The Preparation and Study of Novel Ligand Systems

休斯顿大学化学系的兰道夫·P·图梅尔教授在有机化学和高分子化学项目的支持下，研究了新型配体体系的制备和性质。Thummel教授探索了双齿配体中不对称取代的立体化学后果，重点研究了这种取代在Ru(II)的三(联吡啶)络合物的面状和经面非对映异构体形成中的空间和电子效应。通过合成一系列与9-(二-2‘-吡啶)亚甲基荧烯相关的配体，Thummel教授正在研究长寿命光激发态的产生，这些配体在光诱导的金属到配体电荷转移后围绕中心pi键旋转，从而形成内部返回基态的障碍。相关的配体可以评估配体的氧化状态对两个结合金属离子之间电子通讯的影响，而基于芘的配体的络合物提供了观察室温发射的可能性。金属离子的物理和化学性质可以通过在分子结构中捕获它们来显著改变，这种分子结构旨在影响所选的性质。休斯顿大学化学系的兰道夫·P·图梅尔教授得到了有机化学和高分子化学计划的支持，他研究了分子的合成和研究，这些分子旨在影响金属络合物与光相互作用产生的化学过程。这种光过程导致电子从金属转移到支持的分子结构，通过设计这种结构在这种电子转移时经历显著的几何变化，Thummel教授试图稳定光诱导的“激发态”。相关研究允许评估连接两个金属离子的分子基团性质的改变对两个金属离子之间电子通信的影响。这些研究涉及有关光致电子转移的基本问题，并与从阳光中获取能量直接相关。

With the support of the Organic and Macromolecular Chemistry Program, Professor Randolph P. Thummel, of the Department of Chemistry at the University of Houston, investigates the preparation and properties of novel ligand systems. Professor Thummel explores the stereochemical consequences of unsymmetrical substitution within bidentate ligands, focusing on the steric and electronic effects of such substitution in the formation of facial and meridional diastereomers of tris(bipyridyl) complexes of ruthenium(II). Through the synthesis of a series of ligands related to 9-(di-2'-pyridyl)methylenefluorene, designed to undergo rotation about the central pi bond following photoinduced metal-to-ligand charge transfer and thereby present a barrier to internal return to the ground state, Professor Thummel is investigating the generation of long-lived photoexcited states. Related ligands permit assessment of the impact of ligand oxidation state on electronic communication between two bound metal ions, while complexes of pyrene-based ligands offer the possibility to observe room temperature emission. The physical and chemical properties of metal ions may be altered dramatically by capturing them within a molecular structure designed to impact chosen properties. Professor Randolph P. Thummel, of the Department of Chemistry at the University of Houston, is supported by the Organic and Macromolecular Chemistry Program for his investigations of the synthesis and study of molecules designed to affect the chemical processes resulting from the interaction of their metal complexes with light. Such photoprocesses lead to the transfer of an electron from the metal to the supporting molecular structure, and by designing this structure to undergo a significant change in geometry upon such electron transfer, Professor Thummel attempts to stabilize the photoinduced `excited state.` Related studies permit assessment of the effect on the electronic communication between two metal ions of a change in the nature of a molecular grouping which bridges them. These studies address fundamental issues regarding photoinduced electron transfer and are directly related to the harvesting of energy from sunlight.