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An ultrasensitive ratiometric fluorescent sensor made of an N,N-dimethylaminonaphthalene anhydride moiety for detection of aliphatic primary amines is reported. Biogenic amines at nanomolar concentration is detected with the additional ability to discriminate between primary, secondary and tertiary amines by using both UV-Visible and fluorescence spectroscopy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Micellar environments and cucurbit[7]uril binding modulate p K a of Norharmane (NHM). • Large positive p K a shift imparts a remarkable effect on NHM photophysics. • Encapsulation-induced protonation of NHM significantly enhances aqueous solubility. • Enhanced solubility was validated using live-cell fluorescence imaging. Abstract The effect of supramolecular nanocavity on photophysical and acid-dissociation properties of Norharmane (NHM), a physiologically important, anxiety control and memory-enhancing β -carboline-based drug, has been investigated using steady-state absorption and fluorescence spectroscopy. Self-assembled organization derived from surfactants and rigid water-soluble macrocyclic host Cucurbit[7]uril (CB7) have been selected for this investigation. The confined-space offered by the supramolecular assemblies modulates the p K a value of NHM (up to 3 units) as it can exist in two protolytic forms at near neutral pH. Therefore, the pH-dependent binding properties, modulation of p K a value and its consequences on the photophysical, chemical and solubility properties are investigated in detail. This investigation shows a large shift in the protolytic equilibrium which in turn causes ca. 15 times solubility-enhancement at near neutral pH. Moreover, the effect of enhanced solubility has been further investigated by the augmentation in the cellular uptake of NHM entrapped inside CB7. Thus, the modulation of the acid-base properties and solubility of β -carboline-based drugs will have immense potential for their formulation, cellular uptake and bioavailability. [ABSTRACT FROM AUTHOR]

Synthesis, single-crystal X-ray characterization, and spectroscopic investigation of small, non-charged diethyl 6-(dimethylamino)naphthalene-2,3-dicarboxylate (DMNDC) by UV–Visible, steady-state, and time-resolved fluorescence reveal a series of interesting photophysical properties originating from the intrinsic intramolecular charge transfer (ICT) state, leading to diverse applications. Stokes shift, lifetime, and emission maxima of DMNDC show a very good correlation with E T (30) solvent polarity scale for a series of different polarity solvents, confirms that it has very good environment sensitivity. Furthermore, this dye has been found to be an exceptionally suitable probe for determining Critical Micelle Concentration (CMC) and probing self-organization processes of five different type of surfactant with structural diversity. A 20–60 nm blue shift in emission maxima accompanied by a large fluorescence lifetime enhancement ( ca. 23 ns) was observed upon relocation of DMNDC into a hydrophobic microenvironment. Along with this, the small size, electroneutrality, pH stability, and excellent solvatochromic fluorescent properties are employed for deciphering the number of hydrophobic binding pockets with strong affinity and their local microenvironment present in Bovine Serum Albumin (BSA). [ABSTRACT FROM AUTHOR]