Enhancing Photostability of Complex Lead Halides through Modification with Antibacterial Drug Octenidine.

The high power-conversion efficiencies of hybrid perovskite solar cells encourage many researchers. However, their limited photostability represents a serious obstacle to the commercialization of this promising technology. Herein, we present an efficient method for improving the intrinsic photostability of a series of commonly used perovskite material formulations such as MAPbI3, FAPbI3, Cs0.12FA0.88PbI3, and Cs0.10MA0.15FA0.75PbI3 through modification with octenidine dihydroiodide (OctI2), which is a widely used antibacterial drug with two substituted pyridyl groups and two cationic centers in its molecular framework. The most impressive stabilizing effects were observed in the case of FAPbI3 and Cs0.12FA0.88PbI3 absorbers that were manifested in significant suppression or even blocking of the undesirable perovskite films' recrystallization and other decomposition pathways upon continuous 110 mW/cm2 light exposure. The achieved material photostability-within 9000 h for the Oct(FA)n-1PbnI3n+1 (n = 40-400) and 20,000 h for Oct(Cs0.12FA0.88)n-1PbnI3n+1 (where n = 40-400) formulations-matches the highest values ever reported for complex lead halides. It is important to note that the stabilizing effect is maintained when OctI2 is used only as a perovskite surface-modifying agent. Using a two-cation perovskite composition as an example, we showed that the performances of the solar cells based on the developed Oct(Cs0.12FA0.88)399Pb400I1201 absorber material are comparable to that of the reference devices based on the unmodified perovskite composition. These findings indicate a great potential of the proposed approach in the design of new highly photostable and efficient light absorbers. We believe that the results of this study will also help to establish important guidelines for the rational material design to improve the operational stability of perovskite solar cells.

Magnetically bistable cobalt-dioxolene complexes with a tetradentate N-donor base.

Synthesis and magnetic characterization of a family of cobalt-dioxolene complexes [(Me2TPA)Co(36-DBCat)] (1), [(Me2TPA)Co(36-DBCat)](PF6) (2) and [(Me2TPA)Co(diox-(OMe)3)](BPh4) (3) (Me2TPA = bis(6-methyl-2-pyridyl)methyl-(2-pyridylmethyl)amine; 36-DBCat = dianion of 3,6-di-tert-butylcatechol; diox-(OMe)3 - 2,5-di-tert-butyl-3,3,4-trimethoxy-6-oxocyclohexa-1,4-dienolate) is reported. The neutral complex 1 is found to form hexa- (CoO2N4, 1a) and pentacoordinated (CoO2N3, 1b) isomers. Variable temperature single crystal X-ray diffraction analysis of 1a and 1b clearly indicates the presence of the high-spin divalent metal ion and the dianionic catecholate form of the dioxolene ligand. Oxidation of 1 by ferrocenium hexafluorophosphate results in the formation of the ionic octahedral complex 2, demonstrating thermally induced valence-tautomeric transition (ls-CoIII-36-DBCat ⇄ hs-CoII-36-DBSQ) in the solid state with T1/2 = 175 K (36-DBSQ = radical-anionic semiquinonate form of the redox-ligand). In contrast, aerial oxidation of 1 is accompanied by changes in the structure of dioxolene resulting in oxocyclohexadienolate ligand and the formation of an ionic complex of high-spin divalent cobalt (3). Compounds 1a, 1b, and 3 are found to demonstrate a field-induced single-ion magnet behavior. The analysis of the electronic structures of 1, 2 and 3 with the aid of DFT and SA-CASSCF/NEVPT2 calculations is also given.

Spin-Crossover and Slow Magnetic Relaxation Behavior in Hexachlororhenate(IV) Salts of Mn(III) Complexes [Mn(5-Hal-sal2323)]2[ReCl6] (Hal = Cl, Br).

The cationic complexes of Mn(III) with the 5-Hal-sal2323 (Hal = Cl, Br) ligands and a paramagnetic doubly charged counterion [ReCl6]2- have been synthesized: [Mn(5-Cl-sal2323)]2[ReCl6] (1) and [Mn(5-Br-sal2323)]2[ReCl6] (2). Their crystal structures and magnetic properties have been studied. These isostructural two-component ionic compounds show a thermally induced spin transition at high temperature associated with the cationic subsystem and a field-induced slow magnetic relaxation of magnetization at cryogenic temperature, associated with the anionic subsystem. The compounds are the first examples of the coexistence of spin crossover and field-induced slow magnetic relaxation in the family of known [MnIII(sal2323)] cationic complexes with various counterions.

Quintet Dinitrenes with Negative Zero-Field Splitting: Effect of Spin-Orbit Coupling on the Sign of Magnetic Anisotropy.

We report on W-band EPR and quantum chemical investigation of novel organic tetraradicals with negative axial zero-field splitting (ZFS) parameter D. These belong to the class of quintet 1,3,5-tribromophenylene-2,4-dinitrenes bearing different substituents in position 6 of the benzene ring (1b, N3; 1c, F; 1d, CN; 1e; Cl; 1f, Br). Analysis of the W-band EPR spectrum of dinitrene 1c reveals its large negative ZFS parameter D = -0.27 cm-1. Quantum chemical calculations show that negative D gradually grows in the row of 1c(F) < 1b(N3) < 1d(CN) < 1e(Cl) < 1f(Br) dinitrenes due to decreasing of the through-space distance between the nitrene units and neighboring bromine atoms. Shorter steric N···Br distance results in the stronger contribution of the spin-orbit coupling (SOC) to the total ZFS. The sign of D depends on the interplay of three factors: (i) the angle θ between the "easy" z-axes of the dipolar spin-spin (DSS) and spin-orbit (DSOC) interaction tensors, (ii) the ratio of DSOC/DSS values, and (iii) the rhombicity parameters ESS/DSS and ESOC/DSOC. The study demonstrates in which cases organic quintet tetraradicals may have negative ZFS owing to the presence of heavy atoms at appropriate sites nearby the nitrene units and, thus, possess the bistability property as single-molecule magnets.

The powder X-band electron paramagnetic resonance spectroscopy of septet pyridyl-2,4,6-trinitrene.

The first X-band EPR spectrum containing only non-overlapping signals of septet pyridyl-2,4,6-trinitrene and triplet pyridylnitrenes is reported. This spectrum was recorded after photolysis of 2,4,6-triazidopyridine in solid argon at 5 K. The zero-field splitting (ZFS) parameters of this trinitrene as well as of intermediate triplet mononitrenes and quintet dinitrenes formed at early stages of the photolysis were determined using the combination of modern computer line-shape spectral simulations and density functional theory (DFT) calculations. It was found that septet pyridyl-2,4,6-trinitrene has the record negative parameter DS = -0.1031 cm-1 among all known to date septet pyridyl-2,4,6-trinitrenes and may be of interest as a model multi-qubit spin system for investigations of quantum computation processing.

Nanoscale Visualization of Photodegradation Dynamics of MAPbI3 Perovskite Films.

Herein, we report the nanoscale visualization of the photochemical degradation dynamics of MAPbI3 (MA = CH3NH3+) using infrared scattering scanning near-field microscopy (IR s-SNOM) combined with a series of complementary analytical techniques such as UV-vis and FTIR-spectroscopy, XRD, and XPS. Light exposure of the MAPbI3 films resulted in a gradual loss of MA+ cations starting from the grain boundaries at the film surface and slowly progressing toward the center of the grains and deeper into the bulk perovskite phase. The binary lead iodide PbI2 was found to be the major perovskite photochemical degradation product under the experimental conditions used. Interestingly, the formation of the PbI2 skin over the perovskite grains resulted in a largely enhanced photoluminescence, which resembles the effects observed for core-shell quantum dots. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved degradation dynamics of perovskite absorbers and revealing the associated material aging pathways.

Magnetic behavior of the novel pentagonal-bipyramidal erbium(III) complex (Et3NH)[Er(H2DAPS)Cl2]: high-frequency EPR study and crystal-field analysis.

We report the synthesis, crystal structure and magnetic properties of the new heptacoordinated mononuclear erbium(III) complex (Et3NH)[Er(H2DAPS)Cl2] (H4DAPS = 2,6-diacetylpyridine bis-(salicylhydrazone)) (1). The coordination polyhedron around the Er(III) ion features a slightly distorted pentagonal bipyramid formed by the pentagonal N3O2 chelate ring of the H2DAPS ligand in the equatorial plane and two apical chloride ligands. Detailed high-frequency/high-field electron paramagnetic resonance (HF-EPR) studies of 1 result in the precise determination of the crystal field (CF) splitting energies (0, 290 and 460 GHz) and effective g-values of the three lowest Kramers doublets (KDs) of the Er(III) ion. The obtained HF-EPR data are in good agreement with the results from CF analysis for the Er(III) ion based on the simulation of the dc magnetic data of 1. The results from dynamic susceptibility measurements indicate that there is no slow relaxation of magnetisation behaviour. This observation is discussed in terms of the electronic structure of 1 obtained from experimental and theoretical results.

A Series of Novel Pentagonal-Bipyramidal Erbium(III) Complexes with Acyclic Chelating N3O2 Schiff-Base Ligands: Synthesis, Structure, and Magnetism.

A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N3O2] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H2DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H4DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C2H5OH)Cl] (1); [Er(DAPMBH)(H2O)Cl]·2C2H5OH (2); [Er(DAPMBH)(CH3OH)Cl] (3); [Er(DAPMBH)(CH3OH)(N3)] (4); [(Et3H)N]+[Er(H2DAPS)Cl2]- (5); and [(Et3H)N]+[Y0.95Er0.05(H2DAPS)Cl2]- (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1-6 were studied. The AC magnetic measurements revealed that most of Compounds 1-6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, Ueff ≈ 16-28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1-6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.

Abrupt Spin-State Switching in Mn(III) Complexes with BPh4 Anion: Effect of Halide Substituents on Crystal Structure and Magnetic Properties.

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl)ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh4 (3). Their crystal structure, dielectric constant (ϵ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to sharp spin crossovers from the HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 87 K, while complex 3 exhibits only one spin transition from the HS to the HS:LS intermediate phase at 83 K.

Generation and direct EPR spectroscopic observation of triplet arylphosphinidenes: stabilisation versus internal rearrangements.

Triplet phosphinidenes, which have been postulated as important intermediates in numerous organophosphorus reactions, have been previously directly observed only in isolated cases. Recently we have published the first recorded EPR spectrum of triplet phosphinidene-mesitylphosphinidene (A. V. Akimov et al., Angew. Chem., Int. Ed., 2017, 56, 7944). In the present study we considered a series of triplet arylphosphinidenes which have been stabilised and detected for the first time using EPR spectroscopy by photolysis of 1-arylphosphiranes ArPC2H4 (Ar = C6H5, 9-anthracenyl, and 2,4,6-iPr3C6H2) in solid methylcyclohexane. We paid special attention to their magnetic parameters and the conditions of their stabilization during the photolytic cleavage of arylphosphiranes. An unusual influence of o-substituents on the spin-orbit component of the ZFS parameters D is observed. Surprisingly, photolysis of bulky arylphosphirane Mes*PC2H4 (Mes* = 2,4,6-ButC6H2) results in no formation of the stabilized triplet phosphinidene under similar experimental conditions. The performed quantum chemical calculations showed that the highly unstable singlet phosphinidene Mes*P undergoes an almost barrier-free rearrangement affording a stable insertion product, thereby hindering the conversion of the singlet intermediate to a more stable triplet phosphinidene.

Field-induced SIM behaviour of a Co(II) complex with a 1,1'-diacetylferrocene-derived ligand.

Herein, we report the synthesis and magnetic properties of the Co(ii) coordination compound with the 1,1'-bis(1-((pyrid-2-ylmethylene)hydrazono)ethyl)ferrocene (L) ligand, having the general formula [CoLCl2]. The static magnetic data analysis supported by the CASSCF/NEVPT2 calculations revealed the presence of the triaxial magnetic anisotropy with Dexp = +35.2 cm-1 and large rhombicity (E/D = 0.31) in this complex (Dcalc = +34.5 cm-1, E/Dcalc = 0.30). The dynamic magnetic data confirm that the complex shows a slow field-induced (HDC = 1000 Oe) magnetic relaxation behaviour.

Complexes of Cobalt(II) Iodide with Pyridine and Redox Active 1,2-Bis(arylimino)acenaphthene: Synthesis, Structure, Electrochemical, and Single Ion Magnet Properties.

Complexes [(dpp-BIAN)0CoIII2]·MeCN (I) and [(Py)2CoI2] (II) were synthesized by the reaction between cobalt(II) iodide and 1,2-bis(2,6-diisopropylphenylimino)acenaphthene (dpp-BIAN) or pyridine (Py), respectively. The molecular structures of the complexes were determined by X-ray diffraction. The Co(II) ions in both compounds are in a distorted tetrahedral environment (CoN2I2). The electrochemical behavior of complex I was studied by cyclic voltammetry. Magnetochemical measurements revealed that when an external magnetic field is applied, both compounds exhibit the properties of field-induced single ion magnets.

Purely Spectroscopic Determination of the Spin Hamiltonian Parameters in High-Spin Six-Coordinated Cobalt(II) Complexes with Large Zero-Field Splitting.

Accurate determination of the spin Hamiltonian parameters in transition-metal complexes with large zero-field splitting (ZFS) is an actual challenge in studying magnetic and spectroscopic properties of high-spin transition metal complexes. Recent critical papers have convincingly shown that previous determinations of these parameters, based only on the magnetic data, have low accuracy and reliability. A combination of X-band electron paramagnetic resonance (EPR) spectroscopy and SQUID magnetometry seems to be a more convincing and accurate approach. However, even in this case, the accuracy of the determination of the spin Hamiltonian parameters is strongly limited. In this work, we propose a purely spectroscopic approach, in which three complementary EPR spectroscopic techniques are used to unambiguously with high accuracy determine the spin Hamiltonian parameters for transition-metal complexes with S = 3/2. The applicability of this approach is demonstrated by analyzing the new quasi-octahedral high-spin Co(II) complex [Co(hfac)2(bpy)] (I). Along with the conventional X-band EPR spectroscopy, we also use such advanced techniques as multi-high-frequency EPR spectroscopy (MHF-EPR) and frequency-domain Fourier-transform THz-EPR (FD-FT THz-EPR). We demonstrate that the experimental data derived from the X-band and MHF-EPR EPR spectra allow determination of the g tensor (gx = 2.388, gy = 2.417, gz = 2.221) and the ZFS rhombicity parameter E/D = 0.158. The axial ZFS parameter D = 37.1 cm-1 is measured for I with the aid of FD-FT THZ-EPR spectroscopy, which is able to detect the high-energy EPR transition between the two Kramers doublets. CASSCF/NEVPT2 quantum-chemical calculations of magnetic parameters and magnetic direct current (dc) measurements are performed as well as testing options, and the results obtained in these ways are in good agreement with those derived using the proposed spectroscopic approach.

The First Conducting Spin-Crossover Compound Combining a MnIII Cation Complex with Electroactive TCNQ Demonstrating an Abrupt Spin Transition with a Hysteresis of 50†K.

We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin-crossover salt [Mn(5-Cl-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (I), where 5-Cl-sal-N-1,5,8,12=N,N'-bis(3-(2-oxy-5-chlorobenzylideneamino)propyl)-ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The MnIII complex with a Schiff-base ligand, [Mn(5-Cl-sal-N-1,5,8,12)]+ , acts as the magnetic unit, and the π-electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ- ) is the conducting unit. The title compound (I) exhibits semiconducting behavior with room temperature conductivity σRT ≈1×10-4  ohm-1 cm-1 and activation energy Δ ≈0.20 eV. In the temperature range 73-123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low-spin S=1 and high-spin S=2 states of MnIII and changes in bond lengths within the MnN4 O2 octahedra. The pronounced shrinkage of the basal Mn-N bonds in I at the spin crossover suggests that the d x 2 - y 2 orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5-Br-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (II) of the title compound evidences no spin-crossover phenomena and remains in the high-spin state in the temperature range 2-300 K. Comparison of the chloro and bromo compounds allows the thermal and spin-crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I. The relatively close packing arrangement of the [Mn(5-Br-sal-N-1,5,8,12)]+ cations probably precludes their spin transformation.

Field-induced single-ion magnet behaviour of a hexacoordinated Co(ii) complex with easy-axis-type magnetic anisotropy.

A coordination compound with the composition [CoLCl2]·H2O (L = bis-condensation product of diacetyl and 2-hydrazinyl-4,6-dimethylpyrimidine) was synthesized, in which the Co(ii) ion was hexacoordinated. Under applied DC fields, this compound exhibited single-ion magnet behavior. Two relaxation processes were observed when increasing the applied magnetic field from 1000 to 3200 Oe. The first relaxation (high-frequency) was observed both at 1000 Oe and 3200 Oe, while the second relaxation was only registered under a field of 3200 Oe at low frequencies (<1 Hz) and low temperatures (<5 K). Modeling of the magnetic DC properties using the Griffith Hamiltonian accompanied by quantum chemical calculations revealed easy-axis-type magnetic anisotropy with weak rhombic contributions.

EPR spectroscopy of multicomponent, multispin molecular system obtained by the photolysis of 2,4,6-triazido-3-cyano-5-fluoropyridine in solid argon.

Complex multicomponent, multispin molecular system, consisting of a septet trinitrene, two quintet dinitrenes, and three triplet mononitrenes, was obtained by the photolysis of 2,4,6-triazido-3-cyano-5-fluoropyridine in solid argon. To identify these paramagnetic products, electron paramagnetic resonance spectroscopy in combination with line-shape spectral simulations and density functional theory calculations was used. The products of the photolysis was found to be triplet 2,4-diazido-3-cyano-5-fluoropyridyl-6-nitrene (DT  = 1.000 cm-1 , ET  = 0), triplet 2,4-diazido-3-cyano-5-fluoropyridyl-2-nitrene (DT  = 1.043 cm-1 , ET  = 0), triplet 2,6-diazido-3-cyano-5-fluoropyridyl-4-nitrene (DT  = 1.128 cm-1 , ET  = 0 cm-1 ), quintet 4-azido-3-cyano-5-fluoropyridyl-2,6-dinitrene (DQ  = 0.211 cm-1 , EQ  = 0.0532 cm-1 ), quintet 2-azido-3-cyano-5-fluoropyridyl-4,6-dinitrene (DQ  = 0.208 cm-1 , EQ  = 0.0386 cm-1 ), and septet 3-cyano-5-fluoropyridyl-2,4,6-trinitrene (DS  = -0.1017 cm-1 , ES  = -0.0042 cm-1 ) in a 38:4:7:22:14:4 ratio, respectively.

Steric Heavy Atom Effect on Magnetic Anisotropy of Triplet Tribromophenyl Nitrenes.

Previously unknown the steric heavy atom effect on magnetic anisotropy parameters of triplet phenyl nitrenes is reported. The heavy bromine atom effect is revealed by W-band EPR and theoretical investigations of triplet 2,4,6-tribromophenyl nitrenes bearing different substituents in positions 3 and 5 of the phenyl ring (1a, H/H; 1b, CN/CN; 1c, N3/F; 1d, N3/N3; 1e, Cl/Cl; 1f, Br/Br). The zero-field splitting parameters of nitrenes 1a ( D = 0.9930 cm-1, E = 0.0261 cm-1), 1c ( D = 1.244 cm-1, E = 0.030 cm-1), and 1d ( D = 1.369 cm-1, E = 0.093 cm-1), generated by the photolysis of the corresponding azides in frozen methylcyclohexane solution at 5 K, were determined from the W-band EPR spectra. To clarify the origin of considerable differences in the experimental D values of nitrenes 1a, 1c, and 1d, extensive DFT and CASSCF calculations of these nitrenes as well as of model nitrenes 1b, 1e, and 1f were performed. The calculations show that all nitrenes have nearly the same magnitudes of the spin-spin interactions ( DSS ∼ 1 cm-1), but drastically differ in the spin-orbit coupling parameter (from DSOC = 0.087 cm-1 for 1a to DSOC = 0.765 cm-1 for 1f). Comprehensive analysis of various computational data showed that the magnitude of DSOC of nitrenes 1a-f is the function of the N···Br distance between the nitrene nitrogen and the neighboring bromine atoms. The more bulky substituents are located in positions 3 and 5 of nitrenes 1a-1f, the smaller the N--Br distance and the larger DSOC. These features indicate that the heavy atom effect on magnetic anisotropy of triplet phenyl nitrenes originates from the through-space rather than through-bond electronic interactions between the bromine atoms and the nitrene unit.

Evidence of field induced slow magnetic relaxation in cis-[Co(hfac)2(H2O)2] exhibiting tri-axial anisotropy with a negative axial component.

We report a combined experimental characterization and theoretical modeling of the hexa-coordinated high-spin Co(ii) complex cis-[Co(hfac)2(H2O)2] (I). The magnetic static field (DC) data and EPR spectra (measurements were carried out on the powder samples of diluted samples cis-[Co0.02Zn0.98 (hfac)2(H2O)2]) were analyzed with the aid of the parametric Griffith Hamiltonian for the high-spin Co(ii) supported by the ab initio calculations of the crystal field (CF) parameters, g-factors and superexchange parameters between H-bonded Co(ii) ions in the neighboring molecules in a 1D network. This analysis suggests the presence of the easy axis of magnetic anisotropy and also shows the existence of a significant rhombic component. The detected frequency dependent (AC) susceptibility signal shows that complex I exhibits slow paramagnetic relaxation in the applied DC field belonging thus to the class of non-uniaxial field induced single ion magnets with a negative axial component of anisotropy. It is demonstrated that the main contributions to the relaxation come from the direct one-phonon process dominating at low temperatures, while the contribution of the two-phonon Raman process becomes important with increasing temperature.

The EPR Spectrum of Triplet Mesitylphosphinidene: Reassignment and New Assignment.

Low-temperature UV-photolysis of mesitylphosphiranes under highly anaerobic conditions leads to the formation of the triplet mesitylphosphinidene (MesP). The recorded X-band EPR spectrum of triplet MesP and the derived zero-field splitting parameter D=4.116 cm-1 differ significantly from those reported previously for this intermediate. New magnetic parameters of mesitylphosphinidene are discussed along with the results of DFT calculations.

Single-Ion Magnet Et4N[CoII(hfac)3] with Nonuniaxial Anisotropy: Synthesis, Experimental Characterization, and Theoretical Modeling.

In this article we report the synthesis and structure of the new Co(II) complex Et4N[CoII(hfac)3] (I) (hfac = hexafluoroacetylacetonate) exhibiting single-ion magnet (SIM) behavior. The performed analysis of the magnetic characteristics based on the complementary experimental techniques such as static and dynamic magnetic measurements, electron paramagnetic resonance spectroscopy in conjunction with the theoretical modeling (parametric Hamiltonian and ab initio calculations) demonstrates that the SIM properties of I arise from the nonuniaxial magnetic anisotropy with strong positive axial and significant rhombic contributions.