Field Effects Induce Bathochromic Shifts in Xanthene Dyes

There is ongoing interest in near-infrared (NIR) absorbing and emitting dyes for a variety of biomedical and materials applications. Simple and efficient synthetic procedures enable the judicious tuning of through-space polar (field) effects as well as low barrier hydrogen bonding to modulate the HOMO–LUMO gap in xanthene dyes. This affords unique NIR-absorbing xanthene chromophores.