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1.
Upon irradiation with ultraviolet wavelengths, Fe2(S2C3H6)(CO)6, a simple model of the [FeFe]‐hydrogenase active site, undergoes CO dissociation to form the unsaturated Fe2(S2C3H6)(CO)5 species and successively a solvent adduct at the vacant coordination site. In the present work, the CO‐photolysis of Fe2(S2C3H6)(CO)6 was investigated by density functional theory (DFT) and time‐dependent DFT (TDDFT). Trans Fe2(S2C3H6)(CO)5 form and the corresponding trans heptane or acetonitrile solvent adducts are the lowest energy ground state forms. CO dissociation barriers computed for the lowest triplet state are roughly halved with respect to those for the ground state suggesting that some low‐lying excited potential energy surface (PES) could be loosely bound with respect to Fe? C bond cleavage. The TDDFT excited state PESs and geometry optimizations for the excited states likely involved in the CO‐photolysis suggest that the Fe? S bond elongation and the partial isomerization toward the rotated form could take place simultaneously, favoring the trans CO photodissociation. © 2014 Wiley Periodicals, Inc.  相似文献   

2.
Configuration of the Vitamin-D3-Metabolite 25,26-Dihydroxycholecalciferol: Synthesis of (25S,26)- and (25R,26)-Dihydroxycholecalciferol For selective synthesis of the title compounds, (25S)- 1b and (25R)- 1b (Scheme 1), the protected cholesterol precursors (25S)- 6 and (25R)- 6 were prepared from stigmasterol-derived steroid-units 4a-d and C5-side chain building blocks 5a–d by Grignard- or Wittig-coupling (Scheme 2), the configuration at C(25) of the target compounds being already present in the C5-units. Conversion of the cholesterol intermediates to the corresponding vitamin-D3 derivatives was carried out via the 7,8-didehydrocholesterol compounds (25S)- 2b and (25R)- 2b (Scheme 1), using the established photochemical-thermal transformation of the 5,7-diene system to the seco-triene system of cholecalciferol. The configuration at C(25) of the cholesterol precursors as assigned on basis of the known configuration of the C5-units used, was found to be in agreement with the result of a single crystal X-ray analysis on compound 11 . The configuration at C(25) remained untouched on conversion of the cholesterol ring system to the seco-triene system of vitamin D3 as evident from comparison of the lanthanide-induced CD. Cotton effects observed for (25S)- 3b and (25S) 1b . 25,26-Dihydroxycholecalciferol observed as a natural vitamin-D3 metabolite has (25S)-configuration.  相似文献   

3.
The structures of a series of four‐coordinate nickel(II) complexes of the form [Ni(sacsac)L] PF6 (sacsac = pentane‐2,4‐di­thione anion; L = (Ph2P)2(CH2)n, n = 1,2,3) have beendetermined. These are [bis­(di­phenyl­phosphino)­methane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C25H22P2)(C5H7S2)]PF6, [1,2‐bis­(di­phenylphosphino)­ethane](pentane‐2,4‐di­thionato–S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C26H24P2)(C5H7S2)]PF6, and [1,3‐bis­(di­phenyl­phosphino)­propane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C27H26P2)(C5H7S2)]PF6. All have a distorted square‐planar arrangement about Ni with angles around Ni varying with the length of the hydro­carbon chain.  相似文献   

4.
The enantiomeric pure TADDOLate complexes of the heavier group 4 metals [(η5‐C5H5)2M{(S,S)‐TADDOLate}] (M = Zr, Hf) were prepared by treatment of (S,S)‐TADDOL with 2.5 equivalents of n‐butyl lithium followed by reaction with zirconocene and hafnocene dichloride, respectively. The new complexes have been characterized by standard analytical/spectroscopic techniques and the solid‐state structures of both compounds were established by single crystal X‐ray diffraction. The title compounds are the first fully characterized TADDOLate complexes of zirconium and hafnium.  相似文献   

5.
Complementary techniques had to be applied to investigate the binary system tetradecanedioic acid (C14H26O4)–hexadecanedioic acid (C16H30O4), because all the forms observed have the same space group (P21/c; Z = 2). We studied the polymorphism of the two single compounds and of their mixtures by X‐ray powder diffraction, differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). The two diacids were found to be isopolymorphic. At low temperature, they crystallize in the same ordered C‐form, and, on heating, adopt the ordered Ch‐form, 1° below their melting point. In contrast to similar compounds (unbranched alkanes, alkanols, and fatty acids), the solid–solid and solid–liquid phase‐transition temperatures decrease with increasing chain length. At low temperature, a new monoclinic form, Ci, appears as a result of the disorder of composition in the mixed samples. There are two [C + Ci]‐type solid–solid domains. On heating, the solid domains are related to solid–liquid domains by a peritectic invariant for compositions rich in C14H26O4, and by a eutectic invariant for compositions rich in C16H30O4. At higher temperature, there appears a second peritectic invariant for compositions rich in C14H26O4, together with a metatectic invariant for compositions rich in C16H30O4. All the solid forms observed in this binary system are isostructural. Nevertheless, the equilibrium between them is complex near the melting point, and their miscibility in the solid state is reduced.  相似文献   

6.
The dimeric condensation product of lactic acid, namely (S,S)‐2‐[(2‐hydroxypropanoyl)oxy]propanoic acid, C6H10O5, (I), crystallizes with two independent molecules in the asymmetric unit, which both have an essentially planar backbone. The trimeric condensation product, namely (S,S,S)‐3‐hydroxybut‐3‐en‐2‐yl 2‐[(2‐hydroxypropanoyl)oxy]propanoate, C9H14O7, (II), has one molecule in the asymmetric unit and consists of two essentially planar parts, with the central C—O bond in a gauche conformation. Both molecules of the dimer are involved in intermolecular hydrogen bonds, forming chains with a C(8) graph set. These chains are connected by D(2) hydrogen bonds to form a two‐dimensional layer. The trimer forms hydrogen‐bonded C(10) and C22(6) chains, which together result in a two‐dimensional motif. The Hooft method [Hooft, Straver & Spek (2008). J. Appl. Cryst. 41 , 96–103] was successfully applied to the determination of the absolute structure of (I).  相似文献   

7.
The structural, elastic, electronic, and optical properties of cubic spinel MgIn2S4 and CdIn2S4 compounds have been calculated using a full relativistic version of the full-potential linearized-augmented plane wave with the mixed basis FP/APW+lo method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel-Vosko GGA formalism is also applied to optimize the corresponding potential for band structure calculations. The ground state properties, including the lattice constants, the internal parameter, the bulk modulus, and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. Using the total energy-strain technique, we have determined the full set of first-order elastic constants Cij and their pressure dependence, which have not been calculated or measured yet. The shear modulus, Young’s modulus, and Poisson’s ratio are calculated for polycrystalline XIn2S4 aggregates. The Debye temperature is estimated from the average sound velocity. Electronic band structures show a direct band gap (Г-Г) for MgIn2S4 and an indirect band gap (K-Г) for CdIn2S4. The calculated band gaps with EVGGA show a significant improvement over the GGA. The optical constants, including the dielectric function ε(ω), the refractive index n(ω), the reflectivity R(ω), and the energy loss function L(ω) were calculated for radiation up to 30 eV.  相似文献   

8.
Poly(trifluoromethyl)fullerene S6‐C60(CF3)12 was reduced by sodium fluorenone ketyl in the presence of (PPN)Cl (PPN=bis(triphenylphosphine)iminium) to afford the salt (PPN)[C60(CF3)12] ( 1 ), which contains C60(CF3)12.? radical anions. In the crystal structure of 1 , C60(CF3)12.? layers alternate with the PPN+ cations. There are short F ??? F contacts between C60(CF3)12.? radical anions within the layers but no C ??? C contacts. DFT calculations revealed that the negative charge on C60(CF3)12.? is distributed mainly between sp2 carbon and fluorine atoms, whereas spin density is localized mainly on the fullerene‐cage sp2 carbon atoms. IR and UV/Vis/NIR spectra in the solid state and solution showed characteristic changes relative to those of neutral S6‐C60(CF3)12 due to the formation of radical anions. The solid‐state electronic spectrum of 1 exhibits a single broad band at 738 nm attributed to C60(CF3)12.?. Crystals of 1 show a narrow EPR signal with g=2.0025 (ΔH=0.45 mT) at 300 K. The temperature dependence of the integral intensity follows the Curie–Weiss law with a negative Weiss temperature of ?11.8 K (30–300 K) indicating antiferromagnetic interaction of spins. This dependence was approximated by the Heisenberg model for one‐dimensional chains of antiferromagnetically interacting spins with exchange interaction J/kB=?9.1 K. It was assumed that magnetic interaction between the C60(CF3)12.? spins in the layers is mediated by short F ??? F contacts.  相似文献   

9.
余文浩  赵可清  汪必琴  胡平 《化学学报》2007,65(12):1140-1148
盘状液晶分子能自组装成高度有序的六方柱状介晶相. 其各向异性的载流子高速迁移率使其成为较理想的有机光电子材料. 采用分子间氢键锚定柱状相, 获得介晶相温度范围宽、有序度高的苯并菲盘状液晶是本研究的目的. 本文通过分子设计, 合成了3个系列, 共18个有两种不同软链的苯并菲盘状液晶化合物C18H6(OR)5(OCH2COOEt), C18H6(OR)5(OCH2COOBu)和C18H6(OR)5(OCH2CONHBu), 其中R=CnH2n+1, n=4~9. 化合物的纯度和结构通过1H NMR和元素分析确证. 化合物热稳定性通过热重分析(TGA)测定, 并显示出较高的热稳定性. 通过偏光显微镜(POM)和差示扫描量热法(DSC)对这些化合物的热致液晶性进行了研究. 结果显示对于分子中含有酰胺基的苯并菲液晶化合物C18H6(OR)5(OCH2CONHBu), 与具有同样软链长度的分子中不含酰胺键的化合物系列C18H6(OR)5(OCH2COOBu)相比较, 前者由于柱内分子间氢键的形成, 具有更高的熔点和清亮点.  相似文献   

10.
A new salt, (PPN+)2(C702?) ? 2 C6H4Cl2 ( 1 ), which contains C702? dianions, has been obtained as single crystals (PPN+=bis(triphenylphosphine)iminium cation). The C702? dianions form polymeric zigzag (C702?)n chains, in which the fullerene units are bonded through single C? C bonds of length 1.581(5)–1.586(6) Å. The distance between the centers of neighboring C702? units is 10.441 Å. The optical and magnetic properties of (C702?)n have also been studied. Decreasing the symmetry of C70 in the polymer activate about 20 new IR bands in addition to the 10 IR‐active bands of the starting C70. The polymeric structure shows absorptions in the visible and NIR regions, with three main bands at 890, 1200, and 1550 nm, instead of one band of isolated C702? dianions at 1165–1184 nm. We concluded that the (C702?)n polymer was diamagnetic, with a negative molar magnetic susceptibility of ?3.82×10?4 emu mol?1 per C702? dianion. The polymer is EPR silent and a weak narrow EPR signal in salt 1 is due to impurities, which only constitute 0.84 % of spin S=1/2 of the total amount of fullerene C70.  相似文献   

11.
Stable BIII-subporphyrin-substituted dicyanomethyl radicals were synthesized by SNAr reaction of meso-bromo- or meso-chlorosubporphyrins with malononitrile followed by oxidation with PbO2. Different from previously reported dicyanomethyl radicals that underwent σ- or π-dimer formation both in the solid state and in solutions, subporphyrin-stabilized dicyanomethyl radicals exist as monomers in solutions even at low temperature. DFT calculations revealed efficient spin delocalization over the entire subporphyrin. In the solid state, these radicals form weak π-dimers with antiferromagnetic interactions depending on the crystal packing structures.  相似文献   

12.
A novel chiral phosphane (S)‐2‐(4‐isopropyl‐2‐oxazoline‐2‐yl)phenyl‐di‐N‐pyrrolylphosphane (S‐PyrPOx) based on asymmetric oxazoline ring has been prepared and characterised. Reaction of this ligand and its phenyl‐substituted analogue (S‐PhPOx) with H4Ru4(CO)12 and H3RhOs3(CO)12 gave substituted derivatives H4Ru4(CO)10(1,1‐PhPOx) ( 2 ), H4Ru4(CO)10(1,1‐PyrPOx) ( 3 ), and H3RhOs3(CO)10(1,1‐PyrPOx) ( 4 ), which were structurally characterised by X‐ray crystallography in solid state and by a variety of multinuclear NMR spectroscopic measurements in solution. In all studied clusters the coordinated ligands form five‐membered chelate rings through phosphorus and nitrogen atoms of oxazoline moiety to afford a novel chiral center associated with the substituted metal atom. The substitution reactions demonstrate extremely high stereoselectivity, which results in formation of only one diastereomer in all three cases to give S,S isomer in 2 and S,R isomer in 3 and 4 .  相似文献   

13.
Relaxation dynamics of the excited singlet states of 2,5-bis-(N-methyl-N-1,3-propdienylaniline)-cyclopentanone (MPAC), a ketocyanine dye, have been investigated using steady-state absorption and emission as well as femtosecond time-resolved absorption spectroscopic techniques. Following photoexcitation using 400 nm light, the molecule is excited to the S2 state, which is fluorescent in rigid matrices at 77 K. S2 state is nearly non-fluorescent in solution and has a very short lifetime (0.5 ± 0.2 ps). In polar aprotic solvents, the S1 state follows a complex multi-exponential relaxation dynamics consisting of torsional motion of the donor groups, solvent re-organization as well as photoisomerization processes. However, in alcoholic solvents, solvent re-organization via intermolecular hydrogen-bonding interaction is the only relaxation process observed in the S1 state. In trifluoroethanol, a strong hydrogen bonding solvent, conversion of the non-hydrogen-bonded form, which is formed following photoexcitation, to the hydrogen-bonded complex has been clearly evident in the relaxation process of the S1 state.  相似文献   

14.
Thiocyameluric acid C6N7S3H3, the tri-thio analogue of cyameluric acid, is a key compound for the synthesis of new s-heptazine (tri-s-triazine) derivatives. Here, two different routes for the synthesis of thiocyameluric acid and its reaction to tris(aryldithio)- and tris(alkyldithio)cyamelurates C6N7(SSR)3 are reported as well as transformation to alkali metal thiocyamelurates M3[C6N7S3], M=Na, K. These compounds were characterised by FTIR, Raman, solution 13C and 1H NMR spectroscopies, thermal gravimetric analysis (TGA) and elemental analysis. The three (de)protonation steps of thiocyameluric acid were investigated by acid–base titration followed via UV/Vis absorption spectroscopy. While it was not possible to determine the three pKa values, it could be postulated that the acid strength probably increases in the following order: cyanuric acid (C3N3O3H3) < thiocyanuric acid (C3N3S3H3) < cyameluric acid (C6N7O3H3) < thiocyameluric acid (C6N7S3H3). Single crystals of Na3[C6N7S3]⋅10 H2O and K3[C6N7S3]⋅6 H2O were obtained and the structures analyzed by single crystal X-ray diffraction. Additionally, quantum chemical calculations were performed to get insights into the electronic structure of thiocyameluric acid and to clarify the thiol–thione tautomerism. Based on a comparison of calculated and measured vibrational spectra it can be concluded that thiocyameluric acid and the di- and mono-protonated anions exist in the thione form.  相似文献   

15.
Two‐dimensional (2D) materials are commonly prepared by exfoliating bulk layered van der Waals crystals. The creation of synthetic 2D materials from bottom‐up methods is an important challenge as their structural flexibility will enable chemists to tune the materials properties. A 2D material was assembled using C60 as a polymerizable monomer. The C60 building blocks are first assembled into a layered solid using a molecular cluster as structure director. The resulting hierarchical crystal is used as a template to polymerize its C60 monolayers, which can be exfoliated down to 2D crystalline nanosheets. Derived from the parent template, the 2D structure is composed of a layer of inorganic cluster, sandwiched between two monolayers of polymerized C60. The nanosheets can be transferred onto solid substrates and depolymerized by heating. Electronic absorption spectroscopy reveals an optical gap of 0.25 eV, narrower than that of the bulk parent crystalline solid.  相似文献   

16.
The experimental temperature/composition phase diagram of the binary system decanedioic acid (C10H18O4)/dodecanedioic acid (C12H22O4) was established by combining X‐ray powder diffraction (XRD), differential‐scanning calorimetry (DSC), infrared spectroscopy (IR), scanning electron microscopy (SEM), and thermo‐optical microscopy (TOM). Both compounds crystallize in the same ordered form, C (P21/c), which is the phase that melts in both cases. The C form melts in C12H22O4 earlier than in C10H18O4, in contrast to other unbranched‐chain compounds (alkanes, alkanols, and alkanoic acids) in which the melting temperatures increase as the C‐atom number rises. Contrary to what might be expected, total solid‐state miscibility is not observed. The C10H18O4/C12H22O4 binary system shows a complex phase diagram. At low temperatures, a new monoclinic form, Ci (P21/c), stabilizes as a result of the disorder of composition in the mixed samples; two [C+Ci] domains appear. Upon heating, four solid–solid and seven solid–liquid domains appear related by eutectic and peritectic invariants. All the crystallographic forms observed are isostructural.  相似文献   

17.
The title compound, C25H19NO4S, (IV), was produced by a cyclo­condensation reaction similar to that which had previously produced an unexpected product, thus giving a novel route for such reactions. The structure of (IV) contains two S(6) motifs formed by strong intramolecular O—H?O hydrogen bonds. Weak C—H?O hydrogen bonds form primary C(11), R(7) and R(8) motifs which combine to form a complex three‐dimensional network.  相似文献   

18.
The polycyclic title compound {systematic name: (1S,16S,17S,31S)‐3,20‐diazatetracyclo[15.15.01,17.13,31.116,20]tetratriaconta‐6,8,23,25‐tetraene}, C32H52N2, has recently been isolated and characterized structurally, in solution by NMR spectroscopy and in the solid state by X‐ray crystallography. At 130 K the structure is monoclinic (P21, Z = 4) and comprises two molecules in the asymmetric unit with distinctly different conformations in the twelve‐C‐atom bridging chains. We report that, at 250 K, a phase change from monoclinic to orthorhombic (P22121, Z = 4) occurs. The higher‐temperature phase is structurally characterized herein at 293 K. The two different conformers resolved in the monoclinic low‐temperature form merge to give a single disordered molecule in the asymmetric unit of the high‐temperature phase.  相似文献   

19.
Multinary chalcogenido (semi)metalate salts exhibit finely tunable optical properties based on the combination of metal and chalcogenide ions in their polyanionic substructure. Here, we present the structural expansion of chalcogenido germanate(IV) or stannate(IV) architectures with SbIII, which clearly affects the vibrational and optical absorption properties of the solid compounds. For the synthesis of the title compounds, [K4(H2O)4][Ge4S10] or [K4(H2O)4][SnS4] were reacted with SbCl3 under ionothermal conditions in imidazolium-based ionic liquids. Salt metathesis at relatively low temperatures (120 °C or 150 °C) enabled the incorporation of (formally) Sb3+ ions into the anionic substructure of the precursors, and their modification to form (Cat)16[Ge2Sb2S7]6[GeS4] ( 1 ) and (Cat)6[Sn10O4S20][Sb3S4]2 ( 2 a and 2 b ), wherein Cat=(C4C1C1Im)+ ( 1 and 2 a ) or (C4C1C2Im)+ ( 2 b ). In 1 , germanium and antimony atoms are combined to form a rare noradamantane-type ternary molecular anion, six of which surround an {GeS4} unit in a highly symmetric secondary structure, and finally crystallize in a diamond-like superstructure. In 2 , supertetrahedral oxo-sulfido stannate clusters are generated, as known from the ionothermal treatment of the stannate precursor alone, yet, linked here into unprecedented one-dimensional strands with {Sb3S4} units as linkers. We discuss the single-crystal structures of these uncommon salts of ternary and quaternary chalcogenido (semi)metalate anions, as well as their Raman and UV-visible spectra.  相似文献   

20.
We perform first-principles simulations on a type of two-dimensional metal-organic nanosheet derived from the recently reported manganese bis-dithiolene Mn3C12S12 [Nanoscale 5, 10404 (2013)] and manganese bis-diamine Mn3C12N12H12 [ChemPhysChem 16, 614 (2015)] mono-layers. By coordinating chalcogen (S or O) atoms and -NH- group to Mn atoms with trans- or cis-structures and preserving space inversion symmetry, four configurations of this type of nanosheet are obtained: trans-manganese dithiolene-diamine Mn3(C6S3N3H3)2, cis- manganese dithiolene-diamine Mn3(C6S6)(C6N6H6), trans-manganese dihydroxyl-diamine Mn3(C6O3N3H3)2, and cis-manganese dihydroxyl-diamine Mn3(C6O6)(C6N6H6). The ge- ometric con guration, electronic structure and magnetic properties of these metal-organic nanosheets are systematically explored by density functional theory calculations. The cal- culated results show that Mn3(C6S3N3H3)2, Mn3(C6O3N3H3)2 and Mn3(C6O6)(C6N6H6) monolayers exhibit half-metallicity and display strong ferromagnetism with Curie transition temperatures near and even beyond room temperature, and Mn3(C6S6)(C6N6H6) monolayer is a semiconductor with small energy gap and spin frustration ground state. The mechanisms for the above properties, especially in uences of diflerent groups (atoms) substitution and coordination style on the magnetism of the nanosheet, are also discussed. The predicted two-dimensional metal-organic nanosheets have great promise for the future spintronics ap-plications.  相似文献   

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