Ligation of alkoxymethylimidazoles towards cadmium(II) and zinc(II). X-ray, spectroscopic, thermal and potentiometric investigation

Abstract

The stability constants and structure of the complexes of Cd II and Zn II with 1-ethoxymethylimidazole (ExMeIm), 1-propoxymethylimidazole (PxMeIm), 1-ethoxymethyl-2-methylimidazole (ExMe-2-MeIm) and 1-propoxymethyl-2-methylimidazole (PxMe-2-MeIm) in aqueous solution have been determined by potentiometric methods. Zn II form both tetrahedral and octahedral species with the cited ligands according to the configurational equilibrium type: octahedron $ tetrahedron, but Cd II prefers octahedral coordination of alkoxymethylimidazole complexes in aqueous solution. Retention of the six-coordination form of Cd II has also been confirmed by the data obtained for two novel compounds which have been synthesized in the solid state. The crystal and molecular structure of [Cd(ExMeIm) 4 (NO 3 ) 2 ] (1) has been determined by X-ray diffraction. The coordination geometry around the Cd II ion can be considered as slightly distorted tetragonal bipyramidal (CdN 4 O 2 ). Additionally, another six-coordinate Cd II compound with ethoxymethyl-2-methylimidazole [Cd(ExMe-2-MeIm) 4 (H 2 O)](NO 3 ) 2 (2) has been characterized by spectroscopic (i.r., far i.r., Raman) ES-MS and t.g.a. methods.

A comparison of solution and solid state coordination environments for calcium(II), zirconium(IV), cadmium(II) and mercury(II) complexes with dipicolinic acid and methylimidazole derivatives

“…The titration in the presence of metal ions was stopped when precipitate was observed. The 2-mim forms relative weak complexes with Ca 2+ and Cd 2+ similar to what was seen for other M 2+ cations [26,27], while the complexation between 1-mim and Zr 4+ ion is relatively strong. The interaction for 2-mim/Hg 2+ is similar to imidazole/Hg 2+ [30] and pydc-M n+ systems [12,24,[31][32][33][34] and is relatively strong, except for the pydc-Ca 2+ system.…”

Mononuclear copper(II) nitrato complexes with methyl-substituted 4-nitropyridine N-oxide. Physicochemical and cytotoxic characteristics

“…4). The first step with endothermic effect (DH = 40.79 kJ/mol) was assigned to the release of one water molecule [15,16]. The subsequent steps are related to the degradation of the organic ligands and the remaining NO 3 groups (strong exo effects observed in sharp DTG peak and DSC data (DH = À158.3 kJ/mol).…”

“…coordination or constitution can bring some information on structure of (1). The temperature above or slightly below 100°C (see Section 2) and the magnitude of the endothermic effect (DH = 40.79 kJ/mol, Table 6) is typical for loss of the coordination water molecule [15,16].…”

Systematic coordination chemistry and cytotoxicity of copper(II) complexes with methyl substituted 4-nitropyridine N-oxides

“…The temperature above or slightly below 100°C is typical for loss of weakly bound coordination water molecules [48,49]. Additionally, the DSC data (Table S5) show that the magnitude of the endothermic effect (ΔH = 24.69 kJ/mol (1) and 46.28 kJ/mol (2)) are characteristic for the loss of a coordinated water molecule [48,49]. The subsequent steps between 130 and 500°C correspond to decomposition of the remaining NO 3 group and degradation fragments of the organic ligand (Table S4).…”