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MAS NMR studies of carbon-13 spin exchange in durene

✍ Scribed by Detlef Reichert; Guenter Hempel; Raphy Poupko; Zeev Luz; Zbiegniew Olejniczak; Piotr Tekely

Publisher: Elsevier Science
Year: 1998
Tongue: English
Weight: 444 KB
Volume: 13
Category: Article
ISSN: 0926-2040
DOI: 10.1016/s0926-2040(98)00085-x

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✦ Synopsis

One- (1-D) and two-dimensional (2-D) carbon-13 NMR exchange measurements in powder samples of isotopically normal durene under magic angle spinning (MAS) are reported. The experiments include rotor synchronized 2-D exchange (RS2DE), 1-D magnetization transfer (MT) and time reverse ODESSA (tr-ODESSA). The latter two experiments were performed as a function of several external parameters, including proton decoupling field during mixing time, sample spinning rate and partly, of temperature. The effects of these parameters on the spin exchange induced by spin diffusion and by chemical, or physical exchange, is discussed. Spin exchange between all types of carbons in the durene molecules occurs on the time scale of seconds. From the dependence of the spin exchange rate on the external parameters it is concluded that the process is dominated by spin diffusion. On the basis of these results an upper limit of 10(-16) cm2 s(-1) can be set for the self-diffusion constant in crystalline durene.

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