Combined effect of hydrogen bonding interactions and freezing of rotameric equilibrium on the enhancement of photostability. Issue 19 (2nd May 2018)

• Record Type: Journal Article
• Authors: Golec, Barbara; Nawara, Krzysztof; Gorski, Alexandr; Thummel, Randolph P.; Herbich, Jerzy; Waluk, Jacek
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 19(2018)
• Page Start: 13306
• Page End: 13315
• Publication Date: 2018-05-02
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp00726h
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Rigid structure and hydrogen-bonding interactions provide a higher photostability of organic chromophores. Abstract : The photophysics and photostability of 12, 13-dihydro-5 H -indolo[3, 2- c ]acridine (IA ), a rigid bifunctional indole derivative with proton donor/acceptor functionalities, can be drastically changed by the environment. The formation of hydrogen bonds with alcohols leads to a significant decrease of the triplet formation efficiency and an increase of photostability. The photodegradation yield was found to be about two hundred times lower in methanol and 1-propanol than in n -hexane or acetonitrile. A similar effect has been reported for two indole-naphthyridines, molecules that can exist in syn and anti rotameric forms. We demonstrate thatIA, which can exist only in the syn form, is more photostable in alcohols than similar, but non-rigid molecules. This additional photostability enhancement is due to the elimination of a slower channel of excited state deactivation in alcohol complexes, S0 ← S1 internal conversion. The dominant, faster channel of S1 depopulation is the excited state double proton transfer, manifested by the presence of low energy tautomeric fluorescence.