Issue 21, 2021

Impact of iodine loading and substitution position on intersystem crossing efficiency in a series of ten methylated-meso-phenyl-BODIPY dyes

Abstract

Four core and six distyryl-extended methylated-meso-phenyl-BODIPY dyes with varying iodine content were synthesized. The influence of iodine loading and substitution position on the photophysical properties of these chromophores was evaluated. Selective iodine insertion at the 2- and 6-positions of the methylated-meso-phenyl-BODIPY core, rather than maximum iodine content, resulted in the highest intersystem crossing efficiency. Iodination of the distyryl-extended BODIPY core afforded intersystem crossing quantum yields comparable to 2,6-diiodo-BODIPY. Inclusion of an iodine at the para–meso-phenyl position generally enhanced non-radiative decay in the BODIPY excited-state, leading to lower fluorescence and intersystem crossing quantum yield values. Iodine substitution at the styryl-positions resulted in negligible changes to the excited-state dynamics. This study highlights: (1) the rate of radiative decay is similar in all ten derivatives (on the order of 1 × 108 s−1), (2) iodination of the 2,6-positions results in the greatest enhancement of intersystem crossing efficiency, (3) care must be taken when modifying the para–meso-phenyl position as it could have detrimental effects on the excited-state dynamics, (4) the excited-state is negligibly affected by iodination of the styryl groups, potentially enabling orthogonal functionalization without modifying the molecular photophysics, (5) distyryl extension of the chromophore core diminishes rates of non-radiative decay and intersystem crossing, resulting in higher fluorescence quantum yields and lower intersystem crossing yields in the π-extended derivatives compared to the core BDP derivatives, and (6) DFT calculations provide insight into the electronic and structural factors regulating intersystem crossing and vibrational relaxation in these molecules.

Graphical abstract: Impact of iodine loading and substitution position on intersystem crossing efficiency in a series of ten methylated-meso-phenyl-BODIPY dyes

Supplementary files

Article information

Article type
Paper
Submitted
12 Nov 2020
Accepted
22 Apr 2021
First published
26 Apr 2021

Phys. Chem. Chem. Phys., 2021,23, 12033-12044

Impact of iodine loading and substitution position on intersystem crossing efficiency in a series of ten methylated-meso-phenyl-BODIPY dyes

J. T. Ly, K. F. Presley, T. M. Cooper, L. A. Baldwin, M. J. Dalton and T. A. Grusenmeyer, Phys. Chem. Chem. Phys., 2021, 23, 12033 DOI: 10.1039/D0CP05904H

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