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

Electronic 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 Adducts The 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.     

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 36 [1] Parametrische Analyse der optischen Spektren eines orientierten Tris(hydrotris(1‐pyrazolyl)borato)praseodym(III)‐Einkristalls

Electronic Structures of Highly Symmetrical Compounds of f Elements. 36 [1] Parametric Analysis of the Optical Spectra of an Oriented Tris(hydrotris(1‐pyrazolyl)borato)praseodymium(III) Single Crystal The absorption and luminescence spectra of polycrystalline tris(hydrotris(1‐pyrazolyl)borato)‐praseodymium(III) (PrTp₃) were measured at room temperature as well as at low temperatures. At room temperature the “polarized” luminescence spectra of a small oriented PrTp₃ single crystal could also be recorded. On the basis of these spectroscopic findings the underlying crystal field splitting pattern could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian, achieving a reduced r.m.s. deviation of 17.3 cm^—1 for 37 assignments. On the basis of the parameters used, the global ligand field strength experienced by the Pr³⁺ central ion as well as the individual ligand field strength associated with one Tp ligand are determined, nephelauxetic and relativistic nephelauxetic effects are estimated, and the experimentally orientiented nonrelativistic and relativistic molecular orbital schemes in the f range are set up.     

Substrate‐Modulated Reductive Graphene Functionalization

Covalently functionalizing mechanical exfoliated mono‐ and bilayer graphenides with λ‐iodanes led to the discovery that the monolayers supported on a SiO₂ substrate are considerably more reactive than bilayers as demonstrated by statistical Raman spectroscopy/microscopy. Supported by DFT calculations we show that ditopic addend binding leads to much more stable products than the corresponding monotopic reactions as a result of the much lower lattice strain of the reactions products. The chemical nature of the substrate (graphene versus SiO₂) plays a crucial role.     

Mono‐ and Ditopic Bisfunctionalization of Graphene

For the first time, the bisfunctionalization of graphene by employing two successive reduction and covalent bond forming steps is reported. Bulk functionalization in dispersion and functionalization of individual sheets deposited on surfaces have both been carried out. Whereas in the former case attacks from both sides of the basal plane are possible and can lead to strain‐free architectures, in the latter case, retrofunctionalizations can become important when the corresponding anion of the addend is a sufficiently good leaving group.     

Zur Elektronenstruktur metallorganischer Komplexe der f-Elemente LXI. Welche Oxidationszahl hat Cer im tiefvioletten 1,1′,4,4′-Tetrakis(trimethylsilyl)cerocen?

Using the original and not a newly suggested synthesic route, Ce[C₈H₆(1,4-SiMe₃)₂]₂ (1) was resynthesized as an oil of deep purple color. The absorption, MCD and luminescence spectra of this compound were measured at room temperature as well as at low temperatures. Especially, the low-temperature spectra are more consistent with a Ce^III compound.     

Chemical Bonds and Spin State Splittings in Spin Crossover Complexes. A DFT and QTAIM Analysis

Summary. Density functional theory (DFT) calculations have been performed for the high-spin (HS) and low-spin (LS) isomers of a series of iron(II) spin crossover complexes with nitrogen ligands. The calculated charge densities have been analyzed in the framework of the quantum theory of atoms in molecules (QTAIM). For a number of iron(II) complexes with substituted tris(pyrazolyl) ligands the energy difference between HS and LS isomers, the spin state splitting, has been decomposed into atomic contributions in order to rationalize changes of the spin state splitting due to substituent effects.     

Noncovalent Functionalization of Black Phosphorus

Black phosphorus (BP) was functionalized with organic moieties on the basis of liquid exfoliation. The treatment of BP with electron‐withdrawing 7,7,8,8‐tetracyano‐p‐quinodimethane (TCNQ) led to electron transfer from BP to the organic dopant. On the other hand, the noncovalent interaction of BP with a perylene diimide was mainly due to van der Waals interactions but also led to considerable stabilization of the BP flakes against oxygen degradation.     

Linear Stability Analysis of a Viscous Liquid Sheet in a High-Speed Viscous Gas

Air-assisted atomizers in which a thin liquid sheet is deformed under the action of a high-speed air flow are extensively used in industrial applications, e.g., in aircraft turbojet injectors. Primary atomization in these devices is a consequence of the onset and growth of instabilities on the air/liquid interfaces. To better understand this process, a temporal linear instability analysis is applied to a thin planar liquid sheet flowing between two semi-infinite streams of a high-speed viscous gas. This study includes the full viscous effects both in the liquid and gas basic states and perturbations. The relevant dimensionless groups entering the non-dimensional Orr–Sommerfeld equations and boundary conditions are the liquid and gas stream Reynolds numbers, the gas to liquid momentum flux ratio, the gas/liquid velocity ratio, the Weber number and the equivalent gas boundary layer to liquid sheet thickness ratio. Growth rates and temporal frequencies as a function of the wave number, varying the different dimensionless parameters are presented, together with neutral stability curves. From the results of this parametric study it is concluded that when the physical properties of gas and liquid are fixed, the momentum flux ratio is especially relevant to determine the instability conditions. It is also observed that the gas boundary layer thickness strongly influences the wave propagation, and acts by damping sheet oscillation frequency and growth. This is especially important because viscosity in the basic gas velocity profile has always been ignored in instability analysis applied to the geometry under study. This revised version was published online in July 2006 with corrections to the Cover Date.     

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 78[1]Ergänzende Informationen von “polarisierten” Raman‐Spektren orientierter Einkristalle und Modellrechnungen auf der Grundlage der Dichtefunktionaltheorie bei der Zuordnung der Schwingungsspektren von Decamethylosmocen

The far and mid infrared (FIR/MIR) spectra of powdered Os(η⁵‐C₅Me₅)₂ (OsCp*₂) as well as the polarized Raman spectra of an oriented single crystal (where the two molecules of D_5h symmetry in the unit cell are uniformly oriented) have been recorded. The latter allow the assignment of the observed Raman lines to irreducible representations (irreps) which agree well with the predictions of a calculation applying density functional theory. This finding suggests additional correlation of the observed (unpolarized) bands in the FIR/MIR spectra with the calculated wavenumbers (and their irreps) of IR active normal modes. Neglecting νCH vibrations an r.m.s. deviation of 15.8 cm^–1 for 40 assignments (Raman and IR) could be achieved. Skeletal and intra‐ligand vibrations could be identified and a number of previous assignments of the latter had to be revised. Because of mixing with skeletal modes some of the low frequency intra‐ligand vibrations display a noticeable dependence on the mass of the central atom which prevents the direct transfer of the identified γCCH₃ and βCCH₃ normal modes from MCp*₂ (M = Fe, Ru, Os) to LnCp*₃ (Ln = La, Ce, Pr, Nd, Sm) complexes.