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Synthesis and Property of Dichroic Photochromism of Bipyridinium Bis(phosphonate)s

双(膦酸)联吡啶的合成及二色性光致变色性能

基本信息

批准号：
12650696
负责人：
NANASAWA Masato
金额：
$ 1.22万
依托单位：
University of Yamanashi
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The viologens, bis-quaternary salts of 4,4'-bipyridine turn to intensive blue radical cations by one-electron by photochemical reaction. With the intention to evaluate the reversible photo-reduction(photochromism), the synthesis and dichroism of viologens with alkanephophonate anions which possess relatively good nucleophilicity and anisotrophic character was investigated. N,N'-dialkyl-4,4'-bipyridinium dihalides were prepared by two steps of Menshutkin reactions with different alkyl halides and their counter ions were exchanged with alkanephosphonates using an anion-exchange resin. ^1H-NMR and elemental analyses indicated that the viologens consist of two phosphonate anions, and protons at pyridinium rings are shifted to higher field, presumably due to low electrostatic interaction with bulky bivalent phophonate anions. This causes that the phosphonate salts are thermally unstable and decompose at relative low temperature without melting.The radical formation by near-UV irradiation is small in organic solvents possessing high ionization potential. The photo-reduction in high-diluted solvents possessing electron-donating property (low IP) mainly proceeds by the ET-reaction from surrounding solvent molecules. The radical cations in glass sandwiched PVC-films were observed by steady state UV-irradiation, and the color of the radical cations persisted for several days. IR-spectra indicate that the photo-induced reduction of solid phosphonate salts proceeds from counter anion within a viologen molecule. When films were prepared by gradually cooling the melted viologen-bisphosphonate with alkanephosphonic acids, the absorption at 530 nm corresponds to the dimeric radical cation increased compared with rapidly cooling ones. While the absorption difference was small, the films of viologen-bisphosphonate salt showed dichroism by the orientation of viologen molecules in anisotropically organized alkanephosphonic acids.

紫精、4，4‘-联吡啶的双季铵盐通过光化学反应以单电子方式转变为强蓝自由基阳离子。为了评价紫精的可逆光还原(光致变色)性能，研究了具有较好亲核性和各向异性的烷基苯酚阴离子紫精的合成及其二色性。用不同的烷基卤化物与N，N‘-二烷基-4，4’-联吡啶经两步反应合成了N，N‘-二烷基-4，4’-联吡啶二卤化物，并用阴离子交换树脂将它们的反离子与烷基膦酸盐交换。1H-核磁共振和元素分析表明，紫精由两个膦酸根组成，吡啶环上的质子向高场移动，这可能是由于它们与大体积二价膦酸根的低静电相互作用所致。这导致了磷酸盐的热不稳定，在相对较低的温度下分解而不熔化。在具有高电离势的有机溶剂中，近紫外光照射产生的自由基很少。在具有给电子性(低IP)的高稀释性溶剂中，光还原主要通过与周围溶剂分子的ET反应进行。用稳态紫外光照射观察到了玻璃夹层聚氯乙烯薄膜中的自由基阳离子，并保持了数天的颜色。红外光谱表明，紫精分子中的反阴离子参与了固体膦盐的光诱导还原反应。当熔融的紫精-双膦酸用烷基膦酸逐渐冷却时，与快速冷却相比，在530 nm处的吸收对应于二聚自由基阳离子的增加。紫精-双膦酸膜的吸收差异不大，但紫精分子在各向异性排列的烷基膦酸中的取向使紫精-双膦酸膜表现出二向色性。