Synthesis and Properties of Novel Photomodulation Magnetic Molecular-Based Magnet Based on Photochromic Biindenylidenedione Derivative

Abstract

Molecular-based magnetic material can be used for information storage, magnetic imaging, photo-magnetic switching and so on. So the design and synthesis of the molecular-based magnet is a focus of contemporary science research. Sparked by the strategy of molecular magnets, the novel photomodulation magnetic molecular-based magnet photochromic biindenylidenedione derivative with 2-nitropropane radical and 2,2,6,6-tetramethyl-piperidinyloxy (TEMPO) radical (4) was synthesized. The synthetic method of compound 4 is' that starting from photochromic biindenylidenedione derivative 7,7'-dimethyl-[2,2'-bi-1H-indene]-3,3'-diethyl-3,3'-di-hydroxy-1,1'-dione (1), via bromination reaction, 7,7'-bis(bromomethyl)-[2,2'-bi-1H-indene]-3,3'-diethyl-3,3'-dihydroxy-1,1'-dione (2) was obtained. Sodium ethoxide, 2-nitropropane and compound 2 were dissolved in absolute ethanol reaction to obtain biindenylidenedione derivative with 2-nitropropane radical and formyl 3. The structure of compound 3 was confirmed by H-1 NMR, MS and element analysis. The results indicated that 2-nitropropane group bonds with one methylene on the benzene ring of the compound 3. In further analysis to H-1 NMR and electron spin-resonace (ESR) spectra of compound 3 demonstrated that single electron spin exists in 2-nitropropane group. On the basis compound 3, stable nitroxide radical TEMPO was successfully introduced into the benzene rings of photochromic biindenylidenedione derivative to obtain compound 4. The properties of compounds 2, 3 and 4 were investigated. The testing results display that the solid compounds 2 similar to 4 possess photochromic property. ESR spectrum was found when irradiated solid compound 2. ESR spectrum was found and changed before and after photoirradiation in solid state of compound 3 and 4. The magnetic susceptibility measurement shows that the antiferromagnetic interaction for before and after photoirradiation in solid state of compound 4, and the antiferromagnetic interaction becomes stronger after photoirradiation. These testing results demonstrated that after photoirradiation in solid state of compound 3 and 4, there are two or three kinds of spin centres after photoirradiation: one is 2-nitropropane or TEMPO radical, and another is photo-generated radical of two indanione moieties. The color and magnetic of the solid compound 4 can be photomodulated.