Macrocyclic dinuclear Zn(II) complexes: synthesis, structure and hydrolysis of tris( p-nitrophenyl) phosphate

Abstract

A series of mono- and dinuclear zinc complexes of 3,6,9,17,20,23-hexaaza-29,30-dihydroxy-13,27-dimethyl-tricyclo[23,3,1 11,15]triaconta-1(28),11,13,15(30),25,26-hexaene (H 2L or BDBPH) have been defined in solution by potentiometry. The crystal structure of [Zn 2C 26H 40N 6O 2(CH 3OH) 2]·Br 2 has been determined by X-ray. Each zinc ion is coordinated to three nitrogen atoms, a bridged-phenolic oxygen atom, and a methanolic oxygen atom, which define a six-coordinated octahedron. Bond lengths of ZnN are in the range of 2.104(3)–2.120(3) Å and distances between Zn and O (bridged-phenolic oxygen) are 2.052(2), 2.062(2) Å, respectively. The dinuclear complexes: [Zn 2L] 2+ and [Zn 2L(OH)] + play crucial roles in hydrolytic reaction of tris(4-nitrophenyl)phosphate. A possible mechanism showed that [Zn 2L(OH)] + acts as a nucleophile and [Zn 2L] 2+ stabilizes the formation of the intermediate: [Zn 2L–BNP].