Correction: 57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato).

Correction for '57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato)' by Ryosuke Taniai et al., Dalton Trans., 2023, 52, 8368-8375.

Investigation of the unique magnetic behaviours of isomers in a 1,2-dithiooxalato-bridged diiron(II) complex.

1,2-Dithiooxalate (dto) can be employed as a bridging ligand and it exhibits symmetric (O,S-chelation) or asymmetric (O,O- and S,S-chelation) coordination forms. In this study, we prepared a novel dto-bridged diiron(II) complex, [{Fe(TPA)}2(µ-dto)](ClO4)2 (1), where TPA is tris(2-pyridylmethyl)amine. Interestingly, the bridging dto ligand exhibited not only the asymmetric form but also a linkage isomer and a diastereomer within the same crystal. Notably, the three isomers of 1 exhibited different magnetic properties, resulting in a multi-step spin crossover behaviour.

57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato).

A mixed-valence iron(II,III) coordination polymer, (Ph4P)[FeIIFeIII(dto)3] (2; Ph4P = tetraphenylphosphonium, dto = 1,2-dithiooxalato), exhibits a thermal hysteresis loop and a low temperature shift of the ferromagnetic phase transition temperature, with increasing pressure. The latter magnetic behaviour can also be observed in a novel compound (nPrPh3P)[FeIIFeIII(dto)3] (3; nPrPh3P = n-propyltriphenylphosphonium). To understand the structural information under pressure, we performed high-pressure powder X-ray diffraction, and the result suggests that there was no structural phase transition for either compound. Considering the 57Fe Mössbauer spectroscopy studies, both 2 and 3 may have a high transition entropy, and this finding is caused by pressure-induced unique magnetic behaviours.

Hydrogen-bonded cobalt(II)-organic framework: normal and reverse spin-crossover behaviours.

A novel hydrogen-bonded metal-organic framework (H-MOF) [Co(HL)2](DMF)1.2(H2O)2.4 (1·solv), in which L = 2,2':6',2''-terpyridine-5,5"-diyl biscarboxylate, was prepared. An intermolecular single H-bond between carboxy and carboxylate sites was present in this compound. The crystal structure of 1·solv showed a 4-fold interpenetrating H-bonded diamond framework. After the desorption of the crystal solvents, 1·desolv exhibited normal and reverse spin-crossover (SCO) behaviours, providing an asymmetric thermal hysteresis loop.

Spin transition triggered by desorption of crystal solvents for a two-dimensional cobalt(ii) complex with hydrogen bonding.

[Co(5tpybNOH)2](BPh4)2 (1; 5tpybNOH = 5,5''-bis(N-tert-butyl hydroxylamino)-2,2':6',2''-terpyridine) has a two-dimensional (2D) structure through a hydrogen bond between the NOH sites, as revealed by X-ray crystallography. The crystal solvents were desorbed above 300 K as shown by thermal analyses and powder X-ray crystallography. The removal of the crystal solvents allowed irreversible structural changes and a spin transition of the Co centre from S = 1/2 to 3/2.

Strong Antiferromagnetic Interaction in a Gadolinium(III) Complex with Methoxy-TEMPO Radical: A Relation between the Coupling and the Gd-O-N Angle.

A new compound [Gd(hfac)3(MeOTEMPO)(MeOH)] (MeOTEMPO = 4-methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl) was prepared. From the X-ray crystal structure analysis, the Gd-O-N angle is 170.9(3)°. The magnetic study clarified the Gd3+-radical interaction with 2J/kB = -26.6(3) K (in the H = -2JS1·S2 convention), which corresponds to one of the strongest antiferromagnetic couplings in the Gd-nitroxide systems. Wider Gd-O-N angles seem to favor stronger antiferromagnetic couplings.

Ground Triplet Spirobiradical: 2,2',7,7'-Tetra( tert-butyl)-9,9'(10 H,10' H)-spirobiacridine-10,10'-dioxyl.

A new spirobiradical, 2,2',7,7'-tetra( tert-butyl)-9,9'(10 H,10' H)-spirobiacridine-10,10'-dioxyl, was prepared. The crystallographic analysis clarified the D2 d molecular structure, suggesting the degeneracy of SOMOs. The magnetic study revealed that intramolecular ferromagnetic coupling was operative with 2 J/ kB = +23(1) K. To the best of our knowledge, the ferromagnetic coupling parameter is the largest ever reported for a paramagnetic spiro compound.

Structural variations in (CuL)2Ln complexes of a series of lanthanide ions with a salen-type unsymmetrical Schiff base(H2L): Dy and Tb derivatives as potential single-molecule magnets.

A new series of heterometallic trinuclear Cu2Ln complexes [lanthanide ions Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5)] has been synthesized using a Cu(ii)-metalloligand derived from a N2O2 donor unsymmetrical Schiff base, H2L (where H2L = N-α-methylsalicylidene-N'-salicylidene-1,3-propanediamine), and structurally characterized. Among these complexes, [(CuL)2Gd(NO3)3(CH3CN)2] (1), [(CuL)2Tb(NO3)3(CH3CN)2] (2) and [(CuL)2Dy(NO3)3(CH3CN)2] (3) are isomorphic and isostructural. In these complexes two metalloligands coordinate to the central Ln(iii) (Ln = Gd, Tb and Dy respectively) ion in a transoid fashion viaµ2-phenoxido oxygen atoms. The Ln(iii) ions are deca-coordinated with a distorted tetradecahedron geometry. The two terminal Cu(ii) ions of the complexes possess a hexa-coordinated distorted octahedral geometry. In contrast, in complexes [(CuL)2Ho(NO3)3(CH3CN)], (4) and [(CuL)2Er(NO3)3(CH3CN)]·0.5(CH3CN) (5), the two metalloligands coordinated to the Ln(iii) ions in a cisoid fashion. The Ho(iii) ion in 4 is nona-coordinated with a distorted tricapped trigonal prismatic geometry and the Er(iii) ion in 5 is octa-coordinated with a distorted square antiprismatic geometry. The two terminal Cu(ii) ions in complexes 4 and 5 are penta-coordinated with a distorted square-pyramidal geometry. The dc magnetic susceptibilities and field dependent magnetization measurement of complex 1 reveal the occurrence of ferromagnetic interactions between Cu(ii) and Gd(iii) ions as well as intermolecular antiferromagnetic interactions. Both complexes 2 and 3 show ferromagnetic interactions between Cu(ii) and Ln(iii) ions. The ac magnetic susceptibilities of all the complexes were also recorded and it was found that only complexes 2 and 3 exhibit slow relaxation of magnetization reorientation below 10 K at 2000 Oe applied dc field, this being characteristic of single molecule magnets.

Giant Exchange Coupling Evidenced with a Magnetization Jump at 52 T for a Gadolinium-Nitroxide Chelate.

The Gd-radical complex [GdIII(hfac)3(6bpyNO)] (6bpyNO = 2,2'-bipyridin-6-yl tert-butyl nitroxide; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) showed a magnetization jump at 52 T observed in a pulsed-field facility, corresponding to an exchange coupling constant of -17.4 K. Furthermore, hysteretic behavior due to a relatively slow magnetization reversal was recorded around 2 T. From the high-frequency EPR study, the exchange coupling between Gd and radical spins accompanies an anisotropic character, which is responsible for both the broad jump and the slow magnetization reversal.

Circular and Chainlike Copper(II)-Lanthanide(III) Complexes Generated by Assembly Reactions of Racemic and Chiral Copper(II) Cross-Linking Ligand Complexes with LnIII(NO3)3·6H2O (LnIII = GdIII, TbIII, DyIII).

The 1:1 assembly reaction of the racemic form of the cross-linking ligand complex Na[CuIILdpen(1R2R/1S2S)] with LnIII(NO3)3·6H2O gave the centrosymmetric circular (CuIILnIII)2 complex [CuIILdpen(1R2R/1S2S)LnIII(NO3)2]2 (1Ln: Ln = Gd, Tb, Dy), while the reaction of the enantiopure form Na[CuIILdpen(1R2R)] with LnIII(NO3)3·6H2O gave the chiral chainlike (CuIILnIII)1∞ complex [CuIILdpen(1R2R)LnIII(NO3)2(CH3CN)]1∞·CH3CN (2Ln: Ln = Gd, Tb, Dy), where {CuIILdpen(1R2R)}- is (N-((1R,2R)-2-(((E)-3-ethoxy-2-oxybenzylidene)amino)-1,2-diphenylethyl)-2-oxybenzamide)copper(II) and {CuIILdpen(1R2R/1S2S)}- is the racemic mixture of {CuIILdpen(1R2R)}- and {CuIILdpen(1S2S)}-. The copper(II) component functions as a cross-linking ligand complex and bridges two LnIII ions at two phenoxo oxygen atoms and one ethoxy oxygen atom, as well as at an amido oxygen atom. For 1Ln, two binuclear species of [CuIILdpen(1R2R)LnIII(NO3)2] and [CuIILdpen(1S2S)LnIII(NO3)2] with opposite chiralities are linked by two amido oxygen atoms O3 and O3* to form a centrosymmetric circular structure with Gd-Cu = 3.370(1) Å and Gd-Cu* = 5.627(1) Å. For 2Ln, binuclear species with the same chirality are bridged by Gd-O3* = 2.228(5) Å to form a chiral chainlike structure with Gd-Cu = 3.3348(9) Å and Gd-Cu* = 6.2326(9) Å. The bridged angles through the amido group of Gd-O3*═C7* are 133.9(5) and 177.6(4)° for 1Gd and 2Gd, respectively. The magnetic susceptibilities of 1Gd and 2Gd were analyzed by the spin-only Hamiltonian on the basis of the circular tetranuclear (-CuIIGdIII-)2 and linear chainlike (-CuIIGdIII-)1∞ structures, respectively. The CuII-GdIII magnetic interactions through two phenoxo bridges and a three-atom N-C═O bridge, J1 and J2, are both ferromagnetic to be J1 = +4.6 cm-1 and J2 = +1.8 cm-1 for 1Gd and J1 = +4.2 cm-1 and J2 = +0.037 cm-1 for 2Gd. The J2 value of 2Gd is much smaller than that of 1Gd. When the temperature was lowered, 1Ln and 2Ln (Ln = Tb, Dy) showed a decrease in the χMT vs T plot due to crystal field effects on the LnIII ion (Stark splitting) and an increase due to the ferromagnetic CuII-LnIII interaction. The magnetization values of 1Ln and 2Ln (Ln = Tb, Dy) without liquid paraffin are considerably larger than the corresponding values with liquid paraffin, indicating the presence of strong magnetic anisotropy. 1Tb and 1Dy showed frequency dependence of ac magnetic susceptibility under zero external dc magnetic field, showing the behavior of single-molecule magnets (SMMs). 2Tb and 2Dy showed no frequency dependence under a zero external magnetic field but showed a meaningful frequency dependence under an external magnetic field. Their energy barriers, Δ/kB, estimated by the Arrhenius plots are 29.4(6) and 20.6(3) K for 1Tb and 2Tb under dc bias fields of 0 and 1000 Oe, respectively, and those of 1Dy and 2Dy are 13.1(9) K and 16.4(2) K under dc bias fields of 0 and 1000 Oe, respectively.

An iron(II) complex tripodally chelated with 1,1,1-tris(pyridin-2-yl)ethane showing room-temperature spin-crossover behaviour.

The spin-crossover phenomenon is a reversible low- and high-spin transition caused by external stimuli such as heat. In the novel iron(II) complex salt tetraphenylphosphonium tris(thiocyanato-κN)[1,1,1-tris(pyridin-2-yl)ethane-κ3N,N',N'']ferrate(II), (C24H20P)[Fe(NCS)3(C17H15N3)], the Fe-N bond lengths are in the range 2.027 (2)-2.089 (2) Å, indicating that the specimen consists of comparable molar fractions of the low- and high-spin species at 296 K. A magnetic study confirmed that spin-crossover takes place at around 290 K.

Strongest Ferromagnetic Coupling in Designed Gadolinium(III)-Nitroxide Coordination Compounds.

Three novel gadolinium(III)-radical complexes [Gd(III)(hfac)3(H2O)(L)] [Gd-L; L = tert-butyl phenyl nitroxide (phNO) and its derivatives (tert-butyl 3-tolyl nitroxide and tert-butyl 4-tert-butylphenyl nitroxide)] were synthesized, and all compounds showed ferromagnetic coupling, obeying the empirical relation: out-of-plane coordination of the Gd ion from the radical π system favors ferromagnetic coupling. In particular, Gd-phNO has a considerably large torsion angle around Gd-O-N-Csp(2) (69.8(9)° on average) and the largest ferromagnetic coupling parameter (2J/kB = +18.0(4) K) in Gd-nitroxide compounds ever known. The validity of our molecular design was assessed on the basis of the magneto-structure relation analysis with many literature data including various paramagnetic ligating groups.

Synthesis of mixed-valence hexanuclear Mn(II/III) clusters from its Mn(II) precursor: variations of catecholase-like activity and magnetic coupling.

One Mn(II) coordination polymer, [Mn(o-(NO2)C6H4COO)2(pyz)(H2O)]n (1), has been synthesized and oxidized with n-Bu4NMnO4 in non-aqueous media to two mixed-valence hexanuclear Mn(II/III) complexes [MnIII2MnII4O2(pyz)0.61/(MeOH)0.39(o-(NO2)C6H4COO)10·(H2O)·{(CH3)2CO}2]·(CH3)2CO (2) and [MnIII2MnII4O2(pyz)0.28/(MeCN)3.72(o-(NO2)C6H4COO)10·(H2O)] (3) (where pyz = pyrazine). All three complexes were characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, and variable-temperature magnetic measurements. The structural analyses reveal that complex 1 is comprised of linear chains of pyz bridged Mn(II), which are further linked to one another by syn­anti carboxylate bridges, giving rise to a two-dimensional (2D) net. Complexes 2 and 3 feature mixed valence [MnIII2MnII4] units in which each of the six manganese centres reside in an octahedral environment. Apart from the variations in terminal ligands (acetone for 2 and acetonitrile for 3), the complexes are very similar. Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, the catecholase-like activity of the complexes has been studied and it is found that the mixed valent Mn6 complexes (2 and 3) are much more active towards aerial oxidation of catechol compared to the Mn(II) complex (1). Variable-temperature (1.8­300 K) magnetic susceptibility measurements showed the presence of antiferromagnetic coupling in all three complexes. The magnetic data have been fitted with a 2D quadratic model derived by Lines, giving the exchange constant J/kB = −0.0788(5) K for 1. For 2 and 3, antiferromagnetic interactions within the Mn6 cluster have been fitted with models containing three exchange constants: JA/kB = −70 K, JB/kB = −0.5 K, JC/kB = −2.9 K for 2 and JA/kB = −60 K, JB/kB = −0.3 K, JC/kB = −2.8 K for 3.

Strongest exchange coupling in gadolinium(III) and nitroxide coordination compounds.

The largest antiferromagnetic coupling parameter was characterized to be 2J/kB = -15.9(2) K in [Gd(hfac)3(6bpyNO)], where 6bpyNO stands for 2,2'-bipyridin-6-yl tert-butyl nitroxide. This molecule was designed according to the empirical relation: more planar chelate favors stronger antiferromagnetic coupling. The Gd-Orad bond is relatively short owing to the tridentate character.

Preparation and characterization of [Gd(hfac)3(DTBN)(H2O)] (DTBN = di-t-butyl nitroxide). Ferromagnetic Gd(3+)-Gd3+ super-superexchange.

The intramolecular radical-Gd antiferromagnetic coupling (2J1/k(B) = -11.6 K) is notably strong, as expected from our molecular design, and the intermolecular exchange coupling along the Gd-O-H···O-Gd bridges is unexpectedly ferromagnetic with the largest Gd···Gd coupling ever known (2J2/k(B) = +0.12 K).