0000000001300195
AUTHOR
Antti Siiskonen
Efficient light-induced phase transitions in halogen-bonded liquid crystals
Here, we present a new family of light-responsive, fluorinated supramolecular liquid crystals (LCs) showing efficient and reversible light-induced LC-to-isotropic phase transitions. Our materials design is based on fluorinated azobenzenes, where the fluorination serves to strengthen the noncovalent interaction with bond-accepting stilbazole molecules, and increase the lifetime of the cis-form of the azobenzene units. The halogen-bonded LCs were characterized by means of X-ray diffraction, hot-stage polarized optical microscopy, and differential scanning calorimetry. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to estimate tha…
Halogen bonding stabilizes a cis-azobenzene derivative in the solid state : A crystallographic study
Crystals oftrans- andcis-isomers of a fluorinated azobenzene derivative have been prepared and characterized by single-crystal X-ray diffraction. The presence of F atoms on the aromatic core of the azobenzene increases the lifetime of the metastablecis-isomer, allowing single crystals of thecis-azobenzene to be grown. Structural analysis on thecis-azobenzene, complemented with density functional theory calculations, highlights the active role of the halogen-bond contact (N...I synthon) in promoting the stabilization of thecis-isomer. The presence of a long aliphatic chain on the azobenzene unit induces a phase segregation that stabilizes the molecular arrangement for both thetrans- andcis-i…
ortho -Fluorination of azophenols increases the mesophase stability of photoresponsive hydrogen-bonded liquid crystals
Photoresponsive liquid crystals (LCs) whose alignment can be controlled with UV-Visible light are appealing for a range of photonic applications. From the perspective of exploring the interplay between the light response and the self-assembly of the molecular components, supramolecular liquid crystals are of particular interest. They allow elaborating the structure-property relationships that govern the optical performance of LC materials by subtle variation of the chemical structures of the building blocks. Herein we present a supramolecular system comprising azophenols and stilbazoles as hydrogen-bond donors and acceptors, respectively, and show that ortho-fluorination of the azophenol dr…
Supramolecular control of liquid crystals by doping with halogen-bonding dyes
Introducing photochromic or polymeric dopants into nematic liquid crystals is a well-established method to create stimuli-responsive photonic materials with the ability to "control light with light". Herein, we demonstrate a new material design concept by showing that specific supramolecular interactions between the host liquid crystal and the guest dopants enhance the optical performance of the doped liquid crystals. By varying the type and strength of the dopant-host interaction, the phase-transition temperature, the order parameter of the guest molecules, and the diffraction signal in response to interference irradiation, can be accurately engineered. Our concept points out the potential…
CCDC 1449804: Experimental Crystal Structure Determination
Related Article: Francisco Fernandez-Palacio, Mikko Poutanen, Marco Saccone, Antti Siiskonen, Giancarlo Terraneo, Giuseppe Resnati, Olli Ikkala, Pierangelo Metrangolo, and Arri Priimagi|2016|Chem.Mater.|28|8314|doi:10.1021/acs.chemmater.6b03460
CCDC 1535157: Experimental Crystal Structure Determination
Related Article: Jaana Vapaavuori, Antti Siiskonen, Valentina Dichiarante, Alessandra Forni, Marco Saccone, Tullio Pilati, Christian Pellerin, Atsushi Shishido, Pierangelo Metrangolo, Arri Priimagi|2017|RSC Advances|7|40237|doi:10.1039/C7RA06397K
CCDC 1449805: Experimental Crystal Structure Determination
Related Article: Francisco Fernandez-Palacio, Mikko Poutanen, Marco Saccone, Antti Siiskonen, Giancarlo Terraneo, Giuseppe Resnati, Olli Ikkala, Pierangelo Metrangolo, and Arri Priimagi|2016|Chem.Mater.|28|8314|doi:10.1021/acs.chemmater.6b03460
CCDC 1449802: Experimental Crystal Structure Determination
Related Article: Francisco Fernandez-Palacio, Mikko Poutanen, Marco Saccone, Antti Siiskonen, Giancarlo Terraneo, Giuseppe Resnati, Olli Ikkala, Pierangelo Metrangolo, and Arri Priimagi|2016|Chem.Mater.|28|8314|doi:10.1021/acs.chemmater.6b03460