Intervalence charge-transfer IVCT

D Alessandro DM, Keene FR (2006) Current trends and future challenges in the experimental, theoretical and computational analysis of intervalence charge transfer (IVCT) transitions. Chem Soc Rev 35 424 140... 

Metal-metal interactions in [(C5H5)(dppe)Fe—CN—Ni(cyclam)— NC—Fe(dppe)(C5H5)] + and [(OC)5Cr—CN—Fe(cyclam)—NC—Cr(CO)5]" were probed by electrochemical and spectroscopic techniques,and intervalence charge-transfer (IVCT) within [(NC)5Fe"CNPt (NH3)5] and [(NC)5Fe"CNPt NCFe(CN)5] analyzed. ... 

Fe2 - Fe3 Charge Transfer. Partial reduction of Fe3 clays results in Fe2 and Fe3 cations occupying edge-sharing Fe06 coordination polyhedra. Such a condition allows for optically (and perhaps thermally) induced intervalence charge transfer (IVCT) transitions ... 

The electronic spectra of a variety of transition metal-bearing oxide and silicate minerals have been measured at high pressures and/or elevated temperatures. Trends for absorption bands originating from crystal field (CF), metal-metal intervalence charge transfer (IVCT) and oxygen —> metal charge transfer (OMCT) transitions are summarized in tables 9.2,9.3 and 9.4, respectively. 

Table 7 Comproportionation Constants (Kc) and Intervalence Charge Transfer (IVCT) Bands for Mixed Valence Complexes [Ru(NH3)5]2L5+...

From the A 1/2 = 320 mV, K om is 1.6 x 10, indicating this complex is a Robin and Day class II mixed-valence complex. Electronic absorption spectroelectrochemistry in the near infrared (NIR) shows an osminm-based intervalence charge transfer (IVCT) at 2440 cm. The extent of electronic delocalization, a, can be calcnlated nsing eqnation (16). 

Photoswitching of the electronic communication between two metal centers using the photochromic diarylethene bridging ligand with both thiophene moieties substituted with two cyclometallated phenylpyridines (Figure 23a) was first reported by Coudret and Launay. Although the comproportionation constants (Kc) for the dinuclear mixed-valence ruthenium complexes in both the open and closed forms were similar, the intervalence charge-transfer (IVCT) transitions were observed only in the closed... 

The uv/vis/nir spectra of mixed-valence species exhibit unique low-energy intervalence charge transfer (IVCT) transitions which are absent in the fully reduced and oxidised complexes. Qass (valence localised) mixed-valence systems have broad, weak, structureless IVCT bands which are sensitive to molecular environment (eg solvent ). Detailed study of these bands in trapped valence species allows os to calculate intramolecular electron transfer rates. Class III (valence delocalised) systems have more intense low-energy transitions which are often structured and are largely insensitive to solvent. We will consider the degree of metal-metal interactions within class III species by analysis of low-energy absorption transitions. 

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