Studies on the anti-aromaticity and molecular recognition properties of luminescent heterocyclic compounds related to bioluminescence

3，7-二氢咪唑并[1，2-a]吡嗪-3-酮(咪唑并吡嗪酮)环体系是从海洋发光生物中分离得到的一种重要的生物发光底物杂环结构，具有化学发光、荧光和溶剂变色等性质。为了为咪唑并吡嗪酮类化合物的生物发光化学和生物成像科学奠定基础，本研究旨在建立咪唑并吡嗪酮类化合物的基本物理性质。(1)首先，通过X射线结晶学、UV/Vis吸收光谱和分子轨道计算研究了简单咪唑并吡嗪酮类化合物的基本物理性质。晶体结构分析表明，咪唑并吡嗪酮π-体系具有平面环状结构和特征键长变化，表明π-体系具有Zwitter型离子共振结构，从而提高了芳香性。吸收光谱测量结果表明，溶剂变色的起源是与氢键供体溶剂分子的氢键相互作用。这些观察结果通过MO计算得到了一致的评估。(2)研究了苯基取代对咪唑并吡嗪酮类化合物物理性质的影响。结果表明，在C8位引入苯基可以有效地改变咪唑并吡嗪酮π-体系的性质，成功地扩展了该体系的显色范围。(3)确定了咪唑并吡嗪酮类化合物与金属离子形成络合物的能力。咪唑并吡嗪酮类化合物的光谱性质因络合物的形成而不同，光谱变化的趋势取决于金属离子的Lewis酸度。因此，咪唑并吡嗪酮衍生物可用作金属离子的Lewis酸性的指示剂。

3,7-Dihydroimidazo[1,2-a]pyrazin-3-one (imidazopyrazinone) ring system is an important heterocyclic structure for bioluminescent substrates isolated from marine luminescent organisms and has various useful characteristics, such as chemiluminescent, fluorescent, and solvatochromic properties. To make the bases of bioluminescence chemistry and biological imaging science of imidazopyrazinone derivatives, this research project aims to establish the fundamental physical properties of imidazopyrazinone derivatives. (1) At first, the fundamental physical properties of simple imidazopyrazinone derivatives were investigated by X-ray crystallography, UV/vis absorption spectroscopy, and MO calculations. The crystal structural analyses showed that the imidazopyrazinone π-system had a planar ring structure and characteristic bond length alternations, indicating that the π-system has a character of a zwitter-ionic resonance structure to increase aromaticity. The results of absorption spectral measurements clarified that the origin of solvatochromism was hydrogen-bonding interactions with hydrogen-bond donor solvent molecules. These observations were consistently evaluated by MO calculations. (2) Secondly, the phenyl-substituent effect on the physical property of imidazopyrazinone derivatives was investigated. The result indicated that an introduction of phenyl group at C8 caused an efficient change of the property of the imidazopyrazinone π-system, and it was succeeded in to expand the color range of the solvatochromism. (3) Finally, the ability of imidazopyrazinone derivatives to make a complex with a metal ion has been established. The spectroscopic character of an imidazopyrazinone derivative was varied by complex formation, and the tendency of the spectral change was dependent upon a Lewis acidity of a metal ion. Therefore, imidazopyrazinone derivatives are applicable as an indicator of a Lewis acidity of a metal ion.