Structural Transformations of Pb(II)-trans-1,2-bis(4′-pyridyl)ethene Coordination Polymers in Solution

Reaction of bpe (bpe = trans-1,2-bis(4′-pyridyl)ethylene) with Pb(OAc)2·3H2O in the presence of trifluoroacetic acid (HTFA) affords a triple-stranded coordination polymer (CP) [Pb3(μ-bpe)3(μ-O2CCF3)2(μ-O2CCH3)2(O2CCF3)2] (1) in two days, which undergoes structural transformation in solution to yield a two-dimensional (2D) sheet-like CP [Pb(μ-bpe)(μ-O2CCH3)(O2CCF3)]·0.25bpe·1.75H2O (2) in three weeks; finally compound 2 rearranges to [Pb(μ-bpe)(O2CCH3)(O2CCF3)] (3) in the fourth week. Compound 3 has a molecular fabric-like interwoven structure formed by spiral one-dimensional (1D) coordination polymeric chains. Reaction of bpe with Pb(O2CCF3)2 and Pb(OAc)2·3H2O respectively in equimolar ratio produces [Pb(μ-bpe)(μ-O2CCF3)2] (4) and [Pb(μ-bpe)(O2CCH3)2]·0.25H2O (5). The compound 4 is a three-dimensional (3D) CP with a 42.63.8-sra (SrAl2) topology, whereas 5 has a double-stranded structure with Pb(II)···π (pyridyl) interactions between 1D chains. The compounds [Pb(μ-bpe)(μ-O2CCH3)(O2CCF3)]·0.25bpe (2a), 4, and 5 have been characterized by X-ray crystallography, while 1 and 3 were reported before. The factors influencing the rearrangement of CPs in solution have been discussed. The structural topological features observed in 2a, 4, and 5 have been attributed to the coordination preference of the Pb(II) and the carboxylate ligands.将bpe（trans-1,2-双(4′-吡啶基)乙烯）与Pb(OAc)₂·3H₂O（乙酸铅(II)三水合物）在三氟乙酸（HTFA）存在下反应两天，可得到三线链配位聚合物（CP）[Pb₃(μ-bpe)₃(μ-O₂CCF₃)₂(μ-O₂CCH₃)₂(O₂CCF₃)₂]（化合物1）；该化合物可在溶液中发生结构转变，三周后得到二维（2D）片状配位聚合物（CP）[Pb(μ-bpe)(μ-O₂CCH₃)(O₂CCF₃)]·0.25bpe·1.75H₂O（化合物2）；最终在第四周，化合物2重排为[Pb(μ-bpe)(O₂CCH₃)(O₂CCF₃)]（化合物3）。化合物3为由螺旋状一维（1D）配位聚合物链交织形成的分子织物状结构。分别将bpe与Pb(O₂CCF₃)₂、Pb(OAc)₂·3H₂O按等摩尔比反应，可得到[Pb(μ-bpe)(μ-O₂CCF₃)₂]（化合物4）与[Pb(μ-bpe)(O₂CCH₃)₂]·0.25H₂O（化合物5）。化合物4为具有4²·6³·8-sra（SrAl₂）拓扑结构的三维（3D）配位聚合物，而化合物5则为双链结构，其一维链之间存在Pb(II)···π（吡啶基）相互作用。已通过X射线单晶衍射对化合物[Pb(μ-bpe)(μ-O₂CCH₃)(O₂CCF₃)]·0.25bpe（化合物2a）、4及5进行了结构表征，而化合物1和3此前已有报道。本文讨论了配位聚合物在溶液中发生重排的影响因素，且化合物2a、4与5所呈现的结构拓扑特征可归因于Pb(II)与羧酸配体的配位偏好性。