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Chiroptical Properties (chiroptical + property)
Selected AbstractsStructures and Chiroptical Properties of Thermoresponsive Block Copolymers Containing L -Proline MoietiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2007Hideharu Mori Abstract Amino acid-based block copolymers containing poly(A-Pro-OMe) have been synthesized by RAFT polymerization using the dithioester-terminated poly(DMA) as a macro-CTA. An amphiphilic block copolymer composed of polystyrene as a hydrophobic segment and poly(A-Pro-OMe) as a hydrophilic segment was also prepared using polystyrene as the macro-CTA. The chiroptical properties of the block copolymer, poly(DMA)- block -poly(A-Pro-OMe), was evaluated by specific rotation, CD, and UV-vis spectroscopy. The assembled structure of the block copolymer on a mica surface was characterized by SFM. Thermally induced phase separations of the random and block copolymers were also studied in aqueous solution. [source] Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2004Andrea Pucci Abstract Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed. Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles ,. [source] Metallahelicenes: Easily Accessible Helicene Derivatives with Large and Tunable Chiroptical Properties,ANGEWANDTE CHEMIE, Issue 1 2010Lucie Norel Dr. Enantiomerenreine Metallahelicene wurden durch Cyclometallierung von 2-pyridylsubstituierten Benzophenanthrenen und anschließende Enantiomerentrennung durch HPLC an chiraler Phase erhalten. Sie sind bei Raumtemperatur rote Leuchtstoffe, und ihre chiroptischen Eigenschaften können durch Oxidation des Metallzentrums zur Oxidationsstufe IV moduliert werden. [source] New Functional Hexahelicenes , Synthesis, Chiroptical Properties, X-Ray Crystal Structures, and Comparative Data Bank Analysis of Hexahelicenes.CHEMINFORM, Issue 48 2003Claudia Wachsmann Abstract For Abstract see ChemInform Abstract in Full Text. [source] Multi-Input/Multi-Output Molecular Response System Based on the Dynamic Redox Behavior of 3,3,4,4-Tetraaryldihydro[5]helicene Derivatives: Reversible Formation/Destruction of Chiral Fluorophore and Modulation of Chiroptical Properties by Solvent PolarityCHEMISTRY - A EUROPEAN JOURNAL, Issue 37 2009Takanori Suzuki Prof. Abstract 3,3,4,4-Tetaaryldihydro[5]helicenes (1) and 1,1,-binaphthyl-2,2,-diylbis(diarylcarbenium)s (22+) can be reversibly interconverted upon electron transfer, which is accompanied by a vivid color change (electrochromism) as well as by the formation/cleavage of a CC bond ("dynamic redox behavior"). Because only the neutral donor 1 exhibits strong fluorescence, electrochemical input can further modify the fluorescent properties of the pair. Due to the configurational stability of the helicity in 1 and axial chirality in 22+, the redox reaction of optically pure material proceeds stereospecifically, which induces a chiroptical change such as circular dichroism (CD) as an additional output. The CD spectra of dications 22+ exhibit solvent dependency (chiro-solvatochromism), which is accompanied by solvatochromic behavior based on the ,,, interaction of the two cationic chromophores as well as coordinative interaction of the Lewis basic solvent to the Lewis acidic triarylcarbenium moieties. Thus, the present system is endowed with multi-input functionality for modifying multiple output signals. [source] Inherently Chiral Molecular Clips: Synthesis, Chiroptical Properties, and Application to Chiral DiscriminationCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2007Gaku Fukuhara Abstract Inherently chiral molecular clips (MCs), pseudoenantiomeric anti - 1 and anti - 2, as well as mesoid syn - 3, were synthesized by diastereodifferentiating repetitive Diels,Alder reactions of the achiral bisdienophile 6 with chiral diene 5 generated in situ from (,)-menthyl 3,4-bis(dibromomethyl)benzoate 4. These MCs were successfully separated by chiral HPLC to give optically active anti - 1 and anti - 2 and almost optically inactive syn - 3. The structures of anti - 1, anti - 2, and syn - 3 were assigned by high-resolution NMR and the absolute configurations of anti - 1 and anti - 2 were determined by the exciton-chirality method. Optically active anti - 2 can serve as a chiral host. It binds the HCl adduct of D -tryptophan methyl ester (D -TrpOMe,HCl) 3.5,times stronger than the L -enantiomer (KD/KL=3.5). [source] Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2004Andrea Pucci Abstract Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed. Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles ,. [source] Stabilizing effect of intramolecular lewis base toward racemization of optically active selenoxidesHETEROATOM CHEMISTRY, Issue 3 2007Takahiro Soma 2-(Methylchalcogenomethyl)diphenyl selenoxides 1 and 2-{2,-(N,N-dimethylamino)ethyl}phenyl alkyl (or aryl) selenoxides 2, which were expected to be stabilized toward racemization by intramolecular coordination, were synthesized and optically resolved into their enantiomers on an optically active column using high-performance liquid chromatography. Relationship between the absolute configurations and the chiroptical properties of the enantiomers was clarified by comparing with those of sulfur analogues. Stabilities toward racemization of optically active selenoxides 1a and 1b were nearly equal to that of 2-{(N,N-dimethylamino)methyl}diphenyl selenoxide and mesityl phenyl selenoxide. The rates of racemization for optically active selenoxides 2 were found to be faster than that of 2-{(N,N-dimethylamino)methyl}phenyl alkyl (or aryl) selenoxides. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:301,311, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20299 [source] Synthesis and chiroptical properties of ,-conjugated polymer consisting of dihydropentahelicene units with axial chiralityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2010Masahiro Abe Poly(dihydropentahelicene) or poly(1,1,-naphthalene- 4,4,-diyl) with axial chirality was prepared. The polymer showed a large circular dichroism of 1.8 degrees/,m in a cast film. [source] Synthesis and chiroptical properties of optically active poly(ethynylcarbazole) derivatives: Substituent effect on the helix formationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2007Fumio Sanda Abstract Novel chiral acetylene monomers containing carbazole, 2-ethynyl-9-[(S)-2-methylbutoxycarbonyl]carbazole (1), 3-ethynyl-9-[(S)-2-methylbutoxycarbonyl]carbazole (2), 2-ethynyl-9-[(S)-2-methylbutyl]carbazole (3), and 2-ethynyl-9-[(S)-4-methylhexyl]carbazole (4) were synthesized and polymerized with [(nbd)RhCl]2Et3N. The corresponding polyacetylenes with number-average molecular weights ranging from 68,700 to 310,000 were obtained in good yields. Poly(1) exhibited a large specific rotation and an intense Cotton effect in toluene, indicating that it formed a helix with predominantly one-handed screw sense, while the other three polymers showed no evidence for taking a helical structure. Poly(1) largely decreased the CD intensity upon heating from ,10 to 60 °C. Poly(1) showed a Cotton effect in film state in a manner similar to solution state. No chiral amplification was observed in the copolymerization of 1 with achiral 2-ethynyl-9- tert -butoxycarbonylcarbazole (5). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4450,4458, 2007 [source] Electrochemical polymerization of pyrrole in cholesteric liquid crystals: Morphology and optical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007Hiromasa Goto Abstract Electrochemical polymerization in a cholesteric liquid-crystal electrolyte was carried out. Polypyrrole thus synthesized in a cholesteric liquid-crystal electrolyte could be clearly seen to form a specific morphology. The polypyrrole films exhibited chiroptical properties and formed various surface structures such as Schlieren, Nazca-line, sea-anemone, and wire-loop structures. These structures that developed during polymerization were preserved even after washing. Moreover, no chiral molecule reacted chemically with the monomer during polymerization, and the electrolyte functioned only as a matrix chiral continuum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1377,1387, 2007. [source] Synthesis and chiroptical properties of L -valine-containing poly(phenylacetylene)s with (a)chiral pendant terminal groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006Lo Ming Lai Abstract Poly(phenylacetylene)s containing L -valine residues (P1) with (a)chiral pendant terminal groups R(*) [,(HCC{C6H4CONHCH[CH(CH3)2]COOR(*)})n,]; R(*) = 1-octyl (P1o), (1S,2R,5S)-(+)-menthyl [P1(+)], (1R,2S,5R)-(,)-menthyl [P1(,)] are designed and synthesized. The polymers are prepared by organorhodium catalysts in high yields (yield up to 88%) with high molecular weights (Mw up to ,6.4 × 105). Their structures and properties are characterized by NMR, IR, TGA, UV, and circular dichroism analyses. All the polymers are thermally fairly stable (Td , 320 °C). The chiral moieties induce the poly(phenylacetylene) chains to helically rotate in a preferred direction. The chirality of the pendant terminal groups affects little the helicity of the polymers but their bulkiness stabilizes the helical conformation against solvent perturbation. The backbone conjugation and chain helicity of the polymers can be modulated continuously and reversibly by acid. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2117,2129, 2006 [source] Photochromic and Photoresponsive Properties of Methacrylic Polymers Bearing Optically Active Hydroxysuccinimide in the Side ChainMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 21 2007Luigi Angiolini Abstract The photochromic and photoresponsive properties of a series of optically active azoaromatic polymers, containing in the side chain the rigid (S)- and/or (R)-hydroxysuccinimide residue, have been investigated in solution and in the solid state as thin films by observing the trans - cis photoisomerisation of the azobenzene chromophore, and the results are compared to the corresponding monomeric (S) and (R) model compounds. The presence of exciton splitting due to dipole-dipole interactions between the trans -azoaromatic rings in the CD spectra confirms the intrinsic chirality of the macromolecules. Thin films of the polymers display the same chiroptical properties as the solution, thus suggesting that the macromolecules maintain chiral conformations also in the solid amorphous state. [source] Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2004Andrea Pucci Abstract Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed. Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles ,. [source] Synthesis and chiroptical properties of liquid crystalline copolymers containing azobenzene chromophoresPOLYMER INTERNATIONAL, Issue 6 2007Zhi Zheng Abstract A series of new liquid crystalline copolymers, poly[((S)-2-methyl-1-butyl methacrylate)- co -(6-(4-(4-cyanophenylazo)phenoxy)hexyl methacrylate)], with different contents of chiral units of 17, 36, 54 and 78 mol% were synthesized. The structures and properties of the copolymers were characterized and evaluated using infrared, 1H NMR and UV spectroscopy, differential scanning calorimetry, gel permeation chromatography and circular dichroism (CD). The CD results suggested that absorptions of azobenzene chromophores were observed in films of copolymer containing 17, 36 or 54 mol% chiral units, but not in the film of copolymer containing 78 mol% chiral units. Also, CD values of the copolymeric films decreased with increasing chiral content. After irradiation with linear polarized light at 442 nm, CD values were changed in all the copolymeric films, and the CD values increased with decreasing chiral content in a nonlinear way, while the photoinduced change of chirality of the copolymers increased in a linear way with decreasing chiral content. The results are discussed in terms of interactions between structures and chiroptical properties. Copyright © 2007 Society of Chemical Industry [source] Synthesis and characterization of optically active star-shaped poly (N -phenylmaleimide)s with a calixarene corePOLYMER INTERNATIONAL, Issue 6 2007Liping Lou Abstract Two N -phenylmaleimide derivatives bearing a chiral oxazoline group, N -[o -(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(R)-PhOPMI] and N -[o -(4-isopropyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(S)-PriOPMI], were polymerized using in situ generated calixarene-based phenates as initiators to yield optically active polymers. The formation of star-shaped architectures was strongly dependent on both polymerization conditions and calixarene moieties. In the case of polymerization conducted in toluene at 80,100 °C, the arm-chain numbers achieved their respective maxima for the polymers with these multifunctional initiators. In contrast, the polymers obtained in polymerizations at lower temperature possessed fewer arm chains. The structure and chiroptical properties were investigated on the basis of 13C NMR, multiangular laser light scattering, gel permeation chromatography, and circular dichroism for the macromolecules with calixarene cores. Copyright © 2006 Society of Chemical Industry [source] Synthesis, chiroptical properties, and their theoretical simulation of some highly rotating benzotricamphor derivatives,,CHIRALITY, Issue 1E 2009Giuseppe Mazzeo Abstract The large molecules 1,3 (69, 90, and 102 atoms, respectively), prepared by cyclotrimerization of enantiomerically pure derivatives of (,)-bornyl acetate, show intense ECD spectra, high optical rotation (OR) values (200,1300, in absolute value) dominated in sign and order of magnitude by the lowest-energy Cotton effects, that is, they are the ideal candidates to test the reliability of our "approximate" (TDDFT/B3LYP/6-31G* or smaller basis set) approach to the calculation of chiroptical properties. As a matter of fact, a correct simulation of the OR values and ECD spectra of 1 and 2 can be obtained even using STO-3G basis set and semiempirical or molecular mechanics input geometries: for 1, at the TDDFT/B3LYP/STO-3G level, the OR values are of the order of 500,550, versus an experimental value ranging between 660 and 690, depending on the solvent. On the contrary, the case of 3 (exp. OR between ,1330 and ,1500) is really complex (for instance, the OR values range between ,3216 and ,729 (TDDFT/B3LYP/6-31G* calculations) or ,1824 and ,444 (TDDFT/B3LYP/STO-3G calculations)), making the comparison between calculated and experimental values more difficult. The behavior of 3 is due to its molecular flexibility, whereas 1 is a really rigid molecules and 2 behaves (vide infra) as it were a rigid system. These observations strongly indicate that the conformational freedom constitutes one of the major difficulties for a correct but simple simulation of the chiroptical properties. Chirality 21:E86,E97, 2009. © 2009 Wiley-Liss, Inc. [source] The effects of conformation and solvation on optical rotation: Substituted epoxides,CHIRALITY, Issue 3-4 2008Shaun M. Wilson Abstract The vapor-phase optical rotation (or circular birefringence) of (S)-1,2-epoxybutane, (S)-epichlorohydrin, and (S)-epifluorohydrin has been measured at the nonresonant excitation wavelengths of 355 nm and 633 nm by means of Cavity Ring-Down Polarimetry (CRDP). Complementary solution-phase studies were performed in a wide variety of dilute solvent media to highlight the pronounced influence of solute,solvent interactions. Density functional theory calculations of optical activity have been enlisted to unravel the structural and electronic provenance of experimental observations. Three stable, low-lying conformers have been identified and characterized for each of the targeted chiral species, with thermal (relative population weighted) averaging of their antagonistic chiroptical properties allowing specific rotation values to be predicted under both isolated and solvated conditions. For (S)-epichlorohydrin and (S)-epifluorohydrin, a self-consistent isodensity polarizable continuum model (SCI-PCM) has been exploited to gain further insight into the underlying nature of solvation effects. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source] Structure and chiroptical properties of supramolecular flower pigmentsCHIRALITY, Issue 2 2006George A. EllestadArticle first published online: 30 DEC 200 Abstract Research over the last 30 years has shown that at physiological concentrations of ca. 5 × 10,3 M, flower pigments composed of anthocyanins, either alone or complexed with flavone copigments, and frequently with metals, are self-assembled into non-covalent, chiral supramolecular complexes. This serves several biological functions including color stability, protection against UV radiation and provision for specific colors to attract insects for pollination. Self-association of the monomers takes place under conditions of molecular crowding by precise matching of the ,,, stacking interactions of the aromatic chromophores and intermolecular hydrogen bonding between the attached sugars. The resulting handedness is controlled by the chiral information provided by the sugars joined glycosidically at certain positions around the periphery of the aromatic nuclei. This review gives an overview of (i) the physicochemical evidence including circular dichroism, 1H NMR, and X-ray analysis for the structure and supramolecular chirality of these amphiphilic complexes, (ii) the role of the sugars on directing the chirality of the resulting supramolecules, (iii) the energetics of monomer association, and (iv) the possible influence of stacking chirality on insect pollination. © 2005 Wiley-Liss, Inc. Chirality 18:134,144, 2006. [source] Computational study of conformational and chiroptical properties of (2R,3S,4R)-(+)-3,3,,4,4,,7-flavanpentolCHIRALITY, Issue 9 2005Chiara Cappelli Abstract Conformational analysis of (2R,3S,4R)-(+)-3,3,,4,4,,7-flavanpentol, a flavonoid compound displaying both antioxidant and pro-oxidant properties, is performed by molecular mechanics and density functional theory calculations both in the gas phase and in methanol solution by using the Polarizable Continuum Model. Nine different conformations are identified. Absorption (UV) and circular dichroism (CD) spectra and optical rotations are calculated by means of time dependent density functional theory (TDDFT) and compared with experiments. The effects of a complex environment formed by water and proline-rich peptide molecules on the conformational characteristics of (2R,3S,4R)-(+)-3,3,,4,4,,7-flavanpentol and therefore on its UV and CD spectra are investigated by atomistic molecular dynamics simulations. © 2005 Wiley-Liss, Inc. Chirality 17:577,589, 2005. [source] | |||||||||||||