Construction of Spin Crossover‐Fluorescent Bifunctional Cyclic Chain‐Like Fe(II) Compounds from Carbazole Ligands

The incorporation of fluorescent properties into spin‐crossover (SCO) materials, aiming at controlling fluorescence via spin‐state transitions for applications in magneto‐optical switching and information processing, represents an appealing research direction. In this study, we prepared two examples of one‐dimensional cyclic chain‐like Fe(II) coordination polymers, denoted as [Fe(DPPC)2(NCS)2]⋅CH3OH⋅o‐C6H4Cl2 (1, DPPC=3,6‐di‐4‐pyridinyl‐9‐[4‐(4‐pyridinyl)phenyl]‐9H‐carbazole) and [Fe(PDPC)2(NCS)2] (2, PDPC=3,6‐di(pyridin‐4‐yl)‐9‐phenyl‐9H‐carbazole). Analyses through single‐crystal X‐ray studies and magnetic measurements validate the two‐step SCO behavior of 1 within the temperature range of 50~200 K. Additionally, when combined with temperature‐dependent fluorescence emission spectroscopy, the results demonstrate the coexistence of SCO and fluorescence in 1. Two instances of one‐dimensional cyclic chain‐like iron(II) compounds incorporating carbazole moiety ligands were synthesized, one of them exhibited fluorescence and two‐step spin‐crossover behaviour.