Solid-State Phosphorescence-to-Fluorescence
Switching
in a Cyclometalated Ir(III) Complex Containing an Acid-Labile Chromophoric
Ancillary Ligand: Implication for Multimodal Security Printing
- Publication date
- Publisher
Abstract
In this study, we have demonstrated the reconstruction
of encrypted
information by employing photoluminescence spectra and lifetimes of
a phosphorescent Ir(III) complex (IrHBT). IrHBT was constructed on
the basis of a heteroleptic structure comprising a fluorescent N<sup>∧</sup>O ancillary ligand. From the viewpoint of information
security, the transformation of the Ir(III) complex between phosphorescent
and fluorescent states can be encoded with chemical/photoirradiation
methods. Thin polymer films (poly(methylmethacrylate), PMMA) doped
with IrHBT display long-lived emission typical of phosphorescence
(λ<sub>max</sub> = 586 nm, τ<sub>obs</sub> = 2.90 μs).
Meanwhile, exposure to HCl vapor switches the emission to fluorescence
(λ<sub>max</sub> = 514 nm, τ<sub>obs</sub> = 1.53 ns)
with drastic changes in both the photoluminescence color and lifetime.
Security printing on paper impregnated with IrHBT or on a PMMA film
containing IrHBT and photoacid generator (triphenylsulfonium triflate)
enables the bimodal readout of photoluminescence color and lifetime
