The electronic structure of all-trans-polyenes C2nH2n+2, n = 3–7

The electronic structure of the C_2nH_2n+2 trans-polyenes, n = 3–7, is calculated by the Discrete Variational X_α method (DVM -X_α). The valence ionization potentials (IP ) calculated using the Clementi double zeta basis agree with the known experimental data within several tenths an electron volt. However, the DVM energies of the π → π* optical excitations are systematically underestimated by 0.8–1.0 eV. For polyenes with equal C—C bond lengths, the computed energies of the first optical transitions are smaller than those of polyenes with alternating C—C bond lengths. The charge distribution in polyenes is analyzed in the framework of a Mulliken scheme. The composition of the frontier molecular orbitals (MO ) is analyzed.     

Low-temperature Heat Capacities and Thermodynamic Properties of the Solid State Complexes(C2H10N2)MCl4(s)(M=Cu and Cd)

The tetrachlorocuprate(II) ethylenediammonium and tetrachlorocadmate(II) ethylenediammonium were synthesized. Chemical analysis, elemental analysis, and X‐ray crystallography were applied to characterize the compositions and crystal structures of the two complexes. The lattice potential energies and the radiuses of the anions of two complexes were calculated to be U_POT[(C₂H₁₀N₂)CuCl₄]=1810.19 kJ·mol^?1, U_POT[(C₂H₁₀N₂)CdCl₄]=1784.39 kJ·mol^?1, r[(CuCl₄)^2?]=0.308 nm, and r[(CdCl₄)^2?]=0.321 nm from the data of the crystal structure, respectively. Low‐temperature heat capacities of the two complexes were measured by a precision automatic adiabatic calorimeter with the small sample over the temperature range from 78 to 400 K, respectively. Two polynomial equations of heat capacities against the temperatures were fitted by least square method: C_p,_m[(C₂H₁₀N₂)CuCl₄, s] =213.553+118.578X?5.816X²+4.392X³+0.276X⁴ and C_p,_m[(C₂H₁₀N₂)CdCl₄, s] =190.927+98.501X?7.931X²+0.657X³+3.834X⁴, in which X= (T?239)/161. Based on the fitted polynomial equations, the smoothed heat capacities and thermodynamic functions of the two complexes relative to the standard reference temperature 298.15 K were calculated at intervals of 5 K.     

A novel glycoside lactone derivative with a 2-C-unsaturated diester substituent

The title 4,6-O-benzyl­idene-α-d -gluco­pyran­oside (systematic name: methyl 4-methoxy-2-oxo-8-phenyl-1,2,5a,6,9a,9b-hexa­hydro-4H,8H-7,9-dioxa­cyclo­penta­[c]­chromene-3-carboxyl­ate), C₁₈H₁₈O₈, has been synthesized from the reaction of methyl 4,6-O-benzyl­idene-α-d -2-ketogluco­pyran­oside with diethyl or di­methyl malonate. The compound adopts a chair–chair conformation. The newly formed five-membered ring is fused to the gluco­pyran­oside ring along the C₂—C₃ bond and is planar with an r.m.s. deviation of 0.0091 Å.     

Quantum-chemical investigation of the silicon and carbon coordination bond in their isostructural compounds

Ab initio calculations within the minimal basis set of STO -4LGTO have been carried out on molecules of type H₃MX (M = Si, C; X = H, NH₂, OH, F). The influence of the MH₃-group inversion on the electronic structure of these compounds has been investigated and illustrated by MO electron density maps. The ability of the central atom to form an additional bond has been estimated with the help of calculations on the complexes of these molecules with the hydrogen negative ion. The complexes of type [H₄SiX]^? have been found to be more stable than their unbonded components. The [H₄CX]^? complex formation has not proved to be advantageous.     

Mesogenic behaviour of two series of orthopalladated polar inline derivatives and their organic ligands (II)

Abstract

One series of 4-n-octyl-N-(4-X-benzylidene)anilines and two series of polar orthopalladated complexes derived from these of type Pd₂(μ-Y)₂ p-X-C₆H₃-CH = N-C₆H₄-C₈H_{17 2}; X: -H, -F, -Cl, -Br, -NO₂, -CN, -CH₃, -OCH₃, -CF₃, -COOCH₃, -OCOCH₃ and -OCOQH₅; Y: -OAc and -Cl; have been synthesized and their mesogenic properties studied. In the polar Schiff bases used as organic ligands, the polar end group determines both the presence of the mesophase and the type of mesophase exhibited. In the complexes, however, it is the central structure of the molecule that practically always determines mesogenic behaviour. No acetato-bridged complex is mesogenic. All the chloro-bridged complexes, however, show mesogenic behaviour. All these compounds show smectic A mesophases with the exception of the CN compound, which only exhibits a nematic mesophase.     

Die Struktur des Anhydro-isocalebassin-methyläthers; Säurekatalysierte Umlagerungen des Curare-Alkaloids C-Calebassin. 60. Mitteilung über Calebassen-Alkaloide [1]

Treatment of the Calebash alkaloid C-calebassine ( 1 ), C₄₀H₄₈N₄O₂⁺⁺·2X^?, with hot mineral acid yielded the anhydro-isocalebassine acid adduct 3H , with the formula C₄₀H₄₇N₄O⁺⁺⁺·3X^?.H₂O. This was converted into anhydro-isocalebassine methyl ether salts ( 4 ) C₄₁H₄₈N₄O⁺⁺·2X^?·H₂O with alkaline dimethyl sulphate. A total X-ray analysis of the orthorhombic diiodide led to formula 4 . The conversion of C-calebassine ( 1 ) into 4 involves a radical change in the central part of the molecule. The structure of the acid adduct 3H can be deduced from the structure of 4. Treatment of 3 H with warm methanol or treatment of C-calebassine ( 1 ) with acetic acid yielded a pale yellow compound 2 , C₄₀, H₄₄N₄⁺⁺·2X^?·H₂O. The central part of the molecule 2 contains a pyrrole ring, and most probably this is an intermediate in the conversion of 1 into 3 H by mineral acid. The changes of 3 H and 2 in acidic, neutral and basic media can be shown by electronic spectroscopy. Reaction of 3 H with 1 mole of oxygen at pH 4 converted it into a stable blood-red oxidation product C₄₀H₄₄N₄O₂⁺⁺·2X^? containing a merocyanine system. The structure 7 , proposed for this compound, is discussed.     

Synthesis and Structural Studies of Group 2B Transition Metal Complexes with the Bulky Nitrogen Ligand Bis[<Emphasis Type="Italic">N</Emphasis>-(2,6-diisopropylphenyl) imino]acenaphthene

Summary. Group 2B transition metal complexes of bis[N-(2,6-diisopropylphenyl)imino]acenaphthene (o,o-iPr₂C₆H₃-BIAN), namely, [Hg(o,o-iPr₂C₆H₃-BIAN)Cl₂] (1), [Zn(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (2), and [Cd(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (3) have been synthesized and characterized. In complexes 2 and 3, IR, NMR, and conductivity measurements confirm the coordination of two (o,o-iPr₂C₆H₃-BIAN) ligands to the metal center with two discrete perchlorate anions. X-Ray crystal structure of 1 indicates a distorted tetrahedral geometry with two nitrogen atoms from (o,o-iPr₂C₆H₃-BIAN) ligand and two chloride atoms coordinating to the Hg(II) center.     

Synthesis and Structural Studies of Group 2B Transition Metal Complexes with the Bulky Nitrogen Ligand Bis[ N-(2,6-diisopropylphenyl) imino]acenaphthene

Group 2B transition metal complexes of bis[N-(2,6-diisopropylphenyl)imino]acenaphthene (o,o-iPr₂C₆H₃-BIAN), namely, [Hg(o,o-iPr₂C₆H₃-BIAN)Cl₂] (1), [Zn(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (2), and [Cd(o,o-iPr₂C₆H₃-BIAN)₂](ClO₄)₂ (3) have been synthesized and characterized. In complexes 2 and 3, IR, NMR, and conductivity measurements confirm the coordination of two (o,o-iPr₂C₆H₃-BIAN) ligands to the metal center with two discrete perchlorate anions. X-Ray crystal structure of 1 indicates a distorted tetrahedral geometry with two nitrogen atoms from (o,o-iPr₂C₆H₃-BIAN) ligand and two chloride atoms coordinating to the Hg(II) center.     

SYNTHESIS AND CATIONIC RING-OPENING POLYMERIZATION OF 1, 4-ANHYDRO-2, 3-DI-O-(P-AZIDOBENZYL)-α-D-RIBOPYRANOSE

New highly stereoregular 2, 3 -di- O-(p-azidobenzyl )-(1 →5 ) - α-D -ribofuranan was synthesized byselective ring-opening polymerization of 1, 4-anhydro-2, 3 - di-O -(p-azidobenzyl )-α-D -ribopyranose(ADABR) using phosphorus pentafluoride or tin tetrachloride as catalyst at low temperature indichloromethane. The monomer was obtained by the reaction of p - bromomethyl -phenyleneazide with 1, 4 -anhydro-α-D-ribose in DMF. The structure of poly(ADANR) was identified by specific rotation and ~(13)C-NMR spectroscopy. Acid chloride-AgCl_4 complex catalyst such as CH_2=C(CH_3)C~+OClO_4~- used in thepolymerization resulted in polymers with mixed structures, i.e. (1→5)-α-D-ribofuranosidic and (1→4)-β-D-ribopyranosidic units. However, with C_6H_5C~+OClO_4~- as catalyst, pure (1→5)-α-D-ribofuranan was obtained.The effects of catalyst, polymerization temperature and time on polymer stereoregularity were examined, andthe mechanism of the ring-opening polymerization was discussed.     

Synthesis,structure and magnetic properties of a two-dimensional polymer based on sandwich-type tetra-cobalt(II)-substituted polyoxotungstate anions and 1-D potassium-chains

A 2-D coordination polymer, (C₇N₄H₁₆)₂{NH(CH₃)₃}[{K(H₂O)}₄Na(H₂O)₅{Co₄(H₂O)₂(B-α-PW₉O₃₄)₂}]·2H₂O (1), was hydrothermally synthesized and structurally characterized by IR spectroscopy, elemental analysis, X-ray powder diffraction, and X-ray single-crystal crystallography. Crystal structure analysis shows a triclinic space group Pī with a?=?12.4677(8)?Å, b?=?12.5054(8)?Å, c?=?18.5745(1)?Å, α?=?73.3220(1)°, β?=?87.1890(1)°, γ?=?62.2710(1)°, and V?=?2443.4(3)?ų. Sandwich-type tetra-cobalt(II)-substituted [Co₄(H₂O)₂(B-α-PW₉O₃₄)₂]^10? of 1 consists of two trivacant Keggin [B-α-PW₉O₃₄]^9? moieties and a rhomb-like Co₄O₁₆ unit. Each sandwich-type polyoxotungstate subunit connects 12 K(1) and K(2) centers from two adjacent 1-D K-chain units resulting in an interesting 2-D layer framework. Magnetic properties of 1 have been investigated.     

The chemistry of metal carbonyl anions : VII. Reduction of cyclopentadienylmetal carbonyls in hexamethylphosphoramide

The alkali metal reductions of a series of monomeric and dimeric cyclopentadienyl-substituted metal carbonyls in hexamethylphosphoramide provide principally C₅H₅V(CO)₃^2- from C₅H₅V(CO)₄, Mn(CO)₄^3- from C₅H₅Mn(CO)₃, Co(CO)₄^- from C₅H₅Co(CO)₂, and C₅H₅M(CO)_y^- from corresponding [C₅H₅M(CO)_y]₂, where M = Mo, Fe and Ni for y = 3, 2 and 1, respectively. The spectral and chemical properties of many of these reduced species are described.     

Singlet-triplet splitting of divalent five-membered fused rings C<Subscript>12</Subscript>H<Subscript>8</Subscript>M (M = C,Si, Ge,Sn, and Pb): Application in nanocomplex synthesis

Energy differences, ΔX _s−t (X = E, H, and G) (ΔX _s−t = X(singlet) − X(triplet)) between singlet (s) and triplet (t) states of C₁₂H₈M were calculated at B3LYP/6-311+G*. The DFT calculations indicated that the ΔG _s−t between singlet (s) and triplet (t) states of C₁₂H₈M were increased from M = C to M = Pb. The ΔG _s−t of C₁₂H₈M was compared with its analogue C₄H₄M through replacement of heavy atoms from M = C to M = Pb. Configurations of the electrons in orbitals (σ² or π²) for the singlet state of C₁₂H₈M were discussed.     

A method for phenomenological calculations in series of substituted benzenes

The methodology of calculations of the physicochemical properties of substituted benzenes C₆H_{6 − p} X _p , C₆H_{6 − p − q} X _p Y _q , ... (X and Y are univalent substituents) and C₆H₅A, where A = OH (phenol), NH₂ (aniline), etc. by the phenomenological methods of chemical structure theory is discussed.     

Koordinationsverbindungen des zweiwertigen Nickels und dreiwertigen Kobalts mit Äthylendiimino-bis-acetylaceton

The preparation of compounds with formula Ni(enac ₂) and [Co(enac ₂)L ₂]X is reported [H₂(enac ₂)=ethylenediimino-bis-acetylacetone, C₁₂H₂₀N₂O₂,L=NH₃,py, -pic, diethylamine;X=Cl^–, ClO _– ⁴ , B(C₆H₅) _– ³ ]. The complexes have been studied by means of magnetic susceptibility measurements, infrared, electronic and NMR spectra and conductivity measurements.     

Asymmetrische Hg(II)-Komplexe mit Organothiolato- bzw. Organoselenolato-und Triazenato-Liganden

The mixed mercury complexes (2XC₆H₄)₂N₃HgY (X=CH₃, F, Cl, Br, I;Y=SC₂H₅, SC₆H₅, SeC₆H₅) have been prepared. Both the Hg–S and Hg–Se bonds and, in contrast to other mixed triazenato-mercury compounds, the triazenato-mercury bonds have been shown to be kinetically labile on the NMR time scale by means of⁷⁷Se and¹⁹⁹Hg NMR spectroscopy. Evidence has been obtained for the presence of (2XC₆H₄)₂N₃HgY together with HgY ₂ and [(2XC₆H₄)₂N₃]₂Hg in solution.

     

Two ethyl 2-deoxy-α-d-hexo-3,7-pyranoso-3-octulosonate derivatives

In each of the two pyran­oid sugars, ethyl 2-deoxy-4,5,6,8-tetra-O-acetyl-α-d -gluco-3,7-pyran­oso-3-octulosonate, C₁₈H₂₆O₁₂, and ethyl 2-deoxy-4,5,6,8-tetra-O-benzyl-α-d -galacto-3,7-pyranoso-3-octulosonate, C₃₈H₄₂O₈, the anomeric configuration is α. The acetoxy­methyl substituent on the hexo­pyran­ose ring of the former compound and the ethoxy­carbonyl­methyl substituents in both sugars all have the gauche–trans conformation, while the benzyl­oxy­methyl substituent of the galacto­pyran­ose sugar has the trans–gauche conformation. In each structure, the anomeric hydroxy group forms an intramolecular hydrogen bond with the carbonyl O atom of the ethoxy­carbonyl­methyl substituent.     

SYNTHESIS AND CHARACTERIZATION OF TRIS(ALKYLISOCYANIDE) BIS(TRIARYL-PHOSPHINE)COBALT(II) COMPLEXES

Abstract

A series of complexes having the general formula, [Co(CNR)₃(PR₃)₂]X₂, X = ClO₄, BF₄ with CNR = CNCMe₃, CNCHMe₂, CNC₆H₁₁. CNCH₂Ph and PR₃ = PPh₃, P(C₆H₄Me-p)₃, P(C₆H₄OMe-p)₃ has been synthesized and characterized. Synthesis can be achieved by reaction of [Co(CNR)₄(AsPh₃)₂]X₂ complexes with controlled excess of PR₃ ligands, and by AgClO₄/AgBF₄ oxidation of the [Co(CNR)₃(PR₃)₂]X complexes. The latter procedure is preferable. Alternate syntheses of the [Co(CNR)₃(PR₃)₂]X complexes have also been employed. Five-coordinate Co(II) complexes have not been obtained using CNCMe₃ with P(C₆H₄Me-p)₃ ligands, CNCH₂Ph with P(C₆H₄OMe-p)₃ ligands, or CNC₄H_9-n with PPh₃ ligands. [Co(CNC-Me₃)₃{P(C₆H₄Cl-p)₃}₂]ClO₄ produced only [Co{CNCMe₃)₄H₂O](ClO₄)₂ upon forced oxidation with excess AgClO₄. [Co(CNR)₃(PR₃)₂]X₂ complexes appear to undergo varying degrees of distortion from regular (i.e., D _3h symmetry) axially-disubstituted trigonal bipyramidal coordination in the solid state, as evidenced by v(-N°C) IR patterns, but to assume regular trigonal bipyramidal coordination in solution. Effective magnetic moments indicate one-electron paramagnetism, and solution electronic spectra are compatible with trigonal bipyramidal coordination.     

Transition metal chemistry of oxime-containing ligands,IX

The vibrational (conventional and far-infrared) and diffuse-reflectance spectra in conjunction with magnetic susceptibility measurements over a temperature range down to liquid nitrogen temperature are reported and discussed for the complexes; [Mn(HPOX)₂ X ₂]; [Mn(HMPX)₂ X ₂]; [Fe(HPOX)(POX) X ₂] and [Fe(HMPX)(MPX) X ₂](whereHPOX=pyridine-2-aldoxime (C₆H₆N₂O);POX=C₆H₅N₂O;HMPX=6-Methylpyridine-2-aldoxime (C₇H₈N₂O);MPX=C₇H₇N₂O;X=Cl, Br, I, NO₃, NCS, or OA c andX ₂=SO₄). On the basis of these physical studies a six-coordinated structure is suggested for the manganese(II) and iron(III) complexes.Mössbauer spectra, measured at room-temperature and liquid nitrogen temperature also indicated a six-coordinate geometry for iron(III) complexes.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, IX. Spektroskopische und magnetische Untersuchungen von Mn(II)- und Fe(II)-Komplexen mit Pyridin-2-aldoxim und 6-Methylpyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (HPOX) und 6-Methylpyridin-2-aldoxim (HMPX) vom Typ [Mn(HPOX)₂ X ₂], [Mn(HMPX)₂ X ₂], [Fe(HPOX)(POX)X ₂] und [Fe(HMPX)(MPX)X ₂] (X=Cl, Br, I, NO₃, NCS, OA c;X ₂=SO₄) dargestellt. Die Diskussion erfolgt basierend auf Infrarot-spektroskopie (inklusive fernes IR), Messungen der magnetischen Suszeptibilität (Temp. bis zu fl. N₂) undMössbauer-Spektroskopie.

     

Impact of Transition Metal Substituents on Polysilane Properties: Iron versus Ruthenium

Summary. The previously unknown ruthenio disilanes Rp–Si₂Me₄–C₆H₄X (Rp = η⁵-C₅H₅Ru(CO)₂; X = H, Br, –CHO, CH=C(CN)₂) were synthesized from ClSi₂Me₄C₆H₄X (X = H, Br) and Rp⁻ using conventional chemical methods. Trends in the UV/Vis absorption spectra indicate strong electronic coupling within the Rp–Si–Si–C_aryl fragment and, therefore, closely resemble the ones observed for the corresponding iron complexes. The four compounds however, were shown to be less sensitive towards UV irradiation. The crystal structure of Rp–Si₂Me₄–C₆H₄CH=C(CN)₂ was determined by X-ray diffraction and exhibits an all-trans-array of the Ru–Si–Si–C_aryl moiety, what is a basic requirement for optimal through-bond interaction.     

CycloSiFA: The Next Generation of Silicon-Based Fluoride Acceptors for Positron Emission Tomography (PET)

The ring-opening Si-fluorination of a variety of azasilole derivatives cyclo-1-(iPr₂Si)−4-X−C₆H₃−2-CH₂NR ( 4 : R=2,6-iPr₂C₆H₃, X=H; 4 a : R=2,4,6-Me₃C₆H₂, X=H; 9 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiO; 10 : R=2,6-iPr₂C₆H₃, X=OH; 13 : R=2,6-iPr₂C₆H₃, X=HCCCH₂O; 22 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiCH₂O) with different ¹⁹F-fluoride sources was studied, optimized and the experience gained was used in a translational approach to create a straightforward ¹⁸F-labelling protocol for the azasilole derivatives [¹⁸F] 6 and [¹⁸F] 14 . The latter constitutes a potential clickable CycloSiFA prosthetic group which might be used in PET tracer development using Cu-catalysed triazole formation. Based on our findings, CycloSiFA has the potential to become a new entry into non-canonical labelling methodologies for radioactive PET tracer development.