Visualization of Ion Conductivity: Vapochromic Luminescence of an Ion-Conductive Ruthenium(II) Metalloligand-Based Porous Coordination Polymer

We
synthesized a new porous coordination polymer {La1.75(OH)1.25[Ru­(dcbpy)3]·16H2O} (La7-[4Ru]4; H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine)
composed of a luminescent ruthenium­(II) metalloligand [Ru­(4,4′-dcbpy)3]4– and La3+ cations. X-ray analysis
for La7-[4Ru]4 revealed that the La3+ cations and
[4Ru] metalloligands are crystallized in a molar ratio of 7:4 with
OH– counteranions and a void fraction of ∼25.5%.
Interestingly, La7-[4Ru]4 shows a reversible structural transition
triggered by water ad/desorption, which affects not only the triplet
metal-to-ligand charge-transfer (3MLCT) emission energy
but also the ion conductivity in the solid state. This correlation
suggests that La7-[4Ru]4 is an interesting material that enables
visualization of the ion conductivity via the 3MLCT emission
energy.