UV/Vis Spectroscopic Properties of N -(2′-Hydroxy-4′- N , N -dimethyl-aminobenzylidene)-4-nitroaniline in Various Solvents and Solid Environments

 N-(2′-Hydroxy-4′-N,N-dimethylaminobenzylidene)-4-nitroaniline [HDBN] has been used as a model for investigating intra- and intermolecular D–A (donor–acceptor) interactions in various environments by means of UV/Vis spectroscopy. UV/Vis spectra of HDBN have been measured in various solvents, ethanolic solutions of different pH, adsorbed on silica, and in the solid state. A bathochromic shift of ν_max is observed with increasing the dipolarity/polarizability and HBD (hydrogen bond donor) capacity of the solvent, which is described by means of a multiple LSE (linear solvation energy) relationship in terms of the empirical Kamlet-Taft solvent polarity parameters. The adsorption of HDBN on Aerosil^? 300-silica particles in non-HBA (hydrogen bond acceptor) solvents is explained in the same sense. Mobile protons and sol–gel entrapping cause a hypsochromic shift due to protonation of the lone electron pair of the 4′-N,N-dimethylamino group. Hydroxide ions attack the 2′-hydroxy group which causes a bathochromic shift. A strong intramolecular hydrogen bond between the 2′-hydroxyl hydrogen and the imine nitrogen atom is present in the solid-state structure causing an unprecedented bathochromic shift.     

Ternäre Halogenide vom Typ A3MX6. II. Das System Ag3−xNaxYCl6: Synthese,Strukturen, Ionenleitfähigkeit

Ternary Halides of the A₃MX₆ Type. II. The System Ag_3?xNa_xYCl₆: Synthesis, Structures, Ionic Conductivity . The influence of the substitution of Ag⁺ by Na⁺ ions on the crystal structure and the ionic conductivity of Ag₃YCl₆ (stuffed LiSbF₆-type structure) has been investigated. The system Ag_3?xNa_xYCl₆ forms a complete solid solution. The stuffed LiSbF₆-type structure is stable for all compositions. For compounds with Na⁺ contents of x > 1.67, the cryolite-type structure is observed as the high-temperature form. The transition temperature decreases steadily with increasing Na⁺ content. The “end member” phase Na₃YCl₆ transforms at 243 K from the monoclinic cryolite-type structure to the stuffed LiSbF₆-type structure (trigonal, R3 ; a = 697.3(1), c = 1 868.4(14) pm, Z = 3; R = 0.094; R_w = 0.069). The crystal structures of Ag_1.3Na_1.7YCl₆ (trigonal, R3 ; a = 691.5(2), c = 1 853.7(6) pm, Z = 3; R = 0.099, R_w = 0.081) and AgNa₂YCl₆ (trigonal, R3 ; a = 691.7(1), c = 1 853.9(5) pm, Z = 3; R = 0.099, R_w = 0.064) have also been determined. Both chlorides crystallize like Ag₃YCl₆ and Na₃YCl₆-I in the stuffed LiSbF₆-type structure. The monovalent cations, Ag⁺ and Na⁺, are distributed over the five octahedral voids that are occupied by the Ag⁺ ions alone in Ag₃YCl₆. The ionic conductivity for compounds within the solid solution Ag_3?xNa_xYCl₆ decreases with increasing Na⁺ content. The values for Na₃YCl₆ (σ = 1 · 10^?6 Ω^?1 cm^?1 at T = 500 K) are by 2.5 to 3.5 orders of magnitude smaller than those for Ag₃YCl₆ (σ = 6 · 10^?4 Ω^?1 cm^?1 at T = 500 K).     

Eine Methode zur Bestimmung partieller spezifischer Volumen in kleinen Flüssigkeitsmengen

Zusammenfassung Eine Apparatur zur Bestimmung kleiner Dichtedifferenzen wird beschrieben, die einen mit einem kleinen Magneten versehenen Schwimmer enth?lt, der durch ein in me?barer Weise ver?nderliches magnetisches Feld in der Flüssigkeit zum Schweben gebracht wird. Zur Messung werden nur 10 ml L?sungsmittel und 10 ml L?sung ben?tigt. Die Empfindlichkeit betr?gt etwa 2 · 10⁻⁶ g/cm³ (2 Stellen der sechsten Dezimale der Dichte). Die zum Vergleich bestimmten partiellen spezifischen Volumen von Rinder-Serumalbumin und Chymotrypsinogen ergaben für das erstere im Konzentrationsbereich zwischen 0,04 und 0,65% einen Mittelwert von 0,733₅ (20,0° C) und für das letztere einen Wert von 0,720 (21,6° C).     

Structural Isomers of Bis(diphenylarsino)methane‐dichloroplatinum(II)

From a range of preparative methods, three geometric isomers of bis(diphenylarsino)methane‐dichloroplatinum(II) have been isolated, viz. cis‐PtCl₂(dpam), trans, trans‐Pt₂Cl₄(dpam)₂ and cis, trans‐Pt₂Cl₄(dpam)₂. Their structures were determined by single‐crystal X‐ray diffraction.     

Spin-orbit electronic states of octahedral Pt-group d 6 complexes as derived from reflectance spectra and ligand field calculations

The 90 K diffuse reflectance spectra of some octahedral Rh(III), Ir(III) and Pt(IV) complex compounds with chloride, thiocyanate and amine ligands are reported. The spectra show in the visible and near ultraviolet distinct bands due to spin-orbit components of singlet-triplet d-d transitions which are explained by ligand field calculations including spin-orbit coupling considering all possible d-electron configurations. Model parameter sets are obtained by fitting the measured band peaks to possible transitions between calculated energy levels. For some of the bands the vibrational structure could be resolved which is assigned to metal-ligand stretching vibrations of the electronically excited complex octahedra with vibrational fundamentals lower than those of the ground state.     

Bestimmung einer Phasenumwandlungstemperatur mit der Differentialthermoanalyse

Zusammenfassung Aus dem Maximalwert einer Differentialthermoanalysenkurve kann die Temperatur einer Phasenumwandlung abgeleitet werden. Für die Auswertung benötigt man Kurven, die bei verschiedener Aufheizgeschwindigkeit gemessen wurden. Das Verfahren wurde an K₂SO₄ und BaCO₃ getestet. Die Experimente ergaben 583,3 bzw. 809,6°C.Herrn Prof. Dr. H. Hausner danke ich für die Förderung dieser Arbeit und Frau H. Tyrlas für die umsichtige und sorgfältige Durchführung der Experimente.     

Synthesis and crystal structures of Cd[AlCl4]2 and Cd2[AlCl4]2

Colorless single crystals of Cd[AlCl₄]₂ grow from the melt of CdCl₂ and AlCl₃ upon slow cooling from 250°C. The crystal structure [monoclinic, P1a1, Z = 2, a = 1288.7(2), b = 660.2(1), c = 705.1(1) pm, β = 92.89(1)º] may be derived from hexagonally closest packed layers of Cl^?. Octahedral and tetrahedral holes are filled with Cd²⁺ and Al³⁺ in a 1:2 ratio between all layers stacked in the [104] direction. Cd[GaCl₄]₂ and Cd[AlBr₄]₂ are isotypic. Reduction of Cd[AlCl₄]₂ with excess cadmium shot and slow cooling from 350°C yields plate-like very moisture-sensitive, colorless single crystals of Cd₂[AlCl₄]₂. The crystal structure [triclinic, C1 , Z = 2, a = 655.47(3), b = 1135.26(1), c = 935.23(6) pm, α = 89.70(2)º, β = 103.61(1)º, γ = 90.455(1)º] is built from slabs stacked in the [100] direction consisting of ethane-like [Cd₂Cl₆] units with a Cd? Cd distance of 256.1 pm sharing common vertices with [AlCl₄] tetrahedra.     

Cs3[Tb10(C2)2]Cl21, ein neuer Formel- und Strukturtyp mit isolierten,dimeren Clustern

Cs₃[Tb₁₀(C₂)₂]Cl₂₁, A New Formula and Structure Type with Isolated Dimeric Clusters Cs₃[Tb₁₀(C₂)₂]Cl₂₁ is obtained via the metallothermic reduction of TbCl₃ with caesium in the presence of graphite as black single crystals. The crystal structure (monoclinic, C2/c, Z = 4; a = 2318.72(13); b = 1245.8(9); c = 1502.0(13) pm; β = 98.13(6)°; R = 0.089; R_w = 0.049) contains dimeric clusters that are built from two octahedra connected via one common edge and filled with C₂ units. These isolated [Tb₁₀(C₂)₂] clusters are surrounded by 26 chloride ligands which are then connected via i—a and a—a bridges in a way that voids for Cs⁺ of coordination number 10 are formed.