脲盐的电子结构及其与光谱和能谱的关系

对脲盐的振动和电子光谱及Ｘ光电子能谱进行研究，并用电荷自洽场ＤＶ－Ｘα方法计算其电子结构，确定脲盐正离子ＣＯ（ＮＨ２）２Ｈ＾＋的结构特征，分析其结构变化与光谱和能谱现象的内在联系，并由此提出了形成配合物的反应机理。     

Calculated vibrational spectra of weak hydrogen bonds

Potential energy and dipole moment surfaces for the H-bond SH... S in the dimeric methanethiol have been calculated by the SCF-MO-LCGO method, and the vibrational spectrum — transition frequencies and IR absorption intensities at 20 °K — computed. This spectrum is compared with that of the monomeric species and with experimental results. The resulting dimerization energy is 1.4 kcal/mole.     

Vibrational spectrum of 3-methyl and 4-methylpyridine

The assignments of the vibrational spectra of the 3-methyl and 4-methylpyridine molecules have been carried out following the SQMFF methodology (scaled quantum mechanical force field). The theoretical frequencies have been obtained by calculating the RHF/3-21G force field, using the scale factors for pyridine and 2-methylpyridine and are correlated in a satisfactory manner with the frequencies recorded in the IR and Raman of these methyl derivatives.     

Ab initio study on the structures, energies, and vibrational frequencies of acetone complexes with metal monocations and dications

The structures, interaction energies, and vibrational frequencies of acetone and its complexes with proton and various metal monocations/dications such as H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Be²⁺, Mg²⁺, Ca²⁺, and Zn²⁺ have been investigated from the ab initio calculations. The linear or bent structure for the cation-acetone complexes has been found to be deeply influenced by the amount of charge transfer. The amount of red-shift of CO stretching frequencies of acetone is almost equivalent regardless of the kind of alkali metal monocations. This behavior can be attributed to the electrostatic nature of the interactions rather than orbital interactions. This phenomenon has been supported by the highest occupied molecular orbitals of the acetone complexes investigated, charge transfer based on natural bond orbital (NBO) atomic charges, and the inversely proportional behavior of the interaction energies to the interatomic distances r(M⁺O).     

The low frequency IR and Raman spectra of some complexes of dithiooxamide with cadmium halides

summary The low frequency IR and Raman spectra of Cd(DH ₄)X ₂ (X=Cl, Br;DH=dithiooxamide) have been discussed. On the basis of the cadmium isotope and H-D shift as well as chlorine-bromine substitution a band assignment in the region 500–33 cm^–1 has been made. A polymeric structure of Cd(DH ₄)X ₂ involving both dithiooxamide and halogen bridges with D_4h symmetry of the cadmium environment is assumed.

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Die niederfrequenten IR- und Raman-Spektren einiger Komplexe von Dithiooxamid mit Cadmiumhalogeniden

Zusammenfassung Die IR- und Raman-Spektren von Cd(DH ₄)X ₂ (X=Cl, Br;DH=Dithiooxamid) werden im Bereich niedriger Frequenzen diskutiert. Basierend auf Cadmiumisotopen- und H-D-Verschiebungen mit zusätzlicher Cl-Br-Substitution werden die Banden im Bereich von 500–33 cm^–1 zugeordnet. Es wird eine polymere Struktur von Cd(DH ₄)X ₂ unter Anteilnahme sowohl von Dithioxamid- als auch Halogenbrücken mit einer D_4h-Symmetrie im Bereich des Cadmiumzentralions angenommen.

     

Earth Alkaline Tetrathiosquarates: Syntheses and Crystal Structures of MgC4S4 · 6 H2O and CaC4S4 · 4 H2O

Concentrated aqueous solutions of magnesium chloride and calcium nitrate, respectively, allow on addition of the potassium salt of tetrathiosquarate, K₂C₄S₄ · H₂O, the isolation of the earth alkaline salts MgC₄S₄ · 6 H₂O ( 1 ) and CaC₄S₄ · 4 H₂O ( 2 ) as orange and red crystals. The crystal structure determinations ( 1 : monoclinic, C2/c, a = 17.2280(7), b = 5.9185(2), c = 13.1480(4) Å, β = 104.730(3)°, Z = 4; 2 : monoclinic, P2₁/m, a = 7.8515(3), b = 12.7705(5), c = 10.6010(4) Å, β = 93.228(2)°, Z = 4) show the presence of C₄S₄^2? ions with almost undistorted D_4h symmetry having average C–C and C–S bond lengths of 1.451Å and 1.659Å for 1 and 1.451Å and 1.655Å for 2 . The structure of 1 contains discrete, octahedral [Mg(H₂O)₆]²⁺ complexes. Several O–H····O and O–H····S bridges with H····O and H····S distances of less than 2.50Å connect cations and anions. The structure of 2 is built of concatenated, edge‐sharing Ca(H₂O)₆S₂ polyhedra. The Ca²⁺ ions have the coordination number eight, C₄S₄^2? act as a chelating ligands towards Ca²⁺ with Ca–S distances of 3.14Å. The infrared and Raman spectra show bands typical for the molecular building units of the two compounds.     

Crystal structure and vibrational spectra of pyridine-2,6-dithio-carbomethylamide

The crystal structure of Pyridine-2,6-dithio-carbomethylamide (PDTA) is described: C₉H₁₁N₃S₂, monoclinic, P2₁/c,Z=4,a=6.000 (1) Å,b=8.840 (1) Å,c=21.452 (1) Å, =105.47 (1)^o,d _x=1.47 gcm^–3. The structure was solved with direct methods and refined to a conventionalR-factor of 0.047. The molecule is nearly planar in the crystal. There are possibly weak intramolecular H-bonds between the two amide nitrogens and the pyridine nitrogen and intermolecular H-bonds between two amide nitrogens and one thioamide sulfur atom. The IR andRaman spectra ofPDTA and deuteratedPDTA are discussed.

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Kristallstruktur und Schwingungsspektren von Pyridin-2,6-dithiocarbomethylamid

Zusammenfassung Die Kristallstruktur von Pyridin-2,6-dithiocarbomethylamid (PDTA) wurde bestimmt: C₉H₁₁N₃S₂, monoklin, P2₁/c,Z=4,a=6,000 (1) Å,b=8,840 (1) Å,c=21,452 (1) Å, =105,47 (1)^o,d _x=1,47 gcm^–3. Das Phasenproblem wurde mittels direkter Methoden gelöst und die Struktur bis zu einemR-Faktor vonR=0,047 verfeinert. Das Molekül ist im Kristall nahezu planar. Das Vorliegen schwacher intramolekularer Wasserstoffbrücken zwischen den beiden Thioamid-Stickstoffatomen und dem Pyridinstickstoff sowie intermolekularer Wasserstoffbrücken zwischen Thioamid-Stickstoff- und Thioamid-Schwefelatomen wird postuliert. IR- undRaman-Spektren vonPDTA und deuteriertemPDTA werden diskutiert.

     

Structure and electronic properties for a newly synthesized red fluorescent material

The ground-state structure and electronic properties of a newly synthesized red fluorescent material, 2-[3-(2-{4-[(2-hydroxy-ethyl)-methyl-amino]-phenyl}-vinyl)-5, 5-dimethyl-cyclohex-2-enylidene]-malononitrile (A31), are investigated using a hybrid density-functional theory (DFT) approach, B3LYP, and the 6-31G* basis set. We have obtained four geometrical isomers. The theoretical infrared (IR) spectrum calculated by B3LYP/6-31G* level of theory is in very good agreement with our experimental measurement. The cation and anion are optimized to clarify the effects of the hole and electron injections and the energies needed by injections are estimated.     

Vibrational spectra and structure of some oxalic acid/substituted pyridine (methyl-, amino-, and dihalogeno-) complexes: Hydrogen bond features

The Raman and infrared spectra of some polycrystalline substituted pyridine/oxalic acid complexes have been investigated and assignments in terms of group frequencies are given. Various hydrogen bonds (NH?O, OH?O, OH?N) are distinguished and crystal structures are proposed. For the stronger bases (methyl- or aminopyridines with pk_a ≈ 6) proton transfer occurs. The 1/1 complex contains infinite chains of hydrogen oxalate ions linked by strong OH?O hydrogen bonds with vOH between 2000 and 800 cm⁻¹. R_OH?O distances are 2.47–2.62 Å). The substituted pyridinium cations are linked to the chain backbone by medium NH?O hydrogen bonds with NH?O lengths of 2.71–2.81 Å. The 3,5-dichloropyridine forms a 2/1 adduct without proton transfer, in accordance with its pk_a (0.6), and strong OH?N hydrogen bonds occur (vOH about 2000 cm⁻¹ and ). Finally, the 2,6-dihalogenopyridine derivatives do not form complex with oxalic acid, presumably because of steric hindrance.     

Darstellung,Schwingungsspektren und Normalkoordinatenanalyse von mer-[OsCl3I(NCS)]2− sowie Kristallstrukturanalyse von zwei Modifikationen des mer-(Ph4As)2[OsCl3I(NCS)2c]

Preparation, Vibrational Spectra, and Normal Cooordinate Analysis of mer-[OsCl₃I(NCS)₂^c]^2? and Crystal Structures of two Modifications of mer-(Ph₄As)₂[OsCl₃I(NCS)₂^c] By treatment of cis-/trans-[OsCl₄I₂]^2? or fac-[OsCl₃I₃]^2? with (SCN)₂ in dichloromethane mixtures of different linkage isomers are formed, from which mer-[OsCl₃I(NCS)]^2? has been isolated by ion exchange chromatography on diethylaminoethyl cellulose. With tetraphenylarsonium ions mer-(Ph₄As)₂[OsCl₃I(NCS)₂^c] crystallizes in two different modifications. From acetone solution the high-temperature form α precipitates above ?10°C, the low-temperature form β below, ?65°C. The X-Ray structure determinations on single crystals of α-mer-(Ph₄As)₂[OsCl₃I(NCS)₂^c] (triclinic, space group P 1 , a = 10.245(5), b = 11.690(5), c = 22.027(5) Å, α = 83.650(5)°, β = 85.734(5)°, γ = 72.566(5)°, Z = 2) and β-mer-(Ph₄As)₂[OsCl₃I(NCS)₂^c] (triclinic, space group P 1 , a = 10.959(5), b = 11.122(5), c = 21.745(5) Å, α = 97.677(5)°, β = 92.339(5)°, γ = 104.712(5)°, Z = 2) reveal the ordering of the complex anions, which significantly differ in their geometry. The via N coordinated thiocyanate groups exhibit Os? N? C angles of 172.7° and 173.3° (α) and of 164.4° and 175.4° (β). Using the molecular parameters of the X-Ray determinations the low temperature (10 K) IR and Raman spectra of the (n-Bu₄N) salt of the complex anion are assigned by a normal coordinate analysis based on a modified valence force field. The valence force constants are f_d(OsN) = 1.66 and 1.64 mdyn/Å. Taking into account the trans influence a good agreement between observed and calculated frequencies is achieved.