In:
Zeitschrift für Naturforschung B, Walter de Gruyter GmbH, Vol. 55, No. 12 ( 2000-12-1), p. 1141-1152
Abstract:
The synthesis of (Dien)Pt(PMEA-N7), where Dien = diethylenetriamine and PMEA 2- = dianion of 9-[2-(phosphonomethoxy)ethyl]adenine, is described. No useful biological activity could be discovered for this complex which is in contrast to the known antiviral properties of PMEA itself. The acidity constants of the twofold protonated H 2 [(Dien)Pt(PMEA-N7)] 2+ complex were determined (UV spectrophotometry and potentiometric pH titration): The release of the proton from the -P(O) 2 (OH) - group is only slightly affected by the N7-coordinated (Dien)Pt 2+ unit, whereas the acidity of the (N1)H + site is strongly enhanced. The stability constants of the M[(Dien)Pt(PMEA-N7)] 2+ complexes with the metal ions M 2+ = Mg 2+ , Ca 2+ , Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , and Cd 2+ were measured by potentiometric pH titrations in aqueous solution at 25 °C and I = 0.1 M (NaNO 3 ). Application of previously determined straightline plots of log K M(R-PO3) M versus K H(R-PO3) H for simple phosph(on)ate ligands, R-PO 3 2- where R represents a non-inhibiting residue without an affinity for metal ions, proves that the primary binding site of the complex-ligand, (Dien)Pt(PMEA-N7), with all the metal ions studied is the phosphonate group; in most instances the expected stability is actually reduced by about 0.4 log units due to the N7-bound (Dien)Pt 2+ unit. Only for the Cu[(Dien)Pt(PMEA-N7)] 2+ and the Zn[(Dien)Pt(PMEA-N7)] 2+ systems the formation of some 5-membered chelates involving the ether oxygen atom of the -CH 2 -O-CH 2 -PO 3 2- residue could be detected; the formation degrees are 52 ± 9% and 32 ± 14%, respectively. The metal ion-binding properties of (Dien)Pt(PMEA-N7) differ considerably from those of PMEA 2- , yet they are relatively similar to those of pyrimidine-nucleoside 5'-monophosphates. The structures of the various complex species in solution are discussed and compared.
Type of Medium:
Online Resource
ISSN:
1865-7117
,
0932-0776
DOI:
10.1515/znb-2000-1207
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
2000
detail.hit.zdb_id:
2078109-X
detail.hit.zdb_id:
124635-5
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