Precise Molecular Design and Construction of Organic Ferromagnets

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1) Synthesis of Super-high-spin Polycarbenes with Starburst Structures : A series of polycarbenes 1,3,5- [H (C_6H_4C : ) n/3] 3C_6H_3 have been synthesized and found from their magnetization data to have unprecedentedly high-spin S=6 and 9 ground states for n=6 and 9, respectively. Having optimized the reaction conditions for the construction of the 1,3,5-trisubstituted central benzene rings, we have made logical extension to more highly branched polycarbenes with higher spin concentration. While some of the polycarbenes showed a superparamagnetic properties due to blocking of the rotation of the principal axis of magnetization, the intermolecular and interbranch interactions were found to be antiferromagnetic.2) Synthesis of Persistent High-spin Polynitroxide Radicals : Two or three nitroxide radical centers were assembled into one molecules by means of ferromagnetic couplers m-C_6H_4 or 1,3,5-C_6H_3. The di-and trinitroxide radicals were found by the analysis of their EPR fine structures and SQUID susceptibility to have triplet and quartet ground states, respectively.3) Construction of Molecular Magnets by Assembling High-spin Molecules : The persistent di-and trinitroxide radicals were used as di-and trivalent ligands for transition metal complexes. In the case of a combination of Mn (hfac) _2 and trinitroxide radicals (TN), molecular magnets with Curie temperatures of 3.4 and 46 K have been obtained. X-ray crystallographic analyzes revealed the layred honey-combed network and three dimensional crossed-parallels structures, respectively, both consisting of units (TN) _2 {Mn (hfac) _2} _3.4) Design and Survey of Intemolecular Interaction Assisting Spin Alignment in Organic Free Radicals in Solid State : Prototypes for the hydrogen bonding interaction in aromatic polyamides and the S...S interaction in polythiophenes have been studied to find the potentiality of these interaction in helping intermolecular spin alignment.