1,15-Diferrocenyl-2,5,8,11,14-pentaazapentadecane,an Open-Chain Redox-Active Ferrocene-Functionalized Polyazaalkane Ligand for Anions

The interaction of the ferrocene-functionalized open-chain polyazaalkane 1,15-diferrocenyl-2,5,8,11,14-pentaazapentadecane (L¹) with the sulfate, phosphate, and ATP anions has been studied by potentiometric methods in THF/H₂O 70 : 30 (v/v) (containing 0.1M (Bu₄N)ClO₄ at 25°). Additionally, the electrochemical response of L¹ in the presence of H⁺, HSO^-₄, H₂PO^-₄, Br⁻, and Cl⁻ in a non-aqueous solvent such as MeCN has been studied. A remarkable cathodic shift of the ferrocene oxidation potential was induced for phosphate (198 mV) and sulfate (145 mV) showing an EC mechanistic response. Competitive electrochemical studies showed that L¹ is able to electrochemically and selectively recognize HSO^-₄ vs. H₂PO^-₄ in a mixture of both anions in MeCN.     

Coordination Centres of Purine Nucleotides: Adenosine‐5′‐diphosphate and Adenosine‐5′‐triphosphate in their Reactions with Nickel(II), Cobalt(II) and Tetramines

Interactions between the nucleotides: adenosine‐5′‐diphosphate (ADP) and adenosine‐5′‐triphosphate (ATP) with Ni^II and Co^II ions, as well as with spermine (Spm) and 1,11‐diamine‐4,8‐diazaundecane (3,3,3‐tet) are the subject of this study. Composition and stability constants of mixed complexes thus formed have been determined on the basis of the potentiometric measurements, whereas interaction centres in ligands have been identified by VIS and NMR spectral parameter analysis. Mixed tetraprotonated complexes with Ni^II, i.e. Ni(ADP)H₄(Spm), Ni(ATP)H₄(Spm), Ni(ADP)H₄(3,3,3‐tet) and Ni(ATP)H₄(333‐tet), are identified as ML·······L′ type adducts, in which the main coordination centre is the nucleotide nitrogen N(1) or N(7) donor atom, and the fully protonated polyamine is engaged in noncovalent interactions with nucleotide phosphate group oxygen atoms. Ni(ADP)H₂(Spm), Ni(ATP)H₂(Spm), Ni(ADP)H₂(3,3,3‐tet) and Ni(ATP)H₂(3,3,3‐tet) complexes represent the {N3} coordination type In diprotonated mixed complexes of Ni^II with spermine are weak noncovalent interligand interactions, providing an additional stabilising effect. Formation of ML·······L′ type molecular complexes has been observed in systems with Co^II: Co(ADP)H₄(Spm), Co(ATP)H₄(Spm), Co(ADP)H₄(3,3,3‐tet) and Co(ATP)H₄(3,3,3‐tet), in which the N(7) atom and oxygen atoms of the phosphate group are involved in coordination and the fully protonated polyamine is engaged in noncovalent interactions with the nucleotide N(1).     

Influence of Decreasing Solvent Polarity (1,4‐Dioxane/Water Mixtures) on the Acid–Base and Copper(II)‐Binding Properties of Guanosine 5′‐Diphosphate

The acidity constants of twofold protonated guanosine 5′‐diphosphate, H₂(GDP)^?, and the stability constants of the [Cu(H;GDP)] and [Cu(GDP)]^? complexes were determined in H₂O as well as in 30 or 50% (v/v) 1,4‐dioxane/H₂O by potentiometric pH titrations (25°; I=0.1M , NaNO₃). The results showed that in H₂O one of the two protons of H₂(GDP)^? is located mainly at the N(7) site and the other one at the terminal β‐phosphate group. In contrast, for 50% 1,4‐dioxane/H₂O solutions, a micro acidity‐constant evaluation evidenced that ca. 75% of the H₂(GDP)^? species have both protons phosphate‐bound, because the basicity of pyridine‐type N sites decreases with decreasing solvent polarity whereas the one of phosphate groups increases. In the [Cu(H;GDP)] complex, the proton and the metal ion are in all three solvents overwhelmingly phosphate‐bound, and the release of this proton is inhibited by decreasing polarity of the solvent. Based on previously determined straight‐line plots of log K vs. pK (where R represents a non‐interacting residue in simple diphosphate monoesters ROP(O^?)(?O)? O? P(?O)(O^?)₂, R? DP^3?), which were now extended to mixed solvents (based on analogies), it is concluded that, in all three solvents, the [Cu(GDP)]^? complex is more stable than expected based on the basicity of the diphosphate residue. This increased stability is attributed to macrochelate formation of the phosphate‐coordinated Cu²⁺ with N(7) of the guanine residue. The formation degree of this macrochelate amounts in aqueous solution to ca. 75% (being thus higher than that of the Cu²⁺ complex of adenosine 5′‐diphosphate) and in 50% (v/v) 1,4‐dioxane/H₂O to ca. 60%, i.e., the formation degree of the macrochelate is only relatively little affected by the change in solvent, though it needs to be emphasized that the overall stability of the [Cu(GDP)]^? complex increases with decreasing solvent polarity. By including previously studied systems in the considerations, the biological implications are shortly discussed, and it is concluded that Nature has here a tool to alter the structure of complexes by shifting them on a protein surface from a polar to an apolar region and vice versa.     

Poly[diaquabis(μ‐4,4′‐bipyridine‐κ2N:N′)bis(ethane‐1,2‐diol)di‐μ‐sulfato‐dicopper(II)]

The title compound, [Cu₂(SO₄)₂(C₁₀H₈N₂)₂(C₂H₆O₂)₂(H₂O)₂]_n, contains two crystallographically unique Cu^II centres, each lying on a twofold axis and having a slightly distorted octahedral environment. One Cu^II centre is coordinated by two bridging 4,4′‐bipyridine (4,4′‐bipy) ligands, two sulfate anions and two aqua ligands. The second is surrounded by two 4,4′‐bipy N atoms and four O atoms, two from bridging sulfate anions and two from ethane‐1,2‐diol ligands. The sulfate anion bridges adjacent Cu^II centres, leading to the formation of linear ...Cu1–Cu2–Cu1–Cu2... chains. Adjacent chains are further bridged by 4,4′‐bipy ligands, which are also located on the twofold axis, resulting in a two‐dimensional layered polymer. In the crystal structure, extensive O—H...O hydrogen‐bonding interactions between water molecules, ethane‐1,2‐diol molecules and sulfate anions lead to the formation of a three‐dimensional supramolecular network structure.     

Water‐induced pseudo‐quadruple hydrogen‐bonding motifs in xanthine–inorganic acid complexes

In xanthinium nitrate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium nitrate monohydrate], C₅H₅N₄O₂⁺·NO₃⁻·H₂O, (I), and xanthinium hydrogen sulfate hydrate [systematic name: 2,6‐dioxo‐1,2,3,6‐tetrahydro‐9H‐purin‐7‐ium hydrogen sulfate monohydrate], C₅H₅N₄O₂⁺·HSO₄⁻·H₂O, (II), the xanthine molecules are protonated at the imine N atom with the transfer of an H atom from the inorganic acid. The asymmetric unit of (I) contains a xanthinium cation, a nitrate anion and one water molecule, while that of (II) contains two crystallographically independent xanthinium cations, two hydrogen sulfate anions and two water molecules. A pseudo‐quadruple hydrogen‐bonding motif is formed between the xanthinium cations and the water molecules via N—H...O and O—H...O hydrogen bonds in both structures, and leads to the formation of one‐dimensional polymeric tapes. These cation–water tapes are further connected by the respective anions and aggregate into two‐dimensional hydrogen‐bonded sheets in (I) and three‐dimensional arrangements in (II).     

Hydrogen‐bonded sheets in 2‐(2‐aminophenyl)‐1H‐benzimidazol‐3‐ium dihydrogen phosphate

The title salt, C₁₃H₁₂N₃⁺·H₂PO₄⁻, contains a nonplanar 2‐(2‐aminophenyl)‐1H‐benzimidazol‐3‐ium cation and two different dihydrogen phosphate anions, both situated on twofold rotation axes in the space group C2. The anions are linked by O—H...O hydrogen bonds into chains of R₂²(8) rings. The anion chains are linked by the cations, via hydrogen‐bonding complementarities and electrostatic interactions, giving rise to a sheet structure with alternating rows of organic cations and inorganic anions. Comparison of this structure with that of the pure amine reveals that the two compounds generate characteristically different sheet structures. The anion–anion chain serves as a template for the assembly of the cations, suggesting a possible application in the design of solid‐state materials.     

Hydro­gen‐bonding patterns in 2‐amino‐4,6‐di­methyl­pyrimidinium hydrogen sulfate

In the title compound, C₆H₁₀N₃⁺·HSO₄⁻, the asymmetric unit consists of a hydrogen sulfate anion and a 2‐amino‐4,6‐di­methyl­pyrimidinium cation. The hydrogen sulfate anions self‐assemble through O—H⋯O hydrogen bonds, forming supramolecular chains along the b axis, while the organic cations form base pairs via N—H⋯N hydrogen bonds. The amino­pyrimidinium cations join to the sulfate anions via a pair of hydrogen bonds donated from the pyrimidinium protonation site and from the exo amine group cis to the protonated site.     

Salt effects in the aqueous alkaline hydrolysis of N-hydroxyphthalimide. Kinetic evidence for the ion-pair formation

The effects of the concentrations of LiCl, NaCl, KCl, CsCl, Na₂CO₃, BaCl₂, and Me₄NCl on the rates of reactions of hydroxide ion with ionized N-hydroxyphthalimide (NHP) at 30°C and in a H₂O–MeCN solvent containing 98%, v/v, H₂O reveal a nonlinear increase in observed rate constants with increase in salt concentrations. The observed rate constants are highly sensitive to the valence state of cations and almost insensitive to the valence state of anions of the salts. These observations are explained in terms of ion-pair formation between cations and NHP^?.     

Supramolecular architectures in cytosinium 6‐chloronicotinate monohydrate and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6‐chloronicotinate monohydrate, C₄H₆N₃O⁺·C₆H₃ClNO₂⁻·H₂O, ( I ), and 5‐bromo‐6‐methylisocytosinium hydrogen sulfate (or 2‐amino‐5‐bromo‐4‐oxo‐6‐methylpyrimidinium hydrogen sulfate), C₅H₇BrN₃O⁺·HSO₄⁻, ( II ), have been prepared and characterized by single‐crystal X‐ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt ( I ), the primary R₂²(8) ring motif (supramolecular heterosynthon) is formed via a pair of N—H…O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N—H…O, N—H…N, O—H…O and C—H…O hydrogen bonds, forming R₂²(8), R₃²(7) and R₅⁵(21) motifs, leading to a hydrogen‐bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water–carboxylate O—H…O hydrogen bonds and π–π interactions between the anions and the cations. In salt ( II ), the hydrogen sulfate ions are linked via O—H…O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N—H…O hydrogen bonds and vice versa, generating two R₂²(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen–halogen (Br…Br) and halogen–oxygen (Br…O) interactions.     

A dihydrogen phosphate anionic network as a host lattice for cations in 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate) and 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1)

In the salt 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate), C₅H₁₃N₂²⁺·2H₂PO₄⁻, (I), and the solvated salt 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1), C₁₀H₉N₂⁺·H₂PO₄⁻·H₃PO₄, (II), the formation of O—H...O and N—H...O hydrogen bonds between the dihydrogen phosphate (H₂PO₄⁻) anions and the cations constructs a three‐ and two‐dimensional anionic–cationic network, respectively. In (I), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional pseudo‐honeycomb‐like supramolecular architecture along the (010) plane. 1‐Methylpiperazine‐1,4‐diium cations are trapped between the (010) anionic layers through three N—H...O hydrogen bonds. In solvated salt (II), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional supramolecular architecture with open channels projecting along the [001] direction. The 2‐(pyridin‐2‐yl)pyridinium cations are trapped between the open channels by N—H...O and C—H...O hydrogen bonds. From a study of previously reported structures, dihydrogen phosphate anions show a supramolecular flexibility depending on the nature of the cations. The dihydrogen phosphate anion may be suitable for the design of the host lattice for host–guest supramolecular systems.     

A 2D Metal‐Organic Framework Based on 9‐(Pyridin‐4‐yl)‐9H‐carbazole‐3,6‐dicarboxylic Acid: Synthesis,Structure and Properties

A metal‐organic framework (MOF ) formulated as [Cd₂(μ₃‐L)₂(DMF )₄]•H₂O ( CdL ) [H₂L =9‐(pyridin‐4‐yl)‐ 9H ‐carbazole‐3,6‐dicarboxylic acid, DMF =N ,N ‐dimethylformamide] was synthesized under solvothermal condition. Crystal structural analysis reveals that CdL features the layered 2D framework with L^{2 −} ligands as 3‐connected nodes. The compound CdL emits blue‐violet light with the narrow emission peak and the emission maximum at 414 nm upon excitation at the maximum excitation wavelength of 340 nm. The compound CdL has a similar emission spectrum curve to the free H₂L ligand that indicates the emission of compound CdL should be originated from the coordinated L^{2 −} ligands.     

Radiofluorination of a Pre‐formed Gallium(III) Aza‐macrocyclic Complex: Towards Next‐Generation Positron Emission Tomography (PET) Imaging Agents

As part of a study to investigate the factors influencing the development of new, more effective metal‐complex‐based positron emission tomography (PET) imaging agents, the distorted octahedral complex, [GaCl(L)]?2 H₂O has been prepared by reaction of 1‐benzyl‐1,4,7‐triazacyclononane‐4,7‐dicarboxylic acid hydrochloride (H₂L?HCl) with Ga(NO₃)₃?9 H₂O, which is a convenient source of Ga^III for reactions in water. Spectroscopic and crystallographic data for [GaCl(L)]?2 H₂O are described, together with the crystal structure of [GaCl(L)]?MeCN. Fluorination of this complex by Cl^?/F^? exchange was achieved in high yield by treatment with KF in water at room temperature over 90 minutes, although the reaction was complete in approximately 30 minutes if heated to 80 °C, giving [GaF(L)]?2 H₂O in good yield. The same complex was obtained by hydrothermal synthesis from GaF₃?3 H₂O and Li₂L, and has been characterised by single‐crystal X‐ray analysis, IR, ¹H and ¹⁹F{¹H} NMR spectroscopy and ESI⁺ MS. Radiofluorination of the pre‐formed [GaCl(L)]?2 H₂O has been demonstrated on a 210 nanomolar scale in aqueous NaOAc at pH 4 by using carrier‐free ¹⁸F^?, leading to 60–70 % ¹⁸F‐incorporation after heating to 80 °C for 30 minutes. The resulting radioproduct was purified easily by using a solid‐phase extraction (SPE) cartridge, leading to 98–99 % radiochemical purity. The [Ga¹⁸F(L)] is stable for at least 90 minutes in 10 % EtOH/NaOAc solution at pH 6, but defluorinates over this time scale at pH of approximately 7.5 in phosphate buffered saline (PBS) or human serum albumin (HSA). The subtle role of the Group 13 metal ion and co‐ligand donor set in influencing the pH dependence of this system is discussed in the context of developing potential new imaging agents for PET.     

A novel alkaline earth strontium(II) coordination polymer: poly[hexaaquatetrakis(μ5‐pyridine‐2,6‐dicarboxylato)bis(μ4‐pyridine‐2,6‐dicarboxylato)(μ7‐sulfato)heptastrontium(II)]

The title compound, [Sr₇(C₇H₃NO₄)₆(SO₄)(H₂O)₆]_n, has been synthesized by an ionothermal method using the ionic liquid 1‐ethyl‐3‐methylimidazolium ([Emim]Br) as solvent, and characterized by elemental analysis, energy‐dispersive X‐ray spectroscopy, IR and single‐crystal X‐ray diffraction. The structure of the compound can be viewed as a three‐dimensional coordination polymer composed of Sr²⁺ cations, pyridine‐2,6‐dicarboxylate anions, sulfate anions and water molecules. The compound not only exhibits a three‐dimensional structure with a unique coordination mode of the sulfate anion, but also features the first example of a heptanuclear strontium(II) coordination polymer. The structure is further stabilized by O—H...O hydrogen bonds and π–π stacking interactions.     

3′:5′‐Cyclic nucleotides: two sodium salts of cdTMP

3′:5′‐Cyclic nucleotides play an outstanding role in signal transduction at the cellular level but, in spite of comprehensive knowledge of the biological role of cyclic nucleotides, their structures are not established fully. Two hydrated sodium salts of thymidine 3′:5′‐cyclic phosphate (cdTMP, C₁₀H₁₂N₂O₇P), namely sodium thymidine 3′:5′‐cyclic phosphate heptahydrate, Na⁺·C₁₀H₁₂N₂O₇P⁻·7H₂O or Na(cdTMP)·7H₂O, (I), and sodium thymidine 3′:5′‐cyclic phosphate 3.7‐hydrate, Na⁺·C₁₀H₁₂N₂O₇P⁻·3.7H₂O or Na(cdTMP)·3.7H₂O, (II), have been obtained in crystalline form and structurally characterized, revealing one nucleotide in the asymmetric unit of (I) and eight different nucleotides in (II). All the cyclic nucleotide anions adopt a similar conformation with regard to nucleobase orientation, sugar conformation and 1,3,2‐dioxaphosphorinane ring puckering. In (I), no direct inter‐nucleotide hydrogen bonds are present, and adjacent nucleotide anions interact via water‐mediated and Na⁺‐mediated contacts. In contrast, in (II), direct thymine–phosphate N—H...O inter‐nucleotide hydrogen bonds occur and these are assisted by numerous inter‐nucleotide C—H...O contacts, giving rise to the self‐assembly of cdTMP⁻ anions into three different ribbons. Two of these three ribbons run in the same direction, while the third is antiparallel.     

Three‐dimensional hydrogen‐bonded framework in bis(melamin‐1‐ium) naphthalene‐1,5‐disulfonate melamine pentahydrate

Crystals of the title compound, 2C₃H₇N₆⁺·C₁₀H₆O₆S₂²⁻·C₃H₆N₆·5H₂O, are built up of neutral 2,4,6‐triamino‐1,3,5‐triazine (melamine), singly protonated melaminium cations, naphthalene‐1,5‐disulfonate dianions and water molecules. Two independent anions lie across centres of inversion in the space group P. The melamine molecules are connected by N—H...N hydrogen bonds into two different one‐dimensional polymers almost parallel to the (010) plane, forming a stacking structure along the b axis. The centrosymmetric naphthalene‐1,5‐disulfonate anions interact with water molecules via O—H...O hydrogen bonds, forming layers parallel to the (001) plane. The cations and anions are connected by N—H...O and O—H...N hydrogen bonds to form a three‐dimensional supramolecular framework.     

1‐Carboxymethyl‐3‐methyl‐1H‐imidazol‐3‐ium chloride 2‐(3‐methyl‐1H‐imidazol‐3‐ium‐1‐yl)acetate monohydrate: a crystal stabilized by imidazolium zwitterions

The title compound, C₆H₉N₂O₂⁺·Cl⁻·C₆H₈N₂O₂·H₂O, contains one 2‐(3‐methyl‐1H‐imidazol‐3‐ium‐1‐yl)acetate inner salt molecule, one 1‐carboxymethyl‐3‐methyl‐1H‐imidazol‐3‐ium cation, one chloride ion and one water molecule. In the extended structure, chloride anions and water molecules are linked via O—H...Cl hydrogen bonds, forming an infinite one‐dimensional chain. The chloride anions are also linked by two weak C—H...Cl interactions to neighbouring methylene groups and imidazole rings. Two imidazolium moieties form a homoconjugated cation through a strong and asymmetric O—H...O hydrogen bond of 2.472 (2) Å. The IR spectrum shows a continuous D‐type absorption in the region below 1300 cm⁻¹ and is different to that of 1‐carboxymethyl‐3‐methylimidazolium chloride [Xuan, Wang & Xue (2012). Spectrochim. Acta Part A, 96 , 436–443].     

Syntheses,Structures, and Photophysical Properties of Two Coordination Polymers Based on 2,3‐Dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic Acid

Two complexes based on the ligand 1,4‐dihydro‐2,3‐quinoxalinedione, namely [Mn(H₂L)₂(H₂O)₂]_n ( 1 ) and {[Zn₂(H₂L)₂(tz)₂] · 5H₂O}_n ( 2 ) (H₃L = 2,3‐dioxo‐1,2,3,4‐tetrahydroquinoxaline‐6‐carboxylic acid, Htz = 1,2,4‐triazole) were hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, as well as single‐crystal and powder X‐ray diffraction. Complex 1 exhibited a 1D comb‐like chain formed by H₂L^– anions linking Mn^II ions, whereas complex 2 was a 2D layer‐like structure with square‐shaped windows and outstretched arms built by combination of H₂L^– and tz^– ligands with Zn^II ions. The adjacent chains or layers connected with each other by intermolecular hydrogen bonding and π–π stacking to further extend to a 3D supermolecular framework. In addition, the thermal stabilities, luminescence properties, and optical energy gap of 1 and 2 were investigated in detail.     

A three‐dimensional zinc‐based coordination polymer built from 5‐carboxylato‐1‐carboxylatomethyl‐2‐oxidopyridinium with a 4‐connected sra topology

A novel three‐dimensional Zn^II complex, poly[aqua(μ₄‐5‐carboxylato‐1‐carboxylatomethyl‐2‐oxidopyridinium)zinc(II)], [Zn(C₈H₅NO₄)(H₂O)]_n, has been prepared by hydrothermal assembly of Zn(CH₃COO)₂·2H₂O and 5‐carboxy‐1‐(carboxymethyl)pyridin‐1‐ium‐2‐olate (H₂ccop). The ccop²⁻ anions bridge the Zn^II cations in a head‐to‐tail fashion via monodentate aromatic carboxylate and phenolate O atoms to form an extended zigzag chain which runs parallel to the [011] direction. One O atom of the aliphatic carboxylate group of the ccop²⁻ ligand coordinates to the Zn^II atom of a neighbouring chain thereby producing undulating layers which lie parallel to the (01) plane. A similar parallel undulating planar structure can be obtained if a path involving the other O atom of the aliphatic carboxylate group is considered. Thus, the aliphatic carboxylate group acts in a bridging bidentate mode to give extended –Zn–O–C–O–Zn– sequences running parallel to [001] which link the layers into an overall three‐dimensional framework. The three‐dimensional framework can be simplified as a 4‐connected sra topology with a Schläfli symbol of 4².6³.8 if all the Zn^II centres and ccop²⁻ anions are regarded as tetrahedral 4‐connected nodes. The three‐dimensional luminescence spectrum was measured at room temperature with excitation and emission wavelengths of 344–354 and 360–630 nm, respectively, at intervals of 0.15 and 2 nm, respectively.     

Luminescent properties of three structures built from 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate and cadmium

Yellow–orange tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) dihydrate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·2H₂O, (I), and yellow tetraaquabis(3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κN³)cadmium(II) 1,4‐dioxane solvate, [Cd(C₈HN₄O₂)₂(H₂O)₄]·C₄H₈O₂, (II), contain centrosymmetric mononuclear Cd²⁺ coordination complex molecules in different conformations. Dark‐red poly[[decaaquabis(μ₂‐3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olato‐κ²N:N′)bis(μ₂‐3‐cyano‐4‐dicyanomethylene‐1H‐pyrrole‐2,5‐diolato‐κ²N:N′)tricadmium] hemihydrate], [Cd₃(C₈HN₄O₂)₂(C₈N₄O₂)₂(H₂O)₁₀]·0.5H₂O, (III), has a polymeric two‐dimensional structure, the building block of which includes two cadmium cations (one of them located on an inversion centre), and both singly and doubly charged anions. The cathodoluminescence spectra of the crystals are different and cover the wavelength range from UV to red, with emission peaks at 377 and 620 nm for (III), and at 583 and 580 nm for (I) and (II), respectively.     

Tetraaqua(4,4′‐dimethyl‐2,2′‐bipyridine‐κ2N,N′)nickel(II) sulfate monohydrate: a simple molecule with an extremely complex hydrogen‐bonding scheme

The title ionic compound, [Ni(C₁₂H₁₂N₂)(H₂O)₄]SO₄·H₂O, is composed of an Ni^II cation coordinated by a chelating 4,4′‐dimethyl‐2,2′‐bipyridine ligand via its two N atoms [mean Ni—N = 2.056 (2) Å] and by four aqua ligands [mean Ni—O = 2.073 (9) Å], the net charge being balanced by an external sulfate anion. The whole structure is stabilized by a solvent water molecule. Even though the individual constituents are rather featureless, they generate an extremely complex supramolecular structure consisting of a central hydrogen‐bonded two‐dimensional hydrophilic nucleus made up of complex cations, sulfate anions and coordinated and solvent water molecules, with pendant hydrophobic 4,4′‐dimethyl‐2,2′‐bipyridine ligands which interact laterally with their neighbours viaπ–π interactions. The structure is compared with closely related analogues in the literature.