Metal complexes of macrocyclic ligands. Part XXIII. Synthesis, properties, and structures of mononuclear complexes with 12‐ and 14‐membered tetraazamacrocycle‐N,N′,N″,N‴‐tetraacetic Acids

Abstract

The two tetraazamacrocycle-N.N',N",N"'-tetraacetic acids H,dota and H,teta form with Ni2+, Cu2+, and Zn2+ (M") mononuclear complexes MLH, and M'[ML], M' being an alkaline earth ion. The structures of Ni(H2dota) and Cu(H,dota) have been solved by X-ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N-atoms and two carboxylates. In the case of Cu2+, the distortions are more pronounced than for Ni2+ indicating that the Juhn-Teffer effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.

Lanthanide complexes of macrocyclic derivatives useful for medical applications

“…Some X-ray crystal structures confirm this point, such as in [Cu(ac 3 py14)] - [18] and in [Co(ac 3 py14)] [18], in which the six-coordination is completed with two oxygen atoms from contiguous acetate arms. This is also the case of [M(dota)] 2-and [M(teta)] 2-(M = Cu 2+ or Ni 2+ ) [19][20][21][22] where the metal centers adopt an octahedral geometry with the four nitrogen atoms of the macrocycle forming the equatorial plane and two oxygen atoms from opposed acetate arms occupying the axial positions, leaving the two other arms free and pointing away from the coordination sphere. In contrast, lanthanide ions generally form complexes with higher coordination numbers, such as in [Eu(dota)(H 2 O)] - [23] and [Gd(dota)(H 2 O)] - [24] or [Tb(teta)] - [25] and [Eu(teta)] - [26], for which single-crystal X-ray structures were reported.…”

Unexpected Sensitivity of sst2 Antagonists to N-Terminal Radiometal Modifications

“…This conclusion can be reached from the affinity of Cu-DOTA-JR11, which is also low (IC 50 , 16 6 1.2 nM), and the coordination chemistry of Cu(II)-DOTA, which is similar to that of Ga (III)-DOTA. The geometry is pseudooctahedral and hexacoordinate, and one can strongly assume that in solution the carboxymethyl amide function is acting as a spacer (24)(25)(26).…”

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

“…[10] In the mononuclear Cu II complex with the tetraaza ligand DOTA, the metal ion exists in a distorted octahedral geometry, coordinated to all ring nitrogen atoms and to two (opposite) carboxylate oxygen atoms; the other two carboxylate groups are protonated. [11] The two coordinated oxygen and two nitrogen atoms (in the trans positions in the macrocycle) occupy the equatorial positions, while the other two nitrogen atoms are axially bound. The axial bonds are elongated, as expected from the Jahn-Teller effect, but this elongation is not as pronounced as in other copper(II) complexes, probably as a consequence of steric constraints imposed by the cyclic structure of the ligand.…”

“…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.…”