Premium
New Perspectives on an Old Issue: A Comparative MS‐CASPT2 and OM2‐MRCI Study of Polyenes and Protonated Schiff Bases
Author(s) -
Dokukina Irina,
Marian Christel M.,
Weingart Oliver
Publication year - 2017
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12833
Subject(s) - protonation , excited state , chemistry , computational chemistry , multireference configuration interaction , maxima and minima , conjugated system , quantum , ab initio , chemical physics , configuration interaction , atomic physics , physics , quantum mechanics , mathematics , organic chemistry , polymer , ion , mathematical analysis
Polyenic systems are involved in light perception of numerous living organisms. Although a π ‐conjugated backbone is a common feature of all polyenes, their photophysics may vary. We provide a comparative quantum mechanical study of low‐lying S 1 and S 2 excited states in short (3‐5 double bonds) symmetric all ‐trans linear polyenes and corresponding protonated Schiff bases. In our investigation, we use the well‐established ab initio multireference CASPT2 approach and benchmark the efficient semiempirical OM2‐MRCI approach against it. For all protonated Schiff bases, MS‐CASPT2 results in two distinct S 1 minima with inverted and noninverted bond length pattern, respectively. We find that OM2‐MRCI is a computationally affordable and reliable alternative to MS‐CASPT2 for investigations of polyenic systems, particularly when highly demanding calculations (e.g. excited‐state dynamics) need to be performed.