Fluorescence properties of halogenated mono-hydroxyl corroles: the heavy-atom effects

Abstract

A series of mono-hydroxyl corrole bearing a fluorine (1), chlorine (2), bromine (3) and iodine (4) atom on its 10-phenyl group have been synthesized. Fluorescence spectroscopy shows that the halogen atom at meso-phenyl group of corroles exhibit significant heavy-atom effect on their photo physical properties. Fluorescence quantum yields and the lifetime of these corroles decrease with the increasing of the atomic weight of halogen atoms. The quenching of the fluorescence could be interpreted in terms of a heavy atom-induced increase in intersystem crossing from S 1 to T 1 . The intersystem crossing rate constant of these corroles were also determined by transient fluorescence spectra.

Synthesis, photophysical properties and spectroelectrochemical characterization of 10-(4-methyl-bipyridyl)-5,15-(pentafluorophenyl)corrole

“…[33(a)], the presence of halogen atoms could increase the ISC process, as well as f T ; proportionally to the halogen weight as also observed in porphyrins, but that is not significant here (see CASSCF results) [34,35]. One explanation for the high IC is that the electron-withdrawing of the perfluorination of phenyl groups increases the non-planar distortion of the macrocycle, accelerates the rate of decay from S 1 !…”

“…One explanation for the high IC is that the electron-withdrawing of the perfluorination of phenyl groups increases the non-planar distortion of the macrocycle, accelerates the rate of decay from S 1 ! S 0 , which competes with ISC mechanism [34,35]. A summary of the photophysical data for corrole 2 dissolved in DCM is shown on Table 1.…”

Photophysical properties and singlet oxygen generation ofmeso-iodinated free-base corroles

“…The detailed experimental procedure for the synthesis of A 2 B free-base corroles were discussed elsewhere. 24,26 We have adopted the same method for the synthesis of our targeted compounds. Corroles 1, 2 and 3 were well characterized by MS, 1 H-NMR and 19 F-NMR (see ESI 1 †).…”

“…We found that the ISC rate constant k isc increased in the order F < Cl < I. 23,24 We also compared free-base corroles with a different number of -C 6 F 5 (F 0 , F 5 , F 10 , F 15 ) at meso-positions. The order of k ISC is F 0 C < F 5 C < F 10 C > F 15 C. It indicates that the electron-withdrawing effect of uorophenyl substitutions, together with the heavy atom effect, inuences the photophysical properties of excited states of corroles.…”

Current Developments in Using MESO-(TETRA) Substituted Porphyrins for PDT

“…37) indicated the usual heavy atom effect on the intersystem crossing (ISC). 119 Note, the long wavelength absorption of these corroles is much stronger than that of TPP, which can aid PDT. …”