New spin crossover polymeric composite and another way to describe the result

Firstly, we synthesized a novel spin crossover coordination compound 1 {[Fe(MPEG-trz) 3 ](BF 4 ) 2 }(MPEG-trz: polymeric ligand obtained by amidation reaction between methoxy polyethylene glycol (MPEG) and 4-amino-1,2,4-triazole (NH 2 -trz)). And then a suite of coordination compounds {[Fe(MPEG-trz) m (NH2-trz) n ](BF 4 ) 2 }(m   =   2, n   =   1, 2 ; m   =   1.5, n   =   1.5, 3 ; m   =   1, n   =   2, 4 ;) have been successively synthesized by self-assembly reaction between Fe(BF 4 ) 2 ·6H 2 O and MPEG-trz/NH 2 -trz in different proportion respectively. The structure detail is obtained through FT-IR, XRD and 1 H NMR measurements, while spin crossover behavior of these coordination compounds are inspected by superconducting quantum interference device (SQUID) and DSC . The new polymeric composites not only show mechanical behavior particular the malleability but also exhibit an abrupt spin crossover behavior with a slender hysteresis loop. Simultaneously we speculated the probably cooperative formation mechanism of spin crossover system on the based of analysis upon the magnetic performance among these coordination compounds with different proportions in MPEG-trz and NH 2 -trz.