Add time:08/11/2019         Source:sciencedirect.com

The article summarizes the results of our research on branched network of Provitamin D photo-isomerization in various media using UV absorption spectroscopy. The focus is on the microenvironment effect on the efficiency of Previtamin D cis-trans photoisomerization. Solvent polarity has a negligible effect in homogeneous solutions. In some inhomogeneous media a significant suppression of this undesirable side photoreaction of Previtamin D was detected. The result is discussed in accordance with the well known concept of ground state conformation control in trienes photochemistry. Unexpected increase of trans-isomer formation under UV irradiation is observed in liquid crystalline matrices as compared to the photoreaction in solvents. It indicates a change in the photoreaction pathway or mechanism of Previtamin D cis-trans isomerization. The results of further detailed temperature and concentration studies suggest that the ordering of a liquid-crystalline medium contributes to the increased efficiency of cis-trans isomerization due to the collective nature of process.

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