A Beneficial Effect of Bromination on the Photophysical and Photochemical Properties of Aza-BODIPY Dyes with Electron-Donating Groups

A series of aza-BODIPY dyes substituted with meta-(dimethylamino)phenyl groups were synthesized and their spectroscopic, photophysical, and electrochemical properties were compared. Highly desirable photophysical and photochemical properties were induced in meta-(Me2N)Ph-substituted aza-BODIPY by br...

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Bibliographic Details
Published inAsian journal of organic chemistry Vol. 8; no. 10; pp. 1879 - 1892
Main Authors Obloza, Magdalena, Lapok, Lukasz, Pedzinski, Tomasz, Nowakowska, Maria
Format Journal Article
LanguageEnglish
Published WEINHEIM Wiley 01.10.2019
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
HIGHLY FLUORESCENT
TETRAARYLAZADIPYRROMETHENE
EXCITED-STATE
electrochemistry
PHOTODYNAMIC THERAPY
BF2-AZADIPYRROMETHENES
DONOR
PHOTOSENSITIZER
CHEMOSENSOR
aza-BODIPY
singlet oxygen
CONJUGATED POLYMERS
sensitizers
excited triplet state
AZADIPYRROMETHENES
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Summary:A series of aza-BODIPY dyes substituted with meta-(dimethylamino)phenyl groups were synthesized and their spectroscopic, photophysical, and electrochemical properties were compared. Highly desirable photophysical and photochemical properties were induced in meta-(Me2N)Ph-substituted aza-BODIPY by bromination of the aromatic rings at the 3 and 5 positions. In particular, high values of singlet oxygen quantum yields (phi(Delta)) were measured, ranging from 0.36 to 0.58. The photosensitized oxygenation process of a model compound - diphenylisobenzofuran (DPBF) - proceeds via a Type II mechanism for the di-bromo derivative, while for the tetra-bromo derivative a mixed mechanism involving both O-1(2) and other reactive forms of oxygen formation (Type I and/or Type III) was detected. Nanosecond laser photolysis experiments of the brominated aza-BODIPYs revealed T-1 -> T-n absorption spanning from ca. 350 nm to ca. 510 nm with the triplet lifetimes (tau(T)) ranged between 15.6 mu s and 26.0 mu s. The brominated aza-BODIPYs studied exhibited an absorption band within the so-called "therapeutic window", with lambda(abs) located between 620 nm and 636 nm. As estimated by CV/DPV measurements, the meta-(Me2N)Ph-substituted aza-BODIPYs studied exhibited a multi-electron oxidation processes at a relatively low oxidation potentials (E-ox), pointing to the very good electron-donating properties of these molecules. All compounds studied exhibited extremely high photostability and thermal stability.
ISSN:2193-5807
2193-5815
DOI:10.1002/ajoc.201900385