New bifunctional H₄dota-like ligands with three acetic acid and one phosphinic acid pendant arms and propionate (H₅do3ap^PrA) or 4-aminobenzyl (H₄do3ap^ABn) reactive groups bound to the phosphorus atom were investigated. Potentiometric studies showed that the ligands have a similar basicity to the parent H₄dota and the stability constants of their complexes with sodium(I) and selected lanthanide(III) ions are also similar. Formation and acid-assisted decomplexation kinetics of yttrium(III) complexes with a series of H₄dota-like ligands (H₄dota and its phosphinic/phosphonic acid analogues) were studied and the reactions are sensitive to a slight modification of the ligand structure. The (2-carboxyethyl)phosphinic acid derivative H₅do3ap^PrA and the phosphonic acid ligand H₅do3ap form complexes faster than H₄dota. The most kinetically inert complex is that with H₄do3ap^ABn. Rates of complexation and decomplexation can depend on the ability to transfer proton(s) outside/inside the complex cavity and, therefore, on the hydrophobicity of the ligands. The results demonstrate that the new bifunctional ligands are suitable for labelling biomolecules with yttrium(III) radioisotopes for utilization in nuclear medicine.

Solution properties of complexes of a new H₄dota-like ligand containing three acetate and one methylphosphonate pendant arms (H₅do3ap, H₅L) were studied. The ligand exhibits a high last dissociation constant (pK_A = 13.83) as a consequence of the presence of phosphonate moiety. In solution, successive attachment of protons leads to several reorganizations of protonation sites and the neutral zwitterionic species H₅do3ap has the same solution structure as in the solid state, where the nitrogen atom binding methylphosphonate and the opposite nitrogen atoms are protonated. Stability constants with Na⁺ and trivalent lanthanide ions (La³⁺, Ce³⁺, Eu³⁺, Gd³⁺, Lu³⁺) and Y³⁺ have been determined. The constants are comparable or higher than those of H₄dota due to the higher overall basicity of H₅do3ap. Formation of the stable protonated complexes, as well as complexes with the L:M = 1:2 stoichiometry, was proved. Formation and decomplexation kinetics of the Ce³⁺ and Gd³⁺ complexes were investigated. The mechanism of formation of the H₅do3ap complexes is similar to that observed for H₄dota complexes and the complex species with mono- or diprotonated ligand on the cyclen ring are considered as the reaction intermediates. Acid-assisted decomplexation of H₅do3ap complexes is faster in comparison with those of H₄dota. This is caused by higher basicity of the phosphonate pendant arm and the ring nitrogen atoms, which facilitates the proton transfer from the bulk solution to the nitrogen atoms of cyclen ring.

Three new coordination polymers based on CuI and 2,3-dimethylpyrazine (2,3-dmpyz) were prepared, structurally characterized and investigated for their thermal and luminescence properties. In the ligand rich 2 : 3 compound [(CuI)₂(2,3-dmpyz)₃] 1 (CuI)₂ dimers are found, which are connected by the N-donor ligands into chains, whereas in the structure of the 1 : 1 intermediate [(CuI)(2,3-dmpyz)] 2 (CuI)₄ tetramers are found, which are also connected into chains. The crystal structure of the ligand deficient 2 : 1 compound [(CuI)₂(2,3-dmpyz)] 3 is built up of CuI double chains, which are connected by the 2,3-dmpyz ligands into layers. Thermal decomposition of 1 results in its direct transformation into the ligand deficient compound 3, without the formation of the 1 : 1 compound 2 as an intermediate. A similar thermal reactivity is found for compound 2, which transforms into 3 on heating. Stirring of a crystalline suspension of pure 1 or 2 in acetonitrile, always leads to a transformation into the ligand deficient compound 3 indicating that compound 3 is the most stable of all the coordination polymers, whereas compounds 1 and 2 are metastable. The luminescence properties of the CuCl and CuI coordination polymers were investigated at 298 and 77K. It was observed that the emission maxima strongly depends on the nature of the halide atom and the composition and structure of the coordination polymers. In addition, several of these compounds show luminescence thermochromism. These results are compared with those obtained for the previously reported CuCl and CuBr(2,3-dimethylpyrazine) coordination polymers.