Structural diversity directed by switchable coordination of substitute groups in a ternary CuII-triazole-sulfoisophthalate self-assembly system: synthesis, crystal structures and magnetic behavior

Four magnetic samples with different building blocks and dimensionalities, {[Cu-4(atr)(2)(mu(3)-OH)(2)(sip)(2)]center dot 4H(2)O}(n) (1), {[Cu-4(atr)(2)(H2O)(8)(mu-OH)(2)(sip)(2)]center dot 1.3CH(3)OH center dot 0.7H(2)O}(n) (2), {[Cu-3(atr)(4)(H2O)(2)(sip)(2)]center dot 4H(2)O}(n) (3) and{[Cu-3(atr)(4)(H2O)(2)(mu(3)-OH)(sip)(Hsip)]center dot 2CH(3)OH center dot 2.75H(2)O}(n) (4) (atr = 4-amino-1,2,4-triazole and sip(3-) = 5-sulfoisophthalate), were obtained and characterized structurally and magnetically. Complex 1 exhibits a three-dimensional (3D) robust framework with butterfly-like Cu-4(II) clusters periodically extended by tetratopic sip(3-) connectors. Complex 2 possesses a 2D layer with alternating Cu-3(II) + Cu-1(II) chains crosslinked by pairs of ditopic sip(3-) linkers. By contrast, the latter two entities feature 1D broad ribbons with linear (for 3) and triangular Cu-3(II) cores (for 4) propagated by bidirectional sip(3-) connectors. Structural analysis reveals that the diverse building blocks and dimensionalities of 1-4 are significantly dominated by the tunable coordination of exocyclic amino- and/or sulfonate-group of the mixed ligands. Magnetically, antiferromagnetic interactions with variable strength transmitted by -NN- moiety of atr and hydroxyl mediators result in overall S = 0 (for 1) and 1/2 (for 3 and 4) spin ground states. These interesting results indicate that coordinative side group in the ternary metal ion-azolate-carboxylate system can be utilized to generate aesthetically pleasing building units and variably polytopic connectors, leading to differently extended superstructures and magnetic behavior.