synthesis and structure of rhodium complexes containing extended terpyridyl ligands

Inorganica Chimica Acta 357 (2004) 2827–2832

www.elsevier.com/locate/ica

Synthesis and structure of rhodium complexes containing extendedterpyridyl ligands

Joe Paul, Sharon Spey, Harry Adams, Jim A. Thomas *

Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK

Received 28 November 2003; accepted 20 December 2003

Available online 28 March 2004

Abstract

The reaction of the extended terpyridyl ligands, 40-(4000-pyridyl)-2, 20:60,200-terpyridine (qtpy), and 40-phenyl-2,20:60,200-terpyridine(ptpy) with RhCl3 and [tpyRhCl3] (where tpy¼ 2,20:60,200-terpyridine) has been investigated. This has led to the isolation and

characterisation of four new complexes. All the new complexes have had their molecular structures confirmed via X-ray crystal-

lography studies. It has been shown that, consistent with related systems, changes in the electronic properties of the coordinated

ligand results in modulation of the electrochemical and photophysical properties of the complex to which it is coordinated.

� 2004 Elsevier B.V. All rights reserved.

Keywords: Platinum group metals; Polypyridyl ligands; Rhodium

1. Introduction

Since the groundbreaking synthetic work of Dwyer [1]

more than 50 years ago, polypyridyl complexes of d6

transition metals have attracted a huge amount of atten-

tion. In particular and more recently, a variety of d6

transition metals complexes have been investigated as

DNA binding agents. These systems are attractive for

such studies as they combine rich photophysical proper-

ties with inertness and stability under physiological con-ditions. They also possess well-defined, tunablemolecular

architectures and good solubility in aqueous media [2].

As part of an ongoing project to develop novel DNA

probes [3,4] with new metal and/or ligand architectures,

we are investigating the DNA binding capabilities of d6

transition metals complexes that incorporate extended

2,20:60,200 terpyridines or structurally analogous ligands

[5]. Such ligands present a planar aromatic system pro-jecting away from the metal centre, can display g1, g2,

or g3 coordination modes, and are freely available or

easily synthesised. By varying the ligands and metal

centres used, the properties of this basic architecture

* Corresponding author.Tel.: +44-0-114- 222-9325; fax:+44-0-114-

273-8673.

E-mail address: [email protected] (J.A. Thomas).

0020-1693/$ - see front matter � 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.ica.2003.12.023

may be modulated. For example, it is known that cat-

ionic charge affects the DNA binding affinities of metalcomplexes [6]; with the aim of quantifying these effects

we wish to study the binding characteristics of stuctur-

ally analogous complexes of differing cationic charge. In

previous work, we have reported the synthesis and

characterisation of a series of extended terpyridyl com-

plexes of ReI and RuII metal centres [5]. In this paper,

we report the synthesis and structure of several analo-

gous cations based on RhIII. As in our first report, wehave chosen two extended terpyridines; 2,20:4,400:6,200-quaterpyridine (qtpy), 40-phenyl-2,20:60,200-terpyridine(phentpy) as ligands. Using known methodologies we

have synthesised 4 new complexes – Scheme 1. Such

complexes have virtually identical structures to their

RuII analogues, but possess additional cationic charge.

2. Experimental

2.1. Materials and procedures

The ligands qtpy [7], and phentpy [8], and complex

[Rh(tpy)Cl3] [9] were all synthesised via literature

methods. Unless otherwise stated all reactions were

carried out under an oxygen free nitrogen atmosphere.

mail to: [email protected]

Scheme 1. New rhodium complexes synthesised.

2828 J. Paul et al. / Inorganica Chimica Acta 357 (2004) 2827–2832

2.2. Physical measurements

1H NMR spectra were recorded on a Bruker AM250

machine working in Fourier transform mode. Mass

spectral data was collected on a Micromass Prospec

spectrometer operating in positive ion fast atom bom-

bardment mode (FABþ) with a NOBA matrix. UV/Vis

spectra were recorded on a Unicam UV2 or Varian-Carey bio-3 UV–Visible spectrometer in twin beam

mode. Spectra were recorded in matched quartz cells

(Helmer) and were baseline corrected. Emission spectra

were recorded on a Hitachi F4500 spectrophotometer

operating in luminescence wavelength scan mode. Ele-

mental analysis were obtained using a Perkin–Elmer

2400 analyser working at 975 �C. Cyclic voltammetry

were recorded using an EG&G Versastat potentiostatusing the EG&G 270 Electrochemical Research Soft-

ware or Electrochemistry Powersuite software package.

A three-electrode cell was used with an Agþ/AgCl ref-

erence electrode separated from a Pt disk working

electrode and Pt wire auxiliary electrode. 0.1 M�1 dm�3

tetra-n-butylammonium hexafluorophosphate in aceto-

nitrile, doubly recrystallised from ethyl acetate/diethyl

ether, was used as support electrolyte. A scan rate of 200mV s�1 was employed.

2.3. Syntheses

2.3.1. [[Rh(terpy)(qtpy)][PF6]3] [1][(PF6)3]

qtpy (0.105 g, 0.339 mmol) and [Rh(tpy)Cl3] (0.150 g,

0.339 mmol) were refluxed in ethanol–water (1:1, 50 mL)

for 5 h. The reaction mixture was filtered, and NH4PF6

(0.166 g, 1.017 mmol) was added to the filtrate. The light

brown precipitate thus produced was isolated by filtra-

tion and washed sequentially with 10 mL of water,

ethanol and diethyl ether. The resulting solid was dis-

solved in the minimum volume of acetonitrile and then

reprecipitated by addition of diethyl ether, yielding

[1][(PF6)3] in 71% yield (0.260 g). 1H NMR (d (ppm),

CD3CN): 9.14 (2H, s), 9.02 (2H, m), 8.88 (3H, m), 8.73

(2H, d), 8.62 (2H, d), 8.28 (4H, m), 8.11 (2H, m), 7.70

(2H, d), 7.62 (2H, d), 7.51 (4H, m). Mass spectrum: m=z936.3 [M3þ ) 2[PF6]].

2.3.2. [[Rh(qtpy)2][PF6]3] [2][(PF6)3]

qtpy (0.589 g, 1.899 mmol) and RhCl3 (0.199 g, 0.950

mmol) were refluxed in ethanol–water (1:1, 50 mL) for 5

h. The reaction mixture was filtered, and to the filtrate

was added NH4PF6 (0.464 g, 2.849 mmol). The brown

precipitate thus produced was isolated by filtration and

washed sequentially with 10 mL of water, ethanol anddiethyl ether. The resulting solid was dissolved in the

minimum volume of acetonitrile and then reprecipitated

by addition of diethyl ether, yielding [2] [(PF6)3] in 75%

yield (0.825 g). 1H NMR (d (ppm), CD3CN): 9.15 (4H,

s), 9.03 (4H, d), 8.74 (4H, d), 8.30 (4H, m), 8.11 (4H, d),

7.72 (4H, d) and 7.52 (4H, m). Mass spectrum: m=z1013.7 [M3þ ) 2[PF6]].

2.3.3. [[Rh(terpy)(phentpy)][PF6]3] [3][(PF6)3]

Ag(CF3SO3) (0.261 g, 1.017 mmol) and [Rh(tpy)Cl3]

(0.150 g, 0.339 mmol) were refluxed in ethanol–water

(1:1, 60 mL) for 2 h. The precipitated AgCl was removed

by filtration, phentpy (0.105 g, 0.339 mmol) was added

to the filtrate, and refluxing was continued for 5 h. The

reaction mixture was filtered, and NH4PF6 (0.166 g,

1.017 mmol) was added to the filtrate. The light pinkprecipitate thus produced was isolated by filtration and

washed sequentially with 10 mL of water, ethanol and

diethyl ether. The resulting solid was dissolved in the

J. Paul et al. / Inorganica Chimica Acta 357 (2004) 2827–2832 2829


by addition of diethyl ether, yielding [2] [(PF6)3] in 69%


s), 8.89 (3H, m), 8.75 (2H, d), 8.62 (2H, d), 8.26 (6H, m),

7.76 (5H, m), 7.62 (2H, d) and 7.49 (4H, m). Massspectrum: m=z 935.1 [M3þ ) 2[PF6]].

2.3.4. [[Rh(phentpy)2][PF6]3] [4][(PF6)3]

Phentpy (0.588 g, 1.899 mmol) and RhCl3 (0.199 g,

0.950 mmol) were refluxed in ethanol–water (1:1, 50 mL)

for 5 h. The reaction mixture was filtered, and NH4PF6

(0.464 g, 2.849 mmol) was added to the filtrate. The pink

precipitate thus produced was isolated by filtration andwashed sequentially with 10 mL of water, ethanol and

diethyl ether. The resulting solid was dissolved in the


by addition of diethyl ether, yielding [7][(PF6)3] in 29%


s), 8.74 (4H, d), 8.27 (8H, m), 7.81 (6H, m), 7.71 (4H, d),

and 7.49 (4H, m). Mass spectrum: m=z 866

[M3þ ) [PF6])Hþ] and m=z 721 [Mþ ) 2Hþ].

2.4. Crystallography

Crystals of [1][(PF6)3] � 3MeCN, [2][(PF6)3] � 2EtOH,

[3][(PF6)3] � 3MeCN and [4][(PF6)3] � 2MeCN were ob-

tained from vapour diffusion of diethyl ether into satu-

rated acetonitrile.

Data collected were measured on a Bruker SmartCCD area detector with Oxford Cryosystems low tem-

perature system and complex scattering factors were

taken from the program package SHELXTLSHELXTL [10] as im-

plemented on the Viglen Pentium computer. Hydrogen

Table 1

Crystallographic data for complexes 1–4

1 2

Empirical formula C41H34F18N10P3Rh C56H76F1

Formula weight 1204.60 1671.91

Temperature (K) 150(2) 273(2)

Wavelength (�A) 0.71073 0.71073

Crystal system monoclinic tetragona

Space group P21 /c P421=ca (�A) 22.271(5) 13.041(2)

b (�A) 9.904(2) 13.041(2)

c (�A) 22.849(5) 20.533(5)

a (�) 90 90

b (�) 112.265(4) 90

c (�) 90 90

Volume (�A3) 4664.1(17) 3492.2(12

Z 4 2

Density (Mg/m3) 1.715 1.575

Absorption coefficient (mm�1) 0.586 0.456

F ð000Þ 2408 1674

Crystal size (mm3) 1.152� 10�3 1.588� 10

Reflections collected 28 630 21 468

Final R indices 0.0734 (R1), 0.1893 (wR2) 0.0718 (RR indices (all data) 0.1906 (R1), 0.2590 (wR2) 0.1201 (R

atoms were placed geometrically and refined with a

riding model and with Uiso constrained to be 1.2 times

Ueq of the carrier atom.

A summary of the crystallographic data for the

complexes is given in Table 1.

3. Results and discussions

3.1. Synthesis and characterisation

3.1.1. Synthetic methodology

The syntheses of asymmetric [(tpy)Ru(L)]3þ

(L¼ qtpy, phentpy) complexes, 1 and 3 were readily

effected using relatively mild conditions. It was found

that while good yields of 1 were obtained by the direct

reaction of [Rh(tpy)Cl3] with qtpy, high yields of 3 were

only obtained if [Rh(tpy)Cl3] was first pretreated with

three equivilents of Agþ. The pale coloured complexes

were isolated as hexafluorophosphate salts and required

no signifcant further purification. The symmetric[(L)2Ru]3þ complexes were synthesised by the direct

reaction of RhCl3 with the relevant ligand in similarly

mild conditions. In this case yields were only moderate.

However, the reaction produced analytically pure

products, so other methods were not investigated.

3.1.2. 1H NMR and mass spectra studies

All new complexes were characterised by 1-D 1HNMR, FAB-, ES- and accurate mass spectroscopy.1H

NMR spectra of polypyridyl based complexes are often

quite complex because many of the protons in the aro-

matic region have similar chemical shifts. However, the

3 4

8N8O8P3Rh C42H35F18N9O8P3Rh C46H36F18N8P3Rh

1203.61 1238.65

150(2) 150(2)

0.71073 0.71073

l monoclinic monoclinic

Cc C2=c14.749 14.630(3)

16.104 16.179(4)

21.231 21.640(5)

90 90

105.948 105.104(4)

90 90

) 4849(4) 4945.1(18)

4 4

1.649 1.664

0.563 0.555

2480�2 2.232 � 10�2 3.072� 10�3

14 670 21 742

1), 0.1909 (wR2) 0.0433 (R1), 0.1150 (wR2) 0.0407 (R1) 0.0941 (wR2)

1), 0.2304 (wR2) 0.483 (R1), 0.1196 (wR2) 0.0579 (R1) 0.1019 (wR2)

Table 4

Selected bond lengths and angles for complexes [1][(PF6)3]

Bond lengths (�A) Bond angles (�)

Rh–N(1) 2.035(7) N(1)–Rh–N(2) 80.4(3)

Rh–N(2) 1.960(7) N(1)–Rh–N(3) 160.2(3)

Table 3

Electrochemistry data for the complexes in acetonitrile solution vs an

Ag/AgCl reference electrode

Compound Reductionsa (V)

1 )0.44,b)1.11, )1.65b

2 )0.51,b)1.14, )1.393 )0.56,b)0.97, )1.79b

4 )0.49,b 1.55, )1.67b

aUnless otherwise stated couples are reversible with jIpc=Ipaj ¼ 1 and

Dp < 100 mV.bChemically irreversible couple, therefore only Ep value quoted.


spectrum of 1 possesses minimal amount of overlap. Of

the expected thirteen signals (one triplet, seven doublets,

four doublet of doublets, and one singlet), ten are clearly

seen: doublets occur at 8.73, 8.62, 7.70 and 7.62 ppm;

doublet of doublets occur at 9.02 and 8.11 ppm; and asinglet occurs at 9.14 ppm. While the three signals at

8.88, 8.28 and 7.51 ppm are multiplets, they each clearly

consist of two overlapping resonances. Whilst the sig-

nals of 3 are not so clearly separated, they integrate for

the required 26 protons and are consistent with the

structure of the complex.

From symmetry arguments the 1H NMR spectrum of

2 was expected to show seven signals (one singlet, fourdoublets and two doublet of doublets). Seven separate

signals are indeed observed in the spectrum: one singlet

at 9.15 ppm; four doublets at; 9.03, 8.74, 8.11 and 7.72

ppm; and two multiplets at; 8.30 and 7.52 ppm, with

corresponding intergrals of the correct magnitude.

Again, like 3, the spectrum of phentpy derivative 4 is

more complex than its analogous qtpy structure. How-

ever, it integrates for the required number of protonsand is consistent with the structure of the complex. The

mass spectra of all the complexes were determined using

either FAB or positive ion ES techniques. As typically

observed for such complexes, the spectra show sequen-

tial loss of counter ions.

3.1.3. UV/Visible studies

As might be expected, the four complexes all possesssimilar absorption spectra – Table 2. Intense high energy

bands between 240 and 300 nm are assigned to ligand-

based p ! p� and/or n ! p� transitions, while lower

energy bands between 320 and 400 nm are assigned as

RhðdÞ ! LðpÞ metal-to-ligand charge-transfer (MLCT)

transitions. These values are typical of polypyridyl RhIII

complexes.

3.2. Electrochemical studies

Using cyclic voltammetry the electrochemical prop-

erties of acetonitrile solutions of the new complexes were

studied – Table 3.

While no oxidation processes were observed, all the

complexes displayed a chemically irreversible reductions

at 0.46–0.56 V. By analogy with structurally related

Table 2

Photophysical data for complexes recorded in acetonitrile solution

Compound Absorption [kmax /nm (e/mol�1 dm3 cm�1)]

1 358 (1.8� 104), 344 (1.7� 104), 283

(5.2� 104), 247 (3.9� 104)

2 361 (1.8� 104), 344 (1.6� 104), 282

(8.1� 104), 249 (3.6� 104)

3 356 (2.8� 104), 340 (3.6� 104), 324

(3.2� 104), 291 (5.3� 104) 245 (5.8� 104)

4 358 (2.6� 104), 340 (3.7� 104), 332

(3.5� 104), 295 (5.4� 104) 242 (4.4� 104)

RhIII complexes [11] these processes are assigned to the

two-electron RhIII=I reduction couple.

The complexes also displayed more cathodic reduc-

tions. In several cases, these latter processes were

chemically reversible – Table 3. All of the couples dis-

played lower current amplitudes relative to the two-

electron RhIII=I reduction couple. These observations

are consistent with these couples being single electronligand-based reductions.

3.3. X-ray crystallography studies

Crystallographic quality crystals of the hexafluoro-

phosphate salts of all four complexes could be grown

by vapour diffusion of diethyl ether into acetonitrile

solutions.Relevant bond lengths and angles for [1][(PF6)3] are

shown in Table 4. As expected, both ligands coordinate

in a tridentate g3 mode with the RhIII centre taking up a

distorted octahedral coordination geometry – Fig. 1.

There is significant variation in the three trans-angles

at the RuII site. Two of these angles involve pyridyl

moieties from the same tpy unit and consequently the

trans-angles they describe are distorted away from idealoctahedral geometry (ca. 160�). However, the third

trans-angle, involving pyridyl units on different ligands,

is 178� and thus shows a much smaller deviation from

expected values. The five-member chelate rings that

Rh–N(3) 2.040(6) N(1)–Rh–N(4) 94.8(3)

Rh–N(4) 2.067(6) N(1)–Rh–N(5) 98.0(3)

Rh–N(5) 1.956(6) N(1)–Rh–N(6) 89.9(3)

Rh–N(6) 2.049(6) N(2)–Rh–N(3) 79.8(2)

N(2)–Rh–N(4) 101.3(3)

N(2)–Rh–N(5) 178.0(3)

N(2)–Rh–N(6) 98.7(3)

N(3)–Rh–N(4) 88.5(2)

N(3)–Rh–N(5) 101.8(2)

N(3)–Rh–N(6) 93.7(2)

N(4)–Rh–N(5) 79.8(2)

N(4)–Rh–N(6) 159.9(2)

N(5)–Rh–N(6) 80.2(2)

Fig. 1. Structural representation of the cation in [1][(PF6)3]. Hydrogens

and lone pairs are removed for clarity.



J. Paul et al. / Inorganica Chimica Acta 357 (2004) 2827–2832 2831

result from bidentate coordination mean that bite angles

involving N-donors from the same ligands are smaller

than 90�, for example the N(5)–Rh(1)–N(4) angle is79.8(2)�. Whereas, equivalent angles involving nitrogens

on different ligands are much more obtuse, for example

the angle N(2)–Rh(1)–N(4) is 101.3(3)�.As is typically observed for such systems, the Rh–N

bond lengths show some variation. For both ligands,

coordination of the central pyridyl unit results in the

shortest Rh–N bond length, e.g., Ru–N(5)¼ 1.956(6) �Acompared to Ru–N(4)¼ 2.067(6) �A. This distortion is aconsequence of accomodating tridentate ligand coordi-

nation geometry, which involves two five member che-

late rings. While the three coordinated rings are close to

planar, as might be expected from steric arguments in-

volving ortho-hydrogens, the noncoordinated pyridyl

ring of the qtpy is twisted away from the plane relative

to the attached coordinated pyridyl ring.

Relevant bond lengths and angles for [2][(PF6)3] aresummarised in Table 5 and the structure of the cation is

shown in Fig. 2. Again, the trans-angle, involving pyr-

idyl units on different ligands is the largest at 180�, while

Table 5



Ru–N(1) 1.994(5) N(1)–Rh–N(2) 80.22(14)

Ru–N(1A) 1.994(5) N(1A)–Rh–N(2) 99.78(14)

Ru–N(2) 2.072(6) N(1A)–Rh–N(2A) 80.22(14)

Ru–N(2A) 2.072(6) N(1)–Rh–N(2A) 99.78(14)

Ru–N(2B) 2.072(6) N(2)–Rh–N(2A) 91.65(5)

Ru–N(2C) 2.072(6) N(1A)–Rh–N(2B) 99.78(14)

N(1)–Rh–N(2B) 80.22(14)

N(2A)–Rh–N(2B) 91.65(5)

N(1A)–Rh–N(2C) 80.22(14)

N(1)–Rh–N(2C) 99.78(14)

N(2)–Rh–N(2C) 91.65(5)

N(2B)–Rh–N(2C) 91.65(5)

N(1A)–Rh–N(1) 180.0

N(2)–Rh–N(2B) 160.4(3)

N(2A)–Rh–N(2C) 160.4(3)

the other two trans-angles involving N-donors from the

same ligand are more acute at 160.4(3)�.Again, for the five-member chelate rings involving N-

donors from the same ligands ligand bite angles are less

than 90�, and equivalent angles involving nitrogens on

different ligands are more open. However, the distribu-

tion of bond angles in 2 (80.22(14)–99.78(14)�) is slightlylower than in 1 (79.8(2)–101.3(3)�). This same trend is

observed in bond lengths: for 2 Ru–N bond lengths vary

between 1.994(5) and 2.072(6) �A, whereas for 1 Ru–N

bond lengths vary between 1.956(6) and 2.067(6) �A.These observations indicate that metal coordination

geometry within 2 is closer to idealized octohedral ge-

ometry. Like 1, the noncoordinated pyridyl rings of the

qtpy ligands in 2 display a twist relative to the attached

coordinated pyridyl ring.

Relevant bond lengths and angles for [3][(PF6)3] are

summarised in Table 6 and the structure of the cation is

shown in Fig. 3. The coordination geometry of thiscomplex is very similar to that of 1. Again, coordination

of the central pyridyl unit of tpy and phentpy results in

the two shortest Rh–N bond lengths. However, unlike 1

and 2, these two bonds are different in length. The

phentpy bond is shorter (1.937(7) �A) than equivalent

bond involving tpy (1.988(6) �A) indicating that, because

Table 6



Rh–N(1) 2.044(6) N(1)–Rh–N(2) 79.9(3)

Rh–N(2) 1.937(7) N(1)–Rh–N(3) 159.9(2)

Rh–N(3) 2.058(6) N(1)–Rh–N(4) 90.3(2)

Rh–N(4) 2.056(6) N(1)–Rh–N(5) 98.6(2)

Rh–N(5) 1.988(6) N(1)–Rh–N(6) 92.39(13)

Rh–N(6) 2.056(6) N(2)–Rh–N(3) 80.1(2)

N(2)–Rh–N(4) 102.7(2)

N(2)–Rh–N(5) 176.90(14)

N(2)–Rh–N(6) 96.5(2)

N(3)–Rh–N(4) 92.41(11)

N(3)–Rh–N(5) 101.5(2)

N(3)–Rh–N(6) 91.5(2)

N(4)–Rh–N(5) 80.0(2)

N(4)–Rh–N(6) 160.8(2)

N(5)–Rh–N(6) 80.8(3)



Table 7



Rh–N(1) 1.9651(19) N(1)–Rh–N(1A) 177.42(11)

Rh–N(1A) 1.9651(19) N(1)–Rh–N(2) 101.78(8)

Rh–N(2) 2.046(2) N(1)–Rh–N(2A) 80.04(8)

Rh–N(2A) 2.046(2) N(1)–Rh–N(3) 98.08(8)

Rh–N(3) 2.043(2) N(1)–Rh–N(3A) 80.12(8)

Rh–N(3A) 2.043(2) N(1A)–Rh–N(2) 80.04(8)

N(1A)–Rh–N(2A) 101.78(8)

N(1A)–Rh–N(3) 80.12(8)

N(1A)–Rh–N(3A) 98.08(8)

N(2)–Rh–N(2A) 92.38(12)

N(2)–Rh–N(3) 160.13(8)

N(2)–Rh–N(3A) 90.72(8)

N(2A)–Rh–N(3) 90.72(8)

N(2A)–Rh–N(3A) 160.13(8)

N(3)–Rh–N(3A) 92.99(11)




phentpy contains less nitrogen atoms, it is less electron

deficient than qtpy and thus the pyridyl nitrogen is a

better electron donor.

Relevant bond lengths and angles for [4][(PF6)3] are

summarised in Table 7 and the structure of the cation is

shown in Fig. 4. As expected, and like the analogous

qtpy complex, metal coordination geometry within 4 is

closer to idealized octahedral geometry than 3. Rh–N

bond lengths in 4 are distributed over a lower range

(1.9651(19)–2.046(2) �A) than 3 (1.937(7)–2.058(6) �A).

The chelate ring bite angles also show a slightly less widedistribution.

4. Conclusion

The synthesis of four new extended terpyridyl com-

plexes of RhIII have been synthesised in good yields. In

all cases the structure of the new complexes has beenconfirmed by X-ray crystallography studies. The com-

plexes display distorted octahedral geometries around

the metal ion. To a large extent, variations in coordi-

nation bond lengths and angles between the four com-

plexes can be rationalized by a consideration of the

steric and electronic properties of these systems.

The DNA binding properties of these complexes are

currently being investigated and the results of thesestudies will form the basis of future reports.

Acknowledgements

J.A.T. gratefully acknowledges the support of The

Royal Society.

References

[1] W.W. Brandt, F.P. Dwyer, E.C. Gyarfas, Chem. Rev. 54 (1954)

991.

[2] (a) C. Moucheron, A. Kirsch-De Mesmaeker, J.M. Kelly, J.

Photochem. Photobiol. B: Biol. 40 (1997) 91;

(b) K.E. Erkkila, D.T. Odom, J.K. Barton, Chem. Rev. 99 (1999)

2777;

(c) C. Metcalfe, J.A. Thomas, Chem. Soc. Rev. 32 (2003) 214.

[3] C. Metcalfe, M. Webb, J.A. Thomas, Chem. Commun. (2002)

2026.

[4] C. Metcalfe, H. Adams, I. Haq, J.A. Thomas, Chem. Commun.

(2003) 1152.

[5] C. Metcalfe, S. Spey, H. Adams, J.A. Thomas, J. Chem. Soc.,

Dalton Trans. (2002) 4732.

[6] J.L. Kisko, J.K. Barton, Inorg. Chem. 39 (2000) 4942.

[7] L. Persaud, G. Barbiero, Can. J. Chem. 69 (1991) 315.

[8] E.C. Constable, J. Lewis, M.C. Liptrot, P.R. Raithby, Inorg.

Chim. Acta 178 (1990) 47.

[9] I.I Bhayat, W.R. McWhinnie, Spectrochim. Acta A 28 (1971) 743.

[10] SHELXTLSHELXTL version, An integrated system for solving and refining

crystal structures from diffraction data (Revision 5.1), Bruker

AXS Ltd.

[11] J.-P. Collin, A. Harriman, V. Heitz, F. Odebel, J.-P. Sauvage, J.

Am. Chem. Soc. 116 (1994) 5679.

synthesis and structure of rhodium complexes containing extended terpyridyl ligands

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