Light losses from scattering in luminescent solar concentrator waveguides.

The reductions in the transmission of emission originating from a fluorophore dissolved in a polymer matrix due to light scattering were compared in two forms of planar waveguides used as luminescent solar concentrators: a thin film of poly(methylmethacrylate) (PMMA) spin-coated on a glass plate and a solid PMMA plate of the same dimensions. The losses attributable to light scattering encountered in the waveguide consisting of the thin film of polymer coated on a glass plate were not detectable within experimental uncertainty, whereas the losses in the solid polymer plate were significant. The losses in the solid plate are interpreted as arising from light-scattering centers comprising minute bubbles of vapor/gas, incomplete polymerization or water clusters that are introduced during or after the thermally induced polymerization process.

The photophysics of phenylenevinylene oligomers and self-absorption of their fluorescence in polymer films.

The fluorescence spectra, quantum yields and lifetimes of a series of alkoxy-substituted phenylenevinylene molecules, which serve as short chain oligomer models for poly(p-phenylenevinylene), have been determined in fluid solvents and in a high viscosity polymer matrix. The effects of solvent polarity and a high viscosity molecular environment on the fluorescence yields and spectral shapes have been established. Alkoxy group substitution on the phenyl ring moieties of the molecules has an important effect on the vibronic structures and profiles of the absorption spectra. This was interpreted in terms of hot-band, ground to excited singlet state transitions from energetically closely-spaced torsional vibrational levels of the vinylene double bond in the ground state. The shapes of the absorption bands affect the overlaps of the absorption and fluorescence spectra. This has been quantified as the probability of fluorescence reabsorption in solid polymer films as a function of pathlength. This is an important determinant of the efficacies of these compounds for "harvesting" solar energy in luminescent solar concentrator systems. The reabsorption probabilities of these compounds are lower for all pathlengths than those determined in the same polymer film for the fluorophores, perylene and perylene diimide, which have been considered for concentrating spatially diffuse sunlight.

2-{2-[5-(4-Cyano-5-di-cyano-methyl-idene-2,2-dimethyl-2,5-di-hydro-furan-3-yl)penta-2,4-dienyl-idene]-3,3-dimethyl-2,3-di-hydro-1H-indol-1-yl}ethyl 3,5-bis-(benz-yloxy)benzoate.

In the title mol-ecule, C48H42N4O5, a potential non-linear optical compound, the furan ring [r.m.s. deviation = 0.010 (1) Å] and the indolyl-idene ring system [r.m.s. deviation = 0.013 (2) Å] are inclined to one another by 18.52 (6)°. This is similar to the arrangement [16.51 (18)°] found for the N-hy-droxy-ethyl adduct of the title compound [Bhuiyan et al. (2011 ▶). Mol. Cryst. Liq. Cryst. 548, 1-12]. Replacing the hy-droxy-ethyl group with 3,5-di-benzyl-oxybenzoate has not resulted in a non-centrosymmetric lattice arrangement or significant changes to the basic mol-ecular structure. In the crystal, mol-ecules are linked via pairs of C-H⋯N hydrogen bonds, forming inversion dimers with an R (2) 2(20) ring motif. The dimers are linked via C-H⋯O hydrogen bonds, forming C(17) chains along [010]. The chains are linked by further C-H⋯N hydrogen bonds, forming layers parallel to (001) and enclosing R 2 (2)(44) ring motifs. There are also C-H⋯π inter-actions present, stabilizing the inter-layer orientation of the pendant bis-(benz-yloxy)benzo-yloxy group.

2-(3-Cyano-4-{3-[1-(2-hy-droxy-eth-yl)-3,3-dimethyl-1,3-di-hydro-indol-2-yl-idene]prop-2-en-yl}-5,5-dimethyl-5H-furan-2-yl-idene)malono-nitrile.

The title compound, C25H24N4O2, adopts a cisoid configuration and has twofold orientational disorder of the 2-hy-droxy-ethyl group. The mol-ecule is twisted from planarity so that the dihedral angle between the terminating indol-2-yl-idene and the furan-2-yl-idene moiety mean planes is 12.75 (7)°. Conformational disorder occurs at the indol-2-yl-idene N atom, which results in two orientations for the hy-droxy-ethyl group [occupancy ratio = 0.896 (2):0.104 (2)], and the hy-droxy O atom of the 2-hy-droxy-ethyl group is located over three sites [occupancy ratio = 0.548 (2):0.348 (2):0.104 (2)]. An intra-molecular C-H⋯O hydrogen bond involving the lowest occupancy hy-droxy O atom is observed. In the crystal, the mol-ecules pack in parallel dimeric sheets about centres of symmetry, utilizing O-H⋯N(cyano), C-H⋯N(cyano) and O-H⋯O hydrogen bonds, in two sets parallel to (02-1) and (021) planes.

1-(2,3-Di-hydroxy-prop-yl)-4-{2-[4-(di-methyl-amino)-phen-yl]vin-yl}pyridinium chloride.

The title compound, C18H23N2O2 (+)·Cl(-), crystallizes with two independent cations and anions per cell. Each cation has twofold rotational disorder about the linking vinyl groups but with unequal occupancies [0.963 (5):0.037 (5) and 0.860 (8):0.140 (8)]. The two independent cations are close to being related by an inversion centre but the data does not support the expected centrosymmetric space-group assignment. The conclusion is that the differing rotational disorder has lead to an overall non-centrosymmetric lattice. In the crystal, the mol-ecules pack in layers parallel to (133) and (-13-3), chain-linked with motif C (1) 2(7) by the di-hydroxy-propyl O-H⋯Cl⋯H-O hydrogen bonds. Other lattice binding is provided by O-H⋯Cl, C-H⋯Cl and C-H⋯N inter-actions.

1-(4-{[(1,3,3-Tri-methyl-indolin-2-yl-idene)meth-yl]diazen-yl}phen-yl)ethanone.

The title compound, C20H21N3O, has crystallographic mirror symmetry with all non-H atoms apart from the methyl C atom of the CMe2 group lying on the mirror plane. Mol-ecules are linked into planar sheets parallel to (010) by phen-yl-azo C-H⋯N and phen-yl-ethanone C-H⋯O inter-actions. Methyl C-H⋯π inter-actions provide crosslinking between the planes.

4-Methyl-5-(4-nitro-benzyl-idene)-2-oxo-2,5-di-hydro-1H-pyrrole-3-carbo-nitrile.

Mol-ecules of the potential non-linear optical title compound, C13H9N3O3, form dimeric stacks of mol-ecules along the a axis cross-linked around inversion centers by N-H⋯O hydrogen bonds and weak (phen-yl)C-H⋯O inter-molecular inter-actions, forming a 'collaboration' of R 2 (2)(8) and R 2 (2)(16) ring motifs. The mol-ecules are then further linked by weak C-H⋯O and C-H⋯N inter-actions into sheets parallel to (121).

(E)-5-[3-Cyano-2-(dicyano-methyl-ene)-1-oxaspiro-[4.5]dec-3-en-4-yl]-3-(1-methyl-1,4-dihydro-pyridin-4-yl-idene)pent-4-en-1-yl 3,5-bis-(benz-yloxy)benzoate.

In the title compound, C45H40N4O5, the cyclo-hexane entity on the (3-cyano-2,5-dihydro-furan-2-yl-idene)propane-dinitrile group, which replaces the usual dimethyl substituents, has not perturbed the delocalization geometry significantly. Weak inter-molecular inter-actions, viz. C-H⋯N(cyano), C-H⋯O(ether), C-H⋯π and π-π [between the aromatic rings with the shortest centroid-centroid distance of 3.603 (3) Å], consolidate the crystal packing, which exhibits voids of 57 Å(3).

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 mol-ecule, C36H39ClN4OS, the non-aromatic part of the cyclo-hex-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 mol-ecule, related to the additional intra-molecular C-H⋯S inter-action. In the title compound, the mol-ecules pack into dimeric units about centres of symmetry utilizing weak C-H⋯N(cyano) and C-H⋯O attractive inter-actions, building both chain and ring motifs about the centres [R2(2)(8) and R2(2)(9)]. Adjacent dimeric sets then form a herringbone configuration.

Bis(2-carb-oxy-N-{[1-(2-hy-droxy-eth-yl)-3,3-dimethyl-indolin-2-yl-idene]methyl-imino}-anilinium) sulfate monohydrate.

The asymmetric unit of the title compound, 2C20H22N3O3(+)·SO4(2-)·H2O, contains four cations, two sulfate anions and two lattice water mol-ecules. One of the four cations shows a different conformation of the hy-droxy-ethyl 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 hy-droxy-ethyl groups, and one water mol-ecule is disordered over two positions in a 0.634 (13):0.366 (13) ratio. Each imine H atom is intra-molecularly in contact with the adjacent carboxyl O atom, forming an S(6) motif, while all the carb-oxy-lic acid H atoms are hydrogen bonded to O atoms of the sulfate anions. Other notable hydrogen-bond inter-actions involve (methyl-ene, phenyl and imine chain) C-H⋯O (sulfate and carbox-yl) and O-H⋯O(water) contacts, making up a comprehensive three-dimensional network involving D2(2)(n), with n = 4-6 and 15-16, and C2(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).

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, C(22)H(22)N(4)O(2)·0.25C(3)H(6)O, the disordered acetone mol-ecule lies with partial occupancy about the 2 axis. The mol-ecule 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 mol-ecules form ribbons along (101) utilizing a strong O-H⋯N(cyano) hydrogen bond. Inter-leaving of the nearly planar ribbons is provided by the twofold disordered acetone molecule through C-H⋯O inter-actions.

Testing computational models of hyperpolarizability in a merocyanine dye using spectroscopic and DFT methods.

The structural and electronic properties of a highly solvatochromic merocyanine dye, 2-(3-cyano-5,5-dimethyl-4-(3-(1-octadecylpyridin-4(1H)-ylidene)prop-1-enyl)furan-2(5H)-ylidene)malononitrile (pyr3pi), have been investigated using UV-vis, NMR, hyper-Rayleigh scattering, and Raman spectroscopies and further interpreted using computational chemistry. Spectroscopic data indicate that pyr3pi exists in its zwitterionic form even in low polarity solvents with electronic absorption spectra showing a hypsochromic shift with an increase in solvent polarity and NMR experiments indicating an increasingly zwitterionic structure in chloroform as the temperature is lowered. Raman spectra in increasingly polar solvents show small variations of the structure that are consistent with a change toward a structure with more zwitterionic character. However, comparison of the calculated and experimental vibrational energies and intensities and comparison of NMR coupling constants with calculated bond order indicate that calculations underestimate the amount of charge separation seen in low polarity solvents. Although for this system density functional theory (DFT) calculations and the two-state model qualitatively reproduce negative solvatochromism, they fail to reproduce the trends in hyperpolarizability seen experimentally. This is attributed to solvent field DFT calculations underestimating the degree of charge separation in reaction fields representing low polarity solvents.

2-{[(Biphenyl-2-yl)diazen-yl]methyl-idene}-1,3,3-trimethyl-indoline.

The title mol-ecule, C(24)H(23)N(3), shows some delocalization of charge based on the small [8.0 (2)°] angle between the indolin-2-yl-idene ring system and the link methyl-diazene C(2)N(2) atom plane. A further twist of 17.2 (3)° is subtended between the C(2)N(2) plane and its attached benzene ring. The dihedral angle between the biphenyl rings is 47.96(14)°. In the crystal, the mol-ecules pack via C-H⋯π attractive inter-actions.

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

The title mol-ecule, C(23)H(31)NO, has two alternative cyclo-hexa-none 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-yl-idene subtends an angle of 2.19 (7)° with its fused aromatic ring, an angle of 16.24 (8)° with the plane of the major cyclo-hexa-none configuration and an angle of 8.54 (15)° with the bridging planar ethyl-idene C atoms. These last atoms subtend an angle of 8.37 (16)° with the mean plane through the major cyclo-hexa-none configuration. The mol-ecules pack approximately parallel to the ([Formula: see text]01) plane via C-H⋯π and C-H⋯O inter-actions.

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.

2-(3-Cyano-4-{7-[1-(2-hy-droxy-eth-yl)-3,3-dimethyl-indolin-2-yl-idene]hepta-1,3,5-trien-yl}-5,5-dimethyl-2,5-dihydro-furan-2-yl-idene)malononitrile.

The title compound, C(29)H(28)N(4)O(2), excluding the hydroxyethyl and methyl groups, is slightly twisted from planarity so that the terminating indol-2-yl-idene and furan-2-yl-idene moiety planes subtend a dihedral angle of 6.27 (8)°. A small inwards fold in the polymethine atom chain is consistent with centrosymmetric dimer formation via O-H⋯N(cyano) hydrogen bonds. In the crystal, the mol-ecules pack in layers approximately parallel to the (10[Formula: see text]) plane via pairs of O-H⋯N and C-H⋯N(cyano) inter-actions.

C-H⋯π packing inter-actions in 2-[5,5-bis-(4-benzyl-oxyphen-yl)-3-cyano-4-methyl-2,5-dihydro-furan-2-yl-idene]malononitrile.

The title mol-ecule, C(35)H(25)N(3)O(3), packs utilizing C-H⋯π attractive inter-actions causing the identical 4-benzyl-oxyphenyl groups to pack with different conformational angles. This difference is consistent with the variable inter-planar dihedral angles found in closely related structures.

5-(4-Cyano-5-dicyano-methyl-ene-2,2-dimethyl-2,5-dihydro-3-fur-yl)-3-(1-methyl-1,4-dihydro-pyridin-4-yl-idene)pent-4-enyl 3,5-bis-(benz-yloxy)benzoate acetonitrile 0.25-solvate: a synchrotron radiation study.

The title compound, C(42)H(36)N(4)O(5)·0.25CH(3)CN, crystallizes with a partial twofold disordered (1/4) acetonitrile solvent of crystallization. The linking atoms to the 3,5-bis-(benz-yloxy)benzoic acid are disordered between two conformations in the ratio 0.780 (6):0.220 (6). In the crystal, the mol-ecules pack using mainly C-H⋯N(cyano) inter-actions coupled with weak C-H⋯O(ether) inter-actions and C-H⋯π inter-actions. A brief comparison is made between a conventional and this synchrotron data collection.

2-(4-{3-[1-(3-Bromo-prop-yl)-3,3-dimethyl-2,3-dihydro-1H-indol-2-yl-idene]prop-1-en-yl}-3-cyano-5,5-dimethyl-2,5-dihydro-furan-2-yl-idene)malononitrile.

The backbone of the title mol-ecule, C(26)H(25)BrN(4)O, is approximately planar: the dihedral angle between the planes of the indoline ring system and the furan ring is 7.68 (14)°. In the crystal, layers lying parallel to (10) occur, with the mol-ecules inter-acting via weak C-H⋯N(cyano) and C-H⋯Br bonds and short N(cyano)⋯Br contacts [3.345 (4) Å].

Geometry and bond-length alternation in nonlinear optical materials. III. Structural parameters of two chromophores containing aromatizable donorsPart II: Gainsford, Bhuiyan & Kay (2008a).

The planar component of 2-{3-cyano-4-[3-(1-decyl-1,4-dihydroquinolin-4-ylidene)prop-1-enyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}malononitrile, C(32)H(46)N(4)O, (I), forms into layers parallel to the (\overline{1}01) plane. The larger of the two spaces between layers is filled by the alkyl chains, giving a ;sandwich stack' appearance. The packing of 2-{3-cyano-4-[5-(1-decyl-1,4-dihydroquinolin-4-ylidene)penta-1,3-dienyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}malononitrile, C(34)H(38)N(4)O, (II), which has partial disorder in the 1-decyl group, utilizes weak C-H...N, C-H...O and C-N...pi interactions in a three-dimensional ;herring-bone' array with molecular segments parallel to the (111) and (\overline{1}1\overline{1}) planes. Different rotational isomers with respect to the polyene chain and the 5,5-dimethyl-2,5-dihydrofuran-2-ylidene link are observed in the two structures. The significance of the study lies in the delocalization of charge along the polyene chain and the supramolecular aggregation present, which highlight the difficulty in obtaining the noncentrosymmetric alignment required for high nonlinear optical (NLO) responses in zwitterionic chromophores.