Infrared and Raman spectra of 3,5-diamino-6-(o-C6H4X)-1,2,4-triazines [X = F,Cl, Br,CH3

Raman and infrared spectra of four substituted 3,5-diamino-6-(ortho-substituted phenyl)-1,2,4-triazines, having ortho-fluoro, -chloro, -bromo and -methyl groups on the phenyl ring, are reported and discussed. Bands due to substituent sensitive phenyl vibrations are observed in both the Raman and infrared spectra. The Raman spectra of all four compounds have strong bands near 770 and 1330 cm(-1) which are assigned to the ring breathing vibration of the 1,2,4-triazine ring and an asymmetric triazine C-NH2 stretching vibration, respectively. A medium/strong band near 800 cm(-1) in the infrared spectra is attributed to an out-of-plane bending vibration of the substituted 1,2,4-triazine ring.     

Electronic structure of phenyl-N,N-dimorpholinomethanes

The electronic structure of dimorpholinomethane and 11 phenyl derivatives was studied by He 1 photoelectron spectroscopy and AM1 quantum chemical calculations. The π-system of the phenyl ring reacts weakly with the molecular orbitals of dimorpholinomethane. Mutual electronic effects of the dimorpholine and phenyl fragments are estimated. It is shown that for most title compounds, HOMO is localized on the nitrogen atoms of dimorpholinomethane and is independent of the type of substituent in the phenyl ring. An exception is dimethylaminopheny I-N,N-dimorpholinomethane, whose first ionization potential (7.31_eV) is much lower than that for other compounds (8.15-8.53_eV) due to electron withdrawal from the 3π(b₁) MO of the phenyl ring. The relationship between the first ionization potentials and the effective corrosion inhibiting property of the compounds is discussed. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 753-764, July-August, 2000     

Electronic structure of phenyl-N,N-dimorpholinomethanes

The electronic structure of dimorpholinomethane and 11 phenyl derivatives was studied by He 1 photoelectron spectroscopy and AM1 quantum chemical calculations. The π-system of the phenyl ring reacts weakly with the molecular orbitals of dimorpholinomethane. Mutual electronic effects of the dimorpholine and phenyl fragments are estimated. It is shown that for most title compounds, HOMO is localized on the nitrogen atoms of dimorpholinomethane and is independent of the type of substituent in the phenyl ring. An exception is dimethylaminopheny I-N,N-dimorpholinomethane, whose first ionization potential (7.31_eV) is much lower than that for other compounds (8.15-8.53_eV) due to electron withdrawal from the 3π(b₁) MO of the phenyl ring. The relationship between the first ionization potentials and the effective corrosion inhibiting property of the compounds is discussed. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 753-764, July-August, 2000     

Pyramidalization at the sp2-Hybridized ipso-Carbon Atom of Phenyl Compounds

In this study we investigate the pyramidalization of the sp²-hybridized center at the ipso-carbon atom C_i of phenyl compounds on the theoretical side by DFT calculations of toluene, t-butylbenzene, and ethylbenzene and on the experimental side by a scatter plot analysis of 14,169 structures of ethylbenzene compounds C_β−C_αH₂−C₆H₅ with three open positions for variation at C_β, accumulated in the Cambridge Structural Database. In a 360° rotation about the bond between C_α of the substituent and the ipso-carbon atom C_i of the phenyl ring, the pyramidalization performs three maxima and minima. A comparison of structures with pyramidalization and its hypothetical counterparts without pyramidalization shows that pyramidalization is associated with a gain of energy. The data reveal that it is the carbon atom C_α of the phenyl substituent, which on pyramidalization bends away from the phenyl plane. Pyramidalization of sp²-hybridized centers is an omnipresent member in molecular weak interactions.     

Quantum-Chemical Study of the Structure of Cyanophosphines and Their Oxides

The structure of cyanophosphines and their oxides was studied by ab initio (RHF/6-31G^**) and semiempirical (PM3) methods. Both methods predict that MeOP(CN)₂, (MeO)₂PCN, and (MeO)₂P(O)CN exist in noneclipsed antiperiplanar and synclinal conformations. The calculation results nicely agree with measured dipole moments and Kerr constants of these compounds. The phenyl and diphenyl derivatives PhP(CN)₂, Ph₂PCN, Ph(Et)PCN, and Ph₂P(O)CN prefer forms in which the phenyl ring plane is eclipsing the phosphorus lone electron pair or the phosphoryl bond. The interactions of the phosphorus lone electron pair with the phenyl ring and with the cyano group are lacking in the title compounds.     

Inorganic-organic hybrid compounds based on face-sharing octahedral [PbI3]∞ chains: self-assemblies, crystal structures, and ferroelectric, photoluminescence properties

Eight inorganic-organic hybrid compounds with a formula of [R-Bz-1-APy][PbI(3)] (R-Bz-1-APy(+) = mono-substituted benzylidene-1-aminopyridinium Schiff base derivative; R = m-CN (1), m-CH(3) (2), H (3), p-F (4), p-Cl (5), p-Br (6), o-Cl (7), o-Br (8)) have been synthesized and characterized structurally. The common characteristic of the crystal structures of 1-8 is that the inorganic components form straight and face-sharing octahedral [PbI(3)](∞) chains and the Schiff base cations surround the [PbI(3)](∞) chains to form molecular stacks. The substituent (R) on the phenyl ring of the Schiff base cation clearly influences the packing structures of 1-8, and the hybrid compound crystallizes in the space group P6(3) when R = CN (1) in the meta-position of the phenyl ring, and in a central symmetric space group when R is in the ortho- or para-position of the phenyl ring. The conformation of the Schiff base cation is related to the R position, and the dihedral angle between the phenyl and pyridyl rings increases in the order of para- < meta- < ortho-position substitution of the phenyl ring. The long molecular axis of the Schiff base cation adopts a manner approximately parallel to the straight inorganic [PbI(3)](∞) chain in the para-substituted hybrid compounds, and perpendicular to the straight inorganic [PbI(3)](∞) chain in the ortho-substituted hybrid compounds. 1 is second harmonic generation (SHG) active with a comparable response as that of urea and also exhibits ferroelectricity with larger P(s) and P(r) values; 1-8 emit multi-band luminescence in the 300-650 nm regions under the excitation of ultraviolet light.     

DFT study of 1-, 4-, and 5-substituted 2-oxo-1,2,3,4-tetrahydropyrimidines: substituent steric and electronic effects,and ring flipping

Steric and the electronic effects caused by the substituents in the 1-, 4-, and 5-positions of substituted 2-oxo-1,2,3,4-tetrahydropyrimidines were investigated using density functional theory at the B3LYP/6-31++G(d,p) level. Results of this study show that the heterocyclic ring adopts a pseudo-boat conformation, in which the C₄ and N₁ atoms are deviated from ring planarity. The C₄-substituent occupies a pseudo-axial position and the space orientation of the substituent depends on the type and position of the additional substituent in this aryl group. The heights of the C₄ and N₁ atoms from the boat plane and the orientation of 5-CO moiety toward the heterocyclic ring depend on the electronic and steric effects of the substituents in the various positions. Ring flip calculations for 4-phenyl substituent explain the extreme steric effect caused by the substituent in the 1-position. These calculations indicate the more favored pseudo-axial orientation of the phenyl group over the equatorial orientation.     

Hydrogen‐bonding and C—H⋯π interactions in ethyl 4‐acetyl‐5‐methyl‐3‐phenyl‐1H‐pyrrole‐2‐carboxylate monohydrate

In the title compound, C₁₆H₁₇NO₃·H₂O, the pyrrole ring is distorted slightly from ideal C_2v symmetry. Three strong hydrogen bonds link the substituted pyrrole and water mol­ecules to form infinite chains, in which the hydrogen bonds form rings and chain patterns. Two intermolecular C—H?π interactions maintain the internal cohesion between these chains. The molecular structure differs slightly from that of the isolated mol­ecule calculated by ab initio quantum‐mechanical calculations. In the latter model, the non‐H substituent atoms share the plane of the pyrrole ring, except for the phenyl group, which lies almost perpendicular to this plane.     

5‐Acetyl‐2‐amino‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile and 2‐amino‐5‐benzoyl‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile acetonitrile solvate

The syntheses, X‐ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C₁₅H₁₄N₂O₂, (II), and C₂₀H₁₆N₂O₂·C₂H₃N, (III), respectively. In both mol­ecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo‐axial phenyl substituent and the flat part of the pyran ring are 92.7 (1) and 93.2 (1)° in (II) and (III), respectively. In the crystal structure of (II), inter­molecular N—H⋯N and N—H⋯O hydrogen bonds link the mol­ecules into a sheet along the (103) plane, while in (III), they link the mol­ecules into ribbons along the a axis.     

Conformational studies on heteroleptic trifluoromethyl‐substituted phenylboranes

Organoboranes carrying electron‐withdrawing substituents are commonly used as Lewis acidic catalysts or cocatalysts in a variety of organic processes. These Lewis acids also became popular through their application in `frustrated Lewis pairs', i.e. combinations of Lewis acids and bases that are unable to fully neutralize each other due to steric or electronic effects. We have determined the crystal and molecular structures of four heteroleptic arylboranes carrying 2‐(trifluoromethyl)phenyl, 2,6‐bis(trifluoromethyl)phenyl, 3,5‐bis(trifluoromethyl)phenyl or mesityl substituents. [3,5‐Bis(trifluoromethyl)phenyl]bis[2‐(trifluoromethyl)phenyl]borane, C₂₂H₁₁BF₁₂, (I), crystallizes with two molecules in the asymmetric unit which show very similar geometric parameters. In one of the two molecules, both trifluoromethyl groups of the 3,5‐bis(trifluoromethyl)phenyl substituent are disordered over two positions. In [3,5‐bis(trifluoromethyl)phenyl]bis[2,6‐bis(trifluoromethyl)phenyl]borane, C₂₄H₉BF₁₈, (II), only one of the two meta‐trifluoromethyl groups is disordered. In [2,6‐bis(trifluoromethyl)phenyl]bis[3,5‐bis(trifluoromethyl)phenyl]borane, C₂₄H₉BF₁₈, (III), both meta‐trifluoromethyl groups of only one 3,5‐bis(trifluoromethyl)phenyl ring are disordered. [3,5‐Bis(trifluoromethyl)phenyl]dimesitylborane, C₂₆H₂₅BF₆, (IV), carries only one meta‐trifluoromethyl‐substituted phenyl ring, with one of the two trifluoromethyl groups disordered over two positions. In addition to compounds (I)–(IV), the structure of bis[2,6‐bis(trifluoromethyl)phenyl]fluoroborane, C₁₆H₆BF₁₃, (V), is presented. None of the ortho‐trifluoromethyl groups is disordered in any of the five compounds. In all the structures, the boron centre is in a trigonal planar coordination. Nevertheless, the bond angles around this atom vary according to the bulkiness and mutual repulsion of the substituents of the phenyl rings. Also, the ortho‐trifluoromethyl‐substituted phenyl rings usually show longer B—C bonds and tend to be tilted out of the BC₃ plane by a higher degree than the phenyl rings carrying ortho H atoms. A comparison with related structures corroborates the conclusions regarding the geometric parameters of the boron centre drawn from the five structures in this paper. On the other hand, CF₃ groups in meta positions do not seem to have a marked effect on the geometry involving the boron centre. Furthermore, it has been observed for the structures reported here and those reported previously that for CF₃ groups in ortho positions of the aromatic ring, disorder of the F atoms is less probable than for CF₃ groups in meta or para positions of the ring.     

()‐9‐(2‐Bromophenyl)‐7,7‐dimethyl‐1,3,4,5,6,7,8,9‐octahydrofuro[3,4‐b]quinoline‐1,8‐dione

The title compound, C₁₉H₁₈BrNO₃, has potential calcium modulatory properties. The 1,4‐di­hydro­pyridine ring has a very shallow boat conformation and is one of the most planar examples of this moiety. The 2‐bromo­phenyl substituent is in the axial synperiplanar orientation. The quinoline ring has a half‐chair conformation, with the unusual arrangement of the out‐of‐plane atom being on the opposite side of the ring plane to the bromo­phenyl substituent. The mol­ecules are linked into chains by intermolecular hydrogen bonds.     

3‐(2‐Furyl)‐6‐(4‐methyl­phenyl)‐7H‐1,2,4‐triazolo­[3,4‐b][1,3,4]thia­diazine and its 6‐phenyl analogue

In the title compounds, C₁₅H₁₂N₄OS, (I), and C₁₄H₁₀N₄OS, (II), the thia­diazine ring adopts a skew‐boat conformation, while the triazole and furyl rings are essentially planar. The phenyl group is twisted by 33.5 (2) and 47.9 (1)° out of the triazole‐ring plane in (I) and (II), respectively.     

Ethyl β‐{2‐[4‐(dimethylamino)phenyliminomethyl]‐1‐(phenylsulfonyl)indol‐3‐yl}acrylate

The title compound, C₂₈H₂₇N₃O₄S, crystallizes in the centrosymmetric space group P2₁/n, with one mol­ecule in the asymmetric unit. In the indole ring, the dihedral angle between the fused rings is 3.6 (1)°. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 79.2 (1)° with the best plane of the indole moiety. The phenyl ring of the di­methyl­amino­phenyl group is orthogonal to the phenyl ring of the phenyl­sulfonyl group. The dihedral angle formed by the weighted least‐squares planes through the pyrrole ring and the phenyl ring of the di­methyl­amino­phenyl group is 7.8 (1)°. The molecular structure is stabilized by C—H?O and C—H?N interactions.     

Theoretical studies of thermal decomposition of anhydrous cadmium and silver oxalates

The results of first principles calculations of band structure, density of states and electron density topology of CdC₂O₄ and Ag₂C₂O₄ crystals are presented. The calculations have been performed with WIEN2k ab initio program, using highly precise full potential linearized augmented plane wave (FP LAPW) method within Density Functional Theory formalism. The obtained SCF electron density has been used in calculations of Bader’s AIM (atoms in molecules) topological properties of the electron density in crystal. The obtained results show important similarities in electronic structure and electron density topology of both compounds and allow supposing, that during the thermal decomposition process these compounds should behave similarly, which is in agreement with the experiment.     

New five‐ring symmetrical bent‐core mesogens exhibiting the fascinating B7 phase

Three new homologous series of symmetrical five‐ring bent‐core compounds have been synthesized and investigated for their mesomorphic properties. The laterally unsubstituted parent compounds exhibit a metastable SmCP_A phase. However, the two series of compounds containing a strongly polar cyano or nitro group at the angular position of the central phenyl unit show the fascinating classical B₇ phase. The mesophases have been characterized using standard techniques.     

Linear free energy relationship in thin layer chromatography of 5-arylidenebarbiturates

Summary Among 33 investigated 5-arylidenebarbiturates (I) and their N,N-dimethyl analogs (II) containing different substituents in the phenyl ring, 14 are new derivatives. Substituent effects of the phenyl ring on the ability of adsorption on silica gel were observed by TLC. The significant correlations between the R_M values and or ⁺ substient constants were found for both ortho-substituted derivatives of series I and N,N-di-methyl derivatives of series II. The mechanism of adsorption on the silica gel in relationships to our previous studies on barbituric acid derivatives is discussed.Part of this work has been presented at the Budapest Chromatography Conference, June 1–3, 1983.     

(±)‐Methyl and (±)‐ethyl 4‐(2,3‐di­fluoro­phen­yl)‐2,6,6‐trimethyl‐5‐oxo‐1,4,5,6,7,8‐hexa­hydro­quinoline‐3‐carboxyl­ate

The title compounds, C₂₀H₂₁F₂NO₃ and C₂₁H₂₃F₂NO₃, respectively, belong to a class of 1,4‐dihydro­pyridines whose members sometimes display calcium modulatory properties. The 1,4‐dihydro­pyridine rings have the usual shallow boat conformation. In each structure, the 2,3‐difluoro­phenyl ring is oriented such that the fluoro substituents are in a synperi­planar orientation with respect to the 1,4‐dihydro­pyridine ring plane and the oxocyclo­hexene ring has a slightly distorted envelope conformation. Both structures exhibit the same inter­molecular N—H⋯O hydrogen‐bonding motif, in which the mol­ecules are linked into chains by inter­actions involving the carbonyl O atom of the oxocyclo­hexene ring.     

4,6‐Dimethyl‐2‐[(4‐phenylpiperidin‐1‐yl)methyl]isothiazolo[5,4‐b]pyridin‐3(2H)‐one and 4,6‐dimethyl‐2‐[(4‐phenyl‐1,2,3,6‐tetrahydropyridin‐1‐yl)methyl]isothiazolo[5,4‐b]pyridin‐3(2H)‐one

In the crystal structures of the title compounds, C₂₀H₂₃N₃OS, (II), and C₂₀H₂₁N₃OS, (III), significant differences occur in the conformation of, respectively, the phenylpiperidine and phenyltetrahydropyridine substituents at the 2‐position of the isothiazolopyridine system. The piperidine ring adopts a chair conformation, while the tetrahydropyridine ring assumes a half‐chair form. The phenylpiperidine and phenyltetrahydropyridine fragments exhibit different conformations resulting from the steric and conjugation effects in the phenyl ring, respectively. Theoretical calculations show that both conformations are energetically stable and correspond to a minimum of energy for the analyzed systems. The molecular packing in (II) is influenced by π–π interactions of the isothiazolopyridine systems, with a shortest centroid‐to‐centroid separation of 3.5843 (11) Å between pyridine rings. In the crystal structure of (III), the molecules are linked by C—H...O hydrogen bonds and C—H...π interactions.     

Evaluation of chiral oxazolines for the highly enantioselective diethylzinc addition to N-(diphenylphosphinoyl) imines

On the basis of the principle that the incorporation of the structurally rigid and conformationally restricted skeleton in beta-amino alcohols is beneficial to the enantioselective diethylzinc addition to imines, a series of chiral oxazolines, which had been designed and conveniently prepared from commercially available (1S,2S)-2-amino-1-phenylpropane-1,3-diol, were applied in the diethylzinc addition to diphenylphosphinoyl imines to give high yields of 68-84% and excellent ee values of 90-95%. The configuration of the product was controlled by the chirality of the carbon bonded to the hydroxyl group in the oxazoline. Oxazolines bearing a para- or meta-substituted phenyl group generally offered higher enantioselectivity than those containing an ortho-substituted phenyl. The X-ray structures of 4f and 4j, in combination with the proposed transition state, preliminarily explained why oxazolines with a para- or meta-substituent on the phenyl group gave higher enantioselectivities than those bearing an ortho-substituent. This successful example using chiral oxazolines to promote the titled reaction implies that a large family of chiral compounds containing an oxazoline ring moiety have the potential to be developed for promoting the highly enantioselective dialkylzinc addition to N-(diphenylphosphinoyl) imines.     

Hydroarylation of cinnamic acid with phenols catalyzed by acidic ionic liquid [H-NMP]HSO<Subscript>4</Subscript>: computational assessment on substituent effect

Hydroarylation of cinnamic acid with different substituted phenols, in the presence of acidic ionic liquid, N-methyl-2-pyrrolidonum hydrosulfate ([H-NMP]HSO₄) gave the corresponding dihydrocoumarins in high yields and excellent selectivity. Among these substituted phenols, while methyl phenol afforded the corresponding dihydrocoumarin, nitrophenol under the same reaction conditions diverted the course of reaction, affording 3-(4-nitrophenyl)-3-phenylpropanoic acids. We investigated this behavior from the energetic and electronic points of view, using quantum chemistry computational methods. In this respect, the electronic energy change values for the conversion reaction of substituted phenyl cinnamate esters to dihydrocoumarin compounds have been obtained via density functional theory calculations. We demonstrated that the conversion reaction in the presence of CH₃ substituent is more favorable energetically than NO₂ substituent. Moreover, we have concentrated on topological analysis of electron density on some key bond and ring critical points and their associated bond paths to assess the conversion of substituted phenyl cinnamate esters to dihydrocoumarins. Our calculated results showed that para-methyl phenyl cinnamate has more of electronic tendency to undergo the intramolecular cyclization step and, consequently, generate the corresponding dihydrocoumarin.