Theoretical Study on the Photoelectron Spectra of Ln(COT)2-: Lanthanide Dependence of the Metal-Ligand Interaction

Anionic Stacks of Alkali-Interlinked Yttrium and Dysprosium Bicyclooctatetraenes in Isolation

Electrospray ionization of THF solutions of preformed [K(18-c-6)][M(COT)₂] (M = Dy(III), Y(III); COT = C₈H₈^2-,18-c-6 = C₁₂H₂₄O₆) yields the isolated species [(M(COT)₂)_n+1 + nK]^- with n = 0-3. High-resolution ion mobility spectrometry combined with density functional theory calculations performed for the n = 0-2 aggregates indicate that anionic multidecker stacks interlinked by potassium cations are formed. The alternating metal ions are aligned linearly: COT^2--M³⁺-COT^2--K⁺-COT^2--M³⁺-COT^2-. The different M³⁺ ionic radii lead to slight but resolvable changes in mobility and thus collision cross sections indicative of different overall heights of the multidecker stacks. CID measurements show that the aggregates fragment by cleavage at the K⁺ interconnections.

New Photoelectron-Valence Electron Interactions Evident in the Photoelectron Spectrum of Gd2O. J Phys Chem A 2021;125:9892-9903. [PMID: 34730978 DOI: 10.1021/acs.jpca.1c07818]

Evidence of strong photoelectron-valence electron (PEVE) interactions has been observed in the anion photoelectron (PE) spectra of several lanthanide suboxide clusters, which are exceptionally complex from an electronic structure standpoint and are strongly correlated systems. The PE spectrum of Gd₂O^-, which should have relatively simple electronic structure because of its half-filled 4f subshell, exhibits numerous electronic transitions. The electron affinity determined from the spectrum is 0.26 eV. The intensities of transitions to excited states increase relative to the lower-energy states with lower photon energy, which is consistent with shakeup transitions driven by time-dependent electron-neutral interactions. A group of intense spectral features that lie between electron binding energies of 0.7 and 2.3 eV are assigned to transitions involving detachment of an electron from outer-valence σ_u and σ_g orbitals that have large Gd 6s contributions. The spectra show parallel transition manifolds in general, which is consistent with detachment from these orbitals. However, several distinct perpendicular transitions are observed adjacent to several of the vertical transitions. A possible explanation invoking interaction between the ejected electron and the high-spin neutral is proposed. Specifically, the angular momentum of electrons ejected from σ_u or σ_g orbitals, which is l = 1, can switch to l = 0, 2 with an associated change in the M_s of the remnant neutral, which is spin-orbit coupling between a free electron and the spin of a neutral.

Probing the structures, electronic and bonding properties of multidecker lanthanides: Neutral and anionic Lnn(COT)m (Ln = Ce, Nd, Eu, Ho and Yb; n, m = 1, 2) complexes

The ground state structures of neutral and anionic Ln_n(COT)_m (Ln = Ce, Nd, Eu, Ho and Yb; n, m = 1, 2) complexes have been identified by density functional theory. Ln(COT)_1,2^0/- and Ln₂(COT)₂^0/- complexes are found to possess sandwich ground state structures in which Ln atoms and COT molecules are alternately stacked except for Nd₂COT₂^0/-. Our calculated AEA and VDE values show good agreement with the available experimental values, which validates that our obtained ground state structures are credible. Based on the frontier molecular orbitals, we find that the bond formation between the 4f electrons of Ln atoms and the π clouds of COT molecules is weak. Then, the bond strength within these complexes is further analyzed based on the topological analysis of electron density at bond critical point. By analyzing Hirshfeld charge, we find Ln_n(COT)_m^0/- are charge-transfer complexes with weak bonding feature.

The “Wanderlust” of Me3Si groups in rare-earth triple-decker complexes: a combined experimental and computational study

The migration of Me₃Si groups (“Wanderlust”) in rare-earth triple-decker sandwich complexes of the type Ln₂(COT′′)₃ (COT′′ = bis(trimethylsilyl)cyclooctatetraenyl) has been elucidated by a combined experimental and computational study.

Scandium-Mediated Formation of a Bis(tetrahydropentalene)

The reactivity of Li[Sc(COT'')₂ ] (1; COT''=1,4-bis(trimethylsilyl)cyclooctatetraenyl) towards CoCl₂ is considerably different from that of related lanthanide triple-decker sandwich complexes. In addition to the expected triple-decker complex Sc₂ (COT'')₃ (2), the complex Sc₂ {μ-BTHP}(COT'')₂ (3) is formed, which comprises the novel BTHP^2- ligand (BTHP^2- =bis(3,5-bis(trimethylsilyl)-1,3a,6,6a-tetrahydropentalene-1-yl)diide or bis(2,7-bis(trimethylsilyl)bicyclo[3.3.0]octa-2,7-dien-4-yl)diide, C₁₆ H₁₀ (SiMe₃ )₄^2- ). The formation of 3 is likely facilitated by the fact that scandium prefers η⁸ ,η³  coordination rather than highly symmetric η⁸ ,η⁸  coordination, and the η³ -coordinated COT'' ligand in 1 is activated owing to a loss of aromaticity. Acid hydrolysis of 3 leads to air-stable H₂ BTHP (4).

First hyperpolarizability of cyclooctatetraene modulated by alkali and alkaline earth metals

In the present investigation, the first hyperpolarizability of alkali and alkaline earth metal derivatives of cyclooctatetraene (COT) has been calculated using BHHLYP and CAM-B3LYP functional for 6-311++G(d,p), 6-311++G(3df,3pd), and aug-pc 2 basis sets. Introduction of Na/K atoms at the axial position of COT and Li, Na, K/Be, Mg, Ca metal atoms and cyanide groups at the equatorial sites leads to lager enhancement of first hyperpolarizability. The ring charge density can account for the variation of first hyperpolarizability. The two state model has been invoked to explain the variation of first hyperpolarizability.