中心对称的对羟基苯甲酸-尿素超分子晶体的SHG效应  

The Effect of Centrosymmetric Supermolecular Crystal of p- Hydroxybenzonic Acid/Urea

作　　者：郭 放[1] 魏春生[1] 郭文生[1] 

机构地区：[1]辽宁大学化学科学与工程学院,辽宁沈阳110036

出　　处：《辽宁大学学报（自然科学版）》2002年第2期103-107,共5页Journal of Liaoning University：Natural Sciences Edition

基　　金：国家自然科学基金资助项目(69778022);辽宁省自然科学基金资助项目(9810301001)

摘　　要：利用超分子组装方法获得对羟基苯甲酸（1）和尿素以及对硝基苯酚（2）和三乙烯二胺的超分子组装晶体.经X射线衍射测定单晶结构,前者晶体为中心对称结构,空间群为p2/n;后者为非中心对称结构,空间群为p21.经锁模皮秒激光器测试,前者呈现SHG效应,后者却几乎不呈现SHG效应.在超分子晶格中,前者β值分子为尿素,受到共存的对羟基苯甲酸分子的作用,从而改变了它在晶格中的彼此间的距离,使之能够部分地保持各自独立的超极化分张量,而呈现SHG效应;后者β值分子为对硝基苯酚,由于它在晶格中的紧密层状堆积,导致偶极抵消,超级化分张量几乎为零,SHG效应很小.Supermolecular crystals of urea/p-hydroxybenzonic acid and p-nitrophenol/DABCO are obtained by molecular assembly. The results determined by X-ray single crystal diffraction show that the former spermolecular crystal is centrosymmetric structure with space group p2/n, while the latter is noncentrosymmetric stucture with space group p21. The relative intensity of the green light from the inclusion crystal powders compared to that of urea powder sample is measured by pico-sec-ond Nd: YAG laser. The measured results show the former intensity is equal to that of urea, while the latter intensity is almost zero. In the former supermolecular crystal, β value urea molecules re-stricted by coexisting p-hydroxybenzonic acid change the distance between the molecules, so the in-teraction between ground-state dipole moment of urea molecules is weakened. Thus supermolecular crystals can remain partial hyperpoarizability tensor component independently and exhibit SHG ef-fect. Because of the close layer architecture of β value p-nitrophenol molecules in the latter crystal, dipole moments of p-nitrophenol are almost counteracted each other, so the hyperpolarizability tensor becomes zero.

关 键 词：中心对称结构 对羟基苯甲酸 尿素 超分子组装晶体 SHG效应 硝基苯酚 二阶非线性光学 

分 类 号：O734.1[理学—晶体学] O641.3