Porosity induced rigidochromism in platinum(II) terpyridyl luminophores immobilized at silica composites

Stimuli responsive composites consisting of inorganic or organometallic coordination substrates supported on porous platforms that integrate and improve the key features of both the substrate and platform, open the doorway to advanced multifunctional materials. This work presents a new class of stimuli responsive multifunctional materials based on platinum(II) terpyridyl luminophores@silica composites. Presented here is how the intercalation of Pt(II) salts with a planar architecture and sterically permitting terpyridyl ligands within meso or microporous silica support impacts Pt(II) spectroscopies. The photophysics and luminescence properties of square-planar Pt(II) salts are dictated by their intermolecular, non-covalent Pt⋯Pt interactions between the individual Pt(II) units; a feature that has been explored in designing stimuli responsive materials. This work explores a novel methodology where the electronic structure and luminescence behavior of such salts are systematically varied through their intercalation within rigid silica frameworks. The intercalation of Pt(II) complexes with varied degrees of non-covalent Pt⋯Pt interactions in the virgin form within meso-macroporous silica supports generates materials that show marked variation in their electronic structure and luminescence behavior compared to their virgin salts. Further, the spectroscopies show a systematic dependance on the mean pore size of the silica support. The X-ray powder diffraction and microscopy studies reveal these behaviors to be related to the perturbations in their long-range structural order, that gets reflected in their microcrystalline dimensions and particle morphologies.