Organogels composed of trifluoromethyl anthryl cyanostyrenes: enhanced emission and self-assembly

Abstract

A series of α-cyanostyrenes bearing anthracene and electron withdrawing trifluoromethyl units were designed and synthesized. The α-cyanostyrene skeleton favors aggregation induced enhanced emission behavior due to the restriction of intramolecular rotations. Remarkably, the anthryl cyanostyrenes bearing simple trifluoromethyl (CF3) substituents form stable organogels with enhanced fluorescence emission compared to their solution state. In water, the CF3 substituted anthrylstyrenes self-assemble into entangled fibrous nano/microstructures through intermolecular H-bonding, π-π stacking and cyano substituent interactions. The morphological features of the aggregates and the gels were substantiated using scanning electron microscopy, TEM, and powder XRD measurements. The stability of the gels was assessed using rheology investigations.

Structural Insight of Anthracene Orientation by Halogen Substitution: Impact on Solid-State Fluorescence and Stimuli-Induced Fluorescence Switching

“…1 and halogen-substituted anthracene derivatives (Scheme 1) were synthesized by a simple condensation reaction between alpha-cyanostyrene and anthracene carboxaldehyde (Scheme S1). 65 Single crystals of all derivatives were grown by slow evaporation of CH 2 Cl 2 or CH 2 Cl 2 -CH 3 OH mixture (Table S1). Although the extent of the twist differed, anthracene and alpha-cyanostyrene units displayed highly twisted (nearly perpendicular) molecular conformation in the crystal lattice of 1 as well as in halogen-substituted derivatives (Figure 1, Table S2).…”

One‐ and Two‐Component Organogels Containing Cyanostilbene without any Auxiliary Substituents

“…Cyanostilbenes bearing auxiliary linkers such as alkyl chains, glycol units, amide units were known to form stable organogels . Importantly, cyanostilbenes also form stable organogels with smaller auxiliary groups such as trifluoromethyl substituents . Surprisingly, stilbene 3 (14 mg in 600 μL of ethanol) bearing a pyridine ring and devoid of the general auxiliary groups forms a gel in ethanol with a critical gelation concentration of 8.5 mg/mL) (Figure b (inset) & Figure S6).…”

“…Figure b inset). We presumed that F⋅⋅⋅N interaction between fluorine of trifluoromethyl group and pyridyl nitrogen (F⋅⋅⋅N) could be the driving force for the gel formation although F is the least prone to be involved in a halogen bonding interactions . To verify the halogen interactions if any, we performed the gelation experiments with stilbenes 1 having no CF 3 group (non‐gelator)+ 3 (gelator) and 1 + 2 (two‐ non‐gelator stilbenes).…”

α-Cyanostilbene: a multifunctional spectral engineering motif

“…Thus, we developed a series of organogelators based on the polyaromatic hydrocarbons such as anthracene ( SK22–SK24 ) and pyrene ( SK25–SK27 ) derivatized α-CS π-frameworks and functionalized the other end with o -, m -, and p -CF 3 -substituted phenyl units. 111,112 Nevertheless, marginal differences were noted in the SLE behavior due to the weak electron-deficient CF 3 substitution, where increasing the CF 3 count ameliorated the gelation tendency. Upon cooling, these molecules organized into self-assembled nanostructures in t -BuOH through non-covalent F⋯F/H/π and N⋯H/π interactions.…”