Structural (at 100†K) and DFT studies of 2'-nitro-flavone.

The geometry of the title mol-ecule [systematic name: 2-(2-nitro-phen-yl)-4H-chromen-4-one], C15H9NO4, is determined by two dihedral angles formed by the mean plane of phenyl ring with the mean planes of chromone moiety and nitro group, being 50.73 (5) and 30.89 (7)°, respectively. The crystal packing is determined by π-π inter-actions and C-H⋯O contacts. The results of DFT calculations at the B3LYP/6-31G* level of theory provided an explanation of the unusually large dihedral angle between the chromone moiety and the phenyl group. The electrostatic potential map on the mol-ecular surface was calculated in order to determine the potential binding sites to receptors.

Mol-ecular and crystal structure, lattice energy and DFT calculations of two 2'-(nitro-benzo-yloxy)aceto-phenone isomers.

The two isomers 2'-(4-nitro-benzo-yloxy)aceto-phenone (systematic name: 2-acetyl-phenyl 4-nitro-benzoate) (I) and 2'-(2-nitro-benzo-yloxy)aceto-phenone (systematic name: 2-acetyl-phenyl 2-nitro-benzoate) (II), both C15H11NO5, with para and ortho positions of the nitro substituent have been crystallized and studied. It is evident that the variation in the position of the nitro group causes a significant difference in the mol-ecular conformations: the dihedral angle between the aromatic fragments in the mol-ecule of I is 84.80 (4)°, while that in the mol-ecule of II is 6.12 (7)°. Diffraction analysis revealed the presence of a small amount of water in the crystal of I. DFT calculations of the mol-ecular energy demonstrate that the ortho substituent causes a higher energy for isomer II, while crystal lattice energy calculations show that the values are almost equal for two isomers.

Mol-ecular and crystal structure, optical properties and DFT studies of 1,4-dimeth-oxy-2,5-bis-[2-(4-nitro-phen-yl)ethen-yl]benzene.

The title compound DBNB, C24H20N2O6, has been crystallized and studied by X-ray diffraction, spectroscopic and computational methods. In the title mol-ecule, which is based on a 1,4-distyryl-2,5-di-meth-oxy-benzene core with p-nitro-substituted terminal benzene rings, the dihedral angle between mean planes of the central fragment and the terminal phenyl ring is 16.46 (6)°. The crystal packing is stabilized by π-π inter-actions. DFT calculations at the B3LYP/6-311 G(d,p) level of theory were used to compare the optimized structures with the experimental data. Energy parameters, including HOMO and LUMO energies, their difference, and vertical excitation and emission energies were obtained.

Crystal structures, syntheses, and spectroscopic and electrochemical measurements of two push-pull chromophores: 2-[4-(di-methyl-amino)-benzyl-idene]-1H-indene-1,3(2H)-dione and (E)-2-{3-[4-(di-meth-ylamino)-phen-yl]allyl-idene}-1H-indene-1,3(2H)-dione.

The title pull-push chromophores, 2-[4-(di-methyl-amino)-benzyl-idene]-1H-indene-1,3(2H)-dione, C18H15NO2 (ID[1]) and (E)-2-{3-[4-(di-methyl-amino)-phen-yl]allyl-idene}-1H-indene-1,3(2H)-dione, C20H17NO2 (ID[2]), have donor-π-bridge-acceptor structures. The mol-ecule with the short π-bridge, ID[1], is almost planar while for the mol-ecule with a longer bridge, ID[2], is less planar. The benzene ring is inclined to the mean plane of the 2,3-di-hydro-1H-indene unit by 3.19 (4)° in ID[1] and 13.06 (8)° in ID[2]. The structures of three polymorphs of compound ID[1] have been reported: the α-polymorph [space group P21/c; Magomedova & Zvonkova (1978 ▸). Kristallografiya, 23, 281-288], the ß-polymorph [space group P21/c; Magomedova & Zvonkova (1980 ▸). Kristallografiya, 25 1183-1187] and the γ-polymorph [space group Pna21; Magomedova, Neigauz, Zvonkova & Novakovskaya (1980 ▸). Kristallografiya, 25, 400-402]. The mol-ecular packing in ID[1] studied here is centrosymmetric (space group P21/c) and corresponds to the ß-polymorph structure. The mol-ecular packing in ID[2] is non-centrosymmetric (space group P21), which suggests potential NLO properties for this crystalline material. In both compounds, there is short intra-molecular C-H⋯O contact present, enclosing an S(7) ring motif. In the crystal of ID[1], mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming layers parallel to the bc plane. In the crystal of ID[2], mol-ecules are liked by C-H⋯O hydrogen bonds to form 21 helices propagating along the b-axis direction. The mol-ecules in the helix are linked by offset π-π inter-actions with, for example, a centroid-centroid distance of 3.9664 (13) Š(= b axis) separating the indene rings, and an offset of 1.869 Å. Spectroscopic and electrochemical measurements show the ability of these compounds to easily transfer electrons through the π-conjugated chain.

Synthesis and structure of push-pull merocyanines based on barbituric and thio-barbituric acid.

Two compounds, 1,3-diethyl-5-{(2E,4E)-6-[(E)-1,3,3-tri-methyl-indolin-2-yl-idene]hexa-2,4-dien-1-yl-idene}pyrimidine-2,4,6(1H,3H,5H)-trione or TMI, C25H29N3O3, and 1,3-diethyl-2-sulfanyl-idene-5-[2-(1,3,3-tri-methyl-indolin-2-yl-idene)ethyl-idene]di-hydro-pyrimidine-4,6(1H,5H)-dione or DTB, C21H25N3O2S, have been crystallized and studied. These compounds contain the same indole derivative donor group and differ in their acceptor groups (in TMI it contains oxygen in the para position, and in DTB sulfur) and the length of the π-bridge. In both materials, mol-ecules are packed in a herringbone manner with differences in the twist and fold angles. In both structures, the mol-ecules are connected by weak C-H⋯O and/or C-H⋯S bonds.

Synthesis and structural study of organic two-photon-absorbing cycloalkanone chromophores.

The three organic two-photon-absorbing cycloalkanone chromophores 2,4-bis[4-(diethylamino)benzylidene]cyclobutanone, C26H32N2O (I), 2,5-bis[4-(diethylamino)benzylidene]cyclopentanone, C27H34N2O (II), and 2,6-bis[4-(diethylamino)benzylidene]cyclohexanone, C28H36N2O (III), were obtained by a reaction between 4-(diethylamino)benzaldehyde and the corresponding cycloalkanone and were characterized by single-crystal X-ray diffraction studies, as well as density functional theory (DFT) quantum-chemical calculations. Molecules of this series have three main fragments, i.e. central acceptor (A) and two terminal donors (D1 and D2) and represent examples of the D1-π-A-π-D2 molecular design. All three compounds crystallize with two crystallographically independent molecules in the asymmetric unit (A and B) and are distinguished by the conformations of both the molecular Et2N-C6H4-C=C-C(=O)-C=C-C6H4-NEt2 backbone (arcuate or linear) and the terminal diethylamino substituents (syn- or antiperiplanar to the plane of the molecule). The central four- and five-membered rings in I and II are almost planar, and the six-membered ring in III adopts a sofa conformation. In the crystals of I-III, the two independent molecules A and B form hydrogen-bonded [A...B] dimers via intermolecular C-H...O hydrogen bonds. Furthermore, the [A...B] dimers in I are bound by intermolecular C-H...O hydrogen bonds into two-tier puckered layers, whereas in the crystals of II and III, the [A...B] dimers are stacked along the c and a axes, respectively. Taking into account the decreasing steric strain upon expanding the central ring, compound I might be more efficient as a two-photon absorption chromophore than compounds II and III, which corresponds to the results of spectroscopic studies.

Crystal structure of tetra-methyl-ammonium 1,1,7,7-tetra-cyano-hepta-2,4,6-trienide.

The title compound, C4H12N+·C11H5N4 -, contains one tetra-methyl-ammonium cation and one 1,1,7,7-tetra-cyano-hepta-2,4,6-trienide anion in the asymmetric unit. The anion is in an all-trans conjugated C=C bonds conformation. Two terminal C(CN)2 di-nitrile moieties are slightly twisted from the polymethine main chain to which they are attached [C(CN)2/C5 dihedral angles = 6.1 (2) and 7.1 (1)°]. The C-C bond distances along the hepta-dienyl chain vary in the narrow range 1.382 (2)-1.394 (2) Å, thus indicating the significant degree of conjugation. In the crystal, the anions are linked into zigzag chains along the [10] direction by C-H⋯N(nitrile) short contacts. The anti-parallel chains stack along the [110] direction with alternating separations between the neighboring anions in stacks of 3.291 and 3.504 Å. The C-H⋯N short contacts and stacking inter-actions combine to link the anions into layers parallel to the (01) plane and separated by columns of tetra-methyl-ammonium cations.

Synthesis, crystal structure studies and solvatochromic behaviour of two 2-{5-[4-(dimethylamino)phenyl]penta-2,4-dien-1-ylidene}malononitrile derivatives.

The synthesis, crystal structure studies and solvatochromic behavior of 2-{(2E,4E)-5-[4-(dimethylamino)phenyl]penta-2,4-dien-1-ylidene}malononitrile, C16H15N3 (DCV[3]), and 2-{(2E,4E,6E)-7-[4-(dimethylamino)phenyl]hepta-2,4,6-trien-1-ylidene}malononitrile, C18H17N3 (DCV[4]), are reported and discussed in comparison with their homologs having a shorter length of the π-conjugated bridge. The compounds of this series have potential use as nonlinear materials with second-order effects due to their donor-acceptor structures. However, DCV[3] and DCV[4] crystallized in the centrosymmetric space group P21/c which excludes their application as nonlinear optical materials in the crystalline state. They both crystallize with two independent molecules having the same molecular conformation in the asymmetric unit. The series DCV[1]-DCV[4] demonstrated reversed solvatochromic behavior in toluene, chloroform, and acetonitrile.

High energy density nanocomposites based on surface-modified BaTiO(3) and a ferroelectric polymer.

The dielectric permittivity and electric breakdown strength of nanocomposites comprising poly(vinylidene fluoride-co-hexafluoro propylene) and phosphonic acid surface-modified BaTiO(3) nanoparticles have been investigated as a function of the volume fraction of nanoparticles. The mode of binding of pentafluorobenzylphosphonic acid on the BaTiO(3) particles was investigated using infrared and (31)P solid-state nuclear magnetic resonance spectroscopy, and the phosphonic acid was found to form well ordered, tightly bound monolayers. The effective permittivity of nanocomposites with low volume fractions (<50%) was in good agreement with standard theoretical models, with a maximum relative permittivity of 35. However, for nanoparticle volume fractions of greater than 50%, the effective permittivity was observed to decrease with increasing nanoparticle volume fraction, and this was correlated with an increase in porosity of the spin-coated nanocomposite films. The dielectric breakdown strength was also found to decrease with increasing volume fraction of the BaTiO(3) nanoparticles, with an abrupt decrease observed around 10% and a gradual decrease for volume fractions of 20-50%. Comparison of these results with model calculations, using statistical particle packing simulations and effective medium theory for the permittivity and breakdown strength, indicates the important roles of nanoparticle percolation and porosity of the nanocomposites on the dielectric properties. The measured energy density at a field strength of 164 V/mum, well below the breakdown strength, increased to a value of 3.2 J/cm(3) as the nanoparticle volume fraction is increased to 50%, roughly in line with the trend of the permittivity. The calculated maximum energy densities indicate maximal extractable energy (7-8 J/cm(3) at 1 kHz) for two different particle volume fractions, as a result of the interplay of the dependencies of permittivity and breakdown strength on volume fraction.