Abstract
Solution studies (pH and
1H NMR titrations) on Zn
2+ 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 p
K
a 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](ClO
4)
2
1 and [L1Zn(DETP)](ClO
4)
3, DETP
−=
O,
O-diethyl thiophospate. Compound
1 consists of a monomeric cation and ClO
4
−
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.
Solution studies on zinc(II) complexes
1 and
2 derived from
N′
,N″
,N″′-tris(3-aminopropyl)amine L1 and
N′
,N″
,N″′-tris(3-dimethylaminopropyl)amine L2 have been carried out to investigate the evidence for the protonation/deprotonation of the Zn(II)-bound water molecule. The crystal structure determination of [L1Zn(DETP)](CIO
4)
3 showed the direct evidence for the finding of the hydrolysis product,
O,
O-diethyl thiophosphate (DETP
−) which play an essential role in the hydrolytic reaction mechanism.