【作者】 吴舒婷；

【导师】 郑兰荪； 龙腊生； 黄荣彬； 林文斌；

【作者基本信息】 厦门大学 ， 无机化学， 2008， 博士

【摘要】 1989年Richard Robson报导的第一例金刚石结构配位聚合物[Cu^Ⅰ（C（C₆H₄CN）₄）]ⁿ⁺以来,配位聚合物在配位化学、物理化学、固态化学、化学拓扑学等多个领域成为广泛研究的热点。以配位键为主、分子间作用力或主客体相互作用为辅的组装方式赋予了配位聚合物具有可调控性强、结构丰富多样、性质可控空间大等特点。然而该组装方式也使得配位聚合物的结构调控变数很大,往往同个体系可具有多种结构、不同的对称性。本论文正是在此背景下,以手性配位聚合物的对称性破缺为目标,从配位聚合物的结构调控出发,逐步掌握其组装机制,再以此为设计依据,研究解决手性配位聚合物的构筑及对称性破缺问题。首先,选择二元配体体系——Cu^Ⅱ/苯甲酸/4,4’-联吡啶为研究对象,调节反应体系pH值得到了从零维到二维的化合物1-5,反映出从简单配合物到复杂网络结构的配位聚合组装进程受控于pH值调节的配体配位能力。第二,选择类似的二元配体体系——Cu^Ⅱ/邻苯二甲酸（o-pht）/咪唑（Him）为研究体系,该体系较之体系Ⅰ增加了桥联配体的自由度,用于考察配位聚合过程中亚单元的组装机制。固定反应体系pH值,得到一维亚单元[Cu（Him）₂（o-pht）]_n。在此基础上,通过调节二元溶剂——乙醇/水的比例,得到了从一维到二维、从中心对称到非心对称的化合物6-8·2H₂O,反映出二元溶剂对化合物维度及对称性的选择作用。此外,对上述三个化合物之间的结构关系、转化关系等进行了系统研究,发现一维结构7可脱去一个水分子转化为二维结构8·2H₂O,后者可在保持单晶形貌透明度的前提下脱去所有水分子转为8,完成单晶-单晶的转化,并体现出磁性质从反铁磁-铁磁-反铁磁的有趣变化。第三,与2,2’-联二萘酚的轴手性相类比,2,2’-联二苯酚仅具有潜在的轴手性,由于2,2’-位易出现的无序现象极易发生内消旋化。因此,本章节用2,2’-位修饰与未修饰的2,2’-联二苯酚基四羧酸配体与二价铜离子、锌离子反应,构筑三维大孔配位聚合物9-12。然而,由于9-11为低密度高孔容率结构,2,2’-联二苯酚位的无序问题并未得到解决。化合物12中,由于2,2’-位取代冠醚与水解反应引入的钠离子配位得以克服无序性,仅实现了局部的对称性破缺,总体体现为外消旋化合物。另外,该章节还在体系中引入手性小分子——反式-1,2-环己二胺与2,2’-位乙氧基取代的四羧酸配体反应,得化合物13、14,考察氢键组装的超分子结构中手性小分子对整体氢键结构的对称性作用。在第三步尝试打破2,2’-联二苯酚的内消旋化并未取得很好的效果后,本论文结合前两步有关配位聚合物结构及对称性调控的实验结果,选择二元配体体系——Cu^Ⅱ/丁二酸/4,4’-联吡啶为研究对象,在固定二元溶剂乙醇/水比例条件下,调节体系pH值,得到三维手性配位聚合物15及三维外消旋配位聚合物16。其中15为单一手性配位聚合物,其单晶具有光学活性,但整体产物易出现外消旋化。因此,本论文对15的反应及结晶进程进行了系统考察,发现氨水浓度∝pH值∝（反应速度）^-1∝（结晶速度）^-1。因此,在反应体系中加入过量氨水,通过氨水与其他配体的竞争配位作用,有效控制了反应速度,从而减少结晶体系的初级成核数。根据统计分布规律,初级成核的手性分布与成核数目有着极其微妙的关系。本论文正是依据此关系,打破自然的统计分布规律,实现初级成核的对称性破缺。再通过二级成核的手性自催化作用,实现结晶产物的对称性破缺。这是首例化学方法成功实现配位聚合物的手性对称性破缺。更多还原

【Abstract】 Since Richard Robson synthesized and described the first coordination polymer[Cu^Ⅰ（C（C₆H₄CN）₄）]ⁿ⁺ in 1989,the research of coordination polymers have attracted numerous attention in the field of coordination chemistry,physical chemistry, solid state chemistry,chemical topology,etc.Coordination polymers were mainly assembled with coordination bonds,and some molecular interactions or host-guest interactions as well.The corresponding bond energies are relatively low,compared to the covalent bonds,which makes coordination polymers have incredible large amount of architectures and flexible framework.In that case,various structures might easily exist under subtle change of synthesis condition.Herein,the subject of this dissertation is to fully understand the intrinsic assemble of coordination polymers, so as to construct chiral coordination polymers and realized the chiral symmetry breaking.First of all,the role of pH in binary ligands system has been studied.In the Cu^Ⅱ/benzoate/4,4’-bipyridine system,five compounds 1-5 ranged from 0D to 2D structures were obtained by merely increasing the pH value from 5.5 to 8.0.By analyzing the details of the structure,the coordination ability of 4,4’-bipyridine which is controlled by pH value is the key of assemble mechanism.Secondly,the role of solvent in similar binary ligands system was taken into consideration.Instead of 4,4’-bipyridine,the o-phthalic acid was chosen to increase the freedom of connectivity.In the Cu^Ⅱ/ o-phthalate/imidazole system,the 1D substructure[Cu（Him）₂（o-pht）]_n was obtained by constraining the reaction pH value. Based on the substructure,1D coordination polymers 6,7 were generated in binary solvents EtOH/H₂O,while 2D coordination polymer 8·2H₂O was obtained in pure water.Furthermore,adjusting the proportion of the binary solvent could generate centrosymmetric 6 and acentric 7,showing the solvent-dependent symmetric assemble. Thirdly,new tetracarboxylate ligands with dihydroxyl（L₁） and crown ether （L₂） functionalities have been synthesized and treated with Cu^Ⅱ,Zn^Ⅱions and diaminocyclohexane to generate 3D coordination polymers 9-12 and supramolecular 13,14.Considering the potential axial chirality of 2,2’-biphenol unit, coordination-bonded assemble as well as chiral induction were both tried to realize the structural symmetry breaking.However,the 2,2’-biphenol unit are easily disorded,which always result in centrosymmetric structure.Based on the three steps illustrated above,Cu^Ⅱ/succinate/4,4’-bipyridine system was chosen to construct 3D chiral coordination polymers.By adjusting the reaction pH value,two phases were obtained in binary solvent system:enantiomeric helix-based structure 15,and racemic pillared structure 16.Further investigation of the chiral resolution over 15 revealed a relationship:ammonia concentration∝pH value∝（reaction speed）^-1∝（crystallization speed）^-1.Thus,excess ammonia was added into the system to compete with the binary ligands,in order to slow down the reaction speed and crystallization speed.In that case,the primary nucleation was greatly limited.On the other hand,the statistical fluctuation of coin flipping shows that flipping a coin many times naturally resulted in 50-50 ratio of heads and tails, while flipping a coin once resulted in a single outcome,either a head of a tail.So, would It be nice if isolating a single-enantiomer form of 15 were as simple as flipping a coin? When the primary nucleation was greatly limited by simply adding excess ammonia,it is easy to make it happen! For more details,please read the whole story in the dissertation.更多还原