Synthesis and characterization of N,N′,′N″,Nâ�—-tetrakis(2-aminoethyl)-1,4,8,11-tetra-azacyclotetradecane and its copper(II) complexes

Metal Complexes with Macrocyclic Ligands. Part XXXI. Protonation studies and complexation properties of tetraazamacrocyclic methylenephosphonates with earth‐alkali ions

“…Synthetic work, equilibria measurements, and structural studies have been described for the tetrakisethanol derivatives 7 and 8 which are interesting for their fast rate of metal-ion incorporation [8]. Four aminoethyl groups have also been attached to give the 14-membered macrocycle 9, and a large number of interesting structures of their metal complexes have been published [9]. A tetrakis(propanenitri1e) derivative 10 has been prepared [lo], and it has been shown that the coordinated metal ion can cleave off one of the side chains and/or hydrolyze the nitrile group [l 11.…”

Halide-Ion Encapsulation by a Flexible Dicopper(II) Bis-Tren Cryptate

“…Halide bridging, both in the solid state and in solution, was observed in the dicopper(ii) complex of the very flexible octamine ligand N,N',N'',N'''-tetrakis-(2-aminoethylcyclam). [4,5] Among other bis-tren cryptands containing rigid spacers, we noticed the peculiar behavior of the dicopper(ii) complex of 3, in which the two tripodal tetramine subunits are linked by 2,5-dimethylfuran spacers. In particular, the complex [Cu II 2 (3)(OH)] 3 was isolated and structurally characterized, [6] in which an OH À ion bridges the two metal centers.…”

“…In particular, the most favorable inclusion is observed with the N 3 À ion, which exhibits the correct bite length to position its terminal nitrogen atoms in the vacant coordination sites of the two Cu II centers without inducing any endothermic rearrangement of the polyamine cage. Monoatomic anions such as halides are not encapsulated by the cryptate [Cu II 2 (1)] 4 , even if added in a large excess. Failure to include halide ions seems to be attributable to the mechanical resistence of the rigid cage framework to adjusting its cavity to the size requirements of the monoatomic guest anion.…”

“…The Cu II´´´C u II distance of 3.87 is much smaller than that observed for the complexes [Cu II 2 (1)(X)] 3 (X N 3 À : 6.10 ; NCO À : 6.18 ). Hence, we thought that [Cu II 2 (3)] 4 might be able to encapsulate monoatomic anions of comparable or larger size and exhibit a different selectivity pattern than [Cu II 2 (1)] 4 . We first investigated the formation of the dicopper(ii) cryptate of 3 in aqueous solution by carrying out potentiometric titration experiments on a solution of 3 and Cu II in a 1:2 molar ratio (25 8C, 0.1m NaClO 4 ).…”

“…Figure 3 shows the family of spectra recorded during the titration with chloride ion. The titration profile in the inset corresponds to the formation of a 1:1 inclusion complex, and the log K value for the equilibrium [Cu II 2 (3)] 4 Cl À > [Cu II 2 (3)(Cl)] 3 at pH 5.2, as obtained by a nonlinear least-squares procedure, is 3.98 AE 0.02. The limiting value of the absorption band at 410 nm is especially high (e 12 600 m À1 cm À1 ).…”