A new series of chromium(II)-alkylphosphonates, Cr[RPO3]·H2O (R = CH3, C2H5), and chromium(II) ethylenebis(phosphonate), Cr2[O3P−(CH2)2−PO3]·3H2O, have been synthesized by reaction of CrCl2 and the corresponding phosphonic acid in water in the presence of urea. The (2-aminoethyl)phosphonic acid reacts with CrCl2 to give an unexpected compound of formula Cr[H3N−(CH2)2−PO3(Cl)]. All the compounds are sensitive to the air, except for the latter one. They were characterized by X-ray powder diffraction, thermogravimetry, and UV−visible and infrared spectroscopy, and their magnetic properties were studied by a SQUID magnetometer. The metal ion is in the high-spin d4 configuration, and it appears to have an octahedral coordination. Cr[CH3PO3]·H2O behaves as a “weak” ferromagnet, with a Nèel temperature of TN = 35 K, and it represents an example of an unusual kind of molecular-based magnetic material, having a finite zero-field magnetization. The thermal variation of the magnetic susceptibility of Cr2[O3P−(CH2)2−PO3]·3H2O follows the Curie−Weiss law, with a large negative Weiss constant of θ = −73 K. Below 100 K, the susceptibility increases until a peak at TN = 15 K is observed, and this is associated to the three-dimensional antiferromagnetic order. Cr[H3N−(CH2)2PO3(Cl)] is paramagnetic down to 5 K.

The formation constants of the binary and ternary complexes formed in solution of Pb2+, Co2+, Ni2+, Cu2+, Cd2+, Ce3+ and UO22+ with N-(2-acetamido)-iminodiacetic acid (H2ADA) and salicylic acid derivatives [thiosalicylic (TSA) and 3,5-dinitrosalicylic acid (DNSA)] have been determined pH-metrically at t = 25 ± 0.1 °C and ionic strength μ = 0.1 mol dm-3 (KNO3) The stability of the different complexes formed are discussed in terms of the nature of the ligands and metalions. The mixed ligand complexes of the type [M2+(ADA)(TSA)] (M2+ = Co2+, Ni2+, Cu2+) were synthesized and characterized.

The visible electronic spectra of the title hydroxyazo compound (abbreviated as HAI) in a number of organic solvents have been studied. It was found that in dilute solutions in basic solvents, HAI exists in an acid-base equilibrium of the type HAIgH+ + AI−. The proportional concentration of the conjugate base (AI−) in the medium is largely dependent on the HAI concentration, the basicity of the organic solvent and the tendency of stabilization of the AI− form through H-bond interaction with the solvent molecules. The low energy visible band of both the HAI and AI− forms are assigned to a transition involving the whole solute molecule associated with intramolecular CT character. The effect of time on the longer wavelength visible band of HAI has been investigated.

The visible electronic spectra of the title hydroxyazo compound (abbreviated as HAI) in a number of organic solvents have been studied. It was found that in dilute solutions in basic solvents, HAI exists in an acid-base equilibrium of the type HAIgH+ + AI−. The proportional concentration of the conjugate base (AI−) in the medium is largely dependent on the HAI concentration, the basicity of the organic solvent and the tendency of stabilization of the AI− form through H-bond interaction with the solvent molecules. The low energy visible band of both the HAI and AI− forms are assigned to a transition involving the whole solute molecule associated with intramolecular CT character. The effect of time on the longer wavelength visible band of HAI has been investigated.