UV-Vis-NIR response in a photochromic diarylethene-based spin crossover framework with heterogeneous FeII–AgI nodes

Abstract

Spin crossover (SCO) compounds are versatile platforms for incorporating functional ligands, enabling profuse magnetic regulating strategies and providing new likelihood for diversified practical applications of magneto-switches and information storage devices. Among the copious choices for stimuli-responsive ligands, diarylethene stands out as a photochromic unit that can be integrated into magnetic materials. Here, we report a triple interpenetrating SCO framework [Fe^II(L_o)₂{Ag(CN)₂}₂{Ag(CN)}₂] (1, L_o = 1,2-bis(2-methyl-5-(pyridin-4-yl)thiophen-3-yl)cyclopent-1-ene) with heterometallic nodes. Distinct from the conventional SCO frameworks in which Fe^II centers are directly bridged by organic ligands, the coordination fashion in 1 is manifested as Fe^II–L_o–Ag^I–L_o–Fe^II. Photochromism is partially realized by the alternation of 365 nm and 520 nm light irradiation due to the tightly packed lattice. Subtle magnetic switching is observed from 1 to 1^UV. Moreover, 1^UV displays a photothermal response up to 162 °C under 808 nm light irradiation, with an enhancement in the photothermal conversion efficiency compared with that of 1. This thermally stable three-dimensional framework provides new structural possibilities for SCO polymers and takes a step forward in the assembly of UV-Vis-NIR responsive magnetic materials.