Photochemical stability of the inclusion complexes formed by modified 1,4-dihydropyridine derivatives with beta-cyclodextrin.

The results of studies of photochemical stability of the derivatives of 1,4-dihydropyridine (NR) are reported. The NR with various substituents (-NO2, -Cl, -F, CF3) at different positions in the phenyl ring were identified by UV spectrophotometry. Photodegradation of NR in the inclusion complexes with beta-cyclodextrin (beta-CD) was studied in the liquid phase. The rate of photodegradation of NR derivatives was dependent on the position of -NO2 group in the phenyl ring; for the ortho isomer it is ten times higher than for the meta one. The rate of photodegradation of 2-NO2-NR (ortho isomer) in inclusion complex with beta-CD was 200 times slower than that for this compound in the crystal phase. In the case of halogeno- and cyanoderivatives, the presence of beta-CD caused a 4-fold increase in the photodegradation rate.