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The branched complexes of Schiff bases with various iron(III) salts, named G2-[L2Fe]+A− (A− is NO3−, Cl−, PF6−), were synthesized using the condensation reaction between carbazole derivatives of salicylic aldehyde and N'-ethylethylenediamine and characterized by various spectroscopic methods (GPC, IR, 1H NMR, UV/Vis). The studies revealed that the coordination of the two ligand molecules to metal occurs through the nitrogen ions and oxygen atom of azomethine to form a homoleptic system. All the synthesized coordination compounds were examined for their thermal, optical, and magnetic features. Static magnetic measurements showed that only G2-[L2Fe]Cl was in a single-phase HS state, whereas the Fe(III) ions of G2-[L2Fe]NO3 and G2-[L2Fe]PF6 at room temperatures were in mixed low-spin (LS, S = 1/2) and high-spin (HS, S = 5/2) states: 58.9% LS/41.1% HS for G2-[L2Fe]NO3, 56.1% LS and 43.9% HS for G2-[L2Fe]PF6. All G2-[L2Fe]+A− complexes demonstrate antiferromagnetic exchange interactions between neighboring Fe(III) ions. The ground spin state at 2.0 K revealed a Brillouin contribution from non-interacting LS ions and a proportion of the HS Fe(III) ions not participating in AFM interactions: 57%, 18%, and 16% for G2-[L2Fe]Cl, G2-[L2Fe]NO3 and G2-[L2Fe]PF6, respectively. EPR measurements confirmed the presence of magnetically active HS and LS states of Fe(III) ions and made it possible to distinguish two HS types-with strong low-symmetry (I-type) and weak, distorted octahedral environments (II-type). It was shown that G2-[L2Fe]+A− complexes are magnetically inhomogeneous and consist of two magnetic sub-lattices: AFM-correlated chains in layers from the I-type HS Fe(III) centers and dynamic short-range AFM ordered LS/II-type HS Fe(III) centers in the paramagnetic phase located between the layers. [ABSTRACT FROM AUTHOR]

The main aim of our study is to investigate various types of hybrid systems with a paramagnetic iron (III) ion as a core and photoactive derivatives of carbazole at the periphery. We have synthesized a variety of biligand coordination compounds with the composition [FeL2]A (where L is 2‐[2‐[(E)‐[4‐[4‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)benzoyl]oxy‐2‐phenolate]methyleneamino]ethylamino]ethyl 4‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)benzoate, A− is NO3− (I), Cl− (II), PF6− (III)). These systems were studied by superconducting quantum interference device (SQUID) magnetometry and X‐band electron paramagnetic resonance (EPR) spectroscopy. Magnetic measurements revealed mixed spin states (high spin [HS], low spin [LS]) of Fe (III) ions at room temperatures. Estimates of the corresponding spin contributions were made. It was found that all samples exhibit AFM exchange interactions between iron (III) ions. The ground spin state at 2.0 K was established and analyzed. EPR measurements confirmed the HS states of iron (III) and revealed two types of them: with weak distorted and strong low‐symmetry octahedral crystal fields. [ABSTRACT FROM AUTHOR]

In this paper, the electron and magnetic state of iron placed either on the surface or in the core of TiO2 nanoparticles were investigated using magnetometric methods, electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. It was demonstrated that the EPR spectra of TiO2 samples with iron atoms localized both on the surface and in the core of specific features depending on the composition and size of the nanoparticles. Theoretical calculations using the density functional theory (DFT) method demonstrated that the localization of Fe atoms on the surface is characterized by a considerably larger set of atomic configurations as compared to that in the core of TiO2 nanoparticles. Mössbauer spectra of the samples doped with Fe atoms both on the surface and in the core can be described quite satisfactorily using two and three doublets with different quadrupole splitting, respectively. This probably demonstrates that the Fe atoms on particle surface and in the bulk are in different unlike local surroundings. All iron ions, both on the surface and in the core, were found to be in the Fe3+ high-spin state. [ABSTRACT FROM AUTHOR]

The reaction of [Fe(iii)(CN)6]3− with neutral [Mn(salpn)(H2O)C(CN)3] (salpn: N,N′-propylenebis(salicylideneiminato)) (1) produces two new heterometallic complexes [{MnIII(salpn)(H2O)}2{MnIII(salpn)(H2O)0.7(CH3OH)0.3}2FeII(CN)6]·n(H2O/CH3OH) (2) and [{MnIII(salpn)}4{MnIII(salpn)(H2O)}2FeII(CN)6]{C(CN)3}2·4H2O (3), which are characterized by single-crystal X-ray diffraction. In this reaction, the [C(CN)3]− ligand reduces Fe(iii) to Fe(ii). Complex 3 can be prepared directly using hexacyanoferrate(ii). One more complex containing the hexacyanoferrate(ii), [{MnIII(salpn)(CH3OH)0.67(H2O)0.33}6FeII(CN)6]{ClO4}2·8H2O (4), is obtained in the reaction of [Fe(ii)(CN)6]4− with the cationic complex [Mn2(salpn)2(H2O)2](ClO4)2. The iron(ii) centers in the complexes 2 and 4 are linked via cyano-bridges with the four and six [MnIII(salpn)]+ fragments, respectively. The structure of 3 consists of the cyano-bridged [MnIII6FeII] repeating units linked by double phenolate bridges into a one-dimensional polymeric chain. The magnetic properties of 3 indicate a ferromagnetic coupling between MnIII centers in the double phenolate-bridged [MnIII(salpn)]2 dinuclear subunits. Quantum calculations within the Heisenberg–Van Vleck model are performed giving the exchange constant J = 0.64 cm−1 and the zero-field splitting parameter D = −3.5 ± 0.5 cm−1. The ac-susceptibility obeys the Arrhenius law with the activation energy Ea = 11.89 cm−1. [ABSTRACT FROM AUTHOR]

In this study, crystals of the hybrid layered structure, combined with Fe(III) Spin-Crossover (SCO) complexes with metal-dithiolate anionic radicals, and the precursors with nitrate and iodine counterions, are obtained and characterized. [Fe(III)(3-OMe-Sal2trien)][Ni(dmit)2] (1), [Fe(III)(3-OMe-Sal2trien)]NO3·H2O (2), [Fe(III)(3-OMe-Sal2trien)]I (3) (3-OMe-Sal2trien = hexadentate N4O2 Schiff base is the product of the condensation of triethylenetetramine with 3-methoxysalicylaldehyde; H2dmit = 2-thioxo-1,3-dithiole-4,5-dithiol). Bulk SCO transition was not achieved in the range 2.0–350 K for all three compounds. Alternatively, the hybrid system (1) exhibited irreversible segregation into the spatial fractions of Low-Spin (LS) and High-Spin (HS) phases of the ferric moiety, induced by thermal cycling. Fractioning was studied using both SQUID and EPR methods. Magnetic properties of the LS and HS phases were analyzed in the framework of cooperative interactions with anionic sublattice: Anion radical layers Ni(dmit)2 (1), and H-bonded chains with NO3 and I (2,3). LS phase of (1) exhibited unusual quasi-two-dimensional conductivity related to the Arrhenius mechanism in the anion radical layers, ρ||c = 2 × 105 Ohm·cm and ρ⊥c = 7 × 102 Ohm·cm at 293 K. Ground spin state of the insulating HS phase was distinctive by ferromagnetically coupled spin pairs of HS Fe3+, S = 5/2, and metal-dithiolate radicals, S = 1/2. [ABSTRACT FROM AUTHOR]

Hybrid ion-pair crystals involving hexadentate [Fe(III)(3-OMesal2-trien)]+ spin-crossover (SCO) cationic complexes and anionic gold complexes [Au(dmit)2]− (1) (dmit = 4,5-dithiolato-1,3-dithiole-2-thione) and [Au(dddt)2]− (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were synthesized and studied by single-crystal X-ray diffraction, P-XRD, and SQUID magnetometry. Our study shows that both complexes have similar 1:1 stoichiometry but different symmetry and crystal packing. Complex 1 has a rigid structure in which the SCO cations are engaged in strong π-interplay with molecular surrounding and does not show SCO transition while 2 demonstrates a reversible transition at Tsco = 118 K in a much "softer", hydrogen-bonded structure. A new structural indicator of spin state in [Fe(sal2-trien)]+ complexes based on conformational analysis has been proposed. Aging and thermocycling ruined the SCO transition increasing the residual HS fraction from 14 to 41%. Magnetic response of 1 is explained by the AFM coupled dimers S = 5/2 with J1 = −0.18 cm−1. Residual high-spin fraction of 2, apart from a contribution of the weak dimers with J12 = J34 = −0.29 cm−1, is characterized by a stronger interdimer coupling of J23 = −1.69 cm−1, which is discussed in terms of possible involvement of neutral radicals [Au(dddt)2]. [ABSTRACT FROM AUTHOR]

Correction for ‘Heterometallic complexes combining [MnIII(salpn)]+ and [Fe(CN)6]4− units as the products of reactions between [MnIII(salpn)(H2O)C(CN)3] and [Fe(CN)6]3−/4−’ by Vyacheslav A. Kopotkov et al., New J. Chem., 2014, 38, 4167–4176. [ABSTRACT FROM AUTHOR]

The reaction of [Fe(iii)(CN)6]3− with neutral [Mn(salpn)(H2O)C(CN)3] (salpn: N,N′-propylenebis(salicylideneiminato)) (1) produces two new heterometallic complexes [{MnIII(salpn)(H2O)}2{MnIII(salpn)(H2O)0.7(CH3OH)0.3}2FeII(CN)6]·n(H2O/CH3OH) (2) and [{MnIII(salpn)}4{MnIII(salpn)(H2O)}2FeII(CN)6]{C(CN)3}2·4H2O (3), which are characterized by single-crystal X-ray diffraction. In this reaction, the [C(CN)3]− ligand reduces Fe(iii) to Fe(ii). Complex 3 can be prepared directly using hexacyanoferrate(ii). One more complex containing the hexacyanoferrate(ii), [{MnIII(salpn)(CH3OH)0.67(H2O)0.33}6FeII(CN)6]{ClO4}2·8H2O (4), is obtained in the reaction of [Fe(ii)(CN)6]4− with the cationic complex [Mn2(salpn)2(H2O)2](ClO4)2. The iron(ii) centers in the complexes 2 and 4 are linked via cyano-bridges with the four and six [MnIII(salpn)]+ fragments, respectively. The structure of 3 consists of the cyano-bridged [MnIII6FeII] repeating units linked by double phenolate bridges into a one-dimensional polymeric chain. The magnetic properties of 3 indicate a ferromagnetic coupling between MnIII centers in the double phenolate-bridged [MnIII(salpn)]2 dinuclear subunits. Quantum calculations within the Heisenberg–Van Vleck model are performed giving the exchange constant J = 0.64 cm−1 and the zero-field splitting parameter D = −3.5 ± 0.5 cm−1. The ac-susceptibility obeys the Arrhenius law with the activation energy Ea = 11.89 cm−1. [ABSTRACT FROM AUTHOR]

Correction for ‘Heterometallic complexes combining [MnIII(salpn)]+ and [Fe(CN)6]4− units as the products of reactions between [MnIII(salpn)(H2O)C(CN)3] and [Fe(CN)6]3−/4−’ by Vyacheslav A. Kopotkov et al., New J. Chem., 2014, 38, 4167–4176. [ABSTRACT FROM AUTHOR]