Novel, Highly Nonlinear Optical Molecular Crystals Based on Multidonor-Substituted 4-Nitrophenylhydrazones

Abstract

than to the quantity of active materials. Further device optimization based on such models is under way. ExperimentalPolymer Synthesis: The synthetic path to poly(3-(4¢-(1²,4²),7²-trioxaoctyl)phenyl)thiophene) (PEOPT) is described in Scheme 1. Treatment of p-bromophenol with 1-chloro-2-(2-methoxyethoxy)ethane afforded compound 1, which on Pd(0) catalyzed coupling [6] with 3-thiopheneboronic acid [7] gave 2 as a dark crystalline solid. After passing the crude product dissolved in CH 2 Cl 2 through a short column of silica gel and subsequent recrystallization from MeOH, the monomer (2) was obtained as a pure white crystalline solid (m.p. = 76.1±76.9 C). The polymerization of 2 was performed by slow addition of a slurry of FeCl 3 in CHCl 3 to a solution of the monomer in CHCl 3 at room temperature [8]. The ratio of monomer/FeCl 3 used was 1:6. PEOPT was obtained as a dark solid after precipitation from methanol. The polymer was carefully dedoped and the lower molecular weight and irregular compounds were removed by Soxhlet extraction with methanol and diethyl ether [6]. Size exclusion chromatography (SEC) of the polymer dissolved in tetrahydrofuran (THF) resulted in a molecular weight M n = 20 000 and M w = 56 000 relative to polystyrene standards. The 1 H NMR spectrum of PEOPT was used to estimate the head-to-tail density, which was found to be >85 %. The CHCl 3 solution of the polymer was deep red, while it became darker upon evaporating the solvent. The UV-vis. spectrum of a spin-cast film of the polymer on glass showed an absorption maximum at 476 nm. Annealing of this film with heat or CHCl 3 vapors at room temperature resulted in a change of color accompanied by a red shift of the absorption maximum to 552 nm.

Acentric Nonlinear Optical 2,4-Dihydroxyl Hydrazone Isomorphic Crystals with Large Linear, Nonlinear Optical Susceptibilities and Hyperpolarizability

“…8−10 The phenolic OH groups linked directly to the π-conjugated bridge can also act as hydrogen bond donor and acceptor sites, and simultaneously as an electron donor. 11,12 As a consequence the existing of OH groups may be influence both microscopic and macroscopic physical properties. 10 The introduction of molecular asymmetry or chirality, is a most often employed strategy to achieve noncentrosymmetric packing.…”

Gas-Induced Ion-Free Stable Radical Anion Formation of Organic Semiconducting Solids as Highly Gas-Selective Probes

“…Although the electron-withdrawing ability of EWG1–EWG4 is lesser than that of classical EWGs, EWG1–EWG4 can exhibit a non-negligible electron withdrawing ability. Because non-π-conjugated (or partially π-conjugated) linker between two π-conjugated bridges influence the electronic states − and introduction of highly electronegative groups on phenyl rings results in increasing positive quadrupole moment of the phenyl ring (i.e., increasing the electron-withdrawing ability). Furthermore, whole NDI–EWGs in this work exhibit SRAF behavior opposite to NDI-C6.…”

Supramolecular Ordered Organic Thin Films for Nonlinear Optical and Optoelectronic Applications

“…Therefore, molecular engineering for the optimization of microscopic optical properties and for non-centrosymmetric packing is a vital step prior to growth. Approaches, such as the use of molecular asymmetry, [35,36] non-rod-shaped p-conjugated cores, [10,37] strong Coulomb interactions, [38] and directional intermolecular interactions (e.g., hydrogen bonds), [39] have led to many successful developments of various acentric molecular dipole alignments. Furthermore, high optical quality, good thermal and chemical stability, and high optical-damage threshold are desired.…”

“…[39] The thin films are based on a hydrazone derivative named 5-bromo-5′-formyl-2,2′-bithiophene-4-nitrophenyl hydrazone (BITINPH), which is similar to other hydrazone derivatives developed for secondorder nonlinear optics. [10,37] The structure is shown in Figure 3b. The molecule is designed with two hydrogen-bonding sites, which we believe to be involved in the out-of-plane ordering mechanism.…”