Trischelate complex

Fig. 8. Schematic representation of intercalation into a DNA groove for an octahedral trischelated complex [adapted from Barton JK, Danishefsky AT, Goldberg JM (1984) J. Am. Chem. Soc. 106 2172]...

Trischelate complexes exist in enantiomeric configurations A and A about the metal atom and the process of inversion (interconversion of enantiomers) is of considerable interest. When the metal ions are of the inert type, it is often possible to resolve the complex then the process of racemization can be followed by measurement of optical rotation as a function of time. Possible pathways for racemization fall into two broad classes those without bond rupture and those with bond rupture. 

Figure 1-12 Three possible modes of intramolecular race-mization of a trischelate complex, (a) trigonal twist, (b) rhombic twist, (c) one of several ring-opening paths.

The jS-diketones are a versatile class of ligand with many known modes of coordination, some of which are shown in Figure 3. 0,0 -chelation (11) of the monoanion is by far the most common mode, being found for almost all of the metallic and metalloid elements. Compounds of the stoichiometry M(dike)3 and M(dike)2 are the most common. The former generally have an almost octahedral distribution of the six oxygen atoms when M is a main group or transition metal. These compounds have been used extensively in studies of the mechanism of the racemization of trischelate complexes. 

Several rare exceptions to the general luminescence behavior of heavy-atom molecules described above have recently been reported. It has been found that hetero-trischelated complexes of Rh(III) with 2,2 -... 

Fig. 7.4 D3 trischelate complex orientation of the twofold axes on the positive hemicircle in the (x y ) plane...

Another interesting finding regarding the chirality of trischelate complexes is that the heUcity of the metal coordination sphere can be transferred to the periphery of the coordinated ligands in two different ways. In complexes with bidentate ligands such as dithiolenes, catecholato, and dithiocarbamato, the chirality is attenuated as one moves away from the central metal, whereas for those with... 

These observations indicate that the principle of hierarchical self-assembly of helicates is applicable not only to octahedral trischelate complexes. The reaction is more versatile and can generate new compounds with interesting physical (B fluorescence) or structural (M0O2) features... 

---