Crystal Field Splitting Pattern Research Articles

Electronic structures of organometallic complexes of f elements LXXIX: Truncated crystal field splitting patterns of monomeric pseudo trigonal planar Yb(η5-C5H4R)3 (R = Me, Et, tBu, SiMe3) complexes and polymeric [(η5-C5H5)2Yb(μ-η5:η1-C5H5)] as well as selected mono adducts

The absorption spectra of pseudo (ψ) trigonal planar tris(methylcyclopentadienyl)ytterbium(III) (Yb(C5H4Me)3) have been recorded at room temperature and circa 77 K. The vibronic transitions were separated from the expected three purely electronic ones by correlating the transition energies with observed and assigned vibrational transition frequencies in the infrared spectrum. With this knowledge, the zero-phonon transitions in the absorption spectra of Yb(C5H4R)3 (R = Et, tBu, SiMe3) and [(η5-C5H5)2Yb(μ-η5:η1-C5H5)] (YbCp3), the latter being known since 1967, could be separated from phonon-assisted ones. The first low temperature luminescence measurements of an organometallic YbIII compound were performed by means of powdered YbCp3•THF and YbCp3•CNC6H11, respectively, and in both cases purely electronic and vibronic transitions were separated. The wavefunctions resulting from a fit of the truncated crystal field splitting pattern of YbCp3•THF allowed interpretation of the spectroscopic splitting factors g||/g⊥ and the temperature dependence of the paramagnetic susceptibility of this compound as well as the susceptibility anisotropy χ|| − χ⊥ of YbCp3•B (B = CNnBu, γ-picoline) and Yb(C5H4Me)3•B (B = CNtBu).

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 45[1]Ungewöhnliche spektrochemische Eigenschaften des Triphenylphosphanoxido‐Liganden im Falle von Mono‐ und Bisaddukten homoleptischer Samarium(III)silylamide

AbstractThe optical spectra of the mono tetrahydrofuran (1), mono triphenylphosphinoxide (2) and bis cyclohexylisocyanide (3) adducts of the tris(bis(trimethylsilyl)amido)samarium(III) (Sm(btmsa)3) moiety as well as those of the bis tetrahydrofuran (4) and partly those of the bis triphenylphosphinoxide (5) of the tris(bis(dimethylsilyl)amido)samarium(III) moiety have been recorded at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. The values of the crystal field parameters B$\rm^{2}_{0}$ of the OPPh3 adducts are much less negative than those of the remaining adducts or that of the base free compound.

Electronic structures of organometallic complexes of f elements LXXV : Parametric analysis of the crystal field splitting pattern of Nd(η 5-C 5Me 5) 3

By comparing the FIR, MIR, NIR and vis spectra (pellets) of NdCp ∗ 3 (Cp ∗ = η 5-C 5Me 5) ( 1) with those of Nd(C 5Me 4H) 3 ( 2) and LaCp ∗ 3 ( 3) the energies of a number of crystal field (CF) levels of 1 could be determined. The levels of the ground multiplet 4I 9/2 could be assigned on the basis of the polarized luminescence transition 4F 3/2 → 4I 9/2 of an oriented single crystal of 1, and the CF levels of the excited multiplets by assuming equal sequences of CF levels for 1 and those of 2 assigned previously on the basis of linear dichroism, luminescence anisotropy and electronic Raman measurements of oriented single crystals. In order to prove some uncertain assignments, the expected polarizations were checked against the observed ones in the σ and π absorption spectra of an oriented single crystal of 1 recorded by making use of the “inner filter effect”. The free parameters of a phenomenological Hamiltonian were fitted to the thus derived truncated CF splitting pattern of 1, leading to a reduced r.m.s. deviation of 14.0 cm −1 for 36 assignments. On the basis of the phenomenological CF parameters, the global CF strength experienced by the Nd 3+ central ion was estimated, and seems to be the fourth largest one ever encountered in Nd III chemistry. The obtained Slater parameter F 2 and the spin-orbit coupling parameter ζ 4 f allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Nd III compounds. The experimentally based nonrelativistic molecular orbital scheme (in the f range) of complex 1 was determined and compared with the results of a previous nonrelativistic Xα-SW calculation on the pseudo-trigonal-planar model compound Nd(η 5-C 5H 5) 3. The vibronic sidebands of the hypersensitive absorption transition 4I 9/2 → 4G 5/2 of 1 were correlated with inner-ligand vibrations. The temperature dependence of μ 2 eff of 1 was calculated and compared to the experimental data of the likewise pseudo-trigonal-planar complex Nd(C 5H 4 tBu) 3.

Crystal field splitting on D↔S transitions of atomic manganese isolated in solid krypton

Narrow excitation features present on the [Ar]3d64s1aD(J=9∕2−1∕2)6←[Ar]3d54s2aS1∕26 transitions of manganese atoms isolated in solid Kr are analyzed within the framework of weak crystal field splitting. Use of the Wp optical lineshape function allowed identification of multiple zero-phonon lines for individual spin-orbit J states of the a aD6←aS6 transition recorded with laser-induced excitation spectroscopy. Excellent agreement exists between the predicted crystal field splitting patterns for the J levels of the aD6 state isolated in the «red» tetravacancy site of solid Kr. The tetrahedral crystal field of the «red» trapping site splits J>3∕2 levels of the aDJ6 and aD7∕24 states by approximately 30cm−1. This report represents the first definitive evidence of crystal field splitting, induced by the weak van der Waals interactions between a neutral metal atom and the rare gas atoms surrounding it in a well-defined solid-state site.

Electronic structures of organometallic complexes of f elements LXXIII: Parametric analysis of the crystal field splitting pattern of tris(η 5-pentamethylcyclopentadienyl)cerium(III)

By comparing the far infrared (polyethylene pellets, room temperature) and mid-infrared spectra (KBr pellets, room temperature and ca. 90 K) of pseudo trigonal planar Ce(η 5-C 5Me 5) 3 ( 1) with the corresponding ones of La(η 5-C 5Me 5) 3 ( 2) and considering the low temperature paramagnetic susceptibility data of 1 the crystal field (CF) splitting pattern of 1 could be derived. The free parameters of a phenomenological Hamiltonian were fitted to this pattern achieving an r.m.s. deviation of 8.9 cm −1 for seven assignments. The fact that the difference of the experimental energies of the barycenters of CF levels of the multiplets 2F 7/2 and 2F 5/2 is larger than in the gaseous free Ce 3+ ion (experimental “anti”-relativistic nephelauxetic effect) could be explained by coupling effects of these multiplets via the CF, resulting in a lower spin–orbit coupling parameter than in the case of the free gaseous Ce 3+ ion. The experimental CF splitting pattern of 1 is compared to the results of a relativistic DV-Xα calculation on the pseudo trigonal planar model compound Ce(η 5-C 5H 5) 3. In addition, the prediction of the energies of f → d and charge transfer transitions of Ce(η 5-C 5H 5) 3 are compared to the absorption and luminescence spectra of complex 1.

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente 44 [1]. Erstmalige parametrische Analyse des Absorptionsspektrums einer Molekülverbindung des trivalenten Urans: Tris[hydrotris(1‐pyrazolyl)borato]uran(III)

AbstractThe absorption spectrum of tris[hydrotris(1‐pyrazolyl)borato]uranium(III) (UTp3) was run at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian achieving an r.m.s. deviation of 37.7 cm–1 for 29 assignments. The parameters used allow the insertion of the Tp ligand into empirical spectrochemical, nephelauxetic and relativistic nephelauxetic series of UIII compounds, and the set‐up of experimentally based nonrelativistic and relativistic molecular orbital schemes of UTp3 in the f range. Using the wavefunctions and eigenvalues of the fit, the experimentally determined temperature dependence (in the range 1.34–294.4 K) of μ2eff could be reproduced adopting an orbital reduction factor k = 0.99.

Parametric Analysis of the Crystal Field Splitting Pattern of Sm(η5-C5Me5)3Derived on the Basis of Absorption Spectra of Pellets or Solutions and Electronic Raman Spectra of Oriented Single Crystals

By comparing the absorption spectrum of pseudo trigonal planar Sm(eta(5)-C(5)Me(5))(3) (1) (KBr pellet, methylcyclohexane solution) with the previously assigned one of Sm(eta(5)-C(5)Me(4)H)(3) (2) a truncated experimental crystal field (CF) splitting pattern of the former compound could be derived in the NIR range. Because of its dark brown color, fluorescence is not observed from complex 1, and thus the CF splitting pattern in the low energy range could not be determined on the basis of luminescence measurements. However, comparing the FIR and MIR spectra (pellets) as well as the Raman spectra of oriented single crystals of 1 with those of La(eta(5)-C(5)Me(5))(3) (3) at least two additional CF levels could be detected. The free parameters of a phenomenological Hamiltonian were fitted to the thus extended CF splitting pattern of 1, leading to a reduced rms deviation of 15.0 cm(-1) for 21 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Sm(3+) central ion was estimated, and seems to be the third largest one ever encountered in Sm(III) chemistry. The obtained Slater parameter F(2) and the spin-orbit coupling parameter zeta(4f) allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Sm(III) compounds. With its low F(2) value, complex 1 is the most covalent Sm(III) compound (considering only f electrons) found to date. The experimentally based non-relativistic molecular orbital scheme (in the f range) of complex 1 was set up and compared with the results of a previous Xalpha-SW calculation on the pseudo trigonal planar model compound Sm(eta(5)-C(5)H(5))(3). In the frame of the search for f-f and electronic Raman transitions, the vibrational spectra (FIR/MIR of pellets, Raman spectra of oriented single crystals) of compound 1 were recorded too, and partly assigned on the basis of the observed coincidences and polarizations.

Optical properties of divalent samarium-doped fluorochlorozirconate glasses and glass ceramics

Glass ceramics comprising Sm 2+-doped barium chloride in both hexagonal and orthorhombic phases embedded in a fluorochlorozirconate glass matrix have been prepared. Divalent samarium doping was effected with the aid of NaBH 4 to partly reduce Sm 3+ in the starting materials to Sm 2+. The optical absorption spectrum in unannealed samples shows a strong, broad 4f → 5d band centred at around 340 nm and attributed to Sm 2+, but no photoluminescence is observed. Following annealing to induce crystallisation of Sm 2+-doped barium chloride crystals in the glass, photoluminescence is observed in the form of sharp line 4f → 4f transitions, and two broad 5d → 4f bands, the latter centred at around 680 and 900 nm. The 680 nm band disappears below about 250 K whilst the 900 nm band intensity increases with decreasing temperature. The 4f → 4f transitions for Sm 2+ ions in the orthorhombic phase of barium chloride show an abrupt change in the relative intensity of transitions originating from the 5D 1 and 5D 0 levels at around 90 K. The effect is attributed to the role of the 5d level in thermally assisted indirect transitions between the 5D 1 and 5D 0 levels. In contrast, transitions from only the 5D 0 level are observed for the hexagonal phase. The temperature dependence of the photoluminescence intensity, and the observation of a different crystal field splitting pattern for the 7F 1 level, can be used to distinguish between the two phases. The splitting pattern for the 7F 1 level for the hexagonal phase of barium chloride suggests that both possible crystallographic barium sites are occupied by Sm 2+ ions.

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 70, Optische und Raman‐spektroskopische Polarisationsmessungen an einem orientierten Tris(η5‐tetramethylcyclopentadienyl)neodym(III)‐(Nd(C5Me4H)3) sowie erstmalige Beobachtung “polarisierter” elektronischer Raman‐Effekte an einem orientierten metallorganischen Einkristall: Pr(C5Me4H)3

AbstractElectronic Structures of Organometallic Complexes of f Elements. 70, Optical and Raman Spectroscopical Polarization Measurements on an Oriented Tris(η5‐tetramethylcyclopentadienyl)neodymium(III) (Nd(C5Me4H)3) as well as First Observation of “Polarized” Electronic Raman Effects of an Oriented Organometallic Single Crystal: Pr(C5Me4H)3Looking for the ideal exciting line for recording the polarized vibrational Raman spectra of a small oriented single crystal of Nd(C5Me4H)3 (1), the laser lines at 785, 632.8 and 532 nm were used. Applying the laser line at 785 nm and comparing the spectra of 1 with those of La(C5Me4H)3 (2), the former are dominated by the σ and π luminescence spectra of the transition 4F3/2 → 4I9/2, which allowed to derive an improved crystal field (CF) splitting pattern of the ground manifold 4I9/2. Using the line at 632.8 nm a number of negative peaks were observed which are due to (absorbing) f‐f transitions excited by background radiation. The band positions and intensities as well as the polarizations of these signals correspond to the case of conventional σ and π absorption spectra of a big oriented single crystal. Comparing the polarized Raman spectra of 1, 2 and Pr(C5Me4H)3 (3) (using the laser line at 532 nm), it becomes evident that compound 3 exhibits additional peaks at 183 and 510 cm−1. The existence of CF levels of those energies as well as the strong frequency dependencies and the polarization properties of these bands indicate electronic Raman effects which are extremely rare in the case of organometallics.

Synthesis, Molecular, and Electronic Structure of (η8-C8H8)Ln(scorpionate) Half-Sandwich Complexes: An Experimental Key to a Better Understanding of f-Element-Cyclooctatetraenyl Bonding

Synthetic routes leading to two series of (eta(8)-cyclooctatetraenyl)lanthanide(III) scorpionate "mixed sandwich" complexes are reported. The early lanthanide derivatives (COT)Ln(Tp) (Ln = Ce (1), Pr (2), Nd (3), Sm (4)) and (COT)Ln(Tp(Me2)) (Ln = Ce (5), Pr (6), Nd (7), Sm (8)) (COT = eta(8)-cyclooctatetraenyl, Tp = hydrotris(pyrazolyl)borate, Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate) were obtained by reacting the dimeric halide precursors [(COT)Ln(mu-Cl)(THF)]2 with K[Tp] or K[Tp(Me2)], respectively For the late lanthanide elements a different synthetic route was developed. The complexes (COT)Ln(Tp) (Ln = Er (9), Lu (10)) were made by the reaction of (Tp)LnCl2(THF)1.5 with equivalent amounts of K2C8H8. All new compounds were isolated as intensely colored crystalline materials and fully characterized by elemental analyses and spectroscopic methods. The molecular structures of 4, 5, and 8 were elucidated by X-ray diffraction. The optical spectra of compounds 2 and 4-8 were run at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns of complexes 2, 4, 6, and 7 were derived and simulated by fitting the free parameters of a phenomenological Hamiltonian. The parameters used allow the estimation of the crystal field strengths experienced by the Ln3+ central ions and the insertion of complexes 2, 4, 6, and 7 into empiric nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally oriented non-relativistic and relativistic molecular orbital schemes of compound 6 were set up and compared with the results of previous model calculations on [Ln(COT)2]-, Pa(COT)2, and U(COT)2.

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 67 Erstmalige parametrische Analyse des Absorptionsspektrums einer Molekülverbindung des CeIIIμ: Tris(η5‐tetramethylcyclopentadienyl)cer

AbstractElectronic Structures of Organometallic Complexes of f Elements. 67 First Parametric Analysis of the Absorption Spectrum of a Molecular Compound of CeIIIμ: Tris(η5‐tetramethylcyclopentadienyl)cerium(III)The absorption spectra (in the IR/NIR/Vis/UV range) of Ce(C5Me4H)3 (1) and La(C5Me4H)3 (2) were recorded at room and low temperatures. From the spectra obtained, two alternative closely related crystal field (CF) splitting patterns of 1 could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. The fact that the difference of the experimental energies of the barycenters of CF levels of the multiplets 2F7/2 and 2F5/2 is larger than in the gaseous free Ce3+ ion (“anti”‐relativistic nephelauxetic effect) could be explained by coupling effects of these multiplets via the CF, resulting in lower spin‐orbit coupling parameters than in the case of the gaseous free Ce3+ ion. The experimentally derived CF splitting pattern of 1 is compared with the predictions of previous non‐relativistic SW‐Xα and relativistic DV‐Xα calculations.

Electronic structures of highly symmetrical compounds of f elements XLIII: Parametric analysis of the absorption spectrum of tris(bis(trimethylsilylamido))dysprosium(III) (Dy(btmsa) 3)

The absorption spectra of Dy(btmsa) 3 in KBr pellets have been recorded at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern was derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. The CF strength of the title compound is close to that of Er(btmsa) 3, and the free ion parameters show the expected strong nephelauxetic and relativistic nephelauxetic effects. The experimentally based non-relativistic molecular orbital scheme (in the f range) of Dy(btmsa) 3 is set up.

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 42 Ableitung und Simulation des Kristallfeld‐Aufspaltungsmusters von Tris(bis(trimethylsilyl)amido)ytterbium(III)

AbstractElectronic Structures of Highly Symmetrical Compounds of f Elements. 42 Derivation and Simulation of the Crystal Field Splitting Pattern of Tris(bis(trimethylsilyl)amido)ytterbium(III)Tris(bis(trimethylsilyl)amido)ytterbium(III), (Yb(btmsa)3 (1)) was grown as a single crystal of the size 6×2×2 mm. The unpolarized absorption and luminescence as well as the σ and π absorption spectra of this crystal were recorded at room and low temperatures. The observed polarization properties as well as identificational calculations allowed the separation of zero‐phonon‐ and phonon‐assisted transitions of comparable intensities. The thus derived crystal field splitting pattern could be simulated by fitting the free parameters of a phenomenological Hamiltonian. In order to assign the coupling vibrations, FIR/MIR‐ and unpolarized Raman spectra of 1 as well as polarized Raman spectra of Y(btmsa)3 (2) were recorded and compared with previously assigned ones of MeGa(btmsa)2 and H(btmsa).

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 65 Erstmalige Beobachtung des linearen Dichroismus bei einem homoleptischen metallorganischen π‐Komplex der f‐Elemente: Tris(η5‐tetramethylcyclopenta‐dienyl)neodym(III)

AbstractElectronic Structures of Organometallic Complexes of f Elements. 65 First Observation of Linear Dichroism of a Homoleptic Organometallic π Complex of f Elements: Tris(η5‐tetramethylcyclopentadienyl)neodymium(III)The absorption spectrum of a powder sample of pseudo (Ψ) trigonal planar Nd(η5‐C5Me4H)3 (1) has been measured at room temperature and ca. 40 K, respectively, and the linear dichroism spectra of σ‐ and π‐type of an oriented single crystal at ambient temperature and 77 K. Neglecting the signals of the C–H combination vibrations and overtones extracted from the absorption spectrum of La(η5‐C5Me4H)3 (2), the observed polarization properties of the remaining f‐f transitions allowed the derivation of a truncated crystal field splitting pattern. The free parameters of a phenomenological Hamiltonian were fitted to this pattern leading to a reduced r.m.s. deviation of 16.1 cm−1 for 38 assignments. The temperature dependence of the paramagnetic susceptibility of 1 was calculated, making use of the crystal field energies and wavefunctions of the fit. Introducing an orbital reduction factor of 0.98, calculated values of 1 agree well with the experimental ones of Ψ trigonal planar Nd(C5H4tBu)3.

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 41 Synthese, Kristall‐, Molekül‐ und Elektronenstruktur eines Bis(cyclohexylisonitril)‐Addukts des Grundkörpers Tris(bis(trimethylsilyl)amido)erbium(III) sowie Elektronenstrukturen ausgewählter Monoaddukte

AbstractElectronic Structures of Highly Symmetrical Compounds of f Elements. 41 Synthesis, Crystal, Molecular and Electronic Structure of a Bis(cyclohexylisonitrile) Adduct Derived from the Tris(bis(trimethylsilyl)amido)erbium(III) Moiety and Electronic Structures of Selected Mono AdductsThe reaction of tris(bis(trimethylsilyl)amido)erbium(III) (Er(btmsa)3) with two equivalents of cyclohexylisonitrile yields the corresponding bis adduct [Er(btmsa)3(CNC6H11)2] (1). Complex 1 crystallizes in the monoclinic space group C2/c with a = 2542.9(11) pm, b = 1208.4(4) pm, c = 1783.0(2) pm, β = 122.39(3)°, V = 4.638(5)·109 pm3, Z = 4 and R = 0.0380. The structure of compound 1 features the five coordinate Er3+ central ion in a nearly exact trigonal bipyramidal environment, with three btmsa ligands in the equatorial and the two cyclohexylisonitrile molecules in the axial positions. On the basis of the absorption spectra of bis adduct 1 and the mono(tetrahydrofuran) as well as the mono(triphenylphosphine oxide) adducts [Er(btmsa)3(THF)] (2) and [Er(btmsa)3(OPPh3)] (3), respectively, the underlying truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. Reduced r.m.s. deviations of 13.0 cm−1 (42 assignments), 16.0 cm−1 (63 assignments) and 17.5 cm−1 (55 assignments) could be achieved for compounds 1, 2 and 3, respectively. Making use of the phenomenological CF parameters of the fits, the experimentally based non‐relativistic molecular orbital schemes of complexes 1, 2 and 3 were set up, and compared with that of base‐free Er(btmsa)3.

Electronic Structures of Organometallic Complexes of f Elements. 62 Parametric Analysis of the Crystal Field Splitting Pattern of Pseudo Trigonal Planar Nd(η5‐C5Me4H)3

Abstract The absorption spectrum of pseudo (Ψ) trigonal planar Nd(η5‐C5Me4H)3 (1) has been measured at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern could be derived, and simulated by fitting the parameters of a phenomenological Hamiltonian. For 38 assignments, a reduced r.m.s. deviation of 30.7 cm−1 was achieved. On the basis of the CF parameters used, the global CF strength experienced by the Nd3+ central ion is estimated. The obtained Slater parameter F2 and the spin‐orbit coupling parameter ξ4f allow the insertion of compound 1 into truncated nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally based non‐relativistic molecular orbital scheme (in the f range) of complex 1 is set up and compared with the results of an SW‐Xα calculation on the fictive trigonal planar model complex NdCp3.

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 63 Parametrische Analyse des Kristallfeld‐Aufspaltungsmusters von pseudo trigonal‐planarem Er(η5‐C5H4tBu)3

AbstractElectronic Structures of Organometallic Compounds of f Elements. 63 Parametric Analysis of the Crystal Field Splitting Pattern of Pseudo Trigonal Planar Er(η5‐C5H4tBu)3The absorption spectrum of presumably pseudo trigonal planar Er(η5‐C5H4tBu)3 (1) has been measured at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern could be derived, and simulated by fitting the parameters of a phenomenological Hamiltonian. For 34 assignments, a reduced r.m.s. deviation of 24.8 cm−1 was achieved. On the basis of the CF parameters used, the global CF strength experienced by the Er3+ central ion is estimated, and the experimentally based non‐relativistic molecular orbital scheme (in the f range) is set up and compared with the result of an SW‐Xα calculation on the fictive trigonal planar model complex Dy(η5‐C5H5)3.

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 40. Parametrische Analyse des Kristallfeld‐Aufspaltungsmusters von Tris(hydrotris(1‐pyrazolyl)borato)neodym(III)

AbstractElectronic Structures of Highly Symmetrical Compounds of f Elements. 40. Parametric Analysis of the Crystal Field Splitting Pattern of Tris(hydrotris(1‐pyrazolyl)borato)neodymium(III)The absorption spectrum of tris(hydrotris(1‐pyrazolyl)borato)neodymium(III) (NdTp3) was run at room and low temperatures. From the spectra obtained, a truncated crystal field (CF) splitting pattern could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian achieving an r.m.s. deviation of 11.0 cm−1 for 48 assignments. The parameters used allow the estimation of the ligand field strength experienced by the Nd3+ central ion, the insertion of the Tp ligand into empirical nephelauxetic and relativistic nephelauxetic series, and the set‐up of experimentally based nonrelativistic molecular orbital schemes in the f range.

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 38 [1] Kristall‐, Molekül‐ und Elektronenstruktur von Tris(hydrotris(1‐pyrazolyl)borato)‐samarium(III)

AbstractElectronic Structures of Highly Symmetrical Compounds of f Elements. 38 [1] Crystal, Molecular and Electronic Structure of Tris(hydrotris(1‐pyrazolyl)borato)samarium(III)Tris(hydrotris(1‐pyrazolyl)borato)samarium(III) (SmTp3) crystallizes in the space group P63/m (No. 176) with two molecules in the unit cell. The Sm3+ central ion is coordinated by nine N atoms in the shape of a tricapped trigonal prism, leading to an effective crystal field (CF) of D3h symmetry. The underlying CF splitting pattern was extracted from the absorption and luminescence spectra run at room and low temperatures, and simulated by fitting the free parameters of a phenomenological Hamiltonian achieving an r.m.s. deviation of 9.4 cm−1 for 58 assignments. The parameters used allow the estimation of the global ligand field strength experienced by the Sm3+ central ion, the insertion of SmTp3 into empirical nephelauxetic and relativistic nephelauxetic series, and the set‐up of experimentally based nonrelativistic and relativistic molecular orbital schemes in the f range.

Crystal Field Strengths, Nephelauxetic Effects, and Experimentally Based Molecular Orbital Schemes (in the f Range) of Selected Cyclopentadienyl Complexes of Samarium(III)

AbstractThe absorption and luminescence spectra of pseudo (ψ) trigonal planar [Sm(η5‐C5H4tBu)3] (1), low symmetric [Sm(η5‐Cp)(η3‐Tp)(η2‐Tp)] (Cp = η5‐cyclopentadienyl; Tp = hydrotris(3,5‐dimethylpyrazolyl)borato) (2) as well as ψ trigonal pyramidal [Sm(η5‐C5H4tBu)3(THF)] (3), [Sm(η5‐Cp)3(THF)] (4) and [Sm(η5‐Cp)3(CNC6H11)] (5) have been measured at room and low temperatures. From the spectra obtained, truncated crystal field (CF) splitting patterns of these compounds could be derived, and simulated by fitting the parameters of a phenomenological Hamiltonian. On the basis of the CF parameters used, the global CF strengths experienced by the Sm3+ central ions of complexes 1−5, as well as the individual CF strength associated with one C5H4tBu− ligand are estimated. The obtained Slater parameters F2 and the spin‐orbit coupling parameters ζ4f allow the insertion of compounds 1−5 into truncated nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally based non‐relativistic and relativistic molecular orbital schemes (in the f range) of complexes 1 and, partly, 3 are set up and compared with the results of quantum chemical model calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)