Spacer-Length-Dependent Nuclearity and Cuprophilic Modulation in Copper(I) Complexes with Multidentate β-Thioketiminate Ligands

High Resolution Image Download MS PowerPoint Slide This study explores the impact of alkyl spacer length in multidentate β-thioketiminate ligands (H 2 2 L -H 2 4 L, H 2 6 L, and H 2 8 L ) on the nuclearity and structural properties of copper(I) complexes. Ligands, synthesized thiation of β-ketoiminate precursors, were characterized by 1 H, 13 C NMR, FT-IR, UV–vis spectroscopy, and ESI-MS. Reaction with CuO t Bu led to the formation of tetranuclear ([ L Cu 2 ] 2, C2–C4 spacers) and bis-trinuclear ([ L Cu 2 ] 3, C6 and C8 spacers) complexes, analyzed by 1 H, 13 C NMR, FT-IR, UV–vis, Raman, and single-crystal X-ray diffraction. Each Cu(I) center adopts a distorted trigonal planar geometry, coordinated by one nitrogen and two sulfur atoms through chelating and bridging modes. Shorter spacers favor tetranuclear clusters with stronger cuprophilic interactions (Cu···Cu: 2.58–3.43 Å), while longer spacers promote bis-trinuclear clusters, including a previously unreported triple-helicate with asymmetric Cu···Cu distances (2.76–2.87 Å). Importantly, coordination of 2,4,6-trimethylphenyl isocyanide induces fragmentation of these clusters into dinuclear [ L (Cu-CNR) 2 ] complexes, as confirmed by single-crystal X-ray diffraction and FT-IR (νC≡N blue shift), revealing a spacer-dependent susceptibility to isocyanide-driven S–Cu bridge cleavage. These findings demonstrate spacer length as a key modulator of Cu(I) cluster nuclearity and metal–metal interactions, advancing bioinspired metallosupramolecular design.