Syntheses, structures and fluorescence properties of two Zn(II) coordination compounds with cis-4-cyclohexene-1,2-dicarboxylate ligand

Two Zn(II) coordination compounds, [Zn2(L)2(bipy)]n (1) and [Zn2(L)2(phen)2]2·14.75H2O (2), (H2L = cis-4-cyclohexene-1,2-dicarboxylic acid; bipy = 4,4’-bipyridine; phen = 1,10-phenanthroline), were synthesized. The L2– anions act as tri- and tetradentate ligands to bind to adjacent Zn(II) centers through carboxylate groups in µ1-η1:η0, µ1-η1:η1, µ2-η1:η1 and µ2-η2:η0 coordination fashions, respectively, forming binuclear units. Compound 1 has a chain structure composed of these dinuclear units, which is further extended via the bridging bipy molecules to afford a two-dimensional structure. Compound 2 features two binuclear structural units. The topological analysis of compound 1 reveals a (3,4,4,5)-connected net with the point symbol of {43‧62‧8}{43}{44‧62}{44‧66}. The fluorescence measurements have shown that compounds 1 and 2 present blue and blue-green fluorescence with emission maxima at 406 nm and 480 nm, respectively, which are ascribed to intra-ligand transitions.本研究合成了两种锌(II)配位化合物，分别为{[Zn₂(L)₂(bipy)]ₙ}(1)与{[Zn₂(L)₂(phen)₂]₂}·14.75H₂O(2)，其中H₂L为顺式-4-环己烯-1,2-二羧酸(cis-4-cyclohexene-1,2-dicarboxylic acid)，bipy为4,4'-联吡啶(4,4’-bipyridine，简称bipy)，phen为1,10-邻菲啰啉(1,10-phenanthroline，简称phen)。配体L的二价阴离子分别以三齿配体与四齿配体的形式，通过羧酸根采用μ₁-η¹:η⁰、μ₁-η¹:η¹、μ₂-η¹:η¹及μ₂-η²:η⁰的配位模式与相邻锌(II)中心配位，形成双核结构单元。化合物1以该双核结构单元为构筑基元构成一维链状结构，再经桥联联吡啶分子进一步拓展为二维结构。化合物2包含两个双核结构单元。对化合物1的拓扑分析结果显示，其呈现(3,4,4,5)连接的拓扑网络，点符号为{4³·6²·8}{4³}{4⁴·6²}{4⁴·6⁶}。荧光性能测试表明，化合物1与2分别在406 nm和480 nm处达到荧光发射最大值，呈现蓝色与蓝绿色荧光，该发射源于配体内电子跃迁。