Iodine(iii)-promoted regioselective and efficient synthesis of β-triazolyl BODIPYs for the selective recognition of nickel ions and bovine serum albumin

Abstract

Various β-triazolyl tethered BODIPYs were efficiently prepared in a sequential one-pot protocol involving the initial reaction of BODIPY with iodobenzene diacetate (IBD) and sodium azide to in situ generate BODIPY azides followed by a copper-catalyzed azide–alkyne cycloaddition reaction. Under the optimized reaction conditions, various β-triazolyl BODIPYs 5a–i were successfully prepared in good yields and adequately characterized by using UV, NMR, mass spectral data and XRD analyses. The UV-Visible spectra of the prepared β-triazolyl BODIPYs 5a–i showed intense absorption bands (514–545 nm) with a 13–44 nm red shift when compared with those of the parent BODIPY. The selective recognition of compound 5d towards Ni²⁺ ions (detection limit 0.26 nM) led to significant quenching in the fluorescence intensity over other selected bivalent metal ions. The complex formed between 5d and Ni²⁺ in a stoichiometry of 2 : 1 was found to have a binding constant of 7.5 × 10⁵ M⁻¹. The fluorescence of compound 5i gets enhanced gradually upon interaction with bovine serum albumin due to its selective and high binding affinity (1.25 × 10⁵ M⁻¹) with protein and a concomitant decrease in the total non-radiative decay rate.