Bright NIR-Emitting Styryl Pyridinium Dyes with Large Stokes' Shift for Sensing Applications.

Two NIR-emitting donor-π-acceptor (D-π-A) type regioisomeric styryl pyridinium dyes (-) were synthesized and studied for their photophysical performance and environment sensitivity. The two regioisomers, and , exhibited interesting photophysical properties including, longer wavelength excitation (λ ≈ 530-560 nm), bright near-infrared emission (λ ≈ 690-720 nm), high-fluorescence quantum yields (ϕ ≈ 0.24-0.