Mononuclear copper(i) complexes of triphenylphosphine and N,N′-disubstituted thioureas as potential DNA binding chemotherapeutics

Abstract

In this work, nine new mixed-ligand complexes with the general formula [CuBr(TPP)₂Tu^1–9] were synthesized. The copper(I) complexes of triphenylphosphine (TPP) and different N,N′-disubstituted thioureas (Tu) were characterized via spectroscopic techniques including Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (¹H, ¹³C, and ³¹P NMR), and single-crystal X-ray diffraction (SC-XRD). The complexes were synthesized via the direct reaction of bromo(tris(triphenylphosphine)copper(I)) [BrCu(PPh₃)₃] precursor and thiourea ligand solution under ambient conditions. Complexes 1, 2 and 3 crystallized in a triclinic system with the P space group. Each complex is mononuclear, and the copper atom is tetrahedrally attached to two TPP groups through the phosphorous atom, one thiourea molecule through the sulfur atom and one bromine atom. The synthesized compounds were docked with a DNA macromolecule to predict their binding site and it was found that all molecules showed favorable binding to the DNA minor grooves. The DNA interaction studies of the representative complexes demonstrated their efficient DNA binding affinities. Based on the docking and DNA interaction results, complex 7 was found to be the best binder with a docking affinity of 382.2 kJ mol⁻¹ and binding constant of 3.96 × 10⁴ M⁻¹. This compound tends to interact with the minor groove through the bromine atom positioning the side triphenylphosphine rings along the X-axis of the groove while keeping the 1-(2-chlorobenzyl)-3-(3-(trifluoromethyl)phenyl)thiourea ring on the outside.