Antonio Matilla-Hernández

Hydrolytic species of the ion cis-diaqua(ethylenediamine)palladium(II) complex and of cis-dichloro(ethylenediamine)palladium(II): fitting its equilibrium models in aqueous media with or without chloride ion

Thermodynamic data for equilibria involved int he overall hydrolytic process of the cis-[Pd(en)(H2O)2]2+ complex in the presence or absence of chloride ion are reported. All expected hydrolytic species are taken into account to calculate their formation constants and to fit the equilibrium model. The formation constants (log βpqr) of aqua and/or hydroxo complexes were obtained from E(H+) data of alkalimetric titrations of cis-[Pd(en)(H2O)2](ClO4)2 solutions. The log βpqr balues of chloro-containing complexes were obtained from E(H+) and E(Cl−) data pairs, taking into account the above log β data as fixed values. All formation constants were fitted by SUPERQUAD calculations: log βpqr for cis-aqua-hydroxo (cis=10−1, −6.68(10))), di-μ-hydroxo (20−2, −7.758(4), cis-dihydroxo (10−2, −14.523(4)), cis-dichloro (120, 5.24(1)), cis-chloro-aqua (110, 3.18(1)) and cis-chloro-hydroxo (11−1, −3. 75(4)) specieis for I=0.15 mol dm−3 in NaClO4 and t=37°C. This constant set allows good simulation of experimental titration curves and is used to obtain a variety of species distribution diagrams.

Copper(II) and nickel(II) chelates with dihydrogen Trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetate(2−) ion (H2CDTA2−). Synthesis, XRD structure and properties of [Cu(H2CDTA)]·H2O and [Ni(H2CDTA)(H2O)·4H2O

Abstract Stoichiometric reactions of metal hydroxycarbonates with the acid trans -1,2-cyclohexanediaminotetraacetic acid (H 4 CDTA) in water under reduced pressure yielded [Cu(H 2 CDTA)]·H 2 O ( I ) and [Ni(H 2 CDTA) (H 2 O)]·4H 2 O ( II ). Both compounds were characterized by TG-DTA analysis, spectral properties (IR, reflectance and RSE) and X-ray diffraction. In I the copper(II) atom exhibits a distorted square-base coordination (type 4+1) by chelation of one H 2 CDTA 2− ligand through two N and two O (carboxylate) at the square base and one O (carboxylic) at the apex of the coordination polyhedron; a second carboxymethyl group of H 2 CDTA 2− remains free. In II the H 2 CDTA 2− chelating ligand also plays a quinquedentate role, but one water molecule achieves the slightly distorted octahedral coordination of the nickel(II) atom. Appropriate comparisons with the structure of [M(H 2 EDTA)(H 2 O)] (M = Ni, Cu complexes suggest that the steric constraints in the H 2 CDTA ligand promotes the distorted five-coordination of the Cu II chelate in I as well as the hydration of the nearly octahedral Ni II derivative ( II ). The double protonation of the ligand H 2 CDTA 2− is carried out over different kinds of chelate rings, G and R, for Cu II and Ni II M(CDTA) derivatives, respectively (where G and R, indicate metal-glycinate rings nearly coplanar or perpendicular to the plane MNN, respectively).

Structural insights on the molecular recognition patterns between N(6)-substituted adenines and N-(aryl-methyl)iminodiacetate copper(II) chelates.

For a better understanding of the metal binding pattern of N(6)-substituted adenines, six novel ternary Cu(II) complexes have been structurally characterized by single crystal X-ray diffraction: [Cu(NBzIDA)(HCy5ade)(H2O)]·H2O (1), [Cu(NBzIDA)(HCy6ade)(H2O)]·H2O (2), [Cu(FurIDA)(HCy6ade)(H2O)]·H2O (3), [Cu(MEBIDA)(HBAP)(H2O)]·H2O (4), [Cu(FurIDA)(HBAP)]n (5) and {[Cu(NBzIDA)(HdimAP)]·H2O}n (6). In these compounds NBzIDA, FurIDA and MEBIDA are N-substituted iminodiacetates with a non-coordinating aryl-methyl pendant arm (benzyl in NBzIDA, p-tolyl in MEBIDA and furfuryl in FurIDA) whereas HBAP, HCy5ade, HCy6ade and HdimAP are N(6)-substituted adenine derivatives with a N-benzyl, N-cyclopentyl, N-cyclohexyl or two N-methyl groups, respectively. Regardless of the molecular (1-4) or polymeric (5-6) nature of the studied compounds, the Cu(II) centre exhibits a type 4+1 coordination where the tridentate IDA-like chelators adopt a mer-conformation. In 1-5 the N(6)-R-adenines use their most stable tautomer H(N9)adenine-like, and molecular recognition consists of the cooperation of the CuN3(purine) bond and the intra-molecular interligand N9H···O(coordinated carboxy) interaction. In contrast, N(6),N(6)-dimethyl-adenine shows the rare tautomer H(N3)dimAP in 6, so that the molecular recognition with the Cu(NBzIDA) chelate consist of the CuN9 bond and the N3H···O intra-molecular interligand interaction. Contrastingly to the cytokinin activity found in the free ligands HBAP (natural cytokinin), HCy5ade and HCy6ade, the corresponding Cu(II) ternary complexes did not show any activity.

Coordinating ability of the acetate ion towards cis-(1,3-diamine-2-hydroxypropane)palladium(II) chelate units in aqueous solutions. Preliminary study about the possibility of the acetato ligand to be involved in complex formation equilibria with palladium(II)-based anticancer drugs

Abstract Cis-dichloro(1,3-diamino-2-propanol)palladium(II), cis-[Pd(dapol)Cl2], reacts with stoichiometric amounts of AgClO4 to give chloride free solutions of cis-[Pd(dapol)(H20)2](ClO4)2 (compound 1). Twelve mixed compound I/acetic acid (AcOH) solutions having three different I/AcOH molar ratios and/or total molar complex concentration have been titrated with NaOH 0.1 mol dm−3 at 37°C and I = 0.15 mol dm−3 (NaClO4). Formation constants (log βpqr) of mixed hydroxoacetato complexes were fitted for the equilibrium: pPdL(H2O)2 + gAcO − rH ⇄ (PdL)p (AcO)q (H2O)2-r (OH)r using the log β of acetate ion protonation (also determined) and the corresponding log βpqr data for aqua- and/or hydroxo-complexes previously reported (as fixed values). New calculations were performed by the HYPERQUAD program. Simulated and experimental titrations agree well. Several distribution diagrams are used to show that acetate ions prevent the alkaline hydrolysis of compound I to a lesser extent than they do chloride ions. Both chloride and acetate ions could compete but also contribute to preventing such hydrolysis in weakly acid or nearly neutral solutions. These findings also apply inside cells at physiological conditions (pH = 7.2–7.4 and [Cl−] ∼4 mM) for a total molar complex concentration of ∼1 mM in which compound I could react with DNA and related biopolymers @ 1998 Elsevier Science B.V All rights reserved.