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1.
Crystal structure determination and semiempirical AM1 and PM3 calculations were performed on flutamide {2-methyl-N[4 nitro-3-(trifluoromethyl) phenyl] propamide}, a powerful nonsteroidal androgen antagonist. The molecule is almost planar apart from CF3, NO2, and CH3 groups. The NO2 plane makes an angle of 36.3(4) with the least-square plane of the phenyl ring. The molecules are intermolecularly linked by one N-H O and one C-H O hydrogen bonds. A bifurcated helicoidal hydrogen bond network is formed by the intermolecular C-H O hydrogen bond together with another intramolecular C-H O hydrogen bond. The calculated structures are in good agreement with the crystallographic conformations. AM1 is more accurate for predicting the intramolecular C-H O hydrogen bond while PM3 gives a better geometry for the crowded nitro group. AM1 and PM3 charges of benzenic hydrogens are used to predict the propensity of these atoms to form hydrogen bonds. The noncentrosymmetric space group of the crystal (Pna21), the calculated dipole moment (8.88 D), and the calculated angle between molecular dipoles and the twofold axis (–49) close to the optimal value (54.7) indicate that flutamide might be a possible candidate for nonlinear optical material.  相似文献   

2.
Qualitative and quantitative information about the interspecies distance distributions in aqueous hydroxylammonium nitrate (HAN) is obtained as a function of concentration (7 to 17M), temperature (–120 to 60°C) and pressure (0.1 to 7100 MPa) using isotopic uncoupling techniques for the O-HO and N-HO hydrogen bonds in conjunction with frequency-distance correlations.  相似文献   

3.
Summary Quantum chemical ab initio calculations have been performed for the complex CO2HF and N2OHF. The interaction energies were computed through fourth order MBPT and were corrected for basis set superposition errors. Extended polarized basis sets were used which are constructed to give accurate values for electric moments and polarizabilities. The complex NNOHF was found to be bent, while OCOHF is linear, in agreement with experiment. The MBPT calculations give evidence for a second linear isomeric structure FHNNO, a possibility which has also been suggested by recent experimental data. The computed binding energies are: 2.5 kcal/mol for OCOHF, 2.4 kcal/mol for NNOHF, and 3.0 kcal/mol for FHNNO. At the SCF level, the FHNNO complex is less stable than NNOHF, but correlation has a large effect on the geometry and energetics of the latter complex. The NNOHF complex seems to be a system where the positive intramolecular correlation correction prevails over the negative intermolecular component.  相似文献   

4.
The structure and harmonic vibrational frequencies of several weakly bound complexes formed by HF are reported. Theab initio MP2 approach is used with large basis sets for the optimisation of geometries and the determination of harmonic frequencies. COHF and OCHF are examined; both are found to be minima, with the latter being the dominant structure. The linear OCOHF andT shaped OCOFH are studied, but only the linear structure is a minimum. N2OHF has two minima on the surface corresponding to bent NNOHF and linear ONNHF structures.  相似文献   

5.
Calculations on the hydrogen-bonded complexes HCNHF, H2OHF, ClCNHCl and (CH3)2OHCl are reported. SCF harmonic values for the HF and HCl frequency shifts are in considerable disagreement with experiment, by as much as 100 cm–1. Calculations at the MP2 (harmonic) level yield improved agreement with experiment, reducing discrepancies to the order of 10 cm–1. We have also calculated all the cubic and quartic force constants for HCNHF at the SCF level, so that the anharmonic constants, x rs can be evaluated. Although x 11 (v 1=H-F stretch) is large and negative, it is more than compensated by a positive x 16 (v 6=NH-F bend), so that the anharmonic correction to v 1 is small and positive. The validity of these anharmonistudies is examined.  相似文献   

6.
Summary The influence of Na+ on hydrogen bonds of the OH O and NH O type between an aliphatic amino acid (glycine zwitterion) and water is investigated byab initio calculations with minimal Gaussian basis sets. Distortion of the hydration shell caused by Na+, and interaction energies contributing to the over-all stabilization are discussed.
Der Einfluß von Na+ auf die benachbarten Wasserstoffbindungen in aliphatischen Aminosäuren
Zusammenfassung Der Einfluß von Na+ auf die Wasserstoffbindungen vom OH O- und NH O-Typ in aliphatischen Aminosäuren (Glycin-Zwitterion) und Wasser wurde mittelsab initio Berechnungen mit einem minimalen Gausschen Basissatz untersucht. Die durch Na+-Ionen hervorgerufenen Verzerrungen der Hydratationsschale und die zur Gesamtstabilisierung beitragenden Wechselwir-kungsenergien werden diskutiert.
  相似文献   

7.
The title complex, [Cu(NiL)2(H2O)2](ClO4)2, has been obtained by self-assembly, where [NiL] is a new macrocyclic oxamido complex ligand. In the crystal, a new kind of supramolecular interaction between the carbon atoms of the oxamido group of each [NiL] complex ligand in a [Cu(NiL)2(H2O)2]2 + cation and the oxygen atom of one of the ester carbonyls of another [Cu(NiL)2(H2O)2]2 + cation, and C—HO, O—HO and interactions are observed and link the trinuclear fragments and perchlorate ions to form a 3D supramolecular network.  相似文献   

8.
Based on results of ab initio (6–31G and ECP) calculations, new data on the mutual effect of hydrogen bonds in (HHal)n · H2O · ((CH3)2O)m (n = 0, 1, 2; m = 0, 1, 2) aquacomplexes have been obtained. It is shown that the Hbonds formed by the lone electrons of the oxygen atom of the water molecule (by 20%) weaken each other significantly. The enthalpy of formation of HOH...O(CH3)2 bonds depends on which and how many halogen hydride molecules are bound with the water molecule via its lone electrons. But the ratio of the strengths of the HOH...O(CH3)2 bonds formed by the fragment (HHal)n · H2O (n = 0, 1, 2) with one and with two molecules of dimethyl ether remains virtually constant ( 10%).  相似文献   

9.
An x-ray diffraction structural analysis was carried out on 1H+,10H+-1,10-diazonia-18-crown-6 diethyldithiophosphate, which exists in the crystal as isolated ionic hydrogen-bonded complexes [H2DA18C6]2+·2(EtO)2PS2 with strong inter-ion N-HS hydrogen bonds. The centrosymmetric DA18C6 dication has an unusual two-cornered conformation stabilized by a pair of weak intra-ring furcated OH(N)O hydrogen bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 190–192, January, 1991.  相似文献   

10.
Gradient extremals on N-dimensional energy hypersurfaces V=V(x 1 x n ) are curves defined by the condition that the gradient V is an eigenvector of the hessian matrix V. For variations which are restricted to any (N–1) dimensional hypersurface V(x 1 x N ) = V 0= constant, the absolute value of the gradient V is an extremum at those points where a gradient extremal intersects this surface. In many, though not all, cases gradient extremals go along the bottom of a valley or along the crest of a ridge. The properties of gradient extremals are discussed through a detailed differential analysis and illustrated by an explicit example. Multidimensional generalizations of gradient extremals are defined and discussed.Operated for the U.S. Department of Energy by Iowa State University under Contract No. W-7405-ENG-82. This work was supported by the Office of Basic Energy Sciences  相似文献   

11.
Transition probabilities and oscillator strengths are calculated for the configurations 1s2 2sn1 and 1s2 2sn1-1 2pn2+1, which are, respectively, of the form P=a/Z (1+/Z+) andf=/Z (1+/Z+). Numerical values are given fora, ,, and.  相似文献   

12.
This paper reports on an X-ray diffraction analysis of host–guest type molecular complexes of 18-crown-6 with 1,2,5-oxadiazole derivatives: ethyl 4-amino-1,2,5-oxadiazole-3-carboxylic ether (1:1) (complex I), 4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid hydrazide (1:2) (complex II), and 4-amino-1,2,5-oxadiazole-3-carboxylic acid amide monohydrate (1:1:1) (complex III). Crystals I are monoclinic with cell parameters a = 8.960(2), b = 18.118(4), c = 14.405(3) , = 106.9(3)°, space group P21/n, R = 0.054 for 4082 reflections. The 18-crown-6 and guest molecules are linked by hydrogen bonds of NHO(crown) and CHO(crown) types based on the head-to-tail principle, alternating in infinite chains along the y axis in the crystal. Crystals II are triclinic with cell parameters a = 8.615(2), b = 9.249(2), c = 10.987(2) , = 106.86(3), = 95.25(3), = 97.74(3)°, space group P1, R = 0.046 for 3006 reflections. The guest molecules are united into dimers by N–HO=C hydrogen bonds. The 18-crown-6 molecules and the dimer associates of the guest form chains along [110] in the crystal. Crystals III are monoclinic with cell dimensions a = 13.238(3), b = 19.004(4), c = 8.485(2) , = 100.75(3)°, space group Cc, R = 0.051 for 2032 reflections. The crown ether molecule is disordered over two positions. The NHO=C and NHN type hydrogen bonds link the guest molecules into chains. The water molecules serve to bridge the chains with crown ether molecules, forming ribbons whose axis lies along the z direction in the crystal.  相似文献   

13.
Sodium salicylate (NaSal where Sal=2-hydroxybenzoate), when mixed with dibenzo-24-crown-8 (DB24C8) yields a bimetallic complex [NaSal]2DB24C8 in most polar organic media, while potassium salicylate (KSal) under similar conditions shows a tendency to yield 11 or 21 complexes depending upon medium or synthesis. However, the presence of both NaSal and KSal together results in a unique mixed cation complex of composition NaKSal2DB24C8. This product melts sharply (190-92°C) without decomposition, displays IR spectral characteristics comparable to those of [Na(Sal)]2DB24C8, and is stable in aqueous media as shown by the detectable cation effect on the UV absorption bands of Sal and DB24C8. Single crystal X-ray analysis of NaK(Sal)2DB24C8 reveals that the system represents a co-crystallization complex of individual (KSal)2DB24C8 and (NaSal)2DB24C8 molecules. The crystals are monoclinic,P21/c,a=19.976(2) Å,b=9.031(1) Å,c=25.541(5) Å,=122.065(9)°, Å3,T=298 K,Z=2+2, CuK =1.5418 Å, and 2 (2.5°–100°). FinalR factor for the 3012 observed reflections (F>3) is 0.092. Both the Na2- and K2-molecules possess crystallographic centers of symmetry with one metal and its associated anion on each side of the crown ring. However, the conformations of the crowns are very different in the two molecules, with the K2-crown being nearly planar and the Na2-crown being quite puckered. Four oxygen atoms from the DB24C8 (KO, 2.680–2.908 Å) and three carboxyl oxygen atoms (KO, 2.472–2.708 Å) from separate salicylate ions coordinate with each potassium. Three oxygens from the crown (NaO, 2.536–2.65 Å) and three carboxyl oxygens (NaO, 2.31–2.563 Å) coordinate with each sodium. The salicylate ions lie on opposite sides and nearly perpendicular (77.2°, Na2-molecule; 82.7° K2-molecule) to each crown but coordinate to both of the metal ions within a molecule. The K+K+ and Na+Na+ distances in the respective molecules are 3.95 and 3.34 Å. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82044 (18 pages).  相似文献   

14.
The host compounds 2,2-binaphthyl-3,3-dicarboxylic acid (1) and 1,13–1-terphenyl-2,4,4-tricarboxylic acid (2) have been synthesized, and crystal structures of their inclusion compounds with DMSO {1a [1·DMSO(11)];2a [2·DMSO (12)]} have been determined from single crystal X-ray diffraction data. The crystals show monoclinic symmetry withZ=4 (P21/n for1a andP21/c for2a), with the unit cell dimensionsa=11.567(1),b=10.206(1),c=17.579(1) Å,=100.50(1)° for1a, anda=14.910(1),b=6.732(1),c=26.084(1) Å,=100.41(1)° for2a. The structural models were refined toR=0.032 with 3127 reflections for1a, andR=0.035 with 3175 observations for2a, collected atT=173(1) K. Both structures comprise a characteristic molecular recognition pattern for DMSO via strong (CO)O–HO(=S) hydrogen bonds and possible C–HO contacts, the latter ones from the guest methyl groups to the carbonyl oxygen of the host carboxyl groups. In the crystals H-bonded endless chains of alternating host and guest molecules are formed, which are held together by ordinary van der Waals' forces. Additionally, host2 binds a second DMSO molecule by a single (CO)O–HO(=S) bond.Supplementary Data relating to this article have been deposited with the British Library at Boston Spa, Wetherby, West Yorkshire, U.K., as Supplementary Publication No. SUP 82186 (9 pages)  相似文献   

15.
The preparation, magnetic properties, and crystal structure of [(salen)Cu]4[(salen)Fe(H2O)2]2(ClO4)2 via hydrogen bonding are described [salen=N,N-ethylenebis (salicylideneiminate)]. Crystals are triclinic, of space group , with cell constants a=12.853(3), b=13.921(3), c=14.251(3) Å, =68.68(3)°, =87.86(3)°, =86.82(3)°, and Z=1. The structure was solved and refined to R=0.064 and R=0.068. The structure comprises the hexanuclear units which result from the linking of four mononuclear fragments [(salen)Cu] and two mononuclear fragment [(salen)Fe(H2O)]+, through Cu -O H -O -Fe -O -H O -Cu hydrogen bonds of coordinating H2O. In this complex, FeIII ions are in almost square-planar surroundings. The temperature dependences of the magnetic susceptibilities of the complex have been studied in the 4.2–300 K range, indicating the presence of an antiferromagnetic interactions between metal ions.  相似文献   

16.
To explain the character of the intramolecular hydrogen bond in substituted 3-hydroxypyridines, the chemical shifts in the NMR spectra of the hydroxyl group and the IR spectra were studied. It was established that the stability of the intramolecular hydrogen bond of the O-HNR2 type in substituted 3-hydroxypyridines increases when compared with the corresponding phenols, while an opposite pattern is observed for bonds of the O-H02 N type. An approximate evaluation of the energy of the intramolecular hydrogen bond in substituted 3-hydroxypyridines was achieved. When reacting with bases of the same strength, 3-hydroxypyridine forms more stable complexes than phenol.  相似文献   

17.
4-Aminoethylidene and 4-aminomethylene derivatives of 5-imidazolone exist in the enamine form as two isomers that are stabilized by intramolecular hydrogen bonds of the NHN and NHO type. In solution the enamine with a five-membered H ring is gradually converted to the corresponding isomer with a six-membered H ring with an NHO bond. Because of steric hindrance, rotation about the carbon-carbon double bond is realized more slowly in the aminoethylidene derivatives than in the aminomethylene derivatives of 5-imidazolone.See [1] for communication XXI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1677–1679, December, 1978.  相似文献   

18.
A mixed ligand 12 complex of copper(II) azide with 3,5-lutidine, namely di-(1,1)-azido-di(0,0)-nitrato)tetrakis(3,5-lutidine)dicopper(II) has been prepared and characterized by X-ray crystallographic and spectroscopic methods. The dimeric molecule, which possesses a crystallographic inversion center, contains two(1,1) bridging azido ligands. Each copper(II) atom in the cyclic Cu2N2 unit is further coordinated by two oxygen atoms from two(0,0-nitrato) bridges at Cu-O distances of 2.465(3) and 2.568(3) Å and two nitrogen atoms from the lutidine molecules [Cu-N=2.003(3) and 2.012(3) Å] to give a distorted tetragonal bipyramid. Both azido ligands are linear [N-N-N angle=179.0(4) and asymmetric N-N=1.207(4) and N-N=1.135(5) Å]. The azido bridges produce a rather short Cu Cu distance of 3.013(2) Å. Infrared and electronic data are presented and discussed.  相似文献   

19.
A crystalline 1 : 2 adduct of aquatrifluoroboron and triphenylphosphine oxide 1/2[BF3(H2O)] · Ph3PO(I) is synthesized and studied by X-ray diffraction analysis. The crystals are orthorhombic, space group Fdd2, a = 32.283 Å, b = 20.162 Å, c = 10.191 Å, Z = 16. The structure is solved by the direct method and refined by a full-matrix least-squares method in the anisotropic approximation to R = 0.054 against 2528 independent reflections (CAD4 automated diffractometer, MoK). A Ph3PO molecule has a normal structure. A [BF3(H2O)] molecule is randomly disordered relative to axis 2; populations of positions of all its atoms are 0.5. The boron atom has a distorted tetrahedral coordination with a donor-acceptor B-O(w) bond. In crystal, strong hydrogen bonds of the P=OH-O-HO=P type are formed between the H2O molecule and two Ph3PO molecules.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 1, 2005, pp. 12–16.Original Russian Text Copyright © 2005 by Chekhlov.  相似文献   

20.
Alkorta  Ibon  Rozas  Isabel  Elguero  José 《Structural chemistry》1998,9(4):243-247
It is possible to treat bond distances of covalent C-H bonds and CH hydrogen bonds simultaneously assuming a logarithmic relationship with the electron density at the bond critical point. Similar relationships have been found for other X-H/XH bonds. The data used for obtaining these equations have been determined theoretically. All the systems have been fully optimized and their electron densities calculated at the B3LYP/6-311 + + G(d,p) level.  相似文献   

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