Triphenylamine corrole dyads: Synthesis, characterization and substitution effect on photophysical properties

Investigating the role of corrole as an excitation energy relay in light-induced processes in closely connected N,N'-bis(biphenyl-4-yl)aniline functionalized corrole donor-acceptor dyad

A photosynthetic antenna-reaction center model, BBA-PFCor comprised of N,N'-bis(biphenyl-4-yl)aniline (BBA) covalently functionalized to bis(pentafluoro)corrole moiety has been prepared and the contribution of the BBA as the photoinduced energy transfer antenna was investigated. UV-visible studies have shown that integrating the electron-rich BBA chromophore into the corrole core has broadened the soret band of the corrole moiety with the absorption spanning from 300 to 700 nm. Electrochemical studies, in corroboration with the computational calculations, revealed that, BBA moiety can act as an electron reservoir and, in the excited state, it would transfer the excited energy to the corrole moiety in the dyad. Steady-state fluorescence studies have demonstrated that, upon photoexcitation of the BBA moiety of BBA-PFCor at 310 nm in solvents of varied polarity, the BBA emission centered at 400 nm was observed to be quenched, with the concomitant appearance of the corrole emission from 500 to 700 nm, indicating the happening of photoinduced energy transfer (PEnT) from 1BBA* to corrole moiety. Parallel control experiments involving the excitation of the corrole moiety at 410 nm did not result in the diminishing of the corrole emission, suggesting that the quenching of the BBA emission in BBA-PFCor is majorly due to intramolecular PEnT from 1BBA* to corrole moiety leading to the formation of singlet excited corrole, that is, 1BBA*-PFCor ➔ BBA-1PFCor*. The free energy changes of PEnT, ΔGEnT, were found to be thermodynamically feasible in all the solvents used for the study. Parallel time-resolved fluorescence studies were congruent with the steady-state fluorescence results and provided further evidence for the occurrence of ultrafast PEnT from 1BBA*➔corrole in the dyad with the rates of energy transfer (kEnT) of ~108 s-1.

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

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.

Axially substituted phosphorous(v) corrole with polycyclic aromatic hydrocarbons: syntheses, X-ray structures, and photoinduced energy and electron transfer studies

Excited state energy and electron transfer processes in naphthalene and pyrene appended phosphorous(v) corroles.