construction of three-dimensional metal−organic frameworks with helical character through...

Construction of Three-Dimensional Metal-Organic Frameworkswith Helical Character through Coordinative and SupramolecularInteractions

Jian-Qiao Chen,† Yue-Peng Cai,*,† Hua-Cai Fang,† Zheng-Yuan Zhou,† Xu-Lin Zhan,†

Gang Zhao,‡ and Zhong Zhang†

School of Chemistry and EnVironment, Key Laboratory of Technology on Electrochemical EnergyStorage and Power Generation in Guangdong UniVersities, South China Normal UniVersity,Guangzhou, 510006, China, and Shanghai Institute of Organic Chemistry, Chinese Academy ofScience, Shanghai, 20032, P. R. China

ReceiVed December 7, 2008; ReVised Manuscript ReceiVed January 23, 2009

ABSTRACT: Self-assemblies of the semirigid dipolar ligand 1,4-bis(benzimidazol-1-ylmethyl)benzene (L) with zinc and cobaltsalts have led to six new complexes, namely, {[M(L)(DMF)2(H2O)2] ·2(NO3)}n [M ) Zn (1) and Co (2)], {[M(L)2Cl2] ·DMF ·S}n

[M ) Zn(3), S ) C2H5OH; Co(4), S ) CH3OH + H2O], [Zn(L)2] · (ClO4)2 ·4DMF ·3H2O]n (5), and {[Co(L)2(DMF)2](ClO4)2}n (6),respectively. Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elementalanalyses, IR spectra, and thermogravimetric analyses. Compounds 1 and 2 are isomorphous and present one-dimensional chain-likestructures. It is interesting that three-dimensional (3D) organic-inorganic hybrid frameworks containing meso-helical chains (P +M) have been observed in the solid-state of 1 and 2, in which meso-helical chains are alternately trapped by the cooperative associationof coordination interactions as well as hydrogen bonds. With the replacement of ZnII/CoII nitrate salts with ZnCl2 or CoCl2 in theabove reactions, the resulting complexes 3 and 4 contain P-helical and M-helical chains with 21 screw axis but crystallize as aracemate. Through π · · ·π stacking interactions between two well-overlapping benzimidazoleyl rings from two adjacent chains, the3D racemic supramolecular network is further assembled. However, reaction of M(ClO4)2 (M ) Zn(5), Co(6)) and L yields twohigh dimensional compounds 5 and 6 with helical character, in which compound 5 has a two-dimensional (2D) (4,4) wave-like layerconstructed by vertical crossing of the left-(M) and right-(P)-handed helical chains with the central ZnII ions as the hinge nodes, andsimilarly, the final 3D supramolecular structure is assembled via weak π · · ·π interactions between two central benzene rings fromtwo adjacent ligands L of two neighboring 2D layers. Compound 6 presents a four-connected 3-fold interpenetrated 3D diamondoidnetwork containing meso-helical chains along two mutually perpendicular directions, respectively. Furthermore, the photoluminescentproperties of compounds 1, 3, and 5 were studied.

Introduction

Research on the design and synthesis of metal-organicframeworks (MOFs) in recent years has become an active areain the field of crystal engineering and supramolecular chemistry,not only because of their tremendous potential applications ingas storage, chemical separations, ion exchange, microelectron-ics, nonlinear optics, and heterogeneous catalysis, but alsobecause of their intriguing variety of architectures and topolo-gies.1 The synthesis of such species is often based on the self-assembly of suitable building blocks to give supramolecularnetworks constructed by coordination or/and hydrogen bondsor other weaker supromolecular interactions, such as π · · ·πstacking interactions. Although concepts of crystal engineeringand supromolecular chemistry are usefully employed in theattempt to construct networks of desired topologies and proper-ties, many subtle factors, for example, the selection of the metalions with different coordination geometry or radius, counter-anions with different coordination abilities, or bulk, solvent,metal/ligand ratio, and even pH conditions still contribute tomake this objective a major challenge. For these influencingfactors, the variation of counteranion nature and differentconformations of the semirigid ligand, in particular, play a veryimportant role in the self-assembly processes of metal-complexeswith different structural topologies.2

On the other hand, helices are of intense interest becauseliving organisms utilize them to store and transmit geneticinformation. More importantly, these helical compounds havecharacteristic features and broad applications in the fields ofchiral synthesis, optical devices, sensory functions, etc.3,4

Consequently, many single-, double-, and multihelical com-plexes have been generated by self-assembly processes ofcoordination or supramolecular interactions.5,6 Compared withthe aforementioned cases, metal-containing helical chain struc-tures, especially meso-helical chains, trapped in three-dimen-sional (3D) MOFs by coordinative interactions or cooperativeassociation of coordination interactions and hydrogen bonds,are much less common.7 Meanwhile, the influence of thecounteranion nature on the self-assembly processes of MOFswith helical character is still less well understood, and systematicinvestigations are also rare.

Recently, our investigations show that two flexible C3-symmetric tripodal ligands such as tris(1-benzimidazolylethy-l)amine and tris[(2-salicylaldeneimino)ethyl]amine can encap-sulate one, two, or three metal ions with the two tripodal ligandsexhibiting “double”-propeller-like helical topologies of themesocate or racemate (with each tripodal ligand exhibiting anindependent propeller sense).8 Moreover, one flexible dipolarligand O,O′-bis(8-quinolyl)-1,8-dioxaoctane with two terminaloxaquinolyl rings gives a single-stranded double-helical meso-meric structure.9 As part of our recent efforts to explore thecombination of established ideas in transition metal coordinationchemistry and in supramolecular interactions (mainly hydrogenbonding and π · · ·π) as a strategy for crystal engineering, herein

* To whom corresponding should be addressed. Phone: +86-20-33033475.Fax: +86-20-85215865. E-mail: [email protected].

† South China Normal University.‡ Shanghai Institute of Organic Chemistry, Chinese Academy of Science.

CRYSTALGROWTH& DESIGN

2009VOL. 9, NO. 3

1605–1613

10.1021/cg8013317 CCC: $40.75 2009 American Chemical SocietyPublished on Web 02/16/2009

we report six synthesized and structurally characterized differentdimensional metal-organic coordination polymers, namely, one-dimensional (1D) chain-like {[M(L)(DMF)2(H2O)2] ·2(NO3)}n

[M ) Zn(1), Co(2))] and {[M(L)2Cl2] ·DMF ·S}n [M ) Zn(3),S ) C2H5OH; M ) Co(4), S ) CH3OH + H2O], two-dimensional (2D) layer [Zn(L)2] · (ClO4)2 ·4DMF ·3H2O]n (5),as well as 3-fold interpenetrated 3D diamondoid network{[Co(L)2(DMF)2](ClO4)2}n (6), assembled from a dipolar ligandL and M(NO3)n, MCl2 as well as M(ClO4)2 [M ) Zn(1, 3, 5),Co(2, 4, 6), L ) 1,4-bis(benzimidazol-1-ylmethyl)benzene],respectively. Moreover, a brief comparison of 1D structures 1-4with 2D/3D structures 5-6 is made in an effort to elucidatetheir crystal engineering implications. Our study shows that thechange of anions can influence the subtle variables that lead tocoordination polymers with different structures (Scheme 1).

Experimental Section

Physical Measurements. All materials were reagent grade obtainedfrom commercial sources and used without further purification; solventswere dried by standard procedures. Ligand 1,4-bis(benzimidazol-1-ylmethyl)-benzene (L) was prepared according to the reported proce-dures.10 Elemental analyses for C, H, N were performed on a Perkin-Elmer 240C analytical instrument. IR spectra were recorded on a NicoletFT-IR-170SX spectrophotometer in KBr pellets. The luminescentspectra for the solid state were recorded at room temperature on HitachiF-2500 and Edinburgh-FLS-920 with a xenon arc lamp as the lightsource. In the measurements of emission and excitation spectra the passwidth is 5.0 nm. Thermal analyses (under oxygenated atmosphere,heating rate of 5 °C/min) were carried out in a Labsys NETZSCH TG209 Setaram apparatus.

Synthesis of Complexes 1-6. All complexes were prepared by asimilar procedure. MX2 (0.5 mmol, X ) NO3

-, M ) Zn (1), Co(2);Cl-, M ) Zn(3), Co(4); ClO4

-, M ) Zn(5), Co(6)) dissolved in ethanol/methanol and N,N-dimethylformamide (DMF) (10 cm3, ratio in volume2:1) was added to a ethanol solution (10 cm3) containing L (0.18 g,0.5 mmol) dropwise at room temperature and the mixture was reactedwith stirring for 0.5 h. The insoluble components were removed byfiltration, and the filtrate was allowed to stand at room temperature.The pale yellow (for Zn salts) and red (for Co salts) crystals,respectively, were collected after slow evaporation at room temperaturefor about 2 weeks.

{[Zn(L)(DMF)2(H2O)2] ·2(NO3)}n (1). Yield 45%. Elemental analy-sis calcd (%) for C28H36N8O10Zn: C, 47.32; H, 5.07; N, 15.77. Found:C, 47.25; H, 5.36; N, 15.41. FT-IR (KBr, cm-1): 3436-3284 (br, s),3110 (m), 1652 (vs), 1509 (s), 1485 (m), 1465 (m), 1384 (vs), 1335(m), 1295 (m), 1264 (m), 1112 (m), 1017 (m), 914 (w), 802 (m), 767(m), 740 (m), 690 (m), 615 (w), 506 (w).

{[Co(L)(DMF)2(H2O)2] ·2(NO3)}n (2). Yield 50%. Elemental analy-sis calcd (%) for C28H36N8O10Co: C, 47.76; H, 5.12; N, 15.92. Found:C, 47.38; H, 5.39; N, 15.88. FT-IR (KBr, cm-1): 3358-3235 (br, s),3093 (m), 2938 (m), 1656 (vs), 1513 (s), 1487 (m), 1460 (m), 1386(s), 1330 (m), 1293 (m), 1269 (w), 1110 (s), 1015 (m), 911 (w), 796(m), 768 (m), 743 (m), 693 (m), 511 (w).

{[Zn(L)2Cl2] ·DMF ·C2H5OH}n (3). Yield 67%. Elemental analysiscalcd (%) for C27H31C12N5O2Zn: C 54.56, H 5.22, N 11.79. Found: C54.51, H 5.29, N 11.87. FT-IR (KBr, cm-1): 3171(m), 2927(w), 1665(s),1616(m), 1596(w), 1517(s), 1485(m), 1464(s), 1389(s), 1296(m),1265(s), 1095(s), 917(m), 746(s), 647(m), 623(s), 464(w).

{[Co(L)2(DMF)2] ·H2O ·CH3OH}n (4). Yield 58%. Elemental analy-sis calcd (%) for C26H31C12N5O3Co: C 52.85, H 5.44, N 13.05. Found:C 52.15, H 5.49, N 12.9. FT-IR (KBr, cm-1): 3413(br, m), 3117(s),2935(w), 1657(s), 1607(m), 1588(w), 1510(s), 1492(m), 1383(s),1291(w), 1263(s), 1091(s), 923(m), 741(s), 631(m), 475(w).

[Zn(L)2] · (ClO4)2 ·4DMF ·3H2O]n (5). Yield 66%. Elemental analy-sis calcd (%) for C56H70C12N12O15Zn: C 52.19, H 5.44, N 13.05. Found:C 52.15, H 5.49, N 12.97. FT-IR (KBr, cm-1): 3424(broad, m),3106(m), 2931(w), 1663(s), 1625(m), 1569(m), 1547(s), 1522(s),1488(m), 1464(s), 1429(s), 1288(m), 1101(s), 1095(broad, s), 925(m),638(w), 624(s).

{[Co(L)2(DMF)2](ClO4)2}n (6). Yield 52%. Elemental analysis calcd(%) for C50H50C12N10O10Co: C 55.51, H 4.63, N 12.95. Found: C 55.35,H 4.69, N 12.97. FT-IR (KBr, cm-1): 2968(w), 1661(s), 1633(m),1576(s), 1526(s), 1476(m), 1462(s), 1425(s), 1273(m), 1105(s), 1090(s),913(m), 732(w), 637(s), 482(w).

X-ray Data Collection and Structure Refinement. Data collectionswere performed at 298 K on a Bruker Smart Apex II diffractometerwith graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) for1-6. Absorption corrections were applied by using the multiscanprogram SADABS.11 Structural solutions and full-matrix least-squaresrefinements based on F2 were performed with the SHELXS-9712 andSHELXL-9713 program packages, respectively. All the non-hydrogenatoms were refined anisotropically except O2, C26, C27 atoms in 3and C26 atom in 4. The hydrogen atoms were placed at calculatedpositions and included in the refinement in the riding model approxima-tion. The organic hydrogen atoms except solvent ethanol molecule in3 and methanol molecule in 4 were generated geometrically (C-H )0.93 or 0.96 Å); the water hydrogen atoms were located from differencemaps and refined with isotropic temperature factors. The C27 and O2atoms of solvent ethanol molecule in 3, O2 atom of solvent methanolmolecule in 4, three oxygen (O5, O6, O7) atoms of one perchlorate in5 and C12 atom of DMF in 6 are disordered into two positions, andeach position has a site occupancy factor of 0.5. In addition, thehydrogen atoms of methanol and ethanol molecules in 3-4 are notadded, and the partial hydrogen atoms of the coordinated DMFmolecules in 6 are also added. Details of the crystal parameters, datacollections, and refinement for complexes 1-6 are summarized in Table1. Selected bond lengths and angles for complexes 1-6 are shown inTable S2, Supporting Information. Hydrogen-bonding data of complexes1-6 are listed in Table S2. Further details are provided in SupportingInformation. CCDC 694419, 694420, 702171, 702757, 655962, and704966 are for 1-6, respectively.

Results and Discussion

Synthesis and General Characterization of Compounds1-6. The ligand 1,4-bis(benzimidazol-1-ylmethyl)benzene fea-tures mainly in its exobidentate coordination mode with thebenzene ring as the base and two free-rotating benzimidazolerings as anchors situated at para-positions of the spacerphenylene. It can be easily prepared, according to a proceduresimilar to that reported earlier,10 by the replacement reactionof 1,4-bis(bromomethyl)benzene with benzimidazole. It thenreacts with ZnII/CoII salts such as ZnCl2/CoCl2, Zn(ClO4)2 ·6H2O/Co(ClO4)2 ·6H2O, Zn(NO3)2 ·6H2O/Co(NO3)2 ·6H2O, andZnAc2 ·2H2O with a 1:1 ratio of L to Zn2+/Co2+ at roomtemperature under almost the same conditions except the counter-anions. Fortunately, three former reactions of each salt crystallizegood quality single crystals, and X-ray single crystal diffractionindicates that their components accord with {[M(L)-(DMF)2(H2O)2] ·2(NO3)}n [M ) Zn(1) and Co(2)] and {[Zn(L)2-Cl2] ·DMF ·C2H5OH}n (3), [Co(L)2Cl2] ·DMF ·CH3OH ·H2O]n (4),[Zn(L)2] · (ClO4)2 ·4DMF ·3H2O]n (5), and [Co(L)2(DMF)2] (ClO4)2

(6), respectively, which are further confirmed by elemental analyses.Theoretically, semirigidity of this ligand makes it rotate freely insolution around the -CH2- carbon atom position and has a potentialtendency to generate three typical conformations when coordinatingto the metal centers (Scheme 2). In the present case, though freeligand L is in trans-form in the solid state (Figure S1, Supporting

Scheme 1. Assembly of Compounds 1-6 Tuned by theCounteranions

1606 Crystal Growth & Design, Vol. 9, No. 3, 2009 Chen et al.

Information), its semirigidity affords the appropriate conforma-tion for the formation of every compound.

The IR spectra of complexes 1-6 show that the mediumabsorption νC)N in ligand L appearing at 1505 cm-1 shifts to ahigher wavenumber and becomes a strong peak at 1509 cm-1

for 1, 1513 cm-1 for 2, 1517 cm-1 for 3, 1510 cm-1 for 4, 1522cm-1 for 5, and 1526 cm-1 for 6. The blue shifts indicate thatthe imino nitrogen atoms of the ligand are coordinated to themetal (II) ions.14 Furthermore, the very wide bands at 3439-3227cm-1 in the compounds 1, 2, and 4 are the results of hydrogenbondings O-H · · ·O. Very strong peaks at 1652-1666 cm-1 incomplexes 1-6 show the existence of solvent DMF molecules.These facts are in agreement with the results of compounds 1-6determined by X-ray single crystal diffraction.

Compounds 1 and 2 are isomorphous and structures of 3 and4 are similar; thus compounds 2, 3, 5, and 6 were selected forthe thermogravimetric analysis (TGA) to examine the thermalstability of the compounds (Figure S2, Supporting Information).TGA curve under nitrogen shows that the solid-state structureof 2 is highly robust. For 2, the coordinated water and N,N-

dimethylformamide (DMF) molecules were lost at the ap-proximate temperature from 105 to 282 °C (calcd 25.87%, found26.02%). A complicated decomposition reaction then took placewhen the heating continued. In compound 3, it can be seen fromits TG curve that one ethanol and one DMF molecule were lostat the approximate temperature from 87 to 155 °C (calcd.18.11%, found 17.82%). And then a complicated decompositionreaction took place when the heating continued. Preliminarythermogravimetric (TG) analysis of 5 and 6 shows a weightloss below 167 °C (calcd. 26.87%, found 26.12% for the waterand DMF molecules) in 5 and 271 °C (calcd. 13.50%, found13.65% for the DMF molecules) in 6, and coordinationframework decomposition until a temperature up to 345 °C for5 and 412 °C for 6. Compared with 3 and 5, DMF moleculesin 2 and 6 have a higher loss temperature, deriving from thecoordination to metal ion.

Description of Crystal Structures of Complexes 1 and2. X-ray single crystal diffraction reveals two complexes 1 and2 are isomorphous. The repeat unit consists of one[M(L)(DMF)2(H2O)2]2+ cation and two nitrate anions. The MII

ion locates on a symmetry center and is coordinated by fouroxygen atoms from two aqua ligands and two DMF moleculesarranged trans to each other on the equatorial plane and twonitrogen atoms from the benzimidazolyl groups of two differentL ligands occupying the apical coordination sites to furnish anoctahedral geometry (Figure 1). These bond lengths (Table S2,Supporting Information) are comparable to previously reported

Figure 1. (a) Molecular structure of 1 or 2 showing the localcoordination geometry of M2+ ion [M ) Zn2+(1) and Co2+(2)] withthe atom labels. Symmetry code a: 1 - x, 1 - y, -z; b: 1 - x, 1 - y,1 - z; c: x, y, -1 + z; d: x, y, 1 + z. (b) trans,trans-configuration ofligand L in compounds 1 and 2.

Table 1. Crystal Data and Structure Refinement of 1-6

1 2 3 4 5 6

chemical formula C28H36N8O10Zn C28H36N8O10Co C27H31Cl2N4O2Zn C26H31Cl2N5O3Co C56H70Cl2N12O15Zn C200H200Cl8N40O40Co4

M 710.02 703.58 593.82 591.39 1287.51 4323.32crystal system monoclinic monoclinic monoclinic monoclinic monoclinic orthorhombicspace group P21/n P21/n P21/n P21/n Pn Fddda /Å 13.0189(2) 13.0172(2) 14.2056(9) 14.2359(17) 11.6722(4) 13.5179(9)b /Å 8.74500(10) 8.82010(11) 12.3352(8) 12.5159(15) 11.7171(5) 25.9084(17)c /Å 14.8254(2) 14.7925(2) 17.8585(11) 18.101(2) 23.2671(9) 30.351(2)R /° 90 90 90 90 90 90� /° 106.7470(10) 106.8030(10) 106.890(7) 107.098(3) 96.062(3) 90γ /° 90 90 90 90 90 90V/Å3 1616.29(4) 1625.86(4) 2994.3(3) 3082.7(6) 3164.3(2) 10629.6(12)Z 2 2 4 4 2 2T /K 298 (2) 298 (2) 298(2) 298 (2) 298(2) 298(2)F(000) 740 734 1232 1228 1348 4488Dcalcd/g cm-3 1.459 1.437 1.317 1.274 1.351 1.351µ /mm-1 0.827 0.595 1.030 0.763 0.545 0.489λ /Å 0.71073 0.71073 0.71073 0.71073 0.71073 0.71073Rint 0.0433 0.0413 0.0341 0.0740 0.0398 0.0410data/restraints/param 3009/3/222 3019/3/222 5328/0/344 5735/3/344 10123/5/828 2483/4/173GOF 1.053 1.027 0.995 1.072 1.023 1.048R1 [I ) 2σ(I)]a 0.0547 0.0388 0.0641 0.0680 0.0549 0.0797wR2 [I ) 2σ(I)]b 0.1290 0.0889 0.1561 0.1741 0.1399 0.2086

a R1 ) Σ||Fo| - |Fc||/|Fo|. b wR2 ) [Σw(Fo2 - Fc

2)2/Σw(Fo2)2]1/2, where w ) 1/[σ2(Fo

2) + (aP)2 + bP]. P ) (Fo2 + 2Fc

2)/3.

Scheme 2. Assembling Strategies of Compounds 1-6 withHelical Character

Metal-Organic Frameworks with Helical Character Crystal Growth & Design, Vol. 9, No. 3, 2009 1607

values by Glidewell, et al.15 In each cation, the ligand L adoptsthe trans-conformation with the two benzimidazolyl moietieslocated above and below the basal phenylene ring and pointingin the opposite direction. In turn, each L ligand connects twometal(II) atoms to give a zigzag chain structure as seen in Figure2. From the crystal packing diagram of two componds shownin Figure S3-S4 (Supporting Information), it can be seen thatthe cationic chains and nitrate anions are connected byO-H · · ·O hydrogen bonds involving H atoms on the coordina-tion aqua ligands and the nitrate oxygen atoms to form a 3Dsupramolecular network (Table 2).

Interestingly, two types of helical chains constructed viahydrogen bonds between nitrate anions and coordination watermolecules, namely, right-handed P and left-handed M, followinga 21 screw axis running along the b axis are observed in thesolid state of two compounds (Figure 3a). Different helicalchains are alternately arranged and interlinked by M(II) ionscoordinating to water molecules, resulting in meso-helicalinorganic supramolecular layers (Figure 3b), in which thecoordinated water molecule is in a trigonal geometry with twowater-nitrate hydrogen bonds and one from the water-metalcoordination bond. Meanwhile, each nitrate anion involves twohydrogen bonds with two water-nitrate interactions. Such sixcoordinated water molecules, two M2+ ions, and two nitrateanions constitute a unique metal-coordinated 26-membered ringmotif containing P- and M-helices as secondary building units

(SBUs). Through the coordination as well as hydrogen-bondinginteractions, these SBUs in brick-wall fashion are linked into2D inorganic supramolecular layers. Another remarkable featureis that the 2D layers are further assembled into a 3Dorganic-inorganic hybrid supramolecular network by the co-ordiantion of the dipolar organic ligand L with the M2+ ionlocated in the adjacent layers (Figure 3c). Obviously, theresulting complexes 1 and 2 represent very good examples of3D organic-inorganic hybrid frameworks containing meso-helical chains (P + M) trapped by the cooperative associationof coordination interactions and hydrogen bonds in the solidstate.

Structure of Complexes 3 and 4. As compared with nitratesalts, reactions of the dipolar bis-dentate ligand 1,4-bis(benz-imidazol-1-ylmethyl)benzene (L) with MIICl2 under the samereaction conditions give two unexpected 1D helical chains{[M(L)2Cl2] ·DMF ·S}n (M ) Zn(3), S ) C2H5OH; Co(4), S )CH3OH + H2O). X-ray crystallography reveals that compounds3 and 4 have similar structrures except for a slight differenceof partial uncoordinated solvent molecules (ethanol for 3,methanol and water for 4). Here, we choose 3 to represent thedetailed structure. In complex 3, the repeat unit consists of oneneutral [Zn(L)2Cl2] unit, one N,N-dimethylformamide (DMF),and one ethanol molecule. A perspective view of the zinc(II)center of compound 3 is shown in Figure 4 with an atomnumbering scheme. Each Zn(II) atom is coordinated by two Cl-

anions and two N-donor atoms of benzimidazolyl groups derivedfrom two different L ligands. The coordination geometry of theZn(II) center is a slightly distorted tetrahedron. Each ligand Lbridges two zinc(II) ions via nitrogen atoms. Taking the Zn(II)

Figure 2. Infinite 1D zigzag chain structure (cation part) of 1 or 2.The anions and hydrogen atoms are omitted for clarity.

Table 2. Distances (Å) and Angles (°) of Hydrogen Bonds forCompounds 1-5a

D-H · · ·A d(H · · ·A) d(D · · ·A) ∠ D-H · · ·A

1

O(1)-H(1B) · · ·O(3)#1 2.22(3) 2.856(6) 146(4)O(1)-H(1B) · · ·O(5)#1 2.57(2) 2.981(7) 160(4)

2

O(1)-H(1B) · · ·O(3)#1 2.224(19) 2.861(4) 149(3)O(1)-H(1B) · · ·O(5)#1 2.585(15) 3.082(4) 157(3)

3

C(22a)-H(22a) · · ·O(1) 2.267(5) 3.079(5) 146(5)C(15a)-H(15Aa) · · ·O(1) 2.519(4) 3.264(6) 136(4)C(23)-H(23) · · ·Cg1 2.636(5) 3.535(4) 163(5)C(25)-H(25B) · · ·Cg2 2.853(6) 3.766(6) 173(6)

4

C(7a)-H(7a) · · ·O(1) 2.257(5) 3.078(6) 147(4)C(8a)-H(8Aa) · · ·O(1) 2.523(6) 3.277(5) 138(4)C(23)-H(23) · · ·Cg1 2.689(5) 3.595(4) 165(6)C(25)-H(25C) · · ·Cg2 2.967(5) 3.863(4) 156(5)

5

O(13)-H(13A) · · ·O(6) 2.497(4) 2.975(4) 117(2)O(15)-H(15A) · · ·O(13)#2 2.586(3) 3.147(3) 126(2)O(15)-H(15A) · · ·O(14)#2 2.220(4) 2.823(4) 129(2)O(15)-H(15B) · · ·O(10) 1.875(3) 2.677(3) 158(3)C(50)-H(50) · · ·Cg1 2.892(8) 3.740(7) 152(4)C(56)-H(56) · · ·Cg1 2.994(7) 3.689(7) 133(4)

a Symmetry transformation used to generate equivalent atoms. #1 -x+ 3/2, y + 1/2, -z + 1/2; #2 x + 1/2, -y + 1, z + 1/2. Cg1 and Cg2respectively denote the centroids of six-membered and five-memberedrings of the benzimidazolyl ring in the dipolar ligand L.

Figure 3. In 1 and 2: (a) M- and P-helical chains constructed viahydrogen bonding O-H · · ·O interactions; (b) inorganic supramolecularlayer containg meso-helical chains interlocked through metal-watercoordination interactions; (c) 3D organic-inorganic hybrid networkcontaining alternate meso-helical chains trapped by the cooperativeassociation of coordination interactions and hydrogen bonds.


ions as two alternating parallel backbones along the a-axis, theligands L wrap around the Zn(II) ions in P(∆) or M(Λ) fashionto form 1D racemic tube-like single helical chains with a helicalpitch (Hp) of 12.33 Å (Figure 5a). The two benzimidazoleylrings in the ligand L are cis,cis-conformation based on thecentral benzene core with a dihedral angle of 54.8°, while thoseof neighboring ligands around a zinc ion are nearly perpendicularto each other with dihedral angle of 88.7° (Figure 4).

As shown in Figure 5b, both left-handed and right-handedhelical chains have been orderly arranged in the same crystalof 3: there are parallel chains each with the same helicity in the(001) plane and an alternating left-right-handed helix in the (010)plane. Interactions of face-to-face π · · ·π stacking between twowell-overlapping benzimidazolyl rings from two adjacent chainscause the 3D racemic supramolecular network. The shortestdistance between two parallel benzimidazolyl rings of twoadjacent helical chains are 3.675 Å for the same helicity and3.789 Å for the different helicity, respectively. Solvent DMFmolecules are situated within a tube-like helix through thehydrogen bonding C-H · · ·O and edge-to-face C-H · · ·π in-teractions (Figures 4 and 5b), while ethanol molecules are filledamong helical chains (Figure S5, Supporting Information).Because the free ethanol molecule in complex 3 is disorderedand its hydrogen atoms have not been added, the hydrogenbonds involving it have not been discussed here.

Similar to 3, compound 4 also contains P-helical andM-helical chains with 21 screw axis but crystallize as a racemate,in which solvent DMF molecules are hydrogen bonded(C-H · · ·O and C-H · · ·π, Table 2 and Figure S6, SupportingInformation) within tube-like helical chains. Meanwhile, the

solvent molecules CH3OH and H2O in 4 like C2H5OH moleculein 3 only located between different helical chains, indicatingthese solvent molecules do not afford a decisive role in theformation of the helical structure.

Structure of Complexes 5 and 6. Recently, when reactantZn(NO3)2/Co(NO3)2 was replaced with Zn(ClO4)2/Co(ClO4)2

under the same reaction conditions, two new high dimensionalcompounds [Zn(L)2] · (ClO4)2 · 4DMF · 3H2O]n (5) and[Co(L)2(DMF)2](ClO4)2 (6) with helical character were obtained,respectively, showing that the spherical perchlorate anionpossibly plays a role in the formation of the high-dimensionalstructures in the present system. The polymeric structure ofcomplex 5 was confirmed by X-ray single crystal structureanalysis. As illustrated in Figure 6, the Zn(II) ion is four-coordinated by four N atoms from four different L ligands toform a nearly ideal [ZnN4] tetrahedron. The Zn-N mean bondlength of 2.004(8) Å is consistent with that of 1.996(6) Åreported by Barquin and Song, et al.16 The bond angles ofN-Zn-N are in the range of 105.2(3)-117.2(3)° (Table S2,Supporting Information).

In contrast to the 1D chain structure of complexes 1-4, thepolymeric structure of complex 5 is a 2D wave-like networkwith (4,4) or 44 topology, as defined by Robson et al.17 Thezinc(II) atoms serve as nodes, while each L ligand connectstwo zinc(II) atoms and serves as rods (bridging ligand). Withinthe 2D network of 5, all the 1D chains run in two nearlyperpendicular directions and interweave in a “one-over/one-under” fashion. The chains vertical to each other are cross-linkedby coordinating interactions with ZnII ions (as the hinge nodes),generating a 2D wave-like layer. More interestingly, all the 1Dchains in 5 are arranged into a helical mode with differentchirality: one direction is left-handed (M-), while the other isright-handed (P-) (Figure 7a,b), although they have the samecomponents and linking sequence. As far as we know, heliceswith different chiralities crossing coexisting in the same 2Dsystem are rare,18 which makes 5 a new interesting member of2D interwoven networks.

The interwoven network of 5 is stabilized by offset face-to-face π · · ·π stacking interactions arising from two centralbenzene rings from two adjacent ligands L of two neighboringlayers packed by ABAB fashion with centroid-to-centroiddistances of ca. 3.752 Å to complete the final 3D structures(Figure 7c,d). Meanwhile, two ClO4

- anions as well as waterand N,N- dimethylformamide molecules fill between neighboringsheets stabilized by O-H · · ·O hydrogen bonds (Table 2).

Figure 4. (a) ORTEP plot of coordination environment of Zn(II) centerin complex 3 with an atomic labeling scheme. Symmetry code a: 1.5- x, 0.5 + y, 1.5 - z; b: 1.5 - x, -0.5 + y, 1.5 - z; (b) cis,cis-configuration of ligand L in 3.

Figure 5. (a) Portions of 1D tube-like single strand M- and P-helicesin 3, (b) 3D racemic supramolecular network in complex 3 fabricatedby π · · ·π stacking between two benzimidazolyl rings of the adjacenttube-like single helical chains. The solvent molecules and hydrogenatoms are omitted for clarity.

Figure 6. In compound 5, (a) coordination geometry around Zn(II)atom. Symmetry code a: -1 + x, y, z; b: x, -1 + y, z; c: 1 + x, y, z;d: x, 1 + y, z. (b) cis,trans-configuration of ligand L. Hydrogen atoms,perchlorate anions and the solvent molecules were omitted for clarity.


The structure of 6 contains an octahedral CoII atom, whichis coordinated to four trans ligands L and two axial DMFligands. The view of the coordination geometry around thecentral CoII ion is shown in Figure 8. The structure also containstwo uncoordinated perchlorate anions per CoII. The ligands Lin trans,trans-mode connect the CoII atoms into 3D diamond-like19 networks as depicted in Figure 9 with separation of theadjacent CoII · · ·CoII 14.146 Å.

Although the bridging ligands coordinate to the metal CoII

atoms in a square-planar arrangement, the semirigidity of dipolarligand L allows the metal centers to act effectively as distortedtetrahedral nodes, which are further connected by trans,trans-configurational ligands L into a four-connected diamondoid netcontaining mutually perpendicular meso-helical chains (P + M)with a helical pitch (Hp) of 28.292 Å hinged at the metal CoII

ions (Figure 9). Because of the spacious nature of the network,there coexist, in fact, three identical and parallel diamondoid

networks in 6, which interpenetrate to generate the crystalstructure with 3-fold interpenetrated diamondoid networkcontaining meso-helical chains along two mutually perpendiculardirections, respectively (Figure 10). To the best of our knowl-edge, the topological structure presented by compound 6 is veryuncommon.20

As shown in Figure 10, the same directional meso-helicalchains in the 3-fold interpenetrating network are parallel to oneanother mainly deriving from the 3-fold parallel interpenetrationin 6. Moreover, a notable feature in this structure is the lack ofπ · · ·π stacking interactions that are often observed in interpen-etrating diamondoid network structures (in most cases, theligands are in fact side-on to their nearest neighbors from theother network).21-23

Structural Diversity and Dimensional Change. It shouldbe interesting and essential to compare the related arrangement

Figure 7. (a, b) 2D network of complex 5 with (4,4) topology containingvertical crossing P and M helical chains with the central metal ZnII asthe hinge nodes. (c, d) 3D supramolecular structure packed via weakπ · · ·π interactions between the central benzene rings of two adjacent2D layers in ABAB fashion. Hydrogen atoms, perchlorate, anions andthe solvent molecules were omitted for clarity.

Figure 8. Diagram for the coordination environment around the CoII

center with the labels of the crystallographic independent atoms,hydrogen atoms, and perchlorate anions were omitted for clarity (a)and trans,trans-configuration of ligand L (b) in compound 6.

Figure 9. The diamondlike 3D network of 6 containing mutuallyperpendicular meso-helical chains (P + M) hinged in the metal CoII

ions. Hydrogen atoms, perchlorate anions, and the coordinated solventDMF molecules were omitted for clarity.

Figure 10. Three-fold diamond interpenetrating relationship in 6.


and conformation of the ligand L in these MII complexes 1-6.As shown in Scheme 2, the ligand L adopts the trans,trans-form in complexes 1, 2, 6, the cis,cis-form in 3-4, and thecis,trans-form in 5, and thus L could generate two cisoid andone transoid isomers when coordinated to the metal centers inthis study. As indicated earlier, both cisoid and transoid formshave been reported previously for other 1,4-N-donor bridgingligands, such as 1,4-bis(imidazol-1-ylmethyl)naphthalene and3,6-bis(imidazole-1-yl)pyridazine, and it is interesting that theconformations of these ligands observed in the metal complexesappear to be anion-dependent.24 In complexes 1 and 2, the ligandsurrounding the ZnII/CoII centers is in trans-arrangement to form1D chain-like architectures. Considering hydrogen bondingO-H · · ·O interactions, the resulting layers with meso-helix (P+ M) are connected by this trans-arrangement L into a 3Dsupramolecular network in 1-2 (Figure 3). In complexes 3 and4, the ligand bridges the ZnII/CoII atoms or [MIICl2] units incis,cis-conformation to form the 1D helical chain structures.Although L in 5 also takes a cis-arrangement like that in 3-4,its cis,trans-conformation leads to 2D wave-like layer strucutrecontaining verticle crossing P- and M-helical chains with theZnII ions as hinge nodes. For 6, the ligand L adopts a trans-arrangement and trans,trans-conformation; however, the result-ant compound 6 presents four-connected 3-fold interpenetrateddiamondoid nets containing mutully perpenticular meso-helicalchains (P + M). Obviously, the change in the conformationand arrangement of the ligands can also be considered as a factorthat gives rise to these different structures.

Furthermore, from the above descriptions and discussions,the choice of anions is clearly critical in determining themolecular structures of the resultant complexes. In present study,the nature (coordinating ability, size, donor character, etc.) ofthe anions is the underlying reason behind the differences inthe structure of this series of MII complexes. It has been foundthat anions can be divided into two types according to theirhydrogen-bonding nature. So-called spherical anions, such asClO4

- and BF4-, have been found to be poor at classical

hydrogen bonding (such as O-H · · ·O, etc.), whereas nonspheri-cal anions, such as NO3

- and Otf-, have been found to be muchmore readily incorporated into hydrogen bonds.25 This isconsistent with what has been found in the current study. For1-2, in despite of noncoordination to the central MII atoms,the NO3

- anion serves as an acceptor of O-H · · ·O hydrogenbond formed through the interaction of coordinated H2Omolecules and free nitrate anions, and link 1D chains into a 3Dsupromolecular network containing meso-helical chains. Incomplexes 3-4, the Cl- anions directly coordinate to the ZnII/CoII centers as two terminal ligands in the 1D coordination chain,resulting in each M(II) atoms with donor set MN2Cl2 onlyconnecting two cis-arrangement ligand L, in which two nitrogenatoms of two terminal benzimidazolyl groups are in the samedirections with reference to the plane of the core phenyl groupin cis-,cis-conformation, and finally forming a 1D rac-helicalchain. As indicated above, it seems that this structure resultedfrom the cis arrangement and cis,cis-conformation of the ligand,where weak C-H · · ·π and C-H · · ·O interactions from L itselfand solvent DMF molecule also to play a role (Figure 4). In5-6, the weak coordinating ClO4

- anions are not involved inthe classical hydrogen bonds and coordinative interactionsforming the high-dimensional networks though ligand L havingthe same configuration in 1, 2, and 6 and act as the counteranionsresiding in the lattice to balance the charge. Accordingly, wecan see that directing coordination of the semirigid dipolar ligandL to metal centers is the synergy of various factors, but anions

indeed play an important role in inducing the arrangement andconformation of the dipolar ligand L and finally leading to thedifferent topological structures of metal-complexes in the presentreaction system and under the reaction conditions employed.

Luminescent Properties. Metal-organic polymers have beenreported to have ability to affect the emission wavelength andintensity of the organic material through metal coordination.26

Therefore, it is important to investigate the luminescent proper-ties of metal-organic polymers in view of potential applications.The photoluminescent behaviors of polymers 1, 3, 5 and freeligand L were studied in the solid state at room temperature.The emission spectra of 1, 3, 5, and L are depicted in Figure11; apparently, the emission spectra of the complexes 1, 3, and5 closely resemble that of the ligand L excluding the emissionintensity, indicating the fluorescence of the complexes 1, 3, 5are L-based emission. Meanwhile, the blue emission for thecomplexes 1, 3, 5, and L can be observed, where the maximumemission wavelength at 292 nm (under 284 nm excitation) forthe ligand L, 298 nm (under 283 nm excitation) for the complex1, 297 nm (under 283 nm excitation) for the complex 3 and302 nm (under 284 nm excitation) for 5. Additional shoulderpeaks at 307-309 nm for the ligand L and the three zinccomplexes also can be detected. Compared with the emissionspectrum of L, a slightly red shift of 6 nm in 1, 5 nm in 3, and10 nm in 5 has been given, which is considered to mainly arisefrom the coordination of metal atom to ligand. The incorporationof Zn(II) effectively increases the conformational rigidity ofligand and reduces the loss of energy via vibration motions.Thus, the enhanced fluorescence intensities of the three com-plexes are detected. Moreover, from Figure 11, we find thatthe fluorescent intensity of the complexes 1 and 5 are strongerthan that of the complex 3, and it is a possible explanation thatthere is the big conformational rigidity of the solid-state complex1 with 3D supramolecular network constructed by the coopera-tive association of coordination interactions as well as hydrogenbonds O-H · · ·O compared with that of complex 3 by π · · ·πpacking interactions.27 As for 5, the big conformational rigiditymay be attibuted to its own 2D framework structure.

To further understand the fluorescent properties, the fluores-cence quantum yields and lifetime of the complexes 1, 3, 5,and ligand L were investigated. From Table 3, it can be seenthat the quantum yield is higher and the fluorescence lifetimesare longer for complexes 1 and 5 compared with complex 3

Figure 11. Emission spectra of the complexes 1, 3, 5, and ligand L insolid state at room temperature, respectively: black, complex 1; red,complex 3; blue, complex 5, green ligand L.


and ligand L, also derived from the big conformational rigidityof 3D network structures in the solid-state complexes 1 and5.27

Conclusion

In summary, four one-dimensional and two high dimensionalmetal-organic coordination polymers have been successfullysynthesized from ZnII/CoII salts and the dipolar ligand L underconventional solution reaction conditions and structurallycharacterized by X-ray diffraction analyses. The supramolecularstructures of these 1D complexes (for 1-4) and 2D/3Dframework structures (for 5-6) are to a certain extent influencedby the anions, the arrangement and conformation of ligand L,as well as solvent molecules: a 3D supramolecular network withP and M helical chains assembled by hydrogen bonds in 1-2or a 3D supramolecular network containing P and M helicalchains constructed through coordinative interactions in 3-4 isobserved. However, the 2D layer-like compound 5 is assembledby vertical crossing of the P- and M-helical chains with thecentral metal ZnII atoms as the hinge nodes. And 3D compound6 presents a 3-fold interpenetrated diamondoid net containingmutually perpendicular meso-helical chains (P + M) hinged atCoII ions. This study clearly indicates the important role thatthe coordination ability and bulk of the counteranions can playin crystal engineering. Meanwhile, this work may provide apotential route for constructing 3D framework architectures withhelical character by selecting appropriate counteranions andfunctional organic ligands. Moreover, compared with ligand L,complexes 1, 3, and 5 exhibit strong solid-state fluorescenceproperties at room temperature.

Acknowledgment. The authors are grateful for financial aidfrom the National Natural Science Foundation of P. R. China(Grant No. 20772037), Science and Technology Planning Projectof Guangdong Province (Grant No. 2006A10902002), and theN. S. F. of Guangdong Province (Grant No. 06025033).

Supporting Information Available: Additional structural figuresfor ligand L, compounds 1, 2, 3, 4, and TGA curves for compounds 2,3, 5, and 6 as well as X-ray crystallographic files in CIF format forcompounds 1-6 and L ·4H2O. This material is available free of chargevia the Internet at http://pubs.acs.org.

References

(1) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.;Eddaoudi, M.; Kim, J. Nature 2003, 423, 705. (b) Ockwig, N. W.;Delgado Friedrichs, O.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res.2005, 38, 176. (c) Thallapally, P. K.; Tian, J.; Kishan, M. R.;Fernandez, C. A.; Dalgarno, S. J.; McGrail, P. B.; Warren, J. E.;Atwood, J. L. J. Am. Chem. Soc. 2008, 130, 16842–16843. (d) Hong,M. C. Cryst. Growth Des. 2007, 7, 10. (e) Filby, M. H.; Steed, J. W.Coord. Chem. ReV. 2006, 250, 3200. (f) Biradha, K.; Sarkar, M.;Rajput, L. Chem. Commun. 2006, 4169. (g) Robin, A. Y.; Fromm, K.Coord. Chem. ReV. 2006, 250, 2127. (h) Parnham, E. R.; Morris, R. E.

Acc. Chem. Res. 2007, 40, 1005. (i) Batten, S. R.; Robson, R. Angew.Chem., Int. Ed. 1998, 37, 1460. (j) Evans, O. R.; Lin, W. Acc. Chem.Res. 2002, 35, 511. (k) Janiak, C. Dalton Trans. 2003, 2781. (l)Kitagawa, S.; Kitaura, R.; Noro, S. I. Angew. Chem., Int. Ed. 2004,43, 2334.

(2) (a) Song, Y.-F.; Kitson, P. J.; Long, D.-L.; Parenty, A. D. C.; Thatcher,R. J.; Cronin, L. CrystEngComm 2008, 10, 1243. (b) Li, C.-Y.; Liu,C.-S.; Li, J.-R.; Bu, X.-H. Cryst. Growth Des. 2007, 7, 286.

(3) (a) Albrecht, M. Chem. ReV. 2001, 101, 3457. . (b) Moulton, B.;Zaworotko, M. J. Chem. ReV. 2001, 101, 1629. (c) Schmuck, C.Angew. Chem., Int. Ed. 2003, 42, 2448. (d) Berl, V.; Huc, I.; Khoury,R. G.; Krische, M. J.; Lehn, J.-M. Nature 2000, 407, 720. (e) Bu,X.-H.; Tong, M.-L.; Chang, H.-C.; Kitagawa, S.; Batten, S. R. Angew.Chem., Int. Ed. 2004, 43, 192.

(4) (a) Cui, Y.; Lee, S. J.; Lin, W. J. Am. Chem. Soc. 2003, 125, 6014.(b) Zhang, J.-P.; Lin, Y.-Y.; Huang, X.-C.; Chen, X.-M. Chem.Commun. 2005, 1258. (c) Azumaya, I.; Uchida, D.; Kato, T.;Yokoyama, A.; Tanatani, A.; Takayanagi, H.; Yokozawa, T. Angew.Chem., Int. Ed. 2004, 43, 1360. (d) Sun, Y.-Q.; Zhang, J.; Chen, Y.-M.; Yang, G.-Y. Angew. Chem., Int. Ed. 2005, 44, 5814. (e) Rao,C. N. R.; Natarajan, S.; Vaidhyanathan, R. Angew. Chem., Int. Ed.2004, 43, 1466. (f) Ye, B. H.; Tong, M. L.; Chen, X. M. Coord. Chem.ReV. 2005, 249, 545.

(5) (a) Maggard, P. A.; Stern, C. L.; Poeppelmeier, K. R. J. Am. Chem.Soc. 2001, 123, 7742. (b) Austria, C.; Zhang, J.; Valle, H.; Zhang,Q.-C.; Chew, E.; Nguyen, D.-T.; Gu, J. Y.; Feng, P.-Y.; Bu, X.-H.Inorg. Chem. 2007, 46, 6283. (c) McMorran, D. A. Inorg. Chem. 2008,47, 592. (d) Ciurtin, D. M.; Pschirer, N. G.; Smith, M. D.; Bunz,U. H. F.; zur Loye, H.-C. Chem. Mater. 2001, 13, 2743.

(6) (a) Lu, X.-Q.; Qiao, Y.-Q.; He, J.-R.; Pan, M.; Kang, B.-S.; Su, C.-Y.Cryst. Growth Des. 2006, 6, 1910. (b) Beauchamp, D. A.; Loeb, S. J.Supramol. Chem. 2005, 17, 617. (c) Chen, X.-D.; Du, M.; Mak,T. C. W. Chem. Commun. 2005, 4417. (d) Valencia, L.; Bastida, R.;Macias, A.; Vicente, M.; Perez-Lourido, P. New J. Chem. 2005, 29,424. (e) Schultheiss, N.; Powell, D. R.; Bosch, E. Inorg. Chem. 2003,42, 8886. (f) Kawano, T.; Du, C.-X.; Araki, T.; Ueda, I. Inorg. Chem.Commun. 2003, 6, 165. (g) Tuna, F.; Hamblin, J.; Clarkson, G.;Errington, W.; Alcock, N. W.; Hannon, M. J. Chem.-Eur. J. 2002, 8,4957. (h) Steel, P. J.; Sumby, C. J. Inorg. Chem. Commun. 2002, 5,323. (i) Caradoc-Davies, P. L.; Hanton, L. R. Chem. Commun. 2001,1098.

(7) (a) Ranford, J. D.; Vittal, J. J.; Wu, D.; Yang, X. Angew. Chem., Int.Ed. 1999, 38, 3498. (b) Sreenivasulu, B.; Vittal, J. J. Angew. Chem.,Int. Ed. 2004, 43, 5769. (c) Wang, X.; Vittal, J. J. Inorg. Chem.Commun. 2003, 6, 1074. (d) Tey, S. L.; Reddy, M. V.; Subba Rao,G. V.; Chowdari, B.V. R.; Yi, J.; Ding, J.; Vittal, J. J. Chem. Mater.2006, 18, 1587. (e) McMorran, D. A. Inorg. Chem. 2008, 47, 592. (f)Xiao, D.-R.; Wang, E.-B.; An, H.-Y.; Li, Y.-G.; Xu, L. Cryst. GrowthDes. 2007, 7, 506. (g) Enamullah, M.; Sharmin, A.; Hasegawa, M.;Hoshi, T.; Chamayou, A.-C.; Janiak, C. Eur. J. Inorg. Chem. 2006,2146. (h) Zhang, Y.; Jianmin, L.; Nishiura, M.; Deng, W.; Imamoto,T. Chem. Lett. 1999, 1287. (i) Radford, J. D.; Vittal, J. J.; Wu, D.Angew. Chem., Int. Ed. 1998, 37, 1114.

(8) (a) Zhou, X.-X.; Cai, Y.-P.; Zhu, S.-Z.; Zhan, Q.-G.; Liu, M.-S.; Zhou,Z.-Y.; Chen, L. Cryst. Growth Des. 2008, 8, 2076. (b) Cai, Y.-P.; Su,C.-Y.; Zhang, H.-X.; Zhou, Z.-Y.; Zhu, L.-X.; Chan, A. S. C.; Kaim,W. Inorg. Chem. 2003, 42, 163.

(9) Cai, Y.-P.; Zhang, H.-X.; Xu, A.-W.; Su, C.-Y.; Chen, C.-L.; Liu,H.-Q.; Zhang, L.; Kang, B.-S. J. Chem. Soc., Dalton Trans. 2001,2429.

(10) (a) Cai, Y.-P.; Su, C.-Y.; Zhang, H.-X.; Zhou, Z.-Y.; Zhu, L.-X.; Chan,A. S. C.; Liu, H.-Q.; Kang, B.-S. Z. Anorg. Allg. Chem. 2002, 628,2321. (b) Shi, Z.; Thummel, R. P J. Org. Chem. 1995, 60, 5935.

(11) Sheldrick, G. M. SADABS, Version 2.05; University of Gottingen:Gottingen, Germany.

(12) Sheldrick, G. M. SHELXS-97, Program for X-ray Crystal StructureDetermination; University of Gottingen: Germany, 1997.

(13) Sheldrick, G. M. SHELXS-97, Program for X-ray Crystal StructureRefinement; University of Gottingen: Germany, 1997.

(14) Gupta, M.; Mathur, P.; Butcher, R. J. Inorg. Chem. 2001, 40, 878.(15) Lopez Garzon, R.; Godino Salido, M. L.; Low, J. N.; Glidewell, C.

Acta Crystallogr., Sect. C 2003, 59, m291.(16) (a) Barquin, M.; Cancela, J.; Garmendia, M. J. G.; Ntanilla, J. Q.;

Amador, U. Polyhedron 1998, 17, 2373. (b) Han, H.-Y.; Song, Y.-L.;Hou, H.-W.; Fan, Y.-T.; Zhu, Y. J. Chem. Soc., Dalton Trans. 2006,1972.

(17) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460.(18) (a) Feng, Y.-H.; Guo, Y.; Yang, Y.-O.; Liu, Z.-Q.; Liao, D.-Z.; Cheng,

P.; Yan, S.-P.; Jiang, Z.-H. Chem. Commun. 2007, 3643. (b) Wang,

Table 3. Fluorescence Lifetimes (τ), Fluorescence Quantum Yields(Φ), Optical Density (A), Maximum Excitation Wavelength (λmax),

Fitted Value (�2)a

compound Φ A λmax-ex λmax-em τ (ns) �2

1 0.87 0.005 283 298 16.8 0.973 0.50 0.032 283 297 13.6 0.995 0.96 0.007 284 302 17.2 0.97L 0.50 0.013 284 292 9.5 0.97

a Notes: Samples were prepared to have an optical density of e0.05at the λmax. The �2 for each decay profile is also presented. All of thesephotophysical properties were measured in DMF/acetonitrile, except forthe fluorescence quantum yields measured in ethanol.


R.-H.; Han, L.; Xu, L.-J.; Gong, Y.-Q.; Zhou, Y.-F.; Hong, M.-C.;Chan, A. S. C. 2004, 3751.

(19) Wells, A. F. Three-Dimensional Nets and Polyhedra; Wiley-Inter-science: New York, 1977.

(20) (a) Genuis, E. D.; Kelly, J. A.; Patel, M.; McDonald, R.; Ferguson,M. J; Greidanus-Strom, G. Inorg. Chem. 2008, 47, 6184. (b) Ge, C. H.;Zhang, X. D.; Zhang, P.; Guan, W.; Guo, F.; Liu, Q. T. Polyhedron2003, 22, 3493.

(21) (a) Reddy, D. S.; Dewa, T.; Endo, K.; Aoyama, Y. Angew. Chem.,Int. Ed. 2000, 39, 4266. (b) Sinzer, K.; Hunig, S.; Jopp, M.; Bauer,D.; Bietsch, W.; von Schutz, J. U.; Wolf, H. C.; Kremer, R. K.;Metzenthin, T.; Bau, R.; Khan, S. I.; Lindbaum, A.; Lengauer, C. L.;Tillmanns, E. J. Am. Chem. Soc. 1993, 115, 7696.

(22) (a) Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1990, 112, 1546.(b) Yaghi, O. M.; Li, G. Angew. Chem., Int. Ed. Engl. 1995, 34, 207.(c) Lopez, S.; Kahraman, M.; Harmata, M.; Keller, S. W. Inorg. Chem.1997, 36, 6138.

(23) (a) Carlucci, L.; Ciani, G.; Moret, M.; Proserpio, D. M.; Rizzato, S.Chem. Mater. 2002, 14, 12. (b) Blake, A. J.; Champness, N. R.; Chung,S. S. M.; Li, W.-S.; Schroder, M. Chem. Commun. 1997, 1005–1006.

(24) (a) Begley, M. J.; Hubberstey, P.; Stroud, J. J. Chem. Soc., DaltonTrans. 1996, 4295. (b) Hirsch, K. A.; Wilson, S. R.; Moore, J. S.Inorg. Chem. 1997, 36, 2960. (c) Li, C.-Y.; Liu, C.-S.; Li, J.-R.; Bu,X.-H. Cryst. Growth Des. 2007, 7, 286.

(25) Beatty, A. M. CrystEngComm 2001, 51, 1.(26) (a) Wu, G.; Wang, X.-F.; Okamura, T.; Sun, W.-Y.; Ueyama, N. Inorg.

Chem. 2006, 45, 8523. (b) Ciurtin, D. M.; Pschirer, N. G.; Smith,M. D.; Bunz, U. H. F.; zur Loye, H. C. Chem. Mater. 2001, 13, 2743.(c) Dong, Y.-B.; Wang, P.; Huang, R.-Q.; Smith, M. D. Inorg. Chem.2004, 43, 4727.

(27) Xu, J.-G.; Wang, Z.-B. Fluorescence Analytical Methods, 3rd ed;Chinese Science Publishing Company: Beijing, 2006.

CG8013317


construction of three-dimensional metal−organic frameworks with helical character through...

Documents