Crystal structure of bis(μ2-4-carboxy-2-sulfonatobenzoato)- bis[aqua(2,2′-bipyridyl)copper(II)] hexahydrate, [Cu(H2O)(C10H8N2)(C8H4O7S)]2 · 6H2O

C36H40Cu2N4O22S2, triclinic, P1 (no. 2), a = 9.391(2) Å, b = 10.559(2) Å, c = 11.335(2) Å, 0 = 99.893(3)°, = 100.774(3)°, , = 92.560(3)°, V = 1084.3 Å, Z = 1, Rgt(F) = 0.042, wRref(F) = 0.118, T = 298 K. Source of material A mixture of STP (2-sulfoterephthalic acid, 0.025 g, 0.1 mmol), CuCl2 (0.013 g, 0.1 mmol), 2,2'-bipy (0.016 g, 0.1 mmol), and H2O (10 ml) was stirred for about 30 min. The resulting solution was sealed in a Teflon-lined stainless autoclave and heated to 393 K for 3 days. The bottle was cooled to ambient temperature spontaneously. Blue block-like single crystals (about 90 %, based on Cu) were recovered by vacuum filtration and drying in air. Elemental analysis — found: C, 32.76 %; H, 4.16 %; N, 5.83 %; calulated for C36H40Cu2N4O22S2: C, 32.84 %; H, 4.24 %; N, 5.90 %. Experimental details The C-bound H atoms were geometrically placed (d(C—H) = 0.93 Å) and refined as riding with Uiso(H) = 1.2 Ueq(C). The Obound H atoms were located in difference maps and refined as riding with Uiso(H) = 1.2Ueq(O). Discussion Terephthalate is an important rigid multicaboxylate ligand for construction of extended coordination solids owing to its high symmetry and coordination ability for a broad range of metal ions [1-5]. Introduction of a sulfonate group into rigid multicarboxlate ligands may result in the formation of unexpected frameworks as the sulfonic group has a different shape and properties in terms of its coordination ability compared to the carboxylate group. Since a pseudo-honeycomb coordination polymer constructed by copper(II) and the 5-sulfo-isophthalic acid as ligand was firstly reported [6], the studies of this ligand have received considerable attention [7-15]. However, the studies of the 2-sulfoterephthalic acid (H3STP) are not very common [16-19]. The asymmetric unit in the title structure contains one copper ion, one 2,2'-bipyridine molecule, one deprotonated HSTP anion and four water molecules. The copper center is surrounded with two pyridine N atoms of a 2,2'-bipyridine molecule, one carboxylate O atom, one water molecule, and one sulfonate O atom. One carboxylate O atom, one coordinated water molecule and two 2,2'-bipyridine N atoms form the basal plane, and the sulfonate O atom occupies the apical site. The copper coordination is thus the square pyramidal one. The Cu—N and Cu—Obasal bond lengths range from 1.9538(2) 1.993(2) Å, which is consistent with those found in comparable structures [7,14]. The Cu—Osulfonate bond distance is much longer than that of Cu—Ocarboxylate which is the most frequent with copper sulfonates. The C—O distances are consistent with the location of the H atoms deduced from difference maps, which indicate that the HSTP ligand carries a charge of $2 for charge balance. The HSTP anion coordinates to the symmetry-related copper ions through its sulfonate O atom and carboxylate O atom. The whole HSTP ligand links metal centres in a %2 mode to generate a dimeric unit forming short bridges, which define a 14-membered ring. As found in the previous complex [16], the dihedral angle between aromatic ring and the plane of the carboxylate group is 78.54°, which is made possible by the well matched ionic size. The terminal COOH group does not participate in the coordinat ion of copper . In comparable crystal s t ructure of [Mn(bipy)(H2O)(STP)]2 [16], the sulfonate O atom and cis carboxylate O atom coordinating to the Mn centre form a sevenmembered chelate ring. The carboxylate group acts as a bismonodentate ligand toward two metal centres. In the manganese compound the HSTP ligand adopts a %2 mode forming long bridges that link metal centres generating a dimeric unit with a 16memebered ring. Z. Kristallogr. NCS 224 (2009) 73-75 / DOI 10.1524/ncrs.2009. 0030 73 © by Oldenbourg Wissenschaftsverlag, München