Based on the 4-substituted 1,2,4-triazole derivate ligand 4-benzene-1,2,4-triazole (L), a series of crystalline coordination complexes varying from mononuclear to trinuclear species, namely, [Zn­(L)2­Br2] (1), [Zn­(L)2­Br2] (2), [Fe­(L)4­(NCS)2]2 (3), [Fe2­(μ2-L)3­(L)2­(NCS)4]·CH3OH·CH3CH2­OH (4), [Fe2­(μ2-L)3­(L)2­(NCS)4]·2CH3CH2­OH (5), [Fe2­(μ2-L)3­(L)2­(NCS)4]·2CH3CH2­OH·1.5H2O (6), and [Ni3­(μ2-L)6­(L)4­(H2O)2]­(NO3)6·15.5H2O (7), have been isolated. 1 and 2 present a temperature-induced polymorphic phenomenon of two zinc­(II) coordination complexes with L. The solvent effect plays the key role for the self-assembly of these Fe­(II) complexes 3–6: 3 contains mononuclear Fe­(L)4(NCS)2 units without spin-transition behavior, whereas both 4 and 5 present binuclear Fe­(II) complexes with three N1,N2-1,2,4-triazole bridges exhibiting incomplete spin-transition behavior. The low-temperature X-ray structural analysis (100 K) of 4 also confirms that one of the Fe­(II) centers is located at the low-spin (LS) state and the other Fe­(II) center is located at the high-spin (HS) state. Interestingly, when the binuclear Fe­(II) complex 5 was exposed in the water atmosphere, solvent-induced single crystal-to-single crystal transformation can be observed, and the binuclear Fe­(II) complex 6 exhibiting antiferromagnetic interactions can be isolated. Further, a trinuclear crystalline compound is isolated when Ni­(II) salts were used to react with L. Variable-temperature magnetic susceptibility measurement (2–300 K) reveals antiferromagnetic interactions in 7. The polymorphic phenomenon (1 and 2), incomplete spin-transition phenomenon (4 and 5), and single crystal-to-single crystal transformation (from 5 to 6) also reveal great potential in the construction of these novel functional materials with L.

In this work the multi-dentate 4-amino-benzene-1,2,4-triazole (L 1 ) ligand is used. A series of novel clusterbased micro-porous luminescent cadmium(II) frameworks, namely [Cd 3 5H 2 O} n (3) have been isolated under hydrothermal conditions. 1 presents a 4-connected (4,4) topology using trinuclear Cd(II) clusters as basic nodes. For 1, two bridging m 2 -Cl À anions and two bridging m 3 -L 1 ligands connect three neighboring Cd II ions forming trinuclear Cd 3 clusters. Each Cd 3 cluster links four neighboring Cd 3 clusters forming a 2D (two-dimensional) neutral micro-porous framework. 1D rhombic channels with dimensions of 7.594(2) Å Â 21.250(6) Å can be observed along the c-axis. 2 presents a rare I 1 O 3 hybrid type micro-porous framework. In 2 these bridging m 3 -L 1 ligands link central Cd II ions forming a 3D Cd-L 1 organic connectivity. Two kinds of 1D Cd-Br-Cd inorganic connectivities further consolidate the 3D Cd-L 1 organic connectivity, which ultimately forms a rare I 1 O 3 type hybrid framework. 3 presents a novel 3D cluster-based micro-porous cation framework containing 1D channels, in which guest CdI 4 2À anions and water molecules are located. Topological analysis indicates that 3 presents a novel 4-connected dmp topology using binuclear Cd 2 I 2 clusters as basic nodes. PXRD, TGA and Gas absorption experiments for 1-3 have also been carried out. Solid state photo-luminescent spectra of 1-3 have been determined indicating strong emission bands. For 1 selective photo-luminescent quenching for NO 2 À anions can be observed. The result also reveals that L 1 can adopt various different coordinated modes and flexible spatial distortion dihedral angles (between aromatic benzene and triazole rings), which has great potential in the construction of these novel cluster-based micro-porous coordination frameworks.

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Two aliphatic dicarboxy1ic acid ligands, iminodiacetic acid (H 2 L 1 ) and 3,3-thiodipropionic acid (H 2 L 2 ), were used to construct two novel lead(II) frameworks, namely, [Pb(μ 4 -L 1 )Br] n (1) and [Pb 3 (μ 9 -L 2 )(μ 2 -Br) 2 Br 2 ] n (2), under hydrothermal conditions. It has to be noted that for 1 the central Pb II ions are bridged by L 2ligands resulting in infinite right-and left-handed helical Pb-(O-C-O)-Pb linkage. Compound 2 represents a novel 3D hybrid luminescent lead(II) framework with I 3 O 0 type connectivity. For 2 infinite 2D Pb-O-Pb inorganic layers and trinuclear Pb 3 Br 4 clusters are inter-linked forming a 3D inor-

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