Inclusion of methylviologen dication in a cadmium tetracyanoplatinate host clathrate showing photochromism and photoluminescence modulation

Abstract

A cadmium tetracyanoplatinate host clathrate, (MV)[Cd2{Pt(CN)4}3]⋅2(H2O) (1), including a methylviologen dication (MV2+) was synthesized, and the crystal structures, photochromic and photoluminescence properties were investigated. In 1, the alternatively parallel stacking between the MV2+ dications as electron acceptors in the channels and the electron donors [Pt1(CN)4]2– units in the host frameworks give a unique donor-acceptor (DA) system. Under UV irradiation, the electron transfer between MV2+ and [Pt(CN)4]2– ions generates MV·+ radicals with a photochromic behavior from pale-yellow to blue. This process occurs through single-crystal-to-single-crystal (SCSC) transformation and obvious structure variation of viologen cations is successfully observed. Moreover, the spectral overlap between the emission bands of 1 and the absorption around 623 nm for the MV·+ radicals leads to a modulation of the photoluminescence.