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cis – trans Isomerisation of Substituted Aromatic Imines: A Comparative Experimental and Theoretical Study
Author(s) -
Luo Ying,
Utecht Manuel,
Dokić Jadranka,
Korchak Sergey,
Vieth HansMartin,
Haag Rainer,
Saalfrank Peter
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100179
Subject(s) - isomerization , chemistry , density functional theory , transition state theory , computational chemistry , photochemistry , excitation , spectroscopy , thermal , kinetics , reaction rate constant , thermodynamics , organic chemistry , physics , catalysis , quantum mechanics
The cis – trans isomerisation of N ‐benzylideneaniline (NBA) and derivatives containing a central CN bond has been investigated experimentally and theoretically. Eight different NBA molecules in three different solvents were irradiated to enforce a photochemical trans ${{\mathop \rightarrow \limits ^{h\nu }_{}}}$ cis isomerisation and the kinetics of the thermal backreaction cis ${{\mathop \rightarrow \limits ^{\Delta }_{}}}$ trans were determined by NMR spectroscopy measurements in the temperature range between 193 and 288 K. Theoretical calculations using density functional theory and Eyring transition‐state theory were carried out for 12 different NBA species in the gas phase and three different solvents to compute thermal isomerisation rates of the thermal back reaction. While the computed absolute rates are too large, they reveal and explain experimental trends. Time‐dependent density functional theory provides optical spectra for vertical transitions and excitation energy differences between trans and cis forms. Together with isomerisation rates, the latter can be used to identify “optimal switches” with good photochromicity and reasonable thermal stability.