Iridium α-carboxyimine complexes hyperpolarized with parahydrogen exist in nuclear singlet states before conversion into iridium carbonates

The formation and hyperpolarization of an [Ir(H)2(amine)(IMes)(η2-imine)]Cl complex that can be created in a hyperpolarized nuclear singlet state is reported. These complexes are formed when an equilibrium mixture of pyruvate, amine (benzylamine or phenylethylamine), and the corresponding imine condensation product, react with preformed [Ir(H)2(amine)3(IMes)]Cl. These iridium -carboxyimine complexes exist as two regioisomers differentiated by the position of amine. When examined with para-hydrogen the hydride resonances of the isomer with amine trans to hydride become strongly hyperpolarized. The initial hydride singlet states readily transfer to the corresponding 13C2 state in the labelled imine and exhibit magnetic state lifetimes of up to 11 seconds. Their 13C signals have been detected with up to 420 fold signal gains at 9.4 T. On a longer timescale, and in the absence of H2, further reaction leads to the formation of neutral carbonate containing [Ir(amine)(η2-CO3)(IMes)(η2-imine)]. Complexes are characterized by, IR, MS, NMR and X-ray diffraction

SABRE polarized low field rare-spin spectroscopy

High-field nuclear magnetic resonance (NMR) spectroscopy is an indispensable technique for identification and characterization of chemicals and biomolecular structures. In the vast majority of NMR experiments, nuclear spin polarization arises from thermalization in multi-Tesla magnetic fields produced by superconducting magnets. In contrast, NMR instruments operating at low magnetic fields are emerging as a compact, inexpensive, and highly accessible alternative but suffer from low thermal polarization at a low field strength and consequently a low signal. However, certain hyperpolarization techniques create high polarization levels on target molecules independent of magnetic fields, giving low-field NMR a significant sensitivity boost. In this study, SABRE (Signal Amplification By Reversible Exchange) was combined with high homogeneity electromagnets operating at mT fields, enabling high resolution 1H, 13C, 15N, and 19F spectra to be detected with a single scan at magnetic fields between 1 mT and 10 mT. Chemical specificity is attained at mT magnetic fields with complex, highly resolved spectra. Most spectra are in the strong coupling regime where J-couplings are on the order of chemical shift differences. The spectra and the hyperpolarization spin dynamics are simulated with SPINACH. The simulations start from the parahydrogen singlet in the bound complex and include both chemical exchange and spin evolution at these mT fields. The simulations qualitatively match the experimental spectra and are used to identify the spin order terms formed during mT SABRE. The combination of low field NMR instruments with SABRE polarization results in sensitive measurements, even for rare spins with low gyromagnetic ratios at low magnetic fields.I. INTRODUCTIO

Nutzung der Erkenntnisse der marinen Oekosystemforschung fuer die Antarktis-Umweltschutzaufgaben Endbericht mit Anhang

This study focused on describing and evaluating the impacts of human activities on the Antarctic marine environment including marine birds and mammals (flying seabirds and penguins, seals and whales). The evaluation of impacts was carried out in accordance with the requirements of the German 'Umweltschutzprotokoll-Ausfuehrungsgesetz' ('AUG') which is the national implementation act to the Protocol on Environmental Protection of 4 October 1991 to the Antarctic Treaty. The report covers scientific activities (impact of methods used in biological and other research disciplines) and their logistical support (impact of research vessels, boats and aircraft; construction, operation and extension of scientific stations; field camps) as well as the impact of ship-based and airborne tourism (cruise ships, yaughts, aviation). We elaborated definitions of the undefined legal terms which are used in Paragraph 4 (3) 1-3 AUG to describe the degree of impact on the Antarctic environment (less than minor or transitory; minor or transitory; more than minor or transitory). Criteria and examples are given to illustrate how these definitions can be applied in the permitting process. In Paragraph 3 (4) 1-7 AUG various terms are used to describe impacts on the Antarctic environment which must not occur if an activity is to be permitted. We summarized these expressions under the German term 'erheblich' (in English: 'severe'). Furthermore, a classification scheme was worked out in line with the requirements of Paragraph 17 AUG for the evaluation of impacts of scientific methods on Antarctic mammals and birds (cf. Paragraph 17 AUG). This scheme was based on the results of the workshop 'Human Impact on Antarctic Mammals and Birds' held at our Institute. A detailed protocol of the course of discussions and workshop results is given in Appendix 2. Other aspects covered in this report include a summary of the state of scientific knowledge of the main components of the Antarctic marine environment comprising the results of a literature study on the subject of harmful substances. Case studies illustrate how to evaluate scientific research programms, and research needs are specified. Furthermore, recommendations for environmentally safe visitor behaviour and scientific work as well as suggestions and recommendations for the implementation of the AUG are given. The report is supplemented by an extensive bibliography and an index. (orig.)Published in two volumes. Also published as UBA-Texte 83/99SIGLEAvailable from TIB Hannover: RN 8908(99-113,1): RN 8908(99-113,2) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekUmweltbundesamt, Berlin (Germany); Bundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

External high-Quality-factor Resonator tunes up nuclear magnetic resonance

The development of powerful sensors for the detection of weak electromagnetic fields is crucial for many spectroscopic applications, in particular for nuclear magnetic resonance (NMR). Here, we present a comprehensive theoretical model for boosting the NMR signal-to-noise ratio, validated by liquid-state 1H, 129Xe and 6Li NMR experiments at low frequencies, using an external resonator with a high quality-factor combined with a low-quality-factor input coil. In addition to an enhanced signal-to-noise ratio, this approach exhibits striking features such as a high degree of flexibility with respect to input coil parameters and a square-root dependence on the sample volume, and signifies an important step towards compact NMR spectroscopy at low frequencies with small and large coils

Para-hydrogen raser delivers sub-millihertz resolution in nuclear magnetic resonance

The precision of nuclear magnetic resonance spectroscopy1 (NMR) is limited by the signal-to-noise ratio, the measurement time Tm and the linewidth Δν = 1/(πT2). Overcoming the T 2 limit is possible if the nuclear spins of a molecule emit continuous radio waves. Lasers and masers are self-organized systems which emit coherent radiation in the optical and micro-wave regime. Both are based on creating a population inversion of specific energy states. Here we show continuous oscillations of proton spins of organic molecules in the radiofrequency regime (raser5). We achieve this by coupling a population inversion created through signal amplification by reversible exchange (SABRE) to a high-quality-factor resonator. For the case of 15N labelled molecules, we observe multi-mode raser activity, which reports different spin quantum states. The corresponding 1H-15N J-coupled NMR spectra exhibit unprecedented sub-millihertz resolution and can be explained assuming two-spin ordered quantum states. Our findings demonstrate a substantial improvement in the frequency resolution of NMR