Electronic structures of organometallic complexes of f elements LXXV

The gas phase photoelectron (PE) spectra of LnCp3 (Cp = η-C5H5; Ln = Pr, Nd, Sm), measured with a wide range of photon energy, are reported. Resonances observed in the photon energy regions of 4d to 4f excitation enable identification of ion states resulting from 4f ionization. For all three compounds molecular ion states characteristic of both 4f(n) and 4f(n-1) configurations are observed (Pr, n = 2; Nd, n = 3; Sm, n = 6). The molecular ion ground states have a hole in the uppermost ligand orbital of a' symmetry and are reached by either ligand or f electron ionization. The results are discussed in the context of the previously reported spectra of the Ce, Yb and Lu analogues. For YbCp3 f orbital/ligand interaction is proposed in the molecular ground state and for CeCp3(+) in the molecular ion ground state. For PrCp3 and NdCp3 final state effects are proposed as the origin of the dual configuration structure in their PE spectra. When the contributing orbitals are close in energy the 4f/a' interaction can give rise to significant covalent bonding even in the absence of effective overlap.

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“…7 we indicate the energy range of identified states for Nd 3+ . 23,24 Bands II-VII all lie within this range. SmCp 3 .…”

Section: Papermentioning

confidence: 70%

Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides

Coreno¹,

Simone

Green

et al. 2014

Dalton Trans.

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“…14,16,17 In 4, the splitting of the f-orbitals is approximately twice as large as that in 1, which can be attributed to the greater radial extent of the 5f-orbitals. This result is consistent with previous crystal field studies, which show essentially the same splitting of the 4forbitals and a similar ordering (the relative order of the nearly degenerate f z 3 and (f xyz , f z(x 2 -y 2 ) )-orbitals varies).…”

Section: Please Do Not Adjust Marginsmentioning

confidence: 94%

“…10 Common approaches to studying bonding in actinides and lanthanides are comparing ions with either similar ionic radii, e.g., Ce(III) vs U(III), or similar electronic structures, e.g., Nd(III) vs U(III). 14,16,18,19 The role of this orbital in bonding may also be observed by photoelectron spectroscopy although the effect is more pronounced in the Cp 3 M + molecular cations. More recently, the relative energies of the ligand and metal-orbitals have received increased attention due to their roles in increasing covalency by "accidental degeneracy" (increased covalency due to the similar ligand and metal-orbital energies).…”

Section: Introductionmentioning

confidence: 91%

The roles of 4f- and 5f-orbitals in bonding: a magnetochemical, crystal field, density functional theory, and multi-reference wavefunction study

et al. 2016

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The electronic structures of 4f(3)/5f(3) Cp''3M and Cp''3M·alkylisocyanide complexes, where Cp'' is 1,3-bis-(trimethylsilyl)cyclopentadienyl, are explored with a focus on the splitting of the f-orbitals, which provides information about the strengths of the metal-ligand interactions. While the f-orbital splitting in many lanthanide complexes has been reported in detail, experimental determination of the f-orbital splitting in actinide complexes remains rare in systems other than halide and oxide compounds, since the experimental approach, crystal field analysis, is generally significantly more difficult for actinide complexes than for lanthanide complexes. In this study, a set of analogous neodymium(iii) and uranium(iii) tris-cyclopentadienyl complexes and their isocyanide adducts was characterized by electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility. The crystal field model was parameterized by combined fitting of EPR and susceptibility data, yielding an accurate description of f-orbital splitting. The isocyanide derivatives were also studied using density functional theory, resulting in f-orbital splitting that is consistent with crystal field fitting, and by multi-reference wavefunction calculations that support the electronic structure analysis derived from the crystal-field calculations. The results highlight that the 5f-orbitals, but not the 4f-orbitals, are significantly involved in bonding to the isocyanide ligands. The main interaction between isocyanide ligand and the metal center is a σ-bond, with additional 5f to π* donation for the uranium complexes. While interaction with the isocyanide π*-orbitals lowers the energies of the 5fxz(2) and 5fyz(2)-orbitals, spin-orbit coupling greatly reduces the population of 5fxz(2) and 5fyz(2) in the ground state.

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“…Bei NdCp* 3 haben die vibronischen Seitenbanden des hypersensitivenÜbergangs 4 I 9/2 → 4 G 5/2 bei ca. 90 K durchschnittliche Separationen von 950, 1160 und 1405 cm −1 , denen Raman-Linien bei 947, 1161 und 1401 cm −1 entsprechen dürften [48]. Gemäß unserer vorläufigen DFT-Rechnung sollten diese Signale Normalschwingungen der Natur C-H-Beugung, ν(C-C) und der Pulsationsschwingung entsprechen.…”

Section: Skelettschwingungenunclassified

“…Dabei stellt sich heraus, dass die fünf scharfen Banden zwischen 5181 und 5283 cm −1 offenbar durch Kopplung der Pulsationsschwingung bei 1125 cm −1 , und die in der Gegend von 5000 cm −1 möglicherweise durch die Kopplung mit der symmetrischen C-C-Schwingung der NCCH 3 [48] -jeweils ,,negative" Signale (Absorption aus der Hintergrundstrahlung, ,,inner filter effect" [54]) zu verzeichnen. Dieser Befund führte jedoch nicht zu sicheren ,,neuen" Energien, sondern bestätigte nur früher getroffene Zuordnungen.…”

Section: Absorptionsspektren Vonunclassified

Zur Elektronenstruktur metallorganischer Komplexe der ƒ -Elemente, 81. Berechnung der Normalschwingungen von La(η⁵-C₅H₅)₃(NCCH₃)₂ auf der Basis der Dichtefunktionaltheorie sowie vibronische Kopplungen und Auffindung weiterer rein elektronischer Absorptions- und Lumineszenzüberg¨ange bei [La(η⁵-C₅H₅)₃(NCCH₃)₂:Nd³⁺] / Electronic Structures of Organometallic Complexe

Amberger

Reddmann

2013

Zeitschrift Für Naturforschung B

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The planned model calculations of normal modes of pseudo-trigonal-bipyramidal LaCp 3 (NCCH 3 ) 2 (Cp = η 5 -C 5 H 5 − ) (1) adopting density functional theory (DFT), and using the molecular structure as suggested by X-ray investigations, did not converge. Alternatively, DFT calculations assuming molecular C 3h symmetry were performed. Unfortunately, these calculations did not reproduce the experimentally derived frequencies of the skeletal modes very well, including a wrong energetic sequence of the four previously unambiguously assigned (close lying) Raman-active ν(La-Cp) skeletal modes. The same presumably also holds for DFT calculations made for LaCp 3 ·NCCH 3 (2) and base-free LaCp 3 (3), assuming molecular C 3 and C 3h symmetry, respectively. In order to check whether the calculated incorrect sequence is produced by the five-membered Cp rings, a DFT calculation also has been performed for the hypothetical model complex [La(η 6 -C 6 H 6 ) 3 ] 3+ (4) of D 3 symmetry.A closer examination of the vibronic sidebands of the hypersensitive absorption transition 4 I 9/2 → 4 G 5/2 of [LaCp 3 (NCCH 3 ) 2 :Nd 3+ ] (5) showed that first of all, totally symmetric intraligand and not skeletal vibrations are coupling as it was the case for [LaCp 3 (NCCH 3 ) 2 :Ln 3+ ] (Ln = Pr, Sm). Applying this result to the vibronic sidebands of some purely electronic crystal field (CF) transitions, which are hampered by strong binary combination vibrations, the energies of these CF levels could be determined. The CF state 1Γ 8 of the ground multiplet 4 I 9/2 of [LaCp 3 (NCCH 3 ) 2 :Nd 3+ ], which previously could not be detected by absorption measurements, could be derived from the luminescence transition 4 F 3/2 → 4 I 9/2 . Considering these additional assignments, the goodness of the fit increased from 32.3 to 29.9 cm −1 for 61 assignments.

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Electronic structures of organometallic complexes of f elements LXXV

Cited by 13 publications

References 42 publications

Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides

Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides

The roles of 4f- and 5f-orbitals in bonding: a magnetochemical, crystal field, density functional theory, and multi-reference wavefunction study

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