Photoinduced magnetic hysteresis in a cyanide-bridged two-dimensional [Mn2W] coordination polymer

Abstract

2D magnetic materials have been opening a new horizon in materials science. It is challenging to switch the magnetic hysteresis of 2D magnetic materials via light irradiation, which is applicable for future molecular devices. In this work, the reaction of (Bu₄N)₃[W^V(CN)₈], MnCl₂·4H₂O, and bis(4-pyridyl) disulfide (dpd) provides a new cyanide-bridged 2D compound, {[W^IV(CN)₈][Mn^II(dpd)₂][Mn^II(CH₃OH)₂]·2CH₃OH·2H₂O}_n ([Mn₂W_LS] and LS: low spin). The magnetic susceptibility measurements of [Mn₂W_LS] suggest that paramagnetic Mn^II (S = 5/2) ions are magnetically separated by diamagnetic W^IV ions. Photomagnetic experiments using a 405 nm laser confirm the presence of the light-induced excited spin state trapping (LIESST) effect on the W^IV ions from the singlet (S = 0) to the triplet (S = 1) states, and the formation of a metastable high spin species, [Mn₂W_HS]. In this photogenerated metastable phase, the W^IV (S = 1) and Mn^II (S = 5/2) ions are antiferromagnetically coupled. Field-cooled magnetization experiments suggest that the photoinduced [Mn₂W_HS] layer compound is a ferrimagnet with a transition temperature of 24 K. The current work provides a strategy to build photoswitchable 2D magnetic materials.