Biphenyl-hinged bisnitroxide biradicals toward intramolecular para- and diamagnetic switching

摘要: We designed and attempted to synthesize bisnitroxides involving a suitable spacer, which are supposed display switching behavior based on intramolecular covalent-bond formation cleavage. In this work biphenyl hinge was applied bring conformational freedom in spacer. Nitroxide radical groups generally introduced by way of organometallic reagents from halogen-metal exchange organic halides. For the reaction 2,2’-dibromo-4,4’-di-tert-butylbiphenyl, only one bromine atom substituted with tert-butyl nitroxide group. 2,2’,5,5’-tetrabromo-4,4’-di-tert-butylbiphenyl, unexpectedly, two N-tert-butylhydroxylamino were at 5,5’-positions place desired 2,2’-positions. The molecular structure 2,2’-dibromo-4,4’-di-tert-butyl-5,5’-bis(tert-butylamino)biphenyl-N,N’-dioxyl characterized means X-ray crystallography, magnetic study SQUID magnetometer revealed that spins present magnetically isolated solid.