Crystal structure of 4,4'-(disulfanediyl)dibutanoic acid-4,4'-bipyridine (1/1).

4,4'-(Disulfanediyl)dibutanoic acid (dtba) and 4,4'-bipyridine (4,4'-bpy) crystallize in an 1:1 ratio, leading to the title co-crystal with composition C8H14O4S2·C10H8N2. A distinctive feature of the crystal structure is the geometry of the dtba moiety, which appears to be stretched [with a 9.98 (1) Šspan between outermost carbons] and acts as an hydrogen-bonding connector, forming linear chains along [-211] with the 4,4'-bpy moiety by way of O-H⋯N hydrogen bonds and C-H⋯O interactions. The influence of the mol-ecular shape on the hydrogen-bonding pattern is analysed by comparing the title compound and two other 4,4'-bpy co-crystals with closely related mol-ecules of similar formulation but different geometry, showing the way in which this correlates with the packing arrangement.

Crystal structure of zwitterionic 4-(ammonio-methyl)-benzoate: a simple mol-ecule giving rise to a complex supra-molecular structure.

The asymmetric unit of the title compound, C8H9NO2·H2O consists of an isolated 4-(ammonio-meth-yl)benzoate zwitterion derived from 4-amino-methyl-benzoic acid through the migration of the acidic proton, together with a water molecule of crystallization that is disordered over three sites with occupancy ratios (0.50:0.35:0.15). In the crystal structure, N-H⋯O hydrogen bonds together with π-π stacking of the benzene rings [centroid-centroid distance = 3.8602 (18) Å] result in a strongly linked, compact three-dimensional structure.

A dense hydrogen-bonding network and an unusually large packing index in triaquatris(2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylato)neodymium(III) trihydrate.

The title mononuclear complex, [Nd(C5H3N2O3)3(H2O)3]·3H2O, consists of an Nd(III) cation, three 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate ligands and three aqua ligands forming the neutral complex molecule, and three solvent water molecules. The pyrimidinecarboxylate ligands act in a chelating manner, via carboxylate and keto O atoms. The NdO9 coordination polyhedron is in the form of a distorted monocapped square antiprism. The availability of numerous hydrogen-bonding donors and acceptors results in a very dense hydrogen-bonding network, the immediate effect of which is an unusually large packing index.

A polymeric cobalt(II) complex derived from citric acid (H4cit) and 2,6-diaminopurine (dap): {[Co4(cit)2(dap)4(H2O)4]·6.35H2O}n.

Poly[[tetraaquadi-µ4-citrato-tetrakis(2,6-diaminopurine)tetracobalt(II)] 6.35-hydrate], {[Co4(C6H4O7)2(C5H6N6)4(H2O)4]·6.35H2O}n, presents three different types of Co(II) cations in the asymmetric unit, two of them lying on symmetry elements (one on an inversion centre and the other on a twofold axis). The main fragment is further composed of one fully deprotonated citrate (cit) tetraanion, two 2,6-diaminopurine (dap) molecules and two aqua ligands. The structure is completed by a mixture of fully occupied and disordered solvent water molecules. The two independent dap ligands are neutral and the cit tetraanion provides for charge balance, compensating the 4+ cationic charge. There are two well defined coordination geometries in the structure. The simplest is mononuclear, with the Co(II) cation arranged in a regular centrosymmetric octahedral array, coordinated by two aqua ligands, two dap ligands and two O atoms from the ß-carboxylate groups of the bridging cit tetraanions. The second, more complex, group is trinuclear, bisected by a twofold axis, with the metal centres coordinated by two cit tetraanions through their α- and ß-carboxylate and α-hydroxy groups, and by two dap ligands bridging through one of their pyridine and one of their imidazole N atoms. The resulting coordination geometry around each metal centre is distorted octahedral. Both groups are linked alternately to each other, defining parallel chains along [201], laterally interleaved and well connected via hydrogen bonding to form a strongly coupled three-dimensional network. The compound presents a novel µ4-κ(5)O:O,O':O',O'',O''':O'''' mode of coordination of the cit tetraanion.

Poly[[diaquabis(µ2-crotonato-κ3O:O,O')(crotonato-κ2O,O')lanthanum(III)] adenine monosolvate monohydrate].

The asymmetric unit of the title compound, {[La(C(4)H(5)O(2))(3)(H(2)O)(2)]·C(5)H(5)N(5)·H(2)O}(n), consists of an La(III) cation, three crotonate (but-2-enoate) anions and two coordinated water molecules forming the neutral complex, completed by an external adenine molecule and one hydration water molecule. The LaO(10) coordination polyhedra, connected through the sharing of a single edge, form isolated chains running along the [100] direction. These one-dimensional structures are characterized by two different centrosymmetric La(2)O(2) loops, with La...La distances of 4.5394 (6) and 4.5036 (6) Å. The unbound adenine and water solvent molecules form a highly planar hydrogen-bonded array parallel to (110) (r.m.s. deviation from the mean plane < 0.10 Å) which intersects the isolated La-crotonate chains in a slanted fashion to form an extremely connected hydrogen-bonded three-dimensional structure.

Two isomorphous lanthanide crotonate complexes: di-µ-but-2-enoato-bis[diaquabis(but-2-enoato)dysprosium(III)] adenine monosolvate heptahydrate and the samarium(II) analogue.

The asymmetric unit of the title dimeric compounds, [Ln(2)(C(4)H(5)O(2))(6)(H(2)O)(4)]·C(5)H(5)N(5)·7H(2)O, with Ln = Dy, (I), and Sm, (II), consists of an Ln(III) cation, three crotonate (but-2-enoate) anions and two coordinated water molecules forming the neutral complex, cocrystallized with half of an external adenine molecule and 3.5 water molecules. The metal complex has crystallographic inversion symmetry. The LnO(9) coordination polyhedra are connected through the sharing of a single edge to form isolated dimeric units, with Ln...Ln separations of 4.1766 (12) Å for (I) and 4.2340 (12) Å for (II). The unbound adenine molecule and one of the solvent water molecules are disordered around an inversion centre into two overlapping, equally populated, units. The structure is sustained by a complex hydrogen-bonding scheme involving all possible O-H and N-H groups as donors, and crotonate and water O and adenine N atoms as acceptors. The system is compared with recently published related compounds.

Isoquinolin-5-amine.

The title compound, C(9)H(8)N(2), presents two almost identical independent molecules in the asymmetric unit, both of them exhibiting an extremely planar isoquinoline core (maximum r.m.s. deviation = 0.014 Å). The most significant deviation is found in the -NH(2) groups, which present a noticeable pyramidalization around the N atom, a feature also present in related structures containing the molecule as a ligand. The supramolecular structure is based on pairs of parallel hydrogen-bonded chains formed by just one molecular type each, defined by the strongest hydrogen bonds in the structure, which are of the N-H···N type. These parallel chains are linked into pairs (or strips) via weaker C-H···N hydrogen bonds. Related strips generated by the c-glide plane define two families running along [110] and [110], giving rise to an interesting system of interwoven chains stabilized by a number of weaker contacts of the C-H···π type.

Bis(2-amino-1H-benzimidazol-3-ium) tetrakis(µ-but-2-enoato)-κ4O:O';κ3O,O':O;κ3O:O,O'-bis[bis(but-2-enoato-κ2O,O')holmium(III)].

The title ionic compound, (C(7)H(8)N(3))(2)[Ho(2)(C(4)H(5)O(2))(8)], is constructed from two almost identical independent centrosymmetric anionic dimers balanced by two independent 2-amino-1H-benzimidazol-3-ium (Habim(+)) cations. The asymmetric part of each dimer is made up of one Ho(III) cation and four crotonate (crot or but-2-enoate) anions, two of them acting in a simple η(2)-chelating mode and the remaining two acting in two different µ(2):η(2) fashions, viz. purely bridging and bridging-chelating. Symmetry-related Ho(III) cations are linked by two Ho-O-Ho and two Ho-O-C-O-Ho bridges which lead to rather short intracationic Ho···Ho distances [3.8418 (3) and 3.8246 (3) Å]. In addition to the obvious Coulombic interactions linking the cations and anions, the isolated [Ho(2)(crot)(8)](2-) and Habim(+) ions are linked by a number of N-H···O hydrogen bonds, in which all N-H groups of the cation are involved as donors and all (simple chelating) crot O atoms are involved as acceptors. These interactions result in compact two-dimensional structures parallel to (110), which are linked to each other by weaker π-π contacts between Habim(+) benzene groups.

Tetraaquabis(2,6-diamine-7H-purine-κN9)cobalt(II) benzene-1,2,4,5-tetracarboxylate tetrahydrate.

The title compound, [Co(C(5)H(7)N(6))(2)(H(2)O)(4)](C(10)H(2)O(8))·4H(2)O, is an ionic structure comprising a [Co(Hdap)(2)(H(2)O)(4)](4+) cation (dap is 2,6-diaminopurine) in a general position, two benzene-1,2,4,5-tetracarboxylate (btc(4-)) anions straddling two different inversion centres and four solvent water molecules. The structure presents a remarkable degree of pseudosymmetry, with the Co(II) cation lying almost exactly on a noncrystallographic pseudo-inversion centre. The overall spatial arrangement can be described in terms of cationic and anionic chains running along the [111] direction and linked into a three-dimensional network by a very complex hydrogen-bonding scheme in which all the available N-H and O-H groups take part.

Poly[[µ3-2-(carboxylatomethyl)benzoato-κ3O1:O2:O2]bis(1H-imidazole-κN3)copper(II)].

In the title polymeric compound, [Cu(C(9)H(6)O(4))(C(3)H(4)N(2))(2)](n), the copper(II) cation occupies an N(2)O(3) coordination sphere defined by two 1H-imidazole (imid) ligands in trans positions and three carboxylate O atoms from three different 2-(carboxylatomethyl)benzoate (hpt(2-)) dianions. The geometry is that of a square pyramid with one of the O atoms at the apex, bridging neighbouring metal centres into an [-ON(2)CuO(2)CuN(2)O-] dinuclear unit. These units are in turn connected by hpt anions into a reticular mesh topologically characterized by two types of loops, viz. a four-membered Cu(2)O(2) diamond motif and a 32-membered Cu(4)O(8)C(20) ring. The imid groups do not take part in the formation of the two-dimensional structure, but take part in the N-H···O interactions. These arise only within individual planes, interplanar interactions being only of the van der Waals type.

Poly[4,4'-(propane-1,3-diyl)dipyridinium bis{tetraaquabis(µ2-5-carboxybenzene-1,2,4-tricarboxylato)bis[µ2-1,3-bis(4-pyridyl)propane]dicobalt(II)} pentahydrate].

The title polymeric compound, {(C(13)H(16)N(2))[Co(C(10)H(3)O(8))(C(13)H(14)N(2))(H(2)O)(2)](2)·5H(2)O}(n), is an ionic structure comprising an anionic two-dimensional mesh characterized by a {[Co(Hbtc)(bpp)(H(2)O)(2)](-)}(2) motif [Hbtc is 5-carboxybenzene-1,2,4-tricarboxylate and bpp is 1,3-bis(4-pyridyl)propane], with interspersed 4,4'-(propane-1,3-diyl)dipyridinium cations, denoted (H(2)bpp)(2+), and water molecules providing the charge balance and structure stabilization. The reticular mesh consists of two independent types of [Co(H(2)O)(2)](2+) cationic nodes (lying on inversion centres), interconnected in the [101] direction by two independent sets of neutral bridging bpp ligands, both types of ligands being split by non-equivalent twofold axes. One set is formed by genuinely symmetric moieties, while those in the second set are only symmetric by disorder in the central propane bridge. These chains contain only one type of Co(II) centre and one type of bpp ligand; the metal cations therein are laterally bridged by Hbtc anions, thus forming transverse chains of alternating types of Co(II) cations. The elemental motif of the resulting grid is a highly distorted parallelogram, with metal-metal distances of 13.5242 (14) Å in the bpp direction and 9.105 (2) Å in the Hbtc direction, and a large internal angle of 138.42 (18)°. These two-dimensional structures have a profusion of hydrogen-bonding interactions with each other, either directly (with the aqua molecules as donors and the Hbtc anions as acceptors) or mediated by the unbound (H(2)bpp)(2+) cations and water molecules of hydration. These interactions generate a very complex hydrogen-bonding scheme involving all of the available N-H and O-H groups and which links these two-dimensional grids into a three-dimensional network.

Bis(2,6-diamino-1H-purin-3-ium) di-µ-croconato-κ3O,O':O'';κ3O:O',O''-bis[tetraaqua(croconato-κ2O,O')neodymium(III)].

The structure of the ionic title compound, (C(5)H(7)N(6))(2)[Nd(2)(C(5)O(5))(4)(H(2)O)(8)], consists of anionic dimers built around an inversion centre and is made up of an Nd(III) cation, two croconate (croco) dianions and four water molecules (plus their inversion images), with two noncoordinated symmetry-related 2,6-diamino-1H-purin-3-ium (Hdap(+)) cations providing charge balance. Each Nd(III) atom is bound to nine O atoms from four water and three croco units. The coordination polyhedron has the form of a rather regular monocapped square antiprism. The croconate anions are regular and the Hdap(+) cation presents a unique, thus far unreported, protonation state. The abundance of hydrogen-bonding donors and acceptors gives rise to a complex packing scheme consisting of dimers interlinked along the three crystallographic directions and defining anionic `cages' where the unbound Hdap(+) cations lodge, linking to the mainframe via (N-H)(Hdap)···O(water/croco) and (O-H)(water)···N(Hdap) interactions.

Two isomorphous transition metal complexes containing a protonated diaminopurine ligand: diaquabis(2,6-diamino-7H-purin-1-ium-κN9)bis(homophthalato-κO)nickel(II) tetrahydrate and the cobalt(II) analogue.

The two isomorphous title compounds, [M(C(5)H(7)N(6))(2)(C(9)H(6)O(4))(2)(H(2)O)(2)]·4H(2)O or M(2+)(Hdap(+))(2)(hpt(2-))(2)(H(2)O)(2)·4H(2)O {where dap is 2,6-diaminopurine, H(2)hpt is homophthalic acid [2-(2-carboxyphenyl)acetic acid] and M is Ni(II) or Co(II)}, consist of neutral M(2+)(Hdap(+))(2)(hpt(2-))(2)(H(2)O)(2) monomers, where the M(II) cation lies on an inversion centre and its MN(2)O(4) octahedral environment is defined by one N atom (from Hdap(+)), two O atoms (from one hpt(2-) dianion and one water molecule) and their inversion images. The structures are unusual in that the Hdap(+) cation occurs in an uncommon protonated state (as 2,6-diamino-7H-purin-1-ium) and both ligands bind in an unprecedented monodentate fashion. The existence of a large number of donors and acceptors for hydrogen bonding, together with π-π interactions, leads to a rather complex three-dimensional structure.

Di-µ-but-2-enoato-bis-[diaqua-bis(but-2-enoato)neodymium(III)] 2,6-diamino-purine disolvate.

The title Nd complex [Nd(2)(C(4)H(5)O(2))(6)(H(2)O)(4)]·2C(5)H(6)N(6) is isotypic with two previously reported Dy and Ho isologues. It is composed of [Nd(crot)(3)(H(2)O)(2)](2) dimers [crot(onate) = but-2-enoate = C(4)H(5)O(2)], built up around symmetry centres and completed by 2,6-diamine-purine mol-ecules acting as solvates. The neodymium cations are coordinated by three chelating crotonato units and two water mol-ecules. One of the chelating carboxyl-ates acts also in a bridging mode, sharing one oxygen with both cations, and the final result is a pair of NdO(9) tricapped prismatic polyhedra linked to each other through a central (Nd-O)(2) loop. A most attractive aspect of the structures resides in the existence of a complex inter-molecular hydrogen-bonding interaction scheme involving two sets of tightly inter-linked, non-inter-secting one-dimensional structures, one of them formed by the [Nd(crot)(3)(H(2)O)(2)](2) dimers running along [100] and the second by the solvate mol-ecules evolving along [010].

2,6-Diamino-9H-purine monohydrate and bis(2,6-diamino-9H-purin-1-ium) 2-(2-carboxylatophenyl)acetate heptahydrate: two simple structures with very complex hydrogen-bonding schemes.

Two structures presenting an uncomplexed 2,6-diaminopurine (dap) group are reported, namely 2,6-diamino-9H-purine monohydrate, C(5)H(6)N(6)·H(2)O, (I), and bis(2,6-diamino-9H-purin-1-ium) 2-(2-carboxylatophenyl)acetate heptahydrate, 2C(5)H(7)N(6)(+)·C(9)H(6)O(4)(2-)·7H(2)O, (II). Both structures are rather featureless from a molecular point of view, but present instead an outstanding hydrogen-bonding scheme. In compound (I), this is achieved through a rather simple independent unit content (one neutral dap and one water molecule) and takes the form of two-dimensional layers tightly connected by strong hydrogen bonds, and interlinked by much weaker hydrogen bonds and π-π interactions. In compound (II), the fundamental building blocks are more complex, consisting of two independent 2,6-diamino-9H-purin-1-ium (Hdap(+)) cations, one homophthalate [2-(2-carboxylatophenyl)acetate] dianion and seven solvent water molecules. The large number of hydrogen-bond donors and acceptors produces 26 independent interactions, leading to an extended and complicated network of hydrogen bonds in a packing organization characterized by the stacking of interleaved anionic and cationic planar arrays. These structural characteristics are compared with those of similar compounds in the literature.

Two isomorphous crotonatolanthanide complexes: tetra-mu-but-2-enoato-bis[diaqua(but-2-enoato)Ln]-2,6-diaminopurine (1/2) (Ln = Dy and Ho).

The title isomorphous compounds, tetra-mu-but-2-enoato-bis[diaqua(but-2-enoato)dysprosium(III)]-2,6-diaminopurine (1/2), [Dy(2)(C(4)H(5)O(2))(6)(H(2)O)(4)].2C(5)H(6)N(6), and tetra-mu-but-2-enoato-bis[diaqua(but-2-enoato)holmium(III)]-2,6-diaminopurine (1/2), [Ho(2)(C(4)H(5)O(2))(6)(H(2)O)(4)].2C(5)H(6)N(6), consist of [Ln(crot)(3)(H(2)O)(2)](2) dimers (crot is crotonate or but-2-enoate; Ln is the lanthanide cation), built up around inversion centres and completed by 2,6-diaminopurine molecules. The lanthanide cation is coordinated by three chelating crotonate units and two water molecules. One of the chelating carboxylate groups acts also in a bridging mode sharing one O atom with both cations and the final result is a pair of DyO(9) tricapped prismatic polyhedra linked to each other through a central (Dy-O)(2) loop. A feature of the structures is the existence of a complex intermolecular interaction scheme involving two sets of tightly interlinked non-intersecting one-dimensional structures, one of them formed by the [Dy(crot)(3)(H(2)O)(2)](2) dimers (running along [100] and linked by O-H...O hydrogen bonds) and the second formed by 2,6-diaminopurine molecules (evolving along [010] linked by N-H...N hydrogen bonds).

Two isomorphous cobalt(II) complexes: poly[[diaqua-mu-2,5-dicarboxybenzene-1,4-dicarboxylato-mu-1,2-di-4-pyridylethene-cobalt(II)] 1,2-di-4-pyridylethene solvate] and the 1,2-di-4-pyridylethane analogue.

The two isomorphous title structures, formulated as {[Co(C(10)H(4)O(8))(C(12)H(10)N(2))(H(2)O)(2)].C(12)H(10)N(2)}(n), (I), and {[Co(C(10)H(4)O(8))(C(12)H(12)N(2))(H(2)O)(2)].C(12)H(12)N(2)}(n), (II), respectively, are reported. They crystallize in the space group P\overline{1} with only one formula unit in the asymmetric unit, so that the organic ligands lie about inversion centres and the Co atom lies on an inversion centre. The Co atoms are octahedrally coordinated by a carboxylate O atom from 2,5-dicarboxybenzene-1,4-dicarboxylate (H(2)btc), one N atom from 1,2-di-4-pyridylethene (L) in (I) or from 1,2-di-4-pyridylethane (L) in (II), and one coordinated water molecule, plus their inversion-related species. This particular coordination results in a two-dimensional array, with an elemental unit in the shape of a parallelogram having the Co(II) cations at the corners, linked in one direction by L bridges and in the opposite direction by H(2)btc groups. The L solvent molecules act as pillars between parallel planes, linking them by strong hydrogen bonds where the H atoms lie midway between the formal donor/acceptor atoms in a ;shared' mode. Comparison is made with structures presenting the same structural motif, strongly suggesting that the two-dimensional arrangement reported here might be a very stable robust building block for molecular engineering purposes.

Three lanthanide complexes derived from itaconic acid and 2,2'-bipyridine.

The structures of three new polymeric lanthanide complexes, poly[[bis(2,2'-bipyridine)-mu(4)-itaconato-di-mu(3)-itaconato-digadolinium(III)] tetrahydrate], {[Gd(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(2)].4H(2)O}(n), (I), poly[diaqua(2,2'-bipyridine)di-mu(3)-itaconato-mu(2)-itaconato-digadolinium(III)], [Gd(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(H(2)O)(2)](n), (II), and poly[[bis(2,2'-bipyridine)-mu(4)-itaconato-di-mu(3)-itaconato-diholmium(III)] dihydrate], {[Ho(2)(C(5)H(4)O(4))(3)(C(10)H(8)N(2))(2)].2H(2)O}(n), (III), have been solved from twinned specimens. Compound (I) presents a two-dimensional polymeric structure parallel to (011) built up around two independent nine-coordinated Gd centres displaying similar GdO(7)N(2) environments, with both N-donor atoms in each provided by a chelating 2,2'-bipyridine (bpy) unit. The coordinating O atoms are from three different itaconate (ita) anions (itaconic acid is 2-methylidenebutanedioic acid). Compound (II) also presents two independent Gd centres (one ten- and the other eight-coordinated), but the overall formula and individual coordinations are different from those of (I). The chemical unit is in this case completed by one bpy ligand, three ita anions (one of them displaying a new, hitherto unreported, mu(3)-O,O':O',O'':O''' binding mode) and two aqua ligands. The whole structure is built up around a twofold rotation axis passing through both cations, as well as through the centre of the bpy ligand and one of the ita anions, thus making only half of the chemical unit independent. Finally, compound (III) presents a single independent Ho centre, a bpy unit and one and a half ita anions (one of them bisected by a twofold rotation axis) in the asymmetric unit, plus two (disordered) nonbonded solvent water molecules. In compounds (II) and (III), those ita anions bisected by a symmetry element incompatible with the internal symmetry of the ligand exhibit disorder in the C=CH(2) group.

Two polymeric structures with a benzene-1,2,4,5-tetracarboxylate ligand acting in mu2- and mu4-bridging modes.

catena-Poly[[tetraaquabis(1H-pyrazole-kappaN(2))nickel(II)] [[diaquabis(1H-pyrazole-kappaN(2))nickel(II)]-mu-benzene-1,2,4,5-tetracarboxylato-kappa(2)O(1):O(4)] tetrahydrate], {[Ni(C(3)H(4)N(2))(2)(H(2)O)(4)][Ni(C(10)H(2)O(8))(C(3)H(4)N(2))(2)(H(2)O)(2)].4H(2)O}(n), (I), and poly[[(mu(4)-benzene-1,2,4,5-tetracarboxylato-kappa(4)O(1):O(2):O(4):O(5))octakis(1H-pyrazole-kappaN(2))dicobalt(II)] tetrahydrate], {[Co(2)(C(10)H(2)O(8))(C(3)H(4)N(2))(8)].4H(2)O}(n), (II), are polymeric compounds crystallizing in the space group P1, with two independent metallic cations and one benzene-1,2,4,5-tetracarboxylate (btc) anion, each lying on symmetry centres. Individual coordination polyhedra are regular and the main differences are in the way the btc anion binds [mu(2) in (I) and mu(4) in (II)], promoting a 'chain-like' one-dimensional structure in (I) and a 'sieve-like' two-dimensional motif in (II).

Two polymeric nickel(II) complexes with aromatic benzene-1,2,4,5-tetracarboxylate and pyridine-2,5-dicarboxylate linkers.

(Mu-benzene-1,2,4,5-tetracarboxylato-kappa(2)O(1):O(4))bis[aquabis(2,2-methylpropane-1,3-diamine-kappa(2)N,N')nickel(II)] methanol disolvate tetrahydrate, [Ni(2)(C(10)H(2)O(8))(C(5)H(14)N(2))(4)(H(2)O)(2)].2CH(4)O.4H(2)O, (I), is dinuclear, with elemental units built up around an inversion centre halving the benzene-1,2,4,5-tetracarboxylate (btc) anion, which bridges two symmetry-related Ni(II) cations. The octahedral Ni polyhedron is completed by two chelating 2,2-methylpropane-1,3-diamine (dmpda) groups and a terminal aqua ligand. Two methanol and four water solvent molecules are involved in a number of N-H...O and O-H...O hydrogen bonds which define a strongly bound two-dimensional supramolecular structure. The structure of catena-poly[[[bis(2,2-methylpropane-1,3-diamine-kappa(2)N,N')nickel(II)]-mu-pyridine-2,5-dicarboxylato-kappa(3)O(5):N,O(2)-[(2,2-methylpropane-1,3-diamine-kappa(2)N,N')nickel(II)]-mu-pyridine-2,5-dicarboxylato-kappa(3)N,O(2):O(5)] octahydrate], {[Ni(2)(C(7)H(3)NO(4))(2)(C(5)H(14)N(2))(3)].8H(2)O}(n), (II), is polymeric, forming twisted chains around three independent Ni centres, two of which lie on inversion centres and the third in a general position. There are three chelating dmpda ligands (one disordered over two equally populated positions), which are each attached to a different cation, and two pyridine-2,5-dicarboxylate (pdc) anions, both chelating the Ni centre in general positions through an -O-C-C-N- loop, while acting as bridges to the remaining two centrosymmetric Ni atoms. There are, in addition, eight noncoordinated water molecules in the structure, some of which are disordered.