Ultrafast Broadband Fluorescence Up-conversion Study of the Electronic Relaxation of Metalloporphyrins

We present a systematic study of the ultrafast fluorescence with broadband detection and similar to 110 fs resolution of 5,10,15,20-tetraphenylporphin (TPP) and 2,3,7,8,12,13,17,18-oc-taethylporphin (OEP), with open 3d-shell metals. We also revisit the cases of the closed-shell ZnTPP and ZnOEP systems. We find that in all cases, the relaxation from the Soret (B)-state to the Q-states (S-1) occurs on ultrafast time scales of <50-100 fs, regardless of the metal, its oxidation state, and the peripheral groups of the macrocycle. The analogy with free base TPP and OEP leads us to conclude that the B-Q relaxation involves only the porphyrin states. ZnTPP is an outlier compared to the entire set of investigated systems, in the sense that the B-Q relaxation is significantly slowed down and is multiexponential. We argue that because of a lower density of states in the region of the Soret band, compared to ZnOEP, the relaxation time becomes much longer. Finally, the role of metal orbitals is apparent in the relaxation of the Q-state, which is found to be much faster in the case of open-shell metals compared to closed-shell ones, hinting to an electron transfer from the porphyrin to the metal.


Published in:
Journal Of Physical Chemistry A, 123, 7, 1461-1468
Year:
Feb 21 2019
Publisher:
Washington, AMER CHEMICAL SOC
ISSN:
1089-5639
Keywords:
Laboratories:




 Record created 2019-03-13, last modified 2019-03-25


Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)