The crystal and molecular structure of 2-(2',4'-dinitrobenzyl)pyridine
The crystal and molecular structure of 2-(2',4'-dinitrobenzyl)pyridine
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2-(2,4-二硝基苯甲基)吡啶的晶体和分子结构
DOI：
10.1107/s0567740868004413
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发表时间：
1968
期刊：
影响因子：
--
通讯作者：
K. Trueblood
中科院分区：
文献类型：
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作者：
K. Seff;K. Trueblood
当用波长 4000 A 或更小的光照射 2-(2',4'-二硝基苯甲基)吡啶 (DNBP, C6H3(NOz)zCH2CsNH4) 的浅黄色晶体时，通过被认为是可逆的互变异构反应产生深蓝色物质。激发形式的半衰期在晶体中为几个小时，但在各种溶剂中仅为几秒或更短。异构 4-取代化合物的晶体没有表现出这么长的半衰期。 DNBP形成单斜晶体，空间群为P2~/c，a0=10.276，b0=15.198，co=7"708/~，//=101.84°，晶胞中有四个分子。利用Cu Kct辐射收集了接近完全积分的Weissenberg填充数据。通过直接法求解结构，并通过全矩阵最小二乘法精修至R= 0.073。两个芳香环平面之间的分子内角度为 1140。亚甲基氢原子与负电性原子最接近的是邻硝基上的氧原子（2.4/°）。该硝基与苄基平面旋转 32°；另一个与苄基平面旋转 12°。这些硝基围绕C-N键进行明显的扭转振荡，振动幅度约为8°和10°。从亚甲基氢原子到负电性原子的最短分子间距离为2.6 A (H.••O)。
When the pale yellow crystals of 2-(2',4'-dinitrobenzyl)pyridine (DNBP, C6H3(NOz)zCH2CsNH4) are irradiated with light of wavelength 4000 A or less, a deep blue substance is produced by what is believed to be a reversible tautomeric reaction. The haft-life of the excited form is several hours in the crystal but only a few seconds, or much less, in various solvents. Crystals of the isomeric 4-substituted compound do not show this long half-life. DNBP forms monoclinic crystals in space group P2~/c, with a0= 10.276, b0= 15.198, co= 7"708/~,//= 101.84 °, and with four molecules in the unit cell. Nearly complete integrated Weissenberg f i l l data were collected with the use of Cu Kct radiation. The structure was solved by direct methods and refined by full-matrix least squares to R= 0.073. Small corrections for molecular libration are included in the final geometry. The intramolecular angle between the planes of the two aromatic rings is 1140. The closest approach of a methylene hydrogen atom to an electronegative atom is intramolecular to an oxygen atom (at 2.4/~) on the o-nitro group. This nitro group is rotated 32 o from the plane of the benzyl ring; the other is twisted 12 o from the benzyl plane. These nitro groups undergo appreciable torsional oscillation about the C-N bonds, with approximate libration amplitudes of 8 ° and 10 °. The shortest intermolecular distance from a methylene hydrogen atom to an electronegative atom is 2.6 A (H. • • O).