SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF ZEOLITE-ENTRAPPED BISTERPYRIDINE RUTHENIUM(II) - DRAMATIC CONSEQUENCES OF LIGAND-FIELD-STATE DESTABILIZATION

A bisterpyridine complex of ruthenium(II) (RU(tpy)(2)(2+)) has been pr epared in zeolite Y supercages and investigated by electronic absorpti on, electronic emission, and resonance Raman spectroscopy. In free sol ution this complex is practically nonluminescent, having a very short excited-state lifetime (250 ps) at room temperature. However, entrapme nt within the zeolite supercage results in dramatic increases in emiss ion intensity and excited-state lifetime (140 ns) at room temperature. The observed temperature dependence of the excited-state lifetime has been modeled by a kinetic equation with two thermal terms correspondi ng to the so-called fourth (MLCT)-M-3 state and ligand-field state (LF ), respectively. It is shown that the increased lifetime of the entrap ped complex results from zeolite-induced destabilization of the LF sta te, a conclusion which is in agreement with results obtained for a num ber of other zeolite-entrapped ruthenium(II) polypyridine complexes.