Four tetrazolate (tz(-))-based magnetic metal-organic frameworks, [Cu5(μ3-OH)2(SO4)2(tz)4]n (), {[Cu3(tz)4Cl2]·1.4CH3OH}n (), [Cu(N3)(tz)]n () and {[Cu5(tz)9]Cl·4H2O}n (), were hydro/solvothermally synthesized, and structurally and magnetically characterized. Structural analyses reveal that the former two samples exhibit the same eight-connected topological framework assembled from different subunits. Hourglass-shaped {Cu5(μ3-OH)2}(8+) cores in are periodically extended by mixed μ3-/μ4-tz(-) and μ4-SO4(2-) heterolinkers, while the linear {Cu3(μ-Cl)2}(4+) blocks in are repeatedly intersected by ditopic μ3-tz(-) connectors. In contrast, the square grid-shaped network of is constructed from linear {Cu(μ1,1-N3)}(+) chains and μ3-tz(-) linkers. Complex consists of trigonal-prismatic {Cu8(μ3-tz)6}(10+) subunits, which are interlinked into hexagonal microporous architecture by mirror-symmetry μ4-tz(-) ligands. Thus, the various subunits of are significantly tuned by the co-coordination of the inorganic anions and/or the azido co-ligand, and the backbone extensions are directed by the polytopic tetrazolate ligand. Magnetically, different ordering arrangements of the non-zero magnetizations produced in the local Cu(II)5 and Cu(II)3 subunits eventually lead to unusual ferrimagnetic and canted antiferromagnetic properties in and . Strong antiferromagnetic couplings mediated by the mixed tz(-) and/or azido bridges result in overall S = 0 spin ground-states of and .
Three extended three-dimensional (3D) magnetic metal-organic frameworks (MMOFs), {[Mn3(H2O)2(atz)4Cl2]·2CH3OH}n (1), {[Mn2(H2O)(atz)2(ip)]·C2H5OH}n (2) and {[Mn2(H2O)2(atz)(btc)]·3H2O·0.7CH3OH}n (3) (atz(-) = 5-aminotetrazolate, ip(2-) = isophthalate and btc(3-) = 1,3,5-benzenetricarboxylate), were respectively obtained by varying the coligands with different numbers of functionalities and molecular topology, and structurally and magnetically characterized. Complex 1 exhibits an eight-connected 3(6)·4(18)·5(3)·6 topological network with linear Mn(II)3 subunits periodically linked by ditopic atz(-) connectors. Complex 2 possesses a pillared-layer framework constructed from undulated {Mn2(atz)2} layers and bidirectional ip(2-) spacers. By contrast, 3 consists of bent one-dimensional (1D) {Mn(atz)} ribbons, which are crosslinked through the carboxylate groups of tripodal btc(3-) connectors to generate a 3D architecture. Structural analysis reveals that the interesting motifs of 1-3 and their diverse linkages are significantly dominated by the cooperate coordination of the mixed ligands to the octahedral Mn(II) ion. Magnetically, 1 displays ferrimagnetic behavior resulting from the periodic arrangement of the net moment in the Mn(II)3 subunit, which is scarcely observed in the homometallic azolate systems. Complex 2 features unusual coexistence of spin-canted antiferromagnetic behavior and field-induced spin-flop transition due to the asymmetric magnetic superexchange within the two-dimensional (2D) {Mn2(atz)2} sublayer. By contrast, only antiferromagnetic ordering is observed in the 1D {Mn(atz)} ribbon of 3. These interesting results suggest that the diverse structural motifs by the cooperate coordination of octahedral Mn(II) ion with the N-rich tetrazolyl group can more significantly direct the magnetic behaviors and could be hopefully utilized upon the construction of novel MMOFs.
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