Synthesis and biological acitivities of N-alkyl derivatives of o-,m-, and p-nitro (E)-4-azachalcones and stereoselective photochemistry in solution, with theoretical calculations

The N-alkyl derivatisation and photochemical dimerisation of 3 o-, m-, and p-nitro substituted 4-azachalcones (1-3) yielded 3 new o-, m-, and p-nitro substituted (.E)-N-decyl-4-azachalconium bromides, (2E)-1-(2-nitrophenyl)-3-(N_decyl-4-pyridmium bromide)-2-propen-1-one (4), (2E)-1-(3-nitrophenyl)-3-(N-decyl-4-pyridinium bromide)-2-propen-1-one (5), and (2E)-1-(4-nitrophenyl)-3-(N-decyl-4-pyridinium bromide)-2-propen-1-one (6), and 3 new dimers in solution, $(1\beta,2\alpha)$-di-(3-nitrobenzoyl)-$(3\beta,4\alpha)$-di-(4-pyridinyl)cyclobutane (7), $(1\beta,2\alpha)$-di-(4-nitrobenzoyl)-$(3\beta,4\alpha)$-di-(4-pyridinyl)cyclobutane (8a), and $(1\beta,2\alpha)$-di-(4-nitrobenzoyl)-$(3\beta,4\alpha)$-di-(4-pyridinyl)cyclobutane (8b), stereoselectively. The monomeric compounds showed good antimicrobial activity against test micro-organisms. The most sensitive microorganisms were Gram-positive bacteria. The monomers also showed high antioxidant activity, while the dimerisation products 7-8a,b were less active. Compound 6 was found to have similar or even higher activity when compared to the standard antipxidants Trolox and vitamin C, respectively. The possible dimerisation products of compounds 1-3 were calculated theoretically. Experimental and theoretical calculations showed that 5-truxinic type dimer is the most stable isomer.