Q.E.COSY: determining sign and size of small deuterium residual quadrupolar couplings using an extended E.COSY principle

Residual quadrupolar couplings contain important structural information comparable with residual dipolar couplings. However, the measurement of sign and size of especially small residual quadrupolar couplings is difficult. Here, we present an extension of the E.COSY principle to spin systems consisting of a Spin 1 coupled to a spin ½ nucleus, which allows the determination of the sign of the quadrupolar coupling of the Spin 1 nucleus relative to the heteronuclear coupling between the spins. The so‐called Q.E.COSY approach is demonstrated with its sign‐sensitivity using variable angle NMR, stretched gels and liquid crystalline phases applied to various CD and CD₃ groups. Especially the sign‐sensitive measurement of residual quadrupolar couplings that remain unresolved in conventional deuterium 1D spectra is shown. Copyright © 2016 John Wiley & Sons, Ltd.     

Nuclear Magnetic Resonance Relaxivities: Investigations of Ultrahigh‐Spin Lanthanide Clusters from 10 MHz to 1.4 GHz

Paramagnetic relaxation enhancement is often explored in magnetic resonance imaging in terms of contrast agents and in biomolecular nuclear magnetic resonance (NMR) spectroscopy for structure determination. New ultrahigh‐spin clusters are investigated with respect to their NMR relaxation properties. As their molecular size and therefore motional correlation times as well as their electronic properties differ significantly from those of conventional contrast agents, questions about a comprehensive characterization arise. The relaxivity was studied by field‐dependent longitudinal and transverse NMR relaxometry of aqueous solutions containing Fe^III₁₀Dy^III₁₀ ultrahigh‐spin clusters (spin ground state 100/2). The high‐field limit was extended to 32.9 T by using a 24 MW resistive magnet and an ultrahigh‐frequency NMR setup. Interesting relaxation dispersions were observed; the relaxivities increase up to the highest available fields, which indicates a complex interplay of electronic and molecular correlation times.     

The Photoredox‐Catalyzed Meerwein Addition Reaction: Intermolecular Amino‐Arylation of Alkenes

A variety of amides are efficiently accessible under mild conditions by intermolecular amino‐arylation using a photo Meerwein addition with visible light. The reaction has a broad substrate scope, tolerates a large range of functional groups, and was applied to the synthesis of a 3‐aryl‐3,4‐dihydroisoquinoline.     

A Study of the 3,3,3‐Trinitropropyl Unit as a Potential Energetic Building Block

Compared with the well‐established 2,2,2‐trinitroethyl group in the chemistry of energetic materials, the 3,3,3‐trinitropropyl group is less investigated regarding its chemical and energetic properties. Thus, investigations on the syntheses of several compounds containing the 3,3,3‐trinitropropyl group were performed and their properties compared with the 2,2,2‐trinitroethyl group. All materials were thoroughly characterized, including single‐crystal X‐ray diffraction studies. The thermal stabilities were examined using differential thermal analysis (DSC) and the sensitivities towards impact, friction, and electrostatic discharge were tested using a drop hammer, a friction tester, and an electrical discharge device. The energies of formation were calculated and several detonation parameters such as the velocity of detonation and the propulsion performance were estimated with the program package EXPLO5.     

Polymorphism - integrated approach from high-throughput screening to crystallization optimization

Crystal structure (polymorphism) as well as crystal shape (morphology) and size have a huge practical and commercial impact on active substances all the way from research to manufacture of the final product. For an optimal development process, it is important to have an integrated approach to these issues ranging from a systematic polymorphism screening to a controlled scale-up of the crystallization process. The polymorphism program has to be tailored according to the development stage. Particularly suitable for an early development stage is a high-throughput polymorphism screening, which is the basis for a more thorough investigation if the product proceeds further in development. Such a comprehensive polymorphism investigation involves further crystallization experiments and extensive physicochemical characterization of the various forms. In this article the high-throughput polymorphism screening method that we have developed is described. Using carbamazepine as an example, the power of this high-throughput polymorphism screening system is demonstrated. Not only were all published forms found, but also new forms were identified. In the second part of the article, important considerations for crystallization optimization are discussed, again using the example of carbamazepine. This revised version was published online in July 2006 with corrections to the Cover Date.