Abstract

In our studies aimed to produce new chemicals used in weed control, 2-methyl-1,5-diarylpentadienones were synthesized by the reaction of p-methoxybenzaldehyde, p-nitrobenzaldehyde and p-N,N-dimethylbenzaldehyde, respectively, with 2-butanone, resulting in four model compounds. The phytotoxicity of these compounds against wheat coleoptiles and Sesame seedling was observed at pM concentrations, indicating good potential for their usage in weed management in the field. Spectroscopic and computational studies were performed in order to gain understanding on their mechanisms of action and to clarify some structural complexities due existence of conformers and substituent effects. These compounds probably act as hydroxyphenylpyruvate dioxygenase inhibitors. The tested compounds were characterized by spectroscopic and single crystal X-ray diffraction analyses. Solid crystalline state of the compound A (2-Methyl-1-(p-methophyphenyl)-5-(phenyl)-diarylpentadienone) is observed in the monoclinic space group P2(1)/c with unit cell dimensions a = 14.3366(4) angstrom, b = 113788(4) angstrom, c = 9.6319(3)angstrom , beta = 96.596, V = 1560.88(9) angstrom(3) and Z = 4. Compound C (2-Methyl-1-(p-methophypheny1)-5-(pnitropheny1)-diarylpentadienone) crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 17.8276(9) angstrom, b = 7.3627(4) angstrom, c = 12.9740(6) angstrom, beta = 107.6230(10), V = 1623.04(14) angstrom(3) and Z = 4. LC-UV-MS analysis furnished important data helpful for their characterization. The spectroscopic data and computational (DFT) analysis revealed the fact that each of the compounds A-D occurs in solution as four conformers. (C) 2017 Elsevier B.V. All rights reserved.