Light induced intramolecular energy and electron transfer events in carbazole–corrole and phenothiazine-corrole dyads

Abstract

We report two corrole based donor–acceptor (D–A) dyads, Cbz-Cor and Ptz-Cor to understand the energy/electron transfer reactions. In these D–A systems, the donor, either carbazole (Cbz) or phenothiazine (Ptz), is covalently connected at the meso-phenyl position of 10-(phenyl)-5,15-bis-(pentafluorophenyl)corrole (Ph-Cor) by C–N linkage. Both the dyads were characterized by 1H NMR, MALDI-TOF MS, UV-vis, electrochemical, computational methods, study state fluorescence and TCSPC techniques. A comparison of absorption spectra with their reference monomeric compounds (Cbz-Ph, Ptz-Ph and Ph-Cor) revealed minimal ground-state interactions between chromophores in both dyads. Fluorescence studies suggested that singlet–singlet energy transfer from 1Cbz* to corrole is the major photochemical pathway in the Cbz-Cor dyad with a quenching efficiency of [Formula: see text]99%. Detailed analysis of the data suggests that Forster’s dipole–dipole mechanism does not adequately explain this energy transfer. However, at a 410 nm excitation, florescence quenching is detected in Ptz-Cor (49%) supporting a photo induced electron transfer (PET) process from the ground state of PTZ to the excited state of corrole macrocycle. The electron-transfer rates ([Formula: see text] of Ptz-Cor are found in the range [Formula: see text] to [Formula: see text] and are concluded to be solvent dependent.

Multibranched triarylamine end-capped oxime esters as visible-light absorbing type I photoinitiators for free radical photopolymerization

“…In addition, no PL emission intensity was observed for TPA-DP and TPA-PT compounds probably because of the more twisted diphenylamine unit in TPA-DP and the photo-induced electron transfer (PET) effect of phenothiazine in TPA-PT . 38,39…”

“…In addition, no PL emission intensity was observed for TPA-DP and TPA-PT compounds probably because of the more twisted diphenylamine unit in TPA-DP and the photo-induced electron transfer (PET) effect of phenothiazine in TPA-PT. 38,39 Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were conducted to examine the thermal properties of the compounds. The TGA thermograms obtained under a nitrogen atmosphere are displayed in Fig.…”

Synthetic Model for FRET Constructed from Covalently Linked Porphyrin Dimers through a Pyrene Bridge

“…In the case of the free base dimer, the J Förster values were found to be lower, with C 6 F 5 -PyDP showing an overlap integral of 1.97 × 10 –13 cm 6 mmol –1 . These values were found to be comparable to the J Förster of other D–A systems containing porphyrins. − Finally, the rate of Förster energy transfer ( k Förster ) was calculated using the equation k normalF normalö normalr normals normalt normale normalr = 8.8 × 10 23 κ 2 ϕ normalD J normalF normalö normalr normals normalt normale normalr η 4 τ normalD R 6 where ϕ D is the quantum yield of pyrene (0.28), η is the refractive index of dichloromethane (1.424), τ D is the fluorescence lifetime of pyrene (27 ns), and R is the center-to-center distance between the donor and the acceptor obtained from the energy minimized structures (7.49 Å for Mes-PyZnDP and 7.25 Å for C 6 F 5 -PyZnDP). κ 2 is the orientation factor, which is the relative orientation of the donor’s and acceptor’s transition dipole moment and is given by κ 2 = ( sin θ D sin θ A cos ⁡ ϕ − 2 ⁢ cos θ D cos θ A ) 2 where θ D and θ A are the angles made by the donor emission and absorption transition dipoles, with the vector joining the donor and the acceptor and ϕ is the dihedral angle between the two transition dipoles.…”