Cyclometalated Rhodium(III) Complexes Based on Substituted 2‐Phenylpyridine Ligands: Synthesis, Structures, Photophysics, Electrochemistry, and DNA‐Binding Properties

A new series of octahedral rhodium (III) complexes 1-8 of the type [(Ln)2Rh(dppz)]Cl (n=1-6) and [(Ln)2Rh(dppz)](PF6) (n=1, 7, 8), in which L = 2-phenylpyridine with different modifications as C, N-chelating ligand and dppz = dipyrido[3,2-a:2′,3′-c]phenazine have been synthesized and fully characterized. The photophysical properties of the complexes were investigated. The X-ray single crystal structures of five complexes [(L1)2Rh(dppz)](PF6), [(L2)2Rh(dppz)]Cl, [(L3)2Rh(dppz)](PF6), [(L4)2Rh(dppz)](PF6) and [(L8)2Rh(dppz)](PF6) confirmed the anticipated structure and revealed the effect of substitute on the structure of complex which was reasonably explained through experimental electrochemical characterisation. The interaction of complexes 1-8 with calf thymus DNA (CT DNA) has been verified by the fluorescent detection of ethidium bromide (EB) displacement studies. The result clearly suggested that the DNA-binding abilities of these Rh complexes is not only influenced by the DNA-intercalator dppz by also highly influenced by the electronic and steric properties of the C, N-chelating ligand.