Crystal structures of two erbium(III) complexes with 4-amino­benzoic acid and 4-chloro-3-nitro­benzoic acid

The crystal structures of two erbium(III) complexes with 4-amino­benzoic acid (4-ABAH), namely bis­(μ(2)-4-amino­benzoato-κ(2) O:O′)bis­[bis(4-amino­benzoato-κ(2) O,O′)di­aqua­erbium(III)] dihydrate, [Er(2)(C(7)H(6)NO(2))(6)(H(2)O)(4)]·2H(2)O, (I), and 4-chloro-3-nitro­benzoic acid (CLNBAH), namely poly[hexa­kis­(μ(2)-4-chloro-3-nitro­benzoato-κ(2) O:O′)bis­(dimethyl sulfoxide-κO)dierbium(III)], [Er(2)(C(7)H(3)ClNO(4))(6)(C(2)H(6)OS)(2)](n), (II), have been determined. In the structure of solvatomorphic compound (I), the symmetry-related irregular ErO(8) coordination polyhedra in the discrete centrosymmetric dinuclear complex comprise two monodentate water mol­ecules and six carboxyl­ate O-atom donors, four from two bidentate carboxyl­ate O,O′-chelate groups and two from the bis-monodentate O:O′-bridging group of the third 4-ABA anion. The Er—O bond-length range is 2.232 (3)–2.478 (3) Å and the Er⋯Er separation in the dinuclear complex unit is 4.7527 (4) Å. One of the coordinating water mol­ecules is involved in an intra-unit O—H⋯O hydrogen-bonding association with an inversion-related carboxyl­ate O-atom acceptor. In contrast, the anhydrous compound (II) is polymeric, based on centrosymmetric dinuclear repeat units comprising ErO(7) coordination polyhedra which involve four O-atom donors from two bidentate O:O′-bridging carboxyl­ate groups, one O-atom donor from the monodentate dimethyl sulfoxide ligand and two O-atom donors from the third bridging CLNBA anion. The latter provides the inter-unit link in the one-dimensional coordination polymer extending along [100]. The Er—O bond-length range in (II) is 2.239 (6)–2.348 (6) Å and the Er⋯Er separation within the dinuclear unit is 4.4620 (6) Å. In the crystal of (I), extensive inter-dimer O—H⋯O and N—H⋯O hydrogen-bonding inter­actions involving both the coordinating water mol­ecules and the solvent water mol­ecules, as well as the amine groups of the 4-ABA anions, give an overall three-dimensional network structure. Within this structure are also weak π–π ring inter­actions between two of the coordinating ligands [ring-centroid separations = 3.676 (3) and 3.711 (2) Å]. With (II), only weak intra-polymer C—H⋯O, C—H⋯Cl and C—H⋯S inter­actions are present.