Studies On Crystal Structures And Properties Of Self-Assembled Organo-Metal Coordination Polymers By 1,2-Bis(pyridylamide)benzene And 3d Metal

In this paper , two U-shaped ligands which are based on 1,2-benzenediamine and 3 (or 4)-pyridine carboxylic acid were synthesized. Both of the ligands are a subfamily of bis(pyridyl) by incorporating amide groups into bis(pyridyl) backbone to form bis(amidopyridine) ligands . Ligand L₁ is 1, 2-bis (3-pyridylcarboxamide)-benzene (H₂bpb) and ligand L₂ is N,N'-(1,2-phenylene)diisonicotinamide (pia). Six novel organo-metal coordination polymers and one supramolecular complex have been synthesized by treatments of the synthesized ligands and transition metal. The complexes include [Co (H₂bpb)₂ (NCS)₂ (CH₃OH)₂]( I 1), [Zn(H₂bpb)Cl₂ ]_n·nCH₃OH (I 2), [Ni₂(H₂bpb)₂(H₂O)₂(CH₃OH)₂(SO₄)₂]_n·nCH₃OH ( I 3), [Co₂(H₂bpb)₂(CH₃OH)₂ (DMF)₂(SO₄)₂]_n·0.5nH₂O( I 4), [Zn₂(H₂bpb)₂(CH₃OH)₂(DMF)₂(SO₄)₂]_n·0.5nH₂O ( I 5), [Cu(pia)(CH₃OH)₂(SO₄)]_n·0.5nH₂O(II 1), [Zn (pia) (SO₄)]_n·2nH₂O( II 2), which have been characterized by X-ray diffraction analyses, IR spectra and thermal analyses. Except [Co (H₂bpb)₂ (NCS)₂ (CH₃OH)₂]( I 1) which is a mononuclear complex, all the others are coordination polymers.Self-assembly course of the ligand L₁, 1,2-bis(3-pyridylcarboxylamide)benzene (H₂bpb), with nickel (II) sulfate, cobalt (II) sulfate and zinc (II) sulfate, respectively, gave rise to three new coordination polymers I3, I4 and I 5. They all crystallize in a monoclinic space group C2/c and have two crystallographically distinct metal nodes in their asymmetric units. In their crystal structures almost similar chair-like units constructed by aμ-SO₄^2- anion and U-shaped ligand H₂bpb bridging the same metal centers are threaded to form 1-D structures through sharing the same metal nodes. The ligand H₂bpb displaying a trans, trans, syn conformation with Cs symmetry which is further stabilized by intramolecular hydrogen bonding in chair-like units, interestingly, controls over the assembled architecture.Reaction of the ligand L₂, N,N'-(1,2-phenylene)diisonicotinamide (pia), with metal( II) salts MSO₄ (M= Cu, Zn ) leads to the formation of two 2-D coordination networks [Cu(pia)(CH₃OH)₂(SO₄)]_n·0.5nH₂O( II 1), and [Zn (pia) (SO₄)]_n·2nH₂O (II 2). In the solid state of II1, the Cu( II) centers adapt an five-coordination pyramidal geometry, and the network is generated through the interconnection of the pia organic moieties with [Cu₂(SO₄)₂] dimers; in the case of II2, the Zn( II) centers adapt a tetrahedral coordination geometry and the 2-D network is formed by pia with another type of connector, zigzagμ-SO₄^2--Zn chains. In all these cases, 3D network structures are formed through formation of intermolecular hydrogen bonds NH…O-C, and these porous networks contain large solvent-filled channels with nano-dimensions.We report the synthetical course and the structure of ligands and complexes. Fluorescent and thermal properties and thermal decomposition kinetic about the complexes and ligands are also investigated. From the figures of fluorescence we find that because there is no significant shift in emission energy for the related complexes( I 1- I 5,II1,II2), the emission is neither MLCT (metal-to-ligand charge transfer) nor LMCT (ligand-to-metal charge transfer) in nature. We tentatively assign it to be the intraligand (Ï€-Ï€^*) charge transfer (LLCT), since a similar emission withλ_max is also observed for free ligand. We have studied the thermal behaviors of complexes by thermogravimetry (TG) and differential scanning calorimetry (DSC)and choosed two complexes to study the kinetic parameters of thermal decomposition . Based on the results of TG, the kinetic parameters of thermal decomposition have been calculated by employing method of Ozawa-Flynn-Wall or Friedman equation. All the research of the structure and properties can help us to understand complex for further application.