cis–trans Isomerisation of Substituted Aromatic Imines: A Comparative Experimental and Theoretical Study

Abstract

The cis-trans isomerisation of N-benzylideneaniline (NBA) and derivatives containing a central C=N bond has been investigated experimentally and theoretically. Eight different NBA molecules in three different solvents were irradiated to enforce a photochemical trans--(hnu)-->cis isomerisation and the kinetics of the thermal backreaction cis--(Δ)-->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.

Photoinduced Orientation of Photoresponsive Polymers with N-Benzylideneaniline Derivative Side Groups

“…The lowest-energy absorption band (λ max = 332 nm) is dominated by a HOMO−LUMO (π−π*) transition, while the second lowest-energy absorption (λ max = 283 nm) corresponds to a transition from the lower-lying occupied orbital to the π* (LUMO) orbital; these transitions have been theoretically and experimentally investigated in NBA derivatives that assume nonplanar conformations. 38 Figures S3a,b). For a P1 film, the absorption of CN (1621 cm −1 ) decreases, while a new absorption due to CHO stretching appears at 1684 cm −1 .…”

Imine‐Functionalized Triazatriangulenium Platforms: Towards an Artificial Ciliated Epithelium

“…We propose the reverse assignment:a na ctive surface propelling ap assive load. Upon irradiation, simple imines perform such non-reciprocal motion.I ti s known that the photochemical trans-cis isomerization proceeds through ar otation aroundt he C=Nd ouble bond, [4][5][6][7] whereas the thermalb ack-reactionm echanism is an inversion at the nitrogen atom via al inear transition state. Whip-like structures protruding from the cell wall (flagellao rc ilia) providing motility probably emerged more than 2billion years ago [2] and are prevalent in higher organisms.…”

Photoinduced reorientation and polarization holography in a new photopolymer with 4-methoxy-N-benzylideneaniline side groups

“…18 Several studies have investigated the photochemical behavior of BA derivatives in solution. [18][19][20] Because BA derivatives are structurally similar to a Author to whom correspondence should be addressed. Electronic mail: kawatuki@eng.u-hyogo.ac.jp azobenzene derivatives, an axis-selective photoreaction should occur in the solid state.…”

“…1(c)). [18][19][20] Therefore, photoisomerization is the main part of the photoreaction during the initial stage of the photoirradiation, but further exposure results in both photoisomerization and other photoreactions, such as photocrosslinking. Detailed analyses of the photoreaction of the P1 film are in progress.…”