Resolution of pentafluorophenyl 2-phenylpropanoate using combinations of quasi-enantiomeric oxazolidin-2-ones

The kinetic, mutual and parallel resolution of a series of structurally related active esters derived from 2-phenylpropanoic acid using a combination of quasi-enantiomeric oxazolidin-2-ones is discussed.     

Emission properties of manganese-doped ZnS nanocrystals

We have performed steady-state and time-resolved fluorescence studies on undoped and Mn-doped ZnS nanocrystals with approximately 16 A diameter. While there is no band-edge emission, the intensity of the steady-state blue fluorescence from ZnS surface states decreases upon Mn incorporation, which gives rise to an orange emission. These results show that Mn incorporation competes very effectively with the donor-acceptor surface states for the energy transfer from the electron-hole pair excited across the band gap. In both undoped and doped samples, the time-resolved fluorescence studies establish the presence of a distribution of decay lifetimes possibly due to a number of emission centers in the nanocrystals. A faster short-time decay of the blue emission in the Mn-doped samples compared to that in the undoped sample suggests an additional decay channel for the surface states via an energy transfer from these states to the dopant levels.     

Synthetic Approaches for 15N-Labeled Hyperpolarized Heterocyclic Molecular Imaging Agents for 15N NMR Signal Amplification by Reversible Exchange in Microtesla Magnetic Fields

NMR hyperpolarization techniques enhance nuclear spin polarization by several orders of magnitude resulting in corresponding sensitivity gains. This enormous sensitivity gain enables new applications ranging from studies of small molecules by using high-resolution NMR spectroscopy to real-time metabolic imaging in vivo. Several hyperpolarization techniques exist for hyperpolarization of a large repertoire of nuclear spins, although the ¹³C and ¹⁵N sites of biocompatible agents are the key targets due to their widespread use in biochemical pathways. Moreover, their long T₁ allows hyperpolarized states to be retained for up to tens of minutes. Signal amplification by reversible exchange (SABRE) is a low-cost and ultrafast hyperpolarization technique that has been shown to be versatile for the hyperpolarization of ¹⁵N nuclei. Although large sensitivity gains are enabled by hyperpolarization, ¹⁵N natural abundance is only ∼0.4 %, so isotopic labeling of the molecules to be hyperpolarized is required in order to take full advantage of the hyperpolarized state. Herein, we describe selected advances in the preparation of ¹⁵N-labeled compounds with the primary emphasis on using these compounds for SABRE polarization in microtesla magnetic fields through spontaneous polarization transfer from parahydrogen. Also, these principles can certainly be applied for hyperpolarization of these emerging contrast agents using dynamic nuclear polarization and other techniques.     

Exact Polynomial Solution of $${\cal P}{\cal T}$/Non-${\cal P}{\cal T}$$- Symmetric and Non-Hermitian Modified Woods–Saxon Potential by the Nikiforov–Uvarov Method

Using the Nikiforov–Uvarov (NU) method, the bound state energy eigenvalues and eigenfunctions of the \({\cal P{\cal T}}$-/non-${\cal P}{\cal T}\)-symmetric and non-Hermitian modified Woods–Saxon (WS) model potential with the real and complex-valued energy levels are obtained in terms of the Jacobi polynomials. According to the \({\cal P}{\cal T}\)-symmetric quantum mechanics, we exactly solved the time-independent Schrödinger equation with same potential for the s-states and also for any l-state as well. It is shown that the results are in good agreement with the ones obtained before.