INFRARED-ABSORPTION SPECTRA OF ELECTRONICALLY EXCITED LONG-LIVED METASTABLE STATES IN NA-2[RU(CN)(5)NO]CENTER-DOT-2H(2)O

[Ru(CN)(5)NO](2-) can be excited selectively by two very long-lived el ectronic metastable states (MSI and MSII) by irradiation at low temper ature with blue-near UV light. Upon excitation to MSI and MSII states, CN and NO modes suffer frequency down-shifts, a fact which implies so ftening of the named bonds. Shifts of vibrational modes of the RuNO gr oup are far larger than shifts of CN modes, a fact that indicates that the metastable states involve electronic transitions mainly located a t that group. The MSI and MSII states decay when heating at two differ ent onset temperatures T-I < T-II. A thermally driven MSI-to-MSII exci tation transfer process taking place in the temperature range T-II > T > T-I shows that MSII is energetically below MSI. Copyright (C) 1997 Elsevier Science Ltd