Synthesis, Stability, and Crystal Structure Studies of Some Ca2+, Cu2+, and Zn2+ Complexes of Macrocyclic Polyamino Carboxylates

Study of Copper(II) Polyazamacrocyclic Complexes by Electronic Absorption Spectrophotometry and EPR Spectroscopy

“…This decrease in axial interaction may be caused either by substitution of one axial ligand by a solvent molecule, or simply by breaking of an axial ligand bond with formation of a five-coordinate square-pyramidal structure. The latter hypothesis is supported by the similarity between the EPR parameters of the system under discussion and those of Cu II square-pyramidal complexes with the macrocyclic ligands [12]aneN 4 , [36] 1,4,7,10-tetrabenzyl-2,5,8,11-tetraethyl-1,4,7,10-tetraazacyclododecane [39] and 7,11-bis(carboxymethyl)-1,4-dioxa-7,11-diazacyclotridecane. [40] Cu/DOTA: The EPR spectrum of [Cu(DOTA)] 2-in aqueous solution was previously obtained by other authors at pH 9 for a metal-to-ligand ratio of 1:2, [8] and the reported parameters are included in Table 2.…”

“…The spectra of the complexes with DOTP are significantly different from those with DOTA, implying distinct structures for these complexes in solution. However, the d-d band for Cu/DOTP is in the same energy range as that of the corresponding copper(II) complex with the ligand [12]aneN 4 , which has a square-pyramidal geometry in solution, with the four ring nitrogen atoms defining the equatorial plane and one axial position occupied by a solvent molecule. [36] The present results support a similar structure for the Cu/DOTP complex, in which the axial position of the pyramid is probably occupied by an oxygen from one phosphonate side-arm, in analogy with the solid state geometry reported for the copper(II) complex with the similar ligand N,N',N'',N'''-tetrakis(2-diphenylphosphorylethyl)-1,4,7,10-tetraazacyclododecane.…”

“…Furthermore, even though there is a reported EPR study on the Cu II /DOTA system, [8] the effect of the pH on the EPR pattern of these macrocyclic complexes in aqueous solution was never investigated. The solid-state structures of Cu II complexes with NOTA, [9] NOTP, [10] DOTA, [11] and analogous tetraazamacrocyclic ligands, [12][13][14][15][16][17][18][19][20] have been obtained by X-ray diffractrometry.…”

Long-term retention of gadolinium in the skin of rodents following the administration of gadolinium-based contrast agents

“…To assess the pharmacokinetic parameters of GBCAs, Omniscan, Magnevist, MultiHance and Gadovist were [8], b [9], c [9,10], d [2], e [11], f [12], g [13], h calculated from [14], i calculated from [15], j calculated from [16,17], k calculated from [18], l calculated from [19] injected once at a dose of 2.5 mmol/kg b.w. into the tail vein, and blood samples were taken from the cannulated carotid vein at various time-points p.i.…”

Gd-Complexes of DTPA-bis(amides) Functionalized by Pyridine and Picolinamide: Synthesis, Thermodynamic Stability, and Relaxivity Properties

“…17 The K' Sel have been shown to correlate with the experimental LD 50 value. 21 The thermodynamic stability constant reveals the extent of complexation at the given pH. The stability constants of the complexes have been evaluated using equation (3), where K n H (n = 1, 2, 3, etc) are the stepwise protonation constants of the ligands.…”