Three isoreticular W/Cu/S 1D coordination polymers show good third-order NLO performance.

Main observation and conclusion The assembly of [Et4N][Tp*WS3] (1) with CuX (Tp* = hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; X = Cl, Br, and I) or [Cu(MeCN)4][PF6] in the presence of tetratopic ligand hexamethylenetetramine (HMT) afforded an array of four cluster‐based compounds, which are either neutral or anionic. These compounds include [Tp*WS3Cu3Cl2(HMT)] (2, monomer, neutral), [Tp*WS3Cu3Br2(HMT)] (3, monomer, neutral), [Tp*WS3Cu3I1.5(HMT)]2I (4, dimer, anionic), and [Tp*WS3Cu2(HMT)]2(PF6)2 (5, dimer, anionic). The size of the halogen is found to dictate the structures (2/3 versus 4), and the presence/absence of halogen also affects the utilization of coordinate site of HMT (4 versus 5) by creating more available Cu(I) site in the case of 5. The structures of 2—5 are also characterized using elemental analysis, Fourier‐transform infrared (FT‐IR) spectra, and ultraviolet‐visible (UV‐Vis) spectroscopy, with the dimeric structure of 5 also selected for the third‐order nonlinear optical (NLO) property investigations. The NLO measurement results suggest that the hyperpolarizability value (γ) of 5, reflecting its NLO properties as a neat material, features 2.12×10−30 esu, and it is comparable to other W/Cu/S cluster‐based molecular entities, rendering 5 a promising NLO‐active material.