Benzene Plane Research Articles

2-(5-Methyl-1,3,4-oxadiazol-2-yl)phenyl acetate

In the title compound, C11H10N2O3, which is a potential bioactive compound, the benzene and oxa­diazole rings are approximately coplanar, with an inter-ring dihedral angle of 4.14 (2)°, while the ester plane is rotated out of the benzene plane [dihedral angle = 82.69 (9)°]. In the crystal, the mol­ecules form layers down the a axis with weak π–π inter­actions between the oxa­diazole and benzene rings [minimum ring centroid separation = 3.7706 (14) Å].

Carbinoxaminium dipicrate.

In the dication of the title salt, C16H21ClN2O2+·2C6H2N3O7 − [systematic name: 2-{(4-chloro­phen­yl)[2-(di­methyl­aza­nium­yl)eth­oxy]meth­yl}pyridinium bis­(2,4,6-tri­nitro­phenolate), contains a carbinoxaminium dication and two picrate anions, which are held together through inter­molecular N—H⋯O hydrogen bonds. In the dication, the two aromatic rings form a dihedral angle of 80.1 (1)°. In the two independent picrate anions, the nitro groups are twisted from the benzene plane, the largest dihedral angle in each ion being 42.8 (1) and 81.1 (5)°. In the crystal, in addition to the classical N—H⋯O hydrogen bonds, weak C—H⋯O hydrogen bonds and π–π inter­actions between the aromatic rings of the anions [centroid–centroid distances of 3.5768 (15) and 3.7436 (15) Å] help to establish the packing.

Dicopper(II) Metallacyclophanes with Oligo(p-phenylene-ethynylene) Spacers: Experimental Foundations and Theoretical Predictions on Potential Molecular Magnetic Wires

Two novel double-stranded dicopper(II) metallacyclophanes of formula (nBu4N)4[Cu2(dpeba)2]·4MeOH·2Et2O (1) and (nBu4N)4[Cu2(tpeba)2]·12H2O (2) have been prepared by the Cu(II)-mediated self-assembly of the rigid ('rod-like') bridging ligands N,N'-4,4'-diphenylethynebis(oxamate) (dpeba) and N,N'-1,4-di(4-phenylethynyl)phenylenebis(oxamate) (tpeba), respectively. Single crystal X-ray diffraction analysis of 1 confirms the presence of a dicopper(II)tetraaza[3.3]4,4'-diphenylethynophane metallacyclic structure featuring a very long intermetallic distance between the two square planar Cu(II) ions [r = 14.95(1) Å]. The overall parallel-displaced π-stacked conformation of the two nearly planar para substituted diphenylethyne spacers [dihedral angle (ψ) of 7.8(1)°] leads to important deviations from the perpendicular orientation of the copper mean basal planes with respect to the facing benzene planes [dihedral angles (φ) of 56.4(1) and 58.4(1)°]. X-band EPR spectra together with variable-temperature magnetic susceptibility and variable-field magnetization measurements of 1 and 2, both in solution and in the solid state, show the occurrence of a non-negligible, moderate to weak intramolecular antiferromagnetic coupling [-J = 3.9-4.1 (1) and 0.5-0.9 cm(-1) (2); H = -JS1·S2 with S1 = S2 = SCu = 1/2]. Density functional calculations on the BS singlet (S = 0) and triplet (S = 1) spin states of the model complexes 1 and 2 with an ideal orthogonal molecular geometry (ψ = 0° and φ = 90°) support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the dxy orbital of each square planar Cu(II) ion through the predominantly π-type orbital pathway of the double p-diphenylethyne (1) and di(phenylethynyl)phenylene spacers (2). Time-dependent density functional calculations reproduce the observed bathochromic shift of the main intraligand (IL) π-π* transition in the electronic absorption spectra of 1 and 2 [λ1 = 308 (1) and 316 nm (2)]. In the series of orthogonal model complexes 1-5 with linear oligo(p-phenylene-ethynylene) (OPE) spacers, -C6H4(C≡CC6H4)n- (n = 1-5), a linear increase of the IL π-π* transition energy with the reciprocal of the intermetallic distance is theoretically predicted [νmax = 1.99 × 10(4) + 2.15 × 10(5) (1/r) (S = 0) or ν = 2.01 × 10(4) + 2.18 × 10(5) (1/r) (S = 1)], which clearly indicates that the effective π-conjugation length increases with the number of phenylethyne repeating units. This is accompanied by an exponential decay of the antiferromagnetic coupling with the intermetallic distance [-J = 1.08 × 10(3) exp(-0.31r)], which supports the ability of the extended π-conjugated OPEs to mediate the exchange interaction between the unpaired electrons of the two Cu(II) centers with intermetallic distances in the range of 1.5-4.3 nm. Further developments may be then envisaged for this new family of oxamato-based dicopper(II) oligo-p-phenylethynophanes on the basis of the unique ligand capacity to act as a molecular antiferromagnetic wire.

Sub-Doppler Electronic Spectra of Benzene–(H2)nComplexes

Excitation spectra of the benzene-(H2)n (n = 1-3) van der Waals (vdW) complexes in the vicinity of the S1 ← S0 60(1) vibronic transition of the monomer were recorded with sub-Doppler resolution by utilizing mass-selective two-color resonance-enhanced two-photon ionization. Two distinguished isomers, correlating to para- and ortho-H2, are identified for n = 1 and 2. This finding is the manifestation of the internal rotation of the H2 unit(s) located above (and below) the benzene molecular plane within the complexes. For the observation of the weaker binding para species, a gas sample of pure para-H2 was used. Rotationally resolved spectra allowed us to fix the cluster geometry unambiguously. Three vibronic bands involving vdW-mode excitation were observed for the ortho species with n = 1, yielding to probable sets of vibrational frequencies of all the three vdW modes. One of them correlates to the splitting between the m = 0 and ±1 sublevels in the j = 1 state of a freely rotating H2 molecule, and the potential barrier for the hindered internal rotation has been evaluated from the values. Rotationally resolved spectrum of benzene-(ortho-H2)3 is consistent with a (2 + 1) binding motif, where two H2 molecules on one side of the benzene plane seem to scramble their positions and roles. All the complexes examined with rotational resolution exhibited homogeneous line broadening, which corresponds to the upper-state lifetimes in the subnanosecond regime, most probably due to vibrational predissociation in the S1 6(1) manifold.

Role of Wingtip Substituents on Benzene-Platform-Based Tetrapodal Ligands toward the Formation of a Self-Assembled Silver Carbene Cage

Tetrapodal imidazolium ligands L(1)-L(3) as their PF6(-) salts are synthesized in good yields by reacting 1,2,4,5-tetrakis(bromomethyl)benzene with N-methylimidazole, N-benzylimidazole, and N-ethylimidazole, respectively. Single-crystal X-ray diffraction studies of L(1)·4PF6, L(2)·4PF6, and L(3)·4PF6 show the chair conformation of the tetrapodal imidazoliums (L(1)-L(3)), where 1,5- and 2,4-imidazolium moieties are oriented in opposite directions of the benzene plane. The PF6(-) salts of L(1)-L(3) are reacted with Ag2O to synthesize different silver complexes of N-heterocyclic carbene (NHC), 1-3, respectively, in good yields. Crystals of all three complexes suitable for single-crystal X-ray diffraction study are also isolated. Structural analysis of 1, i.e., the complex of L(1)·4PF6 containing methyl as a wingtip substituent, and Ag2O shows the formation of a bimetallic silver NHC (NHC-Ag) complex, [(L(1)-4H)·2Ag]·2PF6, which is rotationally disordered over an inversion of symmetry of the space group P2(1)/c. Elemental analysis and solution-state (1)H and (13)C NMR studies confirm the above molecular formula of complex 1. When L(2)·4PF6 functionalized with the benzyl wingtip moiety is explored for similar complexation with Ag2O, the isolated complex 2 shows the formation of a simple NHC-Ag complex with molecular formula [(L(2)-4H)·2Ag]·2PF6, as observed in the case of 1. Interestingly, the reaction of L(3)·4PF6 containing ethyl as the wingtip substituent and Ag2O shows the formation of a silver-ion-assisted tetranuclear molecular box of [Ag4(L(3)-4H)2](4+) (3).

Adsorption on Edge-Functionalized Bilayer Graphene Nanoribbons: Assessing the Role of Functional Groups in Methane Uptake

A combination of ab initio and classical Monte Carlo simulations is used to investigate the effects of functional groups on methane binding. Using Møller–Plesset (MP2) calculations, we obtain the binding energies for benzene functionalized with NH2, OH, CH3, COOH, and H2PO3 and identify the methane binding sites. In all cases, the preferred binding sites are located above the benzene plane in the vicinity of the benzene carbon atom attached to the functional group. Functional groups enhance methane binding relative to benzene (−6.39 kJ/mol), with the largest enhancement observed for H2PO3 (−8.37 kJ/mol) followed by COOH and CH3 (−7.77 kJ/mol). Adsorption isotherms are obtained for edge-functionalized bilayer graphene nanoribbons using grand canonical Monte Carlo simulations with a five-site methane model. Adsorbed excess and heats of adsorption for pressures up to 40 bar and 298 K are obtained with functional group concentrations ranging from 3.125 to 6.25 mol % for graphene edges functionalized with OH, NH2, and COOH. The functional groups are found to act as preferred adsorption sites, and in the case of COOH the local methane density in the vicinity of the functional group is found to exceed that of bare graphene. The largest enhancement of 44.5% in the methane excess adsorbed is observed for COOH-functionalized nanoribbons when compared to H terminated ribbons. The corresponding enhancements for OH- and NH2-functionalized ribbons are 10.5% and 3.7%, respectively. The excess adsorption across functional groups reflects the trends observed in the binding energies from MP2 calculations. Our study reveals that specific site functionalization can have a significant effect on the local adsorption characteristics and can be used as a design strategy to tailor materials with enhanced methane storage capacity.

X-ray Diffraction Structures of Regioisomers of N-Methylated Benzimidazole Compounds with Interest for the Design of Amyloid-Avid Probes

This work describes the compounds 5-bromo-1-methyl-2-[N-methyl-N-(2′-O-tert-butylcarbonatethyl)-4′-aminophenyl]-1H-benzo[d]imidazole (4) and 6-bromo-1-methyl-2-[N-methyl-N-(2′-O-tert-butylcarbonatethyl)-4′-aminophenyl]-1H-benzo[d]imidazole (5), C22H26BrN3O3, which correspond to two regioisomers that were obtained by N-methylation of the corresponding 6-bromobenzimidazole derivative. The structures of these two regioisomers have been confirmed in solution by NMR NOESY experiments, as well as in the solid state using single crystal X-ray diffraction analysis. The structures of 4 and 5 comprise two planar benzimidazole and benzene fragments and a disordered aliphatic chain containing a terminal carbamate group. Compound 4 crystallized in the monoclinic P21/c group with unit cell parameters a = 23.0178(7) A, b = 7.9106(2) A, c = 11.9758(3) A, β = 93.340(2)o, V = 2176.90(10) A3, Z = 4, D = 1.405 Mg/m3. Compound 5 crystallized in the triclinic P-1 group with unit cell parameters a = 6.7187(3) A, b = 16.5203(10) A, c = 21.3544(13) A, α = 109.279(2)o, β = 94.802(2)o, γ = 98.871(2)o, V = 2187.4(2) A3, Z = 4, D = 1.398 Mg/m3. Two regiosomers of benzimidazole derivatives are reported, including the elucidation of their structures in solution by NMR NOESY experiments and in the solid state by X-ray diffraction studies.

Rapid capture of large amplitude motions in 2,6-difluorophenol: High-resolution fast-passage FT-MW technique

The rotational supersonic-jet Fourier transform microwave (FT-MW) spectra of the aromatic 2,6-difluorophenol (DFP) have been recorded and analyzed in the frequency range of 8–26GHz. A new design of broadband FT-MW spectroscopy with in-phase/quadrature-phase-modulation passage-acquired-coherence technique (IMPACT) has been used to obtain the spectra rapidly at high-resolution, obsoleting subsequent measurements with a resonator spectrometer.The structural analysis shows that the H-atom of the hydroxyl-group is located in the benzene plane forming an intramolecular hydrogen bond with one of the F-atoms. Due to the tunneling motion of this H-atom between two the equivalent positions, a large part of the rotational transitions are split into two signals being separated by ∼17MHz.The rotational constants, centrifugal distortion constants and the Coriolis coupling constant have been determined.

3-(5-Oxo-3-phenyl-4,5-dihydro-1H-pyrazol-1-yl)benzonitrile

In the title compound, C16H11N3O, the dihedral angles between the 3-cyano­benzene and benzene planes and the 1H-pyrazol-5(4H)-one plane are 4.97 (9) and 9.91 (9)°, respectively.

Cyclic imides and an open-chain amide carboxylic acid from the facile reaction ofcis-cyclohexane-1,2-carboxylic anhydride with the isomeric monofluoroanilines

The structures of the cyclic imides cis-2-(2-fluorophenyl)-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, C(14)H(14)FNO(2), (I), and cis-2-(4-fluorophenyl)-3a,4,5,6,7,7a-hexahydroisoindoline-1,3-dione, C(14)H(14)FNO(2), (III), and the open-chain amide acid rac-cis-2-[(3-fluorophenyl)carbamoyl]cyclohexane-1-carboxylic acid, C(14)H(16)FNO(3), (II), are reported. Cyclic imides (I) and (III) are conformationally similar, with comparable ring rotations about the imide N-C(ar) bond [the dihedral angles between the benzene ring and the five-membered isoindole ring are 55.40 (8)° for (I) and 51.83 (7)° for (III)]. There are no formal intermolecular hydrogen bonds involved in the crystal packing of either (I) or (III). With the acid (II), in which the meta-related F-atom substituent is rotationally disordered (0.784:0.216), the amide group lies slightly out of the benzene plane [the interplanar dihedral angle is 39.7 (1)°]. Intermolecular amide-carboxyl N-H···O hydrogen-bonding interactions between centrosymmetrically related molecules form stacks extending down b, and these are linked across c by carboxyl-amide O-H···O hydrogen bonds, giving two-dimensional layered structures which lie in the (011) plane. The structures reported here represent examples of compounds analogous to the phthalimides or phthalanilic acids and have little precedence in the crystallographic literature.

Bis(benzylaminium) 4,5-dichlorobenzene-1,2-dicarboxylate monohydrate

In the structure of the title salt, 2C7H10N+·C8H2Cl2O4 2−·H2O, the two benzyl­aminium anions have different conformations, one being essentially planar and the other having the side chain rotated out of the benzene plane [minimum ring to side-chain C—C—C—N torsion angles = −3.6 (6) and 50.1 (5)°, respectively]. In the 4,5-dichloro­phthalate dianion, the carboxyl­ate groups make dihedral angles of 23.0 (2) and 76.5 (2)° with the benzene ring. In the crystal, aminium N—H⋯O and water O—H⋯O hydrogen-bonding associations with carboxyl­ate O-atom acceptors give a two-dimensional duplex sheet structure which extends along the (011) plane. Weak π–π inter­actions are also present between the benzene ring of the dianion and one of the cation rings [minimum ring centroid separation = 2.749 (3) Å].

2-({4-[4-(1H-Benzimidazol-2-yl)phenyl]-1H-1,2,3-triazol-1-yl}methoxy)ethanol

In the title molecule, C18H17N5O2, the dihedral angle between the benzene plane and the benzimidazole plane is 19.8 (1)° and the angle between the benzene plane and the triazole plane is 16.7 (1)°. In the crystal, mol­ecules are connected by O—H⋯N hydrogen bonds, forming zigzag chains along the c-axis direction. The chains are connected by bifurcated N—H⋯(N,N) hydrogen bonds into layers parallel to (100). These layers are connected along the a-axis direction by weak C—H⋯O contacts, forming a three-dimensional network.

2-Azido-1-(4-methyl-phen-yl)ethanone.

In the mol­ecule of the title compound, C9H9N3O, the angle formed by the least-squares line through the azide group with the normal to the plane of the benzene plane ring is 46.62 (16)°. The crystal structure features C—H⋯O hydrogen bonds, which link the mol­ecules into zigzag chains running parallel to [010].

5-[4-(1H-Imidazol-1-yl)phenyl]-1H-tetrazole

In the title compound, C10H8N6, the tetra­zole and benzene rings are close to being coplanar [dihedral angle = 9.90 (16)°], but the imidazole ring is rotated 37.18 (09)° out of the benzene plane. In the crystal, mol­ecules are connected through tetra­zole–imidazole N—H⋯N hydrogen bonds, giving rise to zigzag chains, which extend along [010].

Dimethyl 4,5-dichlorobenzene-1,2-dicarboxylate

In the title compound, C10H8Cl2O4, the two Cl atoms and one of the meth­oxy­carbonyl groups are almost coplanar [maxi­mum derivation = 0.035 (2) Å] with the benzene plane, and the other meth­oxy­carbonyl group exhibits an almost orthogonal disposition relative to the benzene plane, with a dihedral angle of 84.82 (3)° between the planes. In the crystal, the molecules are connected into a chain propagating along the [011] direction through nonclassical C—H⋯O hydrogen bonds.

(E)-4-Methoxy-N′-(3,4,5-trimethoxybenzylidene)benzohydrazide

In the asymmetric unit of the title compound, C18H20N2O5, there are two crystallographic independent mol­ecules. Both mol­ecules are twisted; the dihedral angle between the two benzene rings is 7.2 (5)° in one mol­ecule, whereas it is 85.9 (4)° in the other. Of the three meth­oxy groups in the 3,4,5-trimeth­oxy­phenyl unit, two meth­oxy groups at meta positions are approximately coplanar with the benzene plane [C—O—C—C torsion angles of −2.3 (13)–4.8 (11)°], but the other meth­oxy, at the para position, is out of the plane [C—O—C—C of 72.8 (9)° in one mol­ecule and −77.5 (9)° in the other]. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds and weak C—H⋯O inter­actions into tapes along the b axis. C—H⋯π inter­actions are also present.

二苯硫分子自组装单层膜的原子结构 Atomic Structure of Self-Assembled BPT Molecular Monolayer

利用第一性原理研究了二苯硫单分子、一维分子链和分子单层膜的原子结构。CASTEP计算显示二苯硫单分子中两个苯环面的夹角为40度。二苯硫一维分子链由一系列略倾斜的二苯硫分子平行组成，其分子间距为0.37 nm；许多分子链平行错位组成二苯硫分子单层膜，分子链间距为0.66 nm。二苯硫分子单层膜的能量比单分子的能量低了0.146 eV，这说明分子单层膜的结构稳定，这是一个分子自组装过程。 The first-principle technique has been employed to determine the atom structure of 1,1’-biphenyl-4-thiol (BPT), the molecular chain and the monolayer. CASTEP calculation shows the angle between two benzene planes is 40˚. The molecular chain of BPT consists of many parallel and tipsy molecules, and the distance between the neighbor mo- lecules is 0.37 nm. The monolayer of BPT is composed of many parallel and dislocated molecular chains, and the distance between the neighbor molecular chains is 0.66 nm. The energy interval between the monolayer and the single BPT molecule is 0.146 eV, it means the structure of the monolayer is stable. It is a self-assemble system.

2-(4-Chlorophenyl)acetamide

In the title compound, C8H8ClNO, the acetamide group is twisted out the benzene plane with a dihedral angle of 83.08 (1)°. In the crystal, mol­ecules are linked by N—H⋯O hydrogen bonds, forming layers parallel to the ab plane.

Persubstituted p-benzoquinone monoxime alkyl ethers and their molecular structure

Abstract Theoretical and experimental approaches were applied for the investigation of the reactivity of persubstituted 4-nitrosophenols in the reaction with alkyl iodides, in particular the potassium salt of 2,6-di(alkoxycarbonyl)-3,5-dimethyl-4-nitrosophenol. Hartre–Fock calculations showed that the anion negative charge was located mostly on the oxygen of hydroxyl group, while estimation of the total energy of the alkylated products pointed out the benefit of alkylation on the oxygen atom of the nitroso group yielding p-benzoquinone monoxime alkyl ethers. Methylation and ethylation of persubstituted nitrosophenols were carried out. The products obtained were investigated using X-ray diffraction, 1Н NMR spectroscopy and mass spectrometry. The crystal structure of the methyl ether of 2,6-di(alkoxycarbonyl)-3,5-dimethyl-1,4-benzoquinone-1-oxime (С15H19NO6) (I) was determined by the X-ray powder diffraction technique. The unit cell parameters were: a = 7.3322(6) A, b = 10.5039(12) A, c = 21.1520(20) A, β = 93.742(6)°, V = 1625.58(2) A3 Z = 4, Sp.Gr. P21/c. The structure modeling was made in direct space by the Monte-Carlo approach using rigid and soft restrictions. The structure refinement was completed by the Rietveld method. It was established that the alkylation occurred on the oxygen atom of the nitroso group. The molecules (I) in the crystal structure were packed in columns along the axis a with pairwise convergence in a column up to the distance of 3.63 A due to a 180° turn of every second molecule around the column axis. In the molecular structure the methyloxime group was oriented in the benzene plane and had π-conjugation with the ring. The ethoxycarbonyl groups were turned nearly perpendicular to the ring. Other compounds obtained had the structure of the alkyl ethers of 1.4-benzoquinone-1-oxime, which was proved by 1Н NMR spectroscopy and mass-spectrometry.

Regioselective Synthesis and Structure of New Oligophosphorylated rctt Resorcinarenes

Regioselective phosphorylation of rctt tetranaphthyl resorcinarenes gave monofunctionalized derivatives with eight phosphamide groups immobilized on the macrocyclic matrix, as well as heterofunctionalized derivatives containing hydroxyl groups on the vertically oriented benzene rings and phosphorus fragments on the planar benzene rings. GRAPHICAL ABSTRACT