4-Meth-oxy-benzamidinium bromide.

The title salt, C8H11N2O(+)·Br(-), was synthesized by the reaction between 4-meth-oxy-benzamidine (4-amidino-anisole) and hydro-bromic acid. In the cation, the amidinium group has two similar C-N bonds [1.304 (2) and 1.316 (2) Å], and its plane forms a dihedral angle of 31.08 (5)° with the benzene ring. The ions are associated in the crystal into a three-dimension hydrogen-bonded supra-molecular network featuring N-H(+)⋯Br(-) inter-actions.

Supramolecular association in proton-transfer adducts containing benzamidinium cations. II. Concomitant polymorphs of the molecular salt of 2,6-dimethoxybenzoic acid with benzamidine.

Two concomitant polymorphs of the molecular salt formed by 2,6-dimethoxybenzoic acid, C(9)H(10)O(4) (Dmb), with benzamidine, C(7)H(8)N(2) (benzenecarboximidamide, Benzam) from water solution have been identified. Benzamidinidium 2,6-dimethoxybenzoate, C(7)H(9)N(2)(+)·C(9)H(9)O(4)(-) (BenzamH(+)·Dmb(-)), was obtained through protonation at the imino N atom of Benzam as a result of proton transfer from the acidic hydroxy group of Dmb. In the monoclinic polymorph, (I) (space group P2(1)/n), the asymmetric unit consists of two Dmb(-) anions and two monoprotonated BenzamH(+) cations. In the orthorhombic polymorph, (II) (space group P2(1)2(1)2(1)), one Dmb(-) anion and one BenzamH(+) cation constitute the asymmetric unit. In both polymorphic salts, the amidinium fragments and carboxylate groups are completely delocalized. This delocalization favours the aggregation of the molecular components of these acid-base complexes into nonplanar dimers with an R(2)(2)(8) graph-set motif via N(+)-H···O(-) charge-assisted hydrogen bonding. Both the monoclinic and orthorhombic forms exhibit one-dimensional isostructurality, as the crystal structures feature identical hydrogen-bonding motifs consisting of dimers and catemers.

4-Meth-oxy-benzamidinium acetate.

The title compound, C8H11N2O(+)·CH3CO2(-), was synthesized by a reaction between 4-meth-oxy-benzamidine (4-amidino-anisole) and acetic acid. In the cation, the amidinium group forms a dihedral angle of 11.65 (17)° with the mean plane of the benzene ring. The ionic components are associated in the crystal via N-H(+)⋯O(-) hydrogen bonds, resulting in a one-dimensional structure consisting of dimers and catemers and orientated approximately along the c axis.

4-Meth-oxy-benzamidinium nitrate.

The title salt, C8H11N2O(+)·NO3(-), was synthesized by a reaction between 4-meth-oxy-benzamidine (4-amidino-anisole) and nitric acid. The asymmetric unit comprises a non-planar 4-meth-oxy-benzamidinium cation and a nitrate anion. In the cation, the amidinium group has two similar C-N bond lengths [1.302 (3) and 1.313 (3) Å] and its plane forms a dihedral angle of 32.66 (5)° with the mean plane of the benzene ring. The nitrate-amidinium ion pair is not planar, as the dihedral angle between the planes defined by the CN2(+) and NO3(-) units is 19.28 (6)°. The ionic components are associated in the crystal via N-H⋯O hydrogen bonds, resulting in a three-dimensional network.

4-Meth-oxy-benzamidinium hydrogen oxalate monohydrate.

The title hydrated salt, C8H11N2O(+)·C2HO4(-)·H2O, was synthesized by a reaction of 4-meth-oxy-benzamidine (4-amidino-anisole) and oxalic acid in water solution. In the cation, the amidinium group forms a dihedral angle of 15.60 (6)° with the mean plane of the benzene ring. In the crystal, each amidinium unit is bound to three acetate anions and one water mol-ecule by six distinct N-H⋯O hydrogen bonds. The ion pairs of the asymmetric unit are joined by two N-H⋯O hydrogen bonds into ionic dimers in which the carbonyl O atom of the semi-oxalate anion acts as a bifurcated acceptor, thus generating an R(1)2(6) motif. These subunits are then joined through the remaining N-H⋯O hydrogen bonds to adjacent semi-oxalate anions into linear tetra-meric chains running approximately along the b axis. The structure is stabilized by N-H⋯O and O-H⋯O inter-molecular hydrogen bonds. The water mol-ecule plays an important role in the cohesion and the stability of the crystal structure being involved in three hydrogen bonds connecting two semi-oxalate anions as donor and a benzamidinium cation as acceptor.

4-Meth-oxy-benzamidinium chloride monohydrate.

In the cation of the title compound, C(8)H(11)N(2)O(+)·Cl(-)·H(2)O, the C-N bonds of the amidinium group are identical within experiemental error [1.305 (2) and 1.304 (2) Å], and its plane forms a dihedral angle of 25.83 (8)° with the phenyl ring. The ionic components are associated in the crystal into polymeric hydrogen-bonded supra-molecular tapes stabilized by N-H(+)⋯Cl(-) and N-H(+)⋯Ow inter-molecular hydrogen bonds, and by Ow-H⋯Cl(-) inter-actions.

4-Meth-oxy-benzamidinium hydrogen sulfate.

The title salt, C(8)H(11)N(2)O(+)·HSO(4) (-), has been synthesized by the reaction between 4-meth-oxy-benzamidine and sulfuric acid. The asymmetric unit comprises a nonplanar 4-meth-oxy-benzamidinium cation and one hydrogen sulfate anion. In the cation, the amidinium group has two identical C-N bonds [1.306 (2) and 1.308 (2) Å], and its plane forms a dihedral angle of 6.49 (8)° with the mean plane of the benzene ring. The ionic components are associated in the crystal via N-H(+)⋯O(-), resulting in chains running approximately along the b-axis direction whicg are interconnected by O-H⋯O(-) hydrogen bonds.

Testing a Variety of Electronic-Structure-Based Methods for the Relative Energies of 5-Formyluracil Crystals.

The lattice energies of the experimental and several hypothetical crystal structures of the RNA base uracil derivative 5-formyluracil are calculated with a range of methods, based either on the electronic structure of the molecule or the lattice. The explicit modeling of the polarization within the crystal in the model intermolecular potential and the inclusion of an empirical dispersion correction to the periodic density functional energy (DFT-D2) were the only methods able to calculate the energy balance between different conformations, hydrogen bonding, and π-π stacking possibilities sufficiently accurately to give the observed structure as the most stable. Even these two methods underestimated the density of the room temperature structure, showing the need for improvement in the modeling of organic crystal structures.

Conformational effects in photoelectron circular dichroism of alaninol.

A photoelectron circular dichroism (CD) study of the valence states of 2-amino-1-propanol (alaninol) in the gas phase is presented. The aim of the investigation is to reveal conformer population effects in the valence-state photoelectron spectrum. The experimental dispersion of the dichroic D parameter of valence states as a function of the photon excitation energy is compared with its theoretical value calculated by employing a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian. The theoretical values are in very good agreement with the experimental data when the conformer population distribution is taken into account. Moreover, thanks to a comparison between experiment and theory, a clear assignment of the molecular orbital character and conformer geometry is given to the features of the photoelectron spectrum. This work indicates in a detailed experimental analysis that CD in photoelectron spectroscopy is an effective technique to disentangle the conformer assignment in photoelectron spectra.

Two-dimensional chiral single domain by D-alaninol functionalization of Cu(100).

We report the results of chemisorption in saturating conditions of D-alaninol on Cu(100) in term of the analysis of low-energy electron diffraction and scanning tunneling microscopy data. A large two-dimensional, single domain, ordered chiral structure of quadrangular tetrameric molecular units is formed. The four molecules interact differently with the surface in the two orthogonal directions.