Metal-ligand charge-transfer transitions

The electronic spectra of allyl complexes (Table 7.4) exhibit relatively low intensity bands due to the d-d ytansitions as well as intense bands resulting from ligand metal and metal ligand charge transfer transitions. In palladium complexes of the type Pd2Cl2(allyl)2, the first three low intensity bands at 29,500 (fi = 543), 34,000 (e = 618), and 40,500 cm (a = 2006) were assigned to the d-d transitions. The two more intense bands at 44,000 cm ( = 5222) and 46,500 cm(8 = 2286) are due to Cl->Pd and Pd allyl electron transfer transitions, respectively. ... 

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. 

Radical cations of bisarene-transition metal complexes are produced relatively easily by oxidation (39). However, since the coordination of a neutral 7r-system to a metal is accompanied by a net metal - ligand charge transfer, the energy of the LUMO is raised upon complex formation, and the electron affinity of the complex decreases (9). Thus, bisbenzenechromium could not be converted to a stable radical anion... 

Intensily colored (near 450 nm) complexes involving Ruthenium (154) and 1,8-naphthyridine and its more basic derivative, 2,7-dimethyl-1,8-naphthyridine, have recently been described.105 The highly colored nature of these complexes has been ascribed to metal-to-ligand charge transfer transitions. 

Metal activation, and sonochemistry, 1, 314 Metal alkoxides, synthesis, 12, 51 Metal-to-alkyne ligand charge-transfer transitions, rigid-rod transition metal—acetylide polymers,... 

TDDFT calculations results were consistent with the band shapes of the optical spectra of the parent complexes and are shown in Fig. 14. The calculated optical transitions are shown as bars under the experimental spectra and consist of MLLCT, ligand-to-ligand charge transfer transitions (LLCT), intraligand n - tt transitions (IL), and metal-complex delocalized-charge transfer transitions (MCDCT). Triplet state energies were also calculated based on a3 MLLCT state and correlated with experimental emission spectral results [53]. 

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