Crystal structure of the 3-D complex [(H2O)Cd(μ-3,4-TDTA)Cd(H2O)]. Potentiometric and 113Cd NMR studies in aqueous solution (3,4-TDTA = 3,4-toluenediamine-N,N,N ′,N ′-tetraacetate)

Holo- and Hemidirected Lead(II) in the Polymeric [Pb4(μ-3,4-TDTA)2(H2O)2]·4H2O Complex. N,N,N‘,N‘-Tetraacetate Ligands Derived from o-Phenylenediamines as Sequestering Agents for Lead(II)

“…In the [PbHL]complex, the Pb(II) is less shielded than in the [PbL] 2complex, and the binding of the H + to the ligand will decrease its electron density available for donation and for shielding the Pb(II), in a way similar to that observed in Cd(II)/4-Cl-o-PhDTA complexes. 27 The values of the chemical shifts are in good agreement with those reported for the Pb(II) complexes of the amido derivatives of the ethylenediaminetetraacetic acid (EDTA) 45 (δ ) 2189 and 2441), keeping in mind that the lead resonance of a 1.0 mol dm -3 aqueous solution of Pb(NO 3 ) 2 appears -2961 upfield from neat Pb(CH 3 ) 4 . 46 The crystal structure of the lead(II) ethylenediaminetetraacetamide complex, reported in ref 45, presents a Pb(II) environment very similar to that observed for Pb(1) in compound 1 (Figure 2), a six-coordinated hemidirected lead(II) being surrounded by two nitrogen and four oxygen atoms in both complexes.…”

“…For the Pb(II)/4-Cl-o-PhDTA system direct potentiometry at millimolar concentrations gave a good result. These ligands have previously been studied with other metals 27,28 27 As can be seen in the species distribution diagrams (Figure 3) the main species are the monomeric ones. However, due to the large size of lead ion and its ability to have a variable coordination number, more than one ligand molecule can be bound to the metal, forming ligand-rich species.…”

“…This may indicate that the second ligand is only bound to the metal via carboxylato groups as was observed for Cd(II) complexes. 27 Another feature of these ligands is that the carboxylato groups already bound to a metal ion, forming the [ML] 2species, are able to join another metal, generating the [M 2 L] species. These species were first observed for Cd(II) 27 and now are also observed for Pb(II).…”

“…27 Another feature of these ligands is that the carboxylato groups already bound to a metal ion, forming the [ML] 2species, are able to join another metal, generating the [M 2 L] species. These species were first observed for Cd(II) 27 and now are also observed for Pb(II). The values of the stability constants of the formation of those species (eq 5) are log K ) 1.71(5), 2.2(1), and 1.8(1) for 4-Cl-o-PhDTA, o-PhDTA, and 3,4-TDTA, respectively.…”

Estudio de especiación química de los fármacos antiinflamatorios tenoxicam y piroxicam con cationes metálicos de interés biológico

“…La terapia de quelación es el método más utilizado para luchar contra la contaminación por metales tóxicos o esenciales en exceso (5,17) . Actualmente, se ha tenido éxito en conseguir buenos agentes secuestrantes para diferentes iones tóxicos como Be(II) (18)(19)(20) , el esencial en exceso Fe(III) (21,22) , Cd(II) (22,23) y Pb(II) (24) . Dada su importancia biológica y sus implicaciones farmacéuticas, se ha incrementado el interés en la química de coordinación de ligandos durante las últimas décadas.…”