Three pimelato-bridged Cu(II) phenanthroline complexes: [Cu₂(phen)₂(H₂O)₂L₂]·4H₂O, α- and β-[Cu₂(phen)₂L₂]·4H₂O, H₂L = HOOC(CH₂)₅COOH

Abstract

Reaction of CuCl₂·2H₂O, 1,10-phenanthroline (phen) and pimelic acid with Na₂CO₃ in aqueous methanol afforded a mixture consisting of [Cu₂(phen)₂(H₂O)₂(C₇H₁₀O₄)₂]·4H₂O (1), α-[Cu₂(phen)₂(C₇H₁₀O₄)₂]·4H₂O (2) and β-[Cu₂(phen)₂(C₇H₁₀O₄)₂]·4H₂O (3) at pH = 5.8. The structure of compound 1 has been reported earlier, and consists of hydrogen bonded H₂O molecules and dinuclear [Cu₂(phen)₂(H₂O)₂(C₇H₁₀O₄)₂] molecules generated from pimelate anions, acting as bis(monodentates), bridging square pyramidal Cu ions. The structures of dimorphs 2 and 3 have been established using single-crystal X-ray diffraction methods. They are monoclinic and triclinic, respectively (2: C2/c, a = 20.344(2), b = 9.828(1), c = 20.802(2) Å, β = 116.10(7)°, Z = 4, D _calc = 1.558 g cm⁻³; 3: ī, a = 10.124(2), b = 10.658(2), c = 10.847(2) Å, α = 111.36(3), β = 116.27(3), γ = 93.80(3)°, Z = 1, D _calc = 1.529 g cm⁻³). The structures of all three complexes are compared. Both 2 and 3 are composed of hydrogen bonded H₂O molecules and polymeric

chains, in which dimeric Cu₂N₄O₄ units with square pyramidal coordination geometry are bridged by pimelate anions. The dinuclear molecules in 1 and polymeric chains in 2 and 3 are assembled via π–π stacking and weak C–H···O hydrogen bonds into 2D layers, linked by hydrogen bonds.

Keywords:

• Coordination polymer
• Copper
• Pimelic acid
• Phenanthroline
• Crystal structure
• Supramolecular assembly

Acknowledgements

This project was supported by the National Natural Science Foundation of China (20341006), the Expert Project of Key Basic Research of the Ministry of Science and Technology of China (2003CCA00800), the Zhejiang Provincial Natural Science Foundation (Z203067) and the Ningbo Science and Technology Bureau (2003A61014, 2003A62026).