An insight into the coordination specificity of polyaromatic hydrocarbons (PAHs) grafted hydrazones towards rhodium(III)

Upon treatment of the polyaromatic hydrocarbon (PAH) grafted hydrazones HL (1) with [RhCl(PPh3)3], complexes of type [Rh(L)Cl2(PPh3)2] (2) have been isolated. The X-ray diffraction technique has been used to elucidate the structures of three complexes. The rich spectral features of the complexes in the UV–vis region have been explained by TD-DFT and their redox active nature has been validated from the well-defined responses at mild potentials as well as from a theoretical investigation of the redox orbitals. Intra-molecular π–π stacking interactions coupled with the electron withdrawing ability of the pendant PAH moiety within the ligand framework play a significant role in altering the mode of coordination (flexidentate behaviour of HL) as well as the metal–ligand bond parameters.