Structure Variation of Mercury(II) Halide Complexes with Different

Figure 7 Emission spectra of the compounds 1 (red) and 5 (black) with λex = 354 nm .... (e) Blake, A. J.; Brooks, N. R.; Champness, N. R.; Crew, M.; ...
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Structure Variation of Mercury(II) Halide Complexes with Different Imidazole-Containing Ligands Wang,†

Lv,†

Okamura,‡

Xiao-Feng Yang Taka-aki Wei-Yin Sun,*,† and Norikazu Ueyama‡

Hiroyuki

Kawaguchi,§

Gang

Wu,†

CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 6 1125-1133

Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing UniVersity, Nanjing 210093, China, Department of Macromolecular Science, Graduate School of Science, Osaka UniVersity, Toyonaka, Osaka 560-0043, Japan, and Coordination Chemistry Laboratories, Institute for Molecular Science, Okazaki, Aichi 444-8585, Japan ReceiVed NoVember 17, 2006; ReVised Manuscript ReceiVed March 24, 2007

ABSTRACT: A series of coordination complexes with different structures [Hg(iimb)I2]‚0.5acetone (1), [Hg(bib)Br2]‚0.5THF (2), [Hg(bib)I2] (3), [Hg3(tib)2I6]‚2DMF (4), [Hg3(timpt)2I6]‚4H2O (5), [Hg2(titmb)Br4] (6), and [Hg2(titmb)Cl4] (7) were synthesized by reactions of mercury(II) halides with the corresponding imidazole-containing bidentate or tripodal ligands, namely, 1-(1-imidazolyl)4-(imidazol-1-ylmethyl)benzene (iimb), 1-bromo-3,5-bis(imidazol-1-ylmethyl)benzene (bib), 1,3,5-tris(1-imidazolyl)benzene (tib), 2,4,6-tris[4-(imidazol-1-ylmethyl)phenyl]-1,3,5-triazine (timpt), and 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb), respectively. The structures of the complexes were determined by single-crystal X-ray diffraction analyses, and the results revealed that 1, 2, and 4-7 are one-dimensional (1D) chain coordination polymers with different shapes. In the case of 3, two metal atoms and two bib ligands form M2L2 binuclear rings, which are further connected by weak Hg‚‚‚I interactions to form an infinite 1D chain. The different structures of the complexes showed the predominant influence of halides and organic ligands. In addition, the weak interactions such as Hg-X‚‚‚Hg (X ) I or Br), I‚‚‚I interactions also play an important role in the formation of supramolecular architectures, for instance, to link low-dimensional entities to high-dimensional frameworks. Polycatenation of the 1D ladders was observed in 1 to give a three-dimensional architecture. The photoluminescence properties of the synthesized mercury(II) complexes were investigated in the solid state at room temperature. Introduction Crystal engineering of self-assembled coordination polymers containing metal ions and organic bridging ligands is of great current interest not only because of their varied structures but also because of their potential properties such as magnetism, nonlinear optics, electronics, catalysis, molecular recognition, etc.1,2 By introducing specially designed ligands and carefully selected metal ions with definite coordination geometry, the specific coordination polymers can be prepared through selfassembly reactions.3-5 Many efforts have been devoted to the selection and design of suitable ligands, such as adjusting their flexibility and varying the coordination modes.6 For example, by the reactions of the flexible bridging ligand 1-(1-imidazolyl)4-(imidazol-1-ylmethyl)benzene (iimb) (Scheme 1) with copper(II) bromide and cobalt(II) thiocyanate, double-stranded chains were generated, while the reactions of iimb with copper(II) sulfate and cobalt(II) sulfate gave two-dimensional (2D) polycatenated architectures.7 Another flexible imidazole-containing bidentate ligand 1-bromo-3,5-bis(imidazol-1-ylmethyl)benzene (bib) was reacted with transition metal salts such as Ag(I), Zn(II), and Mn(II) to give a series of coordination frameworks.8 In addition, a series of imidazole-containing tripodal ligands, e.g., 1,3,5-tris(1-imidazolyl)benzene (tib), 1,3,5-tris(imidazol1-ylmethyl)-2,4,6-trimethylbenzene (titmb), 2,4,6-tris[4-(imidazol-1-ylmethyl)phenyl]-1,3,5-triazine (timpt) (Scheme 1), were designed in our laboratory and used to investigate the influence of bridging ligand on formation of supramolecular architectures, and they were assembled to result in a broad range of structures * To whom correspondence should be addressed. Telephone: +86-2583593485. Fax: +86-25-83314502. E-mail: [email protected]. † Nanjing University. ‡ Osaka University. § Institute for Molecular Science.

including cagelike, one-dimensional (1D) tubelike, 2D network, three-dimensional (3D) noninterpenetrating or interpenetrating frameworks.9-13 It is clear that the bridging ligands and metal ions play important roles in the formation of such architectures. In contrast, reports on mercury(II) coordination polymers are disproportionately rare compared to those of familiar metal ions such as Ag(I), Zn(II), Cd(II), etc.14 To further investigate the self-assembly reactions of mercury(II) salts with bridging ligands on the formation of coordination polymers, two bidentate (iimb and bib) and three tripodal ligands (tib, timpt, and titmb) were used to generate coordination polymers with interesting structures. Herein, we report the crystal structure of seven novel complexes [Hg(iimb)I2]‚0.5acetone (1), [Hg(bib)Br2]‚0.5THF (2), [Hg(bib)I2] (3), [Hg3(tib)2I6]‚2DMF (4), [Hg3(timpt)2I6]‚ 4H2O (5), [Hg2(titmb)Br4] (6), and [Hg2(titmb)Cl4] (7), obtained by self-assembly reactions of mercury(II) halides with corresponding ligands respectively, and they were characterized by FTIR, single-crystal X-ray diffraction analysis, and elemental analysis. The luminescent properties of the complexes were investigated in the solid state at room temperature. The results indicate that the nature of the ligands and halides have great influence on the formation and structure of metal-organic frameworks. Experimental Section All commercially available chemicals are of reagent grade and used as received without further purification. All ligands were prepared by the method reported previously.7-13 C, H, and N analyses were made on a Perkin-Elmer 240C elemental analyzer at the analysis center of Nanjing University. Infrared (IR) spectra were recorded on a Bruker Vector22 FT-IR spectrophotometer by using KBr discs. The luminescent spectra for the powdered solid samples were recorded at room temperature on an Aminco Bowman Series 2 spectrofluorometer with a xenon arc lamp as the light source. In the measurements of emission

10.1021/cg060814c CCC: $37.00 © 2007 American Chemical Society Published on Web 05/17/2007

1126 Crystal Growth & Design, Vol. 7, No. 6, 2007 Scheme 1.

Wang et al.

Schematic Drawing for bib, iimb, tib, timpb, and titmb

and excitation spectra, the pass width is 5.0 nm. All the measurements were carried out under the same experiment conditions. Synthesis of [Hg(iimb)I2]‚0.5acetone (1). A methanol solution (10 mL) of iimb (22.4 mg, 0.1 mmol) was added dropwise to HgI2 (45.5 mg, 0.1 mmol) in THF (10 mL) to give a clear solution. It was stirred for ca. 15 min at room temperature. Colorless crystals were obtained by slow diffusion of acetone into the above solution after 5 days in ca. 60% yield. Anal. Calc. for C14.5H15N4O0.5I2Hg: C, 24.61; H, 2.14; N, 7.92%. Found: C, 24.50; H, 2.17; N, 7.83%. IR(KBr, cm-1): 3119m, 1611m, 1523s, 1307m, 1236m, 818w, 653w. Synthesis of [Hg(bib)Br2]‚0.5THF (2). A methanol solution (10 mL) of bib (31.7 mg, 0.1 mmol) was added dropwise to HgBr2 (36.1 mg, 0.1 mmol) in THF (10 mL) and stirred for ca. 15 min at room temperature. After filtration, the filtrate was allowed to stand for two weeks upon slow evaporation of the solvent to give colorless crystals in ca. 65% yield. Anal. Calc. for C16H17N4O0.5Br3Hg: C, 26.93; H, 2.40; N, 7.55%. Found: C, 26.96; H, 2.48; N, 7.36%. IR (KBr, cm-1): 3117m, 1577m, 1517s, 1243m, 1105s, 838w, 740s, 648m. Synthesis of [Hg(bib)I2] (3). The title complex was prepared by the same procedure used in preparation of 2 using bib (31.7 mg, 0.1 mmol) and HgI2 (45.5 mg, 0.1 mmol). Yield: ca. 57%. Anal. Calc. for C14H13N4BrI2Hg: C, 21.79; H, 1.70; N, 7.26%. Found: C, 22.01; H, 1.56; N, 7.15%. IR(KBr, cm-1): 3111m, 1576m, 1518s, 1239m, 1109s, 839m, 752s, 649m. Synthesis of [Hg3(tib)2I6]‚2DMF (4). A methanol solution (5 mL) of tib (27.1 mg, 0.1 mmol) was added dropwise to HgI2 (45.5 mg, 0.1

mmol) in CH3CN (5 mL) to give white precipitate. The reaction mixture was stirred for 15 min at room temperature, and then DMF (10 mL) was added to dissolve the precipitate. Colorless crystals suitable for X-ray diffraction were obtained upon slow evaporation of the solvent after two weeks in 69% yield. Anal. Calc. for C36H38N14O2I6Hg3: C, 20.97; H, 1.86; N, 9.51%. Found: C, 20.83; H, 2.01; N, 9.48%. IR (KBr, cm-1): 3111m, 1663s, 1506s, 1245m, 823w, 681w. Synthesis of [Hg3(timpt)2I6]‚4H2O (5). A buffer solution (5 mL) of methanol and DMF (1:1) was carefully layered over a DMF solution (2 mL) of HgI2 (45.5 mg, 0.1 mmol). Then a solution of timpt (55.0 mg, 0.1 mmol) in methanol (2 mL) was layered over the buffer layer. Colorless crystals were obtained after one week in 43% yield. Anal. Calc. for C66H56N18OI6Hg3: C, 31.28; H, 2.46; N, 9.95%. Found: C, 31.39; H, 2.49; N, 9.99%. IR (KBr, cm-1): 3112w, 1519s, 1369s, 1231m, 1107s, 813w, 663w. Synthesis of [Hg2(titmb)Br4] (6). A methanol solution (10 mL) of titmb (36.0 mg, 0.1 mmol) was added dropwise to HgBr2 (36.1 mg, 0.1 mmol) in DMF (10 mL) to give a clear solution. It was stirred for ca. 15 min at room temperature. Colorless crystals for X-ray diffraction were obtained upon slow evaporation of the solvent after two weeks in ca. 70% yield. Anal. Calc. for C21H24N6Br4Hg2: C, 23.33; H, 2.24; N, 7.77%. Found: C, 23.38; H, 2.14; N, 7.82%. IR (KBr, cm-1): 3107s, 1623m, 1513s, 1231s, 1092s, 829m, 641m. Synthesis of [Hg2(titmb)Cl4] (7). The title complex was obtained by the same procedure as that for preparation of 5, except HgCl2 (27.2 mg, 0.1 mmol) and titmb (36.0 mg, 0.1 mmol), instead of HgI2 and

Mercury(II) Halide Complexes

Crystal Growth & Design, Vol. 7, No. 6, 2007 1127 Table 1. Crystallographic Data for Complexes 1-7

complex

1

2

3

4

5

6

7

empirical formula

C14.5H15I2HgN4O0.5 707.70 monoclinic C2/c 25.22(2) 10.017(7) 15.757(11) 90 103.794(11) 90 3865.3(47) 8 2.432 11.185 173 0.7107 0.044 0.058/0.209

C16H17Br3HgN4O0.5 713.64 monoclinic P2/c 12.930(5) 9.969(4) 15.716(6) 90 90.365(8) 90 2025.8(14) 4 2.340 13.562 173 0.7107 0.047 0.038/0.093

C14H13BrI2HgN4 771.59 triclinic Pıj 8.419(3) 9.236(3) 12.274(4) 102.489(3) 95.987(5) 91.462(3) 925.6(5) 2 2.768 13.839 173 0.7107 0.043 0.037/0.125

C36H38I6Hg3N14O2 2061.97 monoclinic C2/c 21.676(17) 15.860(11) 18.097(12) 90.00 121.50(2) 90.00 5304(7) 4 2.582 12.198 200 0.71075 0.0558 0.0340/0.0366

C66H62I6Hg3N18O4 2534.51 triclinic Pıj 8.913(3) 13.306(5) 37.689(11) 80.808(12) 87.933(12) 72.027(13) 4197(3) 2 2.006 7.733 200 0.71075 0.0912 0.0765/0.1991

C21H24Br4Hg2N6 1081.28 monoclinic P21/c 11.585(5) 11.901(3) 19.438(5) 90.00 93.407(14) 90.00 2675.4(15) 4 2.684 17.459 200 0.71075 0.0903 0.0481/0.1021

C21H24Cl4Hg2N6 903.44 monoclinic C2/c 28.808(12) 11.585(4) 19.238(9) 90.00 127.723(12) 90.00 5078(4) 8 2.363 12.521 200 0.71075 0.1041 0.0871/0.1803

formula weight crystal system space group a/Å b/Å c/Å R/° β/° γ/° V/Å3 Z Dcalc/g cm-3 µ/mm-1 T/K λ, Å Rint Ra/wRb a

R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) |∑w(|Fo|2 - |Fc|2)|/∑|w(Fo)2|1/2, where w ) 1/[σ2(Fo2) + (aP)2 + bP]. P ) (Fo2 + 2Fc2)/3.

timpt, were used. Yield: ca. 40%. Anal. Calc. for C21H24N6Cl4Hg2: C, 27.92; H, 2.68; N, 9.30%. Found: C, 27.93; H, 2.58; N, 9.37%. IR (KBr, cm-1): 3102m, 1630m, 1514s, 1232s, 1092s, 828m, 642m. Crystallography. The data collection was carried out on a Rigaku Saturn (or Mercury) CCD area detector at 173 K for the complexes 1-3 and on a Rigaku RAXIS-RAPID Imaging Plate diffractometer at 200 K for complexes 4-7 using graphite-monochromated Mo-KR radiation, respectively. The structures were solved by direct method with SHELXS-9715 and expanded using Fourier techniques.16 All nonhydrogen atoms were refined anisotropically by the full-matrix leastsquares method on F2. The hydrogen atoms were generated geometrically. All calculations were carried out using the CrystalStructure crystallographic software package (for 1-3) and the teXsan crystallographic software package of Molecular Structure Corporation (for 4-7).17 One HgI2 and two carbon atoms of one imidazole goup in 5 disordered into two positions with the site occupancy factors (sofs) of 0.518(10) (for atoms Hg4, I7, I8, C39B, and C40B) and 0.482(10) (for atoms Hg3, I5, I6, C39, and C40), respectively. A water molecule in 5 also disordered into two positions with sofs of 0.54(4) and 0.46(4). Details of the crystal parameters, data collection, and refinement for complexes 1-7 are summarized in Table 1. Selected bond lengths and angles for complexes 1-7 are listed in Table 2. Hydrogen-bonding data of complexes 1-7 are listed in Table 3. Further details are provided in Supporting Information.

Results and Discussion Syntheses and Formation of the Complexes. To investigate the effect of structure and flexibility of organic ligands on the structure of their metal complexes, five imidazole-containing ligands were used to react with Hg(II) salts. The reaction and formation of the complexes are schematically shown in Scheme 2. On the other hand, to study the influence of halides, reactions of five ligands with HgCl2, HgBr2, and HgI2 were carried out, and complexes 1-7 were successfully isolated. The halide effect will be discussed by comparison of 2 and 3 with the same bib ligand but different halides as well as 6 and 7 with the same titmb ligand but with bromide and chloride, respectively. Description of Crystal Structures. Complex [Hg(iimb)I2]‚0.5acetone (1). The X-ray crystallographic analysis revealed that complex 1 crystallizes in the monoclinic form with space group C2/c and has an infinite 1D zigzag chain structure. The crystal structure of 1 with the coordination environment of Hg(II) atom is depicted in Figure 1a. It can be clearly seen that each Hg(II) atom is in a distorted tetrahedral coordination environment with two N atoms from two different iimb ligands, and two iodide from HgI2 with Hg1-I1, Hg1-I2, Hg1-N1, and Hg1-N3A bond distances of 2.690(2), 2.666(2), 2.39(1),

and 2.351 Å, respectively. The bond angles of I2-Hg1-I1, I-Hg1-N and N1-Hg1-N3A are in the range of 97.6143.79(4)° (Table 2), which are similar to those observed in the reported Hg(II) complexes with N and I donors.18,19 The ligand iimb has a “V” shape and links two Hg(II) atoms using its two imidazole groups to give a 1D zigzag chain structure (Figure 1a,b). An interesting feature of complex 1 is that there are I‚‚‚I interactions involved in the crystal lattice. As reported previously, an I-I distance of less than 3.96 Å is considered to have I‚‚‚I interactions.20 The distance between the two I atoms from two adjacent 1D chains is 3.90 Å in 1. Directional interactions formed between the halogens are specific attractive force induced and have been used intensively in systematic crystal engineering.21 In compound 1, the infinite 1D chains are joined together by such I‚‚‚I interactions to lead to the formation of an infinite 1D ladder. As illustrated in Figure 1b, each Hg(II) atom acts as a T-type three-connected center in the ladder (the another I atom serves as a terminal ligand), and each ladder-like chain contains an infinite number of equivalent hexagons composed of two ladder “rungs” of I-I and segments of two ladder “uprights” of the “V” shaped iimb ligands. It is noteworthy that the hexagon is large enough to allow other hexagons to pass through it; namely, the 1D ladders polycatenate to form a 3D framework structure as schematically shown in Figure 1c. There are a few reported examples of such kinds of polycatenated ladders that give 3D architectures (i.e., from 1D to 3D), e.g., [M2(bpethy)3(NO3)4] [M ) Zn(II) or Co(II), bpethy ) 1,2-bis(4-pyridyl)ethyne], [Co2(bpethe)3(NO3)4] [bpethe ) 1,2-(4-pyridyl)ethene] and [Cu2(ip)(bpy)2] (ip ) isophthalate, bpy ) 4,4′-bipyridine).22 Different from these reported polycatenated 1D motifs in which the organic ligands acting as ladder rungs, 1 is, to the best of our knowledge, the first example of a 1D polycatenated coordination polymer formed by I‚‚‚I weak interactions. On the other hand, the uncoordinated acetone solvent molecules are located in the voids of 1D chains, held there by two C-H‚‚‚O hydrogen bonds with the C‚‚‚O distance of 3.205(17) and 3.40(2) Å. The hydrogen-bonding data are summarized in Table 3. Complexes [Hg(bib)Br2]‚0.5THF (2) and [Hg(bib)I2] (3). To investigate the effect of halide on the structure of Hg(II) complexes, the reactions of bib with HgBr2 and HgI2 were carried out, respectively, and complexes 2 and 3 were isolated. The X-ray crystallographic analysis showed that 2 crystallizes in the monoclinic form with space group P2/c, and the structure

1128 Crystal Growth & Design, Vol. 7, No. 6, 2007

Wang et al.

Table 2. Selected Bond Lengths [Å] and Angles [°] for 1-7a 1 Hg1-I1 Hg1-N1 I1-Hg1-I2 I2-Hg1-N1 I2-Hg1-N3#1

2.690(2) 2.39(1) 143.79(4) 99.9(2) 103.2

Hg1-I2 Hg1-N3#1 I1-Hg1-N1 I1-Hg1-N3#1 N1-Hg1-N3#1

2.66(2) 2.351 102.4(2) 101.6 97.6

2 Hg1-Br1 Hg1-N1 Br1-Hg1-Br2 Br2-Hg1-N1 Br2-Hg1-N3#2

2.5269(7) 2.270(5) 131.60(2) 102.1(1) 97.3

Hg1-Br2 Hg1-N3#2 Br1-Hg1-N1 Br1-Hg1-N3#2 N1-Hg1-N3#2

2.5697(7) 2.269 102.7(1) 109.3 114.2

3 Hg1-I1 Hg1-N2 I1-Hg1-I2 I2-Hg1-N2 I2-Hg1-N4#3

2.7004(10) 2.298(5) 125.30(1) 101.1(1) 113.2

Hg1-I2 Hg1-N4#3 I1-Hg1-N2 I1-Hg1-N4#3 N1-Hg1-N4#3

2.6969(11) 2.361 124.7(1) 101.3 83.3

4 Hg1-N12 Hg2-N32 Hg2-I2 N12-Hg1-N12 N12-Hg1-I1 N12-Hg1-I1 N52-Hg2-N32#4 I1-Hg1-I1

2.417(4) 2.353(5) 2.6523(13) 80.3(2) 105.82(11) 103.73(10) 93.61(16) 141.02(4)

Hg1-I1 Hg2-N52#4 Hg2-I3 N32-Hg2-I2 N52-Hg2-I3#4 N32-Hg2-I3 I2-Hg2-I3 N52-Hg2-I2#4

2.6596(13) 2.319(4) 2.698(2) 103.28(11) 100.41(11) 100.27(11) 135.95(3) 114.52(12)

5 Hg1-N22#5 Hg1-I2 Hg2-N112 Hg2-I3 Hg4-N132#7 Hg4-I8 N22#5-Hg1-N12 N12-Hg1-I2 N12-Hg1-I1 N112-Hg2-N122#6 N122#6-Hg2-I3 N122#6-Hg2-I4 N132#7-Hg4-I7 I7-Hg4-I8 N32-Hg4-I8

2.299(15) 2.6436(17) 2.328(14) 2.6425(16) 2.691(12) 2.632(8) 96.4(4) 102.3(3) 99.8(3) 85.6(4) 103.3(3) 100.6(3) 100.5(5) 125.6(3) 109.4(7)

Hg1-N12 Hg1-I1 Hg2-N122#6 Hg2-I4 Hg4-I7 Hg4-N32 N22#5-Hg1-I2 N22#5-Hg1-I1 I2-Hg1-I1 N112-Hg2-I3 N112-Hg2-I4 I3-Hg2-I4 N132#7-Hg4-I8 N32-Hg4-I7 N32-Hg4-N132#7

2.371(11) 2.6571(16) 2.412(12) 2.6562(15) 2.685(10) 2.256(9) 105.7(4) 104.9(4) 139.55(6) 109.6(3) 101.7(3) 141.61(5) 114.7(4) 108.8(7) 92.9(6)

Hg1-N32 Hg1-Br2#8 Hg2-Br4 Hg2-Br2 N12-Hg1-Br1 N32-Hg1-Br1 Br1-Hg1-Br2#8 N52-Hg2-Br3 Br4-Hg2-Br3 Br3-Hg2-Br2

2.170(6) 2.9482(14) 2.5042(11) 2.6748(11) 114.41(17) 91.37(17) 95.86(4) 99.83(18) 120.40(3) 115.32(4)

Table 3. Distance (Å) and Angles (deg) of Hydrogen Bonds for the Complexes 1-7a D-H‚‚‚A

distance (D‚‚‚A)

angle (D-H-A)

C1-H1‚‚‚O1 C5-H4‚‚‚O1

1 3.205(17) 3.40(2)

133 172

C10-H8‚‚‚O1#1 C14-H13‚‚‚O1#1

2 3.433(18) 3.332(14)

152 140

C13-H12‚‚‚Br1

3 3.659(7)

136

C2-H1‚‚‚O1 C6-H3‚‚‚O1#2 C53-H12‚‚‚O1#2

4 3.192(7) 3.235(9) 3.349(10)

140 132 148

C19-H8‚‚‚N1#3 C38-H25‚‚‚O2 C39B-H27‚‚‚I1#4 C138-H54‚‚‚O1

5 3.251(18) 3.23(3) 3.73(3) 3.15(3)

135 140 158 151

C11-H1‚‚‚Br4#5 C34-H13‚‚‚Br4#6 C41-H15‚‚‚N51#7 C53-H20‚‚‚Br4#8 C54-H21‚‚‚Br1#9

6 3.658(9) 3.553(9) 3.310(12) 3.724(8) 3.844(9)

145 132 131 156 163

C13-H4‚‚‚Cl2#10 C14-H5‚‚‚Cl4#11 C31-H10‚‚‚Cl2#12 C51-H17‚‚‚Cl2#13 C54-H21‚‚‚Cl2#13

7 3.63(3) 3.73(2) 3.41(2) 3.51(2) 3.46(2)

157 160 137 139 134

a Symmetry transformations are used to generate equivalent atoms: #1: 1 - x, 1 + y, 1/2 - z; #2: 1/2 - x, 3/2 - y, 1 - z; #3: 1 + x, y, z; #4: x, -1 + y, z; #5: 1 - x, 1 - y, -z; #6: x, 1/2 - y, 1/2 + z; #7: 1 - x, -1/2 + y, 1/2 - z; #8: -x, 1 - y, -z; #9: -1 + x, y, z; #10: 1 - x, y, 3/2 - z; #11: 1 - x, 1 - y, 1 - z; #12: x, 1 - y, -1/2 + z; #13: x, -y, -1/2 + z.

Scheme 2.

Schematic Drawing for Reactions and Formation of the Complexes

6 Hg1-N12 Hg1-Br1 Hg2-N52 Hg2-Br3 N12-Hg1-N32 N12-Hg1-Br2#8 N32-Hg1-Br2#8 N52-Hg2-Br4 N52-Hg2-Br2 Br4-Hg2-Br2

2.147(6) 2.6891(11) 2.261(8) 2.5849(11) 153.2(2) 91.73(18) 92.86(18) 117.41(18) 95.04(19) 106.26(4)

Hg1-N12 Hg1-Cl2 Hg2-N52#9 Hg2-Cl3 Hg-N32 N12-Hg1-Cl2 Cl2-Hg1-Cl3 Cl2-Hg1-Cl1 N32-Hg2-N52#9 N52-Hg2-Cl4 N52#9-Hg2-Cl3 N32-Hg2-Cl1#9 Cl4-Hg2-Cl1#9

2.244(12) 2.352(13) 2.168(15) 2.912(5) 2.132(13) 118.4(4) 112.0(3) 113.1(2) 155.0(5) 94.1(4) 90.1(4) 88.7(3) 90.65(17)

7 Hg1-Cl1 Hg1-Cl3 Hg2-Cl1#9 Hg2-Cl4

2.523(5) 2.507(5) 2.978(5) 2.609(6)

N12-Hg1-Cl3 N12-Hg1-Cl1 Cl3-Hg1-Cl1 N32-Hg2-Cl4 N32-Hg2-Cl3 Cl4-Hg2-Cl3 N52#9-Hg2-Cl1#9 Cl3-Hg2-Cl1#9

100.9(3) 97.7(4) 113.5(2) 110.7(4) 91.9(4) 93.23(19) 87.5(4) 175.54(17)

a Symmetry transformation used to generate equivalent atoms: #1: -1/2 + x, 1/2 + y, z; #2: x, 3 - y, -1/2 + z; #3: -1 - x, 2 - y, 1 - z; #4: x, 1 - y, 1/2 + z; #5: 1 - x, 1 - y, -z; #6: 2 - x, 2 - y, 1 - z; #7: 1 - x, 1 - y, 1 - z; #8: 1 - x, -1/2 + y, 1/2 - z; #9: 3/2 - x, y + 1/2, 3/2 - z.

of 2 is a 1D square-wave like chain. As depicted in Figure 2a, the coordination environment of Hg(II) atom in 2 is similar to that in 1 with two N and two halide atoms. The bond distances

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Figure 1. (a) Crystal structure of 1 with the coordination environment around the Hg(II) center (ellipsoids at 30% probability). (b) A view of ladder structure formed through I‚‚‚I interactions between two 1D zigzag chains of 1. The hydrogen atoms and solvent molecules are omitted for clarity. (c) A schematic drawing of polycatenated 1D polymers.

of Hg1-Br1, Hg1-Br2, Hg1-N1, Hg1-N3A are 2.5269(7), 2.5697(7), 2.270(5), 2.269 Å (Table 2), which are similar to those observed in the reported Hg(II) complexes with N and Br donor set.23 Each ligand bib with trans conformation binds two Hg(II) atoms using its two arms to give a 1D chain structure (Figure 2a), and no evident Br‚‚‚Br interactions between the 1D chains were found. The disordered THF molecules locate at the border of the chains and connect the neighboring chains through C-H‚‚‚O hydrogen bonds to generate a 3D framework (Figure 2b and Table 3). Complex 3 crystallizes in triclinic with space group P1h (Table 1), and the local coordination geometry around the Hg(II) atom in 3 (Figure 3a) is also similar to those in 1 and 2. The bond distances of Hg1-I1, Hg1-I2, Hg1-N2, and Hg1-N4A are 2.7004(10), 2.6969(11), 2.298(5), and 2.361 Å, respectively. The I-Hg-I, I-Hg-N, and N-Hg-N angles are in the range of 83.3-125.30(1)° as listed in Table 2. It is noteworthy that ligand bib connects two Hg(II) atoms to form a 24-membered M2L2 macrocyclic ring, rather than to form a 1D chain as observed in 1 and 2. Furthermore, the distance of 4.40 Å between the I atom of one M2L2 ring and the Hg atom from another M2L2 ring in 3 indicates the presence of weak Hg‚‚‚I interactions.24 Therefore, the M2L2 macrocyclic rings are further connected by weak Hg‚‚‚I interactions to form an infinite 1D chain (Figure 3b), with the Hg-Ibridging-Hg angle of 84.2°. When the bib ligand reacted with ditopic diacetato-zinc(II) acceptors, a similar M2L2-type metallocyclic ring-like complex [Zn2(bib)2(OAc)4]‚2H2O (OAc ) acetate anion) was obtained, and the rings were further connected by Br‚‚‚Br interactions to lead to the formation of 1D pseudopolyrotaxane.8a In addition, the 1D chains in 3 are further linked together by C-H‚‚‚Br interactions to produce an infinite 3D framework stucture (Figure 3c and Table 3). Complex [Hg3(tib)2I6]‚2DMF (4). In addition to the ligands with two imidazole groups as used in preparation of 1-3, ligands each with three imidazole groups were also used to react

Figure 2. (a) 1D chain structure of 2 with the atom numbering scheme (ellipsoids at 30% probability); the hydrogen atoms and solvent molecules are omitted for clarity. (b) Crystal packing diagram of complex 2 with the hydrogen bonds indicated by dashed lines.

with Hg(II) halides, and complexes 4-7 were synthesized and characterized. Complex 4 crystallizes in the monoclinic form with space group C2/c, and its asymmetric unit contains a half molecule of [Hg3(tib)2I6]‚2DMF. A perspective view of the repeated unit in 4 is shown in Figure 4a with the atom numbering scheme. The coordination geometry around the Hg(II) atom is also distorted tetrahedral with N2I2 binding set (Figure 4b). Each Hg(II) atom is coordinated by two imidazole N atoms from two individual tib ligands with bond lengths of Hg-Nav 2.36 Å and two I atoms with Hg-Iav bond lengths of 2.67 Å (Table 2). Each tib ligand in turn connects three Hg(II) atoms to give a 1D chain containing 20-membered rings with a Hg-Hg distance of 10.56 Å. Such infinite 1D chain structure is different from the previously reported Ag(I), Mn(II) complexes of tib with a 2D or 3D network structure.25 It is noticeable that the 1D chains of 4 are further linked together through C-H‚ ‚‚O interactions to produce a 3D network structure (Table 3 and Figure 4c). Complex [Hg3(timpt)2I6]‚4H2O (5). Introduction of an aromatic phenyl group between the terminal imidazol-1-ylmethyl and central triazine groups in ligand timpt not only enlarges the size of ligand but also increases the possibility of π‚‚‚π interactions between the aromatic groups.12,26 There are three crystallographically independent Hg(II) atoms in 5, although they have a similar distorted tetrahedral coordination geometry with two N atoms from two different timpt ligands and two I atoms as shown in Figure 5a,b. On the other hand, each timpt ligand coordinates with three Hg(II) atoms using its three imidazole N atoms. There are large M2L2 macrocyclic units, in

1130 Crystal Growth & Design, Vol. 7, No. 6, 2007

Figure 3. (a) A view of 3 showing the coordination environment around the Hg(II) center (ellipsoids at 30% probability). (b) A view of 1D chain of 3 through Hg-I‚‚‚Hg interactions. The hydrogen atoms are omitted for clarity. (c) Crystal packing diagram of complex 3 with the hydrogen bonds indicated by dashed lines.

which each timpt ligand uses two of its three imidazole groups to connect two Hg(II) atoms. Such M2L2 units are further linked together through the coordination of the third imidazole group with the Hg(II) atom (Figure 5b) to generate an infinite 1D chain structure (Figure 5c). Within the M2L2 units, there are strong π‚‚‚π interactions between the parallel central triazine groups of two opposite timpt ligands with centroid-to-centroid distances of 3.43 and 3.32 Å as indicated by the dashed line in Figure 5b.27 Complexes [Hg2Br4(titmb)] (6) and [Hg2Cl4(titmb)] (7). When ligand titmb was used to react with HgBr2 and HgCl2, respectively, complexes 6 and 7 were obtained. The results of the crystallographic analyses indicate that 6 and 7 have the same structure, although they showed different cell parameters as listed in Table 1. Therefore, only the structure of 6 will be described below, and the structure of 7 is shown in Supporting Information (Figures S1-S3). As exhibited in Figure 6a, there are two crystallographically independent Hg(II) atoms in the repeat unit of 6. Both Hg1 and Hg2 have the same tetrahedral coordination geometry but different binding sets (Figure 6b). Hg1 is coordinated by two N atoms from two imidazole groups with the Hg-N bond lengths of 2.147(6), 2.170(6) Å, and two Br atoms with the Hg-Br bond lengths of 2.6891(11), 2.9482-

Wang et al.

Figure 4. (a) X-ray crystal structure of 4 with the atom numbering scheme (ellipsoids at 30% probability). (b) A view of the 1D chain of 4. (c) Crystal packing diagram of complex 4 with the hydrogen bonds indicated by dashed lines.

(14) Å, while Hg2 is coordinated by one N atom from the imdazole group with the Hg-N bond length of 2.261(8) Å, and three Br atoms with the Hg-Br bond lengths of 2.5042(11), 2.5849(11), 2.6748(11) Å (Table 2). On the other hand, each titmb ligand with cis,cis,cis conformation connects three mercury(II) atoms, serving as a three-connecting linker to form an infinite 1D chain structure (Figure 6b). It is noteworthy that the Hg(II) atoms are not only linked by titmb ligands but also bridged by Br atoms within the 1D chain. The Hg1 and Hg2 are bridged by Br2 atom with the Hg1-Br2-Hg2 angle of 143.80(4)° and the Hg1-Br2 distance of 2.9482(14) Å; meanwhile, the Hg2 and Hg1A was bridged by Br3 with a Hg2-Br3-Hg1A angle of 123.46° and a Hg1A-Br3 separation of 3.16 Å, which is close to those reported for Hg-Br interactions.23 Therefore, the Hg and Br atoms also form an infinite Br‚‚‚Hg‚‚‚Br‚‚‚Hg inorganic chain linked by Hg-Br‚ ‚‚Hg interactions as shown in Figure 6b. The 1D chains range along the ac plane to form a 3D framework (Figure 6c), and the structure is stabilized by a C-H‚‚‚Br hydrogen bond (Table 3). Comparison of the Structures. Seven new Hg(II) complexes with different bidentate and tripodal ligands were successfully obtained. The X-ray crystallographic analysis indicates that the complexes 1-6 have different structures, while the 6 and 7 have the same structures as discussed above, which underlines the crucial roles of the organic ligands and the subtle effect of the

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Crystal Growth & Design, Vol. 7, No. 6, 2007 1131

Figure 5. (a) X-ray crystal structure of 5 with ellipsoids drawn at the 30% probability. (b) A view of M2L2 rings in 5 with the π-π interactions indicated by dashed lines. The hydrogen atoms and solvent molecules are omitted for clarity. (c) 1D chain structure of 5. The hydrogen atoms and water molecules are omitted for clarity.

halides. In complex 1, inorganic HgI2 units are connected by bidentate ligand iimb to form infinite 1D chains. While in the case of 3, 24-membered M2L2 macrocyclic rings, rather than the 1D chains, are formed when the same HgI2 reacted with the bib ligand. The different structures of 1 and 3 are caused by the different ligands of iimb and bib (Schemes 1 and 2). The different structures of 2 and 3 with the same bib ligand, but different halides of Br and I, imply the impact of the halide on the structure of the complexes. However, in the case of 6 and 7, which also have the same titmb ligand but different halides of Br and Cl, the same structure suggests no remarkable influence of Br and Cl on the structure of 6 and 7. Similar phenomenon has been observed in metal halides complexes with pyridine-containing ligands.28 The complexes [Cu3(L2)2Br6]‚ 4MeOH and [Cu3(L2)2Cl6]‚2DMF [L2 ) 1,3,5-tris(2-pyridylmethoxyl)benzene] have the same structure; [Hg2(L4)Cl4] also has the same structure with [Hg2(L4)Br4] but is different from that of [Hg3(L4)2I6]‚H2O [L4 ) 1,3,5-tris(4-pyridylmethoxyl)benzene].28 In complex 4, rigid tib ligands are bridged by HgI2 units to give a 1D chain containing 20-membered rings with a Hg-Hg distance of 10.56 Å. In complex 5, the basic structure is a large M2L2 macrocyclic ring consisting of two Hg atoms and two timpt ligands, in which very strong π‚‚‚π interactions exist between the central triazine groups of two opposite ligands. In addition, HgBr2 units are linked by titmb ligands with cis,cis,cis conformation to form zigzag chains in 6. On the other hand, the weak interactions, existing in complexes 1 and 3, could further affect the final structure of the complexes. In complex 1, adjacent 1D chains are further

Figure 6. (a) X-ray crystal structure of 6 with the atom numbering scheme (ellipsoids at 30% probability). (b) A view of 1D chain structure of 6 with inorganic Hg-Br‚‚‚Hg chain through Hg-Br‚‚‚Hg interactions indicated by dashed lines. (c) Crystal packing diagram of complex 6 with the hydrogen bonds indicated by dashed lines.

linked by I‚‚‚I weak interactions to generate a polycatenated ladderlike 3D framework. In addition, the M2L2 macrocyclic rings of 3 are connected by weak Hg-I‚‚‚Hg interactions to form an infinite 1D chain. Furthermore, it is interesting that the HgBr2 units are connected by Hg-Br‚‚‚Hg interactions to form an infinite Br‚‚‚Hg‚‚‚Br‚‚‚Hg inorganic chain in 6 (Cl‚‚‚ Hg‚‚‚Cl‚‚‚Hg inorganic chain in 7). The results of present and previous studies showed that flexible ligands can have different conformations and thus result in the formation of metal complexes with diverse structures. For example, the flexible bidentate ligand bib used in this study exhibited different conformations in 2 and 3 (Figures 2 and 3). Furthermore, varied shapes such as “L”, “V”, and “Z” have been

1132 Crystal Growth & Design, Vol. 7, No. 6, 2007

Wang et al.

Acknowledgment. This work was supported by the National Natural Science Foundation of China (Grant No. 20231020) and the National Science Fund for Distinguished Young Scholars (Grant No. 20425101). Supporting Information Available: X-ray crystallographic file in CIF format and the structure of 7 (Figures S1-S3). This material is available free of charge via the Internet at http://pubs.acs.org.

References

Figure 7. Emission spectra of the compounds 1 (red) and 5 (black) with λex ) 354 nm.

observed in the Cu(II)-bib complexes as reported previously.8b On the other hand, in the metal complexes with the flexible tripodal titmb ligand adopting cis,cis,cis conformation, the coordination geometry of the metal atom plays a crucial role in determining the structure of the complexes. In 6 and 7, the cis,cis,cis titmb ligands are linked together by Hg(II) atoms to give a 1D chain as mentioned above. When the titmb with cis,cis,cis conformation connected by Ag(I) atoms with linear coordination geometry, M3L2 cagelike complexes were obtained,9b and in the case of Zn(II)-titmb and Mn(II)-titmb, the structure of the complexes is a 2D honeycomb network, in which the conformation of titmb is also cis,cis,cis, but Zn(II) and Mn(II) have octahedral coordination geometry.11 Therefore, it is important to design organic ligands with a suitable structure and flexibility and choose a metal atom with a suitable coordination geometry in the construction of metal organic architectures with a desired structure and property. Photoluminescence Properties of the Complexes. The mixed inorganic-organic hybrid coordination polymers have been investigated for fluorescence properties and for potential applications.29 The photoluminescence properties of complexes 1-6 were studied in the solid state at room temperature. The measurements were carried out under the same experimental conditions and excited at a wavelength of 354 nm. No clear photoluminescence was observed for 2-4 and 6 at room temperature under our experiment conditions. As shown in Figure 7, the maximum emission wavelength of complex 1 is at 450 nm, which is close to that of the iimb ligand (emission maximum at 437 nm upon excitation at 365 nm). In addition, the maximum emission wavelength of complex 5 is at 455 nm, which is almost same as that of the timpt ligand (emission maximum at 445 nm upon excitation at 354 nm). The emissions observed in complexes 1 and 5 are tentatively assigned to the π f π* intra ligand fluorescence due to their close resemblance of the emission bands.30 Conclusions The van der waals radius of mercury(II) is much larger than other familiar metal ions such as Zn(II), Cd(II), etc. It is easier to form weak noncovalent interactions, which provides opportunities for the construction of architectures with novel structure and topology. Herein, we report some exceptional examples of the low dimensional f high dimensional complexes through such weak interactions. The analysis of the complexes’ structures with different ligands and halides showed that the key to the formation of such transformations is the nature of the mercury atom and the coordinated anion (Cl, Br, or I).

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CG060814C