Spectroscopic Evidence in Solid and Solution of a Discrete Copper(I) Tetrahedral Complex Dimer Supported by Supramolecular Interactions

Abstract

The first study of the self-association of a copper(I) tetrahedral complex ([Cu(N-{4-nitrophenyl}pyridine-2-yl-methanimine)(PPh3)Br]) has been performed. The formation of a discrete dimer supported by supramolecular π–π stacking and C–H···Br interactions was established by X-ray diffraction techniques. 1D- and 2D NMR techniques were used for the structural characterization of this compound in solution. Unexpected 1H–1H NOE effects are coherent with the presence of a dimer in solution, whose structure replicates that found in the crystal. Dimerization constants obtained by VT-1H NMR spectroscopy allowed the determination ofthe thermodynamic parameters for the self-association process, namely ΔS = –0.67 ± 0.21 cal mol–1 K–1, ΔH = –2.00 ± 0.05 kcal mol–1 and ΔG(298 K) = –1.79 kcal mol–1. Consequently, this association process is enthalpy driven.