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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ground- and Excited-State Proton Transfer in Anthocyanins: From Weak Acids to Superphotoacids
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Ground- and Excited-State Proton Transfer in Anthocyanins: From Weak Acids to Superphotoacids

机译：花青素中的基态和激发态质子转移：从弱酸到超光酸

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摘要

Malvidin-3, 5-diglucoside (malvin), cyanidin-3, 5-diglucoside (cyanin), and pelargonidin-3, 5-diglucoside (pelargonin) are among the most representative anthocyanins because of their abundance in the most common red flowers and fruits. Anthocyanin color is directly affected by the pH-dependent chemistry of the red (acid) form of these compounds, while anthocyanin photostability is a function of the photophysics of the first excited singlet state. In the present work, we employ laser flash photolysis and picosecond time-correlated single-photon counting to determine the dynamics of the proton-transfer reactions of these three anthocyanins in the ground [deprotonation rate constants, k_d = 1.3 * 10~6s~(-1) (pelargonin), 1.8 * 10~6s~(-1) (cyanin), and 3.8 * 10~6s~(-1) (malvin)] and first excited singlet state [deprotonation rate constants, k_d = 4.3 * 10~(10)s~(-1) (pelargonin), 4.0 * 10~(10)s~(-1) (cyanin), and 1.6 * 10~(11)s~(-1) (malvin)], respectively. The ground- and excited-state proton-transfer rate constants for anthocyanins and for photoacids of the naphthol type are found to correlate with an empirical parameter related to the ionic character of the dissociable OH bond. The present results show that the typically weak fluorescence of the flavylium cation form of anthocyanins is due primarily to competitive ultrafast, adiabatic proton transfer to water. This process is highly efficient as an energy-wasting mechanism, as would be required by an in vivo role such as protection of plant tissues from potentially deleterious excess radiant energy.
机译：Malvidin-3、5-diglucoside（malvin），cyanidin-3、5-diglucoside（cyanin）和pelargonidin-3、5-diglucoside（pelargonin）是最具代表性的花色苷，因为它们在最常见的红色花朵和花蕾中含量丰富。水果。花青素的颜色直接受这些化合物的红色（酸）形式的pH依赖化学的影响，而花青素的光稳定性是第一个激发单重态的光物理性质的函数。在目前的工作中，我们采用激光闪光光解法和皮秒时间相关的单光子计数来确定这三种花色苷在地面中的质子转移反应动力学[去质子化速率常数，k_d = 1.3 * 10〜6s〜（ -1）（pelargonin），1.8 * 10〜6s〜（-1）（花青素）和3.8 * 10〜6s〜（-1）（马尔文）]和第一激发单重态[去质子化速率常数，k_d = 4.3 * 10〜（10）s〜（-1）（pelargonin），4.0 * 10〜（10）s〜（-1）（花青素）和1.6 * 10〜（11）s〜（-1）（马尔文）] ， 分别。发现花色素苷和萘酚型光酸的基态和激发态质子转移速率常数与与可离解OH键的离子特性有关的经验参数相关。目前的结果表明，花青素的黄酮阳离子形式的荧光通常较弱，这主要是由于竞争性的超快绝热质子转移到水中。如体内作用所要求的，例如保护植物组织免于潜在有害的过量辐射能，该过程作为能量浪费机制是高效的。

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