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321.
A. Antony Muthu Prabhu R.K. Sankaranarayanan S. Siva N. Rajendiran 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):484-497
The absorption and fluorescence spectra of fast violet-B (FVB) and benzanilide (BA) have been analysed in different solvents, pH and β-cyclodextrin. The inclusion complex of FVB with β-CD is investigated by UV–visible, fluorimetry, AM 1, FTIR and SEM. The absorption maximum of FVB (anilino substitution) is red shifted than that of BA, but the benzoyl substitution hardly changed the ground state structure of BA. Compared to BA, the emission maxima of FVB largely blue shifted in cyclohexane and aprotic solvents, but red shifted in protic solvents and the longer wavelength maxima in FVB is due to the intramolecular charge transfer (TICT). In BA, the normal emission originates from a locally excited state and the longer wavelength band due to intramolecular proton transfer in non-polar/aprotic solvents and in protic solvents it is due to TICT state. β-CD studies reveal that, FVB forms 1:2 complex from 1:1 complex and BA forms 1:2 complex with β-CD. 相似文献
322.
323.
Tatapudi Kiran Kumar Bandi Siva Ajay Anand Komati Anusha Satish Mohabe Araveeti Madhusudana Reddy Franoise Le Devehat Ashok Kumar Tiwari Joël Boustie Katragadda Suresh Babu 《Molecules (Basel, Switzerland)》2022,27(19)
In this study, we propose ultra-performance liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry (UPLC-QToF-MS/MS)-guided metabolite isolation as a choice analytical approach to the ongoing structure–activity investigations of chemical isolates from the edible lichen, Ramalina conduplicans Vain. This strategy led to the isolation and identification of a new depside (5) along with 13 known compounds (1–4, 6–14), most of which being newly described in this lichen species. The structures of the isolates were established by detailed analysis of their spectral data (IR, NMR, and Mass). The acetone extract was further analyzed by UPLC-Q-ToF-MS/MS in a negative ionization mode, which facilitated the identification and confirmation of 18 compounds based on their fragmentation patterns. The antioxidant capacities of the lichen acetone extract (AE) and isolates were measured by tracking DPPH and ABTS free radical scavenging activities. Most isolates displayed marked radical scavenging activities against ABTS while moderate activities were observed against DPPH radical scavenging. Except for atranol (14), oxidative DNA damage was limited by all the tested compounds, with a marked protection for the novel isolated compound (5), as previously noted for the acetone extract (p < 0.001). Furthermore, compound (4) and acetone extract (AE) have inhibited intestinal α-glucosidase enzyme significantly (p < 0.01). Although some phytochemical studies were already performed on this lichen, this study provided new insights into the isolation and identification of bioactive compounds, illustrating interest in future novel analytical techniques. 相似文献
324.
Thin films of several thicknesses in the form of MIM structures are prepared from the powders of tin oxide (SnO2) by thermal evaporation technique in a vacuum of 10−5 Torr. The dielectric properties of tin oxide film capacitors have been studied with temperatures varying from 77 to 400 K and also with frequency. At 77 K the values of capacitance and loss tangent are small for these films. With increasing temperature the values of capacitance and loss tangent increase. The capacitance-temperature plots show peak values of capacitance at 345 K for 1 kHz, 350 K for 2 kHz, 360 K for 5 kHz and 368 K for 10 kHz. These peak values of capacitance can be eliminated by repeated heating and cooling of the structures. The activation energy for the migration of charge carriers is calculated for tin oxide films and is found to be 0.13 eV. The results obtained on the dielectric properties of tin oxide thin films are presented and discussed. 相似文献
325.
Dr. Chenikkayala Siva Sankara Dr. Shweta Bhagat Dr. Ajeet Chandra Prof. Dr. Irishi N. N. Namboothiri 《European journal of organic chemistry》2023,26(15):e202300069
An enantioselective desymmetrization of curcumins with 3-olefinic oxindoles involving a cascade double-Michael addition strategy provides direct access to spirocyclohexanone-oxindoles with complete regio- and diastereoselectivities and excellent enantioselectivities, besides good to excellent yields. The products possess three contiguous chiral centers and multiple reactive functionalities. The observed selectivities were rationalized by transitions state energy calculations at B3LYP//6-31g(d) level of DFT. 相似文献
326.
The X‐ray diffraction and Infrared (IR) spectral studies of (NH4)2 CuCl4.2H2O single crystals reveals that these crystals contains tetragonal crystal structure with the unit cell dimensions of a = 7.58Å, c = 7.95Å, z= 2, β =90° and two water molecules in the unit cell. The temperature dependence of thermally stimulated depolarization current (TSDC) and dc electrical conductivity (σ) studies of this two‐dimensional (NH4)2 CuCl4.2H2O single crystal have been carried out in 77K–300K temperature region. The TSDC thermograph shows only one sharp peak at 248K with a peak current of 130nA, which is attributed to the Maxwell‐Wagner peak. The activation energy (U), relaxation time (τ) are calculated as 0.78eV and 3.44×10‐15 s respectively. Dc electrical conductivity studies of these crystals show a first order phase transition at about 248K. 相似文献
327.
J. Siva Kumar K. V. Satyanarayana Rao U. V. Subba Rao 《Crystal Research and Technology》1989,24(12):1291-1294
Thin films of various thicknesses in the form of MIM structures have been prepared from the powders of high purity of SnO2, Sb2O3, and their mixed powders separately by the thermal evaporation technique in a vacuum of 10−5 Torr. The dielectric properties of these oxide thin films have been studied with ageing time and also with frequency at room temperature. The results obtained have shown that the capacitance and loss tangent of the structures initially fall off rapidly and thereafter they attain a constant value even after ageing the capacitors for about 20 days. The rapid fall of capacitance and loss tangent may be due to the rapid decrease in the density of defects due to ageing time. The results thus obtained on SnO2, Sb2O3, and their mixed thin film capacitors are presented and discussed. 相似文献