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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Magnetic Properties of Mononuclear Co(II) Complexes with Carborane Ligands Diego R. Alcoba,†,‡ Ofelia B. Oña,¶ Gustavo E. Massaccesi,§ Alicia Torre,∥ Luis Lain,∥ Juan I. Melo,†,‡ Juan E. Peralta,*,⊥ and Josep M. Oliva-Enrich# †

Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria 1428, Buenos Aires, Argentina ‡ Instituto de Física de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Ciudad Universitaria 1428, Buenos Aires, Argentina ¶ Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de la Plata, CCT La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Diag. 113 y 64 (s/n), Sucursal 4, CC 16 1900, La Plata, Argentina § Departamento de Ciencias Exactas, Ciclo Básico Común, Universidad de Buenos Aires, Ciudad Universitaria 1428, Buenos Aires, Argentina ∥ Departamento de Química Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644 E-48080, Bilbao, Spain ⊥ Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, United States # Instituto de Química Física “Rocasolano”, Consejo Superior de Investigaciones Científicas 28006, Madrid, Spain S Supporting Information *

ABSTRACT: We analyze the magnetic properties of three mononuclear Co(II) coordination complexes using quantum chemical complete active space self-consistent field and Nelectron valence perturbation theory approaches. The complexes are characterized by a distorted tetrahedral geometry in which the central ion is doubly chelated by the icosahedral ligands derived from 1,2-(HS)2-1,2-C2B10H10 (complex I), from 1,2-(HS)2-1,2-C2B10H10 and 9,12-(HS)21,2-C2B10H10 (complex II), and from 9,12-(HS)2-1,2-C2B10H10 (complex III), which are two positional isomers of dithiolated 1,2-dicarba-closo-dodecaborane (complex I). Complex I was realized experimentally recently (Tu, D.; Shao, D.; Yan, H.; Lu, C. Chem. Commun. 2016, 52, 14326) and served to validate the computational protocol employed in this work, while the remaining two proposed complexes can be considered positional isomers of I. Our calculations show that these complexes present different axial and rhombic zero-field splitting anisotropy parameters and different values of the most significant components of the g tensor. The predicted axial anisotropy D = −147.2 cm−1 for complex II is twice that observed experimentally for complex I, D = −72.8 cm−1, suggesting that this complex may be of interest for practical applications. We also analyze the temperature dependence of the magnetic susceptibility and molar magnetization for these complexes when subject to an external magnetic field. Overall, our results suggest that o-carboraneincorporated Co(II) complexes are worthwhile candidates for experimental exploration as single-ion molecular magnets.

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INTRODUCTION

by ligands with high spin ground states that exhibit magnetic hysteresis at low temperatures and, consequently, they have been regarded as prototype of single molecule magnets (SMM).3 One of the key properties sought in SMM is the presence of a slow magnetic relaxation (persistence of a magnetic moment for long time below a blocking temperature). The current challenge of this area is to design magnetically active complexes (metallic ions and ligands) with blocking

During the past few decades, efforts dedicated to the study of magnetic properties of molecular systems, aggregates, and crystals have contributed to a significant growth of the molecular magnetism field.1−5 These studies provide valuable insight into the relation between structural and magnetic properties that is useful for applications such as storage devices and quantum computing.6−10 In this context, transition metal ion complexes play a central role among different types of molecules with magnetic properties that can be exploited to that end.11,12 Most of these complexes consist of ions stabilized © XXXX American Chemical Society

Received: March 26, 2018

A

DOI: 10.1021/acs.inorgchem.8b00815 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry temperatures as high as possible to realize them experimentally and make use of their potential properties in practical applications. This challenge remains, as the subtle details of the relation between the electronic environment of the ions and the magnetic properties of the complex remain elusive. In this regard, mononuclear SMM (or single-ion molecular magnets) have been identified as candidates to understand this relation and thus devise complexes with enhanced magnetic properties.13−15 Traditionally, the magnetic behavior of single-ion magnetic complexes has been explained in the framework of an effective spin Hamiltonian containing the zero-field splitting (ZFS) and Zeeman interactions. The ZFS (due to spin−orbit coupling) is typically characterized by the axial (D) and rhombic (E) anisotropy parameters.16,17 The Zeeman interaction originates in the presence of an uniform external magnetic field. A molecule can be considered a single magnet if it possesses a ground state with a high spin quantum number S, a markedly negative magnetic axial anisotropy, and absence of intermolecular interactions which may lead to magnetic relaxation. In these conditions, an energy barrier separates the two minima of potential energy for the degenerate substates corresponding to the quantum numbers MS = ±S. The action of the external magnetic field removes the degeneracy of these substates and, below a blocking temperature, a higher population is accumulated in the lowest state. In the absence of external magnetic field and at higher temperatures, relaxation mechanisms work to restore the equilibrium state. However, if that relaxation process is slow, a magnetic hysteresis is observed if the sweeping rate of the external magnetic field is faster than the relaxation time. Figure 1 shows a scheme of the energy levels involved in this process for the simple case of a S = 3/2 ion.

Figure 2. Molecular structure of three Co(II) complexes in this work. Hydrogen atoms were omitted for clarity.

showing large magnetic anisotropy parameter D, a slow magnetic relaxation at zero field, and a hysteresis loop at 1.8 K. The purpose of this paper is twofold: to perform a computational magnetic and structural characterization of this recently synthesized mononuclear Co(II) complex and to propose and explore two other proposed complexes derived from the ligand positional isomers 1,2-(HS)2-1,2-C2B10H10 and 9,12-(HS)2-1,2-C2B10H10 (Figure 2, complexes II and III) to compare and analyze their properties.

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THEORETICAL BACKGROUND

To characterize the magnetic properties of mononuclear Co(II) complexes, we employ an effective spin Hamiltonian formulated as9 eff ̂ S ̂ + μ BgS ̂ Ĥ = S D B

(1) ̂ where S represents the effective electron spin operator, μB is the Bohr magneton, and B is the externally applied magnetic field. D is the symmetric 3 × 3 second rank ZFS tensor, and g is the Zeeman anisotropy tensor. The states associated with this effective spin Hamiltonian are |S,MS⟩, where S and MS are the standard spin quantum numbers. Using an appropriate molecular coordinate system, this Hamiltonian can be reformulated as9,26 ⎡ 2 S(S + 1) ⎤ 2 2 eff Ĥ = D⎢Sẑ − ⎥ + E(Sx̂ − Sŷ ) + μB BgS ̂ ⎣ ⎦ 3

(2)

where D and E are the axial and rhombic anisotropy parameters described in the Introduction, respectively. In eq 2, S2x̂ , Ŝ2y , and Ŝ2z are the Cartesian components of the Ŝ2 spin operator, and the term μBBgŜ represents the Zeeman interaction. In this framework, the representation of the Hamiltonian Ĥ eff in the |S,MS⟩ basis yields the corresponding matrix, whose eigenvalues and eigenstates allow to evaluate the components of the molar magnetization Mu according to the relation

3

Figure 1. Example of a ZFS system with S = /2.

Carborane-derived complexes constitute icosahedral polyhedrons with interesting magnetic, photophysical, and photochemical properties.18−20 They are air-stable structures with pseudo aromaticity, which can be composed of one isolated unit or several units connected by means of bridging molecules.21−24 Much attention has been paid to the utilization of carboranes in organometallics, medical chemistry, and for luminescence applications. However, there are only a few works attempting to introduce carboranes as ligands in single molecule magnets. Notwithstanding, very recently, carborane units have been described acting as ligands in transition metal complexes presenting magnetic hysteresis.25 That work reports the synthesis of a mononuclear Co(II) complex from CoCl2· 6H2O and 1,2-dithiol-o-carborane (Figure 2, complex I),

kT ∂lnZ u = x, y, z μB ∂Bu

Mu =

(3)

where k is the Boltzmann constant and Z is the partition function corresponding to the eigenstates of the Hamiltonian Ĥ eff at a temperature T, Z=

∑ e−Ei / kT i

(4)

The components of the molar magnetic susceptibility tensor χuv can be calculated from these quantities as B


Article

Inorganic Chemistry χuv =

∂Mu u, v = x , y, z ∂Bv

Table 2. Bond Angles (in Degrees) for Complex I from Experimental (X-ray) Data and DFT Relaxation (See Figure 2)

(5)

Although eq 5 constitutes a formal definition of χuv, the simplest use of this formulation is to calculate the molar magnetic susceptibility tensor χ as9 M χ= B

(6)

which allows us to present field-dependent measurements in terms of χT versus T, providing much insight into the ZFS through visualization of the competing and perturbing effect of the Zeeman interaction.

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COMPUTATIONAL DETAILS

Quantum-chemical computations were carried out on the recently synthesized complex of Co(II) tetracoordinated by two units of 1,2dithiol-o-carborane25 (complex I in Figure 2) as well as its isomers (denoted as II and III in Figure 2). The gas-phase structures of these three complexes were fully relaxed using density functional theory (DFT). To this end, three widely used density functional approximations were employed (B3LYP, 27,28 PBE, 29,30 and BP8627,31,32) in combination with the def2-TZVP basis set and the resolution of the identity approximation with the corresponding auxiliary bases.33,34 DFT-optimized geometries are collected in the Supporting Information. These structures were also confirmed as local minima according to the vibrational analyses. In all cases, we verified that the ground states are high-spin (S = 3/2) quartets. The anisotropy parameters were characterized by complete active space self-consistent field (CASSCF) calculations, using an active space of seven electrons distributed over five 3d orbitals, giving rise to 10 S = 3/2 and 40 S = 1/2 configurations. This active space is sufficient to include all energetically relevant states involved in the spin−orbit coupling. To account for dynamic correlation, N-electron valence perturbation theory (NEVPT2) calculations were performed on top of CASSCFconverged wave functions. The ZFS parameters based on the dominant contributions of the spin−orbit coupling of excited states were calculated by means of the quasi-degenerated perturbation theory (QDPT), which uses the Breit-Pauli approximation35 for the spincoupling operator and the effective Hamiltonians. All calculations were carried out using the ORCA package.36

X-ray

B3LYP

PBE

BP86

2.3554 2.3548 2.3519 2.3548

2.3290 2.3298 2.3282 2.3392

2.2659 2.2661 2.2653 2.2681

PBE

BP86

93.52

93.88

95.04

118.87

113.74

107.04

116.92

S1CoŜ 4 S2 CoŜ 3

114.15

119.77

128.53

117.52

118.88

120.87

125.84

115.76

S2 CoŜ 4 S3CoŜ 4

115.22

117.57

111.43

118.33

95.88

93.54

93.59

95.03

atom pair

complex I

complex II

complex III

Co−S1 Co−S2 Co−S3 Co−S4

2.2659 2.2661 2.2653 2.2681

2.3188 2.3191 2.2919 2.2948

2.3528 2.3516 2.3506 2.3513

Table 4. Bond Angles (in Degrees) for Complexes I, II, and III from DFT (BP86) Relaxation (See Figure 2) bond angle

complex I

complex II

complex III

S1CoŜ 2 S1CoŜ 3

95.04

99.22

102.41

116.92

116.37

114.02

S1CoŜ 4 S2 CoŜ 3

117.52

116.12

112.05

115.76

114.47

112.59

S2 CoŜ 4 S3CoŜ 4

118.33

117.23

113.67

95.03

94.67

102.53

angles for complexes I−III. The two o-carborane-1,2-dithiolate ligands chelate the Co(II) center to form a slightly distorted tetrahedron, in agreement with ref 25, leading to a Co(II) environment that differs from the ideal free-ion tetrahedral (Td) symmetry, causing the 4F Co(II) terms to split. This has been pointed out as the origin of the different D values for tetrahedral Co(II) complexes (see below).38 The D and E/D values calculated at the CASSCF/NEVPT2 level are shown in Table 5. The very small E/D values confirm a highly axial anisotropy in all three complexes. Furthermore,

Table 1. Bond Lengths (in Å) for Complex I from Experimental (X-ray) Data and DFT Relaxation (See Figure 2) 2.2828 2.2771 2.2848 2.2500

B3LYP

95.30

Table 3. Bond Lengths (in Å) for Complexes I, II, and III from DFT (BP86) Relaxation (See Figure 2)

RESULTS AND DISCUSSION For complex I, gas-phase relaxations give Co−S bond lengths that are slightly more uniform than those from X-ray. This can be related to the lack of explicit crystal environment in the calculations. The BP86 functional predicts Co−S distances ranging from 2.2653 to 2.2681 Å for complex I (Figure 2), closer to the experimental X-ray distances than those provided by the PBE and B3LYP functionals (Table 1). The angles

Co−S1 Co−S2 Co−S3 Co−S4

X-ray

S1CoŜ 2 S1CoŜ 3

Therefore, and because one of the purposes of this work is to predict the magnetic parameters of two new complexes for which there are no experimental structural data available, we adopted the structures obtained from the BP86 functional for the calculation of anisotropy parameters for complexes I−III. Tables 3 and 4 summarize the Co−S bond distances and SCoS ̂

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atom pair

bond angle

Table 5. Parameters of the Effective Spin Hamiltonian Ĥ eff (D in cm−1) from CASSCF/NEVPT2 Calculations on Complexes I, II, and III with DFT (BP86) Fully Relaxed Structures

involving the Co(II) ion in the relaxed structures predicted by the BP86 functional, S1CoŜ 2 = 95. 04o and S3CoŜ 4 = 95. 03o, are also closer to those experimentally observed S1CoŜ 2 = 95. 03o and S3CoŜ 4 = 95. 88o (Table 2). These results are in line with the known fact that the BP86 approximation yields reasonably good structural parameters.37

Ĥ eff parameters

C

complex

g1

g2

g3

D

E/D

I II III

2.07 1.47 2.19

2.07 1.49 2.20

2.91 3.52 2.71

−72.85 −147.22 −43.529

0.0016 0.0009 0.0094


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Inorganic Chemistry

anisotropy. In all cases, a S = 3/2 ground state was found before including spin−orbit effects. Once these spin−orbit effects were taken into account in the calculations, a set of Kramers’ doublets (KDs, Δ values in Table 6) is obtained; the CASSCF and CASSCF/NEVPT2 methods also produce similar results, indicating a low-lying KD around 87.1−294.4 cm−1 above the ground state, which may contribute to the spin relaxation processes. The second KD is located at higher energies (635.5− 1661.2 cm−1) and is not expected to participate in the spin relaxation mechanism. The low-lying excited states for complex II (δ = 68.5 cm−1) could lead to an overestimation of the calculated D.40 Therefore, to facilitate a direct comparison with future experiments, in the Supporting Information, we provide a complete list of excitation energies for complexes I−III that can be used to directly compare to temperature-dependent magnetic susceptibility and field-dependent molar magnetization data. We turn now to the analysis of the susceptibility χT and molar magnetization M curves. Calculations on the basis of the 10 S = 3/2 and 40 S = 1/2 spin multiplets at CASSCF/NEVPT2 level, including spin−orbit contribution, yield χT, and M in good agreement with available experimental results25 (Figure 4). A linear behavior of χT can be observed at low temperatures, with saturation at higher temperatures, following

we obtain for complex I values of g1 = 2.07, g2 = 2.07, and g3 = 2.91, corresponding to the main Cartesian components of the g tensor. Although these g values are slightly different to those reported in ref 25. (2.48, 2.48, and 2.75), the calculated and experimental axial symmetry of the g tensor are similar. The small discrepancy can be partially attributed to the effects of the crystal environment, which were not taken into account in our calculations, as is common practice in this type of calculation.39 The main magnetic axes (g1, g2, g3) in Figure 3 are close to the

Figure 3. Ab initio computed main magnetic axes (g1, g2, g3) representing g tensor orientation and main anisotropic axes (Dxx, Dyy, Dzz) representing D tensor orientation for complex I. Hydrogen atoms were omitted for clarity.

main anisotropy axes (Dxx, Dyy, Dzz). In particular, the axes corresponding to g3 and Dzz are almost collinear to the symmetry axis of the complex. More details can be found in the Supporting Information We also analyzed the influence of both static and dynamic electron−electron correlation in the calculated magnetic properties. In Table 6, we show calculated first excitation Table 6. Calculated δ and Δ First Excitation Energies (in cm−1) for Complexes I, II, and III Arising from the CASSCF and CASSCF/NEVPT2 Methods with and without SpinOrbit, Respectivelya method

δ

CASSCF CASSCF/NEVPT2

474.2 1049.0


189.2 68.5


1090.2 1548.0

Δ complex I 219.2/796.0 145.7/1243.0 complex II 260.8/640.1 294.4/635.5 complex III 101.4/1222.9 87.1/1661.2

The Δ value is the energy difference between the ground and the first excited Kramers’ doublet. a

energies (δ and Δ) for complexes I, II, and III arising from the CASSCF and CASSCF/NEVPT2 methods, with and without spin−orbit interaction, respectively. These results show the existence of low-lying spin−orbit free excited states (δ values in Table 6) with energies around 68.5−1548.0 cm−1 above the ground state, which may be the origin of the observed

Figure 4. Experimental (exp.) and ab initio calculated (calc.) (a) temperature-dependent magnetic susceptibility measured at 1000 Oe and (b) field-dependent molar magnetization curve at 2.0 K for complex I. D


Article

Inorganic Chemistry Curie’s law. The χT value at 300.0 K is 2.972 cm3 mol−1K, which is higher than the expected value 1.875 cm3 mol−1K for one isolated Co(II) ion (S = 3/2) center with g = 2, but falls within the range 2.1−3.4 cm3 mol−1K, typical for a single noninteracting high spin d7 Co(II) ion with a considerable orbital angular momentum contribution. The χT value remains roughly constant in the high temperature interval (300−100 K) and then decreases abruptly to 2.361 mol−1K at 2.0 K due to the ZFS of the Co(II) ion. The molar magnetization of the sample at 7 T and 2.0 K is 2.245 μB, far below the expected saturation value for S = 3/2 ion (Msat = 3.88 μB), providing further evidence of a large ZFS.41 Using this same methodology, we also studied the two proposed positional isomers of dithiolated 1,2-dicarba-closododecaborane (II and III shown in Figure 2). The Co−S distances of the relaxed structure for the complex II lie in 2.2919−2.3191 Å and those of the complex III in 2.3506− 2.3528 Å (see Table 3). We observe that complex III presents characteristics similar to those of complex I, both having a unique Co−S distance of 2.35 and 2.26 Å, respectively. Contrarily, complex II presents two distinctive pairs of Co−S distances of 2.32 and 2.29 Å. In relation with the angles, complex II is further distorted from the pure tetrahedral symmetry CoS4, showing bond angles S1CoŜ 2 = 99.22° and S3CoŜ 4 = 94.67°, which are markedly different, in contrast to those found in complexes I and III (see Table 4). Complexes II and III also present a considerable axial anisotropy according to the values E/D ∼ 0, similar to those found for the complex I. Is is worth emphasizing the large value found for the D parameter for complex II (−147.22 cm−1, Table 5), which is about two times larger than that of complex I (−72.85 cm−1). In an attempt to understand the impact of the structural differences of complexes I−III on D, we performed an analysis using the minimum bounding ellipsoid method based on the Khachiyan procedure,42,43 which serves to quantify the deviation from the perfect tetrahedron symmetry (Table 7). According to this analysis, the highest off-center displacement d of the central Co atom corresponds to complex II, followed by complex I, and the lowest corresponds to complex III. This suggests that the largest structural distortion originated by the ligand structure in complex II, as measured by the d parameter, is responsible for the large value of D. The main values for the g

tensor show the distortion in the geometrical parameters. As for complex I, the z-axes of the magnetization g and ZFS tensors are aligned for complexes II and III, but this is not the case for their x and y counterparts. Larger differences are observed for higher values of the anisotropy in the main components of the g tensor (see Figure 5). The main values for the g tensor show the distortion in the geometrical parameters. As for complex I, the z-axes of the magnetization g and ZFS tensors are aligned for complexes II and III, but this is not the case for their x and y

Table 7. Ellipsoidal Analysis of Coordination Polyhedra for the Complexes I, II, and III from DFT (BP86) Structural Optimizationsa R1 R2 R3 ⟨R⟩ σ(R) S d

complex I

complex II

complex III

2.6513 2.0612 2.0323 2.2483 0.2852 0.2085 0.0185

2.6475 2.1680 2.0600 2.2918 0.2553 0.1313 0.0303

2.5502 2.2682 2.2229 2.3471 0.1448 0.0906 0.0059

The principal ellipsoid radii are ordered R1 ≥ R2 ≥ R3. Their mean value ⟨R⟩ is related to the polyhedron size, and the standard deviation σ(R) and the off-center displacement of the central atom d quantify its distortion. S = R3/R2 − R2/R1 describes ellipsoid shape: S < 0, S > 0, and S = 0 correspond to oblate (axially compressed), prolate (axially stretched), and spherical ellipsoids, respectively. All quantities are in Å except S. a

Figure 5. Comparison of the ab initio computed main magnetic axes (g1, g2, g3) representing g tensor orientation and main anisotropic axes (Dxx, Dyy, Dzz) representing D tensor orientation for complexes I, II, and III. Hydrogen atoms were omitted for clarity. E


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Inorganic Chemistry

realized.25 The second complex (II) consists of one ligand arising from 1,2-(HS)2-1,2-C2B10H10 and another one from 9,12-(HS)2-1,2-C2B10H10. The two ligands of the third complex (III) are derived from 9,12-(HS)2-1,2-C2B10H10. Our results for I are in good agreement with experimental observations and serve as a calibration of the computational methodology employed in this work. The three complexes present a similar distorted tetrahedral structure, but their magnetic properties, as described by the effective spin Hamiltonian, turn out to be markedly different. The predicted axial anisotropy D = −147.2 cm−1 for complex II is twice that observed experimentally for complex I, D = −72.8 cm−1, suggesting that this complex may be of interest for practical applications. We believe that the large susceptibility and molar magnetization values found in II compared with those in I and III make this complex an interesting candidate for experimental exploration.

counterparts. Larger differences are observed for higher values of the anisotropy in the main components of the g tensor (see Figure 5). Complexes II and III present χT values of 3.571 and 2.875 cm3 mol−1K at 300.0 K, respectively, larger than those associated with the Co(II) ion (1.875 cm3 mol−1K). Toward lower temperatures, the χT curves for complexes II and III slowly decrease in the interval of temperatures (300−150 K) and (300−50 K), respectively, and then quickly switch to values of 3.024 and 2.087 cm3 mol−1K, respectively, at 2.0 K (Figure 6). The molar magnetization of complexes II and III at 7 T and

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b00815. DFT-optimized structures, calculated g and D tensors, and excitation energies for complexes I−III (PDF)

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AUTHOR INFORMATION

Corresponding Author

Figure 6. Ab initio calculated temperature-dependent magnetic susceptibility for complexes I, II, and III measured at 1000 Oe.

*E-mail: [email protected]. ORCID

Juan E. Peralta: 0000-0003-2849-8472

2.0 K is 2.494 and 2.180 μB, respectively, much lower than the saturated magnetization for the Co(II) ion (3.88 μB), which again indicates the high value of the ZFS. Complex II presents high molar magnetization for a given field and susceptibility values higher than those of complexes I and III (Figures 6 and 7).

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the grants PCB no. 2013-1401PCB, PIP no. 11220130100377CO, and 11220130100311CO (Consejo Nacional de Investigaciones C i e n t ı ́fi c a s y T é c n i c a s , A r g e n t i n a ) , U B A C Y T 20020150100157BA (Universidad de Buenos Aires, Argentina), PICT no. 201-0381 (Agencia Nacional de Promoción Cientı ́fica y Tecnológica, Argentina), and EHU16/10 (Universidad del Paı ́s Vasco). J.E.P. acknowledges support from the Office of Basic Energy Sciences, US Department of Energy, DE-SC0005027. J.M.O. thanks the financial support of Salvador de Madariaga Program no. PRX17/00488 (Ministerio de Educacion, Cultura y Deporte, Spain).

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CONCLUDING REMARKS We performed a computational characterization of the magnetic and structural properties of three doubly chelated Co(II) complexes with icosahedral carborane ligands. The first of them (complex I) is constituted by two ligands derived from 1,2-(HS)2-1,2-C2B10H10 and was recently experimentally

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REFERENCES

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Figure 7. Ab initio calculated field-dependent molar magnetization curve at 2.0 K for complexes I, II, and III. F


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Inorganic Chemistry

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