Metal-ligand interaction, concepts

In 1923 the American chemist G.N. Lewis provided a broad definition of acids and bases, which covered acid-base reactions not involving the traditional proton transfer an acid is an electron-pair acceptor (Lewis acid) and a base is an electron-pair donor (Lewis base). The concept was extended to metal-ligand interactions with the ligand acting as donor, or Lewis base, and the metal ion as acceptor, or Lewis acid. 

S.H. Koenig and R.D. Brown (1995) in Handbook of Metal-Ligand Interactions in Biological Fluids, ed. G. Berthon, vol. 2, p. 1093, Dekker, New York - Relaxiv-ity of MRI magnetic contrast agents. Concepts and principles . 

The angular overlap approach has also been used as a component in a more mathematically sophisticated approach to metal-ligand interactions, the ligand field molecular mechanics (LFMM) method, which has applications to a variety of concepts discussed in this chapter. ... 

Recently, the basic concept of self-healing metallopolymer networks was improved. For this purpose, the Schubert group utilized cadmium(ll)-bis-terpyridine complexes [101]. A metallopolymer network based on these complexes was synthesized by the addition of cadmium acetate. The authors could show that these materials behave completely different due to a different coordination of the metal center. Presumably, the acetate moiety also coordinates to the cadmium, but this metal-ligand interaction is much weaker, which results in an improved self-healing behavior (Fig. 7). 

Catalano et al. reported the synthesis and characterization of a new series of Pd°-based metallocrypates that bind Tl1 ion in the absence of attractive ligand interactions through metal-lophilic connections. The cationic species have been characterized by a variety of methods and have considerable stability. From the solid-state structural data it is apparent that interaction of the metal atoms with one another is the dominant bonding interaction within the metallocryptate cavity. The characterization of complexes supports the concept of metallophilic behavior as a fundamental component of bonding in closed-shell systems. These materials may ultimately serve as prototypical systems for detection of closed-shell ions 946... 

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