Search

A new highly selective fluorescent turn-on probe (RS4) possessing indolinium moiety has been designed and synthesized for the detection of cyanide ion. The probe RS4 displays instantaneous, highly selective and sensitive recognition of cyanide ion over other common anions via change in color and enhancement in fluorescence. Nucleophilic addition of cyanide to the indolinium C-atom leads to the enhancement in fluorescence (λ em 481 nm; Blueish-green emission) and decolourization due to different intramolecular charge transfer (ICT) process. The binding constant of the 1:2 RS4 /CN¯ adduct is determined to be 2.3 × 104 M−1. The limit of detection of cyanide by RS4 is estimated to be 21 nM. Density functional theory (DFT) based calculations strongly substantiate the results of the experimental investigations. Importantly, the probe detects cyanide ion in agro-products (cassava powder and bitter almond), which demonstrates its value to practical application. • The probe senses cyanide with color change and fluorescent enhancement. • The detection mechanism involves nucleophilic addition of CN− at indolinium C-atom. • Sensing mechanism was delineated using spectral and DFT studies. • The probe successfully sensed CN− of cyanogenic glycoside in agro-products. [Display omitted] [ABSTRACT FROM AUTHOR]

The pyrimidine ring is significantly distributed in nature due to its existence in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) as nitrogenous bases. The heterocyclic aromatic compounds have become an important pharmacophore due to promising applications in medicine and nonlinear optics (NLO) fields. Keeping in view of the significance of 4-thiopyrimidines derivatives, we selected phenyl pyrimidine derivatives namely: ethyl 4-((3-chlorobenzyl)thio)-6-methyl-2-phenylpyrimidine-5-carboxylate (1), (4-((4-chlorobenzyl)thio)-6-methyl-2-phenyl-pyrimidin-5-yl)methanol (2) and 4-((4-chlorobenzyl)thio)-5,6-dimethyl-2-phenylpyrimidine (3) for NLO study and comparative analysis. Overall, density functional theory (DFT) findings of structural parameters at B3LYP/6-311G(d,p) level show excellent concurrence with the experimental data which confirms the purity of 1 , 2 and 3. The vibrational analysis of 1 , 2 and 3 have been carried out by DFT calculations based on B3LYP/6-311G(d,p) level of theory. The natural bonding orbital (NBO) analysis has been used to get insight into non-covalent interactions. From DFT calculations, various parameters such as natural population analysis (NPA) atomic charges, HOMO–LUMO energies and global reactivity parameters have been obtained. The molecular electronic potential (MEP) and parametric molecular electrostatic potential (PMEP) have also been derived for 1 , 2 and 3. The photophysical properties of investigated molecules were estimated using time dependent DFT (TDDFT) at B3LYP/6-311G(d,p) level of theory. Nonlinear optical (NLO) analysis has also been carried out by DFT calculations with B3LYP/6-311G(d,p) functional. The NLO properties of 1 , 2 and 3 were observed larger as compared to the standard molecule indicating the considerable NLO character of all molecules especially recommended the NLO activity of 1 for optoelectronic associated hi-tech applications. Image 1 • Three novel phenyl pyrimidine derivatives 1 , 2 and 3 were studied. • Computational study was done at B3LYP/6-311G(d,p) level for comparative study. • Comparative study reveals a good agreement between XRD and DFT results. • FMO, NBO, global reactivity parameter, NPA, MEP, PMEP and NLO analysis were performed. • All studied compounds hold considerable NLO character and recommended for optoelectronic associated hi-tech applications. [ABSTRACT FROM AUTHOR]