Diverse mixed-ligand metal complexes with in situ generated 5-(pyrazinyl)tetrazolate chelating-bridging ligand: in situ synthesis, crystal structures, magnetic and luminescent properties

The purpose of this work is to systematically investigate the influence of the functional co-ligands and metal ions on the self-assembly and properties of the in situ generated 5-(pyrazinyl)tetrazolate (ptz(-))based metal complexes. A series of nine metal complexes, {[Co-3(H2O)(4)(ptz)(2)(btec)]center dot 5H(2)O}(n) (1), [Cu-2(H2O)(4)(ptz)(2)(H(2)btec)](n) (2), [Hg-2(ptz)(2)Cl-2](n) (3), [Hg-3(H2O)(2)(ptz)(4)(mu(1,1)-N-3)(2)]center dot 2H(2)O (4), Hg(H2O)(2)(ptz)(2) (5), [Cd-2(H2O)(2)(ptz)(2)(ox)](n) (6), [Cd(H2O)(ptz)I](n) (7), {[Cd(H2O)(ptz)X]center dot H2O}(n) (X = Br for 8 and Cl for 9) (btec 1,2,4,5-benzenetetracarboxylate and ox = oxalate), was obtained by a subtle variation of co-ligands and metal ions, in which the Hg-II ion is firstly observed as an efficient Lewis acid to catalyze the in situ reaction. Significantly, resulted from the cooperative and/or competitive binding between the mixed ligands and the metal ions with different coordination geometry, complexes 1-9 feature interesting structural subunits (mono-, bi- and tri-metallic core) and various dimensionalities ranged from polymeric three-dimensional (3D) frameworks to discrete zero-dimensional (0D) entities. Three high-dimensional complexes with a binodal (3,8)-connected tfz-d microporous framework for 1, a trinodal (3,4)-connected unusual (6.8(2))(2)(6.8(3).10(2)) topology for 3, and a six-connected alpha-polonium-type network for 6 are observed, respectively. Complexes 2 and 7-9 are bi-metallic node-based 2D layers (7) and 1D chains (2, 8, and 9). In contrast, the rarely linear tri-metallic core and commonly observed mononuclear entities are generated for 4 and 5, respectively. Additionally, Cu-II-based polymer 2 displays weak intra-dimeric antiferromagnetic coupling interaction. Complexes 1 and 3-9 with considerable metal ion-dependent thermal stability exhibit ptz(-)-based photoluminescence with variable intensity.