Photochemistry inorganic complexes

In chemistry, however, the term isomers is generally used in connection with isolable compounds. Keeping this limitation in mind it has been found that, apart from chemistry and photochemistry of common inorganic complexes [1], isomerism is a very rare phenomenon in the chemistry of tetrapyrrole complexes. 

While electron-transfer processes are common in inorganic photochemistry, excited-state atom transfer is limited to a small class of inorganic complexes. For U022 , the diradical excited state ( U-OO is active in alcohol oxidation (2). The primary photoprocess is hydrogen atom abstraction by the oxygen-centered radical. Photoaddition to a metal center via atom transfer has been observed for binuclear metal complexes such as Re2(CO)io (3-5). The primary photoprocess is metal-metal bond homolysis. The photogenerated metal radical undergoes thermal atom-abstraction reactions. Until recently, atom transfer to a metal-localized excited state had not been observed. 

The photochemistry of thin films of inorganic complexes has been investigated as a means to produce thin films of inorganic materials. 

Early transition metal oxygen anion clusters, or polyoxometalates for short, are a large and rapidly growing class of inorganic complexes [1-15]. These compounds attracted us as it was apparent they simultaneously exhibited a unique set of properties we felt could be utilized to address new catalytic transformations, photoredox chemistry, and, ultimately construction of sophisticated single-molecule multifunctional devices capable of several temporally linked functions. These prognostications have already been borne out to a considerable extent. This article reviews the title subject, an enterprise still in its infancy. Presented sequentially in this chapter are the basic properties of polyoxometalates, general features of the photochemistry, the mechanisms elucidated in polyoxometalate photochemistry thus far, and an overview of the photochemistry of two representative complexes in tabular form (Table I). 

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. 

C. Kutal, Mechanistic inorganic photochemistry Parti—reactivity of the excited states ofCr(HI) complexes , /. Chem. Edu., 52, 1975, 502. 

Photooxidation of coordinated oxalate has been known since the earliest studies of transition metal photochemistry (42). In these reactions oxalate ligand is photooxidized to CO2, and up to two metal centers are reduced by one electron (e.g. ferrioxalate). We wondered whether the oxalate ligand could be a two-electron photoreductant, by simultaneous or rapid sequential electron transfer, with metals prone to 2e redox processes. Application of this concept to l6e square planar d complexes, Equation 15, was attractive because it should produce solvated I4e metal complexes that are inorganic analogues of... 

---