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• The Schiff base senses Al(III) ions with a fluorescent enhancement. • The detection mechanism involves formation of an octahedral Al(III) complex. • Sensing mechanism was delineated using spectral and DFT/TD-DFT studies. • The probe detected Al(III) successfully in different natural matrices. Spectroscopic investigation and Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations have been carried out to delineate the mechanism of fluorescent detection of Al(III) by a new Schiff base (CN3) in an aqueous solution. CN3 was synthesized and characterized using 1H and 13C NMR and mass spectral techniques. Upon adding Al(III), the weak fluorescence of CN3 (512 nm) became enhanced with a slight blue shift to 502 nm. CN3 served as an efficient probe for highly selective and sensitive Al(III) detection without the interference of environmentally and biologically significant cations and anions. The limit of detection (LOD) was determined to be 1.3 µM. Job's continuous variation method of analysis suggested the formation of a 1:1 complex between CN3 and Al(III), which was confirmed as an octahedral complex by 27Al NMR and mass spectral data. The binding constant of the complex was found to be 7×104 M−1. The mode of coordination of CN3 with Al(III) was ascertained by 1H NMR titration experiments. CN3 served as an OONN-type tetradentate ligand to form a chelate, which is responsible for the enhancement of fluorescence of CN3 upon binding with Al(III) due to chelation enhanced fluorescence (CHEF) mechanism. The optical properties of CN3 and its Al(III) complex were corroborated well by DFT and TD-DFT calculations. [ABSTRACT FROM AUTHOR]

• Synthesis growth and molecular interaction of organic nonlinear optical single crystals of (E)-N′-(2,3-dimethoxybenzylidene)−4-fluorobenzohydrazide (DMB-FBH) were discussed. • X-ray single-crystal diffraction analysis confirmed the structure. • Vibrational analysis and various electronic properties of the compound were studied using density functional theory (DFT) calculations. • Hirshfeld surface analyses and fingerprint plots confirmed the O...H, N...H, C...C and C...H intermolecular hydrogen bonds interaction. • UV–visible and the fluorescence emission spectra of the DMB-FBH in aqueous solutions were recorded. • Third order nonlinear optical susceptibility (χ3) of DMB-FBH was determined by Z-scan measurement. Organic nonlinear optical single crystals of (E)-N′-(2,3-dimethoxybenzylidene)-4-fluorobenzohydrazide (DMB-FBH) were synthesized and grown using slow evaporation crystallization from ethanol solution. The single crystal X-ray diffraction scattering revealed that the DMB-FBH crystallised in the tetragonal crystal system with a centro symmetric space group of I 4 1 /a. The crystallographic bond lengths and bond angles were compared with the values generated from optimized molecular geometry based on quantum chemical calculations. The functional group vibrations were identified theoretically by density functional theory with B3LYP 6–311 G (d,p) basis set using Gaussian 09 software package and their vibrations were compared with the experimental FT-IR spectra. The UV-visible and the fluorescence emission spectra of the DMB-FBH in aqueous solutions were recorded. The HOMO-LUMO energy level pictogram addressed the intramolecular charge transfer (ICT) interaction between donor and acceptor moieties and their impact on the energy gap was determined. Different interactions such as O···H, N···H, C···C and C···H in DMB-FBH were quantified via fingerprint plots and these results were compared with that of similar structure. The detailed molecular docking simulation was carried out with M. tuberculosis protein [PDB ID:2 × 22]. The third order nonlinear optical susceptibility (χ3) of DMB-FBH was confirmed experimentally by Z-scan method and their conversion efficiency was higher than the other hydrazones derivatives. In short, this work discusses the crystal structure, identification and quantification of the molecular interactions, thermal, antimycobacterial and optical properties of new hydrazone derivative. Energy frameworks (left) coloumb dispersion (center) and total energy (right) of DMB-FBH crystal structure. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

A new organic,1-methylpiperazine-1,4-diium bis(hydrogen oxalate) (compound 1) has been synthesized at room temperature. This compound was subject to various characterization studies such as elemental analysis, powder X-ray diffraction, FTIR, UV–Vis and NMR spectroscopy. The structure of the crystal was confirmed by powder X-ray diffraction analysis. The 13C CP-MASNMR spectrum confirms the results predicted by X-ray diffraction. The Hirshfeld surface analysis and fingerprint plot of the compound has been presented to explore the nature of non-covalent interactions and their relative contributions in building the solid-state architecture. Furthermore, the density functional theory (DFT) methods were used to explore the optical and nonlinear optical (NLO) properties of compound 1. The calculated isotropic (α iso) and anisotropic (α aniso) linear polarizabilities are found to be28.42 × 10−24 esu and 4.81 × 10−24 esu, respectively. While the average third-order NLO polarizability <γ>of compound 1 is found to be 40.64 × 10−36 esu at M06/6-31 + G∗ level of theory. A comparison of <γ> amplitude of the studied compound with a prototype NLO molecule of para -Nitroaniline (7.41 × 10−36 esu) showed that <γ> amplitude of compound 1 is ∼5 times larger as compared to that of p -NA. Moreover, the frontier molecular orbitals, molecular electrostatic potential maps are drawn to get several structure-property insights for compound 1. Image 1 • The title compound was synthesized at room temperature. • The compound was characterized by powder X-ray diffraction, IR, NMR and UV–visible. • The non-covalent contacts were analyzed by Hirshfeld surface. • The density functional theory (DFT) methods were used to explore the optical and nonlinear optical properties. [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]