Shape-persistent binuclear cyclometalated platinum(II) luminophores: Pushing π-mediated excimeric fluid emissions into the NIR region and ion-induced perturbations

The synthesis and spectroscopic properties of new binuclear cyclometalated 6-aryl-2, 2'-bipyridine (C,N,N) platinum(II) complexes tethered by a xanthene backbone has been reported. The rigid bridging unit is chosen to preclude intramolecular metal-metal interactions and hence MMLCT states, while allowing π-stacking interactions within the (Pt-C, N, N) moiety, which has pushed the associated excimeric-type emission into the near-infrared region. The emission features and particularly the relative intensities of the high- and low-energy emissions for desirable electronic and recognition/signaling, are independent of complex concentration. These emissions are susceptible to perturbations in different solvents and by selected metal ions. The NIR emissions are desirable reporting tools for biomolecular probes and chemosensing applications.