Ni Weijuan, Kaur Gurpreet, Springsteen Greg, Wang Binghe, Franzen Stefan
Department of Chemistry, North Carolina State University, Raleigh 27695, USA.
Bioorg Chem. 2004 Dec;32(6):571-81. doi: 10.1016/j.bioorg.2004.06.004.
An anthracene-based fluorescent boronic acid system developed by the Shinkai group has been widely used for the preparation of fluorescent sensors for carbohydrates. Such application is based on the significant fluorescence intensity increase of this system upon binding with a carbohydrate. The mechanism through which this fluorescence intensity change happens was originally proposed to go through a B-N bond formation mechanism, which masks the nitrogen lone pair electrons. However, our own fluorescence studies suggest a possible alternative mechanism for the fluorescence change upon the formation of a boronic acid (1a) complex with diols. In this new proposed mechanism, complex formation induces solvolysis, which results in the protonation of the amine nitrogen if the reactions are carried out in a protic solvent such as water. This protonation prevents the photoinduced electron transfer, resulting in reduced quenching of the anthracene fluorescence. Such a solvolysis mechanism is supported by evidence from various types of experiments and theoretical calculations.
新海小组开发的基于蒽的荧光硼酸体系已被广泛用于制备碳水化合物荧光传感器。这种应用基于该体系与碳水化合物结合后荧光强度显著增加。这种荧光强度变化发生的机制最初被认为是通过B-N键形成机制，该机制掩盖了氮孤对电子。然而，我们自己的荧光研究表明，在硼酸（1a）与二醇形成配合物时，荧光变化可能存在另一种机制。在这个新提出的机制中，配合物的形成诱导溶剂解，如果反应在质子溶剂（如水）中进行，这会导致胺氮质子化。这种质子化阻止了光诱导电子转移，从而减少了蒽荧光的猝灭。各种实验和理论计算的证据支持了这种溶剂解机制。
