Fluorinated liquid crystals formed by halogen bonding

Abstract

New, halogen-bonded fluorinated mesogens are reported; the expected microphase separation associated with perfluoroalkyl chains is surprisingly absent in the mesophase.

A Halogen‐Bonding Catenane for Anion Recognition and Sensing

“…·PF 6 À ·Cl À found by quenched dynamics (see Supporting Information). The MD simulations were carried out with Amber11 [19] using the pmemd.cuda AMBER executable, able to accelerate explicit solvent Particle Mesh Ewald (PME) calculations through the use of GPUs.…”

“…The coupling of 5 and 3 afforded the desired bis-vinyl appended precursor 6 + ·Br À in a yield of 60 % It is noteworthy that the bromide anion template was found to be crucial to the synthesis of the XB catenane. Repeating the RCM reaction by using 6 + ·PF 6 À in the presence of 10 wt % Grubbs 2nd generation catalyst in dichloromethane gave only the macrocycle 8·PF 6 À which was isolated in 25 % yield by silica gel preparatory thin layer chromatography (Scheme 3).…”

Halogen-Bonded Photoresponsive Materials

“…The field has expanded over the years, as has also been reviewed recently [50]. The majority of halogen-bonded LCs are assembled by combining alkoxystilbazoles, widely used promesogenic molecules [51], with halogen-bond donors such as iodoperfluorobenzenes [52], iodoperfluoroalkanes [53], iodoacetylenes [54], and molecular iodine [55]. From these examples, one could argue that very strong halogen-bond donors are required to stabilize the high-temperature mesophases, and that only molecules containing highly electrophilic iodine atoms are suitable for the task.…”

Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds

“…Haloperfluoroalkanes are robust XB donors, and their ability to steer the supramolecular assembly by XBs and F···F interactions is well described [36]. However, the volatile nature of these compounds often results in oily or waxy substances, which are difficult to characterize using single crystal X-ray diffraction [18,37]. Despite their reluctance to crystallize, our attempts from 8 × 4 (acceptor × donor) combinations resulted in 17 crystal structures, providing an impressive crystallization success rate to analyze and understand the interactions at play in their solid-state structures.…”

“…Carefully designed nitrogen compounds are successfully utilized as molecular building blocks engaging in (N−X−N)⁺X − XBs to construct supramolecular structures resembling metal coordination frameworks [15]. However, weaker C−I···N XBs with typical RXB values ranging from 0.75 to 0.90 are still of considerable importance for applications in materials chemistry, e.g., for triggering liquid crystallinity and gelation behaviour [16][17][18].…”