Structural and Magnetic Properties of Layered Copper(II) Coordination Polymers Intercalating s and f Metal Ions

The nanoporous coordination polymer [Cu(pyrimidin-2-olate-N1,N3)2]n (1C) of the sodalite zeotype sorbs a variety
of metal nitrates [M(NO3)m, M = Na+, K+, Rb+, Tl+, Ca2+, Sr2+, Ba2+, Pb2+, La3+, Nd3+, Gd3+, Er3+] from H2O/MeOH
solutions, with a concomitant structural change to a layered [Cu(pyrimidin-2-olate-N1,N3)2]n·[M(NO3)m]n/2 (MNO3@1L)
coordination framework. Single-crystal X-ray diffraction analyses revealed that the layers are based on Cu4(pyrimidin-2-olate-N1,N3)4 square grids of copper(II) ions bridged by N1,N3 exobidentate ligands, displaying a structural motif
of the metallacalix[4]arene type in pinched cone conformation. The interlayer space is occupied by the guest metal
nitrates, each metal being coordinated by (at least) the four oxygen atoms of a metallacalix[4]arene. Magnetic
measurements on the MNO3@1L series denoted a weak ferromagnetic ordering taking place below the Néel
temperatures (typically close to 35 K), arising from spin-canting phenomena of the antiferromagnetically coupled
copper centers. When M = Nd3+, Gd3+, or Er3+, additional magnetic ordering is observed at lower temperatures,
which, on the basis of static and dynamic magnetic susceptibility measurements, can be attributed to copper−
lanthanide interactions.