固体状態のNMR,X線 difraktion,および水素結合構造とピラゾール-4-カルボキシル酸鎖のダイナミクスの初期計算研究
C Foces-Foces1, A Echevarría, N Jagerovic
1Departamento de Cristalografía, Instituto de Química-Física 'Rocasolano', CSIC, Serrano, 119, E-28006 Madrid, Spain.
Journal of the American Chemical Society
|August 9, 2001
まとめ
固体であるピラゾル-4-カルボキシル酸は,その結晶構造にダイナミックな陽子乱れを示し,低温または無形な段階では陽子秩序に移行します. この行動は,水素結合内の素早い陽子移動によって引き起こされる.
科学分野:
- 固体化学 固体化学
- 分子構造と分子ダイナミクス
- 水素結合は水素結合である.
背景:
- ピラゾール-4-カルボキシル酸 (1) は,複雑な水素結合相互作用の可能性のある分子です.
- 陽子の乱れを理解することは,物質の性質と反応性を予測するために不可欠です.
研究 の 目的:
- 固体ピラゾール-4-カルボキシル酸における陽子の構造的および動的振る舞いを解明する.
- 結晶構造,水素結合,陽子の移動性との相互作用を調査する.
主な方法:
- 高解像度固体窒素-15 交叉偏振 マジック・アングル・スピニング (15N CMAS) 核磁共振 (NMR) スペクトロスコピー.
- 変数温度 (295 K と 150 K) でのX線結晶学.
- オリゴーマーに関する初期量子化学計算.
主要な成果:
- X線結晶学では,周期的水素結合と陽子の乱れを持つ準線形リボンが明らかになったが,動的と静的な乱れを区別することができなかった.
- NMRは,室温でのダイナミックな陽子の乱れを示し,それは水素結合間の急速な陽子の移転によって特徴付けられています.
- 低温のNMR研究では,低温で陽子が局所化し,急速な降水時に陽子の順序を示す無形相を持つ,乱雑性-秩序の移行を示した.
結論:
- この研究は,ピラゾール-4-カルボキシル酸のダイナミックな陽子障害を明らかにし,それは温度に依存する水素結合内の急速な陽子転送によって引き起こされる.
- Ab initio計算では,X線データと互換性のある波状のリボン構造がサポートされており,鎖の動きが陽子移動を促進します.
- アモルフな段階は乱雑な構造を示し,曲線と波状のモチーフの組み合わせを示唆しています.
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