Photophysical characterization of methyl viologen ion-exchanged within a zirconium phosphate framework

Abstract

The photophysical properties of 1,1′-dimethyl-4,4′dipyridinium (methyl viologen, MV 2+) intercalated within zirconium phosphate (ZrP) were investigated. The intercalation of MV 2+ within ZrP was achieved by ion-exchange using a hydrated form of ZrP with six water molecules per formula unit and an interlayer distance of 10.3 Å. The intercalation yields a new phase with an interlayer distance up to 10.6 Å. The MV 2+-exchanged ZrP material was characterized using elemental analysis, XRPD and IR data. The MV 2+-exchanged ZrP materials show a red shift in the UV–Vis spectra in contrast with solution. The photoexcitation of nitrogen purged, MV 2+-exchanged ZrP water suspensions with UV light leads to fluorescence emission with a maximum at 337 nm. The photoexcitation of MV 2+-exchanged ZrP suspensions without nitrogen purging yields two fluorescence emissions with maxima at 337 and 450 nm. The emission in the visible region can be attributed to a photodecomposition product. The fluorescence quantum yields indicate that the emission of MV 2+-exchanged ZrP is of the same order of magnitude as that of MV 2+ in water indicating a strong deactivation of the excited state by non-radiative pathways.