COMPLEXES WITH MACROCYLIC LIGANDS

Formation and dissociation kinetics of nine Ni(II)-macrocyclic tetra-thiaether complexes (eight macrocyclic, one linear in acetonitrile) have been compared with those for Cu(II) analogues and for Ni(II) complexes with macrocylic tetramines (262). Whereas for the tetramine complexes conformational changes may be apparent in the kinetics this is not the case for the tetrathiaether complexes, where there is no kinetic evidence for slow conformational changes after initial bonding of the ligand to... 

In recent years numerous macrocyclic square planar complexes have been prepared with various donor atoms and one or more transition metals. None of these complexes have been shown to exhibit extended metal-metal bonding. The physical properties of square planar phthalocyanine complexes have been the most extensively studied of these materials. The macrocylic planar dianionic phthalocyanine ligand forms numerous planar complexes with almost every transition metal (31,318). Crystallographically, the complexes stack in... 

Due to their large size, the inclusion of rare-earth metals into phthalocyanines leads to neutral, double-decker, bis(phthalocyaninato)lanthanide(III) complexes.In these compounds, the triva-lent lanthanide(III) ion is sandwiched between the two macrocyclic ligands, with the rings being rotated with respect to each other by 45°. The coordination polyhedron corresponds to a distorted square antiprism due to the non-equivalent bending deformations of both macrocyles... 

Figure 5.4. Electronic spectra of the hexaaza-macrocyle-H2 (free ligand) in DMF, (a) under N2. (b) under CO2. [HAM-H2] 5 x 10 5 M. [PTBA] = 0.01 M. registered at OPC. Reprinted from Figure 4 M. Isaacs, J.C. Canales, A. Riquelme, M. Lucero, M.J. Aguirre and J. Costamagna, Contribution of the ligand to the electro-reduction of CO2 catalyzed by a cobalt(II) macrocylic complex. Journal of Coordination Chemistry 56(14), 1193-1201 (2003). With permission of Taylor and Francis (http //www.tandf.co.uk/joumals)...

The group of R. Weiss (254) and the group of J.-M. Lehn (255) from Strasbourg in collaboration with S. J. Lippard from Columbia University have developed in 1979 new bimetallic copper models based on macrocylic complexes. The first group synthesized the following elongated macrocyclic ligand that can bind two Cu(I) or Cu(II) ions. 

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