FeIII in the high-spin state in di­methyl­ammonium bis­[3-eth­oxy­salicyl­aldehyde thio­semi­car­ba­zon­ato(2–)-κ3O2,N1,S]ferrate(III)

Powell, R.E.; Lees, M.R.; Tizzard, G.J.; Coles, S.J.; Yuan, Q.; Koningsbruggen, P.J. van

doi:10.1107/S2053229622011597

research papers

STRUCTURAL
CHEMISTRY

ISSN: 2053-2296

Volume 79| Part 1| January 2023| Pages 18-24

https://doi.org/10.1107/S2053229622011597

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Fe^III in the high-spin state in dimethylammonium bis[3-ethoxysalicylaldehyde thiosemicarbazonato(2–)-κ³O²,N¹,S]ferrate(III)

Robyn E. Powell,^a Martin R. Lees,^b Graham J. Tizzard,^c Simon J. Coles,^c Qingchun Yuan ^d and Petra J. van Koningsbruggen ^a ^*

^aCollege of Engineering and Physical Sciences, School of Infrastructure and Sustainable Engineering, Department of Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham, West Midlands, B4 7ET, United Kingdom, ^bDepartment of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom, ^cNational Crystallography Service, Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom, and ^dEnergy and Bioproducts Research Institute, College of Engineering and Physical Sciences, Aston University, Birmingham, B4 7ET, United Kingdom
^*Correspondence e-mail: p.vankoningsbruggen@aston.ac.uk

Edited by D. R. Turner, University of Monash, Australia (Received 7 November 2022; accepted 1 December 2022; online 1 January 2023)

The synthesis and crystal structure (100 K) of the title compound, [(CH₃)₂NH₂][Fe(C₁₀H₁₁O₂N₃S)₂], are reported. The asymmetric unit consists of an octahedral [Fe^III(L)₂]⁻ fragment, where L²⁻ is 3-ethoxysalicylaldehyde thiosemicarbazonate(2−), and a dimethylammonium cation. Each L²⁻ ligand binds with the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an Fe^IIIS₂N₂O₂ chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions, and mutually trans N atoms. The Fe^III ion is in the high-spin state at 100 K. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin Fe^III ion with D = 0.83 (1) cm⁻¹ and g = 2.

Keywords: Fe^III complex; high-spin; crystal structure; thiosemicarbazone; salicylaldehyde; magnetic susceptibility.

CCDC reference: 2223775

1. Introduction

The continuing research and development of switchable magnetic, optical and/or photomagnetic materials seeks to provide solutions for the societal desire towards more advanced electronic devices (e.g. larger data storage capacity and faster data processing) and their miniaturization by offering industry novel magnetic materials that can be implemented in electronic devices for information storage and as displays (Létard et al., 2004 ; Gütlich et al., 2004 ; Gütlich & Goodwin, 2004 ; van Koningsbruggen et al. 2004 ; Halcrow, 2013 ; Molnár et al., 2018 ; Senthil Kumar et al., 2017 ; Rubio-Giménez et al., 2019 ; Tissot et al., 2019 ; Karuppannan et al., 2021 ). Spin-crossover materials have attractive physical properties that make them suitable candidates for fulfilling these requirements. Such compounds exhibiting a temperature-dependent crossover between electronic states having a different magnetic moment were first discovered for iron(III) tris(dithiocarbamates) (Cambi & Szegö, 1931 , 1933 ). Since then, two main families of Fe^III spin-crossover systems have been extensively studied, i.e. those containing ligands sporting chalcogen donor atoms and those based on multidentate N,O-donating Schiff base-type ligands (van Koningsbruggen et al., 2004; Harding et al., 2016 ). It has been found that the magnetic interconversion between the low-spin (S = 1/2) and high-spin (S = 5/2) state in Fe^III systems can be triggered by a change in temperature or pressure, or by light irradiation (Hayami et al., 2000 , 2009 ; van Koningsbruggen et al., 2004; Harding et al., 2016).

The generation of Fe^III spin-crossover behaviour using particular salicylaldehyde thiosemicarbazone derivatives has been extensively studied by several research groups (van Koningsbruggen et al., 2004; Phonsri et al., 2017 ; Powell et al., 2014 , 2015 , 2020 , 2022 ; Powell, 2016 ; Yemeli Tido, 2010 ; Zelentsov et al., 1973 ; Ryabova et al., 1978 , 1981a ,b , 1982 ; Floquet et al., 2003 , 2006 , 2009 ; Li et al., 2013 , 2016 ).

Our research demonstrated that the electronic state of an Fe^III ion surrounded by two such tridentate O,N,S-thiosemicarbazonate ligands depends on the substituents and degree of deprotonation of the R-salicylaldehyde 4R′-thiosemicarbazone ligands, the identity of the counter-ion and the nature and degree of solvation (Powell et al., 2014, 2015, 2020, 2022; Powell, 2016; Yemeli Tido, 2010).

In fact, in solution, the free R-salicylaldehyde 4R′-thiosemicarbazone ligand (H₂L) exists in two tautomeric forms, i.e. the thione and thiol forms, as illustrated in Scheme 1. Moreover, the ligand may also be present in its neutral, anionic or dianionic form. We established that the formation of a particular type of Fe^III complex unit, i.e. neutral, monocationic or monoanionic, can be achieved by tuning the degree of deprotonation of the ligand through pH variation of the reaction solution during the synthesis (Powell et al., 2014, 2015, 2020, 2022; Powell, 2016; Yemeli Tido, 2010; Floquet et al., 2009).

We have thus been particularly proficient in preparing anionic Fe^III complexes of the general formula (cation⁺)[Fe(L²⁻)₂]·x(solvent), such as Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH, containing 3-ethoxysalicylaldehyde methylthiosemicarbazonate(2−) (Powell et al., 2014), Cs[Fe(5-Br-thsa)₂] containing 5-bromosalicylaldehyde thiosemicarbazonate(2−) (Powell et al., 2015) and NH₄[Fe(thsa)₂] containing salicylaldehyde thiosemicarbazonate(2−) (Powell et al., 2020). In all of these compounds, Fe^III exhibits the low-spin state.

Here we report a novel Fe^III compound of this family, namely, dimethylammonium bis[3-ethoxysalicylaldehyde thiosemicarbazonato(2–)-κ³O²,N¹,S]ferrate(III), [(CH₃)₂NH₂][Fe(3-OEt-thsa)₂], (I) (see Scheme 2), containing two dianionic tridentate ligands, i.e. 3-ethoxysalicylaldehyde thiosemicarbazonate(2−), whose structure was determined at 100 K and confirmed that Fe^III is in the high-spin state.

2. Experimental

2.1. Spectroscopic and magnetic measurements

A room-temperature IR spectrum of 3-ethoxysalicylaldehyde thiosemicarbazone within the range 4000–400 cm⁻¹ was recorded on a PerkinElmer FT–IR spectrometer Spectrum RXI using KBr pellets. IR spectroscopic measurements of (I) within the range 4000–600 cm⁻¹ were carried out at room temperature using an ATR (attenuated total reflectance) PerkinElmer FT–IR Frontier spectrometer.

¹H and ¹³C NMR spectra were recorded in DMSO-d₆ (dimethyl sulfoxide) using a Bruker cryomagnet BZH 300/52 spectrometer (300 MHz), with the recorded chemical shifts in δ (in parts per million) relative to an internal standard of tetramethylsilane (TMS).

Measurements of direct current (dc) magnetic susceptibility, χ_M, versus temperature, T, were conducted between 5 and 320 K, heating and cooling at a rate of 2 K min⁻¹ in an applied field, μ₀H, of 0.1 T using a Quantum Design MPMS-5S superconducting quantum interference device (SQUID) magnetometer. The SQUID magnetometer was calibrated using a standard palladium sample. The background due to the sample holder and the diamagnetic signal of the sample, estimated using Pascal's constants (Bain et al., 2008 ), was subtracted from the measured molar magnetic susceptibility χ_M.

2.2. Synthesis

The synthesis of 3-ethoxysalicylaldehyde thiosemicarbazone (H₂-3-OEt-thsa) was carried out according to the general procedure described by Yemeli Tido (2010) (yield: 11.14 g, 46.55 mmol, 95.0%; m.p. 224 °C). H₂-3-OEt-thsa is soluble in methanol, ethanol, acetone and DMSO. ¹H NMR (300 MHz, DMSO-d₆): δ (ppm) 11.39 (1H, s, OH), 9.02 (1H, s, S=C—NH), 8.40 (1H, s, N=C—H), 7.90–8.13 (2H, m, S=C—NH₂), 6.72–7.50 (aromatic 3H, m, C—H), 4.05 (2H, q, O—CH₂), 1.35 (3H, t, O—C—CH₃). ¹³C NMR (300 MHz, DMSO-d₆): δ (ppm) 182.8 (C=S), 147.4, 146.7 (C—O), 140.1 (C=N), 119.5, 118.7, 114.5 (C aromatic), 64.6 (C—N), 74.0 (O—CH₂), 15.1 (O—C—CH₃). IR (cm⁻¹, KBr): 3400 (νOH), 3169 (νNH), 3249 (νNH₂), 2935 (νCH₃), 2896 (νCH₂), 1618 (νC=N), 1535–1600 (νC=C), 1270 (νC—N), 1167 (νC=S).

The synthesis of [(CH₃)₂NH₂][Fe(3-OEt-thsa)₂], (I), was carried out as follows: Fe(NO₃)₃·9H₂O (1.0 mmol, 0.40 g) was dissolved in water (10 ml). The ligand H₂-3-OEt-thsa (2.0 mmol, 0.46 g) was dissolved in methanol (60 ml) with the addition of dimethylamine, 40 wt% in water (10 mmol, 0.51 ml). To this mixture, the Fe^III salt solution was added dropwise with constant stirring. The resulting dark-green solution was stirred and heated to 80 °C for approximately 10 min. The solution was then allowed to stand at room temperature until crystals had formed. The dark-green microcrystals were isolated by filtration and dried (yield: 0.30 g, 0.52 mmol, 52.0%). IR (cm⁻¹, ATR): 3436, 3414 (νNH), 3265, 3098 (νNH₂), 3012 (νCH₃), 2971 (νCH₂), 1614, 1586 (νC=N), 1570–1541 (νC=C ring), 1238 (νC—O), 1215 (νN—N), 1078 (νC—N), 736 (νC—S).

2.3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The H atoms of terminal amine atoms N103 and N3 were located in difference Fourier maps and refined with restrained N—H distances of 0.86 (2) Å and with U_iso(H) = 1.2U_eq(N). The remaining H atoms were included in the refinement in calculated positions and treated as riding on their parent atoms, with N—H distances of 0.91 Å and U_iso(H) = 1.2U_eq(N) for the amine N atom of the cation, C—H distances of 0.95 Å and U_iso(H) = 1.2U_eq(C) for aryl (–CH=) H atoms, C—H distances of 0.99 Å and U_iso(H) = 1.2U_eq(C) for secondary (–CH₂–) H atoms, and C—H distances of 0.98 Å and U_iso(H) = 1.5U_eq(C) for methyl (–CH₃) H atoms.

Table 1
Experimental details

Diffractometer: Rigaku AFC12 goniometer equipped with an enhanced sensitivity (HG) Saturn724+ detector mounted at the window of an FR-E+ SuperBright molybdenum rotating anode generator with VHF Varimax optics (70 µm focus).

Crystal data
Chemical formula	(C₂H₈N)[Fe(C₁₀H₁₁N₃O₂S)₂]
M_r	576.50
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	100
a, b, c (Å)	9.4359 (3), 16.0265 (5), 17.2333 (7)
β (°)	98.668 (4)
V (Å³)	2576.35 (17)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.79
Crystal size (mm)	0.08 × 0.05 × 0.01

Data collection
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2014 )
T_min, T_max	0.661, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	16969, 5903, 4415
R_int	0.055
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.044, 0.096, 1.02
No. of reflections	5903
No. of parameters	341
No. of restraints	4
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.38, −0.38
Computer programs: CrystalClear-SM Expert (Rigaku, 2013 ), CrysAlis PRO (Agilent, 2014), SUPERFLIP (Palatinus & Chapuis, 2007 ; Palatinus & van der Lee, 2008 ), SHELXL2014 (Sheldrick, 2015 ), OLEX2 (Dolomanov et al., 2009) and ORTEP-3 for Windows (Farrugia, 2012 ).

3. Results and discussion

In solution, the free ligand, i.e. 3-ethoxysalicylaldehyde thiosemicarbazone (H₂L), exists in two tautomeric forms, the thione and the thiol form, as illustrated in Scheme 1. Consequently, in Fe^III compounds, the ligand may be present as either one of the possible tautomers, and may be neutral, anionic or dianionic. Referring to the thiol tautomer, neutral H₂L has H atoms located on the phenol O atom and the thiol S atom. The first deprotonation step involving the phenol group results in the formation of 3-ethoxysalicylaldehyde thiosemicarbazone(1−) (abbreviated as HL⁻). Subsequent deprotonation yields 3-ethoxysalicylaldehyde thiosemicarbazonate(2−) (abbreviated as L²⁻).

The structure of dimethylammonium bis[3-ethoxysalicylaldehyde thiosemicarbazonato(2−)-κ³O²,N¹,S]ferrate(III), (I) (Fig. 1), was determined at 100 K. Compound (I) crystallized in the monoclinic space group P2₁/n, with Z = 4. The asymmetric unit consists of one formula unit, [(CH₃)₂NH₂][Fe(3-OEt-thsa)₂], with no atom on a special position. The Fe^III cation is coordinated by the thiolate S, phenolate O and imine N atoms of each of the two dianionic O,N,S-tridentate L²⁻ ligands. The donor atoms of the ligands are situated in two perpendicular planes, with the O and S atoms in cis positions, and mutually trans N atoms. Selected geometric parameters are listed in Table 2.

Table 2
Selected geometric parameters (Å, °)

Fe1—S1	2.4320 (6)	Fe1—O101	1.9595 (16)
Fe1—S101	2.4389 (7)	Fe1—N1	2.167 (2)
Fe1—O1	1.9806 (16)	Fe1—N101	2.131 (2)

S1—Fe1—S101	98.98 (2)	C108—S101—Fe1	95.71 (8)
O1—Fe1—S1	158.48 (5)	C2—O1—Fe1	127.41 (14)
O1—Fe1—S101	91.30 (5)	C102—O101—Fe1	130.25 (16)
O1—Fe1—N1	82.17 (7)	C7—N1—Fe1	124.80 (15)
O1—Fe1—N101	107.31 (7)	C8—N2—N1	113.96 (19)
O101—Fe1—S1	94.31 (5)	C107—N101—Fe1	123.56 (16)
O101—Fe1—S101	158.89 (5)	C108—N102—N101	114.09 (19)
O101—Fe1—O1	81.91 (7)	C2—C1—C7	121.2 (2)
O101—Fe1—N1	105.56 (7)	O1—C2—C1	122.4 (2)
O101—Fe1—N101	84.03 (7)	N1—C7—C1	125.3 (2)
N1—Fe1—S1	78.45 (5)	N2—C8—S1	125.75 (17)
N1—Fe1—S101	93.18 (5)	C102—C101—C107	121.2 (2)
N101—Fe1—S1	93.26 (5)	O101—C102—C101	123.1 (2)
N101—Fe1—S101	78.93 (5)	N101—C107—C101	125.9 (2)
N101—Fe1—N1	167.63 (7)	N102—C108—S101	125.65 (18)
C8—S1—Fe1	95.87 (8)

Figure 1
The molecular structure and atom-numbering scheme for (I)

. Displacement ellipsoids are drawn at the 50% probability level.

The Fe^IIIO₂N₂S₂ coordination sphere exhibits a distorted octahedral geometry, as evidenced by the bond angles of the Fe atom and the ligand donor atoms (vide infra). X-ray structural data of similar Fe^III–bis(ligand) compounds containing two dianionic thiosemicarbazonate(2−) ligands show that the Fe—S, Fe—O and Fe—N bond lengths are in the ranges 2.23–2.31, 1.93–1.95 and 1.88–1.96 Å, respectively, for low-spin Fe^III compounds, and in the ranges 2.40–2.44, 1.96–1.99 and 2.05–2.15 Å, respectively, for the corresponding high-spin Fe^III compounds (van Koningsbruggen et al., 2004). The bond lengths involving the Fe atom and the donor atoms in (I) correspond with Fe^III being in the high-spin state at 100 K.

Variable-temperature magnetic susceptibility measurements (5–320 K) confirm that the Fe^III ion in (I) is indeed in the high-spin state over this temperature range (Powell, 2016). High-spin Fe^III has also been evidenced in the related Cs[Fe(thsa)₂] compound at 103 (and 298 K) (Ryabova et al., 1981a). It is significant to note that the Fe—O distances seem to be less sensitive to the change in Fe^III spin state than the Fe—N and Fe—S distances, which may be related to the π-acceptor capability of the N- and S-donor atoms as opposed to the π-donor capability of the O-donor atoms. This is of particular significance when Fe^III is in the low-spin state, as increased π backbonding will lead to comparatively more pronounced shortening of the Fe—N and Fe—S bonds than of the Fe—O bonds (Powell et al., 2014).

Furthermore, the spin state of the Fe^III cation can be related to the bond angles of the FeO₂N₂S₂ coordination core. An analysis of the bond angles involving the opposite ligand donor atoms at 100 K is very enlightening, as it shows that the octahedral geometry of the present high-spin Fe^III compound, with O1—Fe1—S1 = 158.48 (5)°, O101—Fe1—S101 = 158.89 (5)° and N1—Fe1—N101 = 167.63 (7)°, is considerably less regular than that of the low-spin compound Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH, with the bond angles S11—Fe—O11 = 177.83 (14)°, S21—Fe—O21 = 178.01 (13)° and N11—Fe—N21 = 178.9 (2)° (Powell et al., 2014), which are closer to 180°. This is in agreement with the low-spin Fe^III ion adopting a more regular octahedral geometry than the high-spin Fe^III ion (van Koningsbruggen et al., 2004).

The ligands have been found to be in the dianionic form as no H atoms were located on the phenolate O (O1 and O101) or the thiolate S (S1 and S101) atoms. The charge of the two L²⁻ ligands is balanced by the presence of the monovalent dimethylammonium cation together with the trivalent iron cation. The tridentate ligands of the present compound are coordinated to the Fe^III cation by the thiolate S, phenolate O and imine N atoms, forming six- and five-membered chelate rings. The six-membered chelate ring involves a significantly less restricted bite angle [O1—Fe—N1 = 82.17 (7)° and O101—Fe—N101 = 84.03 (7)°] than the five-membered chelate ring [S1—Fe—N1 = 78.45 (5)° and S101—Fe—N101 = 78.93 (5)°]. The r.m.s. deviations from their least-squares plane of atoms of the six-membered chelate ring of both coordinated ligands are 0.197 and 0.177 Å for Fe1/N11/C17/C11/C12/O11 and Fe1/N101/C107/C101/C102/O101, respectively, and the corresponding values for the five-membered chelate rings are 0.129 and 0.102 Å for Fe1/N11/C12/C18/S11 and Fe1/N101/C102/C108/S101, respectively. It appears that the metal chelate rings deviate slightly from the ideal planar structure. Furthermore, the O—Fe—N and S—Fe—N bite angles of the six- and five-membered chelates are deficient by ca 38 and 30°, respectively, compared to the angle at the vertex of a regular hexagon (120°) or pentagon (108°), respectively. In comparison to other (cation⁺)[Fe(L²⁻)₂]·x(solvent) compounds of related ligands (Powell et al., 2014, 2015, 2020), the deficiency of the bite angle in both the six- and five-membered chelate rings is larger than expected, though it has been recognized that these other Fe^III bis(ligand) compounds contain Fe^III in the low-spin state, whereas the present compound contains Fe^III in the high-spin state. Consequently, (I) displays longer Fe^III–donor atom bond lengths, which are associated with more restricted bite angles. Moreover, the remaining bond angles involving each six-membered chelate ring (Table 2) are, as expected, within ca 5° of the value of 125°. However, the C—S—Fe bond angles involving each five-membered chelate ring are only about 95°, providing an additional deficiency of 13°. The additional deficiency can be offset by increasing the other bond angles within this five-membered chelate ring to ca 120°. It has been found that the N—N—C angles are <120° and the N—C—S angles are >120°; these values suggest sp² hybridization at the C and N atoms.

The stability of the Fe^III complex is further enhanced by the high degree of electron delocalization throughout the chelated ligands, which is evident from the geometric parameters. The C—S, C—N and N—N bond lengths of (I) show characteristics of a bond order between 1 (i.e. single bond) and 2 (i.e. double bond). The C8—S1 bond length of 1.746 (3) Å and the C108—S101 bond length of 1.752 (2) Å suggest partial electron delocalization of these C—S bonds. This feature has also been found in the structure of the related high-spin Fe^III compound Cs[Fe(thsa)₂] at 103 K (Ryabova et al., 1981a), in which the C—S bond lengths of 1.749 (9) and 1.761 (9) Å are indicative of partial electron delocalization.

In addition, the electron delocalization within each of the O,N,S-tridentate ligands is confirmed by a bond order larger than 1 for the C—N bond involving the deprotonated hydrazinic N atom, which is inferred from the lengths for the C7—N1 and C107—N101 bonds in (I) at 100 K of 1.301 (3) and 1.301 (3) Å, respectively, which correspond to the C—N bond lengths of 1.314 (10) and 1.303 (11) Å, respectively, for Cs[Fe(thsa)₂] at 103 K (Ryabova et al., 1981a).

Moreover, the N—N bond lengths of (I) at 100 K are N1—N2 of 1.395 (2) Å and N101—N102 of 1.399 (3) Å, which indicates partial electron delocalization within the five-membered chelate ring.

The hydrogen-bonding interactions of (I), identified using the default parameters of OLEX2 (Dolomanov et al., 2009 ), are listed in Table 3 and displayed in Fig. 2. The N atom of the dimethylammonium cation forms two hydrogen bonds: one contact is formed with the phenolate O atom of one ligand, whereas the second contact is formed with the ethoxy O atom of the salicylaldehyde moiety of the other ligand. The N201—H20A⋯O102 and N201—H20B⋯O1 contacts form an intramolecular hydrogen-bonded ring system, giving rise to an R₂²(9) ring (Bernstein et al., 1995 ).

Table 3
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N201—H20A⋯O102	0.91	1.97	2.877 (3)	174
N201—H20B⋯O1	0.91	1.86	2.766 (3)	173

Figure 2
The unit cell of (I)

, with displacement ellipsoids drawn at the 50% probability level.

Magnetic susceptibility versus temperature measurements for (I) were carried out to investigate the spin state of the Fe^III ion. The data collected on heating and cooling coincide over the temperature range studied. The temperature dependence of χ_MT collected on cooling between 320 and 5 K is displayed in Fig. 3. Above 100 K, χ_MT is temperature independent with a value of 4.41 (1) cm³ K mol⁻¹ [5.94 (1) µ_B/Fe]. This is just above the expected value of 4.38 cm³ K mol⁻¹ (5.92 µ_B/Fe) for Fe^III in its high-spin (S = 5/2) state with an electronic g factor of 2. χ_M⁻¹(T) is linear in T and a fit to a Curie–Weiss law between 100 and 320 K shown in Fig. 4 gives a Weiss temperature of −3.3 (1) K and an effective moment of 6.00 (1) µ_B/Fe.

Figure 3
χ_MT versus T for (I)

. The data were measured while cooling at a rate of 2 K min⁻¹ in an applied field μ₀H of 0.1 T.

Figure 4
Temperature dependence of the molar magnetic susceptibility, χ_M, for (I)

. The solid red lines show fits to the data using Equation (1)

, with D = 0.83 (1) cm⁻¹ and g = 2. The blue line shows a fit of χ_M⁻¹(T) above 100 K using a Curie–Weiss law.

χ_MT drops rapidly below 100 K. This may be due to weak (antiferro)magnetic interactions between neighbouring spins or may reflect a splitting of the S = 5/2 state (O'Connor, 1982 ). Studies using aligned single crystals are needed to differentiate between these possibilities. For splitting, the spin Hamiltonian can be written as H_S = H_CEF + H_z, where the crystalline electric field (CEF) term H_CEF = D[S_z² − S(S + 1)/3] + E(S_x² – S_y²), with D and E being the axial and rhombic zero-field splitting, respectively. The ⁶S high-spin state is split into three Kramers doublets. For E = 0, the doublets are separated by 2D and 6D from the lowest energy doublet. The Zeeman energy H_z = gμ_BHS_z and the molar susceptibility with a field along z is

$[{\chi }_{\rm M}={{{{N}_{\rm A}g}^{2 }{\mu }_{\rm B}^{2}}\over{4{k}_{\rm B}T}}\left[{{1 + {9e}^{-2X }+ {25e}^{-6X}}\over{1 + {e}^{-2X} + {e}^{-6X}}}\right], \eqno(1)]$

where X = D/k_BT, N_A is Avogadro's number and k_B is the Boltzmann constant (O'Connor, 1982). A fit gives D = 0.83 (1) cm⁻¹ with g = 2. D is in the range expected for high-spin Fe^III (Chen et al., 2002 ; Yemeli Tido et al., 2007 ). Fits with a finite E expected for a system with a rhombic distortion are possible, cf. Chen et al. (2002), but these require a knowledge of the ratio λ = E/D from other studies, such as electron paramagnetic resonance (EPR) spectroscopy.

It is of interest to compare the two Fe^III compounds that have so far been reported to contain the 3-ethoxysalicylaldehyde 4-R′-thiosemicarbazonate(2−) dianion. In Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH (Powell et al., 2014), Fe^III is low spin, whereas in the present [(CH₃)₂NH₂][Fe(3-OEt-thsa)₂] compound, (I), the metal ion adopts the high-spin state. The differences between the two compounds further involve: (i) the relative size of the R′ substituent on the terminal N atom of the thiosemicarbazide moiety, as (I) contains a H atom, whereas Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH (Powell et al., 2014) contains a methyl substituent; (ii) the difference in the size and intermolecular interactions involving the associated outer-sphere monovalent cation, i.e. (CH₃)₂NH₂⁺ versus Cs⁺; and (iii) the presence of a methanol solvent molecule in the crystal lattice of Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH (Powell et al., 2014). These differences are associated with (I) forming intramolecular ring systems through hydrogen bonds (vide supra), whereas Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH forms intermolecular hydrogen-bonded ring systems which link neighbouring Fe^III entities. These factors determine the arrangement of the Fe^III entities within the unit cell, which is further characterized by the space group P2₁/n, with Z = 4 and V = 2576.35 (17) Å³ for (I), with a volume of 644.09 Å³ per high-spin Fe^III formula unit, and the space group P $[\overline{1}]$ , with Z = 2 and V = 1369.5 (8) Å³ for Cs[Fe(3-OEt-thsa-Me)₂]·CH₃OH, with a volume of 684.75 Å³ per low-spin Fe^III formula unit (Powell et al., 2014); hence the volume increase associated with Fe^III being low-spin compared to high-spin is more than offset by the differences in substituents, composition and crystal packing.

Evidently, the intricate interplay between the variation in cation, ligand substituents and associated solvent molecules affects the crystal packing of compounds of this class of (cation⁺)[Fe(L²⁻)₂]·x(solvent) materials and allows for a variation of the spin state of Fe^III, with some members displaying temperature-dependent spin-crossover behaviour (van Koningsbruggen et al., 2004; Powell, 2016). Further studies by our group will additionally focus on tuning the spin state of Fe^III by varying the degree of deprotonation of the ligand.

Supporting information

CCDC reference: 2223775

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2053229622011597/jx3075sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2053229622011597/jx3075Isup2.hkl

Computing details top

Data collection: CrystalClear-SM Expert (Rigaku, 2013); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Dimethylammonium bis[3-ethoxysalicylaldehyde thiosemicarbazonato(2-)-κ³O²,N¹,S]ferrate(III) top

Crystal data top

(C₂H₈N)[Fe(C₁₀H₁₁N₃O₂S)₂]	F(000) = 1204
M_r = 576.50	D_x = 1.486 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71075 Å
a = 9.4359 (3) Å	Cell parameters from 7929 reflections
b = 16.0265 (5) Å	θ = 2.3–27.5°
c = 17.2333 (7) Å	µ = 0.79 mm⁻¹
β = 98.668 (4)°	T = 100 K
V = 2576.35 (17) Å³	Plate, dark green
Z = 4	0.08 × 0.05 × 0.01 mm

Data collection top

Rigaku AFC12 (Right) diffractometer	5903 independent reflections
Radiation source: Rotating Anode, Rigaku FRE+	4415 reflections with I > 2σ(I)
Confocal mirrors, VHF Varimax monochromator	R_int = 0.055
Detector resolution: 28.5714 pixels mm^-1	θ_max = 27.5°, θ_min = 2.3°
profile data from ω–scans	h = −12→11
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014)	k = −19→20
T_min = 0.661, T_max = 1.000	l = −22→20
16969 measured reflections

Refinement top

Refinement on F²	Primary atom site location: iterative
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.044	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.096	w = 1/[σ²(F_o²) + (0.042P)² + 0.8071P] where P = (F_o² + 2F_c²)/3
S = 1.02	(Δ/σ)_max = 0.001
5903 reflections	Δρ_max = 0.38 e Å⁻³
341 parameters	Δρ_min = −0.37 e Å⁻³
4 restraints

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. H atoms bonded to N3 and N103 were located in the difference map and then refined with U_iso 1.2 times the parent atoms and a geometrical distance restraint

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Fe1	0.70898 (4)	0.21635 (2)	0.50186 (2)	0.00856 (10)
S1	0.62044 (6)	0.25318 (4)	0.62279 (3)	0.01270 (14)
S101	0.84413 (7)	0.09133 (4)	0.54708 (4)	0.01227 (14)
O1	0.70288 (17)	0.18269 (10)	0.39082 (9)	0.0110 (4)
O2	0.84874 (18)	0.12675 (10)	0.27538 (10)	0.0161 (4)
O101	0.66835 (17)	0.32616 (10)	0.45361 (9)	0.0119 (4)
O102	0.52885 (18)	0.45436 (10)	0.38418 (9)	0.0137 (4)
N1	0.5051 (2)	0.15161 (12)	0.48756 (11)	0.0106 (4)
N2	0.3979 (2)	0.17493 (12)	0.53078 (12)	0.0117 (4)
N3	0.3409 (2)	0.25363 (14)	0.63117 (13)	0.0153 (5)
H3A	0.256 (2)	0.2433 (17)	0.6111 (15)	0.018*
H3B	0.369 (3)	0.2879 (14)	0.6684 (13)	0.018*
N101	0.9159 (2)	0.26779 (12)	0.54029 (11)	0.0103 (4)
N102	1.0392 (2)	0.21832 (12)	0.55538 (11)	0.0104 (4)
N103	1.1288 (2)	0.08691 (13)	0.56251 (13)	0.0157 (5)
H10A	1.116 (3)	0.0359 (11)	0.5552 (15)	0.019*
H10B	1.209 (2)	0.1093 (16)	0.5565 (16)	0.019*
C1	0.5548 (2)	0.05970 (14)	0.38160 (14)	0.0107 (5)
C2	0.6673 (3)	0.10847 (15)	0.35927 (13)	0.0104 (5)
C3	0.7393 (3)	0.07927 (15)	0.29831 (14)	0.0140 (5)
C4	0.6979 (3)	0.00603 (15)	0.25903 (14)	0.0154 (6)
H4	0.7461	−0.0122	0.2175	0.019*
C5	0.5848 (3)	−0.04148 (16)	0.28023 (14)	0.0173 (6)
H5	0.5567	−0.0919	0.2532	0.021*
C6	0.5141 (3)	−0.01476 (15)	0.34072 (14)	0.0144 (5)
H6	0.4374	−0.0470	0.3547	0.017*
C7	0.4709 (3)	0.08925 (15)	0.44005 (14)	0.0117 (5)
H7	0.3840	0.0608	0.4439	0.014*
C8	0.4427 (3)	0.22466 (14)	0.59064 (14)	0.0118 (5)
C9	0.9693 (3)	0.14200 (17)	0.33761 (15)	0.0200 (6)
H9A	1.0543	0.1106	0.3264	0.024*
H9B	0.9449	0.1221	0.3884	0.024*
C10	1.0037 (3)	0.23397 (18)	0.34309 (17)	0.0275 (7)
H10C	1.0318	0.2530	0.2935	0.041*
H10D	1.0828	0.2436	0.3860	0.041*
H10E	0.9190	0.2650	0.3533	0.041*
C101	0.8381 (3)	0.41371 (14)	0.53308 (14)	0.0107 (5)
C102	0.7139 (3)	0.40090 (14)	0.47803 (14)	0.0099 (5)
C103	0.6384 (3)	0.47241 (15)	0.44448 (14)	0.0116 (5)
C104	0.6755 (3)	0.55135 (15)	0.47206 (14)	0.0150 (5)
H104	0.6206	0.5981	0.4513	0.018*
C105	0.7940 (3)	0.56275 (15)	0.53065 (15)	0.0156 (6)
H105	0.8172	0.6170	0.5509	0.019*
C106	0.8772 (3)	0.49560 (15)	0.55903 (15)	0.0143 (5)
H106	0.9611	0.5042	0.5962	0.017*
C107	0.9385 (3)	0.34655 (14)	0.55569 (14)	0.0110 (5)
H107	1.0290	0.3613	0.5844	0.013*
C108	1.0136 (3)	0.13784 (15)	0.55374 (13)	0.0115 (5)
C109	0.4454 (3)	0.52495 (15)	0.34938 (14)	0.0150 (5)
H10F	0.5089	0.5660	0.3290	0.018*
H10G	0.3965	0.5528	0.3893	0.018*
C110	0.3359 (3)	0.49200 (16)	0.28312 (16)	0.0218 (6)
H11A	0.3854	0.4694	0.2416	0.033*
H11B	0.2722	0.5375	0.2618	0.033*
H11C	0.2794	0.4478	0.3031	0.033*
N201	0.5046 (2)	0.29205 (13)	0.31206 (12)	0.0164 (5)
H20A	0.5147	0.3449	0.3314	0.020*
H20B	0.5729	0.2598	0.3406	0.020*
C201	0.5291 (3)	0.29274 (18)	0.22933 (16)	0.0258 (7)
H20C	0.4541	0.3258	0.1978	0.039*
H20D	0.5265	0.2354	0.2093	0.039*
H20E	0.6230	0.3175	0.2260	0.039*
C202	0.3612 (3)	0.26016 (19)	0.32239 (17)	0.0282 (7)
H20F	0.2870	0.2954	0.2929	0.042*
H20G	0.3515	0.2613	0.3782	0.042*
H20H	0.3503	0.2027	0.3029	0.042*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Fe1	0.00729 (18)	0.00775 (18)	0.01073 (18)	−0.00032 (14)	0.00164 (13)	−0.00020 (13)
S1	0.0093 (3)	0.0159 (3)	0.0132 (3)	−0.0012 (3)	0.0025 (2)	−0.0035 (2)
S101	0.0096 (3)	0.0095 (3)	0.0177 (3)	−0.0001 (2)	0.0021 (2)	0.0006 (2)
O1	0.0119 (9)	0.0094 (9)	0.0121 (9)	−0.0015 (7)	0.0028 (7)	−0.0021 (7)
O2	0.0157 (10)	0.0200 (10)	0.0136 (9)	−0.0029 (8)	0.0049 (7)	−0.0004 (7)
O101	0.0135 (9)	0.0076 (9)	0.0140 (9)	0.0003 (7)	0.0003 (7)	−0.0006 (7)
O102	0.0166 (10)	0.0093 (9)	0.0145 (9)	0.0046 (7)	−0.0003 (7)	0.0016 (7)
N1	0.0104 (11)	0.0108 (10)	0.0109 (10)	0.0010 (8)	0.0023 (8)	0.0009 (8)
N2	0.0087 (11)	0.0130 (11)	0.0144 (11)	−0.0008 (8)	0.0051 (8)	−0.0024 (8)
N3	0.0097 (11)	0.0175 (12)	0.0194 (12)	−0.0023 (10)	0.0047 (9)	−0.0064 (9)
N101	0.0069 (10)	0.0132 (11)	0.0109 (10)	0.0005 (8)	0.0018 (8)	0.0005 (8)
N102	0.0058 (10)	0.0107 (10)	0.0143 (11)	0.0019 (8)	−0.0001 (8)	−0.0002 (8)
N103	0.0097 (11)	0.0107 (11)	0.0264 (13)	−0.0001 (10)	0.0020 (9)	−0.0026 (9)
C1	0.0097 (13)	0.0095 (12)	0.0122 (12)	0.0020 (10)	−0.0008 (10)	0.0007 (9)
C2	0.0097 (13)	0.0111 (12)	0.0094 (12)	0.0033 (10)	−0.0020 (9)	−0.0002 (9)
C3	0.0123 (13)	0.0159 (13)	0.0138 (13)	0.0013 (10)	0.0023 (10)	0.0012 (10)
C4	0.0199 (14)	0.0174 (14)	0.0097 (13)	0.0036 (11)	0.0045 (11)	−0.0027 (10)
C5	0.0234 (15)	0.0123 (13)	0.0144 (13)	−0.0012 (11)	−0.0031 (11)	−0.0051 (10)
C6	0.0151 (14)	0.0100 (13)	0.0170 (13)	−0.0013 (10)	−0.0014 (10)	0.0014 (10)
C7	0.0093 (13)	0.0108 (12)	0.0151 (13)	−0.0018 (10)	0.0018 (10)	0.0014 (9)
C8	0.0114 (13)	0.0104 (12)	0.0142 (13)	−0.0004 (10)	0.0041 (10)	0.0031 (9)
C9	0.0148 (14)	0.0293 (16)	0.0159 (14)	−0.0016 (12)	0.0019 (11)	−0.0041 (11)
C10	0.0275 (17)	0.0341 (18)	0.0220 (15)	−0.0162 (14)	0.0071 (13)	−0.0039 (12)
C101	0.0098 (12)	0.0089 (12)	0.0142 (13)	−0.0004 (10)	0.0042 (10)	−0.0001 (9)
C102	0.0128 (13)	0.0079 (12)	0.0104 (12)	0.0005 (10)	0.0061 (10)	0.0011 (9)
C103	0.0103 (13)	0.0117 (12)	0.0137 (13)	0.0014 (10)	0.0047 (10)	0.0013 (9)
C104	0.0186 (14)	0.0106 (13)	0.0173 (13)	0.0032 (11)	0.0073 (11)	0.0037 (10)
C105	0.0174 (14)	0.0094 (13)	0.0212 (14)	−0.0020 (11)	0.0067 (11)	−0.0035 (10)
C106	0.0112 (13)	0.0127 (13)	0.0191 (14)	−0.0030 (10)	0.0023 (10)	−0.0036 (10)
C107	0.0090 (13)	0.0111 (12)	0.0124 (12)	−0.0017 (10)	0.0005 (10)	0.0007 (9)
C108	0.0116 (13)	0.0133 (13)	0.0096 (12)	0.0020 (10)	0.0019 (10)	0.0008 (9)
C109	0.0153 (14)	0.0136 (13)	0.0168 (13)	0.0060 (11)	0.0046 (11)	0.0061 (10)
C110	0.0223 (15)	0.0217 (15)	0.0209 (15)	0.0078 (12)	0.0014 (12)	0.0061 (11)
N201	0.0182 (12)	0.0157 (12)	0.0135 (11)	0.0040 (9)	−0.0035 (9)	0.0002 (9)
C201	0.0339 (18)	0.0268 (16)	0.0171 (15)	0.0033 (13)	0.0047 (13)	−0.0020 (12)
C202	0.0231 (16)	0.0317 (17)	0.0290 (17)	0.0007 (13)	0.0015 (13)	0.0074 (13)

Geometric parameters (Å, º) top

Fe1—S1	2.4320 (6)	C6—H6	0.9500
Fe1—S101	2.4389 (7)	C7—H7	0.9500
Fe1—O1	1.9806 (16)	C9—H9A	0.9900
Fe1—O101	1.9595 (16)	C9—H9B	0.9900
Fe1—N1	2.167 (2)	C9—C10	1.509 (4)
Fe1—N101	2.131 (2)	C10—H10C	0.9800
S1—C8	1.746 (3)	C10—H10D	0.9800
S101—C108	1.752 (2)	C10—H10E	0.9800
O1—C2	1.330 (3)	C101—C102	1.407 (3)
O2—C3	1.387 (3)	C101—C106	1.417 (3)
O2—C9	1.461 (3)	C101—C107	1.448 (3)
O101—C102	1.320 (3)	C102—C103	1.425 (3)
O102—C103	1.381 (3)	C103—C104	1.378 (3)
O102—C109	1.455 (3)	C104—H104	0.9500
N1—N2	1.395 (2)	C104—C105	1.401 (4)
N1—C7	1.301 (3)	C105—H105	0.9500
N2—C8	1.322 (3)	C105—C106	1.377 (4)
N3—H3A	0.840 (17)	C106—H106	0.9500
N3—H3B	0.857 (17)	C107—H107	0.9500
N3—C8	1.352 (3)	C109—H10F	0.9900
N101—N102	1.399 (3)	C109—H10G	0.9900
N101—C107	1.301 (3)	C109—C110	1.515 (4)
N102—C108	1.312 (3)	C110—H11A	0.9800
N103—H10A	0.834 (17)	C110—H11B	0.9800
N103—H10B	0.854 (17)	C110—H11C	0.9800
N103—C108	1.350 (3)	N201—H20A	0.9100
C1—C2	1.417 (3)	N201—H20B	0.9100
C1—C6	1.409 (3)	N201—C201	1.478 (3)
C1—C7	1.451 (3)	N201—C202	1.482 (3)
C2—C3	1.414 (3)	C201—H20C	0.9800
C3—C4	1.382 (3)	C201—H20D	0.9800
C4—H4	0.9500	C201—H20E	0.9800
C4—C5	1.403 (3)	C202—H20F	0.9800
C5—H5	0.9500	C202—H20G	0.9800
C5—C6	1.387 (3)	C202—H20H	0.9800

S1—Fe1—S101	98.98 (2)	C10—C9—H9A	109.6
O1—Fe1—S1	158.48 (5)	C10—C9—H9B	109.6
O1—Fe1—S101	91.30 (5)	C9—C10—H10C	109.5
O1—Fe1—N1	82.17 (7)	C9—C10—H10D	109.5
O1—Fe1—N101	107.31 (7)	C9—C10—H10E	109.5
O101—Fe1—S1	94.31 (5)	H10C—C10—H10D	109.5
O101—Fe1—S101	158.89 (5)	H10C—C10—H10E	109.5
O101—Fe1—O1	81.91 (7)	H10D—C10—H10E	109.5
O101—Fe1—N1	105.56 (7)	C102—C101—C106	119.9 (2)
O101—Fe1—N101	84.03 (7)	C102—C101—C107	121.2 (2)
N1—Fe1—S1	78.45 (5)	C106—C101—C107	118.4 (2)
N1—Fe1—S101	93.18 (5)	O101—C102—C101	123.1 (2)
N101—Fe1—S1	93.26 (5)	O101—C102—C103	118.8 (2)
N101—Fe1—S101	78.93 (5)	C101—C102—C103	118.1 (2)
N101—Fe1—N1	167.63 (7)	O102—C103—C102	114.1 (2)
C8—S1—Fe1	95.87 (8)	C104—C103—O102	125.0 (2)
C108—S101—Fe1	95.71 (8)	C104—C103—C102	120.8 (2)
C2—O1—Fe1	127.41 (14)	C103—C104—H104	119.9
C3—O2—C9	114.40 (18)	C103—C104—C105	120.1 (2)
C102—O101—Fe1	130.25 (16)	C105—C104—H104	119.9
C103—O102—C109	116.38 (18)	C104—C105—H105	119.9
N2—N1—Fe1	120.93 (14)	C106—C105—C104	120.3 (2)
C7—N1—Fe1	124.80 (15)	C106—C105—H105	119.9
C7—N1—N2	114.27 (19)	C101—C106—H106	119.9
C8—N2—N1	113.96 (19)	C105—C106—C101	120.3 (2)
H3A—N3—H3B	127 (3)	C105—C106—H106	119.9
C8—N3—H3A	115.3 (19)	N101—C107—C101	125.9 (2)
C8—N3—H3B	116.1 (18)	N101—C107—H107	117.1
N102—N101—Fe1	122.38 (14)	C101—C107—H107	117.1
C107—N101—Fe1	123.56 (16)	N102—C108—S101	125.65 (18)
C107—N101—N102	113.96 (19)	N102—C108—N103	116.7 (2)
C108—N102—N101	114.09 (19)	N103—C108—S101	117.50 (18)
H10A—N103—H10B	120 (3)	O102—C109—H10F	110.2
C108—N103—H10A	118.5 (19)	O102—C109—H10G	110.2
C108—N103—H10B	116.3 (19)	O102—C109—C110	107.7 (2)
C2—C1—C7	121.2 (2)	H10F—C109—H10G	108.5
C6—C1—C2	119.4 (2)	C110—C109—H10F	110.2
C6—C1—C7	119.1 (2)	C110—C109—H10G	110.2
O1—C2—C1	122.4 (2)	C109—C110—H11A	109.5
O1—C2—C3	118.7 (2)	C109—C110—H11B	109.5
C3—C2—C1	118.8 (2)	C109—C110—H11C	109.5
O2—C3—C2	119.4 (2)	H11A—C110—H11B	109.5
C4—C3—O2	119.6 (2)	H11A—C110—H11C	109.5
C4—C3—C2	120.9 (2)	H11B—C110—H11C	109.5
C3—C4—H4	119.9	H20A—N201—H20B	107.7
C3—C4—C5	120.2 (2)	C201—N201—H20A	108.9
C5—C4—H4	119.9	C201—N201—H20B	108.9
C4—C5—H5	120.0	C201—N201—C202	113.4 (2)
C6—C5—C4	119.9 (2)	C202—N201—H20A	108.9
C6—C5—H5	120.0	C202—N201—H20B	108.9
C1—C6—H6	119.6	N201—C201—H20C	109.5
C5—C6—C1	120.7 (2)	N201—C201—H20D	109.5
C5—C6—H6	119.6	N201—C201—H20E	109.5
N1—C7—C1	125.3 (2)	H20C—C201—H20D	109.5
N1—C7—H7	117.3	H20C—C201—H20E	109.5
C1—C7—H7	117.3	H20D—C201—H20E	109.5
N2—C8—S1	125.75 (17)	N201—C202—H20F	109.5
N2—C8—N3	116.2 (2)	N201—C202—H20G	109.5
N3—C8—S1	118.00 (19)	N201—C202—H20H	109.5
O2—C9—H9A	109.6	H20F—C202—H20G	109.5
O2—C9—H9B	109.6	H20F—C202—H20H	109.5
O2—C9—C10	110.2 (2)	H20G—C202—H20H	109.5
H9A—C9—H9B	108.1

Fe1—S1—C8—N2	18.8 (2)	C3—O2—C9—C10	−129.0 (2)
Fe1—S1—C8—N3	−163.13 (18)	C3—C4—C5—C6	0.2 (4)
Fe1—S101—C108—N102	17.0 (2)	C4—C5—C6—C1	−0.3 (4)
Fe1—S101—C108—N103	−167.08 (18)	C6—C1—C2—O1	174.2 (2)
Fe1—O1—C2—C1	38.7 (3)	C6—C1—C2—C3	−2.4 (3)
Fe1—O1—C2—C3	−144.75 (18)	C6—C1—C7—N1	172.3 (2)
Fe1—O101—C102—C101	20.9 (3)	C7—N1—N2—C8	165.6 (2)
Fe1—O101—C102—C103	−162.28 (15)	C7—C1—C2—O1	0.7 (4)
Fe1—N1—N2—C8	−14.1 (3)	C7—C1—C2—C3	−175.8 (2)
Fe1—N1—C7—C1	−8.6 (4)	C7—C1—C6—C5	174.9 (2)
Fe1—N101—N102—C108	−8.4 (3)	C9—O2—C3—C2	60.1 (3)
Fe1—N101—C107—C101	−15.1 (3)	C9—O2—C3—C4	−122.8 (3)
O1—C2—C3—O2	2.7 (3)	C101—C102—C103—O102	172.33 (19)
O1—C2—C3—C4	−174.3 (2)	C101—C102—C103—C104	−7.8 (3)
O2—C3—C4—C5	−178.3 (2)	C102—C101—C106—C105	0.1 (3)
O101—C102—C103—O102	−4.6 (3)	C102—C101—C107—N101	−12.6 (4)
O101—C102—C103—C104	175.2 (2)	C102—C103—C104—C105	3.8 (3)
O102—C103—C104—C105	−176.4 (2)	C103—O102—C109—C110	177.88 (19)
N1—N2—C8—S1	−6.2 (3)	C103—C104—C105—C106	2.3 (4)
N1—N2—C8—N3	175.6 (2)	C104—C105—C106—C101	−4.2 (4)
N2—N1—C7—C1	171.7 (2)	C106—C101—C102—O101	−177.3 (2)
N101—N102—C108—S101	−8.5 (3)	C106—C101—C102—C103	5.8 (3)
N101—N102—C108—N103	175.57 (19)	C106—C101—C107—N101	176.1 (2)
N102—N101—C107—C101	168.3 (2)	C107—N101—N102—C108	168.2 (2)
C1—C2—C3—O2	179.4 (2)	C107—C101—C102—O101	11.5 (3)
C1—C2—C3—C4	2.3 (4)	C107—C101—C102—C103	−165.3 (2)
C2—C1—C6—C5	1.4 (4)	C107—C101—C106—C105	171.4 (2)
C2—C1—C7—N1	−14.3 (4)	C109—O102—C103—C102	178.22 (18)
C2—C3—C4—C5	−1.2 (4)	C109—O102—C103—C104	−1.6 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N201—H20A···O102	0.91	1.97	2.877 (3)	174
N201—H20B···O1	0.91	1.86	2.766 (3)	173

Acknowledgements

We thank the EPSRC UK National Crystallography Service (Coles & Gale, 2012 ) at the University of Southampton for the collection of the crystallographic data.

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