Chiral optical films based on achiral chromophore guests

Films constituted by an achiral host polymer and an achiral guest chromophore, which exhibit intense chiral optical responses for both host and guest peaks in the infrared as well as in the UV-visible regions, have been obtained. Such films can have any thickness from the nanoscale up to the macroscopic scale. This unexpected chiral optical behavior is easily achieved by crystallization of a robust commercial stereoregular host polymer (syndiotactic polystyrene, s-PS) from the amorphous phase as induced by a nonracemic guest, followed by exchange of the nonracemic guest with the achiral guest, leading to the formation of polymer-host/chromophore-guest cocrystalline phases. This finding opens the possibility to achieve s-PS-based films with chiral optical response at selected wavelengths. It has been also found that the chiral optical cocrystalline phase of s-PS with azulene exhibits a monoclinic δ-clathrate form with equal proportions of left- and right-handed helices. This confirms that the observed chiral optical behavior arises by the nonracemic native morphology of the crystalline regions, which has been induced by the temporary nonracemic guest.     

The amide-aromatic-ring system : An inherently dissymmetric chromophore

Two cyclic peptide like compounds, cyclo-anthranoyl-L- prolyl (1) and cyclo-homoanthranoyl-L-prolyl (2) have been synthesized and investigated by UV spectroscopy and measurement of circular dichroism. Compound 1 of entirely rigid conformation with two N-CO groups conjugated to the aromatic ring, Ar-NH-CO left handed helical, Ar-CO-N right handed helical, shows a very strong positive Cotton effect centered around 250 nm and a strong negative one centered around 227 nm. Compound 2, which has only one conjugated skewed electron system, Ar-NH-CO, can exist in two different stable conformations, one of them being left handed, the other one right handed helical. It also shows a strong positive Cotton effect centered around 235 nm. Since from earlier ¹³C NMR data the latter was concluded to be the preferred conformation, a right handed helical sense of the amide bond-aromatic ring system is likely to correlate with a positive Cotton effect of this inherently dissymmetric chromophore.     

Optical properties of inherently dissymmetric polyamides

A study of the optical rotatory dispersion (ORD), circular dichroism (CD), and ultraviolet spectra (UV) of polyamides derived from optically active biphenyl acid chlorides, and aromatic, and aliphatic diamines, was made. The optically active monomers were (–)-(S)-2,2′-dinitro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride and (–)-(S)-2,2′-dichloro-6,6′-dimethylbiphenyl-4,4′-dicarbonyl chloride. The diamines were o-, m-, and p-phenylenediamine, piperazine, trans-2,5-dimethylpiperazine, and 1,2-pyrazolidine. The ORD spectra of the o-phenylenediaminepolyamide taken in different solvents indicated the existence of some ordered structure in the least polar solvent. All other polyamides existed in a random coil conformation in the solvents employed.     

Synthesis and nonlinear optical properties of hyperbranched polytriazole containing second‐order nonlinear optical chromophore

The hyperbranched polytriazole (hb‐PTA) containing second‐order nonlinear optical chromophore was synthesized through “A₂ + B₃” approach based on “click reaction.” Its corresponding linear analogue (l‐PTA) was prepared for comparison. The hb‐PTA has better solubility in common organic solvents than the l‐PTA. Both the polymers exhibit good thermal stability with 5% weight loss temperatures over 260 °C. The poled film of hb‐PTA exhibits much higher second‐harmonic coefficient (96.8 pm/V) than that of l‐PTA (23.5 pm/V). The three‐dimensional spatial isolation effect resulting from the highly branched structure and the crosslinking of the terminal acetylene groups at moderate temperature play important roles in the enhancement of optical nonlinearity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1140–1148, 2008     

Synthesis and optical properties of copolymers of 4-aminostyrene with the side styrylquinoline chromophore groups

Successive molecular assembling in polymer chains furnished a series of the comb-shaped copolymers of 4-aminostyrene containing side styrylquinoline chromophore groups. Thermal, thermomechanical, spectroscopic, and luminescent properties of the polymers and low-molecular-weight model chromophores were studied.     

Fluoride-selective optical sensor based on the dipyrrolyl-tetrathiafulvalene chromophore

A chemosensor bearing dipyrrolyl motifs as recognition sites and a tetrathiafulvalene redox tag has been evaluated as an optical and redox sensor for a series of anions (F(-), Cl(-), Br(-), HSO(4)(-), CH(3)COO(-), and H(2)PO(4)(-)) in DCM solution. The receptor shows specific optical signaling for fluoride but little electrochemical effect in solution. The solid-state performance of the sensor leads to measurable changes in water. Design implications towards better systems based on these results and other examples are discussed.     

Electrically-driven chiroptical switches based on axially dissymmetric 1,1'-binaphthyl and electrochromic viologens: synthesis and optical properties

A novel redox type of chiral molecular switch based on axially dissymmetric 1,1'-binaphthyl and electrochromic 4,4'-bipyridinium exhibits drastic changes in absorption and circular dichroism spectra upon electrochemical redox reaction and is fully characterized for the electrically driven chiroptical switching properties.     

Chiral imides as potential chiroptical switches: synthesis and optical properties

A series of chiral aromatic imides and diimides were synthesized and their electrochemical, absorption, fluorescent, and chiroptical properties were examined for their potential application as molecular chiroptical switches. These compounds exhibit strong UV-vis absorptions, and can be electrochemically reduced to radical anions that absorb in the near infrared (NIR) region. Further reduction to the dianionic states results in new absorptions in the visible region. The changes in circular dichroism upon redox switching were apparent in the UV-vis region but were absent in the NIR region.     

Synthesis of novel Y-type polyurethane containing azomethine moiety, as non-linear optical chromophore and their properties

3,4-Di-(2′-hydroxyethoxy)-4′-nitrobenzylidene II was prepared by condensation reaction of 3,4-dihydroxy-4′-nitrobenzylidene I with 1-chloro-2-ethanol. Monomer II was reacted with p-phenylene diisocyanate to yield polyurethane containing the non-linear optical chromophore 3,4-di-(2′-hydroxyethoxy)-4′-nitrobenzylidene. Polymer III shows thermal stability up to 300 °C in TGA thermogram. T_g value of the polymer obtained from DSC thermogram was 110 °C. The resulting polyurethane III was soluble in common organic solvents such as acetone, DMF and DMSO. The values of electro optic coefficient d₃₃ and d₃₁ of the poled polymer film were 3.15 × 10 ⁻⁷ and 1.5 × 10 ⁻⁷ esu, respectively.     

Chiroptical properties of the nonplanar amide chromophore in n-acylaziridines

The optically active 1-acyl-substituted (1R,2R)-2-methyl- and (1R,2S)-2-methoxycarbonylaziridines were synthesized. The nonplanarity of the amide chromophore in them and its high conformational mobility, which was caused by the rotation around the N-C(O) bond, were shown on the basis of the investigation of the CD spectra and the calculations of simple models by the MNDO method. The possible correlation of the sign of the Cotton effect of the long-wave p-* transition with the intrinsic chirality of the chromophore was studied.Communication 64 in the series Asymmetric Nitrogen, for Communication 63, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 41–47, January, 1989.     

Interpolymeric complexes of polyoctamethyleneacetamidine with polyethers terminally modifi ed with chromophore groups and their nonlinear optical properties

Ionic interpolymeric complexes of polyoctamethyleneacetamidine with polyethers terminally modifi ed with 4-[5-(4-hydroxyphenyl)-3-oxopenta-1,4-dienyl]benzoyl (chromophore) groups were prepared. The complexes exhibit third-order nonlinear optical properties. Factors affecting the third-harmonic generation effi ciency were revealed.     

A tentative new approach to the optical activity of substituted benzene chromophore

The influence of environmental asymmetry and achiral substitution pattern on the electric and magnetic moments of ¹L_b, and ¹L_a benzenoid transitions is analyzed on the basis of a simple qualitative model.Absolute configurations of chiral benzenoid derivatives may be predicted, if the achiral substitution pattern and the spectroscopic moments associated with each substituent are known.Accurate spectroscopic moments derived from linear dischroic measurements are employed in the CD analysis of some representative rigid polycyclic natural compounds.     

Synthesis and properties of novel polyurethanes containing 3,4‐dioxybenzylidenecyanoacetate group as a nonlinear optical chromophore

Methyl 3,4‐di‐(2′‐hydroxyethoxy)benzylidenecyanoacetate ( 3 ) was prepared by hydrolysis of methyl 3,4‐di‐(2′‐vinyloxyethoxy)benzylidenecyanoacetate ( 2 ). Diol 3 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate, and 1,6‐hexamethylenediisocyanate to yield polyurethanes 4 – 6 containing the nonlinear optical chromophore 3,4‐dioxybenzylidenecyanoacetate. The resulting polyurethanes 4 – 6 were soluble in common organic solvents such as acetone and dimethylformamide. Polymers 4 – 6 indicated thermal stability up to 300 °C in thermogravimetric thermograms with glass‐transition temperature values obtained from differential scanning calorimetric thermograms in the range of 78–102 °C. The second‐harmonic generation coefficients (d₃₃) of the poled polymer films were around 6.9 × 10^?9 esu. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1742–1748, 2002     

Synthesis of nonlinear optical chromophore and the preparation of attenuated total reflectance modulator

A new nonlinear optical chromophore with strong electron‐withdrawing acceptor and rigid–flexible dendron was synthesized. An electro‐optic (EO) attenuated total reflectance modulator was prepared to measure the EO coefficient of the films. Modification of the tricyanopyrroline chromophore with rigid–flexible dendron group provided reduction of dipole–dipole interactions and improvement of its solubility. As the chromophore loading increased, there was a great improvement on the macroscopic EO response of the polymeric materials obtained by incorporating this chromophore as a guest in amorphous polycarbonate. The largest EO coefficient was 42 pm/V at 1310 nm. Copyright © 2011 John Wiley & Sons, Ltd.     

Two-photon absorption and effective broadband optical power limiting properties of a multi-branched chromophore containing 2,3-diarylquinoxalinyl moieties as the electron-pulling units

A novel multi-branched chromophore containing 2,3-diarylquinoxalinyl units as the electron-acceptors had been synthesized and its nonlinear optical properties were characterized in the femtosecond and nanosecond regime. The experimental results show that the studied fluorophore possesses strong and wide-dispersed two-photon absorption in near infrared (NIR) region. It is demonstrated that the incorporation of 2,3-disubstituted quinoxaline moieties as a part of π-conjugation in a dye molecule could be a useful approach toward large molecular two-photon absoptivities within the studied spectral region. Effective optical-power-attenuation behaviors in the nanosecond time domain of this compound were also investigated and the results indicate that such dye molecule can be a potential material as a broadband and quick-responsive optical limiter especially when against those laser lights with longer pulses.     

Charge transfer interactions and nonlinear optical properties of push–pull chromophore benzaldehyde phenylhydrazone: A vibrational approach

FT Raman and IR spectra of the crystallized nonlinear optic (NLO) molecule, benzaldehyde phenylhydrazone (BPH) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies of BPH have been investigated with the help of B3LYP density functional theory (DFT) method. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). From the optimized geometry, the decrease in C–N bond length indicates the electron delocalization over the region of the molecule. The vibrational analysis confirm the charge transfer interaction between the phenyl rings through CN–N skeleton.     

Synthesis of novel nonlinear optical chromophore to achieve ultrahigh electro-optic activity

A new diene-conjugated chromophore WJ1 was synthesized with high yield of 36% through an H-bonding induced Vilsmeier reaction. By simple guest-host doping, a large electro-optic efficiency of 337 pm V(-1) at 1310 nm and excellent temporal stability at 75 °C have been achieved in poled films of WJ1/APC with a high loading density of 40 wt%.     

Chiroptical properties and absolute configurations of the hypericin chromophore propeller enantiomers

Summary The diastereomericmono- andbis--appended (R)-menthyl hypericin derivatives were studied by means of absorption spectroscopy, circular dichroism measurements, application of the C₂ rule, and semiempirical calculations. This allowed us to assign the absolute configuration (P) to the inherently chiral phenanthroperylene quinone chromophore of hypericin, thebay-hypericinate ion, and the 1,6-dioxo-tautomer displaying a negativeCotton effect of their long wavelength absorption band. From these results and according to the positive chiroptical sign of their long wavelength bands, the absolute configuration (M) could be assigned to the stentorin chromophore in the native pigments.

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Chiroptische Eigenschaften und Absolutkonfiguration der Propellerenantiomeren des Hypericinchromophors

Zusammenfassung Die diastereomerenmono- undbis--substituierten (R)-Menthyl-hypericinderivative wurden mit Hilfe der Absorptionsspektroskopie, von Circulardichroismusmessungen, der Anwendung der C₂-Regel und semiempirischer Rechnungen untersucht. Dies erlaubte die Zuordnung der absoluten Konfiguration (P) für den inhärent chiralen Phenanthroperylenchinon-Chromophor von Hypericin, dasbay-Hypericination und das 1,6-Dioxotautomer, die einen negativenCotton-Effekt ihrer langwelligen Absorptionsbande aufweisen. Auf der Basis dieser Ergebnisse und aufgrund des positiven chiroptischen Signals seiner langwelligen Absorptionsbande wurde dem Stentorinchromophor in den nativen Pigmenten die absolute Konfiguration (M) zugeordnet.

     

Adsorption and thermodynamic properties of dissymmetric gemini imidazolium surfactants with different spacer length

A series of dissymmetric gemini imidazolium surfactants with different spacer length ([C_mC_sC_nim]Br₂, m + n = 24, m = 12, 14, 16, 18; s = 2, 4, 6) were synthesized and characterized by ¹H NMR and ESI-MS spectroscopy. Their adsorption and thermodynamic properties were investigated by the surface tension and electrical conductivity methods. Consequently, the surface activity parameters (cmc, γ_cmc, π_cmc, pC₂₀, cmc/C₂₀, Γ_max, A_min) and thermodynamic parameters (ΔG_m^θ, ΔH_m^θ, ΔS_m^θ) were obtained. The effects of the dissymmetry (m/n) and the spacer length (s) on the surface activity and micellization process of surfactants have been discussed in detail.