Ligand field excited states examples

Luminescence is observed from coordination complexes of first row transition metals less often than from complexes of second or third row metals. This is a result of the presence of low-energy ligand field (LF) states into which the excitation is funneled that can rapidly deactivate through either non-radiative pathways to the ground state or photo-reaction pathways to products. Recent reports relating to the luminescence of titanium," chromium", and zinc complexes provide examples of new emissive first row coordination compounds. 

With the exception of a few highly studied states, such as, for example, the redox active lowest metal-to-ligand charge transfer excited state (MLCT) in the [Ru(bipyridine)3]2t cation, or the ligand field active 2E state of Cr(IlI), we know relatively little about these excited states. An enormous body of knowledge is waiting to be explored. 

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