Solution studies of N′,N″,N‴ -tris(3-aminopropyl)amine-based zinc(II) complexes and X-ray crystal structures of [Zn(trpn)](ClO4)2 and [Zn(trpn)(DETP)]ClO4, DETP^-=O,O-diethyl thiophospate. Catalytic activity of the complexes in the hydrolysis of the phosphotriester 2,4-dinitrophenyl diethyl phosphate

Solution studies (pH and 1H NMR titrations) on Zn2+ complexes 1 and 2 derived from N′,N″,N‴ -tris(3-aminopropyl)amine L1 and N′,N″,N‴ -tris(3-dimethyl-aminopropyl)amine L2 revealed that the presence of the hydrophobic (methyl) groups attached to the tripodal ligand side arms decreased the pKa of Zn-bound water molecule from 9.99 for 1 to 8.01 for 2, respectively. The X-ray diffraction studies have established the structures [L1Zn](ClO4)2 1 and [L1Zn(DETP)](ClO4) 3, DETP-=O,O-diethyl thiophospate. Compound 1 consists of a monomeric cation and ClO4- counter ions. The coordination geometry of the Zn(II) centers may be described as distorted tetrahedral. Whereas in compound 3 the zinc atom adopts the slightly distorted trigonal-bipyramidal coordination geometry with the three primary nitrogen's on the basal plane and the tertiary nitrogen and the oxygen of DETP- at the apex. The hydroxo complexes [ZnL(OH)]+ species showed slight catalytic activity in the hydrolysis of the phosphotriester 2,4-dinitrophenyl diethyl phosphate. © 2003 Elsevier B.V. All rights reserved.