Short‐time photodecay dynamics of meso‐tetra(p‐hydroxyphenyl)porphine in the condensed phase explored via resonance Raman spectroscopy and density functional theory calculation

Abstract

Resonance Raman (RR) spectra of free-base meso-tetra(p-hydroxyphenyl)porphine(THPP) were obtained with 397.9, 416 and 514 nm excitation wavelengths, and density functional calculations were carried out to help the elucidation of the photorelaxation dynamics of Soret (B x and B y bands) electronic transitions and the RR spectra of THPP. The RR spectrum indicates that the Franck-Condon (FC) region photorelaxation dynamics for the S 0 → S 5 excited electronic state is predominantly along the totally symmetric C m -phC stretching and the C β C β stretchingand simultaneously along the asymmetric (C m C α )as stretching, ν(phC C)asstretching, δ(NH)s and γ (C β H) vibrational relaxation processes, while that for S 0 → S 4 electronic state is predominantly along the C m -phC stretching and pyrrole breathing. The excited-state structural dynamics of THPP determined from the RR spectra shows that internal conversion (IC) B y → B x electronic relaxation occurs in tens of femtoseconds, and the short-time dynamics is interpreted using the time-dependent wave packet theory and Herzberg-Teller (vibronic coupling) contributions.

Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy

“…The absorption spectra of all three isomers consist of a Soret band or B band, conventionally identified as S 0 → S 2 transition, at around 416 ± 2 nm with a shoulder at 400 ± 2 nm, and two component Q bands (S 0 → S 1 transition), Q x and Q y , with four distinct peaks at 512 ± 2, 545 ± 2, 588 ± 2, and 641–654 nm. In comparison to the prior assignment of absorption peaks of tetraphenyl porphyrin (TPP) within the framework of Gouterman’s well-described “four orbital” model, − we safely assign the 416 nm band as B (0 ← 0) and remaining all peaks in Q-bands as y -polarized Q y (1 ← 0), Q y (0 ← 0), and x -polarized Q x (1 ← 0), Q x (0 ← 0), respectively, where numbers in parentheses represents number of quanta in the active vibrational modes in the upper and lower electronic states of the transitions in Franck–Condon principle. As is observed in Figure A a noticeable bathochromic shift of 13 nm in the peak position corresponds to Q x (0, 0) transition on going from TpyP(4) to TpyP(2) and is rationalized as increased resonative interaction of negative charge density around the N atom of pyridine with porphyrin macrocycle on going from TpyP(4) to TpyP(2).…”

Electronic structure of tetra(4-aminophenyl)porphyrin studied by photoemission, UV–Vis spectroscopy and density functional theory

“…Several theoretical and experimental studies were performed on tetraphenyl porphyrin (TPP) leading to a consistent understanding of the related opto-electronic structure [12,17,16,19,20]. A natural development consists of substituting the TPP phenyls with functional groups capable of tuning the opto-electronic properties [21,22]. Very recently peripheral functionalization was also studied to develop nano-structuration properties [23][24][25] including the formation of covalent organic networks [26][27][28].…”

Excited-State Quenching of Porphyrins by Hydrogen-Bonded Phenol-Pyridine Pair: Evidence of Proton-Coupled Electron Transfer

“…The absorption spectra of all studied porphyrins (Chart ) in DCM consist of a Soret band or a B band, conventionally identified as the S 0 → S 2 transition, at around 418 ± 2 nm, with a shoulder at 400 ± 2 nm, and two component Q bands (S 0 → S 1 transition), Q x and Q y , with four distinct peaks at 515 ± 3, 550 ± 4, 588 ± 2, and 650 ± 4 nm (Figure ). Within the framework of Gouterman’s well-described “four orbital” model, − the Soret band at ∼418 nm is attributed to B (0 ← 0) and the remaining peaks in Q bands are attributed to y -polarized Q y (1 ← 0) and Q y (0 ← 0) and x -polarized Q x (1 ← 0) and Q x (0 ← 0) where numbers in parentheses correspond to the number of quanta in the operative vibrational modes in the excited and ground electronic states of the transitions in the Franck–Condon principle.…”