Observation of <i>T</i><sub>LIESST</sub> above Liquid Nitrogen Temperature and Disclosure of Hidden Hysteresis\nin Multiresponsive Hofmann-type Coordination Polymers

Photoresponsive spin-crossover (SCO)\nmolecules are an important\nclass of bistable magnetic molecules with intriguing potential in\ndevice applications. The light-induced excited spin state trapping\n(LIESST) and the combined application of light and temperature can\nprovide access to the metastable region of the SCO profile. The primary\nobstacle in utilizing light stimuli is the manifestation of light-induced\ntrappings at extremely low temperatures. Herein, we report two novel\nmultiresponsive 2D Hofmann-type coordination polymers exhibiting light-induced\nexcited spin state trapping above liquid nitrogen temperature (<i>T</i><sub>LIESST</sub> = 82 and 81 K). Stimulating the samples\nin conjugation with light and temperature successfully unveils hysteresis,\nwhich is otherwise concealed. Apart from light and temperature, we\nfound that the SCO phenomenon is also responsive to external hydrostatic\npressure and exhibits modulation of the hysteresis width and transition\ntemperature shifts with changes in pressure.