The structure and harmonic vibrational frequencies of the weakly bound complexes formed by HF with CO,CO2 and N2O

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.     

Solid-state mechanochemical synthesis of tris(4-imino-2-pentanonato)chromium,Cr[CH3C(NH)CHC(O)CH3]3

Tris(4-imino-2-pentanonato)chromium was prepared by solid-state synthesis under conditions of mechanical activation of a mixture of chromium(III) chloride and sodium 4-imino-2-pentanonate and characterized by IR spectroscopy, X-ray diffraction, and electronic absorption spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2227–2229, December, 1994.The present work was carried out as a part of Project No. 1.164 Mechanochemical Synthesis of Complex Compounds of The State Scientific and Technical Program Ecologically Safe Processes in Chemistry and Chemical Technology with the financial support of the Ministry of Science of the RF.     

The influence of Na+ on neighbouring hydrogen bonds of aliphatic amino acid

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.

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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.

     

Structure of the Molecular Complexes of 18-Crown-6 with 1,2,5-Oxadiazole Derivatives

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.     

Mutual Weakening of Hydrogen Bonds Between Hydrogen Fluoride and Proton Donors

The mutual effect of hydrogen bonds in BHF(HHal) _n complexes (Hal = F, Cl, Br, I; B = –, CH₃CN, NH₃; n = 1-3) was examined using the self-consistent field ab initio approach (6-31++G(d,p) and ECP-HW). When two and three equivalent H bonds are formed from the lone electron pairs of the fluorine atom of the HF molecule, the mutual weakening effect is 17% and 28%, respectively. The coefficients of the mutual effects of hydrogen bonds in HF(HHal)₂ and H₂O(HHal)₂ bridges are close in magnitude.     

An ab initio study of the structures and enthalpies of the hydrogen-bonded complexes of the acids H2O,H2S,HCN, and HCl with the anions OH−, SH−, CN−, and Cl−

Ab initio calculations at second-order Møller-Plesset perturbation theory with the 6-31 + G(d,p) basis set have been performed to determine the equilibrium structures and energies of a series of negative-ion hydrogen-bonded complexes with H₂O, H₂S, HCN, and HCl as proton donors and OH^–, SH^–, CN^–, and Cl^– as proton acceptors. The computed stabilization enthalpies of these complexes are in agreement to within the experimental error of 1 kcal mol^–1 with the gas-phase hydrogen bond enthalpies, except for HOHOH^–, in which case the difference is 1.8 kcal mol^–1. The structures of these complexes exhibit linear hydrogen bonds and directed lone pairs of electrons except for complexes with H₂O as the proton donor, in which cases the hydrogen bonds deviate slightly from linearity. All of the complexes have equilibrium structures in which the hydrogen-bonded proton is nonsymmetrically bound, although the symmetric structures of HOHOH^– and ClHCl^– are only slightly less bound than the equilibrium structures. MP2/6-31 + G(d,p) hydrogen bond energies calculated at optimized MP2/B-31 + G(d,p) and at optimized HF/6-31G(d) geometries are similar. Using HF/6-31G(d) frequencies to evaluate zero-point and thermal vibrational energies does not introduce significant error into the computed hydrogen bond enthalpies of these complexes provided that the hydrogen-bonded proton is definitely nonsymmetrically bound at both Hartree-Fock and MP2.     

A quantum chemical study of the hydrogen bonding in the CO2⋯HF and N2O⋯HF complexes

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.     

Researches on 2, l, 3-thia- and selenadiazole

4-(,-Dicarboethoxy--acetylamino) ethyl-7-aminobenzo-2,1, 3-thiadiazole (IV) and ethylene oxide form mainly the 7-(-hydroxyethyl) amino derivative (V); the 7- di (-hydroxyethyl) amino derivative VII was isolated in low yield. Action of POCl₃ on compound VII gave the 7-di (-chloroethyl) amino derivative VIII, which was converted into 4-(-amino--carboxy)-ethyl-7 -di (-chloroethyl) aminobenzo-2, 1, 3-thiadiazole (IX). 5-(, -dicarboethoxy--acetylamino) ethyl-4-nitrobenzo-2, 1, 3-thiadiazole (XI) was converted to 5-(-carboxy--amino) ethyl-4-nitrobenzo-2, 1, 3-thiadiazole hydrochloride (XII), from which was prepared, by known routes, and in satisfactory yield, 5-(-carboxy--amino) ethyl-4-di (-chloroethyl)-aminobenzo-2, l, 3-thiadiazole hydrochloride (XVII).For Part XXXIX see [8].     

The geometry of intermolecular interactions in some crystalline fluorine-containing organic compounds

The propensity of C-F groups to form C-F H-C interactions with C-H groups on other molecules has been analyzed. Crystal structures of molecules containing only carbon, hydrogen, and fluorine, but no oxygen, nitrogen, or other hydrogen-bond-forming elements, were chosen for an initial study in which the intermolecular interactions in crystal-structure determinations of polycyclic aromatic hydrocarbons and their analogous fluoro derivatives were analyzed. It is found that C-F H-C interactions occur, but they are weak, as judged by the intermolecular distances and the angles involved. In a study of crystal structures of molecules containing other elements in addition to carbon, hydrogen, and fluorine, it was found that when an oxygen atom is in a neighboring position on an interacting molecule, a C-O group is more likely than a C-F group to form a linear interaction to the hydrogen atom of a C-H group. Thus, in spite of the high electronegativity of the fluorine atom, a C-F group competes unfavorably with a C-O^–, C-OH, or C=O group to form a hydrogen bond to an O-H, N-H, or C-H group. It is found, however, particularly for polycyclic aromatic hydrocarbons with substituted CF₃ groups that, in the absence of other functional groups that can form stronger interactions, C-F H-C interactions may serve to align molecules and give a different crystal packing from that in the pure hydrocarbon (where fluorine is replaced by hydrogen). Thus, C-F H-X (X = C, N, O) interactions are very weak, much weaker than C=O H-X interactions, but they cannot be ignored in predictions of modes of molecular packing in complexes and in crystals.     

Crystal structure of 1H+,10H+-1,10-diazonia-18-crown-6 diethyldithiophosphate

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.     

Hydrogen-bonded complexes involving HF and HCl: the effects of electron correlation and anharmonicity

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.     

Study on the thermokinetic properties of bacterial growth

The power-time curves of bacterial growth at different temperatures were determined by using the 2277 Thermal Activity Monitor (Sweden). From these curves, the growth rate constant () and activation energy (E _a) were calculated. According to the transition state theory of reaction dynamics, the activation entropy (S), activation Gibbs free energy (G) and equilibrium constant (K ) of the activation state could be calculated. These results permitted thermodynamic analysis of the bacterial growth metabolism.Supported by the Natural Science Foundation of Shandong Province.     

Complexation between N-allylmorpholinium derivatives and copper(I) halides. Synthesis and crystal structure of π-complex {[C4H8ONH(C3H5)]+}2[Cu2Cl4]2?

Copper(I) -complex {[C₄H₈ONH(C₃H₅)]⁺}₂[Cu₂Cl₄]^2– (I) was obtained by ac electrochemical synthesis from N-allylmorpholine hydrochloride and copper(II) chloride in ethanol and structurally characterized. In structure I, copper and chlorine atoms form unique noncentrosymmetric Cu₂Cl ₄ ^2– fragments. Both crystallographically independent N-allylmorpholinium cations are involved in the -interaction and are coordinated by the copper atom through the C=C bond of the allyl group. The trigonal pyramidal environment of the Cu(1) atom is composed of three chlorine atoms and the C=C bond, while the Cu(2) atom coordinates two chlorine atoms and the C=C bond forming a planar triangle. The extremely strong N-CCl hydrogen bond (HCl 2.2 ) prevents the Cl(1) atom from acting as a bridge and favors the formation of fragments Cu₂Cl ₄ ^2– .__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 306–310.Original Russian Text Copyright © 2005 by Goreshnik, Davydov, Myskiv.     

Intramolecular hydrogen bond in substituted 3-hydroxypyridines

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.     

Aminomethylene derivatives of azoles

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.     

Molecular and Supramolecular Structures of a Nickel(II)–Copper(II)–Nickel(II) Trinuclear Complex Containing a New Macrocyclic Oxamido Complex Ligand

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.     

Crystal and molecular structure analysis of flutamide. Bifurcated helicoidal C-H ⋯ O hydrogen bonds

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.     

Synthesis and X-ray structural analysis of a unique Co-crystallization complex of [NaSal]2DB24C8 and [KSal]2DB24C8

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)°, ų,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).     

The synthesis and crystal structure of a cubane-like tungsten copper sulphur cluster, [W4CuS4 2P(OEt)2 3(I)(μ2-PhCO2)(MeCN)]

Summary The title compound [W₃C₃S₄{S₂P(OEt)₂}₃(I)(₂ ^–PhCO₂)(MeCN)] crystallized in triclinic system with space group P1 and cell dimensiona=11.645(6),b=18.565(2),c=11.292(7)Å, =96.15(3)°, =113.65(3)°, =93.77(3)°, V=2207.6ų, Z=2, Mr=1588.09, D_c=2.39 g cm^–3. MoK radiation, =0.71073 Å, =97.3 cm^–1, F(000)=1488, R=0.042 for 5588 observed unique reflections I3(I). There are some distortions in the cubane-like W₃CuS₄ core, with three W-W bonds and three weak W-Cu bonds. Two W atoms are coordinated by PhCO₂ bridge ligand, the other W atom is coordinated to the N atom of MeCN.     

Catalytic and physico-chemical properties of Al2O3?H3PO4 system, II. Donor-acceptor properties

Donor-acceptor properties of catalysts containing different quantities of orthophosphoric acid on -alumina were studied. The decrease in N₂O decomposition rate was found to be parallel with that of one-electron donor sites. Catalysts containing more than 0.4 mmol H₃PO₄/g Al₂O₃ exhibit individual surface properties due to the formation of an aluminium phosphate phase in the surface layer.

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- , -Al₂O₃. , N₂O . , 0,4 H₃PO₄/ Al₂O₃ .