Thiophene Chromophores Research Articles

Thiophene‐cored 2,2‐bis(methylol)propionic acid dendrimers for optical‐power‐limiting applications

AbstractThe synthesis and characterization of dendron‐coated 2,5‐bis(phenylethynyl)thiophene chromophores are described. The dendrimers were grown divergently on the arylthiophene core with the versatile anhydride of 2,2‐bis(methylol)propionic acid. The arylthiophene core was synthesized with Sonogashira coupling reactions. Structurally well‐defined dendrimers up to the fourth generation were grown, as confirmed by size exclusion chromatography, NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight analysis. The different dendritic substitution did not influence the absorption spectra of the compounds in or near the visible region. Solutions of arylthiophenes had good transparency at wavelengths greater than 400 nm. The dendritic thiophenes exhibited an optical‐power limit at the laser wavelength of 532 nm. However, the magnitude of the optical‐power limit of these compounds was slightly lower than that of a nondendritic arylthiophene with n‐pentyl substituents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1177–1187, 2005

Synthesis and second order nonlinear optical properties of new chromophores containing 1,3,4-oxadiazole and thiophene rings

We report the synthesis and physico-chemical characterization, including molecular second order nonlinear optical properties by the EFISH technique, of three new heterocycle based push–pull chromophores. Two chromophores contain the five membered 1,3,4-oxadiazole ring, the third a thiophene ring. The chromophores also contain azo or stilbene bridges between conjugated aromatic rings and are functionalized for covalent incorporation into polymer chains. The maximum observed μgβ is 1350 × 10−48 esu for the thiophene chromophore in conditions far from resonance enhancement (fundamental laser wavelength 1.907 µm). The crystal structure of one oxadiazole chromophore is also discussed.

Synthesis of polymers with isolated thiophene-arylidene-thiophene chromophores for enhanced and specific electron/hole transport

The synthesis of nine new polymers intended for future use in light-emitting diodes is described. The polymers consist of alternating units of thiophene–arylidene–thiophene chromophores and saturated silicon-containing spacers. The arylidene moieties include benzene-1,4-, 2,5-dimethoxybenzene-1,4-, naphthalene-1,4-, anthracene-9,10-, pyridine-2,5-, pyridine-2,6-, N-methylcarbazole-3,6-, 1,3,4-oxadiazole-2,5-, and 4,4′-dimethyl-2,2′-bithiazole-5,5′-. The syntheses involved dibromination of the central arene followed by Suzuki or Kumada cross-coupling reactions with two thiophene units. Subsequent dilithiation and reaction with dihalosilylalkanes provided the polymers. Their optical properties, including ultraviolet–visible absorption and emission in solution, were comparable to those of the parent monomer units, and they possessed the physical characteristics of macromolecules. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 872–879, 2001

Nonlinear optical polymers with novel benzoxazole chromophores: V. Linear and crosslinked polyurethanes using nitrothiophene and nitrophenol as electron acceptors

We synthesized two new diol monomers with benzoxazole-based nonlinear optical (NLO) chromophores, one of which has an additional hydroxyl group as a crosslinkable moiety and the other has a nitrothiophene group as an electron withdrawing unit. The diol monomers were polymerized with 4,4′-methylenebis(phenyl isocyanate) to give NLO polyurethanes, respectively. Linear polyurethane with hydroxyl groups could be crosslinked between side chain chromophores themselves after poling using an additional crosslinking agent such as teramethyl-1,3-xylylene diisocyanate. Temporal stability of electro-optic coefficient of a crosslinked polyurethane was improved compared with that of a linear polyurethane. The second harmonic generation coefficient of linear polyurethane with benzoxazole–thiophene chromophores was 94 pm V −1 (1.064 μm) and nonresonant d 33 value was 17.1 pm V −1 calculated by two-level model equation.

Heteroaromatic Chromophore Functionalized Epoxy-Based Nonlinear Optical Polymers

A series of epoxy-based second-order nonlinear optical (NLO) polymers containing heteroaromatic chromophores have been designed. Precursor polymers were prepared from the polymerization between the diglycidyl ether of Bisphenol A and aniline or 4-(2-thienyl)aniline. The precursor polymers were postfunctionalized by an azo-coupling reaction as well as tricyanovinylation to form a series of NLO polymers containing heteroaromatic chromophores. We have extended and established the versatility of our earlier reported postmodification strategy to include various heteroaromatic chromophores in the polymers at the final stage of synthesis. The correlation between different heteroaromatic chromophore structures and the NLO properties of the polymers was extensively studied during this work. Polymers containing heteroaromatic chromophores exhibit improved temporal stability and enhanced NLO activity. The d33 value of 80 pm/V at 1.550 μm was observed for a representative polymer of the class containing 2-(4-aminophenyl)−(5-tricyanovinyl)thiophene chromophores. NLO properties of the poled polymers exhibit long-term stability at 80 °C.

Distamycin‐NA: A DNA Analog with an Aromatic Heterocyclic Polyamide Backbone. Part 1. Synthesis and structural analysis of monomers and dimers containing the nucleobase uracil

AbstractThe synthesis of the monomeric building block 13 and its constitutional isomer 12 of a new type of DNA analog, distamycin‐NA, is presented (Schemes 1 and 2). This building block consists of a uracil base attached to a thiophene core unit via a biaryl‐like axis. Next to the biaryl‐like axis on the thiophene chromophore, a carboxy and an amino substituent are located allowing for oligomerization via peptide coupling. The proof of constitution and the conformational preferences about the biaryl‐like axis were established by means of X‐ray analyses of the corresponding nitro derivatives 10 and 11. Thus, the uracil bases are propeller‐twisted relative to the thiophene core, and bidentate H‐bonds occur between two uracil bases in the crystals. The two amino‐acid building blocks 12 and 13 were coupled to give the dimers 15 and 16 using dicyclohexylcarbodiimide (DCC) in THF/LiCl and DMF, respectively. While the dimer 15 showed no atropisomerism on the NMR time scale at room temperature, its isomer 16 occurred as distinct diastereoisomers due to the hindered rotation around its biaryl‐like axis. Variable‐temperature 1H‐NMR experiments allowed to determine a rotational barrier of 19 ± 1 kcal/mol in 16. The experimental data were complemented by AM1 calculations.

ChemInform Abstract: Synthesis of Sulfone‐Substituted Thiophene Chromophores for Second‐ Order Nonlinear Optics.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of sulfone-substituted thiophene chromophores for second-order nonlinear optics

A new series of conjugated thiophene compounds 1–4 containing methylsulfonyl and phenylsulfonyl acceptors have been synthesized which possess efficient second-order optical nonlinearities, high thermal stability and good transparency for use as nonlinear optical materials.

Intramolecular spin-interactions between two nitronyl nitroxide or imino nitroxide radical units linked to thieno[2,3- b]thiophene and thieno[2,3- b]thieno[3′,2′- d]thiophene chromophores

Diradical species 1N, 1I, 2N, and 2I, in which two nitronyl nitroxide ( N) or imino nitroxide ( I) radical centers are attached to thieno[2,3- b]thiophene ( 1) and thieno[2,3- b]thieno[3′,2′- d]thiophene ( 2) chromophores, respectively, were prepared and their intramolecular exchange interactions were investigated in frozen solutions by means of ESR spectroscopy and magnetic susceptibility measurements at cryogenic temperature. Temperature dependence of the ESR signal intensities due to the triplet state revealed that bis(nitronyl nitroxide) radicals, 1N and 2N, are ground-state singlet species with quite small singlet-triplet gaps. In bis(imino nitroxide) radical 1I the spin interaction was antiferromagnetic and the singlet-triplet gap was estimated to be 2J k B =−18 K . On the other hand, bis(imino nitroxide) 2I was revealed to be a singlet-triplet degenerate species. These results are discussed in terms of the intramolecular NO---S contact along with corroboration by the semi-empirical MO calculations.