【作者】 王鑫；

【导师】 徐斌；

【作者基本信息】 吉林大学 ， 有机化学， 2024， 硕士

【摘要】 光开关分子是在某种波长的光照射下使其状态和结构发生可逆变化,并且这两种异构体可以长时间保持稳定。荧光光开关分子不但具有光开关特性,还伴随荧光的出现和消失。荧光光开关分子无论是在“开”还是“关”的状态下都展示出不同的颜色和光谱的区别。因此在众多领域中表现出非常出色的应用价值,例如光电器件、超分辨成像、防伪和生物成像等。在传统的光开关分子中,螺吡喃(spiropyran,SP)材料属于研究较早的一类光开关,并且其相关报道文献也是最多的。一般情况下,螺吡喃在外界刺激下由无色变为蓝紫色,并伴随明亮的红色荧光出现,在光谱中也表现出明显变化。然而早期螺吡喃在紫外光刺激后,只在单分子状态(溶液状态)展现出红色荧光。因为螺吡喃在紫外光照射下转变为有荧光的部花菁异构体时分子结构发生翻转,这需要非常大的异构空间。溶液状态下较远的分子间距离满足其实现光致异构的条件。但是螺吡喃在聚集的固体状态下,分子之间紧密堆积,无法发生异构反应,因此很难在固体状态下实现其荧光光开关的性质,这对螺吡喃固态光刺激响应性质的研究产生了很大的阻碍。为了解决螺吡喃无法实现固态荧光光开关的难题并拓展更多体系的螺吡喃光开关材料,本论文主要研究内容主要如下:1.基于柔性链调控策略探究螺吡喃固态光致异构我们通过分子设计来解决螺吡喃无法实现固态光致异构的难题,使柔性基团取代螺吡喃衍生物,并命名为SP1。与此同时我们对SP1的光物理特征进行探究,发现SP1在聚集态拥有螺吡喃典型的光致变色和荧光切换的功能。为了探究SP1在聚集态下的堆积状态和结构,我们通过溶剂蒸发法生长出了SP1的晶体,得到的晶体也同样能实现荧光光开关功能。为了揭示SP1晶体能够实现光开关性质的原因,我们对无法实现固态光致异构的SP-COOH和SP1晶体结构和分子间相互作用量子化学计算的结果进行分析。由于SP-COOH分子中存在羧基,使分子内和分子间有较强的相互作用,限制分子的异构化行为。SP1分子的酯基替代羧基后,酯基增大分子间距离,减弱分子间相互作用力,使聚集态的分子堆积松散,这为SP1的固态光致异构过程提供更大的自由空间。2.螺吡喃固态可逆双荧光光开关的设计及研究基于前一章工作中的SP1分子,设计了本章工作中的SP-AQ分子。我们利用酯链把SP分子和蒽醌(Anthraquinone,AQ)分子连接在一起,在固态的情况下实现了光诱导可逆双色荧光切换。SP-AQ在紫外光和可见光的交替照射下,可以进行红色荧光和绿色荧光之间的转换。详细的光物理表征表明,SP-AQ的初始绿色荧光光谱与AQ分子本体荧光光谱类似,因此我们推测SP-AQ的初始绿色荧光来自于AQ的原始荧光。在接受紫外光照射后,SP转变为开环MC形式,展现出红色荧光,由于MC的吸收光谱和AQ的荧光光谱产生大面积重叠,因此我们推测出现MC-AQ的红色荧光同时可能伴随着分子内能量转移。当对SP-AQ分子进行理论计算模拟时证明,SP-AQ的初始绿色荧光确实来自AQ部分,在被紫外光激发后发出的红色荧光是来自MC部分。这对螺吡喃的双色荧光切换机理的理解进行了补充,更拓宽了双色荧光光开关材料的发展体系。更多还原

【Abstract】 Photoswitches are capable of undergoing reversible changes of structure upon exposure to light irradiation.The two isomers exhibit long-term stability.Fluorescent phtoswitches not only possess the ability to change structures but also emit fluorescence.In both the "on" and "off" states,fluorescent photoswitches manifest distinct colors and spectral changes.Consequently,they are found extensive applications in areas including anti-counterfeiting dyes,biological imaging,and optoelectronic devices due to their remarkable utility.Spiropyan(SP)and its derivatives,as traditional organic fluorescent photoswitches,represent the earliest and most extensively investigated systems for photoswitching.Under normal conditions,SP undergoes color change from colorless to dark purple upon external stimulation,accompanied by red fluorescence and spectral changes.However,in the solution state,SP exhibits only red fluorescence due to the requirement of molecular structure flipping for its transformation merocyanine with fluorescence under UV irradiation.This flipping necessitates a larger isomerization space which can be satisfied by the free movement of molecules in solution.Conversely,in confined solid states,Tight packing restricts to freely flip of molecules,thus hinder the realization of fluorescent photoswitching property in solid state of SP.This poses a major obstacle to studying materials of light stimulus response in solid state.To address the challenge and expand the repertoire of spiropyran-based photoswitching materials systems,our studies focuses on:1.Investigation of solid-state photoisomerization of spiropyran based on a flexible chain regulation strategyWe designed a spiropyran derivative with flexible group,SP1,to achieve the SP’s limited photochromism in the solid state.Detailed spectroscopic studies suggest that SP1 in aggregate state exhibits red fluorescence in the solid state and retains the typical photochromic and fluorescence switching functionalities.In order to elucidate SP1 achieves crystalline photochromism effectively,crystalline structure studies on both SP-COOH and SP1 crystals are conducted.The presence of carboxyl group in SPCOOH molecules leads to stronger intramolecular interactions that restrict molecular photoisomerization.In contrast,ester group increase intermolecular distances while weakening intermolecular interactions in SP1,resulting in looser molecular packing arrangements that provide additional free space for achieving solid-state photoisomerization.2.Design and studies of solid-state reversible dual-color fluorescent photoswitch based on spiropyranBased on the studies of SP1,SP-AQ is designed.The connection between the SP and AQ molecules is achieved through an ester group.Under alternating irradiation of UV light and visible light,the SP-AQ exhibits reversible switching between green fluorescence and red fluorescence.Detailed spectroscopic and theoretical studies reveal that the initial green fluorescence of SP-AQ originates from AQ’s inherent fluorescence.Upon exposure to UV light,SP undergoes transformation into MC form,resulting in red fluorescence from MC.It confirmed that our understanding of dual-color fluorescent photoswitching mechanism in SP-AQ provides insights for developing multi-color fluorescent photoswitching materials.更多还原