Abstract:
Four new Ru(II) complexes, [RuII(MeMPTP)(bpy)Cl]PF6 (1), [RuII(MeMPTP)(dmbpy)Cl]PF6 (2), [RuII(MeMPTP)-
(dmcbpy)Cl]PF6 (3) and [RuII(MeMPTP)(Pic)2Cl]PF6 (4) [where, MeMPTP ¼ 40
-(4-methylmercaptophenyl)-
2,20
:60
200-terpyridine, bpy ¼ 2,20
-bipyridine, dmbpy ¼ 4,40
-dimethyl-2,20
-bipyridine, dmcbpy ¼
4,40
-dimethoxycarbonyl-2,20
-bipyridine and pic ¼ 4-picoline] were synthesized and characterized via
various spectroscopic techniques. The molecular structures of the complexes 1 and 2 were determined
by single crystal X-ray diffraction analysis. Catalytic activity for chemical oxidation of water of the
complexes 1–4 reveals that the rate of O2 evolution follows the trend 1 > 4 > 2 > 3. Except the
unsubstituted complex 1, the catalytic rate for O2 generation of 2 and 4, containing electron-donating
(–CH3) groups, is higher than that of 3, bearing an electron-withdrawing (–COOMe) group on the bpy,
while the turn over number (TON) of the complexes follows an opposite trend. The difference in the
water oxidation activity of the complexes has been correlated to the effect of the substituents on the
ancillary ligands in facilitating the electron density on the Ru(II) center to achieve the higher oxidation
states required for the water oxidation catalysis. Interestingly, water oxidation study of the complexes
1–4 fills the missing gap between the well-studied mononuclear ruthenium complexes based on terpy/
bpy and the MeMPTP/phen ligands
