A Facile Synthesis of Substituted Benzodiazepines Using Solid Support

An easy and convenient synthetic procedure for the preparation of benzodiazepines by coupling microwaves with the solvent technique have been elaborated.     

Self-assembled Monolayers of Two Aromatic Disulfides and a Diselenide on Polycrystalline Silver Films: An Investigation by SERS and XPS

Self-assembled monolayers of diphenyldisufide (DDS), naphthalenedisulfide (NDS), and diphenyldiselenide (DDSe) on polycrystalline silver films have been investigated by surface enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS). DDS adsorbs on Ag through a homolytic cleavage of the S-S bond and resultant thiolate at the surface decomposes upon prolonged exposure to air. The geometry of the molecule is such that the benzene ring is almost horizontal to the surface. The Raman spectrum has been assigned in the light of ab-initio molecular orbital calculations. In DDSe, the Se-Se bond is retained upon adsorption and the molecule sticks up. In contrast, NDS is highly reactive on the microscopically rough surface so that a stable monolayer could not be prepared. A temperature dependent Raman study of the DDS monolayer shows the absence of any reorientation at the surface as one would expect from the adsorption geometry. XPS study complements the SERS data and shows the presence of Ag2S on an NDS exposed surface. Copyright 1999 Academic Press.     

Electron transfer reactions of iron(III)-polypyridyl complexes with organic sulfoxides

The redox reactions of four iron(III)-polypyridyl complexes with six aryl methyl sulfoxides have been investigated by spectrophotometric technique. The reaction follows clean second order kinetics and proceeds through rate determining electron transfer (ET) from organic sulfoxides to iron(III). The Marcus cross-reaction relation has been applied to obtain the self exchange rate constant for the ArSOR/ArS⁺(O)R couple as 1.3×10⁷ M⁻¹ s⁻¹. The application of Marcus theory to this ET reaction shows that the contribution of inner sphere reorganization energy is 0.4 eV. The rate constant and reaction constant values observed with organic sulfoxides are small compared with organic sulfides towards the same oxidant Fe(NN)₃³⁺.     

Determining the resolution of Laplace inversion spectrum

In experiments involving decaying signals, it is often desirable to analyze the data as a sum of exponential decays using the Laplace inversion method. However, Laplace inversion is an ill-conditioned problem, and it is difficult to ascertain the stability of the reconstruction method and resolution of the resulting spectrum. This paper provides an easily computed approximate bound of the resolution and offers guidelines on how to design experiments to improve the spectral resolution.     

T(1)--T(2) correlation spectra obtained using a fast two-dimensional Laplace inversion

Spin relaxation is a sensitive probe of molecular structure and dynamics. Correlation of relaxation time constants, such as T(1) and T(2), conceptually similar to the conventional multidimensional spectroscopy, have been difficult to determine primarily due to the absense of an efficient multidimensional Laplace inversion program. We demonstrate the use of a novel computer algorithm for fast two-dimensional inverse Laplace transformation to obtain T(1)--T(2) correlation functions. The algorithm efficiently performs a least-squares fit on two-dimensional data with a nonnegativity constraint. We use a regularization method to find a balance between the residual fitting errors and the known noise amplitude, thus producing a result that is found to be stable in the presence of noise. This algorithm can be extended to include functional forms other than exponential kernels. We demonstrate the performance of the algorithm at different signal-to-noise ratios and with different T(1)--T(2) spectral characteristics using several brine-saturated rock samples.     

Electronic structures and spectra of symmetric meso‐substituted porphyrin: DFT and TDDFT—PCM investigations

DFT and TDDFT calculations at the level of PBE0/6‐31G(d)/6‐31+G(d) were performed systematically on seven porphyrins with symmetrical meso‐substitutents. Our results show that the planarity of the free base porphyrin (BP) are affected by the introduction of substitutents at the meso‐position of the ring. Geometrical studies show that the introduction of electron‐withdrawing groups brings about in‐plane deformation in the porphyrin ring, whereas the bulky substitutents make an out‐of‐plane deformation. However, FMO's diagram shows that electron‐withdrawing groups alter the degeneracy of the HOMO and HOMO ?1 orbtial. Up on introduction of substituents at the meso‐position, the Q band FMOs transitions were the same as in the case of free BP; however, the oscillator strength is changed. Electron releasing substituted at the meso‐position shows bathochromic shift in the Q band region. However, the intensity or the hyperchromic shift is higher for the electron withdrawing groups. Solvation studies show that Q bands are blue shifted and B bands are red shifted, whereas the intensity of the B bands was highly enhanced compared with the Q bands. These theoretical studies would be helpful in designing new porphyrins for the photodynamic therapy and dye‐sensitized solar cell applications. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

An algorithm for solving the multi-period online fulfillment assignment problem

This paper develops an optimal solution procedure for the multi-period online fulfillment assignment problem to determine how many and which of a retailer/e-tailer’s capacitated regional warehouse locations should be set up to handle online sales over a finite planning horizon. To reduce the number of candidate solutions in each period, dominance rules from the facility location literature are extended to handle the nonlinear holding and backorder cost implications of our problem. Computational results indicate that multi-period considerations can play a major role in determining the optimal set of online fulfillment locations. In 92% of our test problems, the multi-period solution incorporated fewer openings and closings than myopic single period solutions. To illustrate the use of the model under changing demands, the multi-period solution yielded different supply chain configurations than the myopic single period solution in over 37% of the periods.