Журнал "Макрогетероциклы"

Arseniy A. Otlyotov,^@1 Vladimir V. Veretennikov, Anton P. Merlyan, Evgeny N. Ivanov, Yana E. Filippova, Yuriy A. Zhabanov,^@2 and Mikhail K. Islyaikin^@3 

Institute of Macroheterocycles, Ivanovo State University of Chemistry and Technology (ISUCT), 153000 Ivanovo, Russian Federation

^@1Corresponding author E-mail: arseney_otlyotov@mail.ru

^@2Corresponding author E-mail: zhabanov@gmail.com

^@3Corresponding author E-mail: islyaikin@isuct.ru

DOI: 10.6060/mhc190443o

Macroheterocycles 2019 12(2) 209-214

Seventeen tautomeric structures of hemihexaphyrazine were considered using DFT in B3LYP/pcseg-2 approximation. The tautomer of D_3h symmetry was found to be the most energetically favorable, and transformations into other tautomers are practically forbidden by high energy barriers (more than 50 kJ·mol^-1). The energetics of hydrogen bonding was estimated by NBO and QTAIM calculations and the preferable D_3h tautomer turned out to possess the lowest total hydrogen bond stabilization energy, according to the results of the NBO-analysis. Aromaticity of the D_3h and C_3h tautomers of hemihexaphyrazine and its thiadiazole annulated analogue was described with use of three popular descriptors: NICS, HOMA and FLU. Tautomeric preference and structural features of the both molecules were found to be very similar.