Synthesis of amino-functionalized cyanine dyes

Abstract

Cyanine dyes are characterized by two terminal nitrogen atoms connected by the chain of methine groups. By manipulating the structural features, such as methine chain length, heterocycles, and their substituents, they exhibit a wide range of absorption and emission in the electromagnetic spectrum. In the current study, we present the synthesis of five indocarbocyanine dyes with amino functionalization. Trimethine and two derivatives of pentamethine cyanines show absorption in the visible region whereas, two heptamethine derivatives emit in the near-infrared region, which is useful for biological research due to increased sensitivity and negligible autofluorescence in cell tissues. The objective of amine functionalization of these commercial dyes is to design dye substituted polymer (for example: PFPA) for enhanced fluorescence. However, all synthesized dyes exhibit small Stokes shifts that could result in self-quenching. Therefore, we also propose a new approach as a continuation of the current work.