1,2,4-Triazolyl-carboxylate-based MOFs incorporating triangular Cu(II)-hydroxo clusters: topological metamorphosis and magnetism.

Bifunctional 1,2,4-triazole-carboxylate ligands, an achiral 1,2,4-triazol-4-yl-acetic acid (trgly-H) and a chiral (d)-2-(1,2,4-triazol-4-yl)-propionic acid (d-trala-H), derived from the corresponding α-amino acid precursors revealed unique binding abilities in the construction of Cu(II)-coordination polymers composing discrete triangular [Cu3(µ3-OH)] clusters. A related series of MOFs, [Cu3(µ3-OH)(trgly)3(SO4)]·2H2O (1a), [Cu3(µ3-OH)(trgly)3(H2O)3]SO4·16H2O (1b), Cu3(µ3-OH)(d-trala)3(ClO4)0.5](ClO4)1.5·1.5H2O (2), was prepared, and their crystal structures were determined by means of X-ray diffraction. Being singly deprotonated, the organic ligands act as multidentate µ3- or µ4-donors using tr and -COO(-) moieties. The generated [Cu3(µ3-OH)(tr)3] cluster core is primarily supported by three [-N-N-] triazole heterocycles in a basal plane and tripodal-assisted µ3-anions (SO4(2-): 1a; ClO4(-): 2) capping the axial faces. The carboxylate groups join the units into either two-dimensional (2D) layer (1a, 2) or 3D zeolite-like networks (1b). Compound 1b represents the topology of α-Po (pcu: 4(12).6(3)) and crystallizes in the noncentrosymmetric space group I4̅3m, in which the six-connected [Cu3(µ3-OH)] clusters and trgly self-assemble in an open-channel cubic array possessing ∼56% solvent-accessible volume. Upon slight thermal treatment (∼60 °C), the structure irreversibly shrinks to the nonporous 2D motif 1a that belongs to a uninodal (3,6) network type. In structure 2 (space group R32), due to the [-N-N-] triazole and 1,3-bidentate carboxylate binding mode, each organic ligand bridges three metal clusters affording cross-linking of two adjacent layers with the same (3,6) topology. The resultant 3,9-c net is novel and can be categorized as two-nodal with point symbol {4(18).6(18)}{4(2).6}3. Spin frustration and antisymmetric exchange effects, resulting in abnormally low g values in the S = 1/2 states, were observed in the magnetic properties and the EPR spectra.

Functionalized adamantane tectons used in the design of mixed-ligand copper(II) 1,2,4-triazolyl/carboxylate metal-organic frameworks.

Bistriazoles, 1,3-bis(1,2,4-triazol-4-yl)propane (tr(2)pr) and 1,3-bis(1,2,4-triazol-4-yl)adamantane (tr(2)ad), were examined in combination with the rigid tetratopic 1,3,5,7-adamantanetetracarboxylic acid (H(4)-adtc) platform for the construction of neutral heteroleptic copper(II) metal-organic frameworks. Two coordination polymers, [{Cu(4)(OH)(2)(H(2)O)(2)}{Cu(4)(OH)(2)}(tr(2)pr)(2)(H-adtc)(4)]·2H(2)O (1) and [Cu(4)(OH)(2)(tr(2)ad)(2)(H-adtc)(2)(H(2)O)(2)]·3H(2)O (2), were synthesized and structurally characterized. In complexes 1 and 2, the N(1),N(2)-1,2,4-triazolyl (tr) and µ(3)-OH(-) groups serve as complementary bridges between adjacent metal centers supporting the tetranuclear dihydroxo clusters. The structure of 1 represents a unique association of two different kinds of centrosymmetrical {Cu(4)(OH)(2)} units in a tight 3D framework, while in compound 2, another configuration type of acentric tetranuclear metal clusters is organized in a layered 3,6-hexagonal motif. In both cases, the {Cu(4)(OH)(2)} secondary building block and trideprotonated carboxylate H-adtc(3-) can be viewed as covalently bound six- and three-connected nodes that define the net topology. The tr ligands, showing µ(3)- or µ(4)-binding patterns, introduce additional integrating links between the neighboring {Cu(4)(OH)(2)} fragments. A variable-temperature magnetic susceptibility study of 2 demonstrates strong antiferromagnetic intracluster coupling (J(1) = -109 cm(-1) and J(2) = -21 cm(-1)), which combines for the bulk phase with a weak antiferromagnetic intercluster interaction (zj = -2.5 cm(-1)).

Unprecedented trapping of difluorooctamolybdate anions within an α-polonium type coordination network.

New fluorinated hybrid solids [Mo2F2O5(tr2pr)] (1), [Co3(tr2pr)2(MoO4)2F2]·7H2O (2), and [Co3(H2O)2(tr2pr)3(Mo8O26F2)]·3H2O (3) (tr2pr = 1,3-bis(1,2,4-triazol-4-yl)propane) were prepared from the reaction systems consisting of Co(OAc)2/CoF2 and MoO3/(NH4)6Mo7O24, as Co(II) and Mo(VI) sources, in water (2) or in aqueous HF (1, 3) employing mild hydrothermal conditions. The tr2pr ligand serves as a conformationally flexible tetradentate donor. In complex 1, the octahedrally coordinated Mo atoms are linked in the discrete corner-sharing {Mo2(µ2-O)F2O4N4} unit in which a pair of tr-heterocycles (tr = 1,2,4-triazole) is arranged in cis-positions opposite to "molybdenyl" oxygen atoms. The anti-anti conformation type of tr2pr facilitates the tight zigzag chain packing motif. The crystal structure of the mixed-anion complex salt 2 consists of trinuclear [Co3(µ3-MoO4)2(µ2-F)2] units self-assembling in Co(II)-undulating chains (Co···Co 3.0709(15) and 3.3596(7) Å), which are cross-linked by tr2pr in layers. In 3, containing condensed oxyfluoromolybdate species, linear centrosymmetric [Co3(µ2-tr)6](6+) SBUs are organized at distances of 10.72-12.45 Å in an α-Po-like network using bitopic tr-linkers. The octahedral {N6} and {N3O3} environments of the central and peripheral cobalt atoms, respectively, are filled by triazole N atoms, water molecules, and coordinating [Mo8O26F2](6-) anions. Acting as a tetradentate O-donor, each difluorooctamolybdate anion anchors four [Co3(µ2-tr)6](6+) units through their peripheral Co-sites, which consequently leads to a novel type of a two-nodal 4,10-c net with the Schläfli symbol {3(2).4(3).5}{3(4).4(20).5(16).6(5)}. The 2D and 3D coordination networks of 2 and 3, respectively, are characterized by significant overall antiferromagnetic exchange interactions (J/k) between the Co(II) spin centers on the order of -8 and -4 K. The [Mo8O26F2](6-) anion is investigated in detail by quantum chemical calculations.

Cobalt(II) and cadmium(II) square grids supported with 4,4'-bipyrazole and accommodating 3-carboxyadamantane-1-carboxylate.

In poly[[bis(µ-4,4'-bi-1H-pyrazole-κ(2)N(2):N(2'))bis(3-carboxyadamantane-1-carboxylato-κO(1))cobalt(II)] dihydrate], {[Co(C12H15O4)2(C6H6N4)2]·2H2O}n, (I), the Co(2+) cation lies on an inversion centre and the 4,4'-bipyrazole (4,4'-bpz) ligands are also situated across centres of inversion. In its non-isomorphous cadmium analogue, {[Cd(C12H15O4)2(C6H6N4)2]·2H2O}n, (II), the Cd(2+) cation lies on a twofold axis. In both compounds, the metal cations adopt an octahedral coordination, with four pyrazole N atoms in the equatorial plane [Co-N = 2.156 (2) and 2.162 (2) Å; Cd-N = 2.298 (2) and 2.321 (2) Å] and two axial carboxylate O atoms [Co-O = 2.1547 (18) Šand Cd-O = 2.347 (2) Å]. In both structures, interligand hydrogen bonding [N...O = 2.682 (3)-2.819 (3) Å] is essential for stabilization of the MN4O2 environment with its unusually high (for bulky adamantanecarboxylates) number of coordinated N-donor co-ligands. The compounds adopt two-dimensional coordination connectivities and exist as square-grid [M(4,4'-bpz)2]n networks accommodating monodentate carboxylate ligands. The interlayer linkage is provided by hydrogen bonds from the carboxylic acid groups via the solvent water molecules [O...O = 2.565 (3) and 2.616 (3) Å] to the carboxylate groups in the next layer [O...O = 2.717 (3)-2.841 (3) Å], thereby extending the structures in the third dimension.

Cadmium(II) thio- and selenocyanate complexes of 3,3'-bis(1,2,4-triazol-4-yl)-1,1'-biadamantane, a ligand designed with an 'extended nanodiamond' aliphatic platform.

In the structures of the Cd(II) pseudohalide coordination polymer poly[[diaquabis[mu(2)-3,3'-bis(1,2,4-triazol-4-yl)-1,1'-biadamantane-kappa(2)N(1):N(1')]cadmium(II)] dithiocyanate dihydrate], {[Cd(C(24)H(32)N(6))(2)(H(2)O)(2)](NCS)(2).2H(2)O}(n), (I), and the isomorphous selenocyanate analogue, {[Cd(C(24)H(32)N(6))(2)(H(2)O)(2)](NCSe)(2).2H(2)O}(n), (II), the Cd(II) cations occupy inversion centres and have octahedral CdN(4)O(2) environments, completed by four N atoms of the organic ligands [Cd-N = 2.316 (2) and 2.361 (2) A for (I), and 2.313 (3) and 2.372 (3) A for (II)] and two trans-coordinated aqua ligands [Cd-O = 2.3189 (15) A for (I) and 2.323 (2) A for (II)]. In each compound, the ligand displays a bidentate N(1):N(1')-bridging mode, connecting the metal centres at a distance of 14.66 A into two-dimensional nets of (4,4)-topology, while the uncoordinated thio(seleno)cyanate anions reside inside the net cavities. Hydrogen bonding between the water molecules, anions and 1,2,4-triazole N atoms supports the tight packing, with an interlayer distance of 6.09 A.

1,3,5-Triphenyladamantane and 1,3,5,7-tetraphenyladamantane.

In 1,3,5-triphenyladamantane, C(28)H(28), (I), and 1,3,5,7-tetraphenyladamantane, C(34)H(32), (II), the molecules possess symmetries 3 and 4, and are situated across threefold and fourfold improper axes, respectively. The molecules aggregate by means of extensive C-H...pi interactions. In (I), the pyramidal shape of the molecules dictates the formation of dimers through a ;sixfold phenyl embrace' pattern. The dimers are linked to six close neighbors and constitute a primitive cubic net [H...pi = 2.95 (2) and 3.02 (2) A]. Compound (II) is isomorphous with tetraphenyl derivatives EPh(4) of group 14 (E = C-Pb) and ionic salts [EPh(4)][BPh(4)] (E = P, As and Sb). The multiple C-H...pi interactions arrange the molecules into chains, with a concerted action of CH (phenyl) and CH(2) (adamantane) groups as donors [H...pi = 3.15 (2) and 3.44 (2) A, respectively]. The additional interactions with the methylene groups (four per molecule) are presumably important for explaining the high melting point and insolubility of (II) compared with the EPh(4) analogs.

Hydrate frameworks involving the pyridazino[4,5-d]pyridazine unit as a multiple hydrogen-bond acceptor.

1,4,5,8-Tetramethylpyridazino[4,5-d]pyridazine trihydrate, C(10)H(12)N(4) x 3 H(2)O, (I), and 1,2,3,6,7,8-hexahydrocinnolino[5,4,3-cde]cinnoline tetrahydrate, C(12)H(12)N(4) x 4 H(2)O, (II), exhibit exceptional functionality of the condensed N(4)-heteroaromatic frame as a symmetric acceptor of four hydrogen bonds [N...O = 2.843 (2)-2.8716 (10) A]. Thus, all the N atoms of the electron-deficient and highly pi-acidic polynitrogen heterocycles function as lone-pair donors. In (I), all the molecular components lie on or across special positions; the site symmetry is 2/m for the organic and m2m and m for the two water molecules. In (II), the organic polycycle lies across a crystallographic inversion center. Both structures involve a hydrogen-bonded centrosymmetric water-pyridazine dimer as the basic supramolecular unit, which is integrated into two-dimensional [in (I)] and three-dimensional [in (II)] hydrate frameworks by hydrogen bonding with the additional water molecules [O...O = 2.744 (2)-2.8827 (19) A]. The hydrate connectivity exists in the form of an (H(2)O)(3) trimer in (I) and as a one-dimensional zigzag (H(2)O)(n) chain in (II).

Copper(II) and cadmium(II) isothiocyanate coordination polymers with 4,4'-bi-1,2,4-triazole.

The coordination polymers catena-poly[[[(4,4'-bi-1,2,4-triazole-kappaN(1))bis(thiocyanato-kappaN)copper(II)]-mu-4,4'-bi-1,2,4-triazole-kappa(2)N(1):N(1')] dihydrate], {[Cu(NCS)(2)(C(4)H(4)N(6))(2)].2H(2)O}(n), (I), and poly[tetrakis(mu-4,4'-bi-1,2,4-triazole-kappa(2)N(1):N(1'))bis(mu-thiocyanato-kappa(2)N:S)tetrakis(thiocyanato-kappaN)tricadmium(II)], [Cd(3)(NCS)(6)(C(4)H(4)N(6))(4)](n), (II), exhibit chain and two-dimensional layer structures, respectively. The differentiation of the Lewis acidic nature of Cu(II) and Cd(II) has an influence on the coordination modes of the triazole and thiocyanate ligands, leading to topologically different polymeric motifs. In (I), copper ions are linked by bitriazole N:N'-bridges into zigzag chains and the tetragonal-pyramidal CuN(5) environment is composed of two thiocyanate N atoms and three triazole N atoms [basal Cu-N = 1.9530 (18)-2.0390 (14) A and apical Cu-N = 2.2637 (15) A]. The structure of (II) contains two types of crystallographically unique Cd(II) atoms. One type lies on an inversion center in a distorted CdN(6) octahedral environment, with bitriazole ligands in the equatorial plane and terminal isothiocyanate N atoms in the axial positions. The other type lies on a general position and forms centrosymmetric binuclear [Cd(2)(mu-NCS-kappa(2)N:S)(2)(NCS)(2)] units (tetragonal-pyramidal CdN(4)S coordination). N:N'-Bridging bitriazole ligands link the Cd centers into a flat (4,4)-network.

Copper(II) bromide and copper(II) acetate complexes of 4,4'-(p-phenylene)bipyridazine.

4,4'-(p-Phenylene)bipyridazine, C(14)H(10)N(4), (I), and the coordination compounds catena-poly[[dibromidocopper(II)]-mu-4,4'-(p-phenylene)bipyridazine-kappa(2)N(2):N(2')], [CuBr(2)(C(14)H(10)N(4))](n), (II), and catena-poly[[[tetrakis(mu-acetato-kappa(2)O:O')dicopper(II)]-mu-4,4'-(p-phenylene)bipyridazine-kappa(2)N(1):N(1')] chloroform disolvate], {[Cu(2)(C(2)H(3)O(2))(4)(C(14)H(10)N(4))].2CHCl(3)}(n), (III), contain a new extended bitopic ligand. The combination of the p-phenylene spacer and the electron-deficient pyridazine rings precludes C-H...pi interactions between the lengthy aromatic molecules, which could be suited for the synthesis of open-framework coordination polymers. In (I), the molecules are situated across a center of inversion and display a set of very weak intermolecular C-H...N hydrogen bonds [3.399 (3) and 3.608 (2) A]. In (II) and (III), the ligand molecules are situated across a center of inversion and act as N(2),N(2')-bidentate [in (II)] and N(1),N(1')-bidentate [in (III)] long-distance bridges between the metal ions, leading to the formation of coordination chains [Cu-N = 2.005 (3) A in (II) and 2.199 (2) A in (III)]. In (II), the copper ion lies on a center of inversion and adopts CuN(2)Br(4) (4+2)-coordination involving two long axial Cu-Br bonds [3.2421 (4) A]. In (III), the copper ion has a tetragonal pyramidal CuO(4)N environment. The uncoordinated pyridazine N atom and two acetate O atoms provide a multiple acceptor site for accommodation of a chloroform solvent molecule by trifurcated hydrogen bonding [C-H...O(N) = 3.298 (5)-3.541 (4) A].

Mixed-anion complexes with a bipyrazolyl ligand. A new entry to a realm of three-dimensional five-connected coordination topologies.

Cross-linking of corrugated square grid coordination layers by anionic bridging groups generates five-connected coordination networks; the 3D topologies of mixed-anion cobalt(II) and nickel(II) complexes with a tetramethyl-substituted 4,4'-bipyrazolyl ligand are supported by mu-SO4(2-) functions and exist as neutral or cationic five-connected arrays involving additional terminal (NCS-) or non-coordinated (NO3-, ClO4-) groups.

Self-assembly cavitand precisely recognizing hexafluorosilicate: a concerted action of two coordination and twelve CH···F bonds.

Bis-pyridazine tectons support the structure of metallosupramolecular cavitand Cu2L4(4+), which is capable of selective encapsulation of SiF6(2-) anions by a set of multiple host-guest interactions.

1,2,4-Triazole functionalized adamantanes: a new library of polydentate tectons for designing structures of coordination polymers.

A series of functionalized adamantanes: 1,3-bis(1,2,4-triazol-4-yl)(tr(2)ad); 1,3,5-tris(1,2,4-triazol-4-yl)-(tr(3)ad); 1,3,5,7-tetrakis(1,2,4-triazol-4-yl)adamantanes (tr(4)ad) and 3,5,7-tris(1,2,4-triazol-4-yl)-1-azaadamantane (tr(3)ada) were developed as a new family of geometrically rigid polydentate tectons for supramolecular synthesis of framework solids. The coordination compounds were prepared under hydrothermal conditions; their structures reveal a special potential of the triazolyl adamantanes for the generation of highly-connected and open frameworks as well as structures based upon polynuclear metal clusters assembled with short-distance N(1),N(2)-triazole bridges. Complexes [Cd{L}(2)]A·nH(2)O [L = tr(3)ad, A = 2NO(3)(-) (4), CdCl(4)(2-) (5); L = tr(3)ada, A = CdI(4)(2-) (7)] are isomorphous and adopt a layered 3,6-connected structure of CdI(2) type. [{Cu(3)(OH)}(2)(SO(4))(5)(H(2)O)(2){tr(3)ad}(3)]·26H(2)O (6) is a layered polymer based upon Cu(3)(µ(3)-OH) nodes and trigonal tr(3)ad links. In [Cu(3)(OH)(2){tr(3)ada}(2)(H(2)O)(4)](ClO(4))(4) (8), [Cu(2){tr(3)ada}(2)(H(2)O)(3)](SO(4))(2)·7H(2)O (9) and [Cd(2){tr(3)ada}(3)]Cl(4)·28H(2)O (10) (UCl(3)-type net) the organic tripodal ligands bridge polynuclear metal clusters. Complexes [Ag{tr(4)ad}]NO(3)·3.5H(2)O (11) and [Cu{tr(4)ad}(H(2)O)](ClO(4))(2)·3H(2)O (12) have 3D SrAl(2)-type frameworks with the metal ions and adamantane tectons as topologically equivalent tetrahedral nodes, while in [Cd(3)Cl(6){tr(4)ad}(2)]·9H(2)O (13) the ligands bridge trinuclear six-connected Cd(3)Cl(6)(µ-tr)(4)(tr)(2) clusters. In the compounds [Cd(2){tr(2)ad}(4)(H(2)O)(4)](CdBr(4))(2)·2H(2)O (2) and [Cd{tr(2)ad}(4){CdI(3)}(2)]·4H(2)O (3) the bitopic ligands provide simple links between the metal ions, while in [Ag(2){tr(2)ad}(2)](NO(3))(2)·2H(2)O (1) the ligand is tetradentate and generates a 3D framework.

Facile access to a series of large polycondensed pyridazines and their utility for the supramolecular synthesis of coordination polymers.

Domino cyclization of ketoenols and hydrazine leads to a series of polycondensed pyridazines, which reveal potential as rigid N-donor multidentate ligands for supramolecular synthesis of open coordination polymers.

Self-assembly hexanuclear metallacontainer hosting halogenated guest species and sustaining structure of 3D coordination framework.

Chloride-centered hexanuclear hydroxopyrazolate reveals potential as a receptor of halomethane and halometallate species and as a molecular building block for coordination polymers.

The chiral auxiliary N-1-(1'-naphthyl)ethyl-O-tert-butylhydroxylamine: a chiral Weinreb amide equivalent.

The chiral auxiliary N-1-(1'-naphthyl)ethyl-O-tert-butylhydroxylamine is readily prepared from N-hydroxyphthalimide in four steps, with resolution giving access to both enantiomers in > 98% ee, on a multigram (> 25 g) scale. Conversion to a range of N-acyl derivatives, followed by highly diastereoselective alkylation (> or = 94% de) gives the corresponding chiral, 2-substituted derivatives as single diastereoisomers (> 98% de) after chromatography. Reductive cleavage with LiAlH(4) allows direct access to chiral aldehydes, and treatment with MeLi gives chiral methyl ketones in excellent enantiopurity (> or = 94% ee). The auxiliary can be recovered in > 98% ee and recycled.

1,2,4,5-tetrazine: an unprecedented micro4-coordination that enhances ability for anion pi interactions.

A series of framework coordination polymers reveals the use of 1,2,4,5-tetrazines as efficient bridging ligands towards silver(i) and copper(i) ions. All four nitrogen atoms were functional as lone pair donors leading to an unprecedented mu(4)-coordination of the ligands (1,2,4,5-tetrazine, ttz; 3,6-dimethyl-1,2,4,5-tetrazine, Me(2)ttz) in [Ag(ttz)(X)] (X = NO(3), ; ClO(4), ), [Ag(2)(Me(2)ttz)(NO(3))(2)] (), [Ag(2)(Me(2)ttz)(H(2)O)(2)(ClO(4))(2)] (), [Ag(3)(Me(2)ttz)(H(2)O)(2)(CF(3)SO(3))(3)] () and [Cu(4)Cl(4)(Me(2)ttz)] (). In and , micro(4)-tetrazines and silver ions (AgN(4), Ag-N 2.42-2.53 A) compose a 3D framework of {4(2);8(4)} topology. Structures and were based on disilver-tetrazine ribbons, while in mu(4)-tetrazines interconnect silver-triflate chains. In , micro(4)-ligands connect inorganic layers sustained by copper-chloride squares, hexa- and octagons (1.974(2) and 1.981(2) A). Multiple N-coordination to metal ions enhances the ability of the electron deficient tetrazine system for anionpi binding. Compounds and exhibit very short interactions of this type with corresponding OC(N) separations down to a record value of 2.78 A and Opi 2.61 A. For , pi-acidity of tetrazine was reflected by contacts Clpi of 3.30 A. Results of high level ab initio calculations (RI-MP2/aug-cc-pVTZ) were in good agreement with experimental results, and were suggestive of the progressive enhancement of the pi-acidity by increasing the number of Ag(i) ions N-coordinated to tetrazine.

Diaquabis[4-(4H-1,2,4-triazol-4-yl)benzoato-kappa2O,O']cobalt(II), and the cadmium(II) and copper(II) analogues: new self-complementary hydrogen-bond donor/acceptor modules for designing hydrogen-bonded frameworks.

In the isostructural title complexes, [M(C(9)H(6)N(3)O(2))(2)(H(2)O)(2)] [M = Co(II), (I), Cd(II), (II), and Cu(II), (III); the metal centres reside on a twofold axis in the space group C2/c for (I) and (II)], the metal centres are surrounded by four O atoms from two O,O'-bidentate carboxylate groups and by two trans-coordinated aqua ligands, forming a distorted octahedral environment. The molecules possess four hydrogen-bond donor (two aqua ligands) and four hydrogen-bond acceptor sites (two triazole groups), and aggregate by self-association, forming two-dimensional hydrogen-bonded frameworks [via O-H...N interactions; O...N = 2.749 (3)-2.872 (3) A]. The layers are parallel and are tightly packed with short interlayer distances of 4.93, 4.95 and 5.01 A for (I), (II) and (III), respectively.

Silver(I) sulfate coordination polymers with 4,4'-bipyridazine and pyridazino[4,5-d]pyridazine.

Poly[[micro(4)-4,4'-bipyridazine-micro(5)-sulfato-disilver(I)] monohydrate], [[Ag(2)(SO(4))(C(8)H(6)N(4))].H(2)O](n), (I), and poly[[aqua-micro(4)-pyridazino[4,5-d]pyridazine-micro(3)-sulfato-disilver(I)] monohydrate], [[Ag(2)(SO(4))(C(6)H(4)N(4))(H(2)O)].H(2)O](n), (II), possess three- and two-dimensional polymeric structures, respectively, supported by N-tetradentate coordination of the organic ligands [Ag-N = 2.208 (3)-2.384 (3) A] and O-pentadentate coordination of the sulfate anions [Ag-O = 2.284 (3)-2.700 (2) A]. Compound (I) is the first structurally examined complex of the new ligand 4,4'-bipyridazine; it is based upon unprecedented centrosymmetric silver-pyridazine tetramers with tetrahedral AgN(2)O(2) and trigonal-bipyramidal AgN(2)O(3) coordination of two independent Ag(I) ions. Compound (II) adopts a typical dimeric silver-pyridazine motif incorporating two kinds of square-pyramidal AgN(2)O(3) Ag(I) ions. The structure exhibits short anion-pi interactions involving noncoordinated sulfate O atoms [O...pi = 3.041 (3) A].