Subtle structural variation in copper metal-organic frameworks: syntheses, structures, magnetic properties and catalytic behaviour

摘要

Two new copper metal-organic frameworks containing 5-nitro-1,3-benzenedicarboxylate (5-nbdc) have been prepared from the reaction between Cu(NO3)(2)center dot 3H(2)O and H-2(5-nbdc) in DMF at different temperatures. Single crystal X-ray structures of {[Cu-2(5-nbdc)(2)(DMF)(2)]center dot 2DMF}(infinity) (1) and {[Cu-2(5-nbdc)(2)(DMF)(2)] center dot 3 1/3 DMF}(infinity) (2) revealed similar sheet structures, containing triangular and hexagonal pores, but differences in the stacking of the sheets. Magnetic measurements on 1 and 2 are consistent with antiferromagnetic dimers containing a small quantity of paramagnetic impurity. The desolvated forms of 1 and 2 were applied as Lewis acid catalysts in the acetylation of methyl 4-hydroxybenzoate. When the reaction between Cu(NO3)(2)center dot 3H(2)O and H-2(5-nbdc) was carried out in a mixture of DMF and water, the reaction gave metallomacrocycles of formula [Cu-6(5-nbdc)(6)(H2O)(12)(DMF)(6)] (3). These assemble through hydrogen-bonding interactions to form a gross structure in which the macrocycle pores align into channels. The reaction between Cu(NO3)(2)center dot 3H(2)O and 5-methylsulfanylmethyl-1,3-benzenedicarboxylic acid, H-2(5-msbdc), in DMF-water gave {[Cu-2(5-msbdc)(2)(OH2)(2)]center dot 3DMF}(infinity) (4), which contains similar sheets to those in 1 and 2, whereas the reaction with 5-amino-1,3-benzenedicarboxylic acid, H-2(5-abdc), gave {[Cu-2(5-abdc)(2)(DMF)(2)]}(infinity) (5), which has a previously reported network based on sheets containing rhombohedral pores. The reaction between Cu(NO3)(2)center dot 3H(2)O and 2-methoxy-1,3-benzenedicarboxylic acid, H-2(2-mbdc), in DMF gave [Cu-2(2-mbdc)(2)(DMF)(2)] (6). The presence of the substituent in the 2-position removes the co-planarity of the carboxylate groups, and the sheet structure adopted by 6 contains rhomboidal pores.