Proton-switchable vapochromic behaviour of a platinum(ii)-carboxy-terpyridine complex

Area of Science:

• Coordination Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Platinum(II)-terpyridine complexes are explored for their unique photophysical properties.
• Vapochromism, the change in optical properties upon vapor adsorption, is a key phenomenon in materials science.
• Carboxy-functionalization offers a route to tune the properties of metal complexes.

Purpose of the Study:

• To synthesize and characterize a carboxy-substituted Pt(II)-terpyridine complex.
• To investigate the switchable vapochromic behavior of the complex in its protonated and deprotonated forms.
• To elucidate the structural basis for the observed vapochromism.

Main Methods:

• Synthesis of a carboxy-substituted Pt(II)-terpyridine complex, [PtCl(Hctpy)]Cl.
• Exposure of the complex to various organic solvent vapors and water vapor.
• X-ray structural analysis of different crystalline forms.
• Spectroscopic analysis (UV-Vis absorption and luminescence).

Main Results:

• The protonated complex, [PtCl(Hctpy)]Cl·3H2O, transforms from dark blue to yellow upon exposure to organic solvent vapors.
• The deprotonated complex, [PtCl(ctpy)]·H2O, exhibits red luminescence and shows vapochromic luminescence shifts upon water vapor exposure.
• X-ray analysis reveals distinct dimeric and columnar structures in the protonated and deprotonated forms, respectively, correlating with Pt-Pt distances and MMLCT transitions.
• Quasi-reversible switching between protonated and deprotonated forms was achieved using specific vapor exposures.

Conclusions:

• The carboxy group plays a crucial role in modulating the hydrophilicity and vapochromic properties of the Pt(II)-terpyridine complex.
• Structural rearrangements, particularly changes in intermolecular Pt-Pt distances, are responsible for the observed vapochromic effects.
• The complex demonstrates potential for applications in chemical sensing and responsive materials.