Biophysical studies on novel metallo-systems and their interactions with DNA and small molecules

Abstract

The DNA binding interactions of five novel bis(2,2':6'2"- terpyridine)ruthenium(II) complexes functionalised with an aryl tail group (i) biphenylene (biphen), (ii) P-napthyl (napth), (iii) phenanthrene (phen), (iv) anthracene (anth) and (v) pyrene (pyr) in the 4' position on each terpyridine ligand were investigated with calf thymus DNA (ct-DNA), poly [d(A-T)]2 and poly [d(G-C)]2 DNA using the spectroscopic techniques of absorbance, circular dichroism (CD) and linear dichroism (LD). All five complexes bind non-covalently to DNA. At low complex concentrations, the anth, phen and pyr complexes were found to intercalate their aryl tail groups between DNA bases. The napth complex exhibits both an intercalative and a non-intercalative mode. The biphen complex exhibits groove binding with no significant tail intercalation. At high metal complex concentrations, aggregation of the complexes on the DNA is observed, resonance light scattering indicate aggregates of low nuclearity along the groove. The DNA binding interactions of a novel series of structurally similar eighteen platinum(H) square planar complexes with subtle ligand variations of the formula [Pt(L)Cl(DMSO)] where L denotes an acylthiourea ligand system were investigated with ct-DNA, poly [d(A-T)]2 and poly [d(G-C)]2 DNA, 5'-mononucleotides and 9- methylguanine. Absorbance, CD and LD studies indicate ligand variation affects DNA binding interaction. Mass spectrometric studies suggest these complexes bind covalently to DNA via the loss of the chloride or possibly the DMSO groups on the platinum. Supramolecular copper(l) and silver(l) metal lo-cyclophanes and their interactions with the isomers of di- and tri-methoxybenzenes and chiral anionic compounds were investigated. The metallo-cyclophanes can adopt two conformations, a helical and a bridging non-helical structure. CD, NMR and X-ray crystallography show the dianion sodium antimonyl-L-tartrate can resolve this mixture. Absorbance and fluorescence studies suggest the metallo-cyclophanes bind methoxybenzenes. The design and synthesis of novel longer asymmetric ligands capable of assembly into a larger suprarnolecular metallo-cyclophanesis included