Metal-ligand charge transfer transition MLCT

The electronic spectra of the rigid-rod polymers are quite interesting. Strong MLCT (metal-ligand charge transfer) transitions are seen in their optical spectra. 

To substitute the strongly bound axial CO ligand of the ruthenium or osmium center, it is necessary to employ more drastic conditions than simple stirring at room temperature. Imamura (11,20) used photolysis to synthesize porphyrin trimers on the basis of simultaneous coordination of two 4-pyridyl porphyrins to the same ruthenium porphyrin (12, Fig. 3). Some interesting photophysical behavior was observed for these systems. The trimers have an extra UV-Vis absorption band at about 450 nm which is ascribed to metal-ligand charge transfer (MLCT), a d7r(Ru(II))-7r (OEP) transition. This band shows a batho-chromic shift in more polar solvents, and decreased in intensity when... 

The colour formed on mixing the two solutions, of magnesium and haem, arises from a charge-transfer bond. The resultant spectrum contains a broad, intense band that we call a metal-to-ligand charge transfer transition, or MLCT for short. 

Fig. 2 Qualitative MO diagram for Fe(CO)j. There are many allowed ligand-field (LF) and metal-ligand charge-transfer (MLCT) transitions that can occur. Selection rules mean that one-photon population of A 2 states is allowed, two-photon population of and states is allowed, while both one- and two- photon population of states is allowed and the spectra may overlap...

In the parallel investigation of systems where metal-ligand charge-transfer (MLCT) occurs, studies into transition metal complexes of the redox-active quinone ligand have unravelled crossover behaviour that accompanies electron transfer. This reversible process, known as valence tautomerism, has been observed with bistability in the solid state. ° Exotic photomechanical behaviours, such as the bending of crystals of ID chain materials with IR irradiation,have been attributed to the unique structural consequences of electron transfer within the solid. 

MLCT Metal-to-Ligand Charge Transfer Transitions ... 

Class 3—Metal to ligand (oxidation) charge-transfer transitions (MLCT)... 

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