Influence of the Coligand onto the Magnetic Anisotropy and the Magnetic Behavior of One-Dimensional Coordination Polymers

Abstract

Reaction of Co­(NCS)2 with different coligands leads to the formation of three compounds with the general composition [Co­(NCS)2(L)2] n (L = aniline (1), morpholine (2), and ethylenethiourea (3)). In all of these compounds the cobalt­(II) cations are octahedrally coordinated by two trans thiocyanate N and S atoms and the apical donor atoms of the coligands and are linked into linear chains by pairs of anionic ligands. The magnetic behavior was investigated by a combination of static and dynamic susceptibility as well as specific-heat measurements, computational studies, and THz-EPR spectroscopy. All compounds show antiferromagnetic ordering as observed for similar compounds with pyridine derivatives as coligands. In contrast to the latter, for 1–3 significantly higher critical temperatures and no magnetic single-chain relaxations are observed, which can be traced back to stronger interchain interactions and a drastic change in the magnetic anisotropy of the metal centers. These results are discussed and compared with those of the pyridine-based compounds, which provides important insights into the parameters that govern the magnetic behavior of such one-dimensional coordination polymers.

Crystal structure of bis(tetramethylthiourea-κS)bis(thiocyanato-κN)cobalt(II)

“…Independent of this, we used ethylenethiourea as coligand and obtained a compound with the composition [Co(NCS) 2 (ethylenethiourea) 2 ] n . Single-crystal structure determination proves that, in this case, the Co II cations are connected by pairs of thiocyanate ligands into chains, which corresponds exactly to the desired structure (Jochim et al, 2020). In contrast to the analogous compounds with N-donor coligands, this compound shows antiferromagnetic ordering but no relaxations of single chains.…”

“…Depending on the nature of the coligand, the metal cations are connected into chains by pairs of -1,3 coordinating anionic ligands (Mautner et al, 2018;Prananto et al, 2017;Shurdha et al, 2013;Jin et al, 2007;Bö hme et al, 2020), or they are linked into layers with different layer topologies (Werner et al, 2015a;Neumann et al, 2018a;Suckert et al, 2016). The chain compounds show either ferromagnetism (Neumann et al, 2019), antiferromagnetism (Jochim et al, 2020) or they represent antiferromagnetic phases of single-chain magnets (Mautner et al, 2018; Rams et al, 2017, 2020; Werner et al, 2015b), whereas the layer compounds are in most cases ferromagnets (Suckert et al, 2016). For this composition a third structure type is known, in which the metal cations are tetrahedrally coordinated, forming discrete complexes with only N-terminally bonded thiocyanate anions (Neumann et al, 2018b).…”

Synthesis, crystal structure and thermal properties of poly[bis[μ-3-(aminomethyl)pyridine-κ2 N:N′]bis(thiocyanato-κN)manganese(II)]

“…The majority of compounds with -1,3bridging thiocyanate anions shows this behaviour. Depending on the actual metal coordination (all-trans or cis-cis-trans), linear or corrugated chains are observed (Jin et al, 2007;Rams et al, 2017;Bö hme et al, 2020;Jochim et al, 2020 of compounds consist of structures with only terminally N-bonding thiocyanate anions, because in this case this coordination is energetically favoured. With only monocoordinating ligands this usually leads to the formation of discrete metal complexes with an octahedral coordination.…”

Crystal structure of bis(N,N′-dimethylthiourea-κS)bis(thiocyanato-κN)cobalt(II)

“…With nickel, two compounds with the composition Ni(NCS) 2 (ethylenethiourea) 2 (Nardelli et al, 1966) and Ni(NCS) 2 (thioacetamide) 2 (Capacchi et al, 1968) are known. We prepared the corresponding cobalt compound with ethylenethiourea, which is isotypic to the nickel analogue (Jochim et al, 2020a). Only one additional polymeric compound with the composition [Co(NCS) 2 (thiourea) 2 ] n is known, in which the cobalt cations are connected by the sulfur atoms of the coligands, while the thiocyanate anions are N-terminally coordinated (Rajarajan et al, 2012;Muthu et al, 2015).…”