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Bifunctional ZnIILnIII dinuclear complexes combining field induced

SMM behaviour and luminescence: Enhanced NIR lanthanide

emission by 9-anthracene carboxylate bridging ligands.

María A. Palacios,a Silvia Titos-Padilla,a José Ruiz,a Juan Manuel Herrera*,a Simon J. Pope,b

Euan K. Brechin,c and Enrique Colacio*,a

aDepartamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada. Avda.

Fuentenueva s/n, 18071-Granada, Spain.

b Cardiff School of Chemistry, Cardiff University, Cardiff, CF10 3AT, United Kingdom

cEaStCHEM School of Chemistry. The University of Edinburgh, West Mains Road, Edinburgh, EH9

3JJ, UK.

Abstract

Thirteen new dinuclear ZnII-LnIII complexes of general formulae [Zn(μ-L)(μ-

OAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3) and Yb (4)), [Zn(μ-L)(μ-NO3)Er(NO3)2] (5),

[Zn(H2O)(μ-L)Nd(NO3)3]·2CH3OH (6), [Zn(μ-L)(μ-9-An)Ln(NO3)2]·2CH3CN (LnIII = Tb (7),

Dy (8), Er (9), Yb(10)), [Zn(μ-L)(μ-9-An)Yb(9-An)(NO3)3]·3CH3CN (11), [Zn(μ-L)(μ-9-

An)Nd(9-An)(NO3)3]·2CH3CN·3H2O (12) and [Zn(μ-L)(μ-9-

An)Nd(CH3OH)2(NO3)]ClO4·2CH3OH (13) were prepared from the reaction of the

compartmental ligand N,N’,N’’-trimethyl-N,N’’-bis(2-hydroxy-3-methoxy-5-

methylbenzyl)diethylenetriamine (H2L), with ZnX2·nH2O (X = NO3- or OAc-) salts,

Ln(NO3)3·nH2O and, in some instances, 9-Anthracenecarboxylate anion (9-An). In all these

complexes, the ZnII ions invariably occupy the internal N3O2 site whereas the LnIII ions show

preference for the O4 external site, giving rise to a Zn(-diphenoxo)Ln bridging fragment.

Depending on the ZnII salt and solvent used in the reaction, a third bridge can connect the Zn II

and LnIII metal ions, giving rise to triple-bridged diphenoxoacetate in complexes 1-4,

diphenoxonitrate in complex 5 and diphenoxo(9-anthracenecarboxylate) in complexes 8-13.

DyIII and ErIII complexes 2, 8 and 3, 5 respectively, exhibit field induced single molecule

magnet (SMM) behavior, with Ueff values ranging from 11.7 (3) to 41(2) K. Additionally, the

solid-state photophysical properties of these complexes are presented showing that ligand L2- is

able to sensitize TbIII and DyIII-based luminescence in the visible region through an energy

transfer process (antenna effect). The efficiency of this process is much lower when NIR

emitters such as ErIII, NdIII and YbIII are considered. When the luminophore 9-Anthracene

carboxylate is incorporated into these complexes, the NIR luminescence is enhanced which

probes the efficiency of this bridging ligand to act as antenna group. Complexes 2, 3, 5 and 8

can be considered as dual materials as they combine SMM behavior and luminescent properties

INTRODUCTION

Lanthanide coordination compounds have been the subject of intense research activity,

especially due to their interesting magnetic and photo-physical properties.1, 2 Their magnetic

properties arise from the unpaired electrons in the inner f orbitals, which are very efficiently

shielded by the fully occupied 5s and 5p orbitals and therefore interact very poorly with the

ligand electrons. Because the ligand effects are very weak, most LnIII complexes exhibit large

and unquenched orbital angular momentum and consequently large intrinsic magnetic

anisotropy and large magnetic moments in the ground state. Bearing this in mind, researchers

have focused their attention toward lanthanide (and actinide) containing complexes, which

could eventually behave as single-molecule magnets (SMMs)3 or low temperature molecular

magnetic coolers (MMCs).4 SMMs show slow relaxation of the magnetization and magnetic

hysteresis below the so-called blocking temperature (TB), and have been proposed as potential

nanomagnets for applications in molecular spintronics,5 ultra-high density magnetic

information storage 6 and quantum computing at molecular level.7 The driving force behind the

enormous increase of activity in the field of SMMs is the prospect of integrating them in nano-

sized devices.8 MMCs show an enhanced magneto-caloric effect (MCE), which is based on the

change of magnetic entropy upon application of a magnetic field and can potentially be used

for cooling applications via adiabatic demagnetisation. Both SMMs and MMCs require a large-

spin multiplicity of the ground state (ST), because in the former the energy barrier () that

avoids the reversal of the molecular magnetization depends on S2, whereas in the latter the

magnetic entropy is related to the spin by the expression Sm = Rln(2S+1). However, the local

anisotropy of the heavy LnIII ions play opposing roles in SMMs and MMCs. While highly

anisotropic LnIII ions (especially DyIII) favour SMM behaviour, MMCs require isotropic

magnetic ions with weak exchange interactions generating multiple low-lying excited and field-

accessible states, each of which can contribute to the magnetic entropy of the system, thus

favouring the existence of a large MCE. Therefore, polynuclear (and high magnetic density)

complexes containing the isotropic GdIII ion with weak ferromagnetic interactions between the

metal ions have been shown to be appropriate candidates for MMCs.9

As for photo-physical properties, lanthanides exhibit intense, narrow-line and long-lived (ns

or s) emissions, which cover a spectral range from the near UV to the NIR region. Because f-f

transitions are parity forbidden, the absorption coefficients are normally very low. However,

organic ligands with strongly absorbing chromophores that transfer energy to the lanthanide

can be used to circumvent that drawback (antenna effect).10 For an efficient energy transfer the

excited state of the ligand should be higher in energy than the lowest excited state of the

lanthanide. It should be noted that lanthanide complexes have been applied as luminescent

bioprobes in analyte sensing and tissues and cell imaging, as well as monitoring drug delivery.

In particular, NIR luminescent complexes are of high interest due to their electronic and optical

applications, especially for optical communications, and biological and sensor applications.11

Recently, we have designed a new compartmental ligand (H2L: N,N’,N”-trimethyl-N,N”-

bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylene triamine, see Figure 1) that presents two

different coordination sites: an inner site of the N3O2 type showing preference for transition

metal ions and the outer site (O4) showing preference for hard, oxophilic metal ions such as

lanthanides.12a The N3O2 pentacoordinated inner site forces metal ions with high preference for

octahedral coordination to saturate their coordination sphere with a donor atom, which can

proceed from a bridging ligand connecting the Ln and the transition metal ions. Following this

strategy, a series of MII-LnIII (MII = Mn, Ni and Co ) complexes were prepared with syn-syn

carboxylate or nitrate bridging groups connecting MII and LnIII ions.12 Moreover, the ligand

does not contain active hydrogen atoms that would promote inter-molecular hydrogen bonds

thus allowing the formation of well isolated molecules in crystal lattice, favouring SMM

behaviour. The existence of phenolic groups in this ligand assures the existence of ligand-

centered electronic transitions in the near-UV, which could sensitize and enhance the emissive

properties of LnIII ions.

We,12 and others,13 have experimentally shown that the very weak JM-Ln observed for

3d/4f dinuclear complexes (MII = Cu, Ni and Co) leads to small separations of the low lying

split sublevels and consequently to a smaller energy barrier for the magnetization reversal. In

view of this, a good strategy to enhance the SMM properties of the 3d/4f aggregates would be

that of eliminating the weak MII-LnIII interactions that split the ground sublevels of the LnIII ion

by replacing the paramagnetic MII ions by a diamagnetic ion.12e,13, 14 According to this strategy,

we are now pursuing, in a first step, the synthesis of 3d/4f systems with the H2L ligand, in

which the paramagnetic MII ions have been replaced with diamagnetic ZnII. Moreover, the new

ZnII-LnIII complexes, in a similar manner to their analogous Schiff-base counterparts,15 should

exhibit interesting luminescent properties. Therefore, some of these complexes can behave as

bifunctional materials, combining SMM and luminescent properties. In a second step, we are

trying to improve the efficiency of energy transfer to the excited levels of the lanthanide ions in

these complexes by introducing a good emitting group, such as 9-Anthracene carboxylate (9-

An), connecting ZnII and LnIII ions.

Herein, we report the synthesis and X-ray structures of a series of ZnIILnIII dinuclear

complexes of formula [Zn(-L)(-X)Ln(NO3)2] ( X = none, NO3-, OAc-, and 9-An; LnIII = Dy,

Tb, Er, Nd, Yb). Ac magnetic susceptibility studies reveal some exhibit slow relaxation of the

magnetization. A study of their solid state photo-physical properties has also been undertaken,

especially of those complexes exhibiting emission in the NIR region (LnIII = Er, Nd, Yb), with

an enhanced NIR luminescence for the complexes containing 9-An bridging ligands discussed.

EXPERIMENTAL SECTION

General Procedures: Unless stated otherwise, all reactions were conducted in oven-dried

glassware in aerobic conditions, with the reagents purchased commercially and used without

further purification. The ligand H2L was prepared as previously described.12a

Preparation of complexes

[Zn(-L)(-OAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). A general procedure was

used for the preparation of these complexes: To a solution of H2L (56 mg, 0.125 mmol) in 5

mL of MeOH were subsequently added with continuous stirring 27 mg (0.125 mmol) of

Zn(OAc)2·2H2O and 0.125 mmol of Ln(NO3)3·nH2O. The resulting colourless solution was

filtered and allowed to stand at room temperature. After two days, well formed prismatic

colourless crystals of compounds 1 and 2, pink crystals for 3 and yellow crystals for 4, were

obtained with yields in the range 40-55%, based on Zn.

[Zn(-L)(-NO3)Er(NO3)2] (5) and [Zn(H2O)(-L)Nd(NO3)3]·2CH3OH (6). These compounds

were prepared in a 60 % yield as pink and violet crystals, respectively, following the procedure

for 1-4, except that Zn(NO3)2·6H2O (37 mg, 0.125 mmol) was used instead of Zn(OAc)2·2H2O.

[Zn(-L)(-9-An)Ln(NO3)2]·2CH3CN (LnIII = Tb (7), Dy (8), Er (9), Yb(10); 9-An = 9-

anthracenecarboxylate)

To a solution of H2L (56 mg, 0.125 mmol) in 5 mL de CH3CN were subsequently added

with continuous stirring 37 mg (0.125 mmol) of Zn(NO3)2·6H2O and (0.125 mmol) of

Ln(NO3)3·nH2O. To this solution was added dropwise another solution containing 28 mg of 9-

anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine. The resulting

solution was filtered and the filtrate allowed to stand at room temperature for two days,

whereupon colourless crystals of compounds 7 and 8, and pink for 9, and yellow for 10 were

obtained with yields in the range 40-50% based on Zn.

[Zn(-L)(-9-An)Yb(9-An)(NO3)2]·3CH3CN (11)

To a solution of H2L (56 mg, 0.125 mmol) in 5 mL of MeOH were subsequently added with

continuous stirring 37 mg (0.125 mmol) of Zn(NO3)2·6H2O and 56 mg (0.125 mmol) of

Yb(NO3)3·5H2O. To this solution was added dropwise another methanolic solution containing

28 mg of 9-anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine and

immediately a yellow precipitate was obtained. The precipitate was dissolved in acetonitrile

and the resulting solution filtered to eliminate any insoluble material. The filtrate was kept at

room temperature for a week affording yellow crystals of compound 11 in 32 % yield based on

Zn.

[Zn(-L)(-9-An)Nd(9-An)(NO3)2]·2CH3CN·3H2O (12). To a solution of H2L (56 mg, 0.125

mmol) in 5 mL de CH3CN were subsequently added with continuous stirring 37 mg (0.125

mmol) of Zn(NO3)2·6H2O and 55 mg (0.125 mmol) of Nd(NO3)3·6H2O. To this solution was

added dropwise another solution containing 28 mg of 9-anthracene-carboxylic acid (0.125

mmol) and 0.125 mmol of triethylamine. The resulting solution was filtered and allowed to

stand at room temperature for two days, whereupon violet crystals of 12 were obtained with a

yield of 41 % based on Zn.

[Zn(-L)(-9-An)Nd(CH3OH)2(NO3)](ClO4)·2CH3OH (13)

To a solution of H2L (56 mg, 0.125 mmol) in 5 mL of MeOH were subsequently added with

continuous stirring 46 mg (0.125 mmol) of Zn(ClO4)2·6H2O and 56 mg (0.125 mmol) of

Nd(NO3)3·5H2O. To this solution was added dropwise another methanolic solution containing

28 mg of 9-anthracene-carboxylic acid (0.125 mmol) and 0.125 mmol of triethylamine. The

resulting solution was filtered and allowed to stand at room temperature. After one week, well

formed prismatic violet crystals of 13, were obtained with a yield of 38% based on Zn.

The purity of the complexes was checked by elemental analysis (see Table S1).

Physical measurements

Elemental analyses were carried out at the “Centro de Instrumentación Científica” (University

of Granada) on a Fisons-Carlo Erba analyser model EA 1108. IR spectra on powdered samples

were recorded with a ThermoNicolet IR200FTIR using KBr pellets. Ac susceptibility

measurements under different applied static fields were performed using an oscillating ac field

of 3.5 Oe and ac frequencies ranging from 1 to 1500 Hz with a Quantum Design SQUID

MPMS XL-5 device. UV-Vis spectra were measured on a UV-1800 Shimadzu

spectrophotometer and the photoluminescence spectra on a Varian Cary Eclipse

spectrofluorometer. Lifetime data were obtained on a 75 JobinYvon-Horiba Fluorolog

spectrometer fitted with a JY TBX picoseconds photodetection module. The pulsed source was

a Nano-LED configured for 372 nm output operating at 500 kHz. Luminescence lifetime

profiles were obtained using the JobinYvon-Horiba FluoroHub single photon counting module

80 and the data fits yielded the lifetime values using the provided DAS6 deconvolution

software.

Single-Crystal Structure Determination

Suitable crystals of 1 and 3-13 were mounted on a glass fibre and used for data collection. Data

for 1 were collected with a dual source Oxford Diffraction SuperNova diffractometer equipped

with an Atlas CCD detector and an Oxford Cryosystems low temperature device operating at

100 K and using Mo-K. Semi-empirical (multi-scan) absorption corrections were applied using

Crysalis Pro. Data for for compounds 3-13 were collected with a Bruker AXS APEX CCD area

detector equipped with graphite monochromated Mo K radiation ( = 0.71073 Å) by applying

the -scan method. Lorentz-polarization and empirical absorption corrections were applied. The

structures were solved by direct methods and refined with full-matrix least-squares calculations

on F2 using the program SHELXS97.16 Anisotropic temperature factors were assigned to all

atoms except for the hydrogens, which are riding their parent atoms with an isotropic

temperature factor arbitrarily chosen as 1.2 times that of the respective parent. The highly

disordered perchlorate counteranion could not be modelled, so that a new set of F2 (hkl) values

with the contribution from the ClO4- anion withdrawn was obtained by the SQUEEZE

procedure implemented in PLATON_94.17

Final R(F), wR(F2) and goodness of fit agreement factors, details on the data collection and

analysis can be found in Tables S2. Selected bond lengths and angles are given in Tables S3.

RESULTS AND DISCUSSION

As expected, the reaction of H2L with Zn(OAc)2·2H2O and subsequently with

Ln(NO3)3·nH2O in MeOH and in 1:1:1 molar ratio led to crystals of the compounds [Zn(-L)

(-OAc)Ln(NO3)2] (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). The same reaction but using

Zn(NO3)3·6H2O instead of Zn(OAc)2·2H2O and Ln(NO3)3·6H2O (LnIII = Nd, Er) led to two

different Zn-Ln dinuclear complexes [Zn(-L)(-NO3)Er(NO3)2]·2CH3OH (5) and [Zn(H2O)(-

L)Nd(NO3)3]· 2CH3OH (6). Zn-Ln complexes, bearing an 9-anthracene carboxylate instead of

acetate connecting ZnII and LnIII ions of formula [Zn(-L)(-9-An)Ln(NO3)2]·2CH3CN (LnIII =

Tb (7), Dy (8), Er (9), Yb(10)) could be prepared by reacting an acetonitrile solution containing

H2L, Zn(NO3)3·6H2O and Ln(NO3)3·nH2O in 1:1:1 molar ratio with another acetonitrile

solution containing 9-anthracene carboxylic acid and Et3N in 1:1 molar ratio. Using the same

reaction conditions as for complexes 1-4, YbIII leads to a yellow powder, which after

recrystallization in acetonitrile afforded the compound of formula [Zn(-L)(-9-An)Yb(9-An)

(NO3)2]·3CH3CN (11) having both bridging and chelating bidentate 9-anthracenecarboxylate

ligands, the latter coordinated to the YbIII ion. With NdIII , and using the same reaction

conditions as for complexes 7-10, only violet crystals of the compound [Zn(-L)(-9-An)Nd(9-

An)(NO3)2]·2CH3CN·3H2O (12), whose structure is very similar to 11, were obtained.

However, using methanol as solvent and Zn(ClO4)·6H2O instead of Zn(NO3)2·6H2O, violet

crystals of the complex [Zn(-L)(-9-An)Nd(CH3OH)2(NO3)](ClO4)·2CH3OH (13) were

obtained (see Figure 1).

Crystal Structures

A perspective view of the structures of complexes 1-13 are given in Figure 1, whereas

selected bond lengths and angles are given in Table S3.

Complex 1 is isostructural to those previously reported by us for the Ni-Ln and Co-Ln

analogues and crystallizes in the triclinic P-1 space group.12a-c The structure of 1 consists of two

almost identical dinuclear ZnII-TbIII molecules, in which the TbIII and ZnII ions are bridged by

two phenoxo groups of the L2- ligand and one syn-syn acetate anion. Compounds 3 and 4

crystallize in the monoclinic P21/n space group and its structure is very similar to that of 1 but

having only one crystallographically independent ZnII-LnIII molecule. The structure of 2 was

previously reported by us and is isostructural to that of 1. 12a

Figure 1.- Structure of the ligand H2L (center). (i) H2L/Zn(OAc)2·2H2O/ Ln(NO3)3·nH2O,

1:1:1, in MeOH (LnIII = Tb (1), Dy (2), Er (3), Yb(4)). (ii) H2L/Zn(NO3)2·6H2O/

Ln(NO3)3·nH2O, 1:1:1, in MeOH (LnIII = Er (5), Nd (6)). (iii) H2L/Zn(NO3)2·6H2O/

Ln(NO3)3·nH2O /9-An/Et3N. 1:1:1:1:1, in CH3CN (LnIII = Tb (7), Dy (8), Er (9), Yb(10)). (iii)

Using the same conditions as in (i) and recrystallization in CH3CN (Yb (11)). The same

conditions as in (iii) (Nd (12)). (v) H2L/Zn(ClO4)2·6H2O/ Nd(NO3)3·6H2O//9-An/Et3N, 1:1:

1:1:1, in MeOH (13)

The structures of complexes 1-4 are given in Figure 1A. In all these complexes, the ZnII

ion exhibits a slightly trigonally distorted octahedral ZnN3O3 coordination polyhedron, where

the three nitrogen atoms from the amine groups, and consequently the three oxygen atoms,

belonging to the acetate and phenoxo bridging groups, occupy fac positions. The Zn-O and Zn-

N distances are found in the ranges 2.037(3)Å to 2.189(2) Å and 2.164(2) Å to 2.262(2) Å,

respectively. In all complexes, the corresponding LnIII ion exhibits a LnO9 coordination

sphere, consisting of the two phenoxo bridging oxygen atoms, the two methoxy oxygen atoms,

one oxygen atom from the acetate bridging group and four oxygen atoms belonging to two

bidentate nitrate anions. The LnO9 coordination sphere is rather asymmetric, exhibiting short

Ln-Ophenoxo and Ln-Oacetate bond distances in the range 2.2 Å -2.3 Å and longer Ln-Onitrate and Ln-

Omethoxy bond distances >2.4 Å (one of the methoxy groups is weakly coordinated with Ln-O

bond distances > 2.6 Å). As expected, the average Ln-Ophenoxo bond distances for compounds 1-

4, steadily decrease from TbIII to ErIII following the lanthanide contraction, with a concomitant

decrease of the average Zn-Ln and Ln-Oacetate bond distances.

The Zn(di--phenoxo)(-acetate)Ln bridging fragment is rather asymmetric, not only

because the Ln-Ophenoxo and Zn-Ophenoxo bond distances are different, but also because there

exists two different Zn-O-Ln bridging angles with average values of 106.28° and 100.5° for

complexes 1-4.

The bridging acetate group forces the structure to be folded with the average hinge

angle of the M(-O2)Ln bridging fragment ranging from 23.39° for 1 to 22.55º for 3 (the hinge

angle, , is the dihedral angle between the O-Zn-O and O-Ln-O planes in the bridging

fragment). Therefore, the hinge angle increases with the decrease of the LnIII size, as expected.

The structure of [Zn(-L)(-NO3)Er(NO3)2]·2CH3OH (5) is isostructural with two Ni-

Ln complexes,12a,b previously reported by us and very similar to that of compounds 1-4 but

having a bridging nitrate anion connecting the ErIII and ZnII metal ions instead of an acetate

anion (see Figure 1B). Compared to complex 3, the most significant effect of the coordination

of the nitrato bridging ligand in 5 is that the Zn(-O2)Er bridging fragment is folded to a lesser

extent. Thus, the hinge angle decreases from 22.6 ° in 3 to a 14.4 ° in 5, with a simultaneous

decrease of Er-O-Zn angles at the bridging region, as well as the out-of-plane displacements of

the O-C bonds belonging to the phenoxo bridging groups from the Zn(O)2Er plane. At variance

with 3, where the acetate and metal ions are almost coplanar, in 5 the plane of the nitrate anion

and the plane containing the ZnII, ErIII and the two oxygen atoms of the nitrato bridging ligands

coordinated to the metal ions, form a dihedral angle of 28.6 °. Zn-O and Er-O bond distances,

involving the oxygen atoms of the nitrate anion in 5, are more than 0.1 Å longer than those

involving the acetate bridging group in 3. The rest of distances and angles in 5 are very close to

that found in 3 and do not deserve any further discussion.

Compound 6 was prepared using the same reaction conditions as for 5, but it does not

contain a nitrate anion connecting the NdIII and ZnII ions. This may be due to the fact that the

large NdIII ion could enforve a significant strain in the weakly bonded nitrate bridging ligand,

so that the di--phenoxo-bridged would be more favourable than the diphenoxonitrate-bridged

one. The structure of 6 is given in Figure 1C and consists of [Zn(H2O)(-L)Nd(NO3)3] neutral

molecules and two methanol molecules of crystallization, both of which are involved in

hydrogen bond interactions. As expected, the absence of a nitrate bridging group in 6 gives rise

to a more planar Zn(-O2)Nd bridging fragment with a hinge angle of 6.6º. Moreover, a water

molecule saturates the octahedral coordination sphere of the ZnII ion and, most importantly, the

coordination of one additional bidentate chelating nitrate ligand to the NdIII ion leads to an

expanded and more symmetrical NdO10 coordination sphere.

Finally, it should be stressed that 6 exhibits both intermolecular and intramolecular

hydrogen bond interactions. The former involve the molecules of methanol, the coordinated

water molecule and one of the nitrate anions belonging to two centrosymmetrically related

ZnII-NdIII molecules with donor-acceptor distances in the range 2.623 Å-2.823 Å. The latter

involve the water molecule and one of the nitrate anions of the same ZnII-NdIII moiety with

O···O distances of 2.920 Å

The structures of complexes 7-10 are shown in Figure 1D and are very similar to that of

complexes 1-4 but having a 9-anthracenecarboxylate bridging ligand instead of an acetate

ligand connecting the ZnII and LnIII ions, and with two acetonitrile molecules of crystallization.

Compared to 1-4, the acetate bridged analogues, compounds 7-10 exhibit a small hinge angle

and smaller and closer Zn-O-Dy bridging angles, resulting in a smaller degree of asymmetry in

the bridging region. One of the Dy-Omethoxy bond distances is significantly shorter than that in

complexes 1-4, leading to a less asymmetry in the DyO9 coordination sphere. The plane of the

anthracene ring is not coplanar with the corresponding plane of carboxylate group, having a

dihedral angle between these planes of ~84°. Bond distances and angles in the rest of the

molecule are very close to those observed in the acetate bridged counterparts.

Compounds 11 and 12 have very similar structures, containing two 9-anthracene

carboxylate bidentate ligands - one acting as a bridge linking the ZnII and LnIII ions and the

other one acting as a chelating ligand coordinated to the LnIII ion (Figure 1E). As with the NiII-

DyIII analogue,12b these compounds crystallize in a non-centrosymmetric space group

(orthorhombic, Pca21) and therefore are examples of chiral molecules obtained from achiral

starting materials. The overall ensemble of crystals in a batch of 11 and 12 are expected to

contain crystals of both enantiomeric forms in equal amounts and therefore to be racemic. As

in compounds 7-10, the anthracene rings are not coplanar with the corresponding plane of

carboxylate group, with dihedral angles between these planes of ~89º and ~82°, for the

bridging and chelating 9-anthracene carboxylate ligands (9-An), respectively, whereas the

dihedral angle between the planes of the anthracene rings for the two 9-An ligands is ~55 º.

The Ln-O bond distances involving the oxygen atoms of the chelating 9-anthracene

carboxylato are shorter than the Ln-Onitrate ones (~ 0.1 Å), the Ln-Omethoxy are the longest and

rather different (~ 0.2 Å) and the two Ln-Ophenoxo distances are ~ 0.1 Å shorter than the Ln-

Ocarboxylate , so that the LnO9 coordination sphere is rather asymmetric.

The structure of 13 is similar to that of compounds 7-10, but one of the nitrate bidentate

ligands coordinated to the LnIII ion is replaced by two molecules of methanol that adopt a cis

configuration. The structure of 13 (see Figure 1F) consists of positive dinuclear units [Zn(-L)

(-9-An)Nd(CH3OH)2(NO3)]+, a perchlorate anion and two methanol molecules of

crystallization. Nd-O distances are in the range 2.30-2.69 Å and therefore the LnO9

coordination sphere is the least asymmetric in this series of ZnII-LnIII complexes. Centro-

symmetrically related molecules are held in pairs by four complementary hydrogen bonds

involving one of the methanol molecules of crystallization, which forms two bifurcated

hydrogen bonds with the non-coordinated oxygen atom of the bidentate nitrate anion and one of

the coordinated methanol molecules of a neighboring unit with O···O distances of 2.977 Å and

2.651 Å, respectively.

SMM behavior

In order to know if our strategy of replacing the 3d paramagnetic ion by Zn II in

diphenoxo-bridged 3d-4f systems improves the SMM properties of this kind of compound, we

have performed dynamic ac magnetic susceptibility measurements as a function of both

temperature and frequency. Under zero-external field, only compound 8 exhibits a weak

frequency dependence of the out-of-phase signal,"M, below 10 K without a net maximum

above 2 K, even at frequencies as high as 1400 Hz (See Figure S1). This behavior indicates

that either the energy barrier for the flipping of the magnetization is not high enough to trap the

magnetization in one of the equivalent configurations above 2 K or there exists quantum

tunneling of the magnetization (QTM), leading to a flipping rate that is too fast to observe the

maximum in the "M above 2 K. The fact that "M for 8 below 4 K does not go to zero but

increase very sharply is a clear indication of the existence of QTM. This fast relaxation process

can be promoted by transverse anisotropy, dipolar and hyperfine interactions. Nevertheless, for

Kramers ions such as DyIII, the first mechanism would not facilitate the QTM relaxation

process. When the ac measurements were performed in the presence of a small external dc

field of 1000 G to fully or partly suppress the quantum tunneling relaxation of the

magnetization, the Dy compounds 2 and 8 and the Er compounds 3 and 5 showed typical SMM

behavior with maxima in the 6.75 K (1488 Hz)-4.25 K (50 Hz), 6.5 K (900 Hz)-4.25 K (50

Hz), 3 K (1400 Hz)-2.5 K (600 Hz), 2.75 K (1400 Hz)-2.2 K (400 Hz) ranges, respectively

(Figures 2 and 3).

Figure 2.- Temperature dependence of in-phase ′M (top) and out-of-phase "M (bottom)

components of the ac susceptibility for complexes 2 (left) and 8 (right) measured under 1000

Oe applied dc field.

The relaxation times, , for compounds 2, 8 and 5 were extracted from the fit of the

frequency dependence of M" at each temperature to the generalized Debye model (Figures S2-

S3). In the case of compound 3, that does not exhibit any maximum in the M" vs frequency

plot (the same fit as for compounds 2, 8 and 5 does not lead to reliable values of ), the

temperatures and frequencies of the maxima in the M" vs T plot were used to extract the

relaxation times. The results were then used in constructing the Arrhenius plot, = 0

exp(/kBT), shown in Figures S2-S3. The fit of the high temperature linear portions of the data

afforded the effective energy barriers for the reversal of the magnetization and o values

indicated in Table 1. The Arrhenius plots, constructed from the temperatures and frequencies

of the maxima observed for the "M signals in Figures 2 and 3 for compounds 2, 5 and 8 lead

virtually to the same and (flipping rate) parameters, as expected. The fact that the out-of-

phase susceptibility for these compounds tends to zero after the maxima is a clear indication

that the QTM is suppressed. Only for compound 3 is the suppression of the QTM incomplete,

which may be due to the existence of significant intermolecular interactions. In some cases, the

effects of these interactions, that favour the fast QTM process, cannot be eliminated by

application of a small magnetic dc field.

The Cole-Cole diagrams for these complexes are shown in Figure S4. The Cole-Cole

plots for complexes 2, 5 and 8 are rather symmetrical and in the high temperature regions

corresponding to the linear portion of the data in the Arrhenius plots they exhibit semicircular

shapes with values in the ranges 0.02 (8 K)-0.10 (5 K), 0.1(3 K)-0.15 (2.2 K), 0.06 (6.75 K)-

0.19 (5 K) for 2, 5 and 8, respectively. These low values indicate very narrow distribution of

slow relaxation in these regions, which would be compatible with the existence of only one

relaxation process. In the case of 3 the Cole-Cole diagram is non-symmetrical with values

are in the range 0.06 (3 K)-0.29 (2.4 K), thus indicating that the crossover from the thermally

activated relaxation process to a quantum regime occurs below ~2.6 K.

Table 1. andvalues for compounds 2, 3, 5 and 8.

Compound ”M signal at H = 0 Oe at H = 1000 Oe0 (s)

2 yes 41(2) 5.6·10-7

3 no 11.7(3) 2.0·10-6

5 no 22(2) 5.3·10-8

8 no 32.1(3) 1.9·10-6

The values of /kB found for 2 and 8 are near the center of the range experimentally

observed for for mono and polynuclear Dy SMMs.1e It should be noted that the

maximum value of found for MII-DyIII ( MII = Ni and Co) compounds isostructural to

2 and 8 was 19.2 K.12a-c Therefore, these results support the conclusion that replacement

of the paramagnetic MII metal ion by ZnII can be an appropriate strategy to improve the

SMM properties in diphenoxo-bridged 3d-4f systems. Complexes 2 and 8 exhibit very

similar LnO9 coordination spheres with a poorly defined geometry as they are

intermediate between several nine-vertex polyhedra (see ESI). Previous ab initio

calculations on a Dy fragment of a Co-Dy compound isostructural to 2 clearly showed

that the ground Kramers doublet arising from the ligand-field splitting of the 6H15/2

ground atomic term shows strong axial anisotropy with gz =18.9 (gx = 0.06 and gy =

0.09) along the main anisotropy axis, which lies close to the Dy–Co direction.12c The

large axial anisotropy of the DyIII ion in compounds 2 and 8 must therefore be at the

origin of their SMM behavior. Notice that axial ligand fields induce strong easy axis

anisotropy of DyIII because it has an oblate electron density.1a This ligand field

anisotropy is easy to achieve accidentally and this is the reason why a wide variety of

DyIII-containing SMMs have been reported. In this regard, the ligand field created by the

nine oxygen atom of the LnO9 coordination sphere is not axial, however 2 and 8 still

present strong axial anisotropy and SMM behavior.

It should be noted that ErIII based SMMs are rare and, as far as we know, only

three such examples have been reported. One of them, Na9[Er(W5O18)2]·xH2O18 (the ErIII

ion is encapsulated between two diamagnetic polyoxometalate cages) exhibits SMM

behavior at zero field with a thermal energy barrier of 55.3 K. The other two are Zn3Er

complexes of very similar hexaimine planar macrocyclic ligands with six oxygen atoms

bridging the ZnII and ErIII ions.19 The former displays a flattened D4d antiprismatic LnO8

coordination sphere leading to a MJ = ± 13/2 ground state that is separated from the first

excited state by ~30 cm-1, whereas the other two have LnO919a and suspected LnO10

19b

coordination spheres that conserve a strong equatorial ligand field. Er III has prolate

electron density1a and, to generate single-ion anisotropy and SMM behavior, an

equatorial ligand field is, in principle, required. The two Zn3ErIII complexes are

examples of systems having this kind of ligand field, whereas the Er-POM system

exhibits a ligand field that can be considered as intermediate between axial and

equatorial. For complexes 3 and 5, with LnO9 coordination spheres very similar to that

of 2 and 8, the absence of a clear axial field can allow an easy-axis anisotropy leading to

the observed SMM behavior.

Figure 3.- Temperature dependence of in-phase ′M (top) and out-of-phase "M (bottom)

components of the ac susceptibility for complexes 3 (left) and 5 (right) measured under 1000

Oe applied dc field.

Photophysical properties.

In the last few years, several examples of lanthanide complexes coordinated by

compartmental Salen-type Schiff-base ligands have been reported to exhibit interesting

photophysical properties. These ligands act as antenna groups, sensitizing LnIII-based

luminescence through an intramolecular energy transfer process.15 Considering the

similarity between ligand H2L and those Salen-derivates, the photophysical properties of

samples 1 – 6 have been studied to determine the ability of ligand L2- to act as sensitizer.

The photophysical properties of complexes 7 – 13, which additionally contain 9-

anthracene carboxylate ligands in their structure, have also been analyzed. The

reflectance spectrum of ligand H2L (Figure S5) shows intense absorption bands in the

UV region located at 240 and 290 nm, which are typical of intraligand π-π* electronic

transitions in the aromatic groups. Excitation at 290 nm resulted in the appearance of a

weak ligand-centered emission (Fig. S5, inset) with a maximum located at λem = 391 nm

and a shoulder located at higher energy (λem = 365 nm).

The 9-Anthracene carboxylate ligand is a well-known luminophore and

anthracene derivates have been previously used as antenna groups to sensitize Ln III-

based luminescence in the NIR region.20 This ligand shows characteristic π-π*

absorption bands that extend well into the visible region and displays an intense and

broad emission band centered at c.a. 500 nm.

In all cases, we examined the emissive properties of the complexes as

microcrystalline powders, their poor solubility preventingdetailed study of their

photophysical properties in solution.

Firstly, we examined the emissive properties of complexes 1 and 2 where the

respective TbIII and DyIII ions are potential emitters in the visible region which can be

sensitized by an energy transfer from the L2- ligand. In both cases, excitation into the

UV π-π* absorption band of ligand L2- at 290 nm resulted in the appearance of the

characteristic TbIII (5D4→7FJ; J = 3, 4, 5, 6) and DyIII (4F9/2→6HJ/2; J = 15/2, 13/2)

emission bands in the visible region respectively (Figure 4). This sensitized LnIII-based

emission can only occur through a L→Ln photoinduced energy transfer process, which

probes the ability of ligand L2- to act as an antenna group. However, a significant

residual ligand-centered emission is still observed which indicates that the energy

transfer process is not complete.

(a) (b)Figure 4. (a) Sensitized emission spectra of complexes 1 (green) and 2 (blue) in the

solid state at room temperature. (b) Jablonski’s diagram of complexes 1 and 2;

approximate energy values of S1 and T1 were determined from the UV-Vis absorption

and emission spectra of ligand H2L.

Similarly, the photophysical properties of samples 7 and 8 were studied. Both

complexes contain the bridging ligand 9-anthracene carboxylate directly linked to the

lanthanide ions. In these cases, excitation of the complexes into the UV absorption

manifold of the 9-anthracene carboxylate unit (λex. = 355 nm) did not result in sensitized

LnIII emission in the visible region. In both cases, only the characteristic emission of the

anthracene moiety was observed. This is due to the fact that the energy of the emissive

3ππ* state is lower than that of the emissive 5D4 and 4F9/2 excited states of ions TbIII and

DyIII respectively.

Regarding the expected sensitized near-infrared emission characteristic of ions

ErIII (4I13/2→4H15/2; λem = 1530 nm) in 3 and 5, YbIII (2F5/2→2F7/2) in 4 and NdIII [4F3/2→4FJ;

J = 11/2 (λem = 1060 nm), 13/2 (λem = 1340nm)] in 6, only the emission characteristic of

YbIII ions in 4 was observed (Figure S6) when the compound was excited at 290 nm,

which indicates the low efficiency of ligand L2- to act as antenna group for these ions.

This is probably due to the poor spectroscopic overlap existing between the ligand

emission and the f-f excited states of ions ErIII, NdIII and YbIII that could act as energy

acceptors. Nevertheless, time-resolved luminescent experiments performed on these

samples using a Nd:YAG excitation source with λex = 355 nm, allowed us to determine

the emission lifetime characteristic of ions ErIII, NdIII and YbIII in these samples. These

lifetimes, obtained after fitting the luminescent decay curve mono-exponentially, are

collected in Table 2 and their values are within those commonly observed for Nd (III),

ErIII) and YbIII molecular complexes, typically 2 μs for ErIII, 1 μs for NdIII and 10 μs for

YbIII.21

Table 2. Luminescence Lifetimes of the solid samples 3 – 6 and 9-13.a

complex τ(μs) complex τ(μs)3 2.08 9 2.774 10.3 10 6.865 0.47 11 11.826 2.14 12 0.80

13 1.12aMeasured at room temperature using 355 nm excitation.

This demonstrates that ligand L2- sensitizes LnIII-based emission, although the

efficiency of the energy transfer process is rather low. To improve the NIR LnIII-based

emissive properties of this kind of molecule, the organic ligand 9-anthracene

carboxylate was introduced as a bridging ligand in complexes 9 – 13. In addition, for

samples 11 and 12, a second anthracene unit is directly chelated to the lanthanide ion.

As expected, in all these cases, excitation at 355 nm resulted in the appearance of

intense sensitized NIR emission from ions ErIII (9), NdIII (12, 13) and YbIII (10, 11) at

their characteristic wavelengths (Figure 5).

(a) (b)Figure 5. (a) NIR sensitized emission spectra of complexes 9 (green) and 10 (blue) and

12 (red) in the solid state at room temperature. (b) Jablonski diagram for these

complexes; approximate energy values of S1 and T1 were determined from the UV-Vis

absorption and emission spectra of ligand 9-Anthracene carboxylic acid.

These results confirm that the use of 9-Anthracene carboxylate ligands as

bridging and/or chelate ligands directly coordinated to the LnIII ions significantly

improves their NIR luminescent properties.

Conclusions.

We have demonstrated that the compartmental ligand H2L (N, N’, N’’-trimethyl-

N,N’’-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-diethylenetriamine) allows the

preparation of four series of dinuclear ZnII-LnIII complexes, in which the ZnII ion

occupies the internal N3O2 site and the oxophylic LnIII ion occupies the external O4 site,

leading to diphenoxo-bridged species. The sixth position in the ZnII coordination sphere

is occupied by either a water molecule or the oxygen atom belonging to acetate, nitrate

or 9-anthracenecarboxylate bridging groups, leading to doubly-bridged diphenoxo or

triply bridged diphenoxo-acetate, diphenoxo-nitrate and diphenoxo-antracene

carboxylate complexes, respectively. Dynamic ac magnetic susceptibility measurements

as a function of temperature and frequency show that the DyIII complexes 2 and 8 and

the ErIII derivates 3 and 5 exhibit field-induced SMM behavior with effective thermal

energy barriers of 41 K, 32.1 K, 11.7 K and 22 K respectively. These are larger than

those found for isostructural complexes with paramagnetic 3d ions such as Ni II, and

CoII, suggesting that the replacement of paramagnetic ions by diamagnetic ions is one

strategy for increasing Ueff in 3d/4f systems. The increase in Ueff appears to due to the

elimination of the weak magnetic exchange coupling between 3d and 4f ions that leads

to a small energy separation between the ground and first excited state. Moreover, we

believe that, as observed in other systems containing diamagnetic ions, the existence of

a diamagnetic ZnII ion linked to the LnIII ions mitigates the intermolecular interactions

between the LnIII, thus diminishing the QTM process and favoring the observation of

slow relaxation of the magnetization. Complexes 3 and 5 are very rare examples of ErIII-

containing SMMs.

Finally, the photophysical properties of these complexes have been studied and

the ability of the ligand L2- to sensitize TbIII and DyIII-based luminescence in the visible

region has been demonstrated. For complexes 1 and 2, excitation of the ππ* absorption

of the ligand results in concomitant sensitized emission in the visible region from the

TbIII and DyIII units respectively. However, the efficiency of this ligand to sensitize the

characteristic emission from ErIII, NdIII and YbIII ions in the NIR region is rather low due

to the poor spectroscopic overlap existing between the ligand emission and the f-f

excited states of these ligands. NIR emission in this kind of system was enhanced by

introducing 9-Anthracene carboxylate luminophores as bridging and/or chelating

ligands coordinated to the lanthanide ions.

DyIII complexes 2 and 8 and ErIII complexes 3 and 5 combine field-induced

SMM behavior and luminescent properties, and therefore can be considered as examples

of dual magnetic-luminescent materials.

ASSOCIATED CONTENT

Elemental analyses for all the complexes, X-ray crystallographic data for 1, 3-13,

including data collection, refinement and selected bond lengths and angles. Variable-

temperature frequency dependence of the ac out-of-phase χM" signal for complexes 2, 5

and 8, Cole-Cole plots for complexes complexes 2, 3, 5 and 8, reflectance spectrum of

the ligand and photoluminisence spectrum of compound 4. This material is available

free of charge via the Internet at http://pubs.asc.org.

AUTHOR INFORMATION

Corresponding Author

*Email: [email protected]

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENT

Financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN)

(Project CTQ-2011-24478), the Junta de Andalucía (FQM-195, the Project of

excellence P11-FQM-7756), and the University of Granada is acknowledged. S. T.-P.

thanks the Junta de Andalucía for a research grant. EKB thanks the EPSRC for funding.

http://pubs.asc.org/

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Electronic supplementary information

Table S1.- Elemental analyses for complexes 1-13

Compound Formula Mw % Cteor (% Cexp) % Hteor (% Hexp) % Nteor (% Nexp)1 C27 H40 N5 O12 Zn Tb 850.93 38.11 (38.04) 4.74 (4.65) 8.23 (8.30)

2 C27 H40 N5 O12 Zn Dy 854.51 37.95 (37,90) 4.72 (4.67) 8.20 (8.37)

3 C27 H40 N5 O12 Zn Er 859.27 37.74 (37.70) 4.69 (4.61) 8.15 (8.24)

4 C27 H40 N5 O12 Zn Yb 865.05 37.49 (37.55) 4,66 (4.73) 8.10 (8.20)

5 C25 H37 N6 O13 Zn Er 862.24 34.82 (34.90) 4.33 (4.41) 9.75 (9.90)

6 C27 H47 N6 O16 Zn Nd 921.32 35.20 (35.31) 5.14 (5.30) 9.12 (9.01)

7 C44 H52 N7 O12 Zn Tb 1095.22 48.25 (48.40) 4.78 (4.91) 8.95 (9.07)

8 C44 H52 N7 O12 Zn Dy 1098.80 48.10 (48.15) 4.77 (4.83) 8.92 (9.00)

9 C44 H52 N7 O12 Zn Er 1103.56 47.89 (47.80) 4.75 (4.76) 8.88 (8.98)

10 C44 H52 N7 O12 Zn Yb 1109.34 47.64 (47.53) 4.73 (4.75) 8.84 (8.80)

11 C61 H64 N7 O11 Zn Yb 1309.60 55.94 (55.90) 4.93 (5.00) 7.49 (7.44)

12 C59 H67 N6 O14 Zn Nd 1293.83 54.77 (54.86) 5.22 (5.30) 6.50 (6.60)

13 C44 H62 N4 O17 Cl Zn Nd 1164.07 45.40 (45.48) 5.37 (5.45) 4.81 (4.90)

Table S2.- Crystalllographic data for compounds 1-13Compound 1 3 4 5 6 7

FormulaC27H40N5O12ZnTb

C27H40N5O12ZnEr

C27H40N5O12ZnYb

C25H37N6O13ZnEr

C27H47N6O16ZnNd

C44H52N7O12ZnTb

Mr 850.93 859.27 865.05 862.24 921.32 1095.22Crystal system Triclinic Monoclinic Monoclinic Orthorhombic Monoclinic Monoclinic

Space group (no.) P-1 (2) P21/n (14) P21/n (14) P212121 (19) P21/c (14) P21/n (14)

a (Å) 11.45081(14) 11.345(5) 11.3197(7) 10.7276(5) 10.686(5) 13.546(5)

b (Å) 14.77726(18) 14.542(5) 14.5238(9) 15.8243(7) 17.785(5) 23.332(5)

c (Å) 19.3346(2) 20.078(5) 20.1539(12) 17.8958(8) 20.049(5) 14.885(5)

a (°) 92.6221(10) 90.000(5) 90.00 90.00 90.000(5) 90.000(5)

β (°) 98.4836(10) 101.407(5) 101.7910(10) 90.00 102.148(5) 102.616(5)

γ (°) 90.9880(10) 90.000(5) 90.00 90.00 90.000(5) 90.000(5)

V (Å3) 3231.50(7) 3247(2) 3243.5(3) 3037.9(2) 3725(2) 4591(2)

Z 4 4 4 4 4 4

Dc (g cm-3) 1.749 1.758 1.771 1.885 1.639 1.585(MoK) (mm-1) 2.981 3.373 3.673 3.609 2.098 2.119

T (K) 100(2) 100(2) 100(2) 100(2) 100(2) 100(2)Observed reflections 16275 (13145) 5689 (5178) 5711 (5254) 5346 (5086) 6560 (5982) 8069 (7233)

Rint0.0403 0.0323 0.0256 0.0302 0.0351 0.0268

Parameters 844 423 423 422 471 595

GOF 0.979 1.055 1.057 0.823 1.109 1.063

R1a, b

0.0363 (0.0260)

0.0310 (0.0281)

0.0269 (0.0240)

0.0272 (0.0253)

0.0388 (0.0347) 0.0330 (0.0289)

wR2c

0.0566 (0.0549)

0.0700 (0.0683)

0.0576 (0.0557)

0.0627 (0.0609)

0.0880 (0.0849) 0.0710 (0.0688)

Largest difference in peak and hole (e Å-3)

1.354 and -0.875

2.947 and -1.033

1.394 and -0.522

1.318 and -0.422

1.453 and -0.767 1.198 and -0.328

a R1 = ||Fo| - |Fc||/|Fo|.b Values in parentheses for reflections with I > 2(I).cwR2 = {[w(Fo

2 - Fc2)2] / [w(Fo

2)2]}½

Compound 8 9 10 11 12 13

Formula

C44H52N7O12ZnDy

C44H52N7O12ZnEr

C44H52N7O12ZnYb

C61H64N7O11ZnYb

C59H67N6O14ZnNd

C44H62N4O17ClZnNd

Mr1098.80 1103.56 1109.34 1309.60 1293.83 1164.07

Crystal system Monoclinic Monoclinic Monoclinic Orthorhombic Orthorhombic TriclinicSpace group (no.) P21/n (14) P21/n (14) P21/n (14) Pca21 (29) Pca21 (29) P-1 (2)

a (Å) 13.547(5) 13.533(5) 13.542(5) 22.4764(12) 22.664(5) 12.051(5)

b (Å) 23.341(5) 23.340(5) 23.319(5) 12.8315(7) 12.828(5) 12.325(5)

c (Å) 14.882(5) 14.868(5) 14.857(5) 19.7813(10) 19.893(5) 17.328(5)

90.000(5) 90.000(5) 90.000(5) 90.00 90.000(5) 74.587(5)

β (°) 102.621(5) 102.600(5) 102.575(5) 90.00 90.000(5) 86.073(5)

γ (°) 90.000(5) 90.000(5) 90.000(5) 90.00 90.000(5) 83.022(5)

V (Å3) 4592(2) 4583(2) 4579(2) 5705.0(5) 5784(3) 2461.0(16)

Z 4 4 4 4 4 2

Dc (g cm-3) 1.589 1.599 1.609 1.525 1.479 1.437MoKmm

2.206 2.411

2.6232.117

1.373 1.593

T (K) 100(2) 100(2) 100(2) 100(2) 100(2) 100(2)Observed reflections 8081 (7400) 8064 (7374) 8003 (7326) 8019 (7335) 9088 (8234) 8641 (6872)

Rint0.0333 0.0399 0.0300 0.0711 0.0613 0.0559

Parameters 595 595 595 740 749 589

GOF 1.066 1.076 1.040 1.037 1.041 1.001

R1a, b

0.0280 (0.0251)

0.0293 (0.0262)

0.0309 (0.0277)

0.0370 (0.0319)

0.0467 (0.0409) 0.0566 (0.0442)

wR2c

0.0618 (0.0601)

0.0650 (0.0634)

0.0675 (0.0658)

0.0723 (0.0693)

0.0965 (0.0914) 0.0989 (0.0935)

Largest difference in peak and hole (e Å-3)

1.122 and -0.387

1.387 and -0.391

1.422 and -0.561

1.361 and -0.455

1.700 and -0.536 1.238 and -0.451

a R1 = ||Fo| - |Fc||/|Fo|.b Values in parentheses for reflections with I > 2(I).cwR2 = {[w(Fo

2 - Fc2)2] / [w(Fo

2)2]}½

Table S3.- Selected bond lengths and angles for complexes 1-13Compound 1 1 3 4 5 6

Ln(1)-Zn(1)3.4662(3

)3.4570(3

) 3.434(1)3.4137(4

)3.4538(5

) 3.637(1)

Ln(1)-O(2A) 2.460(2) 2.479(2) 2.386(3) 2.369(2) 2.416(3) 2.660(3)

Ln(1)-O(5A) 2.329(2) 2.280(2) 2.298(2) 2.280(2) 2.250(3) 2.338(3)

Ln(1)-O(25A) 2.231(2) 2.240(2) 2.209(2) 2.189(2) 2.195(3) 2.371(2)

Ln(1)-O(27A) 2.675(1) 2.726(2) 2.721(3) 2.777(2) 2.562(3) 2.654(3)

Ln(1)-O(2)bridge 2.313(2) 2.307(2) 2.295(3) 2.268(2) 2.422(3)

Ln(1)-O(1B)nitrate 2.443(3) 2.423(2) 2.412(3 2.537(4)

Ln(1)-O(2B)nitrate 2.433(2) 2.408(2) 2.435(3) 2.554(3)

Ln(1)-O(1C)nitrate 2.492(2) 2.502(2) 2.435(3) 2.408(2) 2.439(3) 2.578(3)

Ln(1)-O(2C)nitrate 2.447(2) 2.483(2) 2.447(3) 2.428(2) 2.449(3) 2.578(3)

Ln(1)-O(1D)nitrate 2.471(2) 2.455(2) 2.577(3)

Ln(1)-O(2D)nitrate 2.494(2) 2.478(2) 2.559(1)

Zn(1)-N(12A) 2.180(2) 2.164(2) 2.256(3) 2.262(2) 2.170(4) 2.164(4)

Zn(1)-N(16A) 2.223(2) 2.240(2) 2.195(4) 2,194(3) 2.182(4) 2.186(4)

Zn(1)-N(20A) 2.226(2) 2.233(2) 2.256(3) 2.250(3) 2.251(4) 2.216(4)

Zn(1)-O(5A) 2.189(2) 2.172(2) 2.184(2) 2.177(2) 2.161(3) 2.117(2)

Zn(1)-O(25A) 2.071(2) 2.063(2) 2.097(2) 2.106(2) 2.045(3) 2.077(3)

Zn(1)-O(1)bridge 2.075(2) 2.057(1) 2.037(3) 2.041(2) 2.156(3)Zn(1)-O(1W) 2.219(3)

Ln(1)-O(5A)-Zn(1)100.16(6

)101.86(6

)100.00(9

) 99.96(9) 103.0(1) 109.4(1)

Ln(1)-O(25A)-Zn(1)107.30(7

)106.87(7

) 105.7(1)105.26(9

) 109.1(1) 109.5(1)

O(5A)-Ln(1)-O(25A) 70.07(6) 69.90(6) 72.02(8) 72.51(8) 70.4(1) 65.87(8)

O(5A)-Ln(1)-O(2)bridge 78.43(6) 78.82(6) 78.88(9) 79.80(8) 75.7(1)O(25A)-Ln(1)-O(2)bridge 80.88(6) 79.93(6) 80.86(9) 81.60(8) 78.9(1)

O(5A)-Zn(1)-O(25A) 75.83(6) 75.32(6) 76.48(9) 76.23(8) 75.0(1) 75.2(1)O(5A)-Zn(1)-O(1)bridge 93.36(6) 91.15(6) 90.35(9) 90.10(9) 87.3(1)O(25A)-Zn(1)-O(1)bridge 93.85(6) 95.28(6) 95.76(9) 95.48(9) 90.6(1)O(5A)-Zn(1)-O(1W) 84.1(1)O(25A)-Zn(1)-O(1W) 85.5(1)

Compound 7 8 9 10 11 12 13

Ln(1)-Zn(1)3.4646(7

)3.4550(7

)3.4346(7

)3.4160(7

)3.4213(8

) 3.529(1)3.556(1

)

Ln(1)-O(2A) 2.465(2) 2.453(2) 2.431(2) 2.416(2) 2.408(4) 2.530(4)2.527(3

)

Ln(1)-O(5A) 2.289(2) 2.277(2) 2.259(2) 2.236(2) 2.254(4) 2.379(4)2.397(2

)

Ln(1)-O(25A) 2.230(2) 2.222(2) 2.201(2) 2.181(2) 2.205(4) 2.318(3)2.298(3

)

Ln(1)-O(27A) 2.606(2) 2.598(2) 2.599(2) 2.610(2) 2.854(4) 2.738(4)2.686(2

)

Ln(1)-O(17D)bridge 2.345(2) 2.340(2) 2.311(2) 2.299(2) 2.274(3) 2.412(4)2.420(3

)

Ln(1)-O(1B)nitrate 2.508(2) 2.482(2) 2.485(2) 2.378(2) 2.456(4) 2.586(4)2.589(4

)

Ln(1)-O(2B)nitrate 2.449(2) 2.443(2) 2.406(2) 2.475(2) 2.403(4) 2.549(4)2.573(3

)

Ln(1)-O(1C)nitratea 2.448(2) 2.438(2) 2.422(2) 2.389(2) 2.382(4) 2.494(4)2.499(4

)

Ln(1)-O(2C)nitrateb 2.498(2) 2.495(2) 2.458(2) 2.443(2) 2.342(4) 2.473(4)2.495(4

)

Zn(1)-N(12A) 2.173(3) 2.175(2) 2.177(2) 2.179(3) 2.186(4) 2.196(4)2.179(3

)

Zn(1)-N16A) 2.222(3) 2.225(2) 2.224(2) 2.226(3) 2.200(5) 2.222(4)2.226(4

)

Zn(1)-N(20A) 2.283(2) 2.284(2) 2.279(2) 2.275(2) 2.244(5) 2.276(4)2.258(4

)

Zn(1)-O(5A) 2.186(2) 2.187(2) 2.179(2) 2.177(2) 2.146(4) 2.183(4)2.185(3

)

Zn(1)-O(25A) 2.057(2) 2.055(2) 2.055(2) 2.056(2) 2.115(4) 2.090(4)2.073(2

)

Zn(1)-O(16D)bridge 2.099(2) 2.099(2) 2.102(2) 2.102(2) 2.074(4) 2.061(4)2.069(3

)

Ln(1)-O(5A)-Zn(1)101.43(8

)101.38(7

)101.40(7

)101.43(8

) 102.1(2) 101.2(1)101.7(1

)

Ln(1)-O(25A)-Zn(1)107.76(9

)107.72(8

)107.59(8

)107.45(9

) 104.7(2) 106.3(2)108.7(1

)

O(5A)-Ln(1)-O(25A) 70.48(7) 70.69(6) 71.08(7) 71.51(7) 71.7(1) 69.7(1)67.99(9

)

O(5A)-Ln(1)-O(17D)bridge 77.76(7) 78.11(6) 78.46(7) 78.96(7) 78.9(1) 76.1(1)77.12(9

)

O(25A)-Ln(1)-O(17D)bridge 79.84(7) 80.05(6) 80.37(7) 80.63(7) 83.0(1) 78.6(1)79.47(9

)

O(5A)-Zn(1)-O(25A) 75.78(8) 75.64(7) 75.45(7) 75.09(8) 75.6(1) 77.8(1) 76.1(1)O(5A)-Zn(1)-O(16D)bridge 91.04(7) 90.97(7) 90.83(7) 90.96(8) 91.8(1) 92.1(1) 90.4(1)O(25A)-Zn(1)-O(16D)bridge 92.48(8) 92.40(7) 92.09(7) 92.01(8) 93.4(1) 93.8(1) 93.4(1)

a 11 y 12, O(16C) anthracene and O(1M )methanolb 11 y 12, O(17C) anthracene O(1M )methanol

Continuous Shape Measures calculation for 2

MFF-9 13 Cs Muffin HH-9 12 C2v Hula-hoop JTDIC-9 11 C3v Tridiminished icosahedron J63 TCTPR-9 10 D3h Spherical tricapped trigonal prism JTCTPR-9 9 D3h Tricapped trigonal prism J51 CSAPR-9 8 C4v Spherical capped square antiprism JCSAPR-9 7 C4v Capped square antiprism J10 CCU-9 6 C4v Spherical-relaxed capped cube JCCU-9 5 C4v Capped cube J8 JTC-9 4 C3v Johnson triangular cupola J3 HBPY-9 3 D7h Heptagonal bipyramid OPY-9 2 C8v Octagonal pyramid EP-9 1 D9h Enneagon

Structure [ML9 ] MFF-9 HH-9 JTDIC-9 TCTPR-9 JTCTPR-9 CSAPR-9 JCSAPR-9 CCU-9 JCCU-9 JTC-9 HBPY-9 OPY-9 EP-9

EC-078 , 2.274, 10.337, 11.809,

2.799, 4.168, 2.365, 3.521, 7.589,

8.958, 15.920, 14.999, 23.362, 36.124



Structure [ML9 ] MFF-9 HH-9 JTDIC-9 TCTPR-9 JTCTPR-9 CSAPR-9 JCSAPR-9 CCU-9 JCCU-9 JTC-9 HBPY-9 OPY-9 EP-9 mp-1133 , 1.668, 9.091, 11.107, 2.761, 4.689, 2.000, 2.947, 8.196, 9.510, 15.240, 16.549, 22.853, 35.937



Structure [ML9 ] MFF-9 HH-9 JTDIC-9 TCTPR-9 JTCTPR-9 CSAPR-9 JCSAPR-9 CCU-9 JCCU-9 JTC-9 HBPY-9 OPY-9 EP-9 EC-277 , 2.342, 8.670, 11.539, 2.664, 3.667, 2.413, 3.606, 7.053, 8.316, 15.663, 15.296, 23.442, 35.508



Structure [ML9 ] MFF-9 HH-9 JTDIC-9 TCTPR-9 JTCTPR-9 CSAPR-9 JCSAPR-9 CCU-9 JCCU-9 JTC-9 HBPY-9 OPY-9 EP-9 EC-287 , 1.607, 11.146, 10.742, 2.368, 4.456, 1.531, 2.568, 7.839, 9.260, 14.957, 17.497, 22.261, 37.099

Figure S1.- Temperature dependence of in-phase ’M (left) and out-of-phase ”M (right)

components of the ac susceptibility for complex 8 measured under zero applied dc field.

Figure S2.- Variable-temperature frequency dependence of the χM" signal for 5 in a

1000 Oe dc field. Solid lines represent the best fit to the Debye model (left top).

Arrhenius plots for 5 (left down) and for 3 (right, down).

Figure S3.- Variable-temperature frequency dependence of the χM" signal for 2 (left top)

and 8 (right top) in a 1000 Oe dc field. Solid lines represent the best fit to the Debye

model. Arrhenius plots for 2 (left down) and for 8 (right down).

Figure S4.- Cole-cole plots for 3 (left top), 5(left down), 2 (right top) and 8 (right down)

Figure S5.- Reflectance spectrum of the ligand.

Figure S6.- NIR sensitized emission spectra of complex 4.

university of edinburgh · web viewbifunctional zniilniii dinuclear complexes combining field...

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