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1.
Weakly bound dimer complexes FH—CO and FH—OC were investigated using various ab initio and density function theory (DFT) methods. This study compares the strengths of the H—C H‐bond in FH—CO and the H—O H‐bond in FH—OC. The energy difference between dimers, the H‐bond energy, the inter‐monomer distance, the inter‐monomer vibration frequencies, the red shift of the HF stretching frequency, and the elongation of HF bond, all demonstrate that the H—C H‐bond is stronger than the related H—O H‐bond, according to all methods. The calculated Gibbs energies of the formation of the two dimers show that the weakly bound complexes are unstable at room temperature (T = 298 K) and ordinary pressure (P = 1 atm). However, decreasing T or increasing P monotonically decreases ΔG and increases the related equilibrium constant, K, of their dimer formation. 相似文献
2.
Gene‐Hsiang Lee Hsin‐Ta Wang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m216-m219
N,N′‐Bis(4‐pyridylmethyl)oxalamide, C14H14N4O2, exists as a dimer which is extended into a two‐dimensional network with other dimers through pyridine–amide hydrogen bonds. The crystal structure of the title coordination polymer, {[CoCl2(C14H14N4O2)]·0.5H2O}n, features a one‐dimensional zigzag chain, in which the cobalt ion sits at a twofold symmetry position and adopts a tetrahedral geometry, and the bridging ligand lies on an inversion center and connects to CoII ions in a bis‐monodentate mode. Furthermore, two interwoven chains create a cavity of ca 8.6 × 8.6 Å, which produces a three‐dimensional channel. Water molecules are held in the channel by hydrogen bonds. 相似文献
3.
Alvaro S. de Sousa Zanele Hlam Manuel A. Fernandes Helder M. Marques 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(11):o553-o556
The achiral meso form of the title compound, C18H38N2O42+·2Cl−, crystallizes to form undulating layers consisting of chains linked via weak hydroxyalkyl C—H...Cl contacts. The chains are characterized by centrosymmetric hydrogen‐bonded dimers generated via N—H...Cl and hydroxycycloalkyl O—H...Cl interactions. trans‐N‐Alkyl bridges subdivide the chains into hydrophilic segments flanked by hydrophobic cycloalkyl stacks along [001]. 相似文献
4.
Xiabing Li Dr. Daniele Leonori Dr. Nadeem S. Sheikh Prof. Iain Coldham 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7724-7730
The lithiation of N‐tert‐butoxycarbonyl (N‐Boc)‐1,2,3,4‐tetrahydroisoquinoline was optimized by in situ IR (ReactIR) spectroscopy. Optimum conditions were found by using n‐butyllithium in THF at ?50 °C for less than 5 min. The intermediate organolithium was quenched with electrophiles to give 1‐substituted 1,2,3,4‐tetrahydroisoquinolines. Monitoring the lithiation by IR or NMR spectroscopy showed that one rotamer reacts quickly and the barrier to rotation of the Boc group was determined by variable‐temperature NMR spectroscopy and found to be about 60.8 kJ mol?1, equating to a half‐life for rotation of approximately 30 s at ?50 °C. The use of (?)‐sparteine as a ligand led to low levels of enantioselectivity after electrophilic quenching and the “poor man’s Hoffmann test” indicated that the organolithium was configurationally unstable. The chemistry was applied to N‐Boc‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline and led to the efficient synthesis of the racemic alkaloids salsolidine, carnegine, norlaudanosine and laudanosine. 相似文献
5.
Giovanni Grassi Massimiliano Cordaro Giuseppe Bruno Francesco Nicol 《Helvetica chimica acta》2002,85(1):196-205
The structures of 6‐methyl‐4,8,9‐triphenyl‐2‐oxa‐3,7‐diazaspiro[4.4]nona‐3,6‐dien‐1‐one ( 3 ) and N‐[(2‐Methyl‐4,5‐diphenyl‐1H‐pyrrole‐3‐carbonyl)oxy]benzamide ( 4 ) were established by X‐ray crystal‐structure analysis. A significant improvement in the procedure currently available for the synthesis of these compounds is described. Ab initio and DFT calculations were carried out on the compound 4 and its precursor 3 , and compared with X‐ray results. In particular, to relate structural features to biological properties, the conformational characteristics and rotational barrier of compound 4 were studied. 相似文献
6.
Yansong J. Lu Bin Hu Mahavir Prashad Shaum Kabadi Oljan Repi
Thomas J. Blacklock 《Journal of heterocyclic chemistry》2006,43(4):1125-1127
7.
Dr. M. Luz Raposo Dr. Fernando Fernández‐Nieto Prof. Luis Garcia‐Rio Dr. P. Rodríguez‐Dafonte Dr. M. Rita Paleo Prof. F. Javier Sardina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(29):9677-9685
Kinetic study of the α‐lithiation of benzyl methyl ether (BME) by nBuLi has revealed that increasing the concentration of the organolithium compound does not necessarily increase the reactivity, and this is a consequence of the reactivities of the different nBuLi aggregates present in solution. We propose a dimer‐based mechanism, in which a pre‐complexation step is a key process for substrates bearing a donor oxygen atom that can interact with the lithium cation to form mixed dimers. For these studies, we have developed a system based on UV/Vis spectroscopy that allows kinetic measurements to be conducted at ?80 °C under argon. 相似文献
8.
Eike Gellermann Uwe Klingebiel Thomas Pape Fabio Dall Antonia Thomas R. Schneider Stefan Schmatz 《无机化学与普通化学杂志》2001,627(12):2581-2588
Silylhydrazines and Dimeric N,N′‐Dilithium‐N,N′‐bis(silyl)hydrazides – Syntheses, Reactions, Isomerisations Di‐tert.‐butylchlorosilane reacts with dilithiated hydrazine in a molar ratio to give the N,N′‐bis(silyl)hydrazine, [(Me3C)2SiHNH]2, ( 5 ). Isomeric tris(silyl)hydrazines, N‐difluorophenylsilyl‐N′,N′‐bis(dimethylphenylsilyl)hydrazine ( 7 ) and N‐difluorophenylsilyl‐N,N′‐bis(dimethylphenylsilyl)hydrazine ( 8 ) are formed in the reaction of N‐lithium‐N′‐N′‐bis(dimethylphenylsilyl)hydrazide and F3SiPh. Isomeric bis(silyl)hydrazines, (Me3C)2SiFNHNHSiMe2Ph ( 9 ) and (Me3C)2‐ SiF(PhMe2Si)N–NH2 ( 10 ) are the result of the reaction of di‐tert.‐butylfluorosilylhydrazine and ClSiMe2Ph in the presence of Et3N. Quantum chemical calculations for model compounds demonstrate the dyotropic course of the rearrangement. The monolithium derivative of 5 forms a N‐lithium‐N′,N′‐bis(silyl)hydrazide ( 11 ). The dilithium salts of 5 ( 13 ) and of the bis(tert.‐butyldiphenylsilyl)hydrazine ( 12 ) crystallize as dimers with formation of a central Li4N4 unit. The formation of 12 from 11 occurs via a N′ → N‐silyl group migration. Results of crystal structure analyses are reported. 相似文献
9.
B. Mannfors N. G. Mirkin K. Palmo S. Krimm 《Journal of computational chemistry》2001,22(16):1933-1943
Our previously developed polarizable electrostatic model is applied to isolated N‐methylacetamide (NMA) and to three hydrogen‐bonded configurations of the NMA dimer. Two versions of the model are studied. In the first one (POL1), polarizability along the valence bonds is described by induced bond charge increments, and polarizability perpendicular to the bonds is described by cylindrically isotropic induced atomic dipoles. In the other version (POL2), the induced bond charge increments are replaced by induced atomic dipoles along the bonds. The parameterization is done by fitting to ab initio MP2/6‐31++G(d,p) electric potentials. The polarizability parameters are determined by subjecting the NMA molecule to various external electric fields. POL1 turns out to be easier to optimize than POL2. Both models reproduce well the ab initio electric potentials, molecular dipole moments, and molecular polarizability tensors of the monomer and the dimers. Nonpolarizable models are also investigated. The results show that polarization is very important for reproducing the electric potentials of the studied dimers, indicating that this is also the case in hydrogen bonding between peptide groups in proteins. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1933–1943, 2001 相似文献
10.
Sharmila Basu Soumen Ghosh Somnath Ghosh Madeleine Helliwell Alok K. Mukherjee 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(11):o595-o598
The title compound, C25H35N3O2, is a novel urea derivative. Pairs of intermolecular N—H...O hydrogen bonds join the molecules into centrosymmetric R22(12) and R22(18) dimeric rings, which are alternately linked into one‐dimensional polymeric chains along the [010] direction. The parallel chains are connected via C—H...O hydrogen bonds to generate a two‐dimensional framework structure parallel to the (001) plane. The title compound was also modelled by solid‐state density functional theory (DFT) calculations. A comparison of the molecular conformation and hydrogen‐bond geometry obtained from the X‐ray structure analysis and the theoretical study clearly indicates that the DFT calculation agrees closely with the X‐ray structure. 相似文献
11.
Giuseppe Bruno Santo Lanza Francesco Nicol Giuseppe Tresoldi Giuseppe Rosace 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(10):o608-o609
The title compound, alternatively known as N,N′‐dibenzylethanedithioamide, C16H16N2S2, lies about an inversion centre and contains a planar trans‐dithiooxamide fragment characterized by a strong intramolecular hydrogen bond between the S atom and the adjacent amide H atom in the solid state, with an S?N distance of 2.926 (1) Å. The aryl substituent is oriented orthogonal to the mean plane of the trans‐dithiooxamide fragment due to steric hindrance and this effect is discussed. 相似文献
12.
Jaromír Marek Pavel Kopel Zdenk Trvní
ek 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):m558-m560
In the crystal structure of the title compound, [N,N′‐bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trithionato(2−)‐κ2N,S]zinc(II) ethanol solvate, [Zn(C8H22N4)2(C3HN3S3)]·C2H6O, the ZnII atom is octahedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐aminopropyl)ethylenediamine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a trithiocyanurate(2−) (ttcH2−) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds. 相似文献
13.
Zoran tefani Anton Meden Martin Lutz Antoine M. M. Schreurs Biserka Koji‐Prodi 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):o754-o756
The title compound, rac‐(R,R)‐N,N′‐bis(1‐hydroxy‐3‐methyl‐2‐butyl)oxalamide, C12H24N2O4, crystallizes as a non‐merohedral twin in the triclinic space group . The twin is generated by a twofold rotation about c*. The terminal hydroxy groups of molecules related by an inversion center form hydrogen‐bonded dimers. This hydrogen‐bonding pattern is further extended into a one‐dimensional chain by N—H⋯O hydrogen bonds. 相似文献
14.
Niyazi Biak Bahire Filiz enkal Tuba imanolu Cemal
zerolu 《Journal of polymer science. Part A, Polymer chemistry》2000,38(6):1006-1013
N,N,N′,N′‐tetraallyl piperazinium dibromide (TAP) has been prepared in high yields by quaternization of N,N′‐diallyl piperazine with allyl bromide. Herein, we have described preparation of nonhydrolysable, strong, cationic hydrogels by copolymerization of TAP with N,N‐diallyl morpholinium bromide (DAM) in the presence of t‐butyl hydroperoxide as initiator in aqueous solutions. Because the monomer and crosslinker involved consist of quaternary amine functions, these hydrogels are fully cationic and do not carry hydrolysable groups. Contrary to expectations, the quaternary amine hydrogels presented do not show any super absorbency, instead dry gel particles in water undergo spontaneous disintegration with an audible bursting of the particles due to instantaneous, high osmotic pressure. Whereas, in KBr or HBr solutions, the swellings are relatively slow. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1006–1013, 2000 相似文献
15.
Kazuo Yokokawa Ken Sakai 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(6):m244-m247
The title compound, [Pt2III(C5H10NO)2(SO4)2(C10H8N2)2]·4H2O, is the first reported example of a complex in which an amidate‐bridged Pt(bpy) dimer is stabilized in the oxidation level of PtIII (bpy is 2,2′‐bipyridine). The asymmetric unit consists of one half of the formula unit with a twofold axis passing through the center of the dimer. The intradimer PtIII—PtIII bond distance [2.5664 (6) Å] is comparable to those reported for α‐pyridonate‐bridged cis‐diammineplatinum(III) dimers [2.5401 (5)–2.5468 (8) Å; Hollis & Lippard (1983). Inorg. Chem. 22 , 2605–2614], in spite of the close contact between the bpy planes within the dimeric unit. The axial Pt—Osulfate distance is 2.144 (7) Å. 相似文献
16.
Teshica Chatturgoon Matthew P. Akerman 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(3):234-238
The application of transition metal chelates as chemotherapeutic agents has the advantage that they can be used as a scaffold around which ligands with DNA recognition elements can be anchored. The facile substitution of these components allows for the DNA recognition and binding properties of the metal chelates to be tuned. Copper is a particularly interesting choice for the development of novel metallodrugs as it is an endogenous metal and is therefore less toxic than other transition metals. The title compound, [Cu(C16H11N2O)2], was synthesized by reacting N‐(quinolin‐8‐yl)benzamide and the metal in a 2:1 ratio. Ligand coordination required deprotonation of the amide N—H group and the isolated complex is therefore neutral. The metal ion adopts a flattened tetrahedral coordination geometry with the ligands in a pseudo‐trans configuration. The free rotation afforded by the formal single bond between the amide group and phenyl ring allows the phenyl rings to rotate out‐of‐plane, thus alleviating nonbonded repulsion between the phenyl rings and the quinolyl groups within the complex. Weak C—H…O interactions stabilize a dimer in the solid state. Density functional theory (DFT) simulations at the PBE/6‐311G(dp) level of theory show that the solid‐state structure (C1 symmetry) is 79.33 kJ mol−1 higher in energy than the lowest energy gas‐phase structure (C2 symmetry). Natural bond orbital (NBO) analysis offers an explanation for the formation of the C—H…O interactions in electrostatic terms, but the stabilizing effect is insufficient to support the dimer in the gas phase. 相似文献
17.
Dr. Chang‐Qi Ma Dr. Elena Mena‐Osteritz Dr. Markus Wunderlin Dr. Gisela Schulz Prof. Dr. Peter Bäuerle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12880-12901
The synthesis of generational dendritic oligothiophenes (DOTs) has been successfully achieved by a divergent/convergent approach that involves halogenation, boronation, and palladium‐catalyzed Suzuki coupling reactions. The key point in the presented synthetic approach is the use of trimethylsilyl (TMS) protecting groups, which allow for the core‐lithiation and subsequent boronation of the dendrons and for the peripheral ipso‐substitution with iodine monochloride or N‐bromosuccimide. In addition, the TMS protecting groups can be completely removed by using tetrabutylammonium fluoride, thus yielding only‐thiophene‐based dendrons and dendrimers. Due to their highly branched structure, all these synthesized DOTs are soluble in organic solvents. Chemical structures were confirmed by NMR spectroscopic, mass spectrometric, and elemental analysis. Concentration‐dependent 1H NMR spectroscopic investigations revealed that the higher generation compounds tend to aggregate in solution. Such an aggregation behavior was further confirmed by measuring with MALDI‐TOF MS. Both MALDI‐TOF MS and gel‐permeation chromatography (GPC) analyses confirmed the monodispersity of the DOTs. Furthermore, GPC results revealed that these DOT molecules adopt a condensed globular molecular shape. Their optical and electronic properties were also investigated. The results indicated that these DOTs comprise various conjugated α‐oligothiophenes with different chain lengths, which results in the higher generation compounds showing broad and featureless UV/Vis absorption spectra and ill‐defined redox waves. 相似文献
18.
Abdulnasir A. Majeed Mostafa M.H. Khalil Ahmed Fetoh Ayman A. Abdel Aziz G.M. Abu El‐Reash 《应用有机金属化学》2021,35(1)
In this work, (Z)‐N‐benzoyl‐N′‐(1H‐1,2,4‐triazol‐3‐yl)carbamimidothioic acid and its Mn(II), Co(II), Cu(II) and Cd(II) complexes were introduced for the first time. This carbonyl thiourea ligand was prepared by the reaction of 1H‐1,2,4‐triazol‐3‐amine with benzoyl isothiocyanate. The structural elucidation of these compounds was performed using elemental analysis and spectral and magnetic measurements. Octahedral structures of all complexes, except Cd(II) complex with a tetrahedral geometry, were confirmed by applying DFT structural optimization. The thermal decomposition behaviour of metal complexes of carbonyl thiourea ligand is discussed. The calculation of kinetic parameters for prepared complexes (Ea, A, ΔH*, ΔS* and ΔG*) of all thermal degradation stages has been evaluated using two comparable approaches. Antimicrobial and ABTS‐antioxidant studies indicated potent activity of Cd(II) complex compared with the other investigated compounds. The cytotoxic activity of the prepared compounds was investigated in vitro. The results indicated potent activity of Mn(II) complex against both HePG2 (liver carcinoma) and MCF‐7 (breast carcinoma) cancer cells. 相似文献
19.
Jocelyn C. Bruce Klaus R. Koch 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m1-m4
The crystal and molecular structures of N‐benzoyl‐N′,N′‐dibutylselenourea (HL), C16H24N2OSe, and the corresponding complex bis(N‐benzoyl‐N′,N′‐dibutylselenoureato‐κ2Se,O)palladium(II), [Pd(C16H23N2OSe)2], are reported. The selenourea molecule is characterized by intermolecular hydrogen bonds between the selenoamidic H atom and the Se atom of a neighbouring molecule forming a dimer, presumably as a consequence of resonance‐assisted hydrogen bonding or π‐bonding co‐operativity. A second dimeric hydrogen bond is also described. In the palladium complex, the typical square‐planar coordination characteristic of such ligands results in a cis‐[Pd(L‐Se,O)2] complex. 相似文献
20.
Diyun Huang Cheng Zhang Larry R. Dalton William P. Weber 《Journal of polymer science. Part A, Polymer chemistry》2000,38(3):546-559
An ω‐amino carboxylic acid monomer that contained a nonlinear optical (NLO) chromophore was prepared by a convergent synthesis. Strategies for selective protection/deprotection of the amino and carboxylic acid functionalities were developed. The protected monomer, 4‐[N‐(4‐benzyloxycarbonyl)butyl‐N‐methylamino]‐4′‐[2″,5″‐bis(decyloxy)‐4″‐(phthalimidomethyl)benzylsulfonyl]azobenzene, could be deprotected selectively or sequentially to give HOOC‐monomer‐N‐phthaloyl, benzyl‐OOC‐monomer‐NH2, or HOOC‐monomer‐NH2. Sequential synthesis was performed to yield main‐chain NLO dimers and tetramers. This was accomplished by selective deprotection and dicyclohexylcarbodiimide coupling. The HOOC‐monomer‐NH2 was polymerized by treatment with diphenylphosphoryl azide to give a main‐chain NLO polyamide. The monomer, dimer, tetramer, and polymer NLO materials were characterized by 1H, 13C, IR, and UV–visible spectroscopy as well as by gel permeation chromatography, differential scanning calorimetry, and elemental analysis. The NLO properties of these materials were measured. Thin films of the oligomers and polymer were prepared by spin casting on indium‐tin oxide coated glass. The second‐order NLO properties of the oligomers and polymer thin films were studied by in situ corona poling/second‐harmonic generation and attenuated total reflection methods. The optimal poling temperatures were significantly lower than the melting temperatures or glass‐transition temperatures of the oligomers and polymer. The poling efficiency increased in the following order: monomer, oligomers, and polymer. An electro‐optic coefficient of 4 pm/V at 1.06 μm was obtained for the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 546–559, 2000 相似文献