Spectroscopic and electrochemical properties of mixed-ligand cycloplatinated complexes based on 2-(2-thienyl)pyridine and 2-phenylpyridine with 1,10-phenantroline and its 1,4-diazine derivatives

A comparative study of dipyrido- and dibenzo-substituted 1,4-diazines {dipyrido[fh]quinoxaline (dpq), dipyrido[a,c]phenazine (dppz), 6,7-dicyanodipyrido[f,h]quinoxaline (dicnq), dibenzo[f,h]quinoxaline, dibenzo[a,c]phenazine, 6,7-dicyanodibenzo[f,h]-quinoxaline}, o-phenantroline (phen), and also of the complexes [Pt((NC)-C-boolean AND((NN)-N-boolean AND)](+) [((NC)-C-boolean AND)(-) are deproronated forms of 2-phenylpyridine and 2-(2-thienyl)pyridine; ((NN)-N-boolean AND) is ethylenediamine, phen, dpq, dppz, dicnq] was carried out by the methods of H-1 NMR, electronic absorption, and emission spectroscopy and by cyclic voltammetry. It was found that in frozen solutions of [Pt((NC)-C-boolean AND). ((NN)-N-boolean AND)](+) complexes the photoexcitation energy decay from two lowest in energy electronic excited states has isolated character and is localized on {Pt((NC)-C-boolean AND) and {Pt((NN)-N-boolean AND)} metal-complex fragments: (d-pi*(N boolean AND C))and N (d-pi*(phen)) [((NN)-N-boolean AND) = phen, dpq, dicnq)] or (d-pi*(N boolean AND C)) and (pi-pi*(diaz)) [((NN)-N-boolean AND) = dppz]. Thermal quenching of the luminescence from the (d-pi*(phen)) and (pi-pi*(diaz)) states gives rise to luminescence of the complexes in liquid solutions at 293 K only from the (d-pi*(N boolean AND C)) state.