PICOSECOND INVESTIGATIONS OF THE EXCITED-STATE TRANSITION AT 532 NM IN KINGS COMPLEX [(C5H5)FE(CO)]4 AND SYNTHESIZED ANALOGS

Variations of the organometallic cluster known as King's complex, [(C5 H5)Fe(CO)]4, have been synthesized to study the excited-state transiti on responsible for reverse saturable absorption observed at 532 nm in this molecule. Picosecond pump-probe measurements have been used to me asure the excited-state cross sections and lifetimes in King's complex and the analogs methyl-King's complex, [CH3(C5H4)Fe(CO)]4, and trieth ylaluminum King's complex, [(C5H5) Fe{COAl(C2H5)3}]4. Within experimen tal error, the excited-state parameters are unaffected by alterations to either the carbonyl or the cyclopentadienyl ligand of the King's co mplex. These results are consistent with an excited-state absorption r esulting from a second d to d transition within the singlet states of the metal core.