Holger Schultze

The electronic structure of organometallic complexes of the ƒ elements—XI. Absorption spectrum and parameterization of the crystal field splitting pattern of a methyltetrahydrofuran adduct derived from tris(η5-cyclopentadienyl)-praseodymium(III)☆

Abstract The low temperature absorption spectrum of tris(η 5 -cyclopentadienyl)-praseodymium(III) dissolved in a 2-methyltetrahydrofuran glass has been measured. The observed transitions, along with the previously reported magnetic circular dichroism transitions, have been assigned and fitted to the parameters of a semiempirical Hamiltonian with an r.m.s. deviation of 27.2cm −1 for 40 levels. The experimental and calculated magnetic susceptibility of Cp 3 Pr·butyl acetate (which has an optical spectrum very similar to that of Cp 3 Pr·MeTHF) as a function of temperature are also given.

Zur elektronenstruktur metallorganischer komplexe der f-elemente: XXX. Kristall- und molekülstrukturen ungewöhnlich gut kristallisierender addukte des grundkörpers tris(η5-cyclopentadienyl)-lanthanoid(III)

Abstract The crystallizing properties of approximately 150 adducts derived from tris(η5-cyclopentadienyl) lanthanide(III) (Cp3Ln) and Cp′ 3Ln (Cp′  C5H5R; R  methyl, ethyl, t-butyl, benzyl, phenyl, trimethylsilyl) have been examined. Transparent single crystals which crystallize in the shape of distorted hexagonal plates of cross sections up to 200 mm2 could be grown for the n-butylacetate (BA) adduct of the early members of the Cp3Ln series and for the acetonitrile adducts for Cp3Gd and Cp3Tb. The crystal and molecular structures of Cp3Pr·BA(1) and Cp3Tb·NCCH3 (2) were determined. 1 crystallizes in the molecular space group P21 /n with four molecules in the unit cell, and 2 in the triclinic space group P1(Z = 2). The monoclinic angle β = 91.58° of 1 is close to the right angle of the rhombic system and the pseudo threefold axes of the individual molecules make angles of |14.97°| and |1 75.03°|, respectively, with the monoclinic b axis. For practical purposes 1 may be considered as being rhombic with the molecules aligned along the b axis. Thus, the individual molecules may be easily oriented with respect to a static magnetic field or the electric field vector of linearly polarized radiation. The α absorption spectrum of the spin allowed transitions of 1 is presented and some peculiarities are discussed.

The electronic structure of organometallic complexes of the f elements—XVI. Absorption spectrum and parameterization of the crystal field splitting pattern of the cyclohexylisocyanide adduct derived from tris (η5-cyclopentadienyl)-neodymium(III)☆

Abstract The low temperature absorption spectrum of Cp 3 Nd·CNC 6 H 11 in hydrocarbon glasses has been measured at 77 and ∼ 30 K. The bands were assigned based on calculations assuming the crystal field parameters of the Nd complex were the same as for the previously analyzed Cp 3 Pr·CNC 6 H 11 . Seventy-nine levels were fit to the parameters of a semiempirical Hamiltonian to give an r.m.s. deviation of 26.8 cm −1 .

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente: XXVII. Interpreation der optischen, magnetochemischen, ESR-und NMR-spektroskopischen Eigenschaften ausgewählter Neutralbasenaddukte, die sich vom Grundkörper Tris (n5-cyclopentadienyl)-neodym(III) ableiten

Abstract The absorption spectrum of (Cp- d 5 ) 3 Nd·THF- d 8 in hydrocarbon glasses and run as pellets was measured at room and low temperatures. The bands were assigned based on calculations assuming the crystal field parameters of the Nd complex were the same as for the previously analyzed Cp 3 Pr·MeTHF. The parameters of an empirical Hamiltonian wee fitted to the energies of 96 levels to give an r.m.s. deviation of 26 cm −1 . On the basis of the wave functions of the crystal field ground state obtained from these calculations, the observed EPR spectrum of Cp 3 Nd 0.06 La 0.94 ·THF could be explained. Making use of the calculated wave functions and eigenvalues the experimentally determined temperature dependence of μ 2 eff of powdered Cp 3 Nd·THF and of an oriented single crystal of Cp 3 Nd·Ncch 3 could be simulated. Assuming that the methyl protons of the γ-picoline ligand of Cp 3 Nd·γ-pic and (MeCp) 3 Nd· γ-pic, respectively, experience only an NMR shift of dipolar type, the paramagnetic anisotropy χ ∥ -χ ⊥ was estimated.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente—XX. Vibronische kopplungen bei Tris(η5-cyclopentadientadienyl)-lanthanoid(III)-Addukten

Abstract The vibronic transition 4 I 9/2 → 4 G 5/2 of the 2-methyltetrahydrofuran adduct of Cp 3 Nd and of (Cp-d 5 ) 3 Nd·THF- d 8 , respectively, is analyzed. The derived coupling vibrations which can also be detected in the i.r, and Raman spectrum are due to both skeletal and innerligand vibrations. With the knowledge of the energies of the coupling vibrations of Cp 3 Nd·MeTHF the vibronic and purely electronic transitions in the absorption spectra of Cp 3 Yb·CNC 6 H 11 and Cp 3 Yb·MeTHF could be separated. From the splitting of the manifold 2 F 5/2 the crystal field parameters B 0 2 and B 0 4 could be roughly estimated.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente. Teil 54. Elektronische Raman- und f–f–Übergänge in den Tieftemperatur-Schwingungsspektren von Cp3Ce(NCCH3)2(Electronic structures of organometallic complexes of f elements. Part 54. Electronic Raman and f–f transitions in the low temperature vibrational spectra of Cp3Ce(NCCH3)2)

Zusammenfassung Ein Vergleich der Tieftemperatur-Raman-Spektren von Cp 3 Ce(NCCH 3 ) 2 ( 1 ), Cp 3 La(NCCH 3 ) 2 ( 2 ), Cp 3 La(NCCH 3 ) 2 :Pr 3+ ( 3 ), Cp 3 La · NCCH 3 ( 4 ), Cp 3 Ce · NCCH 3 ( 5 ) und Cp 3 Tb · NCCH 3 ( 6 ) zeigt, das bei der ersteren Verbindung drei zusatzliche Banden bei 320, 2129 und 2154 cm −1 auftreten, die wir elektronischen Raman-Ubergangen zuschreiben. Die beiden letzteren Signale sind auch im Tieftemperatur-IR-Spektrum von Komplex 1 zu verzeichnen, jedoch nicht bei den Verbindungen 2 – 6 . Nach Durchfuhrung von Kristallfeld (KF)-Rechnungen konnten die Endzustande der beobachteten elektronischen Raman-Ubergange identifiziert werden. Sowohl auf der Grundlage der experimentellen als auch der berechneten Kristallfeld (KF)-Energien sowie der berechneten Wellenfunktionen wurde die beobachtete Temperaturabhangigkeit von μ 2 eff des Komplexes 1 in befriedigender Weise simuliert. Ein Vergleich des Tieftemperatur-Raman-Spektrums von Verbindung 1 mit dem Tieftemperatur-FIR-Spektrum des Komplexes 2 zeigt, das im Falle der Skelettschwingungen die Auswahlregeln fur trigonal-bipyramidale Koordination nicht streng befolgt werden. Falls man zusatzlich das Kriterium erlaubter vibronischer Seitenbanden der Ubergange Γ 1 →Γ 1, 4, 5, 6 von Verbindung 3 verwendet, konnen die beobachteten Schwingungsenergien teilweise gemas ihren Schwingungsrassen klassifiziert werden.

The electronic structure of organometallic complexes of the f elements XXIII. Interpretation of the magnetochemical and optical data of a tetrahydrofuran adduct derived from tris(η5-cyclopentadienyl)-ytterbium(III)☆

Abstract Magnetic susceptibility measurements for Cp3Yb · L (Cp  η5-C5H5; L  THF, γ-picoline) in the temperature range 5–300 K are reported, together with EPR spectra for the same compounds at low temperature. On the basis of these results and earlier optical data, preliminary values are derived for the spin-orbit coupling constant and crystal field parameters for Cp3Yb · L compounds.

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente

The absorption spectrum of (η5-Cp)3Er·CNC6H11 (1) has been measured at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern is derived, and simulated by fitting the parameters of an empirical Hamiltonian. For 46 assignments, a reduced r.m.s. deviation of 31 cm−1 is achieved. On the basis of the wavefunction of the CF ground state obtained from these calculations, the 2.5 K EPR spectrum of magnetically diluted 1 could be explained. Making use of the calculated wavefunctions and eigenvalues the experimentally determined temperature dependence of μ2eff of powdered 1 could be reproduced by adopting an orbital reduction factor k=0.985.

Zur elektronenstruktur metallorganischer komplexe der ƒ-elemente—XXIV. Interpretation der optischen und magnetochemischen Eigenschaften von Cp3CeIII THF auf der Grundlage der kristallfeldtheorie

Abstract On the basis of magnetic susceptibility, NMR spectroscopic and optical measurements the crystal field splitting pattern of (η 5 -C 5 H 5 ) 3 Ce III ·THF could be derived. The free parameters of an empirical Hamiltonian were fitted to the experimentally derived crystal field splitting pattern. Making use of the calculated crystal field eigenvalues, the magnetochemical data could be reproduced in a satisfactory manner.

Electronic structures of organometallic complexes of f elements. LIII. Comparison of the experimental spectroscopic splitting factors of a magnetically diluted tetrahydrofuran adduct derived from tris(η5-cyclopentadienyl)erbium with calculated values based on wavefunctions obtained from a parametric analysis of the absorption spectrum

Abstract The absorption spectrum of (η 5 -Cp) 3 Er·MeTHF ( 1 ) has been measured at room and low temperatures. Fitting the experimental energy levels to those obtained by the diagonalization of the energy matrices obtained from a parametric Hamiltonian resulted in 47 crystal field assignments with an r.m.s. deviation of 27.6 cm −1 . The averaged values of the spectroscopic splitting factors ∣ g ‖ ∣=8.07 and ∣ g ⊥ ∣=4.41 (extracted from the 2.6 K electron paramagnetic resonance spectrum of Cp 3 La 0.945 Er 0.055 ·THF ( 2 )) could be reproduced in a satisfactory manner with the wavefunction of the CF ground state obtained from these calculations. Also the experimentally determined temperature dependence of μ 2 eff of the powdered complex 1 could be simulated by using the calculated wavefunctions and eigenvalues.