Electronic luminescence spectra of charge transfer states of titanium(IV) metallocenes

Dual‐Active‐Site Nature of Magnesium Dichloride‐Supported Cyclopentadienyl Titanium Chloride Catalysts Switched by an Activator in Propylene Polymerization

“…[ 33 ] On the other hand, CpTiCl 3 in toluene showed a single absorption band at 406 nm. Though Hamar and co-workers [ 34 ] reported the presence of a weak shoulder at 475 nm (in dichloromethane), we could not observe it probably due to its small oscillation strength. Upon physical immobilization, the lower energy band of Cp 2 TiCl 2 (Cp → Ti) shifted hypsochromically, while the higher energy band was hardly shifted though its intensity was greatly reduced in immobilization.…”

Optical properties of ethylenebis(indenyl)zirconium(IV) binolate with binol=1,1′-binaphthyl-2,2′-diol. Binolate intraligand phosphorescence under ambient conditions

“…Since the emitting state is a triplet, zirconium and hafnium as metals of the second and third transition series facilitate the phosphorescence owing to their heavy-atom effect which leads to increased spinorbit coupling. Accordingly, the phosphorescence of dissolved Cp 2 Ti IV X 2 appears only at low temperatures [15] while Cp 2 Zr IV X 2 and Cp 2 Hf IV X 2 also phosphoresce at room temperature [8][9][10][11]. The emission originates from an LMCT state in agreement with the oxidizing nature of M(IV) and the reducing character of Cp À and X À .…”

“…Various complexes of the general formula Cp 2 M IV X 2 with M ¼ Ti [15], Zr and Hf [8][9][10][11][12][13] have been shown to be luminescent. Since the emitting state is a triplet, zirconium and hafnium as metals of the second and third transition series facilitate the phosphorescence owing to their heavy-atom effect which leads to increased spinorbit coupling.…”

Mechanism of the interaction of components in the metallocene catalytic systems containing titanium and zirconium tetracyclopentadienyls and methylaluminoxane

“…In molecules of the dimethylated zirconocene derivatives (Cp 2 ZrMe 2 ), the HOMO is localized on the methyl group bound to the zirconium atom, unlike the dichloride derivatives (Cp 2 ZrCl 2 ) in which the HOMO lies on the g 5 -cyclopentadienyl ligands [33,34]. According to the DFT calculations [31], the HOMO in a Cp 4 Zr molecule is localized on the r-bonded Cp ligand, as in the case of the dimethylated zirconocenes, which suggests that the ground electronic state of the catalytic precursor is similar to the electronic state of its methylated derivative.…”