| Recent years, the self-assembly of molecular building blocks, as the well-established technique has exhibitted promissing applications in functional molecular devices. Multicomponent self-assembly systems could possess multiple properties through efficient selective recognition of the building units. Among them magnetic material with spin-crossover(SCO) properties attracted unprecedented attention of researchers at home and abroad relying on its potential application in molecular memory switch. Therefore, it’s of important significance for the synthesis and design of magnetic bistable complexes with different spatial structure and excellent processing performance. The work in our paper is focused on the design and synthesis of a series of bidentate/tridentates complexes. And the SCO properties are controlled by changing ligand strength by the means of supporting on the resin, replacing ligands’ substituents. Self-sorting behaviors of competitive building blocks in self-assembly system are investigated preliminarily. This thesis will be divided into three parts:1. Using chiral imidazole Schiff-base as ligands, two couples of mononuclear iron(II) enantiomeric complexes with different anions(Cl O4- or BF4-) 1-4 have been successfully synthesized and characterized. X-ray crystallography revealed that complexes 1-4 all crystallize in the chiral space group P213 with the iron(II) center coordinated to chelating moieties from three bidentate ligands. The CD spectra of 1 and 2, 3 and 4, were basically mirror images confirming their enantiomers presenting single configuration Λ or Δ. Magnetic measurements revealed incomplete spin transition for 1 and 2, and gradual spin crossover(T1/2 = 150 K) for 3 and 4. In order to improve the processing performance of complexes, complexes 1-4 were grafted to Merrifield’s peptide resin step by step to form the polymer-supported compounds 5-8. The scanning electron microscope(SEM) test indicates that the resins grafted with chiral complexes were coated with a layer of numerous particles with an average size of ~100 nm. However, the spin-crossover behaviors were vanished after grafting 1-4 to the merrifield’s peptide resin, and the iron(II) centers in the resin remained high-spin state in the temperature range of 2-300 K.2. A series of binuclear iron(II) imidazole Schiff-base complexes 9-15 were constructed by one-pot multi-component self-assembly of di(imidazole aldehyde), polyamine and Fe(OTf)2 under solvent-free grinding conditions. They have been characterized detailedly by elemental analysis, IR spectra, UV spectra, 1H NMR analysis, PXRD analysis and TG test. X-ray crystallography revealed that the seven complexes crystallize in various space groups of Cmca for 9, P21/C for 10-12, C2/c for 13, P1 for 14 and Pna21 for 15. The molecular structures of 9-11, and 13-15 display Fe2L2 arrangement, while 12 exhibits Fe2LL’ arrangement. In 9-13 and 15 two ligand strands wrap around two Fe2+ ions. Complex 14 forms the cyclic binuclear structure with two Fe2+ ions embedded in one cyclic ligand. 1H NMR results suggest that two muti-component self-assembly systems with competitive building blocks are found to solid self-sorting. And heteromer 12 composed of two different ligands is obtained by social self-sorting in system I. Compared with self-sorting in solution, the solvent-free grinding self-sorting is more efficient due to the certain restrictions of molecular movement.3. Based on the special [2 + 2] molecular design between di(imidazole aldehyde) and polyamine, iron(II) complexes 16-24 with different bridging groups on imidazole rings or polyamine substituents have been successfully prepared in solution. X-ray crystallography revealed that complex 24 crystallize in the space group C2/c and this complex is heteroleptic involving single imidazole aldehyde and di(imidazole aldehyde). Variable temperature magnetic test indicates that the SCO behaviors of iron(II) complexes are vulnerable to influence of the bridging groups between imidazole rings and the kinds of polyamine. |
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