ic9b03357_si_001.pdf (4.25 MB)
Variation of the Chain Geometry in Isomeric 1D Co(NCS)2 Coordination Polymers and Their Influence on the Magnetic Properties
journal contribution
posted on 2020-02-24, 18:08 authored by Michael Böhme, Aleksej Jochim, Michał Rams, Thomas Lohmiller, Stefan Suckert, Alexander Schnegg, Winfried Plass, Christian NätherTwo different isomers
of [Co(NCS)2(4-chloropyridine)2]n (3C and 3L) were synthesized
from solution and by thermal decomposition of Co(NCS)2(4-chloropyridine)2(H2O)2 (2), which show
a different metal coordination leading to corrugated chains in 3C and to linear chains in 3L. Solvent mediated
conversion experiments prove that 3C is thermodynamically
stable at room temperature where 3L is metastable. Magnetic
measurements reveal that the magnetic exchange in 3L is
comparable to that observed for previously reported related chain
compounds, whereas in 3C with corrugated chains, the
ferromagnetic interaction within the chains is strongly suppressed.
The magnetic ordering takes place at 2.85 and 0.89 K, for 3L and 3C, respectively, based on specific heat measurements.
For 3L the field dependence of magnetic relaxations in
antiferromagnetically ordered ferromagnetic chains is presented. In
addition, 3L is investigated by FD-FT THz-EPR spectroscopy,
revealing a ground to first excited state energy gap of 14.0 cm–1. Broken-symmetry DFT calculations for 3C and 3L indicate a ferromagnetic intrachain interaction.
Ab initio CASSCF/CASPT2/RASSI-SO computational studies reveal significantly
different single-ion anisotropies for the crystallographically independent
cobalt(II) centers in 3C and 3L. Together
with the geometry of the chains this explains the magnetic properties
of 3C and 3L. The ab initio results also
explain the weaker exchange interaction in 3C and 3L as compared to previously reported [Co(NCS)2(L)2]n compounds with linear
chains.
