Towards hydrogen-rich ionic (NH4)(BH3NH2BH2NH2BH3) and related molecular NH3BH2NH2BH2NH2BH3

Attempts of synthesis of ionic (NH4)(BH3NH2BH2NH2BH3) using metathetical approach resulted in a mixture of the target compound and a partly dehydrogenated molecular NH3BH2NH2BH2NH2BH3 product. The mixed specimen was characterized by NMR and vibrational spectroscopies, and the crystal structure of their cocrystal was solved from powder x-ray diffraction data, and supplemented by theoretical density functional theory calculations. Despite their impressive hydrogen content, and similarly to ammonia borane, both title compounds release hydrogen substantially polluted with borazine, and traces of ammonia and diborane.Comment: 8 pages, 10 Figures, 2 Tables, and electronic supplement of 19 page

Biphasic NMR of Hyperpolarized Suspensions─Real-Time Monitoring of Solute-to-Solid Conversion to Watch Materials Grow

Nuclear magnetic resonance (NMR) spectroscopy is a key method for the determination of molecular structures. Due to its intrinsically high (i.e., atomistic) resolution and versatility, it has found numerous applications for investigating gases, liquids, and solids. However, liquid-state NMR has found little application for suspensions of solid particles as the resonances of such systems are excessively broadened, typically beyond the detection threshold. Herein, we propose a route to overcoming this critical limitation by enhancing the signals of particle suspensions by >3.000-fold using dissolution dynamic nuclear polarization (d-DNP) coupled with rapid solid precipitation. For the proof-of-concept series of experiments, we employed calcium phosphate (CaP) as a model system. By d-DNP, we boosted the signals of phosphate $^{31}$P spins before rapid CaP precipitation inside the NMR spectrometer, leading to the inclusion of the hyperpolarized phosphate into CaP-nucleated solid particles within milliseconds. With our approach, within only 1 s of acquisition time, we obtained spectra of biphasic systems, i.e., micrometer-sized dilute solid CaP particles coexisting with their solution-state precursors. Thus, this work is a step toward real-time characterization of the solid–solution equilibrium. Finally, integrating the hyperpolarized data with molecular dynamics simulations and electron microscopy enabled us to shed light on the CaP formation mechanism in atomistic detail

Accelerated acquisition in pure-shift spectra based on prior knowledge from 1H NMR

Pure-shift NMR enhances the spectral resolution, but the optimal resolutions can only be obtained at the cost of the acquisition time. We propose to accelerate the acquisition using optimised ’burst’ non-uniform sampling schemes[I. E. Ndukwe, A. Shchukina, K. Kazimierczuk, C. P. Butts,ChemComm, 2016, 52, 12769] and then reconstructing the undersampled signal mathematically. Here, we focus on the reliability of this reconstruction depending on the sampling scheme and present a workflow for the sampling optimization. It is ready to be implemented in routine measurements and yields a great improvement of the reconstruction in challenging cases