An AIE-Active Fe(II) Complex Exhibiting Synergistic Spin-Crossover and Luminescent Properties

The investigation of the synergistic relationship between spin-crossover (SCO) and luminescence has recently become a field of intensive research. However, the weak emission intensity of these complexes presents a challenge for the study of luminescence properties in the aggregated state. In general, an aggregation-induced emission (AIE)-active ligand can be introduced to enhance luminescent intensities and fabricate SCO-fluorescent materials. Herein, a mononuclear complex [Fe(bpp-TPE)2]·(ClO4)2·H2O·0.5CH2Cl2 (bpp-TPE-Fe), where bpp-TPE = (E)-1-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)-N-(4-(1,2,2-triphenylvinyl)phenyl)methanimine, bearing an AIE-active fluorophore, was synthesized. This complex exhibits a gradual SCO behavior and strong luminescence in the aggregated state. Moreover, the SCO process covers the temperature range where a substantial increase in luminescence intensity occurs, implying a coupling between SCO and fluorescence. At the same time, the AIE behavior of bpp-TPE-Fe was investigated in a DCM/n-hexane mixture. This work provides a promising strategy for the development of multifunctional switchable materials.