Solvent effect-driven assembly of W/Cu/S cluster-based coordination polymers from the cluster precursor [Et₄N][Tp*WS₃(CuBr)₃] and CuCN: isolation, structures and enhanced NLO responses

Abstract

We herein describe a coordination polymer system built upon the reactions of a W/Cu/S cluster precursor [Et4N][Tp*WS3(CuBr)3] (1, Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) with three equivalents of CuCN through solvent modulation. Four coordination polymers, namely, [Tp*WS3Cu3(μ3-DMF)(CN)3Cu(Py)] (2), [Tp*WS3Cu3(μ3-DMF)(CN)3Cu] (3), [Tp*WS3Cu3(μ3-DMF)(CN)3Cu]·4aniline (4·4aniline) and [Tp*WS3Cu3(μ3-DMF)(CN)3Cu]·2(DMF)0.5 (5·2(DMF)0.5), are isolated in different solvent systems and characterized by means of elemental analysis, FT-IR, UV-Vis, ESI-MS and single-crystal X-ray diffraction. Compounds 2-5 feature μ3-DMF association with the nest-shaped [WS3Cu3] cluster cores, yielding cubane-type [WS3Cu3O] clusters which are further linked to single Cu(I) ions through CN bridges to provide 1D or 2D structures. Compounds 3-5 have identical chemical compositions in their main fragments but with distinctively different structural features, and are therefore topological isomers. Compound 2 has a ladder-type structure in which the side rails contain alternately linked cluster cores and Cu(I) ions. Compound 3 has a 2D (6,3) network with alternately arranged cluster cores and Cu(I) ions. Both 4 and 5 have 2D structures with 4·8(2) topology. In 4, a pair of cluster cores and Cu(I) ions form a 4-membered ring which is further linked to four equivalent rings through four CN ligands via a cluster core-to-Cu arrangement; while in the structure of 5, the same 4-membered rings as those in 4 are extended to equivalent rings via a cluster core-to-cluster and Cu-to-Cu arrangement. The hyperpolarizabilities (γ) of the polymeric networks exhibit an enhancement of more than 10 times compared to their parent cluster, 1.