Mohamed Ashraf

The Electro‐Optic Response of a Zwitterionic Non‐linear Optical (NLO) Material

Measurements of the electro‐optic coefficient, r33, of a zwitterionic organic chromophore are reported. Amorphous polycarbonate and chromophore were mixed and spin‐processed to obtain host‐guest polymer thin films for measurement with a Teng‐Man modulation eillipsometer. After poling, the films exhibited an r33 of 100 pm/V at a measurement wavelength of 1310 nm, around three times greater than that of crystalline LiNbO3. Given this chromophore’s high figure of merit a high r33 is expected, although the electro‐optic response in the poled polymer films decayed rapidly over several days.

Crystal and Molecular Structure of 7-Diethylamino-[1′,3′,3′-trimethyl-4-((1,3,3-trimethyl-1,3-dihydro-2H-indole-2-ylidene)methyl)-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole]]: A Dicondensation Product From the Reaction of 4-Diethylaminosalicylaldehyde with Fischer's Base

The novel molecule, 7-diethylamino-[1′,3′,3′-trimethyl-4-((1,3,3-trimethyl-1,3-dihydro-2H-indole-2-ylidene)methyl)-1′,3,3′,4-tetrahydrospiro[chromene-2,2′-indole]], was isolated as the product from the condensation of diethylaminosalicylaldehyde with two equivalents of Fischer’s base and its crystal structure determined, initially using MoKα radiation. The diffraction data at higher theta angles (d < 0.9 A) was notably weak so a further dataset was collected using CuKα to determine the cause. Although a different crystal batch and larger crystal was used and a better dataset obtained (with significantly improved atomic resolution) the comparison shows that the essential molecular features and weak intermolecular binding are duplicated in the refinement with the latter data. Comparison is made with a closely related structure. Consistent with observations for this related structure it is proposed that the product is formed through the interception of an intermediate carbinol by Fischer’s base.

2-{3-Cyano-4-[2-(4-diethylamino-2-hy-droxyphenyl)ethenyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}malononitrile acetone 0.25-solvate.

In the title compound, C22H22N4O2·0.25C3H6O, the disordered acetone molecule lies with partial occupancy about the 2 axis. The molecule of the malononitrile derivative is essentially planar excluding the methyl groups, with the largest deviation from the mean plane through the non-H atoms being 0.1955 (13) Å. Two rotamers with different orientations of the benzene ring are observed in the ratio of 0.919 (2):0.081 (2), and as a result the OH group is disordered over two sets of sites. In the crystal, the molecules form ribbons along (101) utilizing a strong O—H⋯N(cyano) hydrogen bond. Interleaving of the nearly planar ribbons is provided by the twofold disordered acetone molecule through C—H⋯O interactions.

2-{[(Biphenyl-2-yl)diazen­yl]methyl­idene}-1,3,3-trimethyl­indoline

The title molecule, C24H23N3, shows some delocalization of charge based on the small [8.0 (2)°] angle between the indolin-2-ylidene ring system and the link methyldiazene C2N2 atom plane. A further twist of 17.2 (3)° is subtended between the C2N2 plane and its attached benzene ring. The dihedral angle between the biphenyl rings is 47.96(14)°. In the crystal, the molecules pack via C—H⋯π attractive interactions.

2-[4-(2-{5-tert-Butyl-2-chloro-3-[2-(3-pentyl-1,3-benzothia-zol-2-yl-idene)ethyl-idene]cyclo-hex-1-en-yl}ethen-yl)-3-cyano-5,5-dimethyl-furan-2-yl-idene]malono-nitrile.

In the title molecule, C36H39ClN4OS, the non-aromatic part of the cyclohex-1-enyl ring and the attached tert-butyl group are disordered over two conformations with occupancy ratios of 0.52 (3):0.48 (3) and 0.53 (3):0.47 (3), respectively. The polyene chain single- and double-bond dimensions contrast with a closely related compound [Bouit et al. (2007 ▶). Chem. Mater. 19, 5325–5335] with an approximate 19° twist between donor and acceptor ends of the molecule, related to the additional intramolecular C—H⋯S interaction. In the title compound, the molecules pack into dimeric units about centres of symmetry utilizing weak C—H⋯N(cyano) and C—H⋯O attractive interactions, building both chain and ring motifs about the centres [R 2 2(8) and R 2 2(9)]. Adjacent dimeric sets then form a herringbone configuration.

4-tert-Butyl-2-[2-(1,3,3-trimethyl-indolin-2-yl-idene)ethyl-idene]cyclo-hexa-none.

The title molecule, C23H31NO, has two alternative cyclohexanone configurations at the 4-position in a ratio of 0.663 (3):0.337 (3). The plane of the five-membered planar ring in the indolin-2-ylidene subtends an angle of 2.19 (7)° with its fused aromatic ring, an angle of 16.24 (8)° with the plane of the major cyclohexanone configuration and an angle of 8.54 (15)° with the bridging planar ethylidene C atoms. These last atoms subtend an angle of 8.37 (16)° with the mean plane through the major cyclohexanone configuration. The molecules pack approximately parallel to the (01) plane via C—H⋯π and C—H⋯O interactions.

Bis(2-carb­oxy-N-{[1-(2-hy­droxy­eth­yl)-3,3-dimethyl­indolin-2-yl­idene]methyl­imino}­anilinium) sulfate monohydrate

The asymmetric unit of the title compound, 2C20H22N3O3 +·SO4 2−·H2O, contains four cations, two sulfate anions and two lattice water molecules. One of the four cations shows a different conformation of the hydroxyethyl group; the remaining three are all essentially superimposable. Two cations exhibit two-site orientational disorder [ratios = 0.524 (5):0.476 (5) and 0.616 (6):0.384 (6)] of the last two atoms of their hydroxyethyl groups, and one water molecule is disordered over two positions in a 0.634 (13):0.366 (13) ratio. Each imine H atom is intramolecularly in contact with the adjacent carboxyl O atom, forming an S(6) motif, while all the carboxylic acid H atoms are hydrogen bonded to O atoms of the sulfate anions. Other notable hydrogen-bond interactions involve (methylene, phenyl and imine chain) C—H⋯O (sulfate and carboxyl) and O—H⋯O(water) contacts, making up a comprehensive three-dimensional network involving D 2 2(n), with n = 4–6 and 15–16, and C 2 2(17) classical hydrogen-bond motifs. The crystal investigated was twinned by pseudomerohedry with a twin component ratio of 0.4745 (12):0.5255 (12).

Optimizing the second-order nonlinear optical response in some indoline-based chromophores at the molecular and macroscopic levels

The effect of extending the conjugation length, the deployment of various substituents and configurational locking of the polyene backbone on the second-order nonlinear optical (NLO) response of a series of indoline based compounds has been investigated. The compounds were examined using Hyper-Rayleigh scattering (HRS) and relative second-harmonic generation (SHG) techniques with a femtosecond operating system with a 1300 nm fundamental wavelength. All of the compounds were found to have high molecular hyperpolarizabilities with β values of up to 1230 × 10-30 esu. At the macroscopic level-for poled polymer thin films-a strong second-order NLO signal has been detected and d33 values of up to 217 pm/V are found-a response of some ten times greater than that found for the well known azo dye Disperse Red 1.

4-Aminopyridinium 2-(anthracen-9-yl)-3-oxo-3H-inden-1-olate monohydrate

The title compound, 2C(5)H(7)N(2)(+)·2C(23)H(13)O(2)(-)·H(2)O, formed as a by-product in the attempted synthesis of a nonlinear optical candidate molecule, contains two independent 4-aminopyridinium cations and 2-(anthracen-9-yl)-3-oxo-3H-inden-1-olate anions with one solvent water molecule. This is the first reported structure containing these anions. The two anions are not planar, having different interplanar angles between the anthracenyl and inden-1-olate moieties of 59.07 (5) and 83.92 (5)°. The crystal packing, which involves strong classical hydrogen bonds and one C-H...π interaction, appears to account for both the nonplanarity and this difference.