Structural studies and investigation on the activity of imidazole-derived thiosemicarbazones and hydrazones against crop-related fungi

Abstract

New imidazole derived thiosemicarbazones and hydrazones were prepared by condensation of 4(5)-imidazole carboxaldehyde, 4-(1H-imidazole-1-yl)benzaldehyde and 4-(1H-imidazole-1-yl)acetophenone with a thiosemicarbazide or hydrazide. All compounds were characterized by quantitative elemental analysis, IR and NMR techniques. Eight structures were determined by single crystal X-ray diffraction. The antifungal activities of the compounds were evaluated. None of the compounds exhibited significant activity against Aspergillus flavus and Candida albicans, while 4(5)-imidazolecarboxaldehyde thiosemicarbazone (ImT) and 4-(1H-imidazole-1-yl)benzaldehyde thiosemicabazone (4ImBzT) were highly and selectively active against Cladosporium cladosporioides. 4(5)-Imidazolecarboxaldehyde benzoyl hydrazone (4(5)ImPh), 4(5)-imidazolecarboxaldehyde-para-chlorobenzoyl hydrazone (4(5)ImpClPh), 4(5)-imidazolecarboxaldehyde-para-nitrobenzoyl hydrazone (4(5)ImpNO2Ph), 4-(imidazole-1-yl)acetophenone-para-chloro-benzoyl hydrazone (4ImAcpClPh) and 4-(imidazole-1-yl)acetophenone-para-nitro-benzoylhydrazone (4ImAcpNO2Ph) were highly active against Candida glabrata. 4(5)ImpClPh and 4(5)ImpNO2Ph were very effective against C. cladosporioides. In many cases, activity was superior to that of the reference compound nystatin.

Figure 1

Generic representation for imidazole-derived thiosemicarbazones.

Figure 2

Molecular plots of ImT∙H₂O (1a), ImTPh (2), 4ImBzT (3), 4ImBzTM (4) and 4ImBzTPh (5), showing the labeling scheme of the non-H atoms and their displacement ellipsoids at the 50% probability level.

Figure 3

Generic representation for imidazole-derived hydrazones.

Figure 4

Molecular plots of 4(5)ImpClPh∙H₂O (11a), 4ImBzPh (14) and 4ImBzpClPh (15), showing the labeling scheme of the non-H atoms and their displacement ellipsoids at the 50% probability level.