Theoretical study on thermal cis-to-trans isomerization of BF2-coordinated azo compounds of the para-substitution with electron donating groups

• Thermal cis-trans isomerization of few azo compounds have been investigated.
• There are inversion mechanism and rotation mechanism for these compounds.
• The electron donation groups change the isomerization reaction parameters.
• Calculated half-lives are in qualitative agreement with experimental values.

Thermal cis→trans isomerization for a series of BF2-coordinated azo compounds of the para-substitution with electron donating groups have been systematically investigated. The density-functional theory calculations exhibited good performance to provide better understanding of the effects of para-substitution with electron donating groups. It is found that the different electron donation groups can significantly affect the absorption spectra, the energy levels of molecular orbitals, the transition properties for the trans isomers, the rate constants and the half-lives for the thermal cis→trans isomerization. Our calculated half-lives for the thermal cis→trans isomerization are in qualitative agreement with the experimental values. Specifically, we have evaluated the thermal rate constants at 294 K. The relationship between the thermal isomerization and the para-substituted electron-donating group reveals that the inversion mechanism is preferred for the substituent species while the rotation mechanism is more favorable for non-para-substituent molecule.

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