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1.
A Charge density analysis of CTB molecule in gas phase (Form I ) and the same present at the active site (Form II ) of p300 enzyme were performed for the wave functions obtained from the Density functional method (B3LYP) with the basis set 6‐311G**. This study has been carried out to understand the nature of conformational modification, charge redistribution and the change of electrostatic moments of the CTB molecule when present at the active site of p300. The difference of charge density distribution between both forms of CTB molecule explicitly indicates the effect of intermolecular interaction on CTB molecule in the active site. The dipole moment of CTB in the gas phase (9.6 D) has been significantly decreased (4.27 D) when it present at the active site of p300; this large variation is attributed to the charge redistribution in CTB, due to the intermolecular interaction between the CTB and the receptor p300 molecule. The electrostatic potential maps differentiate the difference of electrostatic potential between the two forms. A large electronegative region is found at the vicinity of oxygen and fluorine atoms. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012  相似文献   

2.
Linear and nonlinear optical properties of two new nickel(diimine)(dithiolate) complexes, nickel(4,4′‐dinitro2,2′‐bipyridyl)(tfd), Ni(NO2bipy)(tfd) , (tfd = 1,2‐trifluoromethylethene‐1,2‐dithiolate) and nickel(4,7‐diphenyl‐1,10‐phenathroline)(tfd), Ni(dpphen)(tfd) are reported. Ni(NO2bipy)(tfd) has a potent electronic acceptor substituted on the diimine ligand and exhibits an enhanced molecular first hyperpolarizability (β0 = ?31 × 10?30 esu), which is more than three times greater than that (β0 = ?10 × 10?30 esu) of Ni(dpphen)(tfd). Ni(NO2bipy)(tfd) also possesses the longest absorption wavelength, the largest solvatochromic shift, and one of the largest dipole moment changes (‐16 debye from ground to excited state) among nickel(diimine)(dithiolate) complexes. Crystal X‐ray structure of Ni(NO2bipy)(tfd) is used to compared the π‐bonding structure of central (N=C‐C=N)Ni(S‐C=C‐S) unit with that of previously known nickel(4,4′‐bis(butyloxycarbonyl)‐2,2′‐bipyridyl)(tfd), Ni(CO2Bubipy)(tfd).  相似文献   

3.
Self‐assembly reaction between hydrated rare‐earth (RE) nitrates RE(NO3)3 · 6H2O with K3Fe(CN)6 in H2O/DMF solution by employing the tridentate ligand 2, 2′:6′,2′′‐terpyridine (terpy) as a capping ligand has yielded three cyanide‐bridged compounds [RE(terpy)(DMF)(H2O)2][Fe(CN)6] · 6H2O [RE = Y ( 1 ), Tb ( 2 ), Dy ( 3 )]. FT‐IR spectra confirmed the presence of terpy ligands and cyanide groups in compounds 1 – 3 . Single‐crystal X‐ray structural analysis indicated that these compounds are isomorphous and adopt neutral [RE2Fe2] molecular squares, which are further linked through hydrogen bonding interactions to generate a three‐dimensional supramolecular network. Magnetic susceptibility measurements revealed that significant single ion magnetic anisotropy dominates the properties of these compounds.  相似文献   

4.
The title Schiff base compound {systematic name: 2‐[5‐[(E )‐(2‐hydroxybenzylidene)amino]‐4‐(2‐{5‐[(E )‐(2‐hydroxybenzylidene)amino]‐2‐(2‐hydroxyphenyl)‐1,3‐thiazol‐4‐yl}disulfanyl)‐1,3‐thiazol‐2‐yl]phenol}, C32H22N4O4S4, incorporating a disulfanediyl (dithio) linkage, was obtained from the condensation reaction between two equivalents of salicylaldehyde and one equivalent of dithiooxamide in dimethylformamide, and was characterized by elemental analysis, IR spectroscopic analysis and single‐crystal X‐ray diffraction. A one‐dimensional chain is formed along the b axis via double intermolecular C—H…S hydrogen bonds. The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies and some related molecular parameters were calculated at the B3LYP/6‐311G(d,p) level of theory. The molecular hyperpolarizability was also calculated.  相似文献   

5.
Density functional calculations using B3LYP/6‐311G method have been carried out for small to medium‐sized lithium clusters (LiN, N = 2–30). The optimized geometries of neutral and singly charged clusters, their binding energies, ionization potential, electron affinity, chemical potential, softness, hardness, highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gap, and static dipole polarizability have been investigated systematically. In addition, we study the distribution of partial charges in detail using natural population analysis (NPA) in small‐sized clusters (LiN, N = 2–10), both neutral and cationic, and demonstrate the correlation between symmetry and charge. Uniform distribution of charges in cationic clusters confirms them to be energetically more favorable than the neutral counterparts. Whenever possible, results have been compared with available data. An excellent agreement in every case supports new results as reliable predictions. A careful study of optimized geometries shows that Li9 is derivable from bulk Li structure, i.e., body centered cubic cell, and higher clusters have optimized shapes derived from this. Further, the turnover form two to three dimensional structure occurs at cluster size N = 6. The quantity α1/3 (α = polarizability) per atom is found to be broadly proportional to softness (per atom) as well as inverse ionization potential (per atom). The present work forms a sound basis for further study of large‐sized clusters as well as other atomic clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012  相似文献   

6.
Isomerization at the Complexation of 3-Acetyltetramic Acid: Structure and Magnetic Properties of the CuII- and NiII-Complex of 2,7-Bis (1′, 5′, 5′ -trimethylpyrrolidin-2′,4′ -dion-3′ -yl)-3,6-diazaocta-2,6-dien 2,7-Bis(1′, 5′, 5′ -trimethylpyrrolidin-2′, 4′ -dion-3′ -yl)-3,6-diazaoctadien formes CuII and NiII complexes with different constitutions (because of the Z/E isomerization). Results of X-ray analysis of N,N′ -ethylenbis(1′, 5′, 5′ -trimethylpyrrolidin-2′, 4′ -dion-3′ -acetiminato)nickel(II) 1 respectively -copper(II) 2 shows, that the complexing agent in 1 occurs in the E-form, whereas the ligand of the CuII complex forms the Z-form. Magnetic susceptibility and shift effects of the 13C-NMR signals point to a weak paramagnetism of the NiII complex. ESR-spectra are obtained from 2 only. Furthermore, the CuII complex reduces the relaxation times T1 and T2 of 1H and 17O nuclei spins from water. From the temperature dependence of the shortening of the relaxation times an activation energy is calculated which describes the reorientation of the copper complex in the “water matrix”.  相似文献   

7.
3′,4′,5′‐Trimethoxyflavonol (TMFol) is a synthetic flavonol with preclinical cancer chemopreventive properties. The hypothesis was tested that, in mice, p.o. administration of TMFol results in measureable levels of the parent in target tissues. A single oral dose (240 mg/kg) was administered to mice (n = 4 per time point) with time points ranging from 5 to 1440 min. TMFol and its metabolites were identified and quantitated in all tissues by high‐performance liquid chromatography (HPLC). Plasma levels of TMFol were at the limit of quantification or below, although metabolites were identified. Peak levels of TMFol in the gastrointestinal tract and the prostate averaged 1671 ± 265 µg/g (5.3 µmol/g) and 6.0 ± 1.6 µg/g (18.4 nmol/g), and occurred 20 and 360 min post‐dose, respectively. The area under the tissue concentration–time curve (AUC) for TMFol was greater than those of the metabolites, indicating that TMFol is relatively metabolically stable. Micromolar TMFol levels are easily achieved in the prostate and gastrointestinal tract, suggesting that TMFol might exert chemopreventive efficacy at these tissue sites. Further investigations are warranted to elucidate the potential chemopreventive potency of TMFol. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

8.
To evaluate the contribution of indirect action mediated by OH radicals in biological effects of high LET radiations, we examined the production of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in 2′-deoxyguanosine aqueous solution using various ion species with an LET range from 20 to 300 keV/μm. The 8-OHdG yield decreased with increasing LET. In the hypoxic irradiation condition, the yield showed constant or rather increasing tendency above about 100 keV/μm, which is consistent with an oxygen-in-the-track hypothesis to explain the diminishment of oxygen effect.  相似文献   

9.
The involvement of the 5′-hydroxyl group on β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione ( 1b ), to form an intramolecular covalent adduct at C6, is postulated to explain the formation of almost equal amounts of 5-N-alkyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazin-4-one-6-thione and 5-N-alkyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazine-4,6-dione during alkylation of 1b . An X-ray crystallographic study was conducted on 5-N-methyl-β-D-arabinofurano[1′,2′:4,5]oxazolo-s-triazine-4,6-dione ( 2a ) and its solid state structure was established. This was compared to the energy minimized structure of the same compound that was generated by the molecular modeling program, MACROMODEL. Force field calculations (Allinger's MM2) on this structure and other intermediates lend support to the concept of formation of the intramolecular covalent adduct.  相似文献   

10.
Luminescent CuI complexes have emerged as promising substitutes for phosphorescent emitters based on Ir, Pt and Os due to their abundance and low cost. The title heteroleptic cuprous complex, [9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)‐9H‐xanthene‐κ2P ,P ](2‐methylquinolin‐8‐ol‐κ2N ,O )copper(I) hexafluorophosphate, [Cu(C10H9NO)(C39H32OP2)]PF6, conventionally abbreviated as [Cu(Xantphos)(8‐HOXQ)]PF6, where Xantphos is the chelating diphosphine ligand 9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)‐9H‐xanthene and 8‐HOXQ is the N ,O‐chelating ligand 2‐methylquinolin‐8‐ol that remains protonated at the hydroxy O atom, is described. In this complex, the asymmetric unit consists of a hexafluorophosphate anion and a whole mononuclear cation, where the CuI atom is coordinated by two P atoms from the Xantphos ligand and by the N and O atoms from the 8‐HOXQ ligand, giving rise to a tetrahedral CuP2NO coordination geometry. The electronic absorption and photoluminescence properties of this complex have been studied on as‐synthesized samples, whose purity had been determined by powder X‐ray diffraction. In the detailed TD–DFT (time‐dependent density functional theory) studies, the yellow emission appears to be derived from the inter‐ligand charge transfer and metal‐to‐ligand charge transfer (M +L ′)→LCT excited state (LCT is ligand charge transfer).  相似文献   

11.
α-Carbohydrated pyridinyl sulfones, prepared from commercially available d-(−)-ribose, d-(+)-galactose, and d-(+)-glucose through a five-step sequence, have been employed in the Julia–Lythgoe–Kocienski olefination with aldehydes. This one-pot protocol, using solid KOH at room temperature, affords the corresponding glycosidic enol ethers in moderate to excellent yields and (E)-stereoselectivities. These glycosylated adducts undergo hetero-Diels–Alder reactions with 2-formyl-1-malondialdehyde to afford 2′,5′-dideoxygenated disaccharides in good yields and complete regio- and endo-selectivity. Alternatively, the [2+2]-cycloaddition reaction of the glycosidic enol ethers with chlorosulfonyl isocyanate provided glycosylated β-lactams regioselectively and with only trans-stereoselectivity. The β-lactams could be converted to N-methylthio derivatives which show decent antibacterial activity toward methicillin-resistant strains of Staphylococcus aureus.  相似文献   

12.
In 2′,5′‐dimethyl‐p‐terphenyl, C20H18, which displays pseudosymmetry (the true space group is Pna21, but less satisfactory refinement can also be achieved in Pbcn), the mol­ecules are linked into chains by two short C—H⋯π inter­actions to the centroid of the central ring. In 2′,5′‐bis­(bromo­meth­yl)‐p‐terphenyl, C20H16Br2, the polar CH2Br groups cause mol­ecules to aggregate via C—H⋯Br and Br⋯Br inter­actions, forming a layer structure, in which the phenyl rings project outwards from the central, more polar, region.  相似文献   

13.
The molecular structure of isolated canonical 2′-deoxyrinobucleosides was calculated using the density functional theory. It was demonstrated that the geometry of the base unit (BU) is almost unchanged compared to free nucleobases. Only slight out-of-plane deformation of the pyrimidine ring in deoxy-cytidine is observed. The conformation of the furanose ring strongly depends on the nature and orientation of the nucleobase. All nucleosides possess different conformations of this ring. Significant influence of the steric repulsion between the nucleobase and the sugar unit (SU) on puckering of the furanose ring and variation of the C–O and glycosyl bond lengths was demonstrated. The C(3′)-endo conformer of the furanose ring is more stable at the anti-orientation BU with respect to SU. An opposite trend is observed for the syn-orientation which is additionally stabilized by an intramolecular hydrogen bond with participation of the C(5′)OH group.  相似文献   

14.
The ligands 11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine and 2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole have been coordinated to ReI, CuI, RuII and IrIII metal centres. Single‐crystal X‐ray analyses were performed on fac‐chlorotricarbonyl(11‐cyanodipyrido[3,2‐a:2′,3′‐c]phenazine)rhenium (C22H9ClN5O3Re, a=6.509(5), b=12.403(5), c=13.907(5) Å, α=96.88(5), β=92.41(5), γ=92.13(5)°, triclinic, P , Z=2) and bis‐2,2′‐bipyridyl(2‐(11‐dipyrido[3,2‐a:2′,3′‐c]phenazine)‐5‐phenyl‐1,3,4‐oxadiazole)ruthenium triflate ? 2 CH3CN (C52H36F6N12O8RuS2, a=10.601(5), b=12.420(5), c=20.066(5) Å, α=92.846(5), β=96.493(5), γ=103.720(5)°, triclinic, P , Z=2). The ground‐ and excited‐state properties of the ligands and complexes have been investigated with a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited‐state lifetime studies. Spectroscopic, time‐resolved and DFT studies reveal that the ligand‐centred (LC) transitions and their resultant excited states play an important role in the photophysical properties of the complexes. Evidence for the presence of lower‐lying metal‐to‐ligand charge‐transfer transitions is obtained from resonance Raman spectroscopy, but nanosecond transient Raman experiments suggest that once excited, the 3LC state is populated.  相似文献   

15.
16.
The molecular structures of trichlorido(2,2′:6′,2′′‐terpyridine‐κ3N,N′,N′′)gallium(III), [GaCl3(C15H11N3)], and tribromido(2,2′:6′,2′′‐terpyridine‐κ3N,N′,N′′)gallium(III), [GaBr3(C15H11N3)], are isostructural, with the GaIII atom displaying an octahedral geometry. It is shown that the Ga—N distances in the two complexes are the same within experimental error, in contrast to expected bond lengthening in the bromide complex due to the lower Lewis acidity of GaBr3. Thus, masking of the Lewis acidity trends in the solid state is observed not only for complexes of group 13 metal halides with monodentate ligands but for complexes with the polydentate 2,2′:6′,2′′‐terpyridine donor as well.  相似文献   

17.
A novel anhydrogalactosucrose derivative 2′‐methoxyl‐O‐1′,4′:3′,6′‐dianhydro‐βD‐fructofuranosyl 3,6‐anhydro‐4‐chloro‐4‐deoxy‐αD‐galactopyranoside ( 4 ) was prepared from 3,6:1′,4′:3′,6′‐trianhydro‐4‐chloro‐4‐deoxy‐galactosucrose ( 3 ) via a facile method and characterized by 1H NMR, 13C NMR and 2D NMR spectra. The single crystal X‐ray diffraction analysis shows that the title molecule forms a two thee‐dimensional network structure by two kinds of hydrogen bond interactions [O(2) H(2)···O(7), O(5) H(5)···O(8)]. Its stability was investigated by acid hydrolysis reaction treated with sulfuric acid, together with the formation of 1,6‐Di‐O‐methoxy‐4‐chloro‐4‐deoxy‐βD‐galactopyranose ( 5 ) and 2,2‐Di‐C‐methoxy‐1,4:3,6‐dianhydromannitol ( 6 ). According to the result, the relative stability of the ether bonds in the structure is in the order: C(1) O C(5)≈C(3′) O C(6′)≈C(1′) O C(4′)>C(3) O C(6)≈C(1) O C(2′)>C(2′) O C(5′).  相似文献   

18.
A new inorganic–organic hybrid based on an aspartate functionalized polyoxomolybdate, [pentaaquacobalt(II)]‐μ‐aspartate‐[γ‐octamolybdate]‐μ‐aspartate‐[pentaaquacobalt(II)] tetrahydrate, [Co2(C4H6NO4)2(γ‐Mo8O26)(H2O)10]·4H2O ( 1 ), has been synthesized under hydrothermal conditions from the reaction of an Evans–Showell‐type polyoxometalate, (NH4)6[Co2Mo10H4O38], and l ‐aspartic acid. The complex exhibits a supramolecular three‐dimensional framework structure in the crystal lattice. Compound 1 was structurally characterized by elemental analyses, IR and UV–Vis (diffuse reflectance) spectroscopy and single‐crystal X‐ray diffraction. In this compound, aspartic acid acts as a bridge between the two Co atoms and the Mo centres, with the –CH2COOH side chain directly linked to the Mo centre in γ‐[Mo8O26]4? and the α‐carboxylate side chain bound to the Co centre. Commonly, the binding of transition‐metal complexes to POMs involves coordination of the metal to a terminal O atom of the POM so that 1 , with a bridging ligand between Mo and Co atoms, belongs to a separate class of hybrid materials. While the starting materials are both chiral and one might expect them to form a chiral hybrid, the decomposition of the chiral Evans–Showell‐type POM and its conversion to the centrosymmetric γ‐octamolybdate POM, plus the presence of two aspartate ligands centrosymmetrically placed on either side of the POM, leads to the formation of an achiral hybrid. We have studied energetically by means of density functional theory (DFT) calculations and using the Bader's `atoms‐in‐molecules' analysis the electrostatically enhanced hydrogen bonds (EEHBs) observed in the solid state of 1 , which are crucial for the formation of one‐dimensional supramolecular assemblies.  相似文献   

19.
Sodium bis[2‐(3′,6′,9′‐trioxadecyl)‐1,2‐dicarba‐closo‐dodecaborane‐1‐carboxylato]triphenylstannate, [(CH3OCH2CH2OCH2CH2OCH2CH2)‐1,2‐C2B10H10‐9‐COO)2SnPh3]? Na+, compound 1, was synthesized by the 1:1 condensation of triphenyltin(IV) hydroxide with 2‐(3′,6′,9′‐trioxadecyl)‐1,2‐dicarba‐closo‐dodecaborane‐1‐carboxylic acid and crystallized in the presence of sodium bicarbonate. Its structure was determined by spectroscopy, elemental analysis and X‐ray diffraction. The structure of 1 consists of trigonal bipyramidal [Sn(Ph)3(L)2]? anions and Na+ cations coordinated by oxygen atoms of polyoxaalkyl chains of different stannate anions, forming cation–anion chains elongated along the c axis. Compound 1 is significantly more active in vitro against seven tumour cell lines of human origin than 5‐fluorouracil, cis‐platin, carboplatin, and previously reported organotin carboranecarboxylates, but is less active than organotin polyoxaalkylcarboxylates. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

20.
An unusual heterobimetallic bis(triphenylphosphane)(NO2)AgI–CoIII(dimethylglyoximate)(NO2) coordination compound with both bridging and terminal –NO2 (nitro) coordination modes has been isolated and characterized from the reaction of [CoCl(DMGH)2(PPh3)] (DMGH2 is dimethylglyoxime or N,N′‐dihydroxybutane‐2,3‐diimine) with excess AgNO2. In the title compound, namely bis(dimethylglyoximato‐1κ2O,O′)(μ‐nitro‐1κN:2κ2O,O′)(nitro‐1κN)bis(triphenylphosphane‐2κP)cobalt(III)silver(I), [AgCo(C4H7N2O2)2(NO2)2(C18H15P)2], one of the ambidentate –NO2 ligands, in a bridging mode, chelates the AgI atom in an isobidentate κ2O,O′‐manner and its N atom is coordinated to the CoIII atom. The other –NO2 ligand is terminally κN‐coordinated to the CoIII atom. The structure has been fully characterized by X‐ray crystallography and spectroscopic methods. Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) have been used to study the ground‐state electronic structure and elucidate the origin of the electronic transitions, respectively.  相似文献   

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