Synthesis, crystal structures and biological activities of halogeno-(O-alkylphenylcarbamothioate)bis(triarylphosphine)copper(I) complexes

Abstract

The aim of this work was to synthesize and characterize a new series of copper(I) complexes with thiocarbamate ligands and to evaluate their biological activity. Treatment of CuX salts (X = Cl, Br, I) with O-alkyl N-phenylcarbamothioates in the presence of two equivalents of PAr3 (Ar = Ph, p-C6H4OMe) affords a series of mononuclear thione complexes [(Ar3P)2Cu{ROC(=S)N(H)Ph}X)] C1-C10. According to X-ray diffraction analyses, all complexes adopt a distorted tetrahedral geometry and feature intramolecular NH···Hal bonding, giving rise to six-membered cycles. Like in the case of the literature-known chloro‑compounds C1 and C2 (d(NH···Cl) ∼ 2.29 Å), the bromo‑derivatives C3–C6 exhibit strong NH···Hal distances varying from 2.48 to 2.63 Å. This intramolecular bonding, which is weaker for the iodo complexes C7-C10 (∼ 2.75 Å), has also been studied by Hirshfeld surface analysis of C1, C3, C4 and C6. The crystal structure of two 1D-polymeric intermediates occurring during the synthesis of C7 and C9, namely [{Cu(μ2-I)2Cu}(μ2-L)2]nCP1 and CP2, has also been elucidated. The complexes display weak luminescence in solution centered on the triarylphosphine ligands. In contrast, in the solid state a high-energy band around 350–450 nm centered on the thioamidate and triarylphosphine ligands is observed, along with a second low energy band typical for MLCT/XLCT states around 450–550 nm. The screening of the biological activity of these complexes reveals the absence of any significant antibacterial capacity. However, the presence of an antioxidant activity with a maximum activity for complexes C3 and C4 has been evidenced using the colorimetric DDPH method. This has been probed in vivo on Wistar rats for the preservation of hepatocytes integrity after liver hypothermic conservation (4 °C) for 24 h in Krebs solution with normal cellular state by addition of [(Ph3P)2Cu{EtOC(=S)N(HPHh}I] C8.