Design of mononuclear, binuclear and polynuclear molybdenum(VI) complexes based on ONO benzoylacetone derived enaminones and their in vitro biological activity

Abstract

Molybdenum(VI) complexes of different nuclearity, mononuclear, [MoO2(L1 or 2)(MeOH)]·MeOH (1·MeOH and 2·MeOH), [MoO2(L1 or 2)(D)] [D = pyridine, (1a and 2a), 3-methylpyridine, (1b and 2b) and 4-methylpyridine, (1c and 2c)], binuclear [{MoO2(L1 or 2)}2(D)] (D = 4,4′-bipyridine (1d, 1d′ and 2d), and polynuclear complexes [MoO2(L1 or 2)]n (3 and 4) were synthesized by solution based reactions of enaminones (H2L1 = 3-(2-hydroxy-4-methylphenylamino)-1-phenylbut-2-en-1-one; H2L2 = 3-(2-hydroxy-5-methylphenylamino)-1-phenylbut-2-en-1-one) with the dioxobis(acetylacetonato)molybdenum(VI) complex, [MoO2(acac)2]. Reactions of the mononuclear complexes 1·MeOH and 2·MeOH with pyridine and its derivatives resulted in corresponding mononuclear [MoO2(L1 or 2)(D)] or binuclear [{MoO2(L1 or 2)}2(D)] complexes. In case of [{MoO2(L1)}2(4,4-bpy)] two polymorphic forms are obtained (1d and 1d′). The cross-linked transformations of [MoO2(L1 or 2)(D)] complexes in solution or when exposed to vapors of N-heterocyclic bases have been explored. Crystal and molecular structures of ten complexes (1·MeOH, 2·MeOH, 1a–d, 1d′, 2b–d) were determined by the single-crystal X-ray diffraction analysis. Enaminone ligands and their molybdenum complexes were characterized by elemental and TG analysis, IR and NMR spectroscopy and screened for their in vitro cytotoxic and antibacterial activities. None of the tested compounds showed cytotoxic ability against THP-1 and HepG2 cell lines. Compounds 1·MeOH, 1b, 2·MeOH, 2a and 3, exhibited weak antibacterial activity on Moraxella catarrhalis strain while other complexes did not show antibacterial properties towards Staphylococcus aureus, Enterococcus faecalis and Escherichia coli bacteria.