Platinum(II) and copper(II) complexes of 7-azaindole-3-carboxaldehyde: crystal structures, IR and Raman spectra, DFT calculations and in vitro antiproliferative activity of the platinum(II) complex

Abstract

Pt(II) and Cu(II) complexes, trans-[PtCl2(7AI3CAH)2] and [CuBr2(7AI3CAH)2]n, containing 7-azaindole-3-carboxaldehyde (7AI3CAH) have been synthesized and investigated by a single crystal X-ray diffraction, vibrational spectroscopy and DFT calculations. In the platinum(II) complex two pyridine nitrogen atoms of the 7AI3CAH ligands and two chloride ligands are coordinated to the central metal atom, in a square-planar trans arrangement. In the polymeric copper(II) complex the coordination geometry is a tetragonal bipyramid (4 + 2), where the in-plane ligands are two pyridine nitrogen atoms of two organic ligands and two trans-bromide ligands. The apical positions of bipyramid are occupied by the two Br ligands from the neighboring units. Thus, the CuBrBrCu double bridge system is formed. Detailed vibrational assignments of the IR and Raman spectra of the Pt(II) and Cu(II) complexes have been made on the basis of the calculated potential energy distributions (PEDs) using B3LYP method. The in vitro antiproliferative activity of trans-[PtCl2(7AI3CAH)2] was studied against different human cancer cell lines. The results have shown that this complex is comparably cytotoxic with cisplatin at the LoVo (colon cancer) and MCF7 (breast cancer) cells, whilst its cytotoxicity is significantly lower against the A549 cells (lung cancer) as compared to cisplatin. However, it is about 8-fold less toxic than cisplatin against a normal fibroblast cell line (BALB/3T3). A study on stability of trans-[PtCl2(7AI3CAH)2] in DMSO solution has been performed by FT-IR (ATR) spectroscopy to predict a possible binding mode of trans-platinum(II) complex with DNA.