Photophysical Studies of XRe(CO)4L (X = Cl, I; L = CO, pip, PPh3) Complexes. Examples of Ligand Field Luminescence from Organometallic Complexes on Fluid Solution

Article abstract of DOI:10.1021/ja00220a028

A series of cis-XRe(CO)4L complexes have been prepared via photochemical and thermal reactions of the parent XRe(CO)5 species.Electronic absorption spectra have been recorded for these complexes in solution at 293 K and in EPA glasses at 80 K.The lowest lying absorption system is assigned definitively to ligand field (LF)¹A₁(e⁴b₂²) <*> ^1,3E(e³b₂²a₁¹) transitions; the band energies depend on L and are ordered CO > P donor > N donor, in accordance with the LF strength.Luminescence spectra, lifetimes, quantum yields, and excitation spectra from the cis-XRe(CO)4L (L = pip, PPh3) derivatives in both 293 K solution and EPA glasses at 80 K are consistent with emission from the lowest energy ³LF state.In contrast, the parent XRe(CO)5 molecules were not found to emit under identical experimental conditions.The photochemistry of these cis-XRe(CO)4L complexes has also been investigated.Irradiations at 313 or 366 nm of cis-XRe(CO)4L in solution at 293 K that contains an excess concentration of entering ligand give rise to ligand-substitution processes involving replacement of both CO and PPh3 ligands.Irradiations at 313 nm of cis-IRe(CO)4(PPh3) in solution at 293 K without added scavenging ligands leads to formation of carbonyl-bridged 2 dimer and I2 products.These photochemical processes are correlated with the model of lowest lying electronically excited states.