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

Abstract

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.