Metal ions sensing properties of some phenylquinoxaline derivatives

The sensitivity and selectivity properties of three phenylquinoxaline derivatives to different metal ions were investigated by absorption and fluorescence spectroscopy. The absorption and fluorescence responses of the phenylquinoxaline derivatives were examined towards the following metal ions Ag⁺, Mg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺, in THF solution. All investigated samples exhibit sensitivity and selectivity to Ag⁺, Co²⁺ and Cu²⁺ ions compared to other metal ions (Mⁿ⁺ = Mg²⁺, Ni²⁺, Zn²⁺, Cd²⁺ and Hg²⁺). The gradual addition of Ag⁺, Co²⁺ and Cu²⁺ ions to a Q-Ox sample solution generates new absorption bands (with maxima at 244, 675 and 294 nm, in presence of the Ag⁺, Co²⁺ and Cu²⁺ ions, respectively) while the emission intensities were weakly quenched, except in presence of Ag⁺ ions, when the emission was almost completely quenched (quenching efficiency at 426 nm, (I₀ - I) / I₀ × 100% = 91%). Absorption and fluorescence results show the formation of 1:2 metal complexes with Ag⁺ ions and 1:1 stoichiometry for a complexation between Q-Ox and Co²⁺ or Cu²⁺ ions. The following characteristics of these phenylquinoxaline derivatives have been calculated and discussed: the effects of the interfering ions, the binding constants and the detection limit of Ag⁺, Co²⁺ and Cu²⁺ ions.

Chemistry and engineering of cyclodextrins for molecular imaging

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides bearing a basket-shaped topology with an "inner-outer" amphiphilic character. The abundance of hydroxyl groups enables CDs to be functionalized with multiple targeting ligands and imaging elements. The imaging time, and the payload of different imaging elements, can be tuned by taking advantage of the commercial availability of CDs with different sizes of the cavity. This review aims to offer an outlook of the chemistry and engineering of CDs for the development of molecular probes. Complexation thermodynamics of CDs, and the corresponding implications for probe design, are also presented with examples demonstrating the structural and physiochemical roles played by CDs in the full ambit of molecular imaging. We hope that this review not only offers a synopsis of the current development of CD-based molecular probes, but can also facilitate translation of the incremental advancements from the laboratory to real biomedical applications by illuminating opportunities and challenges for future research.

Tuning the constrained photophysics of a pyrazoline dye 3-naphthyl-1-phenyl-5-(4-carboxyphenyl)-2-pyrazoline inside the cyclodextrin nanocavities: A detailed insight via experimental and theoretical approach

The modulation in the photophysics of a pyrazoline dye 3-naphthyl-1-phenyl-5-(4-carboxyphenyl)-2-pyrazoline (NPCP), when it drifts from bulk water into the nanocages of aqueous cyclodextrin solutions was investigated. The intramolecular charge transfer (ICT) fluorescence band intensity was found to increase with a blue shift in the presence of cyclodextrins. The results from ¹H NMR and ¹HH COSY NMR spectral analysis clearly points out the position of pyrazoline ring inside the cavity and its role in complexation process. A quantitative assessment of the emission intensity data on Benesi-Hildebrand (B-H) equation along with ESI-MS spectra reveals the probable stoichiometry of NPCP-CD complexes. Molecular docking and molecular dynamics studies were conducted for β/γ cyclodextrin associated inclusion complexes of NPCP. The results obtained by computational studies are in good relation with the data obtained through experimental methods and both ascertain the encapsulation of NPCP into cyclodextrins.

Unveiling a versatile heterocycle: pyrazoline – a review

The design and synthesis of novel fluorescent heterocyclic dyes is a “hotspot” research area, due to their favourable photophysical and electronic properties, which could allow huge advances in the fields of physics, chemistry and biology.

Synthesis of novel boron chelate complexes and proposed mechanism of new rearrangement

We synthesized novel boron chelate complexes by the reaction of pyrazoline derivatives and boron trifluoride diethyl etherate followed by a new rearrangement. The structures of the compounds were characterized by IR, NMR and HRMS, especially, a typical compound 3c was confirmed by X-ray single crystal analysis. We proposed a mechanism of the rearrangement. Moreover, the absorption and fluorescence spectroscopy of these compounds were measured.

Study on the spectral and inclusion properties of a sensitive dye, 3-naphthyl-1-phenyl-5-(5-fluoro-2-nitrophenyl)-2-pyrazoline, in solvents and β-cyclodextrin

3-Naphthyl-1-phenyl-5-(5-fluoro-2-nitrophenyl)-2-pyrazoline (NPFP), a fluorogenic probe and its derivative NPFP-Phenylephrine were synthesized and their absorption and fluorescence properties were recorded in solvents of varying polarity. Spectroscopic studies reveal that, the solvatochromic behavior of the compounds depend not only on the polarity but also on the hydrogen-bonding properties of the solvents. The effects of β-cyclodextrin on the fluorescence properties of both compounds were studied. It was found that there is an enhancement in the fluorescence intensity of labeled drug (NPFP-Phenylephrine) in the presence of β-cyclodextrin. In the present study, the molecular motions of NPFP-Phenylephrine embedded in a β-cyclodextrin cavity have been investigated by fluorescence techniques in steady-state and time resolved modes.

Kinetic exploration supplemented by spectroscopic and molecular docking analysis in search of the optimal conditions for effective degradation of malachite green

The degradation of malachite green (MG) by an alkaline hydrolytic process has been explored spectrophotometrically.

Dual channel selective fluorescent detection of Al3+ and PPi in mixed aqueous media: DFT studies and cell imaging applications

A new, easily synthesizable chemosensor, DFC-EN-p-Ph-NO2, acts as a dual channel (colori- and fluorimetric) sensor for Al³⁺ and PPi.