ULTRAFAST VIBRATIONAL-RELAXATION AND LIGAND PHOTODISSOCIATION PHOTOASSOCIATION PROCESSES OF NICKEL(II) PORPHYRINS IN THE CONDENSED-PHASE/

Citation
Hs. Eom et al., ULTRAFAST VIBRATIONAL-RELAXATION AND LIGAND PHOTODISSOCIATION PHOTOASSOCIATION PROCESSES OF NICKEL(II) PORPHYRINS IN THE CONDENSED-PHASE/, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 101(20), 1997, pp. 3661-3669
Citations number
59
Categorie Soggetti
Chemistry Physical
ISSN journal
10895639
Volume
101
Issue
20
Year of publication
1997
Pages
3661 - 3669
Database
ISI
SICI code
1089-5639(1997)101:20<3661:UVALPP>2.0.ZU;2-3
Abstract
We have carried out a femtosecond transient absorption spectroscopic s tudy on nickel(II) porphyrins in various solvents in order to obtain d etailed information on vibrational relaxation processes occurring in t he initial stage after photoexcitation to the highly excited states. W e found the decay process of time constant of approximately 1 ps corre sponding to the intramolecular vibrational relaxation process for Ni(I I)TPP and Ni(II)OEP in toluene. In addition to this process, the inter molecular vibrational relaxation process with 10-20 ps lifetime was al so observed for Ni(II)OEP in toluene, although its contribution to the overall decay process is relatively weak probably due to the weak sol ute/solvent interaction. In coordinating solvents such as pyridine and piperidine, we observed the intramolecular vibrational relaxation pro cesses before complete population of the bottleneck excited metal (1)\ 0,d(z2)] or (3)\0,(3)(d,d)]. In this case, it is likely that the inter molecular vibrational relaxation process associated with photodissocia tion/photoassociation processes depending on the selective excitation of four- and six-coordinate species is accompanied by the intramolecul ar vibrational relaxation due to the strong solute/solvent interaction . These processes are also believed to be responsible for the excess e nergy dissipation of highly excited nickel(II) porphyrins into the sur rounding solvent molecules.