Asghar Abbas

Synthesis, characterization and fluorescent property evaluation of 1,3,5-triaryl-2-pyrazolines.

A series of 1,3,5-triaryl-2-pyrazolines was synthesized by dissolving the corresponding 4-alkoxychalcones in glacial acetic acid containing a few drops of concentrated hydrochloric acid. This step was followed by the addition of (3,4-dimethylphenyl) hydrazaine hydrochloride. Finally the target compounds were precipitated by pouring the reaction mixture onto crushed ice. The structures of the synthesized compounds were established by physicochemical and spectroscopic methods. The 1,3,5-triaryl-2-pyrazolines bearing homologous alkoxy groups were found to possess fluorescence properties in the blue region of the visible spectrum when irradiated with ultraviolet radiation. The fluorescent behavior of these compounds was studied by UV-Vis and emission spectroscopy, performed at room temperature.

Synthesis, spectral characterization, self-assembly and biological studies of N-acyl-2-pyrazolines bearing long alkoxy side chains

A series of new pyrazoline derivatives (1b-4c) bearing N-acyl arms and nine to twelve carbon long alkoxy side chains was synthesized and characterized on the basis of spectroscopic data and microanalysis. The nature of self-assembly to understand the interplay of alkoxy chain crystallization and various supramolecular interactions was investigated using single crystal X-ray diffraction studies. Interesting self-assembled supramolecular structures of 1b and 4c were observed in the crystal lattice owing to various CH⋯O, H⋯H, CH⋯π, lonepair⋯π and π⋯π interactions. Further, all the synthesized compounds (1b-4c) were screened for their in vitro antifungal and anti-inflammatory activities. Compounds 2b, 3b, 2c and 3c showed significant to moderate antifungal activity against Microsporum canis whereas most of the other compounds were found inactive against all the five tested fungal strains. Good anti-inflammatory activity was observed for compounds 1b with IC50 value 331 μM compared to 273 μM for Indomethacine, a standard reference drug. The bio-activity data demonstrates the relationship between lipophilicity, solubility and bioavailability.

Homologous 1,3,5-triarylpyrazolines: synthesis, CH⋯π interactions guided self-assembly and effect of alkyloxy chain length on DNA binding properties

A series of new 2-pyrazoline derivatives (1c–12c) bearing one to twelve carbon homologous alkyloxy side chains have been synthesized in good to excellent yields via intramolecular cyclization reaction on treatment of chalcone intermediates (1a–12a) with phenyl hydrazine (1b) and characterized on the basis of their physical and spectral (IR, 1H & 13C NMR, GC-MS) data. The solid state structure of compound (2c) showed intriguing and unique 1D-supramolecular zigzag chain-like self-assembled structure, the driving force of which is only CH⋯π interactions. DNA interaction studies have also been carried out on selected compounds 1c, 3c, 5c, 6c, 9c and 12c of the series by UV-visible spectroscopy to evaluate their anticancer potential and the effect of alkyloxy chain length on DNA binding property. All the tested compounds showed strong DNA binding (105–106 M−1 binding constants) with hyperchromic effect. A slight increase in the DNA binding strength, observed on increasing the chain length of alkyloxy groups, was attributed to their conformational arrangements, leading to the best fit conformation of 1,3,5-triaryl moiety in the minor groove of DNA structure.

Synthesis and spectral characterization of new homologous 1,3,5-triaryl-2-pyrazolines: Influence of alkyloxy chain length on fluorescence.

Twelve new homologous 1,3,5-triaryl-2-pyrazolines (1c-12c) have been synthesized and characterized on the basis of their spectral (IR, (1)H and (13)C NMR and MS) data and microanalysis. The influence of alkyloxy chain length on absorption and fluorescence properties of 1c-12c was studied by UV-Vis and emission spectroscopy. For all the compounds, fluorescence was observed in the blue region of the visible spectrum. Furthermore, a strong influence of alkyloxy chain length was found on the emission intensity of 1,3,5-triaryl-2-pyrazolines, without causing any major blue- or red-shift in the emission wavelength (λmax(em)). The absorption and emission maxima (λmax(abs) and λmax(em)) for all the compounds were observed in the range of 408-416nm and 471-476nm, respectively. The effect of chloro-substituent present on the conjugated backbone of 1,3,5-triaryl-2-pyrazoline moiety is also discussed.

Structure-fluorescence relationship: interplay of non-covalent interactions in homologous 1,3,5-triaryl-2-pyrazolines

Fluorescence intensity depends on the synergy of multiple non-covalent interactions in solutions. Twelve new homologous 1,3,5-triaryl-2-pyrazolines (1–12)·Br have been synthesized and characterized on the basis of their spectral (IR, 1H and 13C NMR and MS) and microanalytical data to investigate the interplay of non-covalent interactions and their effect on absorption and fluorescence properties by UV-vis and emission spectroscopies. All the compounds showed fluorescence in the blue region of the visible spectrum, but a strong influence of alkyloxy chain length was observed on the emission intensity without causing any major blue- or red-shifts in the emission wavelengths. The absorption and emission maxima (λabsmax and λemmax) for all the compounds were observed in the range of 404–414 nm and 467–479 nm, respectively. Compound 12·Br showed the maximum emission intensity, indicating the dominant role of weak van der Waals forces in driving the solution state self-assembly in comparison to other relatively strong intermolecular interactions. The influence of different halogen substituents present on the conjugated backbone of the 1,3,5-triaryl-2-pyrazoline skeleton in relation to the increasing alkyloxy chain length and their ultimate role in driving the solution state self-assembly and fluorescence properties are also discussed.

Synthesis and spectral characterization of new 1,3,5-triaryl-2-pyrazolines highlighting effect of alkyloxy chain length on fluorescence

A series of new 1,3,5-triaryl-2-pyrazolines (1b-12b) having one to twelve carbon alkyloxy side chains were synthesized and characterized on the basis of their spectral (IR, (1)H &(13)C NMR and GC-MS) and microanalytical data. The UV-Vis and emission spectroscopy was used to study the effect of alkyloxy chain length on absorption and fluorescence properties of 1b-12b. All the compounds showed fluorescence in the blue region of the visible spectrum. Interestingly, the alkyloxy chain length strongly affects the emission intensity of 1,3,5-triaryl-2-pyrazoline framework without causing any major blue- or red-shift in the emission wavelength (λmax(em)). The absorption and emission maxima (λmax(abs) &λmax(em)) for compounds (1b-12b) were observed in the range of 337-364nm and 454-464nm, respectively. Furthermore, the effect of fluorine substituent on aryl ring present at 3-position of pyrazoline moiety on fluorescence properties is also discussed.

Isolation and synthesis of flavonols and comparison of their antioxidant activity

Phytochemical investigation of the leaves of Astragalus beckari yielded four flavonol aglycones, namely kaempferol, quercetin, 5-deoxy kaempferol and fisitin. These isolated compounds were then synthesised in the laboratory using the Algar–Flyn–Oyamad reaction. Antioxidant activity of both the isolated and synthesised flavonoids was compared using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay method. The isolated flavonoids were found to be more active.

Quantum chemical investigations of a co-crystal of 1,3,5-tris(4-hydroxyphenyl)benzene and 2,4,6-trimethoxy-1,3,5-triazine

In the present study, quantum chemical investigations were carried out on our previously reported co-crystal based on 1,3,5-tris(4-hydroxyphenyl)benzene and 2,4,6-trimethoxy-1,3,5-triazine, which showed CH···π and π···π interactions driven layer-by-layer self-assembly of hydrogen-bonded hexagonal blocks in the solid state. Using the DFT/B3LYP calculation method with 6-311++G(d,p) basis set in the ground state, the optimized molecular geometric parameters, conformational analysis, vibrational wavenumbers and their assignments, the HOMO–LUMO analysis, molecular electrostatic potential, thermodynamic properties, and atomic charges were calculated to understand various structural features that are playing an important role in its packing. Furthermore, the simulated infrared and Raman spectra of the co-crystal are plotted using the calculated results. The calculated results are in a good agreement with experimental data. The study with constructive propositions may be helpful in understanding complex self-assembled systems and in the construction of similar molecular self-assemblies.Graphical abstract

Crystallographic structure and quantum chemical computations of 1-(3,4-dimethylphenyl)-3-phenyl-5-(4-methoxyphenyl)-2-pyrazoline.

In this study the experimental crystallographic structure and the calculated optimized geometric parameters, vibrational wavenumbers, (1)H NMR and (13)C NMR chemical shift values, electronic absorption maximum wavelength values, HOMO-LUMO analysis, and molecular electrostatic potential (MEP) of 1-(3,4-dimethylphenyl)-3-phenyl-5-(4-methoxyphenyl)-2-pyrazoline (in abbreviated 1h), molecule, (C24H24N2O), by using density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set in the ground state have been reported for the first time. Furthermore the IR and Raman spectra of title molecule were simulated by using calculated vibrational results. Geometric parameters (bond lengths and bond angles) vibrational wavenumbers and (13)C &(1)H NMR chemical shift values for the mentioned compound calculated at B3LYP/6-311++G(d,p) level are in good agreement with the experimental data.

Ethyl 6-(4-ethoxy­phen­yl)-4-(furan-2-yl)-2-oxocyclo­hex-3-ene-1-carboxyl­ate

The title compound, C21H22O5, was prepared by NaOH-catalysed cyclocondensation of 3-(4-ethoxyphenyl)-1-(furan-2-yl)prop-2-en-1-one with ethyl acetoacetate. In the crystal, C—H⋯O and C—H⋯π interactions link the molecules. In the title molecule, the furan and cyclohexene rings are almost parallel [6.77 (11)°] and the cyclohexene ring is approximately perpendicular to the benzene ring [84.79 (5)°].