Syntheses, characterization and third order non-linear optical properties of the ruthenium(II) complexes containing 2-phenylimidazo[4,5-f ][1,10]phenanthroline derivatives †

The ruthenium(II) complexes [Ru(dmb)2(LH)][ClO4]2 [dmb = 4,4′-dimethyl-2,2′-bipyridine; LH = 2-(4-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (PNOPH), 2-(3-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (MNOPH) and 2-(2-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (ONOPH)] and their deprotonated complexes have been synthesized and characterized. The electrochemical behaviour of these complexes were examined and compared to that of [Ru(dmb)3]2+. Non-linear optical (NLO) properties of the complexes were investigated using Z-scan techniques. All of the complexes exhibit both NLO absorption and self-defocusing effect (n2 = –0.79 × 10–17 to –1.44 × 10–17 m2 W–1, α2 = 3.00 × 10–11 to 7.09 × 10–11 m W–1, [M] = 5 × 10–5 mol dm–3 in acetonitrile solution). The corresponding effective NLO susceptibilities |χ (3)| of the complexes are 2.86 × 10–12 to 5.07 × 10–12 esu. The results indicate that the substitution and deprotonation of the ligand have an effect on the NLO properties of the complexes. Finally, the crystal structure of [Ru(dmb)2(PNOP)][ClO4]·H2O·0.5C6H6 was determined by X-ray diffraction analysis; it contains two twisted dmb ligands and the bidentate ligand PNOP with torsional angles between each dmb ring pair of 3.4 and 8.7°.