Influence of metal coordination and co-ligands on the magnetic properties of 1D Co(NCS)2 coordination polymers. Issue 4 (13th January 2017) - Rams, Michał
Abstract : Two 1D Co(NCS)2 coordination polymers were synthesized and their magnetic properties were investigated by susceptibility and specific heat measurements as well as DFT and ab initio calculations. Abstract : Two new transition metal thiocyanate coordination polymers with the composition [Co(NCS)2 (4-vinylpyridine)2 ] n (1 ) and [Co(NCS)2 (4-benzoylpyridine)2 ] n (2 ) were synthesized and their crystal structures were determined. In both compounds the Co cations are octahedrally coordinated by two trans -coordinating 4-vinyl- or 4-benzoylpyridine co-ligands and four μ-1, 3-bridging thiocyanato anions and linked into chains by the anionic ligands. While in1 the N and the S atoms of the thiocyanate anions are also in trans -configuration, in2 they are in cis -configuration. A detailed magnetic study showed that the intra-chain ferromagnetic coupling is slightly stronger for2 than for1, and that the chains in both compounds are weekly antiferromagnetically coupled. Both compounds show a long range magnetic ordering transition at T c = 3.9 K for1 and T c = 3.7 K for2, which is confirmed by specific heat measurements. They also show a metamagnetic transition at a critical field of 450 Oe (1 ) and 350 Oe (2 ), respectively. Below T c 1 and2 exhibit magnetic relaxations resembling relaxations of single chains. The exchange constants obtained from magnetic and specific heat data are in good accordance with those obtained from constrained DFT calculations carried out on isolated model systems. The ab initio calculations allowed us to find the principal directions of anisotropy.