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J Phys Chem A. 2009 Apr 2;113(13):3197-201. doi: 10.1021/jp809267y.

First calculations of 15N-15N J values and new calculations of chemical shifts for high nitrogen systems: a comment on the long search for HN5 and its pentazole anion.

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  • 1Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, USA.


In the potential solution observation of the long-sought-after pentazole anion (N(5)(-)), the principal experimental tool used for detection is NMR. However, in two experiments, very different conclusions were reached. To assist in the interpretation, we report predictive level coupled-cluster results for the spin-spin coupling constants and chemical shifts for all of the key species, which include NO(3)(-), N(5)(-), HN(5), N(3)(-), and MeOC(6)H(5)N(3). In the case of the shifts, an empirical estimate based on the molecule polarity enables comparison of gas-phase and observed values with expected error bars of approximately +/-10 ppm. For the scalar couplings, the evidence is that the solution effects are modest, enabling the gas-phase values (with error bars are approximately +/-5 Hz) to be accurate. The latter supports the observation of centrally (15)N labeled N(3)(-) in the cerium(IV) ammonium nitrate (CAN) solution which could only occur if the pentazole anion had been created in the experiment, yet with too short a lifetime to be observed in NMR.

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