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The title mol­ecule, C15H9NO4, is non-planar, with the unusually large dihedral angle between mean planes of phenyl ring and chromone moiety being 50.73 (5)°., The geometry of the title mol­ecule [systematic name: 2-(2-nitro­phen­yl)-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 inter­actions 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 mol­ecular surface was calculated in order to determine the potential binding sites to receptors.

In the title mol­ecule, which is based on a 1,4-distyryl-2,5-di­meth­oxy­benzene 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 inter­actions., The title compound DBNB, C24H20N2O6, has been crystallized and studied by X-ray diffraction, spectroscopic and computational methods. In the title mol­ecule, which is based on a 1,4-distyryl-2,5-di­meth­oxy­benzene 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 inter­actions. 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.

We report on the effect of residual ions in dielectric sol–gel films based on 2-cyanoethyltrimethoxysilane (CNETMS) on their dielectric and energy storage properties for pulsed power applications. A wide range of pH from 1.5 to 6.5 is employed to catalyze CNETMS sol–gel films. The sol–gel films processed at near neutral pH exhibit improved dielectric and energy storage characteristics including a Weibull modulus of 11, an order of magnitude reduction of leakage current, and an extractable energy density of 32 J cm−3 with an energy extraction efficiency of 80% at 685 V μm−1, as compared with the films processed at pH 1.5. These improvements are attributed to the reduced amount of ions within the sol–gel films, which is believed to suppress the detrimental effects of mobile charge carriers that are likely to trigger field-driven scattering and impact ionization, and subsequent catastrophic electrical breakdown under high electrical stress. The present work suggests the importance of engineering residual charge carriers in dielectric sol–gel films based on trifunctional alkoxysilanes for pulsed power applications.

The crystallization from different solvents of homologues of 1,3-diethyl-2-thiobarbituric acid and p-dimethylaminobenzene with different lengths of the polymethine bridge between donor and acceptor groups (TB[n]) produced three pairs of polymorphs with the number of C═C bonds in the chain n = 1, 3, and 5. The homologues with the shortest (one methine unit) π-conjugated bridge were presented by two concomitant (obtained simultaneously) polymorphs. Bond length alternation values calculated using X-ray data and evaluation using NMR data showed that some homologues possesses a very high hyperpolarizability. It was shown that the increase of polarizability is related to the increase in the length of the π-conjugated bridge that was supported by experimental hyper-Rayleigh scattering data. Density functional theory calculations of HOMO/LUMO molecular energy levels indicated that compounds with a longer π-conjugated bridge have a higher thermal stability.

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 (D 1 and D 2) and represent examples of the D 1–π–A–π–D 2 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.

The synthesis and crystal structures of 1,3-diethyl-5-{(2E,4E)-6-[(E)-1,3,3-tri­methyl­indolin-2-yl­idene]hexa-2,4-dien-1-yl­idene}pyrimidine-2,4,6(1H,3H,5H)-trione or TMI, C25H29N3O3, and 1,3-diethyl-2-sulfanyl­idene-5-[2-(1,3,3-tri­methyl­indolin-2-yl­idene)ethyl­idene]di­hydro­pyrimidine-4,6(1H,5H)-dione or DTB, C21H25N3O2S, are described. 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., Two compounds, 1,3-diethyl-5-{(2E,4E)-6-[(E)-1,3,3-tri­methyl­indolin-2-yl­idene]hexa-2,4-dien-1-yl­idene}pyrimidine-2,4,6(1H,3H,5H)-trione or TMI, C25H29N3O3, and 1,3-diethyl-2-sulfanyl­idene-5-[2-(1,3,3-tri­methyl­indolin-2-yl­idene)ethyl­idene]di­hydro­pyrimidine-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, mol­ecules are packed in a herringbone manner with differences in the twist and fold angles. In both structures, the mol­ecules are connected by weak C—H⋯O and/or C—H⋯S bonds.

Structural and spectroscopic characteristics of merocyanine dyes are important because of their potential applications in optoelectronics and sensors. Herein we report synthesis, X-ray diffraction characterization of crystal structure, spectroscopic and NMR studies of four merocyanine dyes which, according to their strong donor-acceptor structure, exhibit a second order polarizability (β). Crystallographic studies demonstrated an almost planar structure of all molecules and indicated the occurrence of conformational changes in π-conjugated bridge between donor and acceptor. For three homologues similar packing modes, defined mostly by week C H⋯N interactions, were found in crystals. Bond length alternation (BLA) values have been evaluated using crystallographic and NMR data and have shown a correlation to their nonlinear optical activity. Second order polarizabilities for all compounds were measured using hyper Rayleigh scattering (HRS) in solution. It was found that the merocyanines studied exhibit very large second order polarizabilities (up to 4.1 10−27 esu), making them potentially useful for materials for second harmonic generation (SHG). Unfortunately, they do not demonstrate acentric packing of chromophores, which is required for SHG in the crystalline state, but may show promise for other applications such as poled polymer blends or for SHG sensing in biological environments.

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.

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.

Polymer/ceramic nanocomposites provide a means of combining the high permittivities (εr) of metal oxide nanoparticles with the solution-processability and high dielectric strength of polymeric hosts. Simple mixing of nanoparticles and polymers generally results in poor quality nanocomposites due to the agglomeration of nanoparticles and poor miscibility of nanoparticles with host materials. We have shown that surface modification of metal oxide nanoparticles with phosphonic acid-based ligands affords robust surface modification and improves the processiblity and the quality of the resulting nanocomposites. We report on the use of phosphonic-acid modified barium titanate (BaTiO3, BT) nanoparticles in dielectric nanocomposites and their applications to high-energy-density capacitors and solution-processable high permittivity gate insulators in organic field-effect transistors (OFETs). Surface modification of BT nanoparticles enabled the formation of high quality nanocomposite thin films with ferroelectric polymer hosts such as poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), with large volume fractions (up to 50 vol. %), which are potentially useful materials for electrical energy storage. Similarly, the use of phosphonic acid-modified BT nanoparticles in cross-linked poly(4-vinylphenol) (PVP) allowed to form gate insulators for OFETs. High quality nanocomposite thin films at high nanoparticle volume fractions (up to 37 vol. %) with a large capacitance density (∼50 nF/cm2) and a low leakage current (10−8 A/cm2) were obtained. Pentacene-based p-type OFETs using these nanocomposites showed a large on/off current ratio (Ion/off 104 ∼ 106). We will also present the results from a recent experimental and theoretical study where the BT nanoparticle volume fraction was systematically varied in P(VDF-HFP) host, εr = 11, to find the optimum permittivity and dielectric strength, which provided a guideline for the optimization of the volume fraction for achieving maximum energy density.