FT-IR and FT-Raman, UV spectroscopic investigation of 1-bromo-3-fluorobenzene using DFT (B3LYP, B3PW91 and MPW91PW91) calculations

The FT-IR and FT-Raman spectra of 1-bromo-3-fluorobenzene (C₆H₄FBr) molecule have been recorded using Bruker IFS 66 V spectrometer in the range of 4000–100 cm⁻¹. The molecular geometry and vibrational frequencies in the ground state are calculated using the DFT (B3LYP, B3PW91 and MPW91PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets. The computed values of frequencies are scaled using a suitable scale factor to yield good coherence with the observed values. The isotropic DFT (B3LYP, B3PW91 and MPW1PW91) analysis showed good agreement with the experimental observations. Comparison of the fundamental vibrational frequencies with calculated results by B3LYP methods. The complete data of this molecule provide the information for future development of substituted benzene. The influence of bromine and fluorine atom on the geometry of benzene and its normal modes of vibrations has also been discussed. A study on the electronic properties, such as absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, was performed by time dependent DFT (TD-DFT) approach. The electronic structure and the assignment of the absorption bands in the electronic spectra of steady compounds were discussed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated in gas phase, revealing the correlations between standard heat capacities (C) standard entropies (S), standard enthalpy changes (H) and temperatures.     

FT-IR and FT-Raman spectral investigation, computed IR intensity and Raman activity analysis and frequency estimation analysis on 4-chloro-2-bromoacetophenone using HF and DFT calculations

In this work, the experimental and theoretical spectra of 4-chloro-2-bromoacetophenone (4C2BAP) are studied. FT-IR and FT-Raman spectra of title molecule have been recorded in the region 4000-100 cm(-1). The structural and spectroscopic data of the molecule in the ground state have been calculated by using Hartree-Fock and density functional method (B3LYP) with the 6-31G (d, p) and 6-311G (d, p) basis sets. The vibrational frequencies are calculated and scaled values are compared with the experimental FT-IR and FT-Raman spectra. The DFT (B3LYP/6-311G (d, p)) calculations are more reliable than the ab initio HF/6-311G (d, p) calculations for the vibrational study of 4C2BAP. The optimized geometric parameters (bond lengths and bond angles) are compared with experimental values of the molecule. The alteration of vibrational bands of the carbonyl and acetyl groups due to the presence of halogens (Cl and Br) in the base molecule is also investigated from their characteristic region of linked spectrum.     

Vibrational spectroscopic (FTIR and FTRaman) investigation using ab initio (HF) and DFT (LSDA and B3LYP) analysis on the structure of Toluic acid

The FTRaman and FTIR spectra for Toluic acid (TA) have been recorded in the region 4000-100 cm(-1) and compared with the harmonic vibrational frequencies calculated using HF/DFT (LSDA and B3LYP) method BY employing 6-311G (d, p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (LSDA/B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values for benzoic acid and some substituted benzoic acids. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. The scaled vibrational frequencies at B3LYP/6-311G (d, p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. Some of the vibrational frequencies of the TA are effected upon profusely with the methyl substitutions in comparison to benzoic acid and these differences are interpreted.     

Determining protease substrate selectivity and inhibition by label-free supramolecular tandem enzyme assays

An analytical method has been developed for the continuous monitoring of protease activity on unlabeled peptides in real time by fluorescence spectroscopy. The assay is enabled by a reporter pair comprising the macrocycle cucurbit[7]uril (CB7) and the fluorescent dye acridine orange (AO). CB7 functions by selectively recognizing N-terminal phenylalanine residues as they are produced during the enzymatic cleavage of enkephalin-type peptides by the metalloendopeptidase thermolysin. The substrate peptides (e.g., Thr-Gly-Ala-Phe-Met-NH(2)) bind to CB7 with moderately high affinity (K ≈ 10(4) M(-1)), while their cleavage products (e.g., Phe-Met-NH(2)) bind very tightly (K > 10(6) M(-1)). AO signals the reaction upon its selective displacement from the macrocycle by the high affinity product of proteolysis. The resulting supramolecular tandem enzyme assay effectively measures the kinetics of thermolysin, including the accurate determination of sequence specificity (Ser and Gly instead of Ala), stereospecificity (d-Ala instead of l-Ala), endo- versus exopeptidase activity (indicated by differences in absolute fluorescence response), and sensitivity to terminal charges (-CONH(2) vs -COOH). The capability of the tandem assay to measure protease inhibition constants was demonstrated on phosphoramidon as a known inhibitor to afford an inhibition constant of (17.8 ± 0.4) nM. This robust and label-free approach to the study of protease activity and inhibition should be transferable to other endo- and exopeptidases that afford products with N-terminal aromatic amino acids.     

Steric control in the reactions of 3-pyrazolecarboxylic acid with diorganotin dichlorides

Reaction of 3-pyrazolecarboxylic acid (LH₂) with dibenzyltin dichloride (Bn₂SnCl₂) in the presence of potassium hydroxide afforded a 2D-coordination polymer, [{(Bn₂Sn)₂(μ-L)(μ-LH)(μ-OH)}₂]_n (1), which crystallizes as an ethanol solvate. The repeat unit of the coordination polymer 1 is a tetrameric motif which contains two pairs of centrosymmetrically related dimeric stannoxanes; in the latter the two tin atoms are connected to each other by a μ-OH and a η²-μ-pyrazole ligand. The tetrameric units are linked to each other by the bridging coordination action of the pyrazolecarboxylate ligand to generate a 2D-coordination polymer. An analogous reaction of LH₂ with the sterically encumbered t-Bu₂SnCl₂ afforded the monomeric dinuclear compound [{(t-Bu₂Sn)₂(μ-L)(LH)(μ-OH)}]·H₂O (2). In the latter the two tin atoms are linked to each other by a bridging hydroxide as well as a pyrazole ligand affording a 6-membered ring. The steric hindrance of the tert-butyl groups seems to prevent the elaboration of this unit into a coordination polymer. Both 1 and 2 have been characterized by single crystal X-ray, NMR and ESI-MS studies.     

Desymmetrization of meso diols using enantiopure zinc (II) dimers: Synthesis and chiroptical properties

The one‐pot metal templated synthesis of enantiopure binuclear Zn (II) complexes Zn₂L¹–Zn₂L⁴ were obtained by treating (1R,2R)‐diphenylethylenediamine or (1S,2S)‐diphenylethylenediamine with 2‐hydroxy‐5‐methyl‐1,3‐benzenedicarboxaldehyde or 4‐tert‐butyl‐2,6‐diformylphenol and zinc acetate. The chiroptical properties of the complexes were studied by using circular dichroism spectroscopy. These ΔΔ and ΛΛ complexes were used as enantioselective catalysts for desymmetrization of meso diol to achieve monobenzoylated product with 96% yield and 88% ee.     

A Pyrene-Tetrazole Fused Fluorescent Probe for Effective Real Time Detection Towards Aluminium Ion

Journal of Fluorescence - We constructed a novel-binding site for metal ion detection using a fused tetrazole ring conjugated with aminopyrene (R). The designed structure of the molecule was...     

Spectroscopic,Computational, Antimicrobial,DNA Interaction,In Vitro Anticancer and Molecular Docking Properties of Biochemically Active Cu(II) and Zn(II) Complexes of Pyrimidine-Ligand

Biochemically active Cu(II) and Zn(II) complexes [CuL(ClO₄)₂(1) and ZnL(ClO₄)₂(2)] have been synthesized from N,N donor Schiff base ligand L derived from4,6-dichloropyrimdine-5-carboxaldehyde with 4-(2-aminoethyl)morpholine. The L, complexes 1 and 2 have been structurally characterized by elemental analysis, ¹H-NMR, FTIR, MS, UV-Visible and ESR techniques. The results obtained from the spectral studies supports the complexes 1 and 2 are coordinated with L through square planar geometry. DFT calculations results supports, the ligand to metal charge transfer mechanism can occur between L and metal(II) ions. The antimicrobial efficacy results have been recommended that, complexes 1 and 2 are good anti-pathogenic agents than ligand L. The interaction of complexes 1 and 2 with calf thymus (CT) DNA has been studied by electronic absorption, viscometric, fluorometric and cyclic voltammetric measurements. The calculated K_b values for L, complexes 1 and 2 found from absorption titrations was 4.45?×?10⁴, L; 1.92?×?10⁵, 1 and 1.65?×?10⁵, 2. The Ksv values were found to be 3.0?×?10³, 3.68?×?10³and 3.52?×?10³ for L, complexes 1 and 2 by using competitive binding with ethidium bromide (EB). These results suggest that, the compounds are interacted with DNA may be electrostatic binding. The molecular docking studies have been carried out to confirm the interaction of compounds with DNA. Consequently, in vitro anticancer activities of L, complexes 1 and 2 against selected cancer (lung cancer A549, liver cancer HepG2 and cervical carcinoma HeLa) and normal (NHDF) cell lines were assessed by MTT assay.     

Third-order optical nonlinearities and optical-limiting properties of a Pararosanilin dye in liquid and solid media

Solid-state dye-doped polymers are attractive alternatives to the conventional liquid-dye solutions. In this paper, the third-order nonlinear optical properties of a Pararosanilin dye in 1-Butanol and a dye-doped polymer film were measured by the Z-scan technique using a continuous wave 532-nm diode-pumped Nd:Yag laser. This material exhibits a negative optical nonlinearity. The low-power optical-limiting properties based on the nonlinear refraction of this material have also been studied.     

Spectral and nonlinear studies of an aniline blue dye in liquid and solid media

Solid-state dye-doped polymers are an attractive alternative to conventional liquid dye solutions. In this paper, the spectral characteristics and nonlinear properties of the Aniline Blue dye has been studied. The third-order nonlinear optical properties of the Aniline Blue dye in ethanol and a dye-doped polymer film were measured by the Z-scan technique using a 632.8-nm He-Ne laser. This material exhibits a negative optical non-linearity. The dye at a 0.4-mM concentration exhibited a nonlinear refractive coefficient (n ₂ = ?4.02 × 10^?8 and ?4.41 × 10^?8 cm²/W in liquid and solid media, respectively), a nonlinear absorption coefficient (β = ?9.7 × 10^?4 and ?11.63 × 10^?4 cm/W in liquid and solid media, respectively), and susceptibility (x ⁽³⁾ = 1.844 × 10^?6 and 2.028 × 10^?6 esu in liquid and solid media, respectively). These results show that the Aniline Blue dye has potential applications in nonlinear optics.