Bis- and tris(2,3-dihydro-4a,12b-(epoxyethanooxy)[1,4]dioxino[2,3-f][1,10]phenanthroline) complexes of Ru(II): Synthesis, structure and DNA binding properties

• The synthesis and characterization of two mononuclear Ru(II) complexes.
• Single-crystal X-ray crystallography for [Ru(phen-diox)3](PF6)2.
• The phen-diox ligand was prepared by an unusual condensation via metal-assisted effect.
• The binding investigation of the complexes with FS-DNA.
• The complexes interact with DNA through the groove and hydrogen bonding.

In this paper, a mononuclear tris(chelate) ruthenium(II) complex, [Ru(phen-diox)3](PF6)2 (1) and its diaqua derivative, [Ru(phen-diox)2(H2O)2](PF6)2 (2), where phen-diox is 2,3-dihydro-4a,12b-(epoxyethanooxy)[1,4]dioxino[2,3-f][1,10]phenanthroline, have been prepared based on the condensation reaction of the coordinated 1,10-phenanthroline-5,6-dione (phen-dione) ligand with ethylene glycol using the metal-assisted effect. The condensation reaction could not occur in the absence of [Ru(phen-dione)3]2+ or [Ru(phen-dione)2(H2O)2]2+ complex. The computational studies have demonstrated that the energy of the LUMO of [Ru(phen-dione)3]2+ is about 129 kcal/mol lower than the uncoordinated phen-dione molecule. The complexes have been characterized by elemental analysis and spectroscopic techniques. The X-ray analysis of [Ru(phen-diox)3](PF6)2 (1) shows a distorted octahedral RuN6 coordination geometry around the ruthenium atom. The interaction of the complexes with DNA has been monitored by UV–Vis, fluorescence and voltammetric (CV and DPV) techniques. The Kb values of (1) and (2) for DNA binding were determined 1 × 103 and 2 × 103 M−1, respectively. Furthermore, other experiments reveal that the binding affinity of (2) is stronger than (1). The results show that the complexes interact with DNA through the groove and hydrogen bonding of the acetal oxygens of the phen-diox ligands with the nucleobases of DNA. Also, complex (2) possibly interacts with DNA via covalent bonding.