Exploring the two step spin transition of Fe(NCBH3)(4phpy)2(m-bpypz)2 with ab initio calculations

Abstract

Spin crossover complexes represent a fascinating class of molecular materials with potential applications in diverse fields ranging from information storage to molecular electronics. Here using density functional theory, we investigate the properties of the binuclear spin crossover complex Fe(${\text{NCBH}}_3$)(4phpy)${}_2$(m-bpypz)${}_2$, which presents the intriguing property that the two step magnetic transition occurs through an intermediate state made of low spin or high spin chains, as seen experimentally. We observe that the different magnetic configurations can be reproduced by our calculations, and that irons ions are coupled antiferromagnetically. This complex transition is further elucidated through nudged elastic band calculations and observation of the magnetization density, and opens the path towards more studies of polynuclear spin crossover complexes.