Spectral peculiarities of isomeric trans-styrylpyrazoles
The regularities in the electronic absorption spectra of trans-styrylpyrazoles were interpreted on the basis of quantum-chemical calculations by the Pariser-Parr-Pople configuration-interaction (PPP CI) method and data from the photoelectron spectra taking into account the peculiarities of the formation of the boundary molecular orbitals of pyrazole. The difference in the electronic effects of the isomeric pyrazolyl radicals determines the degree of polarization of the ethylene fragment and the C-C bonds of the pyrazole ring in the styrylpyrazole molecules; this is reflected in their IR spectra.