Strong Intermolecular Ring Current Influence on 1H Chemical Shifts in Two Crystalline Forms of Naproxen: a Combined Solid-State NMR and DFT Study

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• 作者：Elisa Carignani ; Silvia Borsacchi ; Jonathan P. Bradley ; Steven P. Brown ; Marco Geppi
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 29, 2013
• 年：2013
• 卷：117
• 期：34
• 页码：17731-17740
• 全文大小：418K
• 年卷期：v.117,no.34(August 29, 2013)
• ISSN：1932-7455

文摘

The anhydrous crystalline forms of Naproxen [(S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid], (NAPRO-A) and its sodium salt (NAPRO-S), widely used anti-inflammatory drugs, have been investigated by means of 1D and 2D MAS NMR and density functional theory (DFT) based calculations. From calculations, 1D ¹³C CP MAS and ¹H CRAMPS and 2D ¹H鈥?sup>13C MAS-J-HMQC, refocused INEPT, FSLG-HETCOR, and ¹H鈥?sup>1H DQ-CRAMPS solid-state NMR experiments, ¹H and ¹³C resonances have been fully assigned for NAPRO-A and -S. In the case of NAPRO-S, all of the nuclei belonging to the two inequivalent molecules of the asymmetric cell gave rise to distinct signals, which could be completely assigned. Interesting intermolecular ring current effects on ¹H chemical shifts have been experimentally observed for the two samples, even if with significant differences between the two cases. The measured and calculated proton chemical shift values showed a very good agreement for both NAPRO-A and -S, allowing us to correlate the different ring current effects with the crystal structures. The comparison between the proton chemical shifts calculated in the crystal structures and in vacuo allowed us to confirm the mainly intermolecular character of the ring current effects and to quantify them.