ELECTRONIC AND RESONANCE RAMAN-SPECTRA OF THE PYRAZINE)RUTHENIUM(II)-HEXAQUIS(RUTHENIUM(II)EDTA) SUPRAMOLECULAR COMPLEX

Resonance Raman and electronic spectra of the pyrazine)ruthenium(II)-h exaquis{ruthenium(II)EDTA} supramolecular complex are reported in this paper. Excitation in the 457-676 nm range leads to the selective enha ncement of the Ru-bipyrazine vibrational peaks according to distinct p atterns, supporting the assignment of the absorption bands at 670 and 490 nm as charge-transfer (MLCT) transitions from the [Ru(II)EDTA] d(p i) orbitals to the pi(1) and pi(2)* LUMO levels of the bipyrazine lig and. A vibronic coupling mechanism involving the two excited states is suggested for the excitation at 490 nm. The occurrence of MLCT transi tions in the [Ru(bpz)(3)](2+) central unity, around 440 nm, is support ed by the Raman and fluorescence excitation profiles.