Structure, Motion, and Exchange Coupling of 15NO2/15NO2 Radical Pairs Occupying Adjacent Solvent Cavities of α-HNIW, a Nitramine Hydrate
| Autor: | J. Michael McBride, Lev R. Ryzhkov† and |
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| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 119:4826-4833 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja9631615 |
| Popis: | Low-temperature photolysis of α-HNIW (2,4,6,8,10,12-hexanitrohexaazatetracyclo[5.5.05,9.03,11]dodecane) generated three 15NO2/15NO2 radical pairs that were studied by single-crystal electron paramagnetic resonance spectroscopy at 80 K. In two of the pairs, A and B, the two NO2 molecules occupy solvent cavities that are related by unit translation along the a-axis of the α-HNIW unit cell (radical pair separations of 9.26 and 9.67 A). In the third pair, C, they occupy cavities related by translation along the b-axis (∼13 A). Pair formation was highly specific since no pairs were trapped in cavities related by the b-glide (8.14 A). All three observed pairs survived annealing to 215 K, but from 220 to 294 K they decayed, one by one, without interconverting or separating to isolated radicals. Positive and negative exchange couplings as large as 0.004 cm-1 were estimated through approximate simulation of the position and intensity of transitions involving the nuclear states with hyperfine-induced So−To mixing. ... |
| Databáze: | OpenAIRE |
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