Photochemistry of Chromium III Complexes

H. PHOTOCHEMISTRY OF CHROMIUM(HI) COMPLEXES A. Survey of Thermal and Photochemistry of Chromium(III) Complexes... 

Photochemistry.—The stereochemistry of photoinduced substitution reactions of chromium(iii) complexes has been analysed theoretically using orbital and state correlation diagrams. ... 

Ab initio calculations have also been carried out on the photochemistry of chromium(III) ammine complexes. Both ab initio calculations and the angular overlap model show that ligand rearrangements are confined to the original plane of excitation, and that the stereomobility required to obtain the predicted isomeric product can be modeled. ... 

It is several years since sufficient pattern had emerged in photoreactions of chromium(iii) complexes for Adamson to expound his empirical rules to codify this area of photochemistry. A general pattern for photoreactions of cobalt(m) complexes has been slower to emerge, principally owing to the difficulties attendant on characterizing primary photoproducts of redox processes, since cobalt(ii) is such a labile centre. However, a model based on known antibonding properties of excited states has recently been shown both to rationalize Adamson s empirical rules for chromium(ra) complexes and to... 

The special issue of Photochemistry and Photophysics of Coordination Compounds contains two reviews pertinent to Cr(III) systems and another general review coordination compound photochemistry is available. There is also a detailed review of the photophysics of chromium(III) complexes containing an extensive compilation of excited-state relaxation rates. 

It will become evident from this discussion of cobalt(III) and chromium(III) photochemistry that a fortunate combination of many factors makes these systems especially amenable to mechanistic investigation this is not the case for most other inorganic systems. For this reason, the progress made toward understanding the photochemical reactions of cobalt(III) and chromium(III) complexes may not be easily duplicated in other areas and it is useful to inquire whether conclusions reached here can be generalized. It is my belief that they can, and this and the next section are intended to place the subsequent discussion in the perspective of inorganic photochemistry. 

Table 2 Photochemistry of Mixed-ligand Chromium(III) Complexes upon Irradiation into the Lowest Quartet Ligand...

Wegner EE, Adamson AW. Photochemistry of complex ions. III. Absolute quantum yields for the photolysis of some aqueous chromium (III) complexes. Chemical actinometry in the long wavelength visible region. J Am Chem Soc 1966 88 394-404. 

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