Synthesis, crystal structure and magnetic properties of a trinuclear phenolate bridged manganese complex containing Mn(II)–Mn(III) ions

Abstract

A trinuclear manganese complex containing Mn(III)–Mn(II)–Mn(III) cores, [Mn₃(bp)₄(CH₃OH)]·0.875CH₃OH·0.125H₂O (1), has been prepared and structurally characterized where H₂bp is an O₃-donor bis(phenolate) ligand {H₂bp = 2,2′-sulfinylbis(4-methylphenol)}. The combined structural and magnetic analysis reveals the mixed valence character of the compound with one central Mn(II) ion and two outer Mn(III) ions connected by phenolate bridging groups. The Mn(III)–Mn(II)–Mn(III) angle is close to a linear arrangement (∼160°) and the Mn(II)⋯Mn(III) separations are about 3.21 Å. The coordination environment around the two terminal Mn(III) ions is distorted octahedral (O₆) and shows Jahn–Teller elongation, while the central Mn(II) has a distorted five coordinated trigonal-bypyramidal (O₅) coordination environment. In the central Mn(II) the equatorial Mn–O bond lengths are shorter than the axial Mn–O ones. The crystal packing of 1 involves hydrogen bonding between the complex and the uncoordinated methanol molecule. The analysis of the magnetic susceptibility data is consistent with ferromagnetic intramolecular coupling among the Mn(III) and the Mn(II) ions. The system can be interpreted in terms of a simple Heisenberg–Dirac–Van Vleck model H = −J(S₁S₂ + S₂S₃) with a magnetic coupling constant of J = 0.28 cm⁻¹.

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Introduction

In the past decade polynuclear transition metal complexes have attracted considerable attention.¹ Among them, polynuclear manganese complexes are of great and current interest because of their relevance in industrial catalysis,² the mimicry of active centers of biological systems,³ their use as models for the water oxidation center of photosystem II⁴ and also their remarkable magnetic properties⁵ which may help us to improve our understanding of the mechanism of magnetic coupling and for the design of single-molecule magnets (SMM).⁶ It is well recognized that some manganese complexes possess large numbers of unpaired electrons and show paramagnetism in various oxidation states. Therefore, polynuclear manganese complexes are one of the most important precursors for magnetic materials^7,8 and these findings have triggered the investigation of new molecular complexes based on manganese ions.

The most popular and effective strategy to design magnetically coupled polynuclear complexes consist of connecting paramagnetic centers by short bridging ligands such as oxide, hydroxide, alkoxide, carboxylate or phenolate, in combination with different organic co-ligands.^9–12 Trinuclear manganese systems may exhibit triangular,¹³ discrete linear¹⁴ and extended polymeric structures.¹⁵ Trinuclear phenolate-bridged manganese complexes are one of the most important class of Mn complexes because they can show interesting magnetic properties. Within the 15 phenolate bridged manganese trimers available in the CCDC database, only two complexes containing both Mn²⁺ and Mn³⁺ cores have been reported,¹⁶ while the remaining 13 structures are Mn²⁺ (ref. 17) or Mn³⁺ (ref. 18) complexes. On the other hand, the phenol containing ligands are one of the most important O-donor systems in the bioinorganic chemical community¹⁹ because of the widespread occurrence of the tyrosyl radicals in various metalloproteins,²⁰ which are involved in oxygen dependent enzymatic oxidations. Ligands containing two phenolate donor atoms have good σ and π-donor ability and can stabilize higher oxidation states with highly covalent M–O phenolate bonds.²¹ Moreover, they may produce phenoxy radical complexes to be used as bio-inspired radical catalysts for the conversion of different organic substrates.²² Tridentate bis(phenol) ligands embrace three donor atoms (such as OXO where X = Se, S, S=O, etc.) have versatile structures and generate novel transition metal complexes with interesting magnetic, catalytic and electron transfer activity.²³

The symmetric two phenolate containing sulfoxides have been synthesized by many groups using various methods. Treatment of phenols carrying two substitution on ortho and para positions with thionyl chloride in the presence of Lewis acids afford bis(phenolate) sulfoxide ligands. Phenols with one substitute on the para position, form tetra member convoluted rings.²⁴ Eight tetranuclear manganese complexes have been reported by these type of ligands.^25–27 However, by controlling the reaction condition and using suitable molar ratio of reagents, the bis(phenolate) sulfoxide can be produced with para-substituted phenols (Scheme 1).²⁸ In this sense, we find interesting the preparation of mixed valence Mn(II)–Mn(III) polynuclear benzoate bridged complexes. Herein, we report synthesis, spectroscopic and magnetic properties of a new trinuclear manganese complex of bis(phenolate) ligand contaning Mn(II)–Mn(III) cores in which the Mn(II) ion has trigonal-bipyramide coordination environment.

Scheme 1 Schematic drawing of the synthesis of H₂bp and complex 1.

Results and discussion

Syntheses of compounds and spectroscopy

The 2,2′-sulfinylbis(4-methylphenol), H₂bp, was synthesized by the reaction of thionyl chloride with p-cresol in dry dichloromethane in the presence of AlCl₃. Recrystallization of the crude product gave the desired symmetric pincer-type tridentate O,O,O-donor ligand in excellent purity. The manganese complex of bis(phenolate) ligand was prepared in reaction of H₂bp with an equimolar amount of MnCl₂·4H₂O in methanol (Scheme 1). In the reaction two Mn(II) ions were oxidized to Mn(III) and H₂bp acts as a dinegative ligand.

¹H and ¹³C NMR spectra of the ligand (Fig. S1 and S2†) in CDCl₃ confirmed the proposed structure for H₂bp. The signal at δ 2.26 ppm in the ¹H NMR spectrum of H₂bp is assigned to the –CH₃ group of p-cresol. The broad peak at 8.65 ppm is assigned to the phenolate –OH. One singlet and two doublet peaks between 6.82–7.15 ppm are assigned to the three aromatic hydrogen atoms on the phenyl groups. The electronic spectra of complex and bis(phenolate) ligand are shown in Fig. 1. They show similar absorption peaks. Comparison of the complex and ligand spectra supports the coordination of H₂bp to the manganese centers. The spectrum of the complex shows an intense band in the high-energy region at 230 nm which can be attributed to the intraligand π → π* transition. The band at 300 nm is assigned to the intraligand and ligand to metal charge transfer (LMCT) transitions. A very broad band around 400 nm is due to the LMCT transition.

Fig. 1 UV-Vis spectra of (a) H₂bp and (b) complex 1 in MeOH.

Differential thermal (DT) and thermal gravimetric analyses (TGA) were conducted to examine the thermal stability of complex 1. TGA thermogram of the compound exhibits four steps weight losses (Fig. S3†). The first step started at 35 °C and was completed at about 195 °C, corresponding to the loss of the uncoordinated methanol and water molecule. The observed weight loss of 2.56% is equal to the calculated value (2.39%). The remaining organic ligand and coordinated methanol are removed continuously to yield the total mass loss of 56.29% up to 1400 °C, probably leaving MnO₂.

Description of the crystal structure

In the asymmetric unit of complex 1, two crystallographically independent complex molecules appear. An overlay of these two molecules shows that they are almost identical (Fig. S4†). For this reason only one molecule from asymmetric part of the unit cell will be discussed. The molecular structure with the atom numbering scheme is shown in Fig. 2 and selected interatomic distances and angles are summarized in Tables 1 and 2, respectively. Compound 1 is trinuclear complex of manganese in which two external Mn³⁺ cores are connected to the central Mn²⁺. Four dianions of the bis(phenolate) ligand with one methanol molecule are involved in the coordination environment of the three Mn³⁺/Mn²⁺ ions. Each bis(phenolate) anion behaves as a dianionic tridentate ligand (bp)²⁻, supplying three oxygen atoms through the S=O moiety and phenolates-O for the coordination to the metal ions. The angle of Mn1–Mn2–Mn3 is 156.4(3)°. The geometry around the two terminal Mn³⁺ centers is a distorted octahedral with a O₆-ligand set provided by two tridentate bis(phenolate) ligands in a facial coordination mode. For each terminal Mn³⁺ atom, two bonds are considerably elongated (Mn1–O1, 2.120(5); Mn1–O2C, 2.164(5); Mn3–O2E, 2.195(6) and Mn3–O4, 2.111(6) Å) with respect to the other four bonds (average 1.934 Å and 1.922 Å) in consistent with the Jahn-Teller effect which is usually found in most of the octahedral Mn³⁺ complexes with d⁴ electronic configuration.²⁹ For each terminal Mn³⁺ ions the two coordinated (bp)²⁻ ligands are in a cis orientation with respect to the sulfoxide oxygen atom donors (S=O). Two phenolate donor atoms provided by two bis(phenolate) ligands are located in a trans mode towards each other and act as a terminal monodentate donor. The remaining phenolate arms are in a cis position. These phenolate oxygen atoms further bridges to the central Mn²⁺ atom of the trimeric moiety.

Fig. 2 The molecular structure of one of two independent molecules of 1 drawn at 10% probability.

Table 1 Selected bond lengths (Å) and angels (°) for complex 1

Bond	(Å)	Angle	(°)
Mn1–O2D	1.859(6)	Mn2–O2C–Mn1	98.3(2)
Mn1–O2B	1.891(6)	Mn2–O2A–Mn1	101.5(2)
Mn1–O2A	1.993(6)	Mn2–O2G–Mn3	101.4(2)
Mn1–O2	1.993(6)	Mn2–O2E–Mn3	98.0(2)
Mn1–O1	2.120(5)	Mn1–Mn2–Mn3	156.40(6)
Mn1–O2C	2.164(5)	O2D–Mn1–O2B	176.2(2)
		O2D–Mn1–O2A	90.6(3)
Mn3–O2H	1.869(6)	O2B–Mn1–O2A	88.6(3)
Mn3–O2F	1.893(6)	O2–Mn1–O1	98.2(2)
Mn3–O3	1.942(7)	O2D–Mn1–O2C	86.4(2)
Mn3–O2G	1.985(6)	O2B–Mn1–O2C	89.8(2)
Mn3–O2E	2.195(6)	O2A–Mn1–O2C	80.3(2)
Mn3–O4	2.111(6)	O2E–Mn2–O2C	113.3(2)
		O2E–Mn2–O1M	125.6(3)
Mn1–Mn2	3.205(2)	O2C–Mn2–O1M	120.8(3)
Mn2–Mn3	3.215(2)	O2E–Mn2–O2A	107.8(2)
		O2C–Mn2–O2A	79.0(2)
Mn2–O2E	2.065(6)	O1M–Mn2–O2A	87.8(2)
Mn2–O2C	2.073(6)	O2E–Mn2–O2G	78.8(2)
Mn2–O1M	2.105(7)	O2C–Mn2–O2G	104.0(2)
Mn2–O2A	2.145(5)	O1M–Mn2–O2G	83.7(2)
Mn2–O2G	2.167(5)	O2A–Mn2–O2G	171.3(2)
		O2H–Mn3–O2F	178.7(3)
		O2H–Mn3–O2G	90.4(3)
		O2F–Mn3–O2G	89.4(3)
		O3–Mn3–O4	97.8(2)
		O2H–Mn3–O2E	95.0(2)
		O2F–Mn3–O2E	83.7(2)
		O2G–Mn3–O2E	79.8(2)

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Table 2 Hydrogen bond geometry (Å, °)^a

D–H⋯A	D–H⋯A	H⋯A	D⋯A	D–H⋯A
a Symmetry codes: (i) x + 1, y, z + 1; (ii) x + 1, y, z; (iii) x − 1, y, z; (iv) x − 1, y, z − 1.
O1M–H1M⋯O3M	0.84	1.93	2.699(11)	152
O2M–H2M⋯O4M	0.84	1.84	2.670(11)	172
C6L–H6L⋯O3^i	0.95	2.70	3.440(12)	135
C6B–H6B⋯O3^ii	0.95	2.63	3.480(10)	150
C6H–H6H⋯O2^iii	0.95	2.55	3.361(10)	144
C7D–H7D2⋯O8	0.98	2.63	3.303(12)	126
C7F–H7F1⋯O5^iv	0.98	2.47	3.432(12)	168

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The most distorted from right angle are the cis O_bridge–Mn–O_bridge angles (O2C–Mn2–O2A, 79.0(2)° and O2E–Mn2–O2G, 78.8(2)°). These angles being compressed by the formation of a four-membered chelate rings with the Mn²⁺ and Mn³⁺ ions (Mn1/O2A/Mn2/O2C and Mn3/O2E/Mn2/O2G). The central metal in complex 1 is five-coordinated in which the ligand environment is provided by the four bridging phenolate oxygen atoms and one coordinated methanol molecule. The central Mn²⁺ atom has slightly distorted trigonal bipyramidal (TBP) coordination geometry. The structural index, τ, has a value of 0.76 [τ = (α − β)/60, where α and β are the two largest coordination angles; τ = 0 for square pyramidal geometry, and τ = 1 for trigonal bipyramidal geometry].³⁰ The equatorial plane of the TBP is defined by two μ₂-bridging phenolate oxygen donors (O2E, O2C) and the oxygen atom of the coordinated methanol molecule (O1M). The axial positions contain two μ₂-bridging phenolate oxygen ligands with O2G–Mn2–O2A angle of 171.3(2)°, near to the ideal value of 180°. In the central Mn²⁺ atom, the Mn–O bond lengths for the equatorial positions (<2.10 Å) are shorter than the corresponding bond lengths for the axial positions (>2.11 Å) and attributable to the different hybridizing which is usually found in TBP geometry (sp³d = sp² + pd) and is in good agreement with the other reported TBP manganese complexes.³¹ The O2E–Mn–O2C angle of the equatorial plane (113.3(2)°) is compressed from the ideal trigonal value of 120, and the two O1_methanol–Mn–O2E/O1_methanol–Mn–O2C angles of this plane are slightly expanded (125.6(3) and 120.8(3)°, respectively). The observed slight distortions in the equatorial plane angles of this stereochemistry are a result of accommodating the formation of the four membered chelate rings (Mn1/O2A/Mn2/O2C and Mn3/O2E/Mn2/O2G) in forming the trimeric moiety. The phenolate oxygen bridging atoms mediate Mn⋯Mn separation of 3.205–3.215 Å and the dihedral angle between Mn1/O2A/Mn2/O2C and Mn3/O2E/Mn2/O2G plane is about 60°. There is a methanol molecule beside each trinuclear molecule which connects to the methanol ligand and phenolate oxygen-O2F by strong hydrogen bonds. Parameters of hydrogen bonding geometry are given in Table 2. There are some CH–π and π–π stacking interactions.

Magnetic properties

Fig. 3 shows the temperature dependence of the χ_MT product for complex 1.

Fig. 3 (a) Temperature dependence of the χ_MT product for complex 1. The solid line corresponds to the best fit to the model derived from eqn (2). (b) Magnetization vs. field isotherm at 2 K. The solid line is a guide for the eyes.

At room temperature the χ_MT value for 1 is very close to the spin-only value (10.3 emu mol⁻¹) expected for two isolated high spin Mn(III) with S = 2 and one high spin Mn(II) ion with S = 5/2. On lowering T, the χ_MT product remains almost constant up to 50 K and then it continuously increases which suggests the occurrence of a dominant ferromagnetic interaction. The total spin for a ferromagnetically coupled Mn(III)–Mn(II)–Mn(III) complex would be S_T = 13/2 with a spin-only value for χ_MT product of 24.4 emu mol⁻¹ K, which is far from being reached at low temperatures. Also, the magnetisation isotherm plot is below the maximum expected for a complex with a S_T = 13/2 (M_S = 13 BM). These two facts indicate that the ferromagnetic coupling is weak and that low-lying excited states with smaller spin are also populated at low temperatures. The magnetic model to analyse this magnetic behaviour is shown in Scheme 2 and its corresponding isotropic spin Heisenberg Hamiltonian is given by^32,33

H = −J₁₂(S₁S₂) − J₂₃(S₂S₃) − J₁₃(S₁S₃) (1)

J_ij are the exchange interactions between the Mn i and j ions and S_i represents the corresponding spin operator. Although complex 1 contains two different trinuclear units with Mn(III) ions which are not equivalent, their environment and their connectivity (bridging atoms and angles) towards the Mn(II) ion are very similar, so we could assume J₁₂ = J₂₃ and due to the long Mn(1)⋯Mn(3) distance the latter term could be neglected leaving eqn (2) as^34,35

H = −J(S₁S₂ + S₂S₃) (2)

Scheme 2 The magnetic model to analyse the magnetic behaviour of complex 1.

The zero-field energy levels for such a system can be easily calculated by Kambe's method,^32,34 however due to the large value of the spin of the Mn(II) and Mn(III) ions (S = 5/2 and S = 2, respectively) the Van Vleck equation is rather complex and with the intention of elude numerical errors the MAGPACK package of programs has been used to analyse the magnetic susceptibility data.^36,37 The model employed considers just a single g parameter to avoid overparameterization and it does not include magnetic anisotropy, since we did not observe a decrease of the experimental χ_MT product at low temperatures for fields as low as 1000 Oe. Best fit parameters to the model are g = 1.93, J = 0.28 cm⁻¹ and R = 9.44 × 10⁻⁵ (R is the agreement factor defined as ). It can be seen that the calculated curve matches very well the experimental plot in the whole temperature range which indicates that the model, with the assumptions done above, is good enough to explain the magnetic behaviour of the compound.

Ferromagnetically coupled mixed valence Mn(II)–Mn(III) complexes may exhibit single-molecule-magnet behaviour (SMM) due to the combination of high spin and a uniaxial zero-field-splitting parameter induced by the occurrence of the Mn(III) ions. Nevertheless ac magnetic measurements did not show a measurable signal in the temperature range studied which discards the SMM behaviour that additionally supports a negligible effect of the anisotropy (Fig. S5†).

Several binuclear, trinuclear and tetranuclear complexes involving magnetic interactions between high spin Mn(II) and Mn(III) ions have been reported. Some of them exhibit ferromagnetic couplings,^33,38,39 others are antiferromagnetic.^33,40–43 In all these complexes the super-exchange interactions have been found to be weak, like in 1, with values which range −7 to +3.94 cm⁻¹.³² A few attempts have been done in order to find some correlations between the magnetic couplings constants and some structural parameters,³³ however the large number of singly occupied orbitals, the geometry of the Mn ions, the occurrence of interactions through different σ and π magnetic exchange pathways and the diversity of bridges involved has made, at least up to now, impossible to find a clear structural parameter, or set of parameters, directly correlated to the magnetic coupling. In any case, the values obtained for 1 are in the range of the previous studies and provide new experimental data which may contribute to establish magneto-structural correlations.

Conclusions

In summery, a new trinuclear manganese complex containing Mn(II)–Mn(III) cores, has been prepared and structurally characterized. The central Mn(II) ion and two outer Mn(III) ions connected by phenolate bridging groups and the Mn(III)–Mn(II)–Mn(III) angle is close to linear arrangement (∼160°). The Mn(II)⋯Mn(III) separation is about 3.21 Å. The central Mn(II) has a distorted five coordinated trigonal-bypyramidal (O₅) coordination environment which the equatorial Mn–O bond lengths are shorter than axial ones. The analysis of the magnetic susceptibility data is consistent with a ferromagnetic intramolecular coupling among the Mn(III) and the Mn(II) ions with a magnetic coupling constant of J = 0.28 cm⁻¹.

Experimental

Materials and instrumentations

Manganese(II) chloride tetrahydrate, MnCl₂·4H₂O, thionyl chloride, AlCl₃ and p-cresol were purchased from Merck and used as received. Solvents of the highest grade commercially available (Merck) were used without further purification. CH₂Cl₂ was dried by the standard procedure. IR spectra were recorded in KBr discs with a Bruker FT-IR spectrophotometer. UV-Vis solution spectra were recorded on a thermo-spectronic Helios Alpha spectrophotometer. Elemental analyses were carried out using a Perkin-Elmer 240 elemental analyzer. ¹H and ¹³C NMR spectra in DMSO-d₆ solution were measured on a Bruker 250 MHz spectrometer and chemical shifts are indicated in ppm relative to tetramethylsilane. Differential thermal (DT) and thermal gravimetric analyses (TGA) curve was recorded with a PL-STA 1500 device manufactured by Thermal Sciences.

Synthesis of 2,2′-sulfinylbis(4-methylphenol) (H₂bp)

2,2′-Sulfinylbis(4-methylphenol) (H₂bp) was synthesized according to the reported procedure.⁴⁴ In a typical method the reaction was carried out in a 50 ml round bottom flask equipped with a magnetic stirrer and immersed in an ice bath. The mixture of 2.16 g (2 mmol) p-cresol and 2 mmol AlCl₃ were added to a 20 ml dry dichloromethane and stirred for 20 min. The solution of thionyl chloride (1 mmol) in 10 ml dry dichloromethane was drop-wise added (1 drop per 10 second) and the mixture was stirred for 20 h. The solution was then poured to 30 ml ice-water. After a day white solids of H₂bp appeared. This solid was separated and filtered off, washed with 5 ml of cool water and recrystallized in ethanol. Yield: 0.17 g, 65%, M.p. 192–194 °C. Anal. calcd for C₁₄H₁₄O₃S (262.32 g mol⁻¹): C 64.10; H 5.38; S 12.22. Found. C 63.90; H 5.15; S 12.45%. FT-IR (KBr): ν = 3440 (m, br), 2924 (m), 2860 (w), 1609 (m), 1589 (m), 1507 (vs), 1456 (s), 1414 (vs), 1384 (vs), 1363 (s), 1288 (vs), 1262 (s), 1227 (s), 1206 (m), 1141 (s), 1061 (m), 999 (w), 945 (vs), 883 (m), 828 (s), 784 (m), 758 (m), 714 (s), 701 (m), 652(w), 567 (m), 529 (s), 492 (m), 486 (w), 470 (w), 442 (m), 417 (m). ¹H NMR (250.13 MHz, CDCl₃, 25 °C, TMS): δ = 2.27 (s, 6H, C–H_methyle), 6.82 (d, 2H, J = 8.50), 7.05 (s, 2H), 7.15 (d, 2H, J = 7.50 Hz), 8.65 (s, broad 2H, –O–H). ¹³C NMR (62.90 MHz, CDCl₃): δ = 156.4, 134.1, 126.1, 124.7, 120.7, 118.8, 20.4 ppm. UV/Vis (CH₃OH): λ_max (ε_max/dm³ mol⁻¹ cm⁻¹) = 208 (43 500), 295 (5700), 317 nm (5300).

Synthesis of [Mn₃(bp)₄(MeOH)]·0.875MeOH·0.125H₂O (1)

Single crystals of [Mn₃(bp)₄(CH₃OH)] 0.875MeOH·0.125H₂O (1) were obtained by a thermal gradient method. In this method 1.0 mmol of MnCl₂·4H₂O and 1.0 mmol of H₂bp were placed in the main arm of a branched tube. Methanol was carefully added to fill the arms, the tube was sealed and the reagents containing arm immersed in an oil bath at 60 °C while the other arm was kept at ambient temperature. After 10 days black crystals were deposited in the cooler arm, which were filtered off and air dried. Yield: 0.19 g, 60%. Anal. calcd for C_57.875H_55.75Mn₃O₁₄S₄ (1268.33 g mol⁻¹): C, 54.80; H, 4.43; S, 10.11. Found. C, 54.94; H, 4.41; S, 10.09. FT-IR (KBr): ν = 3428 (vs, br), 3019 (w), 2919 (m), 1606 (m), 1545 (m), 1479 (vs), 1396 (m), 1302 (vs), 1268 (s), 1212 (m), 1145 (m), 1058 (m), 1022 (m), 943 (s), 896 (s), 818 (s), 800 (s), 727 (w), 684 (w), 632 (m), 527 (s), 467 (s), 448 (s), 419 (m) cm⁻¹. UV/Vis (CH₃OH): λ_max (ε_max/dm³ mol⁻¹ cm⁻¹) = 230 (93 600), 300 (47 700), 400 (broad) nm (7850).

X-ray diffraction data collection and refinement

Data collection for the X-ray structure determination was performed on an Xcalibur PX four-circle diffractometer with an Onyx CCD detector with graphite monochromatized MoKα radiation. Data were collected at 100(2) K using an Oxford Cryosystems cooler. Data collection, cell refinement, data reduction, analysis and absorption corrections were carried out with CrysAlis^Pro software.⁴⁵ The structure was solved by direct methods with SHELXS⁴⁶ and refined by a full-matrix least-squares technique on F² using SHELXL⁴⁶ with anisotropic thermal parameters for the non-H atoms. The H atoms were found in the difference Fourier maps, but in the final refinement cycles they were repositioned in their calculated positions and refined using a riding model, with C–H = 0.95–0.98 Å, and with U_iso(H) = 1.2U_eq.(CH) or 1.5U_eq.(CH₃), except for methanol hydroxyl H atoms, which were located in the difference Fourier map, refined isotropically with O–H distance restrained to 0.840 Å and then constrained to ride on their parent atoms (AFIX 3 instruction in SHELXL). The crystal data and refinement parameters are presented in Table 3.

Table 3 Crystal data and structure refinement parameters for 1

Identification code	Complex 1
Net formula	C57.875H55.75Mn3O14S4
Formula weight, g mol^−1	1268.33
Radiation	MoKα
Diffractometer	Xcalibur PX with Onyx CCD detector
T	100 K
Crystal size, mm	0.24 × 0.10 × 0.07
Crystal shape, color	Block, dark violet
Crystal system	Triclinic
Space group	P1̄
a, Å	13.263 (5) Å
b, Å	19.962 (8) Å
c, Å	21.953 (9) Å
α, deg	86.49 (5)
β, deg	88.31 (5)
γ, deg	89.30 (5)
Volume, Å^3	5798 (4) Å^3
Z	4
Density (calc.), g cm^−3	1.453
Absorption coefficient, mm^−1	0.85 mm^−1
F(000)	2616
Θ range for data collection, deg	2.5–26.6
Measured reflections	47 778
Reflections with I > 2σ(I)	7888
Unique reflections	22 944
Index ranges hkl	−16 → 14, −25 → 25, −27 → 27
Rint	0.137
Restraints/parameters	0/1407
Goodness of fit on F^2	1.00
R[F^2 > 2σ(F^2)]	0.093
wR(F^2)	0.201
Max electron density/e Å^−3	1.23
Min electron density/e Å^−3	−0.85

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Magnetic measurement

Magnetic susceptibility measurements on polycrystalline samples were carried out by means of a Quantum Design SQUID MPMS XL magnetometer. The dc measurements were performed in the temperature range 1.9–300 K at applied magnetic fields of 1000 Oe for T < 15 K and 10.000 Oe for T > 15 K. ac measurements were performed in the 2 to 5 K range under a dc field of 0 Oe and an ac field of 3.5 Oe. Diamagnetic corrections of the constituent atoms were estimated from Pascal's constants and experimental susceptibilities were also corrected for the temperature-independent paramagnetism and the magnetization of the sample holder.

Acknowledgements

The authors wish to thank Dr. M. Weselski for magnetic data collection. The authors are grateful to the University of Zanjan and Universidad de La Laguna for financial support of this study.

Notes and references

1. (a) J. S. Miller and M. Drilon, Magnetism: Molecules to Materials, Willey-VCH, Weinheim, 2002–2005, vol. I–V; (b) D. Gatteschi and R. Sessoli, Angew. Chem., Int. Ed., 2003, 42, 268.
2. J. N. Armor, Catal. Today, 2011, 163, 3.
3. (a) S. Signorella and C. Hureau, Coord. Chem. Rev., 2012, 256, 1229; (b) M. M. Whittaker, V. V. Barynin, S. V. Antonyuk and J. W. Whittaker, Biochemistry, 1999, 38, 9126.
4. (a) V. L. Pecoraro and W.-Y. Hsieh, Inorg. Chem., 2008, 47, 1765; (b) T. Wydrzynski, Photosystem II: The Light-Driven Water: Plastoquinone Oxidoreductase, Springer, New York, 2005; (c) W. Jiang, D. Yun, L. Saleh, E. W. Barr, G. Xing, L. M. Hoffart, M.-A. Maslak, C. Krebs and J. M. Bollinger, Science, 2007, 316, 1188.
5. V. Tangoulis, D. A. Malamatari, G. A. Spyroulias, C. P. Raptopoulou, A. Terzis and D. P. Kessissoglou, Inorg. Chem., 2000, 39, 2621.
6. (a) C. J. Milios, R. Inglis, A. Vinslava, R. Bagai, W. Wernsdorfer, S. Parsons, S. P. Perlepes, G. Christou and E. K. Brechin, J. Am. Chem. Soc., 2007, 129, 12505; (b) T. C. Stamatatos, D. Foguet-Albiol, S. C. Lee, C. C. Stoumpos, C. P. Raptopoulou, A. Terzis, W. Wernsdorfer, S. O. Hill, S. P. Perlepes and G. Christou, J. Am. Chem. Soc., 2007, 129, 9484; (c) C. Kachi-Terajima, H. Miyasaka, K. Sugiura, R. Clerac and H. Nojiri, Inorg. Chem., 2006, 45, 4381; (d) L. Lecren, W. Wernsdorfer, Y. G. Li, A. Vindigni, H. Miyasaka and R. Clerac, J. Am. Chem. Soc., 2007, 129, 5045.
7. G. Aromi, M. J. Knapp, J. P. Claude, J. C. Huffman, D. N. Hendrickson and G. Christou, J. Am. Chem. Soc., 1999, 121, 5489.
8. A. J. Tasiopoulos, A. Vinslava, W. Wernsdorfer, K. A. Abboud and G. Christou, Angew. Chem., Int. Ed., 2004, 43, 2117.
9. R. Celenligil-Cetin, P. Paraskevopoulou, N. Lalioti, Y. Sanakis, R. J. Staples, N. P. Rath and P. Stavropoulos, Inorg. Chem., 2008, 47, 10998.
10. E. M. Rumberger, S. J. Shah, C. C. Beedle, L. N. Zakharov, A. L. Rheingold and D. N. Hendrickson, Inorg. Chem., 2005, 44, 2742.
11. J. Mrozinski, A. Bienko, P. Kopel and V. Langer, Inorg. Chim. Acta, 2008, 361, 3723.
12. S. Giri, R. Biswas, A. Ghosh and S. K. Saha, Polyhedron, 2011, 30, 2717.
13. (a) R. D. Cannon and R. P. White, Prog. Inorg. Chem., 1988, 36, 195; (b) P. Christian, G. Rajaraman, A. Harrison, M. Helliwell, J. J. W. McDouall, J. Raftery and R. E. P. Winpenny, Dalton Trans., 2004, 2550; (c) C. I. Yang, P. Y. Feng, Y. T. Chen, Y. J. Tsai, G. H. Lee and H. L. Tsai, Polyhedron, 2011, 30, 3265; (d) M. H. Liu, C. I. Yang, G. H. Lee and H. L. Tsai, Inorg. Chem. Commun., 2011, 14, 1136; (e) T. C. Stamatatos, D. Foguet-Albiol, C. C. Stoumpos, C. P. Raptopoulou, A. Terzis, W. Wernsdorfer, S. P. Perlepes and G. Christou, Polyhedron, 2007, 26, 2165; (f) J. P. Geng, Z. X. Wang, M. X. Li and H. P. Xiao, Polyhedron, 2011, 30, 3134.
14. Q. W. Xie, X. Chen, K. Q. Hu, Y. T. Wang, A. L. Cui and H. Z. Kou, Polyhedron, 2012, 38, 213.
15. (a) J. P. Geng, Z. X. Wang, X. He, H. P. Xiao and M. X. Li, Inorg. Chem. Commun., 2011, 14, 997; (b) R. A. Coxall, A. Parkin, S. Parsons, A. A. Smith, G. A. Timco and R. E. P. Winpenny, J. Solid State Chem., 2001, 159, 321; (c) R. Wang, E. Gao, M. Hong, S. Gao, J. Luo, Z. Lin, L. Han and R. Cao, Inorg. Chem., 2003, 42, 5486.
16. (a) S. C. Shoner and P. P. Power, Inorg. Chem., 1992, 31, 1001; (b) C. Hureau, E. Anxolabehere-Mallart, G. Blondin, E. Riviere and M. Nierlich, Eur. J. Inorg. Chem., 2005, 4808.
17. (a) D. H. Shi, Z. L. You, C. Xu, Q. Zhang and H. L. Zhu, Inorg. Chem. Commun., 2007, 10, 404; (b) X. Y. Xu, T. T. Xu, S. R. Niu, D. Wang and X. Hu, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2006, 62, m2026; (c) J. Tang, J. S. Costa, G. Aromi, I. Mutikainen, U. Turpeinen, P. Gamez and J. Reedijk, Eur. J. Inorg. Chem., 2007, 4119; (d) T. C. Higgs, K. Spartalian, C. J. O. Connor, B. F. Matzanke and C. J. Carrano, Inorg. Chem., 1998, 37, 2263; (e) J. L. Ma, Z. L. You and H. L. Zhu, Acta Crystallogr., Sect. A: Found. Crystallogr., 2005, 61, m1286; (f) V. Chandrasekhar, R. Azhakar, B. Murugesapandian, T. Senapati, P. Bag, M. D. Pandey, S. K. Maurya and D. Goswami, Inorg. Chem., 2010, 49, 4008; (g) K. Z. Ha, Z. Kristallogr. – New Cryst. Struct., 2010, 225, 777; (h) M. Albrecht, M. Fiege, P. Kogerler, M. Speldrich, R. Frohlich and M. Engeser, Chem.–Eur. J., 2010, 16, 8797.
18. (a) V. Chandrasekhar, R. Azhakar, S. Zacchini, J. F. Bickley and A. Steiner, Inorg. Chem., 2005, 44, 4608; (b) V. Chandrasekhar, R. Azhakar, G. T. S. Andavan, V. Krishnan, S. Zacchini, J. F. Bickley, A. Steiner, R. J. Butcher and P. Kogerler, Inorg. Chem., 2003, 42, 5989.
19. (a) D. Zurita, I. Gautier-Luneau, S. Menage, J. L. Pierre and E. Saint-Aman, JBIC, J. Biol. Inorg. Chem., 1997, 2, 46; (b) L. Benisvy, A. J. Blake, D. Collison, E. S. Davies, C. D. Garner, E. J. L. McInnes, J. McMaster, G. Whittacker and C. Wilson, Chem. Commun., 2001, 1824; (c) Y. Shimazaki, S. Huth, A. Odani and O. Yamauchi, Angew. Chem., Int. Ed., 2000, 112, 1666; (d) E. Bill, J. Müller, T. Weyhermüller and K. Wieghardt, Inorg. Chem., 1999, 38, 5795; (e) P. Chaudhuri, M. Hess, J. Müller, K. Hildenbrand, E. Bill, T. Weyhermüller and K. Wieghardt, J. Am. Chem. Soc., 1999, 121, 9599; (f) T. K. Paine, T. Weyhermüller, K. Wieghardt and P. Chaudhuri, Inorg. Chem., 2002, 41, 6538; (g) S. Mukherjee, T. Weyhermüller, E. Bothe, K. Wieghardt and P. Chaudhuri, Eur. J. Inorg. Chem., 2003, 863.
20. (a) P. Chaudhuri and K. Wieghardt, Prog. Inorg. Chem., 2002, 50, 151; (b) H. Holm and E. I. Solomon, Chem. Rev., 1996, 96, 7; (c) T. Babcock, M. Espe, C. Hoganson, N. Lydakis-Simantiris, J. McCracken, W. Shi, S. Styring, C. Tommas and K. Warncke, Acta Chem. Scand., 1997, 51, 533; (d) J. Stubbe and W. A. Van der Donk, Chem. Rev., 1998, 98, 705.
21. (a) T. Weyhermuller, T. K. Paine, E. Bothe, E. Bill and P. Chaudhuri, Inorg. Chim. Acta, 2002, 337, 344; (b) T. K. Paine, T. Weyhermuller, E. Bothe, K. Wieghardt and P. Chaudhuri, Dalton Trans., 2003, 3136.
22. (a) P. Chaudhuri, M. Hess, T. Weyhermuller and K. Wieghardt, Angew. Chem., Int. Ed., 1999, 38, 1095; (b) Y. Wang, J. L. DuBois, B. Hedman, K. O. Hodgson and T. D. P. Stack, Science, 1998, 279, 537; (c) F. Thomas, G. Gelbon, I. G. Luneau, E. S. Aman and J. L. Pierre, Angew. Chem., Int. Ed., 2002, 41, 3047.
23. R. Bikas, H. Hosseini-Monfared, S. Alami, I. Pantenburg and G. Meyer, Z. Naturforsch., B: J. Chem. Sci., 2010, 65, 1457.
24. G. Mislin, E. Graf, M. W. Hosseini, A. D. Cian and J. Fischer, Tetrahedron Lett., 1999, 40, 1129.
25. C. Desroches, G. Pilet, S. A. Borshch, S. Parola and D. Luneau, Inorg. Chem., 2005, 44, 9112.
26. Y. Bi, W. Liao, X. Wang, X. Wang and H. Zhang, Dalton Trans., 2011, 40, 1849.
27. J. Zeller, I. J. Hewitt and U. Radius, Z. Anorg. Allg. Chem., 2006, 632, 2439.
28. A. Shockravi, R. Alizadeh, H. Aghabozorg, A. Moghimi, E. Rostami and S. Bavili, Phosphorus, Sulfur Silicon Relat. Elem., 2003, 178, 2519.
29. (a) I. B. Bersuker, The Jahn-Teller Effect, Cambridge University Press, 2006; (b) M. M. Yu, Z. H. Ni, C. C. Zhao, A. L. Cui and H. Z. Kou, Eur. J. Inorg. Chem., 2007, 5670; (c) Z. Lu and C. Fan, Inorg. Chem. Commun., 2011, 14, 1329; (d) H. S. Wang, X. J. Song, H. B. Zhou, Y. Chen, Y. L. Xu and Y. Song, Polyhedron, 2011, 30, 3206; (e) R. Celenligil-Cetin, P. Paraskevopoulou, N. Lalioti, Y. Sanakis, R. J. Staples, N. P. Rath and P. Stavropoulos, Inorg. Chem., 2008, 47, 10998.
30. A. W. Addison, T. N. Rao, J. Reedijk, J. Rijn and G. C. Verschoor, J. Chem. Soc., Dalton Trans., 1984, 1349.
31. Y. Quan, P. Yin, N. Han, A. Yang, H. Gao, J. Cui, W. Shi and P. Cheng, Inorg. Chem. Commun., 2009, 12, 469.
32. D. P. Kessissoglou, Coord. Chem. Rev., 1999, 185–186, 837.
33. O. Kahn, Molecular Magnetism, VCH, New York, 1993.
34. Q.-W. Xie, X.-M. Chen, K.-Q. Hu, Y.-T. Wang, A.-L. Cui and H.-Z. Kou, Polyhedron, 2012, 38, 213.
35. V. Tangoulis, D. A. Malamatari, K. Soulti, V. Stergiou, C. P. Raptopoulou, A. Terzis, T. A. Kabanos and D. P. Kessissoglou, Inorg. Chem., 1996, 35, 4974.
36. J. J. Borrás-Almenar, J. M. Clemente-Juan, E. Coronado and B. S. Tsukerblat, Inorg. Chem., 1999, 38, 6081.
37. J. J. Borrás-Almenar, J. M. Clemente-Juan, E. Coronado and B. S. Tsukerblat, J. Comput. Chem., 2001, 22, 985.
38. P.-H. Lin, S. Gorelsky, D. Savard, T. J. Burchell, W. Wernsdorfer, R. Clérac and M. Murugesu, Dalton Trans., 2010, 39, 7650.
39. A. R. Schake, E. A. Schmitt, A. J. Conti, W. E. Strieb, J. C. Huffman, D. N. Hendrickson and G. Christou, Inorg. Chem., 1991, 30, 3192.
40. H. Diril, H.-R. Chang, X. Zhang, S. K. Larsen, J. A. Potenza, C. G. Pierpont, H. J. Schugar, S. S. Isied and D. N. Hendrickson, J. Am. Chem. Soc., 1987, 109, 6207.
41. D. Mandal, P. B. Chatterjee, A. Bhattacherjee, K.-Y. Choi, R. Clérac and M. Chaudhuri, Inorg. Chem., 2009, 48, 1826.
42. D. Li, H. Wang, S. Wang, Y. Pan, C. Li, J. Dou and Y. Song, Inorg. Chem., 2010, 49, 3688.
43. A. Gelasco, M. L. Kirk, J. W. Kampf and V. L. Pecoraro, Inorg. Chem., 1997, 36, 1829.
44. (a) W. S. Gump and J. C. Vitucci, J. Am. Chem. Soc., 1945, 67, 238; (b) M. Gazdar and S. Smiles, J. Chem. Soc., 1910, 97, 2248.
45. CrysAlisPro in Xcalibur R software, Agilent Technologies, Inc., Yarnton, Oxfordshire, UK.
46. G. G. M. Sheldrick, A short history of SHELX, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008, 64, 112.

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Footnote

† CCDC 1001291. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c4ra05964f

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