The felxibility pf the coordination sphere of mixed valence carbonyl complexes enables to tune spectral and protochemical properties. The variety of excited states in ilustrated on Ru, Re and W mixed ligand carbonyl complexed. The lowest excited states of [W(CO)4L] and [W(CO)5L’] (L=N,N'-di-methyl-1,4-diazabutadiene, ethylenediamine, 2,2’-bipyridine, phenantroline; L’= pyridine, 4-CN-pyridine, piperidine) ckomplexes were found to be either W -> pi*(L) or W -> pi*(CO) in charakter, depending on the type of the heteroligands