One-step condensation synthesis and characterizations of indocyanine green
Xiangning Fang, Wenjuan Liu, Xia Wu, Wei Zhou, Jie Chen, Xiaogang Liu, Zhaochao Xu
Abstract
Indocyanine green (ICG) was the first fluorescent dye approved by the United States Food and Drug Administration (FDA) for clinical use in humans and had been widely used in biological imaging for decades. However, there were few public reports on the synthesis method of ICG, and there were few studies on its fluorescence emission mechanism, which limited its chemical derivation and function expansion. In this paper, we provided a one-step condensation method for the synthesis of ICG with 92% yield. We also employed quantum chemical calculations of the frontier molecular orbitals to show that the luminescence of ICG was mainly derived from the polymethine conjugation system, and the naphthalenyl rings at both ends had little effect on the UV–vis absorption and fluorescence wavelengths.