Ligand Identification in Titanium Complexes Using X-ray Valence-to-Core Emission Spectroscopy

Abstract

The identification of ligands in metalloorganic complexes is crucial for understanding many important biological and chemical systems. Nonresonant Kβ valence-to-core X-ray emission spectroscopy (XES) has been demonstrated as a ligand identification technique which is complementary to other spectroscopies, such as X-ray absorption. In this study we show the Kβ valence-to-core XES alongside the Ti K-edge X-ray absorption near edge structure spectra for a series of chemically relevant low-symmetry Ti organometallic complexes. The spectra are modeled using density functional theory calculations. XES spectra are analyzed in terms of the molecular orbitals probed, in order to understand the effects of bond length, bond nature, orbital hybridization, and molecular symmetry on the observed spectral features.

Cobalt Kβ valence-to-core X-ray emission spectroscopy: a study of low-spin octahedral cobalt(iii) complexes

“…In the current work, we develop a thorough understanding of cobalt Kβ V2C X-ray emission spectral features of a structurally diverse set of low-spin Co(III) complexes for the first time through combined experimental and computational studies. The experimental Co Kβ V2C features were found to be sensitive to valence orbital composition and cobalt-ligand environment, consistent with previous studies for iron, 11,13–25 manganese, 26–31 titanium, 32 chromium 33 and vanadium. 34 The ORCA single particle model was used to compute the V2C features of the cobalt complexes in this study.…”

XAS and XES Techniques Shed Light on the Dark Side of Ziegler–Natta Catalysts: Active‐Site Generation

“…In particular: i) the intense absorption around 25000 cm -1 in the DR UV-Vis spectrum ( Figure 2a) is assigned to fully allowed Cl(p)→Ti(d) ligand-tometal charge-transfer transitions, where the excited electron is associated with one of the nearest Cl anion and the transferred electron goes into a 3d orbital of the Ti 4+ ion; [14,[27][28][29][30] ii) the weak pre-edge peak at 4970.6 eV (shoulder at 4968.3 eV) in the XANES spectrum (Figure 2b), that precedes the absorption edge at 4979 eV, is due to 1s→pd transitions; [14,[31][32][33][34] iii) the two Kβ″ lines present in the vtc-XES spectrum (Figure 2c) at 4947 and 4953 eV are due to transitions mainly involving molecular orbitals having primarily O(2s) and Cl(3s) character, and thus identify the presence of oxygen and chlorine ligands in the first coordination sphere of the Ti sites. [35][36][37] The catalysts were obtained from the above mentioned precatalyst upon interaction with the AlR3 activator. In order to limit catalyst deactivation, excess of AlR3 was used, and this step was performed immediately before the spectroscopic measurements.…”

“…In principle, transitions involving Cl(3s) molecular orbitals could contribute in this energy region (as indicated by the label for the TiMg pre-catalyst), provided that they also have a Ti p contribution. [35,36,45] Also C ligands having sp 3 hybridization can contribute in the same energy region. As an example, the vtc-XES spectrum of TiC ( Figure S6) shows a prominent band at 4954 eV, which identifies the sp 3 hybridized carbon ligands.…”

Spin-state studies with XES and RIXS: From static to ultrafast

“…X-ray Emission Spectroscopy (XES) and Resonant Inelastic X-ray Scattering (RIXS) are very powerful in elucidating the electronic structure, providing information on the electron energies, local geometry, spin and valence state, etc. [9,17,18,19,20,21,22,23]. These tools can thus deliver complementary information to the usually employed ultrafast laser spectroscopies, when implemented in a pump-probe experiment with a laser pump and a time-delayed X-ray probe pulse.…”