Nilpotent completely positive maps

We study the structure of nilpotent completely positive maps in terms of Choi-Kraus coefficients. We prove several inequalities, including certain majorization type inequalities for dimensions of kernels of powers of nilpotent completely positive maps.     

Synthesis of sugar-derived spiroaminals via lactamization and metathesis reactions

A series of sugar-derived spiroaminals has been synthesized by utilizing cross metathesis, ring closing metathesis and lactamization reactions as key steps from 1-C-alkylated glycosyl azides and important correlations in the spectral data between spiroaminals and their respective anomers are reported.     

(1‐Butyl‐4‐methyl‐pyridinium)[Cu(SCN)2]: A Coordination Polymer and Ionic Liquid

The compound (C₄C₁py)[Cu(SCN)₂], (C₄C₁py=1‐Butyl‐4‐methyl‐pyridinium), which can be obtained from CuSCN and the ionic liquid (C₄C₁py)(SCN), turns out to be a new organic–inorganic hybrid material as it qualifies both, as a coordination polymer and an ionic liquid. It features linked [Cu(SCN)₂]^? units, in which the thiocyanates bridge the copper ions in a μ_1,3‐fashion. The resulting one‐dimensional chains run along the a axis, separated by the C₄C₁py counterions. Powder X‐ray diffraction not only confirms the single‐crystal X‐ray structure solution but proves the reformation of the coordination polymer from an isotropic melt. However, the materials shows a complex thermal behavior often encountered for ionic liquids such as a strong tendency to form a supercooled melt. At a relatively high cooling rate, glass formation is observed. When heating this melt in differential scanning calorimetry (DSC) and temperature‐dependent polarizing optical microscopy (POM), investigations reveal the existence of a less thermodynamically stable crystalline polymorph. Raman measurements conducted at 10 and 100 °C point towards the formation of polyanionic chain fragments in the melt. Solid‐state UV/Vis spectroscopy shows a broad absorption band around 18 870 cm^?1 (530 nm) and another strong one below 20 000 cm^?1 (<500 nm). The latter is attributed to the d(Cu^I)→π*(SCN)‐MLCT (metal‐to‐ligand charge transfer) transition within the coordination polymer yielding an energy gap of 2.4 eV. At room temperature and upon irradiation with UV light, the material shows a weak fluorescence band at 15 870 cm^?1 (630 nm) with a quantum efficiency of 0.90(2) % and a lifetime of 131(2) ns. Upon lowering the temperature, the luminescence intensity strongly increases. Simultaneously, the band around 450 nm in the excitation spectrum decreases.     

Spectroscopic investigation on the interaction of ICT probe 3-acetyl-4-oxo-6,7-dihydro-12H Indolo-[2,3-a] quinolizine with serum albumins

Interaction of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), a biologically active molecule, with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA) have been studied using steady state and picosecond time-resolved fluorescence and fluorescence anisotropy. The polarity dependent intramolecular charge transfer (ICT) process is responsible for the remarkable sensitivity of this biological fluorophore to the protein environments. The CT fluorescence exhibits appreciable hypsochromic shift along with an enhancement in the fluorescence yield, fluorescence anisotropy (r) and fluorescence lifetime upon binding with the proteins. The reduction in the rate of ICT within the hydrophobic interior of albumins leads to an increase in the fluorescence yield and lifetime. Marked increase in the fluorescence anisotropy indicates that the probe molecule is located in a motionally constrained environment within the proteins. Micropolarities in the two proteinous environments have been determined following the polarity sensitivity of the CT emission. Addition of urea to the protein-bound systems leads to a reduction in the fluorescence anisotropy indicating the denaturation of the proteins. Polarity measurements and fluorescence resonance energy transfer (FRET) studies throw light in assessing the location of the fluorophore within the two proteinous media.     

Kinetic Study of the Interaction of Three Glycine-Containing Dipeptides with Hydroxopentaaquarhodium(III) Ion in Aqueous Medium

The kinetics of the interaction of three glycine-containing dipeptides, namely, glycyl-L-valine (L¹-L??H), glycyl-glycine (L²-L??H) and glycyl-L-glutamine (L³-L??H), with [Rh(H₂O)₅OH]²⁺ has been studied spectrophotometrically in aqueous medium as a function of the Rh(H₂O)₅OH²⁺ and dipeptide concentrations, pH and temperature, at constant ionic strength. At pH = 4.3, the substrate complex exists predominantly as the hydroxopentaaqua species and dipeptides as zwitterions. The reaction has been found to proceed via two parallel paths: both processes are ligand dependent. The rate constants for the processes are of the order: k ₁??10^?3 s^?1 and k ₂??10^?5 s^?1. The activation parameters for both steps were evaluated from Eyring plots. Based on the kinetic and activation parameters an associative interchange mechanism is proposed for both of the interaction processes. The low $\Delta H_{1}^{\neq}$ and $\Delta H_{2}^{\neq}$ values and large negative values of $\Delta S_{1}^{\neq}$ and $\Delta S_{2}^{\neq}$ support the associative mode of activation for both processes. The product of the reaction has been characterized using IR and ESI-mass spectroscopic analysis.