Platinum(ii)-CN/SCN-rhenium(i) luminophores adopting multiple aggregation states

Abstract

Cycloplatinated complexes constitute an important class of luminescent compounds for sensing, bioimaging and optoelectronics. Their properties often depend on intermolecular non-covalent interactions between sterically unhindered square planar motifs. Here we investigated the photophysical behavior of novel platinum(II)–rhenium(I) cyanido-/thiocyanato-bridged complexes [{Pt(C^N^N)}(µ-CN/SCN){Re(phen)(CO)₃}]⁺ (^–C^N^N = cyclometalated pincer ligand, phen = 1,10-phenanthroline) containing two chromophoric units. Their phosphorescence is dominated in solution by the platinum(II) fragment derived from HC^N^N = phenylbipyridine, while major contribution of the rhenium(I) motif and dual emission are observed when HC^N^N = phenyl-pyrazolylpyridine and triazolyl-phenylpyridine ligand precursors are used. The solid-state behavior depends on intermolecular interactions between platinum components, the preferential mode of which is defined by the counterions. The complexes showcase a rare example of platinum(II)-based bichromophoric compounds demonstrating vapo-/mechano-/thermo-induced reversible changes of optical properties and phase transformations, which could be interpreted as a result of switching between several conformations of noncovalently bound dimers.