COMPARATIVE STRUCTURAL STUDIES OF 4-DIAZOPYRAZOLE DERIVATIVES BY X-RAY DIFFRACTION AND THEORETICAL INVESTIGATION

摘要

The X-Ray crystal and molecular structures of the 4-pyrazol derivatives 3-methyl-4-diazo-5-benzamido-1H-pyrazole (4) and 3-benzamido-5-methyl-1H-pyrazole (3) have been determined.A dimeric structure has been found for the first and polymeric for the second.A comparison of 4 with 1,3-dimethyl-4-diazo-5-benzamido-1H-pyrazole (2) shows differences in the geometrical parameters of the pyrazole ring due to electron delocalization in 2 consequent to the nitrogen negative charge in the latter.Theoretical investigation at the density functional theory (DFT) level shows difference in the molecular electronic distribution of 2 and 4,in agreement with the structural parameters and the IR stretching frequencies of the respective carbonyl moieties.