Fast and stable vapochromic response induced through nanocrystal formation of a luminescent platinum(II) complex on periodic mesoporous organosilica

Hiroki Matsukawa,Ayana Sato-Tomita,Atsushi Kobayashi,Takahiro Tsunenari,Yoshifumi Maegawa,Shinji Inagaki,Masaki Yoshida,Masako Kato,Shunsuke Nozawa

doi:10.1038/s41598-019-51615-w

Abstract

A hybrid vapoluminescent system exhibiting fast and repeatable response was constructed using periodic mesoporous organosilica with bipyridine moieties (BPy-PMO) and a Pt(II) complex bearing a potentially luminescent 2-phenylpyridinato (ppy) ligand. An intense red luminescence appeared when the Pt(II)-complex immobilised BPy-PMO was exposed to methanol vapour and disappeared on exposure to pyridine vapour. The ON-OFF vapochromic behaviour occurred repeatedly in a methanol/pyridine/heating cycle. Interestingly, a rapid response was achieved in the second cycle and cycles thereafter. Scanning and transmission electron microscopies (SEM/TEM), absorption and emission, and nuclear magnetic resonance spectroscopies, mass spectrometry, and powder X-ray diffraction indicated that methanol vapour induced Si-C cleavage and thus liberated [Pt(ppy)(bpy)]Cl (bpy = 2,2′-bipyridine) from the BPy-PMO framework. Furthermore, the self-assembling properties of the Pt(II) complex resulted in the formation of highly luminescent micro/nanocrystals that were homogeneously dispersed on the porous support. The unique vapoluminescence triggered by the unprecedented protodesilylation on exposure to protic solvent vapour at room temperature is attributable to BPy-PMO being a giant ligand and an effective vapour condenser. Consequently, this hybrid system presents a new strategy for developing sensors using bulk powdery materials.

Highlights

Porous materials are extremely attractive for the creation and control of nano- and meso-spaces where specific effects and novel phenomena are expected
Pt(II)-immobilised BPy-periodic mesoporous organosilicas (PMOs) (Pt-PMO) with a favourable immobilisation amount was successfully obtained by reacting BPy-PMO with [Pt(ppy)Cl(DMSO)] (DMSO = dimethyl sulfoxide) in CH2Cl2 instead of DMSO, which was used in our previous report (Fig. 2a)[16]
The two broad peaks at ~1.4–1.9 Å and 2.2–2.7 Å were well-explained by the local structure of the first and second shells around the Pt site in the model complex [Pt(ppy)(bpy)](PF6), whose crystal structure was elucidated by single crystal X-ray analysis of a linear chain structure of the Pt(II) complex units with a moderate Pt···Pt distance www.nature.com/scientificreports

Summary

Introduction

Porous materials are extremely attractive for the creation and control of nano- and meso-spaces where specific effects and novel phenomena are expected. BPy-PMO, composed of silicate and 2,2′-bipyridine (bpy) connected by covalent bonds, allowed the metal ions to be captured through direct coordination to the periodic mesoporous framework (Fig. 1a)[13]. This PMO was utilised as a photocatalytic system with polypyridine-Ru(II) and Ir(III), Re(I), Cu(II), and Pt(II) complexes as well as other selective catalytic systems[10,14,15,16,17,18]. We developed a unique vapochromic luminescent system that exhibited a rapid and stable vapour response with clear colour changes using integrated coordination sites and the vapour absorptivity of BPy-PMO.

Methods

Results

Conclusion