Dodecaborate-Functionalized Anchor Dyes for Cyclodextrin-Based Indicator Displacement Applications

A new type of water-soluble anchor dyes, that is, dyes which carry an auxiliary unit for strong binding to macrocyclic host molecules, has been synthesized. It consists of 7-nitrobenzofurazan (NBD) as a dye and the dodecaborate cluster (B₁₂H₁₁R) as a dianionic, globular, and purely inorganic anchoring group for cyclodextrins (<i>K</i>_a > 10⁵ M^–1). The synthesized dodecaborate-substituted dyes show marked changes in their photophysical properties (UV–vis and fluorescence) upon complexation with cyclodextrins (β-CD and γ-CD), such that the resulting host·dye complexes (1:1 stoichiometry) present sensitive reporter pairs for indicator displacement applications