Analytical Sciences

Abstract − Analytical Sciences, 32(2), 251 (2016).

Photophysical Properties of the 2-Hydroxytryptanthrin and Its Sodium Salt as Near-infrared Dyes for Fluorescent Imaging
Jun KAWAKAMI,* Masahiro TAKAHASHI,* Shunji ITO,* and Haruo KITAHARA**
*Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
**Kitahara Laboratory Co. Ltd, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
2-Hydroxytryptanthrin (T2OH) and its sodium salt (sodium tryptanthrin-2-olate, T2ONa) were synthesized as near-infrared (NIR) dyes for fluorescent imaging. The absorption maxima (λa,max) of T2OH under a pH range from 1.3 to 7.2 and from 8.5 to 10.6 were ca. 410 nm and ca. 495 nm, respectively. Moreover, the fluorescence maxima (λf,max) were ca. 660 nm regardless of the pH range. T2ONa was water soluble and the λf,max were ca. 660 nm in both aprotic and protic solvents.