Laura De Vega - Academia.edu (original) (raw)
Papers by Laura De Vega
![Research paper thumbnail of Steric and Electronic Situation in the 4-X-4′-[(4′′-Y-Phenyl)ethynyl]biphenyl Homologous Series: A Joint Theoretical and Spectroscopic Study](https://attachments.academia-assets.com/45005088/thumbnails/1.jpg)
](The Journal of Physical Chemistry A, 2010
In this work we have studied the rotational barriers, the polarization of the acetylenic triple b... more In this work we have studied the rotational barriers, the polarization of the acetylenic triple bond, and the molecular dipole moments in the 4-X-4′-[(4′′-Y-phenyl)ethynyl]biphenyl homologous series using the density functional theory (DFT) and 1D/2D NMR spectroscopy. This series of compounds constitutes an effective base for the acquisition of liquid crystals. The equilibrium angle (θ eq ) and the torsional barriers ∆E(0°) and ∆E(90°) are not very sensitive to the substituent effects. We have found evidence for the similarity in the π-conjugation of the Y-substituted and X,Y-disubstituted compounds, the latter with mesomorphic properties, by means of the graphic analysis of the relationship between the molecular dipolar moment µ(D) and the difference between the 13 C NMR chemical shifts of the acetylenic carbon atoms (∆δ CItCII [ppm]). The obtained results contribute to a better understanding of the structure-activity relationship for potential liquid crystalline systems.
Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens subst... more Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4′-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase.
European Journal of Organic Chemistry, 2012
Keywords: Chirality / Self-assembly / Crystal engineering / Cross-coupling / Spectroscopic method... more Keywords: Chirality / Self-assembly / Crystal engineering / Cross-coupling / Spectroscopic methods By changing the position of the homochiral alkoxy substituents of C 3 -symmetric 1,3,5-trialkynylbenzenes from the center to the periphery, the macroscopic chirality of the resulting [a]
Nonlinear Optical Thin Film Device from a Chiral Octopolar Phenylacetylene Liquid Crystal
The Journal of Organic Chemistry, 2012
A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling be... more A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling between different ethynylbenzenes and triiodobenzenes. The resultant bulk materials are fully characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction. The octopolar nature of the target compounds is studied by UV-vis absorption spectroscopy and hyper-Raleigh scattering in solution. Optimization of the donor-acceptor substitution yields both high hyperpolarizability values and appreciable mesomorphic properties. A simple thin film device for second harmonic generation has been prepared from the nitro-substituted liquid crystalline derivative.
The Journal of Physical Chemistry B, 2010
Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens subst... more Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4′-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase.
The Journal of Physical Chemistry A, 2010
In this work we have studied the rotational barriers, the polarization of the acetylenic triple b... more In this work we have studied the rotational barriers, the polarization of the acetylenic triple bond, and the molecular dipole moments in the 4-X-4′-[(4′′-Y-phenyl)ethynyl]biphenyl homologous series using the density functional theory (DFT) and 1D/2D NMR spectroscopy. This series of compounds constitutes an effective base for the acquisition of liquid crystals. The equilibrium angle (θ eq ) and the torsional barriers ∆E(0°) and ∆E(90°) are not very sensitive to the substituent effects. We have found evidence for the similarity in the π-conjugation of the Y-substituted and X,Y-disubstituted compounds, the latter with mesomorphic properties, by means of the graphic analysis of the relationship between the molecular dipolar moment µ(D) and the difference between the 13 C NMR chemical shifts of the acetylenic carbon atoms (∆δ CItCII [ppm]). The obtained results contribute to a better understanding of the structure-activity relationship for potential liquid crystalline systems.
Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens subst... more Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4′-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase.
European Journal of Organic Chemistry, 2012
Keywords: Chirality / Self-assembly / Crystal engineering / Cross-coupling / Spectroscopic method... more Keywords: Chirality / Self-assembly / Crystal engineering / Cross-coupling / Spectroscopic methods By changing the position of the homochiral alkoxy substituents of C 3 -symmetric 1,3,5-trialkynylbenzenes from the center to the periphery, the macroscopic chirality of the resulting [a]
Nonlinear Optical Thin Film Device from a Chiral Octopolar Phenylacetylene Liquid Crystal
The Journal of Organic Chemistry, 2012
A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling be... more A set of chiral discotic phenylacetylenes have been synthesized by 3-fold Sonogashira coupling between different ethynylbenzenes and triiodobenzenes. The resultant bulk materials are fully characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction. The octopolar nature of the target compounds is studied by UV-vis absorption spectroscopy and hyper-Raleigh scattering in solution. Optimization of the donor-acceptor substitution yields both high hyperpolarizability values and appreciable mesomorphic properties. A simple thin film device for second harmonic generation has been prepared from the nitro-substituted liquid crystalline derivative.
The Journal of Physical Chemistry B, 2010
Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens subst... more Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4′-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase.