Preparation and cis-to- trans transformation study of square-planar [Pt(L n) 2Cl 2] complexes bearing cytokinins derived from 6-benzylaminopurine (L n) by view of NMR spectroscopy and X-ray crystallography

Abstract

Mononuclear, square-planar platinum(II) complexes involving derivatives of aromatic cytokinins as the ligands, and having the general formula cis-[Pt(L n ) 2Cl 2] ( 1– 3) and trans-[Pt(L n ) 2Cl 2] ( 4– 6), where n = 1–3, L 1 = 2-chloro-6-(benzylamino)-9-isopropylpurine, L 2 = 2-chloro-6-[(4-methoxybenzyl)amino]-9-isopropylpurine and L 3 = 2-chloro-6-[(2-methoxybenzyl)-amino]-9-isopropylpurine, have been synthesized and characterized by elemental analysis, MALDI-TOF mass, FT IR, 1H, 13C, 15N and 195Pt NMR spectral measurements. Dynamic cis-to- trans isomerization process of complex 1 in N, N′-dimethylformamide (DMF) has been investigated by means of multinuclear NMR spectroscopy. The solid-state structures of 1, 4 · (DMF) 2, and 5 have been determined by single crystal X-ray analysis. X-ray structures revealed that the heterocyclic ligands are coordinated to platinum via nitrogen atom N(7) in all the complexes studied. In vitro cytotoxicity of the prepared complexes against MCF7, G361, K562, and HOS has been evaluated. Owing to low solubility of the complexes in water, the cytotoxicity has been only tested up to 5 μM concentration. Unfortunately, all complexes have been found to be non-cytotoxic in the accessible concentration range.