Synthesis And Characterization Of Large-ring Coordination Compounds With Bidentate Betaine Derivatives

The molecular and crystal structure of a crystalline solid determines its macroproperties. In the past decades, the crystal engineering, which studies the relationshipof the non-bonding interactions between molecules and the topologic structures ofcrystals, has been extensively developed, and become one of the most active area inchemical researches. In crystal engineering, hydrogen-bonding occupies a veryimportant position. Other factors such as π–π stacking, C H πweak interaction,the charge, size and shape of counter ions also influence the topologic structure andits stability of the resulting compounds. The properly choice of organic ligands andmental ions will lead to a variety of structures.In present research, two bidentate betaine derivatives1,5-bis（4–carboxypyridinium）-N-methyl-diethylamine （L1）_and1,5-bis（3-carboxypyridinium）-N-methyl-diethylamine （L2）, which have two naked carboxylate groups, multiple aromaticrings and a reflexable N-methyl-diethylamine chain, have been adopted to react withvarious transition metal and rare earth metal salts. Eight coordination compounds anda covelent-like hydrogen-bonding compound, namely,{[CuCl₂L1（H₂O）₃]2H₂O}_n（1）,{[Cu（ClO4）₂L1（H₂O）₃]2H₂O}_n（2）,{[Cd₂（PF₆）₄（L1）₄（H₂O）₆]2H₂O}_n（3）,{[Zn₂（PF₆）₄（L1）₄（H₂O）₆]2H₂O}_n（4）,{[Cd₂（ClO₄）₃P F₆（DMSO）₄（L1）₂（H₂O）₂] H₂O}_n （5）,{[AgNO3C NMeL1] H₂O}_n（6）,{[Er（ClO₄）₃（DMF）₂（HCl）₂（H₂O）₃（L1）₃]4H₂O}_n （7）,{[Nd₂（ClO₄）₆（DMF）₆（H₂O）₂（L2）₄]4H₂O}_n（8）,{H3（L2）₂（PF₆）₃}_n （9）,have been prepared and their molecular and crystal structures have been determinedby single crystal X-ray diffraction structural analysis. In addition, these compoundsare also characterized by IR spectroscopy and thermal analysis.The results show that （1）_all compounds except9contain35–（or36–）_memberedrings, which is formed through bridging of two metal ions by a pair of ligandmolecules or hydrogen bonds between carboxylate groups and aqua ligands.Compound6is a coordination polymer, and others are disreate molecules containingone or multiple35–（or36–）_membered rings;（2）_compounds1and₂contain Cu（Ⅱ）as their center ion. The Cu（Ⅱ）_atom is ligated by five oxygen atoms in a distortedtrigonal bipyramidal coordination sphere owing to the John-Teller effect of d9electronic configuration of Cu（Ⅱ）;（3）_compounds3and4are iso-structure, in which the center ions are Cd（Ⅱ） and Zn（Ⅱ）, respectively. In the compounds, the two centerions bridged by a pair of aqua ligands is ligated by four L1molecules andmonodentate water molecules. The coordination free carboxylate groups form stronghydrogen bonds with aqua ligands thus form a butterfly-like discreate cation, whichextend to a brick-wall like two dimensional topological structure;（4） compared with3,in compound5, the coordination mode of Cd（Ⅱ） and stacking fashion of thecompound changes drastically due to the different solvents and anion used.（5） In6,the Ag（I） atoms are tridentate coordinated in a pyramid sphere, and are bridged by themolecules of L1forming a coordination polymeric chain. The polymers are joined byhydrogen bonds thus form a two dimensional honeycomb-like structure;（6） both in7and8, the rare earth metal cations are highly coordinated, and hydrogen-bondingthree-dimensional structures are formed by bonds between carboxylate groups andaqua ligand or coordination free water molecules.