Two series of novel 3D potentially porous heterometallic Cu–Ln coordination frameworks assembled by 3,4-pyridinedicarboxylic acid with different topologies and channels: syntheses, structures, luminescence and magnetic properties†
Self-assembly of rare earth salts, Cu(NO3)2 and 3,4-pyridinedicarboxylic acid (3,4-pdcH2) resulted in the formation of two series of 3 d–4f heterometallic coordination polymers: [Ln2Cu3(3,4-pdc)6(H2O)12]·mH2O·nCH3OH (Ln = Eu (1, m = 22, n = 0), Gd (2, m = 22, n = 0) and Tb (3, m = 15.5, n = 5)) and [LnCu(3,4-pdc)2(OAc)(H2O)3]·8H2O (Ln = Ho (4), Er (5)). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, PXRD and TGA. The structures of isomorphous complexes 1–3 (Form I) are constructed with irregular (4,4)-connected 2D [Cu3(3,4-pdc)6(H2O)3]n sheets pillared by Ln(H2O)4, showing an intriguing 3D 36·418·53·6 framework with the treatment of the Ln2Cu3 unit as an 8-connected node. Complexes 4 and 5 (Form II) are constructed with (4,4)-connected 2D [Cu(3,4-pdc)2(H2O)]n sheets pillared by bimetallic units Ln2(OAc)2(H2O)4, exhibiting a fascinating 3D architecture with (4,8)-connected fluorite (412·612·84)(46)2 topology. There exist different 1D channels in the polymers of Form I and Form II, in which solvent molecules are accommodated. Moreover, their luminescence and magnetic properties have been investigated.