Optical, electrochemical and structural studies on the first rhenium compound of di-2-pyridylketonephenylhydrazone (dpkphh), fac-Re(CO) 3(dpkphh)Cl

Abstract

fac-Re(CO) 3(dpkphh)Cl isolated from the reaction between Re(CO) 5Cl and dpkphh in refluxing toluene exhibits rich physico-chemical properties. Spectroscopic measurements on fac-Re(CO) 3(dpkphh)Cl revealed strong solvent dependence as manifested by the high sensitivity of its 1H NMR and electronic absorption spectra to solvent variation. Electrochemical measurements on fac-Re(CO) 3(dpkphh)Cl in CH 2Cl 2 show irreversible/quasi-reversible redox processes pointing to electrochemical transformation(s) following electronic-transfer(s). Crystals of fac-Re(CO) 3(dpkphh)Cl·CH 3CN obtained from an acetonitrile solution of fac-Re(CO) 3(dpkphh)Cl are chiral and structural studies show racemic twins of fac-Re(CO) 3(dpkphh)Cl.CH 3CN with fac-Re(CO) 3(dpkphh)Cl molecules in distorted octahedral geometry. The molecules pack shows stacks of well separated strands of fac-Re(CO) 3(dpkphh)Cl·CH 3CN in double helix formation with a network of hydrogen bonds that include solvent–solute and solute–solute interactions. The interlocked helical structure of fac-Re(CO) 3(dpkphh)Cl·CH 3CN and weak bond energies of the non-covalent interactions may account for the optical behavior of fac-Re(CO) 3(dpkphh)Cl·CH 3CN as any slight interaction between this system ( fac-Re(CO) 3(dpkphh)Cl and surrounding solvent molecules) and its surroundings may disrupt the weak solvent–solute and solute–solute interactions.