Phosphorescent ligand-to-metal charge-transfer excited states in the group IVB metallocene triad

Photophysical Properties and Coordination Interaction of d 0 Metallocenes with Unsaturated Hydrocarbons

“…However, as follows from the photoproperties of the representative triad of π complexes Cp 2 M ( IV ) Cl 2 , their radiative lifetimes decrease manyfold in the series Ti 4+ → Zr 4+ → Hf 4+ (table). It is worth noting that this is a consequence of a considerable increase in spinorbit coupling typical for transition metal ions with open electronic subshells, i.e., for soft acids.Previously [2,4,5], we assumed that these longlived states (their experimental lifetimes are among the largest known for metal-containing molecules) are triplet. In this case, we should observe their luminescence quenching in the presence of a triplet quencher of UHCs with large S -T splitting energies.…”

“…Previously [2,4,5], we assumed that these longlived states (their experimental lifetimes are among the largest known for metal-containing molecules) are triplet. In this case, we should observe their luminescence quenching in the presence of a triplet quencher of UHCs with large S -T splitting energies.…”

“…One of the most promising approaches to an understanding of the nature and properties of frontier orbitals of organometallic π complexes of Group IVB metalsmajor components of catalysts of a large number of organic syntheses-involves generation and study of electronically excited and ground redox states of molecules [1][2][3][4][5][6]. However, fundamental processes, such as energy and electron transfer, and properties of electronically excited states of organometallic compounds have been little studied partly due to the complexity of their synthesis and of manipulations with solutions of these compounds (especially with catalytic concentrations), which are extremely sensitive to moisture and oxygen traces and to minor impurities [7].…”

Photoisomerization and the nature of bond cleavage in π-complexes of early transition metals in photo and redox processes

“…In this work, the reversible isomerization of bridged metallocene was investigated for the first time; we also proposed an approach to comparative estimation of the factors that cause breaking of the structural integrity of d 0 -metal ion complexes upon single-photon excitation such as charge transfer from ligand to metal (LMCT), electrochemical transfer of an electron ( e -) to the lowest unoccupied MO (LUMO) (reduction), and generation of a vacancy ( h + ) on the highest occupied MO (HOMO) (oxidation). Earlier, it was demonstrated that the same MOs are involved in both optical and redox electron transfer in these metallocenes [2,[5][6][7].In the photolysis of Group IVB metallocenes with visible light in the absence of active additives, various photochemical reactions such as dissociation, isomerization, etc. can occur [2,5,8,9].…”

“…Earlier, it was demonstrated that the same MOs are involved in both optical and redox electron transfer in these metallocenes [2,[5][6][7].…”