Spectroscopic manifestations of the intramolecular hydrogen bond in ordinary and sterically hindered porphyrins

Spectroscopic manifestations of the intramolecular hydrogen bond (IHB) in ordinary and sterically hindered porphyrins were investigated by the methods of IR spectroscopy and molecular modeling. It is shown that the IHB plays a part in the formation of the νNH and γNH vibrations of porphyrins. By changing the type and value of the distortion of the macroring at the expense of steric effects of interaction of volumetric substituents, the parameters and spectroscopic manifestations of the IHB can be varied in a significantly larger range as compared with ordinary tetrapyrroles having nearly quadratic and planar macrorings.