supplementary materials

Li^I ion forms with pyridazine-3,6-dicarboxylate and water ligands a complex composed of centrosymmetric monomers in which the metal ion is chelated by two singly deprotonated ligand molecules and two water O atoms giving rise to octahedral coordination with aqua O atoms at the axial positions. A proton located between adjacent aqua O atoms, apart from maintaining charge balance, bridges the monomers via strong centrosymmetric hydrogen bonds to form catenated ribbons (Starosta & Leciejewicz, 2010). It has been of interest to study structural changes brought about by removal of the bridging protons. Hydrazine has been selected as the deprotonating agent. The structure of a complex obtained when the amount of added hydrazine was very small is described in this report.

The title compound is a polymeric complex with four symmetry independent Li ions in the asymmetric unit. Two of them show distorted trigonal bipyramidal geometry, the other two exhibit distorted tetrahedral coordination environment. The asymmetric unit contains also two pyridazine-3,6-dicarboxylate ligand molecules (PY1 with atoms labels starting with 1 and PY2 with atoms labels starting with 2), three coordinated water molecules and a solvation water molecule (Fig.1). The equatorial plane of the Li1 coordination polyhedron is composed of atoms O11, N21, O24ⁱ. The Li1 ion is 0.0285 (2) Å out of the plane, atoms O21 and N11 are at axial positions. Li2 ion is shifted by 0.0186 (2) Å from the basal plane composed of atoms O12ⁱⁱ, O23, N12; atoms O13 and N22 make the apices. Li3 ion is coordinated by atoms O21, O22ⁱⁱⁱ, O31, O42ⁱⁱ at the apices of a distorted tetrahedron while the coordination tetrahedron of the Li4 ion is composed of atoms O13^iv, O14, O41, O42 [Symmetry codes: ⁱ -x + 2, -y, -z + 2; ⁱⁱ -x + 2, -y + 1, -z + 2; ⁱⁱⁱ -x + 2, -y, -z + 3; ^iv -x + 2, -y + 1, -z + 1]. The Li—O and Li—N bond distances are close to those observed in the other Li complex with the title ligand (Starosta & Leciejewicz, 2010). Both pyridazine rings are planar with r.m.s. deviation of 0.0154 (2)Å and 0.0123 (2)Å for the ring PY1 and PY2, respectively. Carboxylate groups C17/O11/O12 and C18/O13/O14 make with the hetero-ring PY1 dihedral angles of 14.3 (1)° and 22.2 (2)°, respectively. Dihedral angles formed with the hetero-ring PY2 by carboxylate groups C27/O21/O22 and C28/O23/O24 amount to 3.8 (1)° and 17.2 (2)°, respectively. The Li1 and Li2 ions bridged by hetero-ring N atoms donated by both ligands along the Li1—N11—N12—Li2—N22—N21—Li1 pathway form a dimeric moiety. The C27/O21/O22 and C27ⁱⁱⁱ/O21ⁱⁱⁱ/O22ⁱⁱⁱ groups act as bidentate bridge between the Li3 and Li3ⁱⁱⁱ ions to form a loop which joins two dimers via O21 and O21ⁱⁱⁱ atoms since the latter are also bonded to the Li1 and Li1ⁱⁱⁱ ions, respectively. A similar loop bridges the dimers from the other side as the bidentate O13 atom links the Li2 and Li4^iv ions. A molecular ribbon propagating along the c direction can be visualized (Fig. 2). The ribbons bridged by carboxylate and coordinated water O atoms form molecular layers which are parallel to the bc plane and stacked along the a axis direction. The bridging of ribbons proceeds via carboxylato O12 and O24 atoms: atom O12 is coordinated to the Li2ⁱⁱ atom in an adjacent ribbon, while the Li2 ion by the O12ⁱⁱ atom from the same adjacent ribbon. The O24 atom is chelated to the Li1ⁱ ion in the other adjacent ribbon, while the O24ⁱ atom is coordinated to the Li1 ion. In addition, pairs of ribbons are bridged by coordinated aqua O42 atoms via Li4—O42—Li3ⁱⁱ and Li3—O42ⁱⁱ—Li4ⁱⁱ links. An extended system of hydrogen bonds in which coordinated water molecules are donors and carboxylato O atoms in adjacent layers act as acceptors, maintains the stability of the structure (Table 1). Two intra-molecular hydrogen bonds are also observed.