Журнал "Макрогетероциклы"

Dmitriy V. Belykh^a@ and Alexander L. Stolypko^b 

^aInstitute of Сhemistry of Komi Scientific Centre of Ural Branch of Russian Academy of Sciences, 167000 Syktyvkar, Russian Federation

^bPitirim Sorokin Syktyvkar State University, 167001 Syktyvkar, Russian Federation

^@Corresponding author. E-mail: belykh-dv@mail.ru

 

DOI: 10.6060/mhc213945b
Macroheterocycles 2021 14(3) 209-213

 

Using the DOSY method, the equilibrium constants (K_c) for the formation – decomposition of molecular associates for a number of porphyrins and chlorins with a water molecule in the C₆D₆ medium were determined. K_c and the proportion of porphyrin-bound water were determined experimentally from the dependences of the self-diffusion coefficients D on the diffusion time t_m , D(t_m ). The formation of water-porphyrin associates is a necessary condition for proton exchange between porphyrin and water in the C₆D₆ medium. It was established that the ability of the studied macroheterocyclic compounds to form associates with water molecules due to the formation of intermolecular hydrogen bonds, as a rule, increases with an increase in the deviation from the planarity of the macrocycle and, consequently, an increase in the steric accessibility of intracyclic NH groups and nitrogen atoms. The obtained data indicate that the K_c value in the absence of substituents capable of forming hydrogen bonds in the studied macroheterocyclic compounds can be used as an independent criterion for assessing the nonplanarity of the macrocycle in addition to the currently existing structural, spectral and computational methods, as well as to the data obtained in the study of other model reactions.