Zn (II)-1, 2, 4-Triazolate Coordination Complexes

give colorless prismatic crystals, which were collected by filtration. (yield 0.4 g, 68% on the basis of Cd). Anal. Calcd for C6H8N10CdS2: C, 18.16; H...
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CRYSTAL GROWTH & DESIGN

Construction of Cd/Zn(II)-1,2,4-Triazolate Coordination Complexes via Changing Substituents and Anions

2006 VOL. 6, NO. 9 2126-2135

Quan-Guo Zhai, Xiao-Yuan Wu, Shu-Mei Chen, Can-Zhong Lu,* and Wen-Bin Yang State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P.R. China ReceiVed June 15, 2006; ReVised Manuscript ReceiVed July 21, 2006

ABSTRACT: A series of zero- to three-dimensional Cd/Zn(II)-1,2,4-triazolate coordination complexes have been obtained by changing the anions and the substituents on the triazole ring. Cd2(2-pytrz)2Cl4 (1) and Cd3(dpatrz)4Cl6 (2) (2-pytrz ) 3,5-di(pyrid-2-yl)-1,2,4triazole and dpatrz ) 3,5-di(n-propyl)-4-amino- 1,2,4-triazole) have discrete binuclear and trinuclear structures, respectively. Cd3(atrz)4Cl6 (3) and Cd(atrz)2(SCN)2 (4) (atrz ) 4-amino-1,2,4-triazole) are polymeric 1D chains constructed from trinuclear cadmium units and mononuclear cores. Cd(datrz)I (5), Zn(dmtrz)Cl (6), and Cd3(dmatrz)4(N3)6 (7) (datrz ) 3,5-diamino-1,2,4-triazole, dmtrz ) 3,5-dimethyl-1,2,4-triazole, and dmatrz ) 3,5-dimethyl-4-amino-1,2,4-triazole) all show two-dimensional layer structures. Complexes 5 and 6 are 2D grids based on binuclear clusters and present (4.82)metal(4.82)trz topology. Complex 7 is of 2D (4,4) topology when trinuclear cadmium units are regarded as four-connected nodes. For complexes 1-7, weak hydrogen-bonding contacts link the discrete polynuclear clusters, 1D chains, or 2D layers to form three-dimensional supramolecular structures. Zn2(trz)3Cl (8) (trz ) 1,2,4-triazole) presents an interesting 3D network based on three nonequivalent nodes and has a (46861224)(861254)(42841236)3 topology. Complexes 1-8 all exhibit strong blue fluorescence emission bands in the solid state at ambient temperature. Introduction The design and synthesis of metal-organic complexes have been flourishing in recent years because of their intriguing architectures1 and potential application to gas storage, ion change, catalysis, and so on. 2 Although a variety of metal coordination frameworks with beautiful topology and interesting properties have been synthesized to date, rational control in the construction of polymeric networks remains a great challenge in crystal engineering. Now the utilization of a polynuclear metal cluster as building blocks has proved to be a versatile strategy to construct supramolecular coordination frameworks, especially highly connected structures.3 Usually, rigid or flexible multidentate ligands act as organic connectors to link these polynuclear clusters to form extended architectures varying from one- to three-dimensions. Although a large number of organic molecules have been investigated as potential linkers, metalorganic frameworks incorporating polycarboxylate and polypyridine ligands have witnessed the most important development.1-3 However, organic ligands offering different chargebalance requirements, alternative linking modes, and orientation of donor groups are closely related to the structures and applications of materials. The development of new ligand systems is continuously an important aspect for the chemistry of metal-organic coordination polymer. 1,2,4-triazole and, in particular, its derivatives gain more and more interest as ligands to bridge metal ions because of their potential bridging fashions (µ1,2, µ2,4, and µ1,2,4). Many triazolebased polynuclear compounds have been reported to date, including dinuclear, linear trinuclear, cyclic trinuclear, and hexanuclear ring complexes.4 However, coordination polymers constructed of metal-triazole polynuclear clusters are rare, especially highly dimensional networks.4b,4h Recently, we described the first 3D example5 based on µ3-oxo bridged trinuclear [CuII3(µ3-O)(µ3-trz)3]+ units exhibiting a six-connected porous self-penetrating network. Moreover, we have also obtained a series of novel planar tetranuclear [CuI4L4]4+ (L ) * To whom correspondence should be addressed. E-mail: czlu@ ms.fjirsm.ac.cn. Fax: 86-591-83714946. Tel.: 86-591-83705794.

Scheme 1

1,2,4-triazole derivatives) clusters when large polyoxometalate building groups are introduced.6 As a part of our ongoing efforts in the design and synthesis of polynuclear metal-triazole clusters and multidimensional coordination polymers based on them, we chose different 1,2,4-trazole ligands (Scheme 1) and anions (Cl-, I-, SCN-, and N3-) in our experiments to investigate the influence of substituents and the second or third bridging ligand. As a result, a series of novel coordination complexes with a variety of zero-, one-, two-, and three-dimensional frameworks were isolated. These compounds, namely, Cd2(2pytrz)2Cl4 (1), Cd3(dpatrz)4Cl6 (2), Cd3(atrz)2Cl6 (3), Cd(atrz)2(SCN)2 (4), Cd(datrz)I (5), Zn(dmtrz)Cl (6), Cd3(dmatrz)4(N3)6 (7), and Zn2(trz)3Cl (8) (trz ) 1,2,4-triazole, atrz ) 4-amino1,2,4- triazole, datrz ) 3,5-diamino-1,2,4-triazole, dmtrz ) 3,5dimethyl-1,2,4-triazole, dmatrz ) 3,5-dimethyl-4-amino-1,2,4triazole, dpatrz ) 3,5-di(n-propyl)-4-amino-1,2,4-triazole, and 2-pytrz ) 3,5-di(pyrid-2-yl)-1,2,4- triazole), were synthesized by the solution evaporation method or hydrothermal technique (Scheme 2) and characterized via single-crystal X-ray diffraction analysis, FT-IR, X-ray powder diffraction (XRPD), TGA, and luminescence properties.

10.1021/cg060359k CCC: $33.50 © 2006 American Chemical Society Published on Web 08/19/2006

Construction of Cd/Zn(II)-1,2,4-Triazolates Scheme 2.

Syntheses of Complexes 1-8

Experimental Section Materials and General Procedures. 4-Amino-1,2,4-triazole (atrz), 3,5-dimethyl-4-amino-1,2,4-triazole (dmatrz), 3,5- dimethyl-1,2,4-triazole (dmtrz), 3,5-di(n-propyl)-4-amino-1,2,4-triazole (dpatrz), and 3,5di(pyrid-2-yl)-1,2,4-triazole (2-pytrz) were prepared according to the literature methods. 7 Other ligands and chemicals were obtained from commercial sources and used without further purification. The IR spectra (KBr pellets) were recorded on a Magna 750 FT-IR spectrophotometer. C, H, and N elemental analyses were determined on an Elementar Vario EL III elemental analyzer. Powder X-ray diffraction data were recorded on a Rigaku MultiFlex diffractometer with a scan speed of 0.05-0.2° min-1. Thermal stability studies were carried out on a NETSCHZ STA-449C thermoanalyzer under N2 (40-1000 °C range) at a heating rate of 10° min-1. Fluorescence spectra were measured with an Edinburgh Analytical instrument FLS920. Synthesis. Cd2(2-pytrz)2Cl4 (1). A mixture of CdCl2‚2.5H2O (0.23 g, 1.0 mmol), 2-pytrz (0.22 g, 1.0 mmol), and H2O (10 mL) was heated at 140 °C for 3 days under autogenous pressure. The mixture was cooled to room temperature at a rate of 0.5 °C min-1. Almost phase-pure colorless block crystals were collected, washed with H2O, and air-dried (yield 0.23 g, 56% on the basis of Cd). Anal. Calcd for C24H18N10Cd2Cl4: C, 35.45; H, 2.23; N, 17.23. Found: C, 35.20; H, 2.30; N, 17.18. IR (KBr pellets, λ, cm-1): 3435 (s), 3269 (s), 3078 (w), 1608 (s), 1571 (w), 1553 (m), 1477 (m), 1466 (s), 1456 (s), 1434 (w), 1380 (m), 1320 (w), 1291 (w), 1261 (w), 1184 (w), 1156 (m), 1147 (w), 1099 (w), 1053 (w), 1016 (s), 996 (w), 808 (s), 759 (m), 731 (s), 640 (w), 623 (w), 550 (w), 409 (w). Cd3(dpatrz)4Cl6 (2). A mixture of CdCl2‚2.5H2O (0.45 g, 2.0 mmol), dpatrz (0.50 g, 3.0 mmol), and H2O (20 mL) was stirred for 5 h at room temperature. The white precipitate was filtered off. The filtrate was allowed to stand at room temperature for about 1 month to give colorless prismatic crystals, which were collected by filtration, washed with ethanol, and air-dried (yield 0.62, 75% on the basis of Cd). Anal. Calcd for C32H64N16Cd3Cl6: C, 31.43; H, 5.28; N, 18.33. Found: C, 31.52; H, 5.34; N, 18.21. IR (KBr pellets, λ, cm-1): 3318 (s), 3245 (w), 3187 (s), 2964 (s), 2935 (s), 2873 (m), 1619 (m), 1533 (s), 1464 (m), 1381 (m), 1289 (w), 1212 (w), 1096 (w), 1076 (w), 1057 (w), 980 (m), 892 (w), 861 (w), 814 (w), 716 (w), 523 (w). Cd3(atrz)4Cl6 (3). A mixture of CdCl2‚2.5H2O (0.45 g, 2.0 mmol), atrz (0.25 g, 3.0 mmol), and H2O (20 mL) was stirred for 5 h at room temperature. The white precipitate was filtered off. The filtrate was allowed to stand to give colorless block crystals, which were collected by filtration, washed with ethanol, and air-dried (yield 0.47 g, 80% on the basis of Cd). Anal. Calcd for C8H16N16Cd3Cl6: C, 10.84; H, 1.82; N, 25.29. Found: C, 10.88; H, 1.90; N, 25.25. IR (KBr pellets, λ, cm-1): 3448 (w), 3323 (s), 3282 (s), 3250(m), 3199 (s), 3161 (w), 3105 (s), 1808 (w), 1712 (w), 1672 (w), 1619 (s), 1542 (s), 1395 (m), 1333 (m), 1222 (w), 1207 (s), 1079 (s), 1045 (s), 1026 (m), 1012 (m), 910 (m), 880 (m), 858 (m), 688 (w), 620 (m). Cd(atrz)2(SCN)2 (4). To a solution of Cd(NO3)2‚4H2O (0.46 g, 1.5 mmol) and atrz (0.25 g, 3.0 mmol) in 20 mL H2O was slowly added a

Crystal Growth & Design, Vol. 6, No. 9, 2006 2127 solution of KSCN (0.29 g, 3.0 mmol) in 5 mL of H2O with stirring. The white precipitate was filtered off after the mixture was stirred at room temperature for about 5 h. The filtrate was allowed to stand to give colorless prismatic crystals, which were collected by filtration. (yield 0.4 g, 68% on the basis of Cd). Anal. Calcd for C6H8N10CdS2: C, 18.16; H, 2.03; N, 35.30. Found: C, 18.21; H, 1.99; N, 35.38. IR (KBr pellets, λ, cm-1): 3437 (br), 3327 (m), 3275 (m), 3103 (m), 2099 (s), 1619 (m), 1521 (w), 1384 (w), 1193 (m), 1068 (m), 985 (m), 952 (w), 893 (w), 861 (w), 774 (w), 677 (w), 624 (m), 469 (w). Cd(datrz)I (5). A mixture of Cd(NO3)2‚4H2O (0.31 g, 1.0 mmol), datrz (0.10 g, 1.0 mmol), KI (0.17 g, 1.0 mmol), and H2O (10 mL) was heated at 180 °C for 5 days under autogenous pressure. The mixture was cooled to room temperature at a rate of 0.5 °C min-1. Phase-pure colorless block crystals were collected, washed with H2O, and air-dried (yield 0.21 g, 62% on the basis of Cd). Anal. Calcd for C2H4N5CdI: C, 7.12; H, 1.19; N, 20.77. Found: C, 7.08; H, 1.25; N, 20.79. IR (KBr pellets, λ, cm-1): 3367 (s), 1895 (w), 1615 (m), 1587 (m), 1574 (m), 1515 (m), 1465 (m), 1395 (m), 1329 (w), 985 (m), 858 (m), 783 (m), 712 (w), 678 (w). Zn(dmtrz)Cl (6). Method A: A mixture of ZnF2 (0.16 g, 1.5 mmol), dmtrz (0.15 g, 1.5 mmol), KCl (0.11 g, 1.5 mmol), and H2O (10 mL) was heated at 180 °C for 5 days under autogenous pressure. The mixture was cooled to room temperature at a rate of 0.5 °C min-1. Colorless block crystals were isolated manually from white unidentified powder, washed with H2O, and air-dried (yield 0.10 g, 33% on the basis of Zn). Method B: A mixture of Zn(OAc)2‚2H2O (0.44 g, 2.0 mmol), dmtrz (0.19 g, 2.0 mmol), KCl (0.15 g, 2.0 mmol), and H2O (20 mL) was stirred for 5 h at room temperature. The filtrate was allowed to stand for about 1 month to give colorless block crystals, which were collected by filtration, washed with ethanol, and air-dried (yield 0.34 g, 86% on the basis of Zn). Anal. Calcd for C4H6N3ZnCl: C, 24.39; H, 3.07; N, 21.33. Found: C, 24.41; H, 2.99; N, 21.43. IR (KBr pellets, λ, cm-1): 3435 (br), 3014 (w), 2969 (w), 2932 (m), 2671 (w), 2215 (w), 1627 (w), 1504 (s), 1416 (s), 1379 (s), 1339 (s), 1135 (s), 1043 (m), 1000 (m), 878 (w), 777 (s), 701 (m), 624 (m). Cd3(dmatrz)4(N3)6 (7). To a solution of Cd(NO3)2‚4H2O (0.46 g, 1.5 mmol) and dmatrz (0.22 g, 2.0 mmol) in 40 mL H2O was slowly added a solution of NaN3 (0.18 g, 3.0 mmol) in 5 mL of H2O with stirring. The resulting solution was stirred at room temperature for 5 h and then filtered. Colorless block crystals were obtained by slow evaporation of the resulting solution (yield 0.37 g, 71% on the basis of Cd). Anal. Calcd for C16H32N34Cd3: C, 18.52; H, 3.11; N, 45.88. Found: C, 18.50; H, 3.06; N, 45.93. IR (KBr pellets, λ, cm-1): 3409 (m), 3320 (m), 3276 (m), 3192 (m), 3166 (m), 2977 (w), 2086 (s), 2056 (s), 2042 (s), 1634 (m), 1554 (m), 1422 (w), 1385 (w), 1350 (m), 1294 (w), 1264 (w), 1083 (w), 1055 (w), 999 (w), 930 (m), 769 (w), 731 (w), 646 (w), 528 (w). Zn2(trz)3Cl (8). A mixture of Zn(OAc)2‚2H2O (0.22 g, 1.0 mmol), trz (0.11 g, 1.5 mmol), KCl (0.038 g, 0.5 mmol), and H2O (10 mL) was heated at 180 °C for 5 days under autogenous pressure. The mixture was cooled to room temperature at a rate of 0.5 °C min-1. Almost pure colorless prismatic crystals were collected, washed with H2O, and air-dried (yield 0.13 g, 68% on the basis of Zn). Anal. Calcd for C6H6N9Zn2Cl: C, 19.45; H, 1.63; N, 34.03. Found: C, 19.33; H, 1.59; N, 34.41. IR (KBr pellets, λ, cm-1): 3401(br), 3129 (m), 3106 (s), 3045 (w), 2948 (w), 2732 (w), 2620 (w), 2517 (w), 2482 (w), 2394 (w), 2315 (w), 1816 (w), 1797 (w), 1770 (w), 1560 (w), 1532 (s), 1440 (w), 1332 (w), 1303 (s), 1222 (m), 1180 (s), 1100 (s), 1044 (m), 1007 (m), 911 (w), 888 (m), 731 (w), 659 (s). Crystal Structure Determination. Suitable single crystals of 1-8 were carefully selected under an optical microscope and glued to thin glass fibers. Crystallographic data for all compounds were collected with a Siemens Smart CCD Diffractometer with graphite-monochromated Mo KR radiation (λ ) 0.71073 Å) at T ) 293(2) K. Absorption corrections were made using the SADABS program. 8 The structures were solved using the direct method and refined by full-matrix leastsquares methods on F2 by using the Shelx-97 program package.9 All non-hydrogen atoms were refined anisotropically. Positions of the hydrogen atoms attached to carbon and nitrogen atoms were fixed at their ideal positions. CCDC 608879 (1), 608880 (2), 608881 (3), 608882 (4), 608883 (5), 608884 (6), 608885 (7), and 608886 (8) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data

2128 Crystal Growth & Design, Vol. 6, No. 9, 2006

Zhai et al.

Table 1. Crystal Data and Structure Refinements for Compounds 1-8

empirical formula fw space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z dcalcd (g/cm3) µ (Mo KR) (mm-1) F (000) no. of reflns collected/unique no. of unique reflns (R(int)) params GOF on F2 R1,a wR2a [I > 2σ(I)] R1, wR2 (all data) max, min peaks (e Å-3) a

1

2

3

4

5

C24H18N10Cd2Cl4 813.08 P-1 8.172(12) 8.807(10) 11.067(10) 67.496(9) 75.765(10) 70.771(9) 688.212(10) 1 1.962 1.970 396 5315/3116

C32H64N16Cd3Cl6 1222.89 P2(1)/n 11.472(6) 15.089(8) 14.977(10) 90 94.601(3) 90 2584.2(3) 1 1.572 1.573 1228 19 624/5914

C8H16N16Cd3Cl6 886.27 P-1 9.089(3) 9.179(3) 9.240(3) 70.89(2) 71.710(2) 62.637(17) 634.5(4) 1 2.319 3.156 422 4853/2831

C6H8N10CdS2 396.74 P2(1)/n 9.626(11) 5.730(5) 12.123(13) 90 100.094(6) 90 658.25(12) 2 2.002 1.979 388 4808/1515

C2H4N5CdI 337.40 P2(1)/c 7.114(14) 9.956(11) 10.731(18) 90 108.277(7) 90 721.7(2) 4 3.105 7.224 608 5396/1645

0.0134

0.0247

0.0130

0.0207

181 1.060 0.0301, 0.0791 0.0323, 0.0812 0.831, -0.759

259 1.111 0.0387, 0.1020 0.0433, 0.1062 1.255, -0.694

152 1.073 0.0239, 0.0614 0.0263, 0.0626 1.104, -0.750

89 1.023 0.0269, 0.0634 0.0325, 0.0670 0.828, -0.453

6

7

8

C4H6N3ZnCl 196.94 P2(1)/c 7.6304(6) 9.2864(8) 9.8460(8) 90 100.126(3) 90 686.81(10) 4 1.905 3.871 392 5042/1566

C16H32N34Cd3 1037.96 Pbca 17.782(8) 9.973 (4) 20.697(9) 90 90 90 3670.4(3) 4 1.878 1.788 2040 27 003/4202

C6H6N9Zn2Cl 370.39 Pnma 7.5093(11) 9.9120(13) 17.457(2) 90 90 90 1299.4(3) 4 1.893 3.893 728 9500/1569

0.0314

0.0150

0.0327

0.0713

82 1.000 0.0331, 0.0887 0.0384, 0.0930 0.767, -1.972

82 1.026 0.0280, 0.0731 0.0302, 0.0748 0.590, -0.395

241 1.035 0.0384, 0.0975 0.0412, 0.0998 0.834, -0.584

94 1.087 0.0595, 0.1158 0.0755, 0.1247 1.042, -0.646

R1 ) ∑(|Fo| - |Fc|)/∑|Fo|, wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]0.5.

Center via www.ccdc.cam.ac.uk/data_request/cif. Crystal data as well as details of data collection and refinement for 1-8 are summarized in Table 1. Selected bonded lengths and angles are listed in Table 2.

Results and Discussion Structure Description. Cd2(2-pytrz)2Cl4 (1): A Dinuclear Structure. Compound 1 shows a dinuclear structure with the asymmetric unit containing one crystallographically unique Cd2+ ion, one neutral 2-pytrz ligand, and two unique Cl- ions. A view of the molecular structure, together with its numbering scheme, is depicted in Figure 1a. The cadmium(II) atom is in a distorted [CdN2Cl3] trigonal bipyramid, of which the coordination sphere for Cd1 is defined by one pyridyl nitrogen (Cd-N ) 2.321(2) Å), one triazole nitrogen atom (Cd-N ) 2.361(2) Å), and three Cl- ions. Two of the chloride anions act as µ2-bridges and the Cd-Cl distances are in the range of 2.4271(8)-2.6446(8) Å. The Cd1-Cl2-Cd1A angle is 95.00(3)°. This gives rise to a Cd‚‚‚Cd distance of 3.823(3) Å. The dihedral angle between the coordinated pyridyl group and the triazolate ring is 9.5(5)°, whereas that between the noncoordinated pyridyl group and the triazolate ring is 15.3(5)°. It is worth noting that although a variety of coordinated complexes based on anionic 2-pytrz ligands have been reported, only one example containing the neutral 2-pytrz was structurally characterized more recently.10 As shown in Figure 1b, the solid structure of 1 is further stabilized by interesting hydrogen-bonding interactions (type I-IV). First, the dinuclear species are held together into 1D chains via their complementary N(3)‚‚‚Cl(1)#1 hydrogen bonding (type I: N(3)‚‚‚Cl(1)#1 ) 3.440(3) Å, #1 ) -x, -y + 1, -z 1). Further, another two kinds of hydrogen bonds link the 1D chains to generate a three-dimensional network (type II: C(4)‚‚‚N(3)#2 ) 3.049(4) Å, #2 ) -x + 1, -y + 1, -z - 1; type III: C(11)‚‚‚Cl(1)#3 ) 3.674(4) Å, #3 ) -x - 1, -y + 1, -z). Moreover, there exists a second weak C-H‚‚‚Cl interaction in the dinuclear unit itself (type IV: C(12)‚‚‚Cl(1)#4 ) 3.438(4) Å, #4 ) -x, -y, -z). Cd3(dpatrz)4Cl6 (2): A Linear Trinuclear Structure. When we decrease the bulk of substituents on the triazole ring (using dpatrz), complex 2 exhibits a linear trinuclear structure. The centrosymmetric trinuclear species is shown in Figure 2a. In

the trinuclear unit, the central cadmium (Cd2) is surrounded by four N1, N2 bridging triazole ligands and two chloride anions. The octahedron of the central Cd2+ is elongated along the Cl2-Cd2-Cl2A axis, given the distances Cd(2)-N(3) ) 2.346(2) Å, Cd(2)-N(6) ) 2.450(2) Å, and Cd(2)-Cl(2) ) 2.5801(8) Å, respectively. Atom Cd2 links to Cd1 via one µ2bridging chloride atom and two µ1,2-bridging dpatrz ligands. Another two terminal Cl- ions complete the coordination geometry of a distorted trigonal bipyramidal Cd1 ion in the unit. The Cd1-Cl2-Cd2 bridging angle is 93.14(2)°, and the Cd1‚‚‚Cd2 distance is 3.779(3) Å. To the best of our knowledge, only two linear trimers of this bridging type, containing two N1, N2 triazole ligands and one µ2-Cl atom, have been reported previously,4h,11 even though 1,2,4-triazole ligands and metal ions easily form a linear trinuclear structure. Furthermore, the adjacent trimers are connected together through weak C-H‚‚‚Cl and N-H‚‚‚Cl hydrogen-bonding interactions to form a 2D supramolecular network (Figure 2b). The 2D net presents a (4, 4) topology regarding trinuclear units as nodes and hydrogen bonds as linkers. It is interesting that all the flexible propyl groups run to the cavities of (4, 4) nets because of their large bulk. Cd3(atrz)4Cl6 (3): A 1D Chain Based on a Trinuclear Unit. X-ray crystallographic analysis reveals that 3 is made of linear trinuclear cadmium units, linked by the double Cl- bridges to form 1D chains. As shown in Figure 3a, the fundamental trinuclear unit is similar to that in 2, except that the terminal cadmium(II) atom is coordinated to other Cl- ions to exhibit an octahedral geometry. Four triazole ligands are coordinated to the central Cd2+ ion and form a square plane, with the octahedron elongated along the Cl-Cd-Cl axis (Cd-N ) 2.296(3) and 2.364(3) Å, Cd-Cl ) 2.6246(11) Å). The octahedral coordination sphere of the terminal Cd2+ ion contains three chloride atoms and two atrz ligands. The Cd-Cl distances range from 2.5435(11) to 2.7177(10) Å, and the Cd-N distances are 2.381(3) and 2.403(3) Å. These distances and corresponding angles are indicative of a distorted octahedron. The Cd‚‚‚Cd separation of 3.905(6) Å is slightly longer than that in compound 2. Two terminal chloride atoms in the fundamental unit adopt a double-bridging fashion to connect with other units. On the basis of this linking mode, all trinuclear cadmium clusters form

Construction of Cd/Zn(II)-1,2,4-Triazolates

Crystal Growth & Design, Vol. 6, No. 9, 2006 2129

Table 2. Selected Bond Lengths (Å) and Angles (deg) for Compounds 1-8a Cd(1)-N(5) Cd(1)-N(2) N(5)-Cd(1)-N(2) N(5)-Cd(1)-Cl(1) N(2)-Cd(1)-Cl(1) N(5)-Cd(1)-Cl(2)

2.321(2) 2.361(2) 72.07(9) 115.01(7) 103.27(7) 131.38(7)

Cd2(2-pytrz)2Cl4(1) Cd(1)-Cl(1) 2.4271(8) Cd(1)-Cl(2) 2.5401(9) N(2)-Cd(1)-Cl(2) 91.96(6) Cl(1)-Cd(1)-Cl(2) 113.28(3) N(5)-Cd(1)-Cl(2)#1 87.77(7) N(2)-Cd(1)-Cl(2)#1 150.14(6)

Cd(1)-N(7) Cd(1)-N(4) Cd(1)-Cl(1) N(7)-Cd(1)-N(4) N(7)-Cd(1)-Cl(1) N(4)-Cd(1)-Cl(1) N(7)-Cd(1)-Cl(3) N(4)-Cd(1)-Cl(3) Cl(1)-Cd(1)-Cl(3) N(7)-Cd(1)-Cl(2)

2.279(3) 2.369(2) 2.4976(10) 100.68(10) 105.34(7) 152.08(8) 103.21(7) 90.96(7) 92.79(3) 88.15(7)

Cd3(dpatrz)4Cl6 (2) Cd(1)-Cl(3) 2.5210(9) Cd(1)-Cl(2) 2.6231(8) Cd(2)-N(3) 2.346(2) N(4)-Cd(1)-Cl(2) 81.70(7) Cl(1)-Cd(1)-Cl(2) 89.14(3) Cl(3)-Cd(1)-Cl(2) 167.50(3) N(3)#1-Cd(2)-N(3) 180.00(1) N(3)-Cd(2)-N(6)#1 87.67(8) N(3)-Cd(2)-N(6) 92.33(8) N(6)#1-Cd(2)-N(6) 180.00(11)

Cd(1)-N(1) Cd(1)-N(4) Cd(1)-Cl(3) N(1)-Cd(1)-N(1)#1 N(1)-Cd(1)-N(4)#1 N(1)-Cd(1)-N(4) N(4)#1-Cd(1)-N(4) N(1)-Cd(1)-Cl(3) N(1)#1-Cd(1)-Cl(3) N(4)#1-Cd(1)-Cl(3) N(4)-Cd(1)-Cl(3) N(4)-Cd(1)-Cl(3)#1

2.296(3) 2.364(3) 2.6246(11) 180.0(2) 90.82(9) 89.18(9) 180.00(13) 94.15(7) 85.85(7) 86.56(7) 93.44(7) 86.56(7)

Cd3(atrz)4Cl6 (3) Cd(2)-N(2) Cd(2)-N(3) Cd(2)-Cl(2) Cl(3)-Cd(1)-Cl(3)#1 N(2)-Cd(2)-N(3) N(2)-Cd(2)-Cl(2) N(3)-Cd(2)-Cl(2) N(2)-Cd(2)-Cl(1) N(3)-Cd(2)-Cl(1) Cl(2)-Cd(2)-Cl(1) N(2)-Cd(2)-Cl(3) N(3)-Cd(2)-Cl(3)

Cd(1)-N(2) N(2)#1-Cd(1)-N(2) N(2)#1-Cd(1)-N(4) N(2)-Cd(1)-N(4)

2.293(3) 180.00(2) 89.46(10) 90.54(10)

Cd(1)-N(3) Cd(1)-N(4) N(3)-Cd(1)-N(4) N(3)-Cd(1)-N(1)

Cd(1)-Cl(2)#1 Cl(1)-Cd(1)-Cl(2)#1 Cl(2)-Cd(1)-Cl(2)#1

Cd(2)-N(6) Cd(2)-Cl(2)

2.6446(8) 105.20(3) 85.00(3)

2.450(2) 2.5801(8)

N(3)-Cd(2)-Cl(2)#1 N(6)-Cd(2)-Cl(2)#1 N(3)-Cd(2)-Cl(2) N(6)-Cd(2)-Cl(2) Cl(2)#1-Cd(2)-Cl(2)

94.54(7) 91.85(6) 85.46(7) 88.15(6) 180.00(2)

Cd(2)-Cl(1) Cd(2)-Cl(3) Cd(2)-Cl(1)#2 Cl(2)-Cd(2)-Cl(3) Cl(1)-Cd(2)-Cl(3) N(2)-Cd(2)-Cl(1)#2 N(3)-Cd(2)-Cl(1)#2 Cl(2)-Cd(2)-Cl(1)#2 Cl(1)-Cd(2)-Cl(1)#2 Cl(3)-Cd(2)-Cl(1)#2

2.5698(12) 2.6730(12) 2.7177(10) 173.41(2) 90.42(4) 83.99(7) 170.06(6) 91.90(4) 88.69(3) 90.32(4)

Cd(atrz)2(SCN)2 (4) Cd(1)-N(4) 2.332(2) N(4)-Cd(1)-N(4)#1 180.00(5) N(2)-Cd(1)-S(1)#1 92.30(7) N(4)-Cd(1)-S(1)#1 91.01(7)

Cd(1)-S(1) N(2)-Cd(1)-S(1) N(4)-Cd(1)-S(1) S(1)#1-Cd(1)-S(1)

2.7557(8) 87.70(7) 88.99(7) 180.00(1)

2.193(4) 2.216(4) 110.82(14) 104.09(14)

Cd(datrz)I (5) Cd(1)-N(1) 2.249(4) Cd(1)-I(1) 2.7046(7) N(4)-Cd(1)-N(1) 102.08(14) N(3)-Cd(1)-I(1) 119.56(11)

N(4)-Cd(1)-I(1) N(1)-Cd(1)-I(1)

111.09(10) 107.40(10)

Zn(1)-N(2) Zn(1)-N(3)#1 N(2)-Zn(1)-N(3)#1 N(2)-Zn(1)-N(1)

2.0208(19) 2.030(2) 106.68(8) 106.60(8)

Zn(dmtrz)Cl (6) Zn(1)-N(1) 2.043(2) Zn(1)-Cl 2.2089(7) N(3)#1-Zn(1)-N(1) 105.22(8) N(2)-Zn(1)-Cl(1) 112.44(6)

N(3)#1-Zn(1)-Cl(1) N(1)-Zn(1)-Cl(1)

111.92(7) 113.44(6)

Cd(1)-N(4) Cd(1)-N(13) Cd(1)-N(14) N(4)-Cd(1)-N(13) N(4)-Cd(1)-N(14) N(13)-Cd(1)-N(14) N(4)-Cd(1)-N(3) N(13)-Cd(1)-N(3) N(14)-Cd(1)-N(3) N(4)-Cd(1)-N(17) N(13)-Cd(1)-N(17)

2.297(4) 2.308(4) 2.329(3) 93.88(14) 92.13(13) 170.33(12) 174.38(14) 91.41(13) 82.89(11) 89.95(19) 99.70(17)

Cd3(dmatrz)4(N3)6 (7) Cd(1)-N(3) 2.348(3) Cd(1)-N(17) 2.386(4) Cd(1)-N(8) 2.407(3) N(14)-Cd(1)-N(17) 87.86(16) N(3)-Cd(1)-N(17) 87.27(16) N(4)-Cd(1)-N(8) 91.94(15) N(13)-Cd(1)-N(8) 91.36(12) N(14)-Cd(1)-N(8) 80.87(11) N(3)-Cd(1)-N(8) 89.85(11) N(17)-Cd(1)-N(8) 168.64(16) N(14)-Cd(2)-N(14)#1 180.00(12)

Cd(2)-N(14) Cd(2)-N(7) Cd(2)-N(1) N(14)-Cd(2)-N(7) N(14)#1-Cd(2)-N(7) N(7)-Cd(2)-N(7)#1 N(14)-Cd(2)-N(1) N(14)#1-Cd(2)-N(1) N(7)-Cd(2)-N(1) N(7)#1-Cd(2)-N(1) N(1)-Cd(2)-N(1)#1

2.300(3) 2.364(3) 2.383(3) 83.53(11) 96.47(11) 180.00(12) 96.31(11) 83.69(11) 89.99(11) 90.01(11) 180.0(1)

Zn(1)-N(4) Zn(1)-N(5) Zn(1)-N(1) N(4)-Zn(1)-N(5) N(5)#1-Zn(1)-N(5) N(4)-Zn(1)-N(1) N(5)#1-Zn(1)-N(1) N(5)-Zn(1)-N(1) N(4)-Zn(1)-N(1)#1

2.125(7) 2.130(4) 2.172(4) 94.51(17) 90.8(2) 90.87(17) 174.54(17) 87.82(16) 90.87(17)

Zn2(trz)3Cl (8) Zn(1)-N(3) 2.242(6) Zn(2)-N(6) 1.985(6) Zn(2)-N(2) 2.005(4) N(5)#1-Zn(1)-N(1)#1 87.82(16) N(5)-Zn(1)-N(1)#1 174.54(17) N(1)-Zn(1)-N(1)#1 93.0(2) N(4)-Zn(1)-N(3) 171.9(2) N(5)-Zn(1)-N(3) 91.17(16) N(1)-Zn(1)-N(3) 83.57(16)

2.381(3) 2.403(3) 2.5435(11) 180.00(4) 88.49(9) 88.37(7) 94.37(7) 171.68(6) 98.32(7) 95.83(4) 85.69(7) 82.63(7)

Zn(2)-Cl(1)

N(6)-Zn(2)-N(2) N(6)-Zn(2)-Cl(1) N(2)-Zn(2)-Cl(1) N(2)-Zn(2)-N(2)#2

2.266(3)

113.01(16) 108.5(2) 106.07(14) 109.7(3)

a Symmetry codes: 1: #1 -x, -y, -z. 2: #1 -x + 1, -y, -z + 1. 3: #1 -x, -y, -z; #2 -x, -y + 1, -z - 1. 4: #1 -x + 1, -y + 1, -z + 1. 6: #1 -x + 1, -y + 2, -z + 1. 7: #1 -x, -y + 2, -z. 8: #1 x, -y + 1/2, z; #2 x, -y - 1/2, z.

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Figure 1. ORTEP diagram showing the coordination environments for (a) the binuclear structure of complex 1 and (b) three-dimensional supramolecular structure generated by four types (I-IV) of hydrogen bonds. Hydrogen bond, dotted line. Hydrogen atoms are omitted for clarity.

Figure 2. ORTEP diagram showing the coordination environments for (a) the trinuclear structure of complex 2 and (b) the three-dimensional supramolecular structure generated by hydrogen bonds. Hydrogen bond, dotted line. Hydrogen atoms are omitted for clarity.

Figure 3. (a) Trinuclear cadmium unit and (b) 1D chain structure in 3. Color scheme: Cd, orange; Cl, green; N, blue; C, white. Hydrogen atoms are omitted for clarity.

a 1D chain (Figure 3b). Furthermore, the adjacent chains are connected together through weak hydrogen-bonding interactions (N(8)‚‚‚Cl(2)#1 ) 3.403(3) Å, #1 ) x, y, z + 1) to form a 3D supramolecular network (see Figure S1 of the Supporting Information). Compared with the common 1D triazole-metal chains based on mononuclear or binuclear bridging units, such a structural feature in 3 is novel. Cd(atrz)2(SCN)2 (4): A 1D Chain Based on a Mononuclear Core. To investigate the influence of the anion on the molecular construction, we added SCN- to the reaction system.

This anion is a versatile ligand with two donor atoms, which gives rise to linkage isomers or polymers and forms a variety of different coordination modes in coordination polymers. As shown in Figure 4a, complex 4 does not present a highdimensional network based on polynuclear clusters as expected, but instead presents a 1D chain constructed by mononuclear unit. Each Cd(II) ion coordinates to two triazole nitrogen atoms of two atrz ligands, two nitrogen atoms of SCN-, and two sulfur atoms of another two SCN -. The neighboring cadmium(II) ions are bridged by double µ1,3-SCN - ligands to form an eight-

Construction of Cd/Zn(II)-1,2,4-Triazolates

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Figure 4. (a) One-dimensional chain and (b) 3D supramolecular structure linked by weak hydrogen bonding in 4. Color scheme: Cd, orange; S, yellow; N, blue; C, white. Hydrogen bond, dotted line. Hydrogen atoms are omitted for clarity.

numbered Cd(SCN)2Cd circuit unit with a Cd‚‚‚Cd distance of 5.730(1) Å. The Cd(SCN)2Cd units construct an infinite polymeric chain and the organic ligand acts as a monodentate ligand coordinated via its N1 atom. It is interesting that all cadmium atoms and atrz ligands are completely coplanar. Weak nonclassic hydrogen bonds (N-H‚‚‚S, 3.596(4) Å) exist between amino groups and sulfur atoms of SCN- from two neighboring 1D chains, which further assemble 1D chains to form a 3D supramolecular structure (Figure 4b). In the FT-IR spectrum of compound 4, the single strong peak at 2100 cm-1 can be assigned to the µ1,3 thiocyanate ligand, which is in agreement with the X-ray crystal result. Cd(datrz)I (5) and Zn(dmtrz)Cl (6): Two 2D Layers Based on a Binuclear Unit. Complex 5 consists of one datrz ligand, one Cd(II) ion, and one iodide atom in the crystallographically asymmetric independent unit. Each Cd(II) ion features a distorted tetrahedral geometry, being coordinated to three triazole nitrogen atoms (Cd-N ) 2.193(4)-2.249(4) Å) and one terminal I- (Cd-I ) 2.7046(7) Å). Unlike complexes 1-4, each datrz ligand adopting the µ1,2,4-bridging mode is connected to three Cd(II) ions to generate a 2D layer structure (Figure 5a) of 5. All the I- anions locate symmetrically on the two sides of the 2D sheet. This sheet contains six-numbered circuits (Cd2N4) and 16-numbered circuits (Cd4N8C4). The Cd‚‚‚Cd distance in the Cd2N4 rings is 3.890(2) Å. Just like compound 2, the cavity of each Cd4N8C4 ring is filled with four amino groups from datrz ligands. The 2D layer structure of 5 can be rationalized as a binodal (4.82)Cd(4.82)datrz topological network (Figure 5b) when Cd and datrz are regarded as two kinds of three-connected nodes. If the dinuclear [Cd2(datrz)2] subunits are further simplified as a square-planar four-connected node, 5 has a much simpler (4, 4) topological network (Figure 5b). A significant structural feature of 5 is that the adjacent layers are stacked in an ABAB sequence to form a 3D inorganic-organic hybrid supramolecular framework by interlayer N-H‚‚‚I weak interactions (N(2)‚‚‚I(1)#1 3.786(5) Å, #1 ) x, -y + 1/2, z + 1/2), as shown in Figure 5c. It should be

pointed out that only two similar 2D layers12 based on threecoordinated Ag(I) or Cu(I) atoms and unsubstituted 1,2,4-triazole ligand have been reported to date; compound 5 is the first example and contains 1,2,4-triazole derivatives. Moreover, the existence of four-coordinated Cd(II) atoms destroys the interesting π‚‚‚π, M‚‚‚π, and M‚‚‚M interactions described in the two reported examples. 12 When Zn(OAc)2, dmtrz, and KCl are used instead in our experiments, compound 6 was obtained with an isomorphous structure of 5 (see Figure S2 of the Supporting Information). Cd3(dmatrz)4(N3)6 (7): A 2D Layer Based on a Trinuclear Unit. Compared with 1,2,4-triazole complexes containing SCNanions, for example, with N3- bridging ions is rare, even though the linking fashions of these two anions are very similar. Another substituted 1,2,4-triazole ligand, dmatrz, was chose to react with cadmium salts and N3- ions; 7 was obtained. Complex 7 is constructed from the basic subunits, which is composed of trinuclear cadmium cations bridged by two triazole ligands and one azido ion, linked via the other azido ligands to form a 2D polymer. The basic linear trinuclear subunit is depicted in Figure 6a, which is similar to that in compound 3, except that Cl- is instead by N3-. The central Cd(II) atom is surrounded by four µ1,2-triazole ligands and two azido ions. The octahedral terminal Cd(II) ions are bridged by the N3- anions via the µ1,1-linking mode. The bridging angle Cd-N-Cd is 109.87(1)°, and the Cd‚‚‚Cd separation is 3.789(5) Å. In 7, each trinuclear subunit is connected by four other units through µ1,3-N3- ligands, resulting in a 2D network along the c axis direction (Figure 6b). This 2D layer structure of 7 presents a (4,4) topology when the coordination trimers are regarded as four connected nodes. It should be pointed out that the Cd‚‚‚Cd distance is 3.789(5) Å through µ1,2-triazole ligands, which is much shorter than those through µ1,3-SCN- in 4 (5.730(1) Å) or µ1,3-N3- in 6 (6.146(2) Å). A striking structure feature of 7 is that three kinds of coordinated fashions of N3- are found in the same complex: µ1,1-bridging N3-, µ1,3-bridging N3-, and terminal N3-. The N-N distances in the N3- anions range from 1.142(6) to

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Figure 5. (a) View of the 2D layer structure of 5 along the a axis direction. (b) Two-dimensional three-connected (4.82)Cd(4.82)datrz topological net (right) and simplified (4,4) network (left). (c) Packing diagram of 5 with hydrogen bonds indicated by dashed lines. Color scheme: Cd, orange; I, purple; N, blue; C, white. Hydrogen atoms are omitted for clarity.

1.191(5) Å. The µ1,1-bridging N3- bridged two Cd(II) ions to form trinuclear subunits, and µ1,3-bridging N3- ligands bridged trinuclear units to generate the 2D framework. To the best of our knowledge, only a trinuclear cluster and one 1D chain 13 have been obtained using N3- ion as the second bridging ligand in the coordination chemistry of a 1,2,4-triazole; complex 7 is the first 2D example with azido as linkers. It is interesting that this 2D layer presents a wave shape along the b axis direction. The wavelength is ca. 15 Å and the height of the wave is ca. 6 Å. Weak nonclassic hydrogen bonding N-H‚‚‚N exists between amino groups and nitrogen atoms of terminal azido groups from two neighboring 2D layers, which further assemble 2D layers to form a 3D supramolecular architecture (Figure 6c). Zn2(trz)3Cl (8): A 3D Framework Based on a Mononuclear Unit. When nonsubstituted 1,2,4-triazole is used, complex 8 presents an interesting three-dimensional framework with a hexagonal profile along the bc plane. Two distinct Zn(II) ions exist in the structure. Zn1 is coordinated to six N1 or N2 atoms from six different trz ligands to form a [ZnN6] octahedral geometry (Zn-N ) 2.125(7)-2.242(6) Å). The Zn1 atoms link to each other via the µ1,2-bidging mode to generate a [Zn(trz)3]nnchain running along the a axis direction (Figure 7a). The Zn1‚‚‚Zn1 distance is 3.796(1) Å. This chain is similar to the {Fe(Htrz)2(trz)}nn- of [FeII(Htrz)2(trz)](BF4), whose structure

Figure 6. (a) Trinuclear fundamental unit in 7. (b) View of the 2D layer structure along the c axis direction and (4, 4) topology indicated by yellow color. (c) Three-dimensional supramolecular structure formed by 2D wavy sheets and hydrogen bonds. Color scheme: Cd, orange; N, blue; C, white. Hydrogen bond, red dashed lines. Hydrogen atoms are omitted for clarity.

was deduced from extended X-ray absorption fine structure data.14 Each Zn2 atom bridges three adjacent [Zn(trz)3]nn- chains via three N4 atoms to form the three-dimensional structure (Figure 7b) of 8 (Zn-N ) 1.985(6)-2.005(4) Å). A terminal chloride atom completes the distorted tetrahedral geometry of Zn2 atom (Zn-Cl ) 2.266(3) Å). It should be noted that although a cobalt(II) triazolate magnet15 reported by Zubieta has a structure similar to that of compound 8, no topological analysis was carried out on this novel 3D net. For reasons of classifying the net, we define the trz ligand as a single point; it can then be considered as a three-connected node. Thus, there are three kinds of nodes in the structure of 1: a six-connected node for Zn1, a three-connected node for Zn2, and a threeconnected node for trz anion (Figure 7c). There are unique four-, six-, eight-, and twelve-membered circuits through the nodes in 8. For the six-connected node, 36 sets of links are contained

Construction of Cd/Zn(II)-1,2,4-Triazolates

Crystal Growth & Design, Vol. 6, No. 9, 2006 2133

Figure 7. (a) One-dimensional chain generated by Zn1 atoms running along the a axis direction in 8. (b) View of the 3D network along the b axis direction showing [Zn(trz)3]nn- chains linked by Zn2 atoms. (c) Perspective (top) and simplified (bottom) view of the six-connected Zn1 node (right), three-connected Zn2 node (middle) and three-connected trz node (left). (d) Topological representation of 3D net.

in six four-membered circuits, six eight-membered circuits, and 24 twelve-membered circuits (see the Supporting Information, Figure S3). So the six-connected Zn1 node has the Schla¨fli symbol (46861224). For the three-connected Zn2 node, 60 sets of links are contained in six eight-membered circuits and 54 twelve-membered circuits (see the Supporting Information, Figure S4); therefore, the Zn2 node has the Schla¨fli symbol (861254). For the three-connected trz node, 42 sets of links are contained in two four-membered circuits, four eight-membered

circuits, and 36 twelve-membered circuits (see the Supporting Information, Figure S5); so the trz node has the symbol (42841236). The molar ratio of these three kinds of nonequivalent nodes is 1:1:3 (Zn1:Zn2:trz); thus, the 3D (6,3,3)-connected net (Figure 7d) of 8 can be symbolized as (46861224)(861254)(42841236)3. This framework topology, to the best of our knowledge, is completely new within the coordination polymer chemistry. On the other hand, according to the concept of rod secondary building units in the design and synthesis of metal-

2134 Crystal Growth & Design, Vol. 6, No. 9, 2006

organic frameworks (MOFs),16 this novel 3D net can also be considered as being constructed from 1D rod-shaped [Zn(1)(trz)3]building blocks and the three-connected Zn(2) node (see the Supporting Information, Figure S6). In our opinion, the interesting bridging modes of the 1,2,4-triazole ligand are the key factor in generating this interesting 3D net. Moreover, this example indicates again that topological analysis is a useful tool for the description and comparison of networks in crystal engineering, especially for those high-connected architectures.17 Effects of Substituents and Anions. Studies have shown that 1,2,4-triazole derivatives and transition metals easily formed polynuclear structures bridging through N1 and N2 atoms.4 Usually, in this N1, N2 bridging mode, a second or a third bridging ligand is needed to ease the effect of the repulsion of two metal ions that are brought close together at a distance of about 4 Å by triazole ligands 4a. The structures of complexes 1-8 (Scheme S1) clearly show that the substituents on the 1,2,4triazole ring and anions (or the second bridging ligands) are critical in the construction of molecular architecture of metaltriazole complexes. For 1-3, the anions all are Cl-, and the molecular structures vary from binuclear cluster and linear trinuclear cluster to 1D chain with a gradually decreasing bulk of substituents on the 3 and 5 positions of the 1,2,4-triazole ring. The 1D chain structure of 4 exhibits a rare N1-triazole coordinated mode due to the longer doubly bridged SCN- anions instead of Cl- ions. In compounds 5 and 6, although the groups on the 3 and 5 positions (NH2 or CH3) are larger than those of 3 (H), the 4-position unoccupied datrz and dmtrz ligands take the µ1,2,4-bridging fashion to generate 2D grids. The terminal coordinated halide ions obstruct the construction of a 3D network. When a nonsubstituted 1,2,4-triazole ligand is used instead, 8 presents a three-dimensional (6,3,3)-connected framework. Therefore, it can be seen that substituents and anions play a controlling role over the molecular structure. The results suggest that selection of appropriate substituted groups and anions would be an ideal way to construct novel metaltriazolate coordination polymers. Thermal Properties. The TG/DTA of compounds 1-8 (see the Supporting Information, Figure S8) were performed on crystalline samples under a nitrogen atmosphere from 40 to 1000 °C. The thermogravimetric analysis results show that these coordination frameworks exhibit high thermal stability. The TG curve of 1 indicated it was stable up to ca. 275 °C. Two stages of weight loss are observed in the temperature range 275-800 °C. The first weight loss in the range 275-375 °C (17.97%) is in good agreement with the calculated value (17.44%) for the decomposition of chlorine. Over the range 375-800 °C, the weight loss (54.02%) should correspond to the loss of organic ligands (calcd 54.91%). The TG curves of 2 and 3 are very alike, which is consistent with their similar structure skeleton. No weight losses were observed for either compound up to 300 °C; above 300 °C, two steps of weight losses occurred that ended at about 700 °C for 2 and 750 °C for 3. The first weight losses observed in the temperature range 300-425 °C were due to the decomposition of organic components (exp. 54.33%, calcd 55.04% for 2; exp. 37.86%, calcd 37.95% for 3). The second weight losses, 45.31% for 2 and 62.02% for 3, are in good agreement with the loss of CdCl2 (calcd 44.96% for 2 and 63.05% for 3). In our opinion, the nearly complete weight loss of compounds 2 and 3 is due to the sublimation of newly formed CdCl2 compounds. For compound 4, the two-step weight loss in the temperature range 170-750 °C should correspond to the decomposition of organic components and SCN-, respectively. The whole weight

Zhai et al.

Figure 8. Emission spectra of complexes 1-8 and 2py-trz ligand in the solid state at room temperature. All complexes are excited at 340 ( 5 nm.

loss (69.11%) is in accordance with the expected value (71.68%). No weight loss was observed for compound 6 up to 475 °C; above 475 °C, significant weight loss occurred that ended at about 850 °C, indicating complete decomposition of organic ligands and chlorine. This conclusion is supported by the value of the whole weight loss (exp. 67.45%, calcd 66.79%). The TG curve of compound 7 first exhibits a sharp weight loss in the temperature range 275-450 °C, corresponding to the weight loss of four dmatrz ligands (exp. 43.84%, calcd 44.22%). The azido components decomposed in the range 450-700 °C. The whole weight loss, 68.39%, is in good agreement with the calculated value (68.51%). The TG curve of compound 8 showed that it could be stable up to about 408 °C. Further, organic ligands and chlorine were decomposed in the range 408-905 °C (exp. 65.05%, calcd 64.69%). Luminescence Properties. Upon excitation of solid samples of 1-8 at λ ) 340 ( 5 nm, intense bonds in the emission spectra are observed at 385 nm for 1 and 410 nm for 2-8 (Figure 8). To understand more thoroughly the nature of the emission band, we also investigated the luminescence of all the 1,2,4-triazole derivative ligands used in the solid state at room temperature. All the organic ligands except for 2py-trz are nearly nonfluorescent in the range 400-800 nm for excitation wavelengths between 250 and 450 nm. The rigid 2py-trz ligand exhibits strong emission with a maximum at λ ) 421 nm upon excitation at λ ) 357 nm. In our opinion, the emission of complex 1 is neither metal-to-ligand charge transfer (MLCT) nor ligand-to-metal charge transfer (LMCT) in nature, and may be assigned to intraligand fluorescence emission because it is similar to that for the free 2py-trz ligand. For compounds 2-8, the free organic ligands display no luminescence. In these complexes, the highest occupied molecular orbitals (HOMOs) are presumably associated with the π-bonding orbitals from aromatic 1,2,4-triazole rings, whereas the lower unoccupied molecular orbitals (LUMOs) are associated mainly with the Cd/ Zn-X (X ) Cl-, I-, SCN-, and N3-) δ*-antibonding orbitals, localized more on the metal centers. Thus, the origin of the emission might be attributed to the ligand-to-metal charge transfer (LMCT).18 The luminescence properties of these metalorganic complexes indicate that they may be excellent candidates for potential photoactive materials.

Construction of Cd/Zn(II)-1,2,4-Triazolates

Conclusions We have constructed a series of coordination complexes based on mono-, bi-, and trinuclear Cd/Zn(II)-1,2,4-triazolate subunits with a variety of zero-, one-, two-, and three-dimensional frameworks. Compounds 3, 5, 6, and 7 all are coordination polymers based on polynuclear clusters; 7 is the first example in which three kinds of coordination modes of azido are observed in the same structure. Three-dimensional supramolecular structures are generated by weak hydrogen bondings in complexes 1-7. Compound 8 shows a 3D framework and has a novel Schla¨fli symbol (46861224)(861254)(42841236)3. The isolation of these complexes demonstrates again that the substituents on the triazole ring and the anions are clearly critical in determining the molecular architecture of metal-1,2,4triazolate complexes. All the complexes exhibit a strong blue fluorescence property in the solid state at room temperature. Acknowledgment. This work was supported by the 973 program of the MOST (001CB108906), the National Science Foundation of China (20521101, 20425313, 90206040, 20333070, and 20303021), the Natural Science Foundation of Fujian Province (2005HZ01-1), and the Chinese Academy of Sciences. Supporting Information Available: X-ray crystallographic files in cif format, additional plots of the structures, PXRD and thermogravimetric analysis results. This material is available free of charge via the Internet at http://pubs.acs.org.

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