In the title compound, (C7H11N2)[Er(H2O)8]Cl4·H2O, the asymmetric unit consists of one 4-(dimethyl­amino)­pyridinium and one octa­aqua­erbium cation balanced by four Cl− anions, and one water mol­ecule. The 4-(dimethyl­amino)­pyridinium cation is protonated at the pyridine N atom. The dimethyl­amino group (C/N/C) lies close to the plane of the pyridinium ring, making a dihedral angle of 4.5 (3)°. In the crystal, the [Er(H2O)8]3+ cations are linked via O—H⋯O and O—H⋯Cl hydrogen bonds, forming two-dimensional networks propagating in the ab plane. These networks are linked via O—H⋯O and O—H⋯Cl hydrogen bonds, forming a three-dimensional network. The 4-(dimethyl­amino)­pyridinium cations are located in the cavities and are linked to the framework via N—H⋯Cl, C—H⋯O and C—H⋯Cl hydrogen bonds.
For similar structures in this series involving 4-(dimethyl­amino)­pyridinium, see: Benslimane et al. (2012a ,b ). For details of the Cambridge Structural Database, see: Allen (2002 ). For hydrogen-bond motifs see: Bernstein et al. (1995 ).
Symmetry codes: (i) x-1, y, z; (ii) -x+2, -y+1, -z+1; (iii) x, y-1, z; (iv) x+1, y, z; (v) -x+2, -y+1, -z; (vi) -x+1, -y, -z; (vii) -x+1, -y+1, -z; (viii) -x+2, -y, -z+1.
The title compound is part of a series of lanthanide complexes with the organic cation 4-(dimethylamino)pyridinium, for example: (C7H10N2)2.LaCl(H2O)8.Cl4.3H2O (I) (Benslimane et al., 2012a) and (C7H10N2)3.[Nd2Cl4(H2O)10].Cl5.2H2O (II) (Benslimane et al., 2012b).
The title compound (III) contains an inorganic [Er(H2O)8]3+ and an organic (C7H10N2)+ cation equilibrated by four Cl anions, and one lattice water molecule (Fig. 1). Atom Er1 is coordinated by eight water molecules with Er-O bond distances ranging from 2.2989 (15) to 2.3807 (15) Å. The [Er(H2O)8]3+ cations are linked to the organic cations via Cl- anions through intermolecular O-H···Cl and N-H···Cl hydrogen bonds. Each Cl- anion acts as an acceptor of hydrogen bonds from the pyridinium groups and the water molecules. The water molecules, which act as bridging units between the cations, form cooperative infinite chains parallel to the (100) plane through O-H···Cl hydrogen bonds generating centrosymmetric R24(8) ring motives (Bernstein et al., 1995), as shown in Fig. 2 and Table 1.
In the three compounds, (I) - (III), there is a decrease in the bond lengths of the metal-O(water) bonds, from 2.5101 (15) - 2.5632 (15) Å in (I), 2.404 (3) - 2.479 (4) Å in (II) and 2.2989 (15) - 2.3807 (15) Å in (III). This trend corresponds to the decreasing metallic radius of the lanthanide ion involved; La3+, Nd3+ and Er3+, respectively. In addition, the 4-(dimethylamino)pyridinium cation in the three compounds is protonated at the pyridine N atom. The N-C bond linking the dimethylamino substituent to the pyridinium ring is short, 1.321 (3), 1.324 (3)Å for (I), 1.330 (5), 1.2855 (2) Å for (II) and 1.331 (3) Å for (III), suggesting some delocalization in the cation. A search of the Cambridge Structural Database (CSD, V5.33, Update 4, August 2012; Allen, 2002) reveals similar structures incorporating the 4-(dimethylamino)pyridinium cation for which the corresponding mean N-C distance is 1.34 (1) Å. The dimethylamino group lies close to the plane of the pyridinium ring, with dihedral angles of 3.5 (3) and 2.0 (3)° for (I), 1.6 (6)° and 6.5 (3)° for (II) and 4.5 (3)° for (III).
In conclusion, on the structural level the atomic arrangement in all three compounds, (I) - (III), consists of networks of alternating organic–inorganic layers. The chloride anions are located between these entities forming hydrogen bonds with the NH atoms of the 4-(dimethylamino)pyridinium cations and the water molecules. There are also C—H···Cl interactions present involving one of the 4-(dimethylamino)pyridinium cations. The result is the formation of three-dimensional supramolecular architectures.
For similar structures in this series involving 4-(dimethylamino)pyridinium, see: Benslimane et al. (2012a,b). For details of the Cambridge Structural Database, see: Allen (2002). For hydrogen-bond motifs see: Bernstein et al. (1995).
4-(Dimethylamino)pyridine (1 mmol, 0.051g) and hydrochloric acid (1M) was added slowly to a solution of ErCl3.6H2O (1mmol, 0.08g). The mixture was refluxed at 353 K for about 1 h and then cooled to room temperature. Slow evaporation of the solvent at room temperature lead to the formation of pink plate-like crystals of the title compound.
The H-atoms of the coordinated water molecules were located in difference Fourier syntheses and were initially refined using distance restraints: O-H = 0.85 (2) Å, and H···H= 1.40 (2) Å, with Uiso(H) = 1.5Ueq(O). In the last cycles of refinement they were constrained to ride on their parent O atoms. The N-bound H atom was located in a difference Fourier map but like the C-bound H atoms it was included in calculated positions and treated as riding: N-H=0.86 Å, C-H = 0.93 (aromatic), 0.96 (methyl), with Uiso(H) = 1.5Ueq(C) for the methyl groups and 1.2Ueq(N,C) for the other H atoms.
Fig. 1. The molecular structure of the title compound, showing the atom-numbering. Displacement ellipsoids are drawn at the 50% probability level. The O-H···Cl and N-H···Cl hydrogen bonds are shown as double dashed lines.
Fig. 2. A view of part of the crystal structure of the title compound lying parallel to (100), showing the formation of rings via O-H···Cl and N-H···Cl hydrogen-bonds. Hydrogen bonds are drawn as dashed lines [symmetry codes: (i) x-1, y, z; (ii) -x+2, -y+1, -z+1; (iii) x+1, y, z].
Symmetry codes: (i) x−1, y, z; (ii) −x+2, −y+1, −z+1; (iii) x, y−1, z; (iv) x+1, y, z; (v) −x+2, −y+1, −z; (vi) −x+1, −y, −z; (vii) −x+1, −y+1, −z; (viii) −x+2, −y, −z+1.
Technical support (X-ray measurements) from Laboratory of Coordination Chemistry, UPR-CNRS 8241, Toulouse, are acknowledged.