Guido Leibeling

A novel 2D net-like supramolecular polymer constructed from Ln6Cu24 node and trans-Cu(Gly)2 bridge

A 2D net-like lanthanide-copper heterometallic supramolecular network {Ln6Cu27} 1 was synthesized with Ln6Cu24 octahedral cluster as the node and trans-Cu(glycinato)2 group as the linker. The compound represents the first example of 2D polymer with high-nuclear 3d–4f heterometallic cluster as the node.

Targeted construction of azido-bridged Ni4 complexes with decisive effect of µ-1,3-azide torsion on the spin ground state

Highly preorganized pyrazolate-based dinickel(II) systems are shown to constitute suitable building blocks for the targeted assembly of azido-bridged Ni4 complexes with rectangular arrangement of the metal ions. A set of such complexes has been prepared and structurally characterized. mu-1,1-Azide binding within the bimetallic sub-units is controlled by the chosen topology of the pyrazolate ligand scaffold and gives rise to the anticipated ferromagnetic intradimer coupling. Overall magnetic properties of the Ni4 array, however, are mainly determined by the Ni-NNN-Ni torsion of the interdimer mu-1,3-azido linkages. According to the crystallographic results, these torsion angles vary over a wide range, and partial disorder of the mu-1,3-azide bridge in one of the compounds indicates high structural flexibility even in the solid state. Two of the compounds represent rare examples of molecular complexes with a Ni-NNN-Ni torsion angle of almost exactly 90 degrees . The resulting magnetic ground state (neglecting zero-field splitting) is either S = 0 or S = 4 depending on the Ni-NNN-Ni torsion, and in one case a drastic change is observed upon extrusion of lattice solvent.

Magnetism of a novel tetranuclear nickel(II) cluster in strong magnetic fields

High frequency Electron Spin Resonance (ESR) up to ν = 1 THz and magnetization M(B) of a tetranuclear-Ni(II) single molecular complex of type [L2Ni4(N3)(O2CAda)4](ClO4) featuring an unprecedented central μ4 - 1,1,3,3 azide have been studied in magnetic fields up to B = 55T. Bridging ligands provide intramolecular exchange paths of different strength between the four Ni ions each having a spin SNi = 1. T- and ν-dependent ESR measurements enable to accurately determine the energy spectrum of the spin states of the cluster as a function of B. A predominantly antiferromagnetic character of exchange renders the ground state nonmagnetic, S = 0, with a number of excited magnetic multiplet states, S = 1,. . . ,4. Remarkably, ESR gives evidence for the spin-level crossing in a field of ~ 25T which turns the ground state of the cluster to a strongly magnetic one. This observation is confirmed by the static M(B) data.

1,3,5-Triazine-based tricopper(II) complexes: structure and magnetic properties of threefold-symmetric building blocks

Two new trinuclear complexes 1 and 2 that are composed of the three-directional ligand 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine (dipyatriz) and copper(II) chloride as well as a 1D polymeric zigzag system 3 assembled from trimetallic type 2 building blocks have been prepared and structurally characterized. While the triazine-N are not involved in metal coordination, each ligand bidentately binds to three copper ions via its three pairs of pyridine-N donors, and five-coordination of the copper is completed by chloride or dmso solvent molecules. Variable-temperature magnetic studies reveal weak antiferromagnetic coupling. Magnetic properties of the trinuclear entities and of the bis(micro-chloro) bridged pseudo-dimeric copper(II) subunits in 3 can be rationalized on the basis of the structural findings.