Conformational effects in the vibrational and electronic spectra of propionaldehyde: Experimental and theoretical studies.

We report here investigations on conformational effects in the vibrational and electronic spectra of the propionaldehyde (propanal) molecule using FTIR (600-3200 cm-1) and vacuum ultraviolet (VUV) synchrotron radiation photoabsorption (52 500-85 000 cm-1) spectroscopy respectively. Detailed theoretical calculations (using DFT and TDDFT methodologies) on ground and excited states of the cis and gauche conformers of propanal are performed; a comprehensive spectral analysis of the IR and VUV spectra is presented. A reinvestigation of the IR spectrum reveals several new bands assigned to the gauche conformer based on theoretical calculations. The VUV spectrum exhibits rich Rydberg series structure assigned to ns, np and nd series converging to the first ionization potentials of the two conformers. Earlier assignments of the 3s cis and gauche origins are revised in addition to extending Rydberg series analysis to several higher members. Vibronic bands accompanying the 3s, 4s and 4p Rydberg states are assigned using estimated vibrational frequencies of cis and gauche conformers in the cationic ground state. Simulated potential energy curves of the first few excited states (singlets and triplets) of cis and gauche conformers of propanal help in gaining insights into photodissociation mechanisms and possible conformational effects therein.

Development of an experimental set-up for low-temperature spectroscopic studies of matrix-isolated molecules and molecular ices using synchrotron radiation.

An experimental set-up for studying photophysics and photochemistry of molecules in an inert gas medium (matrix-isolated) and in the ice phase at low temperatures has been developed and commissioned at the Photophysics beamline, Indus-1 synchrotron radiation source. This end-station uses an in-house-developed closed-cycle cryostat for achieving cryo-temperatures (∼10 K). Synchrotron radiation from the Photophysics beamline is used as the source of UV-VUV photons and the system is equipped with a Fourier transform infrared spectrometer for characterization of the molecular species formed at low temperature. Various individual components of the end-station like closed-cycle cryostat, experimental chamber, gas mixing and deposition systems are tested to ascertain that the desired performance criteria are satisfied. The performance of the composite system after integration with the Photophysics beamline is evaluated by recording IR and UV-VUV photoabsorption spectra of sulfur dioxide at low temperatures (10 K), both in the ice phase as well as isolated in argon matrices. Results obtained are in good agreement with earlier literature, thus validating the satisfactory performance of the system. As an off-shoot of the study, the VUV absorption spectrum of matrix-isolated SO2 in argon matrix up to 10.2 eV is reported here for the first time. This experimental end-station will provide new opportunities to study photon-induced reactions in molecules of environmental, astrochemical and industrial importance. Details of the design, development and initial experimental results obtained are presented.

Electronic spectroscopy of ethyl bromide probed by VUV photoabsorption and quantum chemical calculations.

The electronically excited states of ethyl bromide and its deuterated isotopologue (C2H5Br and C2D5Br) are studied using synchrotron radiation based photoabsorption spectroscopy in the wavenumber region 50 000-86 000 cm-1. A detailed spectral analysis supported by quantum chemical calculations is presented. A complex Rydberg series structure comprising of nsa1, npa1, npe, nda1 and nde series, converging to each of the two spin-orbit split components of the first ionization potential (2E3/2 and 2E1/2) is observed for both the isotopologues. Quantum defect values are consistent with excitation from Br lone pair orbitals. Rydberg series analysis is extended to several higher members as compared to earlier work and corroborates the dominance of the spin-orbit mechanism over the hyperconjugative effect. A few new Rydberg series members converging to the second and third ionization potentials are observed and assigned. The complete gas phase VUV photoabsorption spectrum of C2D5Br up to its first ionization limit and its infrared absorption spectrum in the liquid phase are reported for the first time. An extended vibronic analysis of bands accompanying the first few Rydberg series is reported along with several new assignments. DFT calculations on ground states of neutral and ionic species and TDDFT calculations on singlet and triplet excited states aid and support the spectral analysis. Potential energy curves with respect to the C-Br bond length and the C-C-Br bond angle provide further insights into the nature of the excited states. This work represents a comprehensive study of the electronic absorption spectrum of ethyl bromide and its deuterated counterpart.

Spectroscopy of N,N-dimethylformamide in the VUV and IR regions: Experimental and computational studies.

The electronic absorption spectrum of N,N-dimethylformamide (DMF) is studied in the 45 000-80 000 cm-1 (5.6-9.9 eV) region using synchrotron radiation. The vacuum ultraviolet (VUV) spectrum comprises mostly of Rydberg series of ns, np, and nd types converging to the first two ionization potentials (IPs). Quantum defect values obtained are consistent with excitation of an electron from the highest occupied molecular orbitals localized on nitrogen (4a″) and oxygen (16a'); in addition, the 3s Rydberg transition converging to the third IP (3a″) is observed at 8.95 eV. A reinvestigation of the infrared spectrum of DMF in the 500-4000 cm-1 region with the help of density functional theory (DFT) calculations establishes the planarity of the ground state and leads to revision of several vibrational assignments. Vertical excited state energies and their valence/Rydberg character are predicted using time dependent DFT calculations; excellent correlation is achieved between theoretical results and experimentally observed spectral features. Potential energy curves of the first few excited states give additional insights into the nature of the excited states and their role in photodissociation dynamics. The absorption spectrum of DMF in the region >63 400 cm-1 (7.85 eV) as well as a complete set of spectral assignments in the VUV region (45 000-80 000 cm-1) is reported for the first time. This work represents a comprehensive study of the absorption spectra of DMF in the VUV and infrared regions.

Structural, vibrational and electronic spectroscopic study of 6-hydroxycoumarin using experimental and theoretical methods.

Understanding the photochemical behavior of structural isomers of hydroxycoumarin (HC) having different properties of consequence in biological activities demand spectroscopic information of this class of compounds. Barring 6-hydroxycoumarin (6-HC), other isomers of HC's are well studied spectroscopically. To understand and compare the photochemical activity of 6-HC with other isomers, a detailed study of this molecule has been taken up. For this purpose, electronic, vibrational and structural properties of 6-HC have been studied using ultraviolet absorption and Infrared spectroscopy techniques. Quantum chemical calculations have been performed at DFT/B3LYP level of theory to get the optimized geometry and vibrational frequencies of normal modes to support and analyze experimental data. The detailed vibrational assignments were made on the basis of potential energy distributions. Chemical activity, molecular orbital energies, band gap and hyper-polarizability information have been computed from quantum chemical simulations. NBO analysis helped in understanding the stability of the molecule arising from hyper-conjugative interaction and charge delocalization. UV-Visible spectrum of the compound was recorded in the region 300-600 nm helped in obtaining band gap data of the compound. Molecular Electrostatic Potentials (MESP) were plotted and the respective centers of electrophilic and nucleophilic attacks were predicted with the help of Fukui functions calculations. Further, it was observed that the negative electrostatic potential regions are mainly localized over the oxygen atoms and the positive regions are localized over the benzene ring. Details of the results and analysis of experimental and theoretical spectroscopy studies are presented in this paper.

Treatment of hemorrhoids with individualized homeopathy: An open observational pilot study.

AIM: Controversies and disagreement exist on conventional treatment strategies of hemorrhoids due to relapse, inefficacy, and complications. We intend to evaluate the role of individualized homeopathic treatment in hemorrhoids. MATERIALS AND METHODS: In this prospective, open, observational trial, hemorrhoids patients were treated using five standardized scales measuring complaints severity and anoscopic score. It was conducted at two homeopathic hospitals in India, during from mid-July 2014 to mid-July 2015. Patients were intervened as per individualized homeopathic principles and followed up every month up to 6 months. RESULTS: Total 73 were screened, 52 enrolled, 38 completed, 14 dropped out. Intention to treat population (n: = 52) was analyzed in the end. Statistically significant reductions of mean bleeding (month 3: -21.8, 95% confidence interval [CI]: -30.3, -13.3, P: < 0.00001, d = 0.787; month 6: -25.5, 95% CI -35.4, -15.6, P: < 0.00001, d = 0.775), pain (month 3: -21.3, 95% CI -28.6, -14.0, P: < 0.00001, d = 0.851; month 6: -27.6, 95% CI -35.6, -19.6, P: < 0.00001, d = 1.003), heaviness visual analog scales (VASs) (month 3: -8.1, 95% CI -13.9, -2.3, P: = 0.008, d = 0.609; month 6: -12.1, 95% CI -19.1, -5.1, P: = 0.001, d = 0.693), and anoscopic score (month 3: -0.4, 95% CI -0.6, -0.2, P: < 0.0001, d = 0.760; month 6: -0.5, 95% CI -0.7, -0.3, P: < 0.0001, d = 0.703) were achieved. Itching VASs reduced significantly only after 6 months (-8.1, 95% CI -14.6, -1.6, P: = 0.017, d = 0.586). No significant lowering of discharge VASs was achieved after 3 and 6 months. CONCLUSION: Under classical homeopathic treatment, hemorrhoids patients improved considerably in symptoms severity and anoscopic scores. However, being observational trial, our study cannot provide efficacy data. Controlled studies are required. Trial Reg. CTRI/2015/07/005958.