权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Unusual Bond Length of Organic Molecules in Crystals

晶体中有机分子的异常键长

基本信息

批准号：
06640680
负责人：
OGAWA Keiichiro
金额：
$ 1.41万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Recently we found an unusual shortening of the ethlene bond and a significant temperature dependence of the molecular structure for the X-ray structures of (E)-stilbenes. This phenomenon was ascribed to an artifact that originates from the large amplitude torsional motion of the C-Ph bonds. The puroposes of this project are to get further evidence for our interpretation reported previously and to the generality of the phenomenon.X-ray crystallographic analyzes of the compound having the (E)-stilbene skeleton in which the internal rotation of the C-Ph bonds is severely restricted by the alkylene chains. The observed ethylene bond length is 1.35-1.36 @90, independent of the temperature, which agrees well with the length estimated from the molecular mechanics calculatiojns. The results make a sharp contrast with those for ordinary (E)-stilbenes and strongly support the interpretation that unusual short ethlene bond in the X-ray structures of (E)-stilbenes is an artifact which originates from the large-amplitude torsional motion of the C-Ph bonds in crystals. The true length of the ethlene bond in (E)-stilbenes is safely estimated to be 1.35-1.36 @90.Crystal structures of 1,2-diphenylethanes were determined at different temperatures by X-ray diffraction. The observed length of the central C-C bond of 1,2-diphenylethane at 240 K (1,506 (5) @90) appears to be considerably shorter than the standard value of a C (sp^3)-C (sp^3) bond 1,541 (3) @90. The observed length, however, substantially increases with lowering the temperature. It is concluded that the anomaly in the ethane bond length of 1,2-diphenylethanes, which has been attempted to be explained in terms of various electronic effects, is an artifact caused by the torsional vibration of the C-Ph bonds in crystals.

最近，我们发现 (E)-二苯乙烯的 X 射线结构的乙烯键异常缩短，并且分子结构具有显着的温度依赖性。这种现象被归因于源自 C-Ph 键大幅扭转运动的伪影。该项目的目的是为我们之前报道的解释以及该现象的普遍性获得进一步的证据。对具有 (E)-二苯乙烯骨架的化合物进行 X 射线晶体学分析，其中 C-Ph 键的内旋受到亚烷基链的严格限制。观察到的乙烯键长为 1.35-1.36 @90，与温度无关，这与分子力学计算估计的长度非常吻合。该结果与普通 (E)-二苯乙烯的结果形成鲜明对比，有力地支持了这样的解释：(E)-二苯乙烯的 X 射线结构中不寻常的短乙烯键是源自晶体中 C-Ph 键的大幅扭转运动的伪影。 (E)-二苯乙烯中乙烯键的真实长度被安全地估计为 1.35-1.36 @90。1,2-二苯基乙烷的晶体结构在不同温度下通过 X 射线衍射测定。在 240 K 下观察到的 1,2-二苯基乙烷中心 C-C 键长度 (1,506 (5) @90) 似乎比 C (sp^3)-C (sp^3) 键 1,541 (3) @90 的标准值短得多。然而，观察到的长度随着温度的降低而显着增加。结论是，1,2-二苯基乙烷的乙烷键长异常（已尝试用各种电子效应来解释）是由晶体中 C-Ph 键的扭转振动引起的人为因素。