Magnetic Properties of Multinuclear Titanium Complexes

定义良好的分子结构的自组装吸引了大量的国际研究努力。虽然这样的工作已经产生了具有新颖光物理（例如光收集）和电化学性能的系统，但令人惊讶的是，在具有新型磁性行为的组件上进行的工作很少。然而，对采用d1， d2或d3金属中心的早期过渡金属多核配合物的磁性行为的了解相对较少。我们发现，通过使用低价钛配合物和吡嗪、嘧啶、4,4 -联吡啶或喹诺啉等双氮分子桥接，可以建立离散的分子结构（分子三角形、正方形和矩形）。分子结构的形成通常伴随着同时发生的原始形成的自由基阴离子的C-C偶联或C-H键激活和脱氢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）以及HATN钛（1,6,7,12,13,18-六氮杂萘）配合物。一般来说，多吡啶基化合物是一类有吸引力的有机配体，已被广泛用于制备超分子物质，这些超分子物质对理解能量和电子转移过程有潜在的帮助。在这个项目中，我们想研究多核低价钛配合物的磁性行为作为分子排列的函数，在homo和混合价配合物中涉及的金属中心的氧化和自旋状态。特别是，根据桥接配体的性质，比较分子正方形和四面体状排列聚集体的磁性能的研究是有意义的。磁性能应与电化学行为、光物理性质以及DFT计算表征的MO情况相关联。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.