Results of analyses of the solution spectra of Pr3+ in the acetates of praseodymium, magnesium, calcium and cadmium complexes are presented. Slater-Condon (F2, F4 and F6), configurational interaction (α,β), spin-orbit (ξ4f), nephelauxetic () bonding (δ) and Judd-Ofelt (T2T4 and T6) intensity parameters are evaluated. Judd-Ofel intensity relationship has been used in the calculation of electric dipole line-strengths. Theoretical evaluation of predicted radiative lifetimes (τR) of the electronic excited states 3P1, 3P0 and 1D2 of Pr3+ in four diff been carried out. 相似文献
Optical spectral studies of Pr3+ in PrCl3 complexes with MgCl2, CaCl2, CdCl2 and NH4Cl have been carried out, and the second derivative spectra of these five Pr3+ complexes are reported. From the observed features of the 3P2 and 1D2 bands, crystal field (A20, A40) parameters were evaluated assuming C3h symmetry for Pr3+ in these complexes. The Slater-Condon(F2, F4 and F6), configuration interaction (α, β) and spin-orbit (ξ4?), Racah (E1,E2 and E3), nephelauxetic (β), bonding (δ) and Judd-Ofelt (T2, T4 and T6) intensity parameters are evaluated. Theoretical estimates of spectral intensities calculated from Judd-Ofelt and electric (Sed)-magnetic (Smd) dipole linestrength methods are in good agreement with the observed values. The radiative lifetimes of elctronic excited states 3P1, 3P0, and 1D2 of Pr3+ in these five different hosts have been theoretically estimated. 相似文献
Interfacial interactions of protonated water clusters adsorbed at aromatic surfaces play an important role in biology, and in atmospheric, chemical and materials sciences. Here, we investigate the interaction of protonated water clusters ((H+H2O)n (where n=1–3)) with benzene (Bz), coronene (Cor) and dodecabenzocoronene (Dbc)). To study the structure, stability and spectral features of these complexes, computations are done using DFT-PBE0(+D3) and SAPT0 methods. These interactions are probed by AIM electron density topography and non-covalent interactions index (NCI) analyses. We suggest that the excess proton plays a crucial role in the stability of these model interfaces through strong inductive effects and the formation of Eigen or Zundel features. Also, computations reveal that the extension of the π-aromatic system and the increase of the number of water molecules in the H-bounded water network led to a strengthening of the interactions between the corresponding aromatic compound and protonated water molecules, except when a Zundel ion is formed. The present findings may serve to understand in-depth the role of proton localized at aqueous medium interacting with large aromatic surfaces such as graphene interacting with acidic liquid water. Besides, we give the IR and UV-Vis spectra of these complexes, which may help for their identification in laboratory. 相似文献
1,4-Difluorobenzo[c]phenanthrene (1,4-DFBcPh) and its putative metabolites, the dihydrodiol and diol epoxides, have been synthesized and structurally characterized, and the extent of DNA binding by the metabolites has been assessed. 1,4-DFBcPh and 1,4-difluoro-10-methoxybenzo[c]phenanthrene were prepared by photochemical cyclization of appropriate naphthylphenylethylenes. The dihydrodiol was synthesized from 1,4-difluoro-10-methoxybenzo[c]phenanthrene, and the diol epoxides were diastereoselectively synthesized from the dihydrodiol. Interesting differences were noted in 1H NMR spectra of the series 1 (syn) diol epoxides of benzo[c]phenanthrene (BcPh) and 1,4-DFBcPh; the BcPh diol epoxide displays a quasi-diequatorial orientation of the hydroxyl groups, but in the 1,4-DFBcPh case these are diaxially disposed. This difference probably stems from the presence of the fjord-region fluorine atom in 1,4-DFBcPh. A through-space, fjord-region H-F coupling has also been observed for 1,4-DFBcPh and its derivatives. Comparative X-ray crystallographic analyses of BcPh and 1,4-DFBcPh and their dihydrodiols show that introduction of fluorine increases the molecular distortion by about 6-7 degrees . As a guide to estimating the molecular distortion and its effects, and for comparison with the X-ray structures in known cases, optimized structures of BcPh, 1,4-DFBcPh, and 1,4-DMBcPh (the dimethyl analogue) as well as their dihydrodiols and diol epoxides were computed. Relative aromaticities of these compounds were assessed by nucleus-independent chemical shift calculations, and 13C NMR chemical shifts were computed by gauge-inducing atomic orbital calculations. 1,4-DFBcPh and its dihydrodiol were subjected to metabolism, and the amount of DNA binding in human breast cancer MCF-7 cells was assessed. The extent of DNA binding was then compared with that for BcPh and its dihydrodiol and the potent carcinogen benzo[a]pyrene. The 1,4-DFBcPh series 2 (anti) diol epoxide-derived DNA adducts were also compared with those arising from intracellular oxidation of the dihydrodiol with subsequent DNA binding. These experiments showed that increased molecular distortion decreased metabolic activation to the terminal metabolites but that diol epoxide metabolites that are formed are the DNA-damaging species. 相似文献
Journal of Solid State Electrochemistry - In this short communication, we study the electrochemical behavior of an individual Al2Cu intermetallic phase (coexisting with α-Al) in 0.1 M... 相似文献
Natural scolecite has been found as an effective catalyst for the one-pot synthesis of 2,4,5-triarylimidazole derivatives
via a three component reaction using benzil or benzoin, aldehydes and ammonium acetate. This method provides several advantages
such as being environmentally benign, reusable, possessing high yields with increased variations of the substituents in the
product and preparative simplicity.
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Dye-sensitized solar cells (DSSCs) offer an alternative to conventional silicon solar cell because of low cost and easy fabrication. However, one major drawback in DSSCs is their low efficiency. This paper reports the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells based on polymer gel electrolytes. Several different polymers, such as polyacrylonitrile (PAN), polymethylmethacrylate (PMMA), poly (vinylidenefluoride (PVdF)), and polyethylene oxide (PEO) have been used as host polymers. A binary iodide mixture consisting of an alkaline iodide salt (small cation) and a quaternary ammonium iodide salt such as tetrapropyl ammonium iodide (Pr4NI) (large cation) has been used as the iodide ion source. In some of these systems, efficiency enhancement of more than 25% has been reached due to the “mixed cation effect”. From these studies, it was established that the variation of the power conversion efficiency with the concentration ratio of the two iodide salts follows the same trend as the short circuit current density (Jsc) and goes through a maximum at a particular salt concentration ratio. The maximum efficiency was found to be higher than the efficiencies of the DSSCs with only a single iodide salt in the electrolyte. The Jsc in these DSSCs appears to be governed by the iodide ion conductivity of the gel electrolyte. The observed efficiency enhancement has been explained on the basis of the electrode effects as well as electrolyte effects where the cations play a dominant role.
A potent fluorescence ‘turn-on’ receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg2+ and Al3+ is synthesized by condensation of rhodamine 6G hydrazide and 4-hydroxy-3-acetylcoumarin. In presence of Al3+ and/or Hg2+ the receptor (HL) exhibits deep pink colouration and a sharp band at 528 nm is appeared in UV–vis titration. Upon gradual addition of Al3+ and/or Hg2+ to the solution of HL significant enhancement of fluorescence intensity is observed at 564 nm in MeCN:H2O (1:5, v/v) medium. The receptor is strongly bound to Al3+ and/or Hg2+ and the association constants (Ka) are found to be 1.74?×?104 and 1.04?×?104 M??1 for Al3+ and Hg2+ respectively.
Graphical Abstract A potent fluorescence ‘turn-on’ receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg2+ and Al3+ is synthesized and characterized. In presence of Al3+ and/or Hg2+ the receptor (HL) exhibits deep pink colouration and significant enhancement of fluorescence intensity is observed at 564 nm in MeCN:H2O (1:5, v/v) medium. The receptor is strongly bound to Al3+ and/or Hg2+ and the association constants (Ka) are found to be 1.74?×?104 and 1.04?×?104 M??1 for Al3+ and Hg2+ respectively.
Nitration of phenols with tertiary butyl nitrite (TBN) obeyed second‐order kinetics with a first‐order dependence on [TBN] and [phenol] under acid‐free conditions. Reaction rates were significantly altered by a change in the dielectric constant and other physical properties of solvent. The rate of nitration increased with an increase in temperature (303–323 K) in different solvent media (acetonitrile, dichloroethane, CCl4, dimethyl formamide (DMF), and toluene). The rates of nitration (log k) could not fit into either Amis or Kirkwood plots [log k’ vs. (1/D) or [(D – 1)/(2D + 1)], but the trends were better explained by the basic form of multivariate linear solvent energy relationships (MLSER) suggested by the Koppel and Palm approach on the one hand and the Kamlet and Taft approach on the other hand. These observations probably substantiate that cumulative contributions of basic solvent parameters (equilibrium as well as frictional solvent effects) and solvent–solute interactions for solvation of transition state during nitration of phenols. Reaction rates accelerated with the introduction of electron‐donating groups and retarded with electron‐withdrawing groups. Accordingly, the reactivity of structurally different phenols was found to follow the following sequence: p‐OH > p‐MeO > p‐Me > H > m‐Me > p‐Cl > p‐Br > m‐Cl > p‐NO2 > m‐OH. The results are interpreted by Hammett's theory of linear free energy relationship. The reaction constant (Hammett's ρ) is a measure of the sensitivity of the reaction toward the electronic effects of the substituent. The rho (ρ) values obtained from the present experiments are fairly large negative values (ρ < 0), indicating attack of an electrophile on the aromatic ring. An increase in temperature decreases the reaction constant (ρ) values. According to Exner, ρ values for a given reaction are influenced by the temperature according to the following relation: ρ = A [1 – β/T]. Obtained “isokinetic temperature (β)” values are in the range of 225–290. These values are far below the experimental temperature range (303–323 K), indicating that the entropy factors are probably more important in controlling the reaction. This point can be seen from the negative entropy values and linearity of multiple linear regression analysis (MLRA). Furthermore, in the present study, rate constants for TBN nitration of ortho‐substituted phenols could not fit into Taft's plots of log(k/kCH3) versus σ* or, Es or combined Taft's relationship. However, Charton's MLRA of the log k with polar, resonance, steric, hydrophobicity, and molar refractivity showing a very good linear relationship was obtained. It is of interest to note that when log kexp values are correlated with log kcal a perfect linearity is obtained with a correlation coefficient of unity, indicating the consonance between experimental and calculated rate constants in the present work. 相似文献