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[摘要]：77 To study the conformations (configurations) of 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H6L), eleven new coordination polymers were isolated from hydrothermal reactions of different metal salts with all cis 1e,2a,3e,4a,5e,6a-cyclohexanehexacarboxylic acid (3e+3a, H6LI) and characterized. They are [Cd12(m6-LII)(m10-LII)3(m-H2O)6(H2O)6]?6.5H2O (1), Na12[Cd6(m6-LII)(m6-LIII)3]?7H2O (2), [Cd3(m13-LII)(m-H2O)] (3), [Cd3(m6-LIII)(2,2'-bpy)3(H2O)3]?H2O (4), [Cd4(m4-LVI)2(4,4'-Hbpy)4(4,4'-bpy)2(H2O)4]?.5H2O (5), [Cd2(m6-LII)(4,4'-Hbpy)2(H2O)10]?H2O (6), [Cd3(m11-LVI)(H2O)3] (7), [M3(m9-LII)(H2O)6] (M = Mn (8), Fe (9), and Ni (10)), and [Ni4(OH)2(m10-LII)(4,4'-bpy)(H2O)4]?H2O (11). Three new conformations (configurations) of 1,2,3,4,5,6-cyclohexanehexacarboxylate, 6e (LII; 1a,2b,3a,4b,5a,6b), 4e+2a (LIII; 1a,2a,3b,4a,5b,6b) and 5e+1a (LVI; 1a,2a,3a,4b,5a,6b), were derived from the conformational conversions (isomerization) of LI and trapped in these complexes by controlling the conditions of the hydrothermal systems. Complexes 1 and 2 have three-dimensional (3D) coordination frameworks with nanoscale cages and were obtained at relatively low temps. A quarter of the LI ligands undergo a conformational transformation into LII while the others are transformed into LIII in the presence of NaOH in 2, while all of the LI are transformed into LII in the absence of NaOH in 1. Complex 3 has a 3-dimensional condensed coordination framework, which was obtained under similar reaction conditions as 1, but at a higher temp. The addn. of 2,2'-bipyridine (2,2'-bpy) or 4,4'-bipyridine (4,4'-bpy) to the hydrothermal system as an auxiliary ligand also induces the conformational transformation of H6LI. A new LVI conformation was trapped in complexes 4-7 under different conditions. Complex 4 has a 3-dimensional microporous supramol. network constructed from a 2-dimensional LIII-bridged coordination layer structure by p-p interactions between the chelating 2,2'-bpy ligands. Complexes 5-7 have different frameworks with LII/LVI conformations, which were prepd. by using different amts. of 4,4'-bpy under similar synthetic conditions. Both 5 and 7 are 3-dimensional coordination frameworks involving the LVI ligands, while 6 has a 3-dimensional microporous supramol. network constructed from a 2-dimensional hydrogen bonds. 3D coordination frameworks 8-11 were obtained from the H6LI ligand and the paramagnetic metal ions MnII, FeII, and NiII, and their magnetic properties were studied. Of particular interest to the authors is that two copper coordination polymers [{CuII2(m4-LII)(H2O)4}{CuI2(4,4'-bpy)2}] (12a) and [CuII(Hbtc)(4,4'-bpy)(H2O)]?H2O (H3btc = 1,3,5-benzenetricarboxylic acid) (12b) resulted from the same 1-pot hydrothermal reaction of Cu(NO3)2, H6LI, 4,4'-bpy, and NaOH. The Hbtc2- ligand in 12b was formed by the in situ decarboxylation of H6LI. The obsd. decarboxylation of the H6LI ligand to H3btc may serve as a helpful indicator in studying the conformational transformation mechanism between H6LI and LII-VI. Trapping various conformations in metal-org. structures may be helpful for the stabilization and sepn. of various conformations of the H6L ligand. |
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