Crystal structures of two isotypic lanthanide(III) complexes: triaqua[2,6-diacetylpyridine bis(benzoylhydrazone)]methanollanthanide(III) trichloride methanol disolvates (Ln III = Tb and Dy)

Two isotypic complexes of TbIII and DyIII with the ligand 2,6-diacetylpyridine bis(benzoylhydrazone) have been synthesized and structurally characterized.


Chemical context
Molecule-based magnets based on lanthanide ions have attracted much attention because of their large magnetic moments and magnetic anisotropy. The design of building units, such as the coordination-acceptor or coordinationdonor magnetic units, is a key process in the construction of multi-dimensional magnetic materials. Some lanthanide complexes with 2,6-diacetylpyridine bis(benzoylhydrazone as ligand (DAPBH 2 ) have been reported, viz. for La III (Thomas et al., 1979), Yb III (Pan et al., 1989), Eu III (Gao & Wang, 2012), Dy III (Batchelor et al., 2014) and for La III and Dy III (Gao et al., 2016). The Dy complexes having two DAPBH 2 ligands (Batchelor et al., 2014) have demonstrated attractive singlemolecule magnet behaviour, indicating that DAPBH 2 ligands are useful for constructing magnetic units. For the use of DAPBH 2 complexes as building blocks, coordination active sites are needed. The DAPBH 2 ligand is pentadentate, thus it can make coordination sites in the axial positions of the lanthanide ion. These complexes have coordinated or noncoordinated nitrate ions, which can disturb the coordination of coordination-donor units. We report herein on the Tb III and Dy III complexes with the DAPBH 2 ligand containing noncoordinating chloride ions as the coordination-acceptor building units.
parameters. The representative molecular structure of the Tb III complex is shown in Fig. 1.
The lanthanide ion is surrounded by six oxygen atoms and three nitrogen atoms, and the coordination polyhedron is a distorted capped square antiprism. The equatorial coordination site of the Ln III ion is occupied by an N 3 O 2 atom set of a pentadentate DAPBH 2 ligand. Selected bond lengths and bond angles for both complexes are compared in Table 1. The Ln-donor bond distances are in the range of 2.321 (2)-2.596 (2) Å for the Tb III complex and 2.313 (2)-2.584 (2) Å for the Dy III complex. The bond distances for the Dy III complex are slightly shorter than those of the Tb III complex as a result of the lanthanide contraction effect. The DAPBH 2 ligand is approximately planar, and the Ln III ion lies out of the mean plane (O1/N2/N3/N4/O2) by a distance of 0.5754 (3) Å for the Tb III complex and 0.5702 (3) Å for the Dy III complex. The coordination of the DAPBH 2 ligand to the lanthanide ion shows a bent arrangement [bond angles O1-Ln-N4 and O2-Ln-N2 are 149.40 (6) and 152.08 (7) , respectively, for the Tb III complex, and 149.36 (7) and 151.76 (8) , respectively, for the Dy III complex]. These coordination features are similar to those reported for the dysprosium DAPBH 2 nitrate complex (Gao et al., 2016). Three water molecules and one methanol molecule are involved in the coordination sphere of the Ln III ion. The asymmetric unit consists of the Ln III complex, three chlorides as counter-ions, and two methanol solvent molecules.

Supramolecular features
In the crystals, the lanthanide complexes are connected by O-HÁ Á ÁCl, N-HÁ Á ÁCl, O-HÁ Á ÁO, C-HÁ Á ÁCl and C-HÁ Á ÁO hydrogen bonds (Tables 2 and 3). The representative crystal structure of the Tb III complex is discussed here and the crystal packing is shown in Figs. 2

Figure 2
A view along the b axis of the hydrogen-bonded (dashed lines) layer structure of the Tb III complex. The Cl À ions are shown as green balls and the C-bound H atoms have been omitted for clarity.

Figure 1
Molecular structure of the Tb III complex, showing the selected atomlabelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Funding information
SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 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.