Premium
Ultrafast Spectroscopy of Hydroxy‐Substituted Azobenzenes in Water
Author(s) -
Steinwand Sabrina,
Halbritter Thomas,
Rastädter Dominique,
OrtizSánchez Juan Manuel,
Burghardt Irene,
Heckel Alexander,
Wachtveitl Josef
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201501863
Subject(s) - chemistry , tautomer , enol , keto–enol tautomerism , photochemistry , isomerization , excited state , aqueous solution , spectroscopy , ground state , computational chemistry , stereochemistry , organic chemistry , quantum mechanics , nuclear physics , catalysis , physics
Ultrafast UV/Vis pump/probe experiments on ortho ‐, meta ‐ and para ‐hydroxy‐substituted azobenzenes (HO‐ABs), as well as for sulfasalazine, an AB‐based drug, were performed in aqueous solution. For meta ‐HO‐AB, AB‐like isomerisation behaviour can be observed, whereas, for ortho ‐HO‐AB, fast proton transfer occurs, resulting in an excited keto species. For para ‐HO‐AB, considerable keto/enol tautomerism proceeds in the ground state, so after excitation the trans ‐keto species isomerises into the cis form. Aided by TD‐DFT calculations, insight is provided into different deactivation pathways for HO‐AB, and reveals the role of hydroxy groups in the photochemistry of ABs, as well as their acetylation regarding sulfasalazine. Hydroxy groups are position‐specific substituents for AB, which allow tuning of the timescale of thermal relaxation, as well as the amount and contribution of the keto species to photochemical processes.