pH triggered smart organogel from DCDHF-Hydrazone molecular switch

Abstract

The design, synthesis and photophysical properties of a Low Molecular Weight pH-responsive Gelator (LMWG) based on alkoxy group functionalized DCDHF-Hydrazones (DCDHF-H) are described. A straightforward synthesis of DCDHF-Hydrazone (DCDHF-H) chromophores was achieved via simple azo-coupling starting from 2-(dicyanomethylene)-2,5-dihydro-4,5,5trimethylfuran-3-carbonitrile and alkoxy bearing aryl diazonium chloride derivatives. The DCDHF-H efficiently gelate selected organic solvents and reversibly respond to pH stimuli with a gel-sol conversion and an associated color change from yellow to purple. Self-assembly of these molecules, as indicated by X-ray crystallography, occurs via cooperative π-π stacking and van der Waals interactions producing gelation in some pure and mixed organic solvents.Furthermore, the presence of acidic or alkaline gases leads to a dramatic change in the rheological properties with potential applications in areas such as gas detection devices and drug release systems. Scanning electron microscopy (SEM) and transmission electron Page | 2 microscopy (TEM) studies of the xerogels obtained from n-propanol provide visual images revealing the formation of fibrous nanostructures.

Synthesis and Self‐Assembly of Novel s‐Tetrazine‐Based Gelator

“…The gelation studies of the minimum gel concentration values are displayed in Table . The minimum gelation concentration values demonstrate solvent dependent performance and occur in the range of 2.38 and 9.63 m m which is comparable to a variety of reported organogelators containing long alkoxy side chains …”

“…Recently, low molecular‐weight organogelators (LMOGs) have attracted considerable interest due to the large diversity of gelators giving rise to thermally reversible organogels in different solvents . The distinct capability of small organogelator to solidify and hold organic liquids via weak non‐covalent interactions such as π‐π stacking, push‐pull systems, hydrogen bonding, and van der Waals interactions, has received significant attention . It is significant to control such intermolecular forces in a way that the gelator molecules can self‐assemble into fibrous higher order assemblies but without switching into dense crystals .…”

Synthesis, Solvatochromism, Antibacterial Activity and Dyeing Performance of Tricyanofuran‐Hydrazone Analogues

“…The synthetic approach for the TCFH chromophores 3a‐d employed in this study is shown in Figure . The azo‐coupling reaction occurs in alkaline medium between the diazonium salt and tricyanofuran heterocycle bearing active methyl group to afford the corresponding unstable azo‐product that transforms directly to the more stable hydrazone‐form . The hydrazone N−H functional group was confirmed by 1 H NMR at 12.27‐12.66 ppm; and by FT‐IR at 3241–3392 cm −1 .…”

“…The choice of aromatic amines to produce the corresponding diazonium salts were selected to contain weak electron donating and withdrawing substituents as our earlier publications for TCF‐hydrazone dyes indicated high effects with highly electron donating and withdrawing substituents . The UV‐Vis absorption and fluorescence spectra of the TCF‐based aryl‐hydrazones 3a‐d in a variety of solvents with different polarities are shown in Table .…”

“…The lone pair on the nitrogen of the hydrazone group can partially function as a bridge between donor and acceptor fragments in a push‐pull system or function itself as a donor fragment when in conjugation with strong electron withdrawing group. This leads to potentially attractive solvatochromic and bathochromic shift due to the resulting higher extended conjugation . Hence, the electron‐withdrawing groups certainly play a significant role in promoting solvatochromism.…”