Metalloligand approach

In view of the rapid development in the synthesis of metal alkynyl complexes and the inherent advantage of the rigidity of such systems, attempts have been made by researchers to synthesize mixed-valence metal alkynyl [210, 211] and mixed-metal alkynyl complexes [64]. The incorporation of different metal centers to the organic spacer, which is usually achieved by the metalloligand approach, may provide a good handle to investigate the electron transfer and communication across the molecule. Isolation of mixed-valence homometallic species have... 

The robustness of the rhenium(i) diimine alkynyl systems and rich photophysical behavior have rendered them suitable as metalloligands for the synthesis of mixed-metal complexes. It is well-known that organometallic alkynes exhibit rich coordination chemistry with Cu(i), Ag(i) and Au(i) [214-218], however, photophysical properties of these r-coordinated compounds are rare. Recent work by Yam and coworkers has shown that luminescent mixed-metal alkynyl complexes could be synthesized by the metalloligand approach using the rhenium(i) diimine alkynyl complexes as the z -ligand. Reaction of the rhenium(i) diimine alkynyl complex [Re(bpy)(CO)3C=CPh] with [M(MeCN)4]PF6 in THF at room temperature in an inert atmosphere afforded mixed-metal Re(i)-Cu(i) or -Ag(i) alkynyl complexes (Scheme 10.31) [89]. Their photophysical properties have also been studied. These luminescent mixed-metal complexes were found to emit from their MLCT[d7i(Re) —> 7i (N N)] manifolds with emission bands blue-shifted relative to their mononuclear precursors (Table 10.5). This has been attributed to the stabilization of the dTi(Re) orbital as a consequence of the weaker t-donating ability of the alkynyl unit upon coordination to the d metal centers. 

Scheme 1 Metalloligand approach for the construction of two M MOFs. M MOF-3 shows better C2H2/C2H4 gas separation and chiral separation than M MOF-2...

Recently, several groups reported molecular squares prepared by an alternative approach, in which bifunctional metalloligands serve as the linkers thereby placing the metal ions into the walls of the container molecules (114—116). Hupp and coworkers, for example, have designed square-shaped macrocycles based on salen-type components (117). Thus, the molecular square 15 was prepared by the directed assembly of cis- [(PEt3)2Pt(OTf)2] and... 

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