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(NO 3 ) 2 and 3,4-pyridinedicarboxylic acid (3,4-pdcH 2 ) resulted in the formation of two series of 3 d–4f heterometallic coordination polymers: [Ln 2 Cu 3 (3,4-pdc) 6 (H 2 O) 12 ]· m H 2 O· n CH 3 OH (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)(H 2 O) 3 ]·8H 2 O (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 [Cu 3 (3,4-pdc) 6 (H 2 O) 3 ] n sheets pillared by Ln(H 2 O) 4 , showing an intriguing 3D 3 6 ·4 18 ·5 3 ·6 framework with the treatment of the Ln 2 Cu 3 unit as an 8-connected node. Complexes 4 and 5 (Form II) are constructed with (4,4)-connected 2D [Cu(3,4-pdc) 2 (H 2 O)] n sheets pillared by bimetallic units Ln 2 (OAc) 2 (H 2 O) 4 , exhibiting a fascinating 3D architecture with (4,8)-connected fluorite (4 12 ·6 12 ·8 4 )(4 6 ) 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.