Synthesis, structural characterization and third-order nonlinear optical study of W/Cu/S cluster-based coordination polymers with thioether-containing ligands

The assembly of [Et₄N][Tp*WS₃] (Et = ethyl, Tp* = tetrakis(3,5-dimethyl-1-pyrazolyl)borate), Cu(I) with 1,3,5-tri((pyridin-4-ylthio)methyl)benzene (tptmb) or 4,4′-bis((pyridin-4-ylthio)methyl)-1,1′-biphenyl (bptmb) leads to two coordination polymer with the formulae of {[Tp*WS₃Cu₃(tptmb)(CH₃CN)](PF₆)₂·CHCl₃·2CH₃CN}_n (1·CHCl₃·2CH₃CN) and {[(Tp*WS₃Cu₃)₂(bptmb)₃(CH₃CN)](PF₆)₄·5CH₂Cl₂·1.5CH₃CN}_n (2·5CH₂Cl₂·1.5CH₃CN), respectively. Compounds 1 and 2 were characterized by elemental analysis, infrared spectroscopy, UV–vis spectroscopy, high-resolution electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. In 1, each tptmb ligand connects two adjacent cluster nodes by its three coordination arms, forming a cluster-based one-dimensional zigzag chain. In 2, equal amounts of [Tp*WS₃Cu₃(CH₃CN)]²⁺ and [Tp*WS₃Cu₃]²⁺ clusters serve as three-connected nodes and are alternatively bridged by the bptmb ligands, forming a 2D network. Z-scan tests of 1 and 2 in dimethylformamide (DMF) solution reveal they have reverse saturable absorption with effective nonlinear absorption coefficients of 1.50 × 10⁻¹¹ m/W for 1 and 5.00 × 10⁻¹¹ m/W for 2. This work could inspire the construction of coordination polymer structures using cluster nodes and flexible thioether-containing ligands, providing a new way for the development of third-order nonlinear optical materials.