Bis(3,5-dimethoxy-2-{[2-(pyridin-2-yl)ethylimino-κN]methyl}phenolato-κO)bis(dimethyl sulfoxide)manganese(III) perchlorate methanol 0.774-solvate

The title complex contains a central octahedrally coordinated MnIII cation with to two bidentate Schiff base ligands occupying the equatorial positions and two dimethyl sulfoxide ligands occupying the axial positions. In addition, disordered perchlorate anions and solvent molecules with a site-occupancy factor corresponding to that of the major fraction of the anions.


Chemical context
Single-molecule magnets (SMMs) are a class of coordination compounds that attract a great deal of scientific attention because they exhibit magnetic bistability at low temperatures (Christou et al., 2000;Gatteschi et al., 2006). These finite size (zero-dimensional) molecules possess a high-spin ground state S t and a magnetic anisotropy of the easy-axis type (negative zero-field splitting parameter D), which causes a slow relaxation of the magnetization at low temperatures, resulting in a hysteresis of the magnetization of purely molecular origin (Sessoli et al., 1993a,b;Gatteschi et al., 1994;Aubin et al., 1998;Gatteschi & Sessoli, 2003;Long, 2003;Thomas et al., 1996). SMMs promise access to dynamic random access memory devices for quantum computing and to ultimate high-density memory storage devices in which each bit of digital information is stored on a single molecule (Tejada, 2001;Awschalom et al., 1992;Leuenberger & Loss, 2001;Cornia et al., 2003;Dahlberg & Zhu, 1995).
The archetype of SMMs is the family of dodecanuclear manganese complexes, [Mn 12 O 12 (O 2 CR) 16 (OH 2 ) 4 ], Mn12 (Lis, 1980;Sessoli et al., 1993a,b;Boyd et al., 1988;Tsai et al., 1994;Sun et al., 1998;Boskovic et al., 2002). Since the discovery of the SMM behavior of Mn12, a lot of synthetic effort has been devoted to the preparation of new molecules with an increased anisotropy barrier. In this respect, it is interesting to note that ISSN 2056-9890 already a dimeric Mn III salen complex behaves as an SMM (Miyasaka et al., 2004).
An undeveloped field in this chemistry is the use of manganese complexes of Schiff base ligands as precursors in the synthesis of SMMs. In a continuation of our studies in manganese chemistry with Schiff base ligands as precursors to SSMs (Egekenze et al., 2017a,b,c), we report the structure of bis(3,5-dimethoxy-2-{[2-(pyridin-2-yl)ethylimino-N]methyl}phenolato-O)bis(dimethyl sulfoxide)manganese(III) perchlorate methanol 0.774-solvate.

Structural commentary
In the structure of the title compound ( Fig. 1), the cation contains a central octahedrally coordinated Mn III cation, with two bidentate Schiff base ligands occupying the equatorial positions and two dimethyl sulfoxide (DMSO) ligands occupying the axial positions. There are two independant cations in the asymmetric unit, with the Mn III atoms of both cations being positioned on crystallographic centers of inversion. The perchlorate anion is disordered over two equivalent conformations, with occupancies of 0.744 (3) and 0.226 (3). In addition, there is a disordered methanol solvent molecule in the crystal lattice.

Figure 1
Diagram of one of the two equivalent cations, showing the atom labeling.  (Groom et al., 2016) for compounds of manganese Schiff base complexes with attached DMSO ligands showed only one other example (Glaser et al., 2007) of a bis-DMSO complex of an Mn III Schiff base. In this case, the DMSO ligands were also occupying axial positions. If the search was restricted to a single coordinating DMSO ligand, there was one relevant example (Bermejo et al., 1994), aqua[N,N 0 -bis(3-bromo-5-nitrosalicylidene)-1,2-diamino-(2-methyl)ethane](dimethyl sulfoxide)manganese(II), which, however, contains both Mn II and a tetradentate ligand and therefore no Jahn-Teller distorsion was observed.

Supramolecular features
In the crystal structure, intermolecularstacking between the non-coordinating pyridine rings of each cation is observed with a perpendicular stacking distance of 3.623 Å and a slippage of 1.321 Å (symmetry code 1 À x,, 1 À y, 1 À z). Thisstacking, along with extensive O-HÁ Á ÁO hydrogen bonding and C-HÁ Á ÁO interactions ( Fig. 2   A solution of 1.3985 g (11.4 mmol) of 2-(pyridin-2-yl)ethanamine in 15 ml of methanol was mixed with a solution of 2.0874 g (11.5 mmol) of 4,6-dimethoxysalicylic aldehyde in 15 ml of methanol to obtain a dark-green solution. The solution was refluxed for 4 h. The thick dark-brown oil obtained was recrystallized from dichloromethane by slow evaporation of the solvent (yield: 3.02 g, 87%). Characterization data for C 16 H 18 N 2 O 3 are as follows; molecular mass: calculated for [C 16 H 19 50, 5.85, 7.25, 7.58, 8.28, (s, 1H ArH); 7.10 (d, 2H); 3.08 (d, 2H, CH 2 ); 3.88 (d, 2H, CH 2 ); 3.70 (m, 6H, 2(OCH 3 ). 9.2 mmol) in methanol was added to a mixture of 3,5-dimethoxy-2-{[2-(pyridin-2-yl)ethylimino]methyl}phenol (2.6252 g, 9.2 mmol) and triethylamine (C 6 H 15 N; 1.65 ml, 9.2 mmol). The solution turned dark brown. It was refluxed for 4 h and cooled to room temperature. The solvent was reduced with a rotary evaporator and the resulting precipitate was filtered off by suction, washed with diethyl ether and dried in the desiccator. The precipitate was recrystallized from methanol and diethyl ether and crystals suitable for X-ray analysis were grown by slow evaporation of a DMSO solution in a yield of 2.89 g

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The perchlorate anion is disordered over two equivalent conformations, with occupancies of 0.744 (3) (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008). Special details 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.