Mixed-ligand complexes excited states

Mixed-ligand Crm complexes have a particularly rich substitutional photochemistry in that two (or more) reaction modes are normally observed. Data for the well-studied class of acidoamine complexes are presented in Table 2. The dominant photochemical reaction for [CrX(NH3)5]2+ complexes in aqueous solution is NH3 aquation, with X- aquation occurring to a lesser extent (equation 31). In contrast, the latter pathway is the favored thermal reaction of these compounds. Such behavior again illustrates that the reactivity of ligand field excited states can differ sharply from that of the ground state. 

A range of vanadyl(IV) complexes have been studied, e.g., VOL + (632) as well as mixed ligand complexes VOLL +, e.g., where L = oxalate (210, 213, 471, 632). VOLX2 (X = Cl, Br) is less tetragonal than V0(H20) from the ligand field point of view (157), i.e., there is less double-bond character in the VO bond when L is present. Quite marked splitting (3700 cm ) of the first excited state ( Eg -> Ai + is found forVCUL (157). 

It should be noted that for the mixed-ligand complexes the non-cyclometallated ligands are not involved in the lowest energy excited state, although they may indirectly affect to some degree the excited state properties via electron withdrawing or electron donating effects on the metal. 

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