Metamagnetism and Single‐Chain Magnetic Behavior in a Homospin One‐Dimensional Iron(II) Coordination Polymer

Abstract

Reaction of FeCl(2)·4H(2)O with KNCSe and pyridine in ethanol leads to the formation of the discrete complex [Fe(NCSe)(2)(pyridine)(4)] (1) in which the Fe(II) cations are coordinated by two N-terminal-bonded selenocyanato anions and four pyridine co-ligands. Thermal treatment of compound 1 enforces the removal of half of the co-ligands leading to the formation of a ligand-deficient (lacking on neutral co-ligands) intermediate of composition [Fe(NCSe)(2)(pyridine)(2)](n) (2) to which we have found no access in the liquid phase. Compound 2 is obtained only as a microcrystalline powder, but it is isotypic to [Cd(NCSe)(2)(pyridine)(2)](n) and therefore, its structure was determined by Rietveld refinement. In its crystal structure the metal cations are coordinated by two pyridine ligands and four selenocyanato anions and are linked into chains by μ-1,3 bridging anionic ligands. Magnetic measurements on compound 1 show only paramagnetic behavior, whereas for compound 2 an unexpected magnetic behavior is found, which to the best of our knowledge was never observed before for a iron(II) homospin compound. In this compound metamagnetism and single-chain magnetic behavior coexist. The metamagnetic transition between the antiferromagnetically ordered phase and a field-induced ferromagnetic phase of the high-spin iron(II) spin carriers is observed at a transition field H(C) of 1300 Oe and the single-chain magnetic behavior is characterized by a blocking temperature T(B), estimated to be about 5 K.

A Rational Route to Coordination Polymers with Condensed Networks and Cooperative Magnetic Properties

“…Magnetic measurements prove that the metamagnetic behavior is still present but in contrast to the thiocyanato analog, slow relaxations of the magnetization are observed below and above the critical field. In this context it is noted that only a few Fe II homospin SCM compounds are reported in literature and that this behavior was www.zaac.wiley-vch.de [174] never observed before in a selenocyanato coordination polymer. [174] Based on these results we investigated similar compounds with the bidentate ligands 4-bpa and 4-bpe.…”

“…In this context it is noted that only a few Fe II homospin SCM compounds are reported in literature and that this behavior was www.zaac.wiley-vch.de [174] never observed before in a selenocyanato coordination polymer. [174] Based on these results we investigated similar compounds with the bidentate ligands 4-bpa and 4-bpe. [Fe(NCS) 2 (4-bpe)] n is isotypic to its Co II analogue, which means that Fe(NCS) 2 chains are observed that are linked by the bidentate ligands into layers.…”

A toolbox of building blocks, linkers and crystallisation methods used to generate single-chain magnets

“…Subsequently Ishida and co-workers reported a series of similar compounds using the same [Co II (hfac) 2 ] complex [64,65]. Other simple complexes can also be efficiently used as Ising centres in SCMs: Näther and co-workers as well as Miyasaka, Clérac and co-workers reported several SCMs made from Co(II) and Fe(II) pyridine complexes [61,[66][67][68], and Liu, Sato, Duan and co-workers reported SCMs made of Co(II) complexes of 4-styrylpyridine and 4,4 -bipyridine [69,70] Source: Reproduced, slightly modified, from Ref. [12] and Ni(II) [71] and subsequently reported a series of SCMs prepared from [Fe II (DMF) 6 ] 2+ and analogues of it ( Fig.…”

Magnetization-based assessment of correlation energy in canted single-chain magnets

“…For ferromagnetic systems, this scenario is well confirmed 9,14,15 and has been exploited for a number of compounds 16,17 , but for antiferromagnetic chains with non-collinear anisotropy axes 11,18 the situation is much less clear. The problem was revealed 11 for the compound of formula [Mn(TPP)O 2 PHPh]·H 2 O considered a textbook example of SCM (TPP = mesotetraphenylporphyrin and PHPh = phenylphosphinate) and referred to as Mn-CAF (canted antiferromagnet).…”