Bipyridinium Cation Research Articles

Extent of protonation of 4,4′-bipyridinium cations and nature of host influences the amount of guest intake by cobalt(II) 2,6-pyridinedicarboxylate

4,4′-Bipyridinium cobalt(II) 2,6-pyridinedicarboxylate hexahydrate forms host–guest complexes with hydroxy-aromatic compounds 2,3- or 2,7-dihydroxynaphthalene and phloroglucinol. Impressive aspect of the complex is the modification of protonated species in different ways while forming host–guest complexes with hydroxyaromatics. Complex with 2,3-dihydroxynaphthalene has 4,4′-bipyridinium monocation and dication as counter-ions, whereas 2,7-dihydroxynaphthalene complex has only 4,4′-bipyridinium dication. Host-guest complex with phloroglucinol has two 4,4′-bipyridinium monocations. Guest dependent templates are formed in each case. In the case of 2,3-dihydroxynaphthalene, interactions among amine-water-naphthalenediol resulted in chain-like structures within the self-assembly; whereas host–guest complex having 2,7-dihydroxynaphthalene holds water clusters within self-assembly. Substrate dependent host–guest complexes with variations on amounts of guest intake per unit cell was observed; for example with 1, 3, 5-trihydroxybenzene as guest molar ratio of cobalt ion with respect to guest is unity, whereas three equivalents of 2, 3- or 2, 7-dihydroxynaphthalene molecules per cobalt complex were observed.

An Organic Receptor Isolated in an Unusual Intermediate Conformation: Computation, Crystallography, and Hirshfeld Surface Analysis.

1,1″-1,4-Phenylene-bis(methylene)bis-4,4'-bipyridinium cation [C28H24N4]2+ (c), an organic receptor that generally crystallizes in its anti conformation, has recently been shown to be isolated in its syn conformation in an ion-paired compound [C28H24N4][Zn(dmit)2]·2DMF (dmit2- = 1,3-dithiole-2-thione-4,5-dithiolate; DMF = dimethylformamide). In this article, we demonstrated that the same receptor [C28H24N4]2+ (c) can also be stabilized in an unusual intermediate conformation (neither syn nor anti) with PF6- anion in compound [C28H24N4](PF6)2·(1,4-dioxane) (1·(1,4-dioxane)). The energetically favored anti conformation has been described in its nitrate salt [C28H24N4](NO3)2·2H2O (2·2H2O). Compounds 1·(1,4-dioxane) and 2·2H2O, crystallizing in triclinic and monoclinic systems with space groups P1̅ and P21/n, respectively, were additionally characterized by Hirshfeld surface analysis. The density functional theory calculations are performed to understand the internal mechanism of the stability of various conformers of cationic receptor c, compound 1, and compound 2. In conjunction with the electronic stability of the conformers, the natural bond orbital analysis and conformational equilibrium constants at different temperatures are also calculated to find out the sources of the different stability of the various conformers of experimentally synthesized compounds.

Inclusion of dihydroxyaromatics by a lanthanum(III) 2,6-dipicolinate complex

Lanthanum complexes possessing dihydroxyaromatic guests namely, (H2bpy)1.5[La(26pdc)3]·2(cat)·4H2O, (H2bpy)3[La(26pdc)3]2·3(23dhn)·19H2O, (H2bpy)1.5 [La(26pdc)3]·3(27dhn)·10H2O [26pdc=2,6-pyridinedicarboxylate, bpy=4,4′-bipyridine, cat=1,2-dihydroxybenzene, 23dhn=2,3-dihydroxynaphthalene, 27dhn=2,7-dihydroxynaphthalene] are synthesized from 4,4′-bipyridinium lanthanum(III) tris-pyridinedicarboxylate and structurally characterized. Two different types of templates to accommodate hosts are found in these host–guest complexes. 1,2-Dihydroxybenzene molecules are held by template formed by interactions of a [tris-2,6-dipicolinate lanthanum(III)] anion with a 4,4′-bipyridinium cation; whereas dihydroxynaphthalene molecules are held by templates formed between two complex anions interacting with one 4,4′-bipyridinium cation. Complexes 1 and 2 without guest molecules are fluorescent in solid state; whereas dihydroxyaromatic guest included complexes 3–5 are non-fluorescent in solid state. However, in solution, complex 1 causes increase in fluorescence emission intensity of 1,2-hydroxyaromatic compounds and recognition of 1,2-dihydroxybenzene by complex 1 is significant.

Direct observation of light-driven, concerted electron–proton transfer

The phenols 4-methylphenol, 4-methoxyphenol, and N-acetyl-tyrosine form hydrogen-bonded adducts with N-methyl-4, 4'-bipyridinium cation (MQ+) in aqueous solution as evidenced by the appearance of low-energy, low-absorptivity features in UV-visible spectra. They are assigned to the known examples of optically induced, concerted electron-proton transfer, photoEPT. The results of ultrafast transient absorption measurements on the assembly MeOPhO-H---MQ+ are consistent with concerted EPT by the instantaneous appearance of spectral features for MeOPhO·---H-MQ+ in the transient spectra at the first observation time of 0.1 ps. The transient decays to MeOPhO-H---MQ+ in 2.5 ps, accompanied by the appearance of oscillations in the decay traces with a period of ∼1 ps, consistent with a vibrational coherence and relaxation from a higher υ(N-H) vibrational level or levels on the timescale for back EPT.

Effects of alkyl chain length on film morphologies and photocurrent responses of tetrathiafulvalene-bipyridinium charge-transfer salts: a study in terms of structures

Viologen dication derivatives with a series of alkyl chains are used to assemble charge-transfer salts and films with dimethylthio-tetrathiafulvalene-bicarboxylate which aims to explore the relationship of the alkyl chain length to molecular structures and film morphologies which are important points for the design of molecular materials and manipulation of molecular devices. Four charge-transfer salts generally formulated as [(CnV)(HL)2] [n = 4(1), 8(2), 12(3) and 16(4)] are prepared and 1–3 are characterized by single-crystal X-ray structural analysis. In the short alkyl chain compound, TTF and C4V moieties are regularly arranged and effectively stacked with strong charge-transfer interactions. Lengthening the alkyl chain of the bipyridinium cation reduces the regular and close arrangement of the cations and anions in the crystals, which weakens the charge-transfer interaction while increasing the amphiphilic assembly of the films. Their film morphologies change from crystals to fused crystals, band-like structures and finally to smooth films with the increase of the alkyl chain length. The effects of alkyl chain length on photocurrent intensity are different between the crystal sample-modified electrodes (in the order of 1 > 2 > 3 = 4) and the film-modified electrodes (in the order of 2 > 1 = 3 > 4), because both inter-ion interactions and film-forming properties should be considered for the film electrodes. This is a systematic study of the effect of alkyl chain substitution on film morphologies in terms of crystal structures.

Effect of conjugated structures of bipyridinium cations on ion assembly and charge-transfer of their tetrathiafulvalene-bicarboxylate salts

A series of tetrathiafulvalene (electron donor, D) charge-transfer salts with three methyl bipyridiniums (electron acceptor, A) in the basic formulas MV(HL)2 (1), MeBpe(HL)2 (2) and MeBpa(HL)2 (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, MV = methyl viologen, MeBpe = 1,2-bi(4-pyridinium) ethene and MeBpa =1,2-bi(4-pyridinium) ethane) was synthesized and their structures were characterized by X-ray single crystal analysis. The three bipyridiniums allow the exploration of the effect of different conjugated systems on molecular packing and charge-transfer interactions. A type of –DDDD– stacking column with edge-to-edge short D⋯A⋯D contacts is found in MV compound 1, while in π-extended MeBpe compound 2, a –DADDAD– type of stacking column with face-to-face short D⋯D and A⋯D stacking is formed, which shows the most effective cation–anion interaction. No effective interaction is found for the non-conjugated MeBpa compound 3. The charge-transfer from an anion to a cation measured by UV-vis, CV and ESR is in the order of 2 > 1 ≫ 3, which is greatly in accordance with the order of the cation's conjugated state and CT interaction. It is known that charge-transfer is a key factor in obtaining photoelectric materials. Photocurrent responses of these compounds are consequently studied and the results agree with the intensity of charge-transfer. This is a systematic study of the effect of different π-conjugated systems on charge-transfer properties in terms of crystal structures.

Solvothermal Preparation, Crystal Structure, and Photoluminescence of a Cadmium Compound With a Two-Dimensional Supramolecular Layer

By virtue of a solvothermal reaction, a new cadmium-bipyridinium derivative (N,N′-dimethyl-4,4′-bipyridinium)3(CdCl3-HCl-CdCl3)(CdBr4)2 (1) with the N,N′-dimethyl-4,4′-bipyridinium cation obtained in situ, was synthesized and characterized by X-ray single-crystal diffraction method. The title compound is characteristic of an isolated structure. The anions and cations in 1 are connected through hydrogen-bonding interactions to give a two-dimensional (2-D) supramolecular layer. The fluorescence result discovers a wide emission band in the green region.

A Convenient N-Arylation Route for Electron-Deficient Pyridines: The Case of π-Extended Electrochromic Phosphaviologens.

A simple and representative procedure for the synthesis of N,N'-diarylated phosphaviologens directly from both electron-rich and electron-poor diaryliodonium salts and 2,7-diazadibenzophosphole oxide is reported. The latter are electron-deficient congeners of the widely utilized N,N'-disubstituted 4,4'-bipyridinium cations, also known as viologens, that proved to be inaccessible by the classical two-step route. The single-step preparation method for phosphaviologens described herein could be extended to genuine viologens but reached its limit when sterically demanding diaryliodonium salts were used. The studied phosphaviologens feature a significantly lowered reduction threshold as compared to all other (phospha)viologens known to date due to the combination of an extended π-system with an electron deficient phosphole core. In addition, a considerably smaller HOMO-LUMO gap was observed due to efficient π-delocalization across the phosphaviologen core, as well as the N-aryl substituents, which was corroborated by quantum chemical calculations. Detailed characterizations of the singly reduced radical species by EPR spectroscopy and DFT calculations verified delocalization of the radical over the extended π-system. Finally, to gain deeper insight into the suitability of the new compounds as electroactive and electrochromic materials, multicolored proof-of-concept electrochomic devices were manufactured.

Hydrogen-Bond Controlled π-Dimerization in Viologen-Appended Calixarenes: Revealing a Subtle Balance of Weak Interactions.

The intramolecular π-dimerization between two 4,4'-bipyridinium cation radicals directly connected to the wide rim of a calixarene is described. The ability of a phenol-containing calixarene to dimerize in its two-electron-reduced state depends on a subtle balance of weak interactions associated with hydrogen bond formation on the lower rim and orbital overlap between π-radicals on the upper rim.

Impact of the Extended 1,1′-Bipyridinium Structure on the Electron Transfer and π-Dimer Formation. Spectroelectrochemical and Computational Study

The electrochemical reduction of the extended 1,1′-bipyridinium dication was investigated in detail by means of semiquantitative in situ electron paramagnetic resonance (EPR), UV–vis–NIR spectroelectrochemistry, and density functional theory (DFT) calculations. It was found that in the extended 1,1′-bipyridinium cation radical the spin density is localized on one of the pyridinium centers, which is in contrast to charge delocalization within the 4,4′-bipyridinium radical cation reported in the literature. The charge and spin density separation in the extended 1,1′-bipyridinium cation radical leads to π-dimer formation in a triplet electronic configuration.

Compounds based on cluster anion [Re4Te4(CN)12]4−, Ln3+ cations (Ln = Gd, Tb, Dy, Ho, Er) and 4,4′-bipyridine: Synthesis, structure and properties

Compounds with general formula (bipyH2)[{Ln(H2O)6}{Re4Te4(CN)12}]2·10H2O (Ln=Gd (1), Dy (2), Tb (3), Ho (4), Er (5)) were obtained by evaporation of acidic aqueous solution containing salts of [Re4Te4(CN)12]4− cluster anion, respective lanthanide cation and 4,4′-bipyridine. Structures of compounds 1–5 consist of dimeric cluster fragments [{Ln(H2O)6}{Re4Te4(CN)12}]22−, forming supramolecular ionic structure with outer-sphere 4,4′-bipyridinium cations and H2O molecules. Magnetic susceptibility of all compounds in the range of temperature 80–300K was measured; thermal stability was also investigated.

Conductometric and UV–Visible Spectroscopic Studies on Association in Dilute Aqueous Solutions of Dq2Fe(CN)6

Electrical conductivities and electronic absorption spectra of Dq2Fe(CN)6 (where Dq2+ is diquat, the N,N′-ethylene-2,2′-bipyridine cation) were measured in dilute solutions in water. Experimental data were interpreted in terms of a molecular model which includes the presence of 1:1 and 2:1 associates. Initially, electrical conductivities and absorption spectra were treated using the Quint–Viallard conductivity equations and modified Hemmes algorithm in a limited concentration range, when only minor 2:1 complex formation is expected. The thermodynamic association constant of the 1:1 complex (\( K_{ 1}^{{^\circ }} \) = 17,800 ± 1800 dm3·mol−1) and the corresponding contact distance (rmin = 5.31 ± 0.07 A) were evaluated from the spectral data. Analysis of the conductivity data resulted in \( K_{ 1}^{{^\circ }} \) = 16,500 ± 1500 dm3·mol−1 (rmin = 5.38 ± 0.07 A). Both contact distances were found to agree with the Fe···N distances in crystalline DqH2Fe(CN)6·4H2O and Dq2Fe(CN)6·6H2O. This agreement allowed us to use the same rmin value to estimate the association constant of the 2:1 complex in accordance to the Fuoss–Krauss theory. Both \( K_{ 1}^{{^\circ }} \) and \( K_{ 2}^{{^\circ }} \) were used to calculate electrical conductivities and optical absorbancies in the concentration range up to 5 mmol·dm−3. Satisfactory agreement was achieved between calculated and experimental data.

Synthesis and Structural Characterization of [(Pb6I22)(DMF)2(DPB)5] Directed by 1,1′-dipentyl-4,4′-bipyridinium Cation

In this study, one novel hexanuclear black crystals, namely [(Pb6I22)(DMF)2(DPB)5] were obtained from the solution-phase reaction of PbI2 in the present of excess KI directed by viologen-based linear templates in MeOH/DMF (DPB= 1,1′-dipentyl-4,4′-bipyridinium). Single-crystal X-ray diffraction analysis showed that this supramolecular compound crystallized in the monoclinic system with the space group P2(1)/c. Electrostatic interactions between the organic dications and inorganic moieties and hydrogen-bond interactions between structural unit are present and contribute to the crystal packing. IR spectroscopy was performed to further characterize title compound.

Ferrocenyl–Bipyridinium Cations and Their Platinum Complexes Related to Viologens – Preparation, Redox Properties, and Crystal Structures

N-R1-N′-R2-4,4′-Bipyridinium and N-R1-4,4′-bipyridinium salts containing ferrocenyl substituents were prepared as donor–acceptor compounds (R1 = ferrocenyl, ferrocenylphenyl; R2 = ferrocenyl, ferrocenylphenyl, phenyl, methyl). Platinum(II)-bridged diferrocene compounds were prepared by using the N-R1-4,4′-bipyridinium ligands. These compounds display multistage redox properties. The redox potentials of the ferrocenyl and bipyridinium moieties in these compounds are independently affected by molecular modifications, which indicates that conjugation between the donor and acceptor moieties is less effective. Single-crystal X-ray diffraction analyses revealed large twist angles between the two moieties in the solid state. The compounds exhibit broad charge-transfer absorption bands in the range 450–800 nm. No electronic communication was observed between the terminal ferrocenes in the diferrocene complexes.

DNA interaction with dipolar ruthenium(II) ammine complexes containing 4,4′-bipyridinium as photochemotherapeutic agents

The interaction of DNA with dipolar ruthenium(II) ammine complexes containing 4,4′-bipyridinium cations L+, [Ru(L+)(NH3)5]3+, has been investigated by spectroscopic and electrochemical methods. These ruthenium(II) complexes undergo strong stacking interactions of L+ with the base-pairs of DNA duplex in addition to the electrostatic and hydrogen binding modes. The phbp+ ([2]3+) and pymbp+ ([3]3+) complexes bind to DNA more strongly than the mebp+ ([1]3+) complex, due to the presence of extended planar aromatic ligands. [3]3+ which exhibited the strongest interaction with DNA can bind to supercoiled plasmid pBR322 DNA following photoinduced loss of ligands pymbp+ and NH3. The finding led to the photocleavage of supercoiled plasmid pBR322 DNA by [3]3+ with visible light under aerobic and unaerobic conditions. Since similar photolysis of [1]3+ and [2]3+ has been observed, all the dipolar ruthenium(II) ammine complexes bearing 4,4′-bipyridinium cations can function as O2-independent photochemotherapeutic agents.

Crystal structure of 4,4'-bipyridine-1,1'-diium naphthalene-2,6-di-sulfonate dihydrate.

The title hydrated mol­ecular organic salt, C10H10N2 2+·C10H6O6S2 2−·2H2O, crystallized with half a bipyridinium cation, half a naphthalene-2,6-di­sulfonate anion and a water mol­ecule in the asymmetric unit. The whole cation and anion are generated by inversion symmetry, the inversion centers being at the center of the bridging C—C bond of the cation, and at the center of the fused C—C bond of the naphthalene group of the anion. In the crystal, the anions and cations stack alternately along the a axis with π–π inter­actions [inter-centroid distance = 3.491 (1) Å]. The anions are linked via O—H⋯O(sulfonate) hydrogen bonds involving two inversion-related water mol­ecules, forming chains along [10-1]. These chains are bridged by bifurcated N—H⋯(O,O) hydrogen bonds, forming a three-dimensional framework structure. There are also C—H⋯O hydrogen bonds present, reinforcing the framework structure.

Synthesis and Catalytic Reactions of Nanoparticles formed by Electrospray Ionization of Coinage Metals

AbstractNoble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped‐nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p‐nitrophenol by NaBH4. Efficient catalysis was also observed by simply directing the spray of solvated Au+ onto the surface of an aqueous p‐nitrophenol/NaBH4 mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, CuI bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene.

Synthesis and Catalytic Reactions of Nanoparticles formed by Electrospray Ionization of Coinage Metals

Noble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped-nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p-nitrophenol by NaBH4 . Efficient catalysis was also observed by simply directing the spray of solvated Au(+) onto the surface of an aqueous p-nitrophenol/NaBH4 mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, Cu(I) bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene.

Electrochemical Capture of Carbon Dioxide in An Ionic Liquid Using N-Methyl-4,4'-Bipyridinium Cation

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Solvothermal synthesis, structural characterization and properties of two new layered lanthanide sulfates

Two new layered lanthanide sulfates, [C10H10N2][Pr2(SO4)4(H2O)2](1) and [H5O2][Sm(SO4)2(H2O)3](2) were synthesized via solvothermal reaction and structurally characterized by single-crystal X-ray diffraction(XRD), infrared(IR) spectroscopy, thermal analysis, fluorescent spectra and inductively coupled plasma(ICP). Crystal data for compound 1, triclinic, P-1 space group, a=0.8052(4) nm, b=0.9438(4) nm, c=1.4990(7) nm, α=79.450(5)°, β=83.703(5)°, γ=74.048(5)°, V=1.0746(9) nm3, Z=2; for compound 2, monoclinic, P2(1)/c space group, a=0.6599(11) nm, b=1.8940(3) nm, c=0.8765(14) nm, β=96.596(2)°, V=1.0883(3) nm3, Z=4. Structure analysis indicates that both the compounds exhibit a 2D corrugated layer structure, with protonated 4,4′-bipyridine cations and water dimmers (H5O2)+ located between the inorganic layers of compounds 1 and 2, respectively. Luminescent properties of compounds 1 and 2 were further investigated.