FEMTOSECOND TRANSIENT DYNAMICS OF A HEPTAMETALLIC HAT-RUTHENIUM(II) COMPLEX - A PHOTOPHYSICAL STUDY

A photophysical study of a heptametallic HAT-rathenium(II) complex, {R u(HAT)(3)[Ru(phen)(2)](6)}(14+) (where phen = 1,10-phenanthroline and HAT = 1,4,5,8,9,12-hexa-azatriphenylene), has been carried out using s teady state and time resolved techniques. The absence of luminescence suggests that polycomplexation changes the properties of the Ru-bridgi ng HAT luminophore inducing a decrease of the radiative rate constant and an enhancement of the non-radiative decay channel. By femtosecond transient absorption measurements a decay time of 1.9 ns has been meas ured for the (MLCT)-M-3 state formed upon excitation at 590 nm. Furthe rmore the data give information on the relaxation processes leading to the formation of the MLCT triplet state. Upon excitaton, a single dec ay time of 1.4 ps has been determined. The lack of faster decays, with in the instrumental time resolution, may indicate that this is a relax ation time from the Frank-Condon state produced upon excitation to the triplet MLCT state. (C) 1997 Elsevier Science B.V.