Some boron compounds of semicarbazones: antimicrobial activity and precursor for the sol–gel transformation to nanosized boron oxide

Abstract

Few new boron derivatives of the type [(4-C₆H₄R)C(CH₃)NN:C(NH₂)OB(OC₆H₄O)] were synthesized by the reaction of OC₆H₄OBOPrⁱ and LH [LH = (OH)C(NH₂)NN:C(CH₃)(4-C₆H₄R)], [where R = H(L¹H); CH₃(L²H); OCH₃(L³H); Cl(L⁴H); Br(L⁵H)] in a 1 : 1 molar ratio under toluene reflux. All these newly synthesized complexes were characterized using elemental analysis, and their probable structures were proposed on the basis of IR, ¹H, ¹³C and ¹¹B spectral data and EI mass spectrometry. Antimicrobial activities of the semicarbazone ligands and their boron derivatives were investigated against E. coli and P. aeruginosa bacteria and A. niger and P. peniculosum fungi. B(OPrⁱ)₃ and the boron semicarbazone derivative [(4-C₆H₄Cl)C(CH₃)NN:C(NH₂)OB(OC₆H₄O)] were used as precursors to synthesize nanosized cubic B₂O₃ (A and B) and orthorhombic B₇O (C), respectively, by sol–gel transformation. The average particle sizes of B₂O₃ (A) and (B) and B₇O (C) are ∼9.41 nm, ∼14.87 and ∼16.81 nm, respectively.