Synthesis and structures of zinc complexes with new binucleating ligands containing alkoxide bridges, and their activities in the hydrolysis of tris(p-nitrophenyl)phosphate

Four new binucleating ligands featuring a hydroxytrimethylene linker between two coordination sites (1,3-bis{N-[3-(dimethylamino)propyl]-N-methylamino}propan-2-ol, HL1; 1,3-bis{N-[2-(dimethylamino)ethyl]-N-methylamino}propan-2-ol, HL2; 1,3-bis[bis(2-methoxyethyl)amino]propan-2-ol, HL3; and 1-bis[(2-methoxyethyl)amino]-3-{N-[2-(dimethylamino)ethyl]-N-methylamino}propan-2-ol, HL4) were synthesized, along with the corresponding zinc complexes. The structures of three dinuclear zinc complexes ([Zn2L1(μ-CH3COO)2]BPh4 (1), [Zn2L3(μ-CH3COO)2]BPh4 (3), and [Zn2L4(μ-CH3COO)(CH3COO)(EtOH)]BPh4 (4)) and a tetranuclear zinc complex ({[Zn2L2(μ-CH3COO)]2(μ-OH)2}(BPh4)2 (2)) were revealed by X-ray crystallography. Hydrolysis of tris(p-nitrophenyl)phosphate (TNP) by these zinc complexes in an acetonitrile solution containing 5% Tris buffer (pH 8.0) at 30 °C was investigated spectrophotometrically and by 31P NMR. Although zinc complexes 1, 3, and 4 did not show hydrolysis activity, the tetranuclear zinc complex 2, containing μ-hydroxo bridges, was capable of hydrolyzing TNP. This suggests that the hydroxide moiety in the complex may have an important role in the hydrolysis reaction.

Graphical abstractThe structures of three dinuclear zinc complexes ([Zn2L1(μ-CH3COO)2]BPh4 (1), [Zn2L3(μ-CH3COO)2]BPh4 (3), and [Zn2L4(μ-CH3COO)(CH3COO)(EtOH)]BPh4 (4)) and a tetranuclear zinc complex ({[Zn2L2(μ-CH3COO)]2(μ-OH)2}(BPh4)2 (2)) were revealed by X-ray crystallography. The tetranuclear zinc complex 2, containing μ-hydroxo bridges, was capable of hydrolyzing TNP.Figure optionsDownload full-size imageDownload as PowerPoint slide