Magnetic Properties of Multinuclear Titanium Complexes

定义明确的分子结构的自组装吸引了巨大的国际研究努力。虽然这样的工作已经产生了新的物理系统（e。G.光捕获）和电化学性质，但令人惊讶的是，对具有新的磁性行为的组件进行的工作很少。然而，采用d1，d2或d3金属中心的前过渡金属多核配合物的磁行为的知识是比较低的。我们已经发现，离散的分子结构（分子三角形，正方形和矩形）可以通过使用低价钛配合物和桥连双嗪分子如吡嗪，嘧啶，4，4 ′-联吡啶或喹喔啉来构建。分子结构的形成通常伴随着初级形成的自由基阴离子的C-C偶联同时发生或伴随着C-H键活化和分解性C-C偶联，导致有吸引力的三核HAT型（1，4，5，8，9，12-六氮杂苯并菲）以及HATN钛（1，6，7，12，13，18-六氮杂三萘）配合物。通常，多吡啶化合物构成一类有吸引力的有机配体，其已被广泛用于制备对理解能量以及电子转移过程潜在有用的超分子物种。在这个项目中，我们要调查的磁性行为的多核低价钛配合物的功能的分子排列，氧化和自旋状态的金属中心的同质和混合价的配合物。特别是，根据桥连配体的性质，比较分子正方形与四面体状排列聚集体的磁性的研究是令人感兴趣的。磁性应与电化学行为、光物理性质以及通过DFT计算表征的MO情况相关。最终，基于早期过渡金属的可切换系统可能成为可能。

Self-assembly of well defined molecular architectures is attracting a huge international research effort. While such work has yielded systems with novel photophysical (e. g. light-harvesting) and electrochemical properties, surprisingly little work has been carried out on assemblies with novel magnetic behaviour. However, the knowledge of the magnetic behaviour of early transition metal multinuclear complexes employing d1, d2 or d3 metal centers is comparatively low. We have found, that discrete molecular architectures (molecular triangular, square and rectangular) can be build up by using low valent titanium complexes and bridging bisazine molecules like pyrazine, pyrimidine, 4,4¿-bipyridine or quinoxalines. The formation of the molecular architectures is often accompanied by simultaneously occurring C-C couplings of primary formed radical anions or by C-H bond activation and dehydrogenative C-C couplings leading to attractive trinucleare HAT type (1,4,5,8,9,12-hexaazatriphenylene) as well as HATN titanium (1,6,7,12,13,18-hexaazatrinaphthylene) complexes. Generally, polypyridyl compounds constitute an attractive class of organic ligands, which have been widely used for the preparation of supramolecular species which are potentially useful to understand energy as well as electron transfer processes. In this project we want investigate the magnetic behaviour of multinuclear low valent titanium complexes as a function of the molecular arrangement, the oxidation and the spin state of the involved metal centers in homo and mixed valent complexes. Particularly, investigation to compare the magnetic properties of molecular squares with tetrahedral like arranged aggregates depending on the nature of the bridging ligands are of interest. The magnetic properties should be correlated with the electrochemical behaviour, the photophysical properties as well as the MO situation characterized by DFT calculation. At the end switchable systems based on early transition metals could becomes possible.