Advances in spin crossover metal complexes: a comprehensive review on its gas sensing applications

Spin crossover metal complexes (SCO) are unique class of coordination compounds that can switch between LS and HS (low and high spin) states in response to external stimuli like pressure, temperature, gas molecules and light irradiation. This bistable behaviour makes them excellent candidate for many technological applications like data storage, molecular switches, actuators and sensing applications. The sensing mechanism of these complexes is based on the reversible change in their spin state which results in difference in magnetic, electrical and optical responses which can be evaluated with high sensitivity. This review provides a comprehensive analysis of the synthesis methods and characterization techniques of SCO metal complexes with a special focus on their gas sensing applications that remains unexplored in the literature. To address this gap this, review comprehensively examines approximately eight published researches in this field, with a particular focus on gases such as ammonia (NH₃), carbon dioxide (CO₂) and volatile organic compounds (VOCs) like ethanol, methanol and alcohol we highlight the sensitivity and selectivity of SCO based metal complexes with their future prospects to enhance their performances for the future gas detection technologies. The review aims to explore the potential of SCO complexes in gas sensing technology and highlight the ongoing progress in this field. To the best of our knowledge this is the first ever review article which is dedicated exclusively to the gas sensing application of SCO based metal complexes to provide a new way for the advancement in this emerging field.