Organic Nonlinear Optical Crystals Based on Configurationally Locked Polyene for Melt Growth

Abstract

A series of nonlinear optical chromophores based on configurationally locked polyene are synthesized, and the single crystal growth from the melt are investigated. The chromophores consist of a π-conjugated hexatriene bridge between the dialkylamino or methoxy electron donors and the dicyanomethylidene electron acceptor. The physical and nonlinear optical properties and the single crystal X-ray structures of these chromophores are characterized. Specifically, the chromophore 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) exhibits a strong powder second-harmonic generation signal of about 2 orders of magnitude greater than that of urea and a large temperature difference of 80 °C between the melting temperature and the recrystallization temperature. Finally, we demonstrate the growth of single crystalline thin films of DAT2 by a Bridgman-type melt growth technique, which gives a new direction for organic nonlinear optical crystal engineering using melt-growth techniques.

Organic Electro‐optic Single‐ Crystalline Thin Films Grown Directly on Modified Amorphous Substrates

“…This indicates that the crystals grown on the substrate have good optical surfaces and are free from scattering centers. Comparing the UV-vis/IR transmission along the two main axes of the DAT2 crystals grown on the substrate and bulk plate-like crystals [10] we can conclude that the largest crystal face is in both cases the c-face. Therefore, the crystal preferentially grows normal to the crystallographic c-face, which is due to the supramolecular interactions between the CN groups on the modified surface and the c-face of crystals, as illustrated in Figure 1b.…”

“…A series of acentric configurationally locked polyene (CLP) crystals has been developed recently with large macroscopic nonlinearity and high thermal stability. [10,11] For the growth of thin films on the substrates we choose one of the chromophores 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2, see Fig. 1a) due to a noncentrosymmetric crystal structure (monoclinic P2 1 space group) [12] that leads to large macroscopic nonlinearities.…”

“…1a) due to a noncentrosymmetric crystal structure (monoclinic P2 1 space group) [12] that leads to large macroscopic nonlinearities. [10] The main supramolecular interactions of DAT2 crystals are weak hydrogen bonds of C≡N···H-C with distances in the range of 2.8-3.4 Å. The C-H groups on the equatorial and axial methyl groups in the hexatriene bridge and one of methyl groups on dimethylamino group act as hydrogen bond donors.…”

Theory-Guided Design of Organic Electro-Optic Materials and Devices

“…Materials can also be prepared by sequential synthesis/self-assembly techniques and by crystal growth including from solution, the melt and the vapor phase [97][98][99][100][101][102][103][104][105][106][107]; however, these approaches have not been as widely adapted to the fabrication of prototype devices as have electric field poling methods.…”

Novel organic material with potential NLO application - electronic and spectroscopic properties

“…Differences between the values for our structure and those for 2-(3-(2-(4-dimethylaminophenyl) v i n y l ) -5 , 5 -d i m e t h y l c y c l o h e x -2 -e n y l i d e n e ) malononitrile (CCDC YEPRIV and YEPQUG [31,32]), 2-(3-(2-(4-dimethylaminonaphthyl)vinyl)-5,5-dimethylcyclohex-2-enylidene)malonitrile (CCDC HEPJIW [33]) and 2-(3-(2-(4-diethylaminophenyl)vinyl)-5,5-dimethylcyclohex-2-enylidene)malonitrile (CCDC HEPJAO [33]) are less then 0.021 Å and 2. (3) o .…”