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Gas-Phase Ion Spectroscopy of Congo Red Dianions and Their Complexes with Betaine
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-03-12 00:00:00 , DOI: 10.1021/acs.jpca.8b00904 Christina Kjær 1 , James M. Lisy 2 , Steen Brøndsted Nielsen 1
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-03-12 00:00:00 , DOI: 10.1021/acs.jpca.8b00904 Christina Kjær 1 , James M. Lisy 2 , Steen Brøndsted Nielsen 1
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Congo Red (CR) is an azo dye that is negatively charged in aqueous solutions. Here we report on the intrinsic electronic properties of CR dianions from mass spectroscopy experiments on bare dianions and their complexes with betaine (B). As betaine is a zwitterion, it possesses a large dipole moment and is a good reporter on the sensitivity of CR to microenvironmental changes. Photoexcitation of CR2– in the visible region resulted in several fragment ions after absorption of at least three photons, with major fragmentation routes due to breakage of one or both C–NN bonds, one azo linkage, and/or the bonds to sulfite. Their yields as a function of excitation wavelength reveal a broad absorption in the visible region with the lowest-energy band located at ∼500 nm. Features are observed with a spacing of ∼1500 cm–1. One photon was sufficient to dissociate CR2–·B, and its action spectrum was almost identical to those of CR2– in accordance with previous findings that a symmetric ion is essentially unaffected by changes in its microenvironment. Electron detachment occurs in the UV with threshold energy of 3.6 ± 0.1 eV for CR2– and 3.81 ± 0.06 eV for CR2–·B. Attempts to measure fluorescence from photoexcited CR2– were unsuccessful.
中文翻译：
刚果红离子及其甜菜碱配合物的气相离子光谱
刚果红（CR）是一种偶氮染料，在水溶液中带负电荷。在这里，我们从裸二价阴离子及其与甜菜碱（B）的配合物的质谱实验中报告了CR二价阴离子的固有电子性能。由于甜菜碱是一种两性离子，因此它具有很大的偶极矩，并且是CR对微环境变化敏感性的很好的报道者。吸收至少三个光子后，CR 2–在可见光区的光激发导致几个碎片离子，主要断裂途径是由于一个或两个C–NN键，一个偶氮键和/或与亚硫酸盐的键断裂。它们的产率与激发波长的关系揭示了在可见光区域的宽吸收，最低能带位于〜500 nm。观察到的特征间距约为1500厘米–1。一个光子足以解离CR 2– ·B，并且其作用谱与CR 2–的作用谱几乎相同，根据先前的发现，对称离子基本上不受其微环境变化的影响。在UV中，电子发生脱离，对于CR 2–，阈值能量为3.6±0.1 eV，对于CR 2– ·B ，阈值能量为3.81±0.06 eV 。尝试测量光激发的CR 2–发出的荧光的尝试未成功。
更新日期：2018-03-12
中文翻译：
刚果红离子及其甜菜碱配合物的气相离子光谱
刚果红（CR）是一种偶氮染料，在水溶液中带负电荷。在这里，我们从裸二价阴离子及其与甜菜碱（B）的配合物的质谱实验中报告了CR二价阴离子的固有电子性能。由于甜菜碱是一种两性离子，因此它具有很大的偶极矩，并且是CR对微环境变化敏感性的很好的报道者。吸收至少三个光子后，CR 2–在可见光区的光激发导致几个碎片离子，主要断裂途径是由于一个或两个C–NN键，一个偶氮键和/或与亚硫酸盐的键断裂。它们的产率与激发波长的关系揭示了在可见光区域的宽吸收，最低能带位于〜500 nm。观察到的特征间距约为1500厘米–1。一个光子足以解离CR 2– ·B，并且其作用谱与CR 2–的作用谱几乎相同，根据先前的发现，对称离子基本上不受其微环境变化的影响。在UV中，电子发生脱离，对于CR 2–，阈值能量为3.6±0.1 eV，对于CR 2– ·B ，阈值能量为3.81±0.06 eV 。尝试测量光激发的CR 2–发出的荧光的尝试未成功。
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