pH triggered smart organogel from DCDHF-Hydrazone molecular switch

• pH-responsive DCDHF-Hydrazone dyes are synthesized and characterized.
• The solvatochromic and pH-responsive molecular switching properties are evaluated.
• The gelation properties can be modulated when exposed to acidic/alkaline gases.

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-4,5,5-trimethylfuran-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 microscopy (TEM) studies of the xerogels obtained from n-propanol provide visual images revealing the formation of fibrous nanostructures.

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