Ferrocenyl dithiophosphonate metal-based molecular compounds are infrequent with untapped potential in electrocatalysis and luminescence. A stoichiometric reaction of late 3d metal (II) (Co, Ni, Cu) salts with ferrocenyl dithiophosphonate NH4S2P (OnPr) Fc in a 1: 2 ratio produces mononuclear MS2P (OnPr) Fc2 M = CoII (1), NiII (2) complexes and a tetranuclear Cu4S2P (OnPr) Fc4 (3) Fc = Fe (η5-C5H4) (η5-C5H5) cluster. The distinct core of 3 compared to 1 and 2 indicates that NH4S2P (OnPr) Fc first serves as a sacrificial reductant and subsequently stabilizes the Cu (I) cluster. Heterometallic species (1-3) were characterized by NMR (1H, 31P), FT-IR, TGA, UV-visible spectroscopy, ESI-MS, XPS, and single-crystal X-ray diffraction. Ligand S2P (OnPr) Fc- stabilized the redox-derived tetrahedral CuI core of 3 and the M (II) -centered square (MS4) frame in 1 and 2 through (η3; μ1, μ2) and (η; μ1, μ1) bonding patterns, respectively. The irreversible single wave voltammogram indicated nonuniform electrochemical behavior of 1-3. TD-DFT indicates MLCT and weak LLCT in isostructural 1-2 and 3m CuIIS2P (OnPr) Fc2, while 3 exhibits multielectron transitions with two types of MLCT. Third-order decay confirms singlet fluorescence, and multiple electronic transitions in 3 enhance its photoluminescence (27. 5% QY) relative to 1-2, correlating the isostructural and different nuclearity features of late 3d metals with their physical and electrochemical properties.
Jangid et al. (Wed,) studied this question.