abstract
Absorption and relaxation dynamics of electronic states of free-base, Co(II), Cu(II) and Zn(II) porphyrins bearing a b-(2,2-difluoro-1,3,2-dioxaborinin-5-yl) group were investigated in dimethyl sulfoxide by using distinct time-resolved spectroscopic techniques. Furthermore, excited state absorption cross-section spectra were determined by combining white light continuum Z-Scan and transient absorption techniques. In the case of the free-base (2H) and Zn(II) porphyrins, we were able to quantify singlet-triplet conversion by analyzing the evolution of time-resolved fluorescence. Relaxation lifetimes from the excited to the ground state were observed in both porphyrins at nanosecond time scale. However, for Co(II) and Cu(II) metalloporphyrins it was observed in the picosecond time scale through femtosecond transient absorption, indicating that both compounds relax back to the ground state only by internal conversion processes. Co(II) and Cu(II) heavy atoms seem to prohibit the radiative and intersystem crossing processes. (c) 2021 Elsevier B.V. All rights reserved.
keywords
NONLINEAR ABSORPTION; ZINC PORPHYRIN; QUANTUM YIELD; COMPLEXES; SPECTRA; CO
subject category
Spectroscopy
authors
Sciuti, LF; Costa, LD; Guieu, S; Cocca, LHZ; Iglesias, BA; Mendonca, CR; Tome, AC; Faustino, MAF; De Boni, L
our authors
Samuel Jacques André Guieu
Junior Researcheracknowledgements
The authors gratefully acknowledge financial support from Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq - Universal Grant 425124/20185; 409150/2018-5 and 304711/20187) ; FAPESP 2018/11283-7 and 2016/208861; CoordenacAo de Aperfeicoamento de Pessoal de Nivel SuperiorBrasil (CAPES) Finance Code 001; Army Research Laboratory (W911NF-17-1-0123) and the Air Force Office of Scientific Research (FA95501210028) . Thanks are also due to Fundacao para a Ciencia e a Tecnologia (FCT) for the financial support to project PTDC/QEQQOR/6160/2014, the LAQV-REQUIMTE (UIDB/50006/2020) , and the CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT UID/CTM/50011/2019) , through national funds and, when applicable, cofinanced by the FEDER within the PT2020 Partnership Agreement. L. D. Costa thanks FCT for her doctoral grant (SFRH/PD/BD/114578/2016) . S. Guieu also thanks the funding from national funds (OE) , through FCT, in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the DecreeLaw 57/2016, of August 29, changed by Law 57/2017, of July 19.