Inorganic Chemistry, Vol.57, No.21, 13423-13430, 2018
Deactivation Routes in Gold(I) Polypyridyl Complexes: Internal Conversion Vs Fast Intersystem Crossing
An electronic spectral and photophysical characterization of three gold(I) complexes containing heterocyclic chromophores differing in the number and arrangement of pyridine rings (pyridine, bipyridine, and terpyridine, with the acronyms pD, bD, and tD respectively) was performed. Quantum yields of fluorescence, internal conversion and triplet state formation, together with the rate constants for singlet to triplet intersystem crossing, S-1 similar to similar to similar to S-0 internal conversion and fluorescence were measured in order to equate the impact of fast triplet state formation on the amount of triplets formed. The results showed a correlation between the increase on the measured decay values of S-1 (leading to the main formation of T-1) and the increase in the charge transfer (CT) character of the lowest energy transition, as evaluated from the orthogonality of the frontier orbitals. The measured triplet state yields range from similar to 50-60% to 70%, whereas the intersystem crossing rate constants differ by almost 2 orders of magnitude, from 9.4 x 10(9) s(-1) for tD to 8.1 x 10(11) s(-1) for bD. This constitutes an evidence for the existence of a correlation between the intersystem crossing and the internal conversion mechanisms.