LAUSR

Abstract The structural modification of plant pigments allows the development of new functional dyes with tailored photophysical properties. Two-photon excitation fluorescence microscopy has emerged as an important technique, but requires the use of fluorophores having large two-photon absorption cross-sections in water. This feature is rarely found in natural or artificial dyes, but betalains, the main pigments of beetroots and some species of fluorescent flowers, can be modified to produce water-soluble two-photon fluorophores. Herein we describe the semisynthesis and photophysical characterization of two water-soluble artificial coumarinic betalains. The excitation of these compounds in the near-infrared results in yellow fluorescence with two-photon cross-sections in water of 323 GM and 179 GM.