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

Abstract

A new series of octahedral rhodium(III) complexes 1 – 8 of the type [(L n ) 2 Rh(dppz)]Cl ( n = 1–6) and [(L n ) 2 Rh(dppz)](PF 6 ) { n = 1, 7, 8; L = 2‐phenylpyridine, with different modifications, as the 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 have been investigated. The single‐crystal X‐ray diffraction structures of five complexes – [(L1) 2 Rh(dppz)](PF 6 ), [(L2) 2 Rh(dppz)]Cl, [(L3) 2 Rh(dppz)](PF 6 ), [(L4) 2 Rh(dppz)](PF 6 ), and [(L8) 2 Rh(dppz)](PF 6 ) – have confirmed the anticipated structure and have revealed the effect of substitution on the structure of the complex, which has been reasonably explained through experimental electrochemical characterization. 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 suggests that the DNA‐binding abilities of these Rh complexes are not only influenced by the DNA‐intercalator dppz, but are also highly influenced by the electronic and steric properties of the C,N‐chelating ligands.