Fourier transform infrared and Raman spectral assignments and analysis of 7-amino-4-trifluoromethylcoumarin

Ultraviolet Circularly Polarized Luminescence in Chiral Perovskite Nanoplatelet-Molecular Hybrids: Direct Binding Versus Efficient Triplet Energy Transfer

The development of ultraviolet circularly polarized light (UVCPL) sources has the potential to benefit plenty of practical applications but remains a challenge due to limitations in available material systems and a limited understanding of the excited state chirality transfer. Herein, by constructing hybrid structures of the chiral perovskite CsPbBr3 nanoplatelets and organic molecules, excited state chirality transfer is achieved, either via direct binding or triplet energy transfer, leading to efficient UVCPL emission. The underlying photophysical mechanisms of these two scenarios are clarified by comprehensive optical studies. Intriguingly, UVCPL realized via the triple energy transfer, followed by the triplet-triplet annihilation upconversion processes, demonstrates a 50-fold enhanced dissymmetry factor glum. Furthermore, stereoselective photopolymerization of diacetylene monomer is demonstrated by using such efficient UVCPL. This study provides both novel insights and a practical approach for realizing UVCPL, which can also be extended to other material systems and spectral regions, such as visible and near-infrared.

Ferric ion detection mechanism of a dicarboxylic cellulose nanocrystal and a 7-amino-4-methylcoumarin based fluorescent chemosensor

As one of Earth's most widely distributed and abundant elements, iron impacts the natural environment and biological systems. Therefore, developing a simple, rapid, and accurate Fe3+ detection method is vital. Fluorescent dicarboxylic cellulose nanocrystals (FDCN) with selective quenching of Fe3+ were synthesized using 7-amino-4-methylcoumarin (AMC), and dicarboxylic cellulose nanocrystals (DCN) prepared by sequential periodate-chlorite oxidation. The sensing characteristics and detection mechanism of FDCN for Fe3+ were studied by fluorescence spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), the Stern-Volmer equation, Job's plot method, and the Benesi-Hildebrand equation. The results showed that FDCN was highly selective for Fe3+, and other metal ions did not reduce the selectivity. High sensitivity with a detection limit of 0.26 μM and a Stern-Volmer quenching constant of 0.1229 were also achieved. The coordination between Fe3+ and the carboxylic, hydroxyl, and amide groups on the surface of FDCN and the carbonyl of coumarin lactones to form FDCN/Fe3+ complexes prevented the intramolecular charge transfer (ICT) process and led to the fluorescence quenching of FDCN. EDTA restored the fluorescence emission of quenched FDCN. The complexation stoichiometry of Fe3+ to FDCN was 1 : 1, and the association constant was 3.23 × 104 M-1. The high hydrophilicity, sensitivity, and selectivity of FDCN for Fe3+ make the chemosensor suitable for Fe3+ trace detection in drinking water and biology.

Nanocapsules for 5-fluorouracil delivery decorated with a poly(2-ethylhexyl methacrylate-co-7-(4-trifluoromethyl)coumarin acrylamide) cross-linked wall

Nanocapsules with reverse cross-linked polymer walls containing coumarin moieties are capable of encapsulating 5-fluorouracil and accomplishing a comprehensive strategy in a drug delivery system.

Density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 6-methyl-2-chromenone

The Fourier-transform infrared and FT-Raman spectra of 6-methyl-2-chromenone (6M2C) was recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1) respectively. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 6M2C were carried out by density functional theory (DFT/B3LYP and LSDA) method with 6-311++G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The values of the total dipole moment (μ) and the first order hyperpolarizability (β) of the investigated compound were computed using B3LYP/6-311++G(d,p) calculations. The calculated results also show that 6M2C might have microscopic non-linear optical (NLO) behaviour with non-zero values. A detailed interpretation of infrared and Raman spectra of 6M2C is also reported. The calculated HOMO-LUMO energy gap shows that charge transfer occur within the molecule. The molecular electrostatic potential map shows that the negative potential sites are on the electronegative atoms as well as the positive potential sites are around the hydrogen atoms. The NMR spectrum is used in conjunction with other forms of spectroscopy and chemical analysis to determinate the structures of complicated organic molecules.

Vibrational spectra, structural conformations, scaled quantum chemical calculations and NBO analysis of 3-acetyl-7-methoxycoumarin

The powder form NIR-FT Raman and FT-IR spectra of 3-acetyl-7-methoxycoumarin (3A7MC) have been recorded in the regions 4000-400 and 3500-100 cm(-1), respectively. The equilibrium geometry, vibrational frequencies, band intensities, NMR spectra, NBO analysis and UV-Vis spectral studies of the most stable conformer have been calculated by density functional B3LYP method with the 6-311G(d,p) basis set. A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra, the calculated wavenumber and intensity of the vibrational bands and the potential energy distribution over the internal coordinates. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping the electron density isosurface with electrostatic potential surfaces (ESP). Natural bond orbital analysis has been carried out to understand the nature of different interactions responsible for the electron delocalization and the intramolecular charge transfer between the orbitals (n→π(∗), n→σ(∗), π→π(∗)).

Optical properties and chemical behavior of Laser-dye Coumarin-500 and the influence of atmospheric corona discharges

Structure elucidation of Coumarin-500 Laser-dye in cyclohexane at room temperature has been studied by UV-Vis, Raman, and FTIR spectroscopic techniques. Optical properties and chemical behavior under the influence of atmospheric positive electric pulsed corona discharges were also examined. The effects of UV-Vis irradiation changed some optical parameters, such as decrease in optical density on the absorption spectrum and formation of photoproducts, due to the chromaticity removal. No significant optical changes were observed in the light absorption upon UV-irradiation but large changes in absorption spectrum were observed after positive electric corona discharge treatments, FTIR and Raman spectra in non-polar solvent are recorded and interpreted.