A fluorescent chemosensor for selective detection of chromium (III) ions in environmentally and biologically relevant samples.

A simple single step one pot multicomponent reaction was performed to synthesize N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2-a]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm â†’ 285 nm) in the UV-Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (ka) obtained from Benesi-Hildebrand plot is 0.21 × 105 M-1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10-7 M and 1.56 × 10-7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples.

Crystal structure and Hirshfeld surface analysis of two imidazo[1,2-a]pyridine derivatives: N-tert-butyl-2-(4-meth-oxy-phen-yl)-5-methyl-imidazo[1,2-a]pyridin-3-amine and N-tert-butyl-2-[4-(di-methyl-amino)-phen-yl]imidazo[1,2-a]pyridin-3-amine.

In the title imidazo[1,2-a]pyridine derivatives, N-tert-butyl-2-(4-meth-oxy-phen-yl)-5-methyl-imidazo[1,2-a]pyridin-3-amine, C19H23N3O, (I), and N-tert-butyl-2-[4-(di-methyl-amino)-phen-yl]imidazo[1,2-a]pyridin-3-amine, C19H24N4, (II), the 4-meth-oxy-phenyl ring in (I) and the 4-(di-methyl-amino)-phenyl ring in (II) are inclined to the respective imidazole rings by 26.69 (9) and 31.35 (10)°. In the crystal of (I), mol-ecules are linked by N-H⋯N hydrogen bonds, forming chains propagating along the [001] direction. The chains are linked by C-H⋯π inter-actions, forming layers parallel to the (010) plane. In (II), the crystal packing also features N-H⋯N hydrogen bonds, which together with C-H⋯N hydrogen bonds link mol-ecules to form chains propagating along the c-axis direction. The chains are linked by C-H⋯π inter-actions to form layers parallel to the (100) plane. Inversion-related layers are linked by offset π-π inter-actions [inter-centroid distance = 3.577 (1) Å]. The inter-molecular inter-actions of both compounds were analyzed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Diastereoselective tandem oxidation/Michael/aldol reaction: unprecedented formation of dispirocyclopentanebisoxindoles and dispiro[acenaphthylene-1,1'-cyclopentane-3',1''-acenaphthylene]-2,2''diones.

An unprecedented tandem oxidation/Michael/aldol reaction is reported. The diastereoselective formation of only a single isomer of dispirocyclopentanebisoxindole and dispiro[acenaphthylene-1,1'-cyclopentane-3',1''-acenaphthylene]-2,2''dione is presented. The reaction generates two new C-C bonds and two all-carbon quaternary chiral stereocenters in a single step.