Strength of interaction between Bader's atomic basins, enclosed by zero-flux surfaces of electron distribution, was proposed to be a measure of elastic deformation of an interaction. The set containing 53 atomic aggregate and covering all range of interaction strength (from van der Waals interactions to triple covalent bonds) was calculated by DFT and perturbation theory methods. Further analysis was performed to seek correlations between various local quantities based on electron density and effective force constants of stretching diatomic vibrations. The linear trend between effective force constants and the potential energy density at the (3, -1) critical point of electron distribution was found. This correlation was improved by the integration of the potential energy density over an interbasin zero-flux surface of electron density. Simple mechanical explanation of established trends is presented. The correlations can be further used to at least semiquantitatively compare any pair of interactions between Bader's atomic basins.

Radiolabeled macrocyclic zinc complexes are more stable in serum than analogous copper compounds; an azacrown-derived cycle with five heteroatoms coordinates zinc, providing fast complexation and high in vivo stability.

The complexation properties towards Bi 3 + of benzoazacrown ligands with five (H 3 BA3A) and six (H 4 BATA) heteroatoms and corresponding number of acetic arms have been investigated. Complexation constants were determined via potentiometric titration for BA3ABi complex (logβ = 26.2) and refined for BATABi complex (logβ = 31.7). According to NMR, X-ray and EXAFS results, chelation of cation by H 3 BA3A appears to be outside the macrocyclic cavity both in the solid state and in the aqueous solution. This out-cage location despite the high stability constant causes serum and in vivo instability of complex of smaller azacrown H 3 BA3A in contrast to H 4 BATA. Whereas the larger macrocycle and four pendant arms of H 4 BATA provide long-range coordination effectively shielding the cation thereby ensuring high inertness in vitro, low accumulation of the radionuclide in the organs, and fast clearance.

Two series of regioisomeric heterylmethylidene derivatives of imidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazines and imidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazines were synthesized. Several compounds exhibiting high antiproliferative activity were found.