Bipyridine Groups Research Articles

Study of the effect of aliphatic and π-conjugated systems on the photophysical properties of polypyridinic Ruthenium II complexes as potential semiconductor materials for iTMC type LEC

The photophysical properties of polypyridinic Ruthenium complexes, as potential semiconductor materials for iTMC (ionic transition metal complex) type LECs have been studied. Substituted 2,2′-bipyridine ligands were used to study the effects of conjugated and aliphatic chains on the properties of the complexes, especially on the photophysical properties. Specifically, the N^N type ligands 4,4′-bis[2-hydroxy-2-(phenyl)ethyl]-2,2′-bipyridine (1), 4,4′-bis(α-styrene)-2,2′-bipyridine (2) and 4,4′-diphenylethyl-2,2′-bipyridine (3) were synthesized, and used to prepare the corresponding [RuII(bpy)2(N^N)](PF6)2 complexes. All three ligands contain a phenyl group as substituent for bpy, but with different residues as bridges between both: ligands 1 and 3 have free rotating connecting groups, while 2 is more rigid due to the styryl double bond. From the achieved results it was observed that, as expected, a conjugation on the ligand produces complexes with bands shifting toward lower energy regions, due to the electronic communication between the phenyl and bipyridine groups. On the contrary, in the absence of this conjugation, as is the case of the complexes with ligands 1 and 3, absorptions and emissions bands are very similar to the corresponding complex with unsubstituted bpy. Therefore, complexes with ligands 1 and 3 seem to be promising for LEC devices, due to the free rotations of the connecting aliphatic chain. This should preserve the properties as emission color, and advantages of Ru(bpy)32+ photoluminescence, but increasing the efficiency when used in a device, avoiding crystallization and diminishing self-quenching processes.

Construction of organic–inorganic hybrid molybdophosphonate clusters with copper–bipyridine

An organic–inorganic hybrid polyoxomolybdate with formula as [Cu(2,2′-bpy)(H2O)]2[Cu(2,2′-bpy)(H2O)3][(O3PCCH3(OH)PO3)2MoVI4O11(H2O)2]·7H2O (1) (2,2′-bpy=2,2′-bipyridine) has been successfully synthesized constructing by diphosphonate H2O3PC(CH3)(OH)PO3H2 (1-hydroxyethylidene-1,1-bisphosphonic acid, noted as HEDP or etidronate) under conventional aqueous solution. 1 was characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and X-ray photoelectron spectroscopy (XPS). Each anion cluster of 1 can be regarded as the fusion of two [{Cu(2,2′-bpy)(H2O)}(O3PCCH3(OH)PO3)MoVI2O6]2− subunits with an additional six-coordinated [Cu(2,2′-bpy)]2+ coordination cation linking on one side and there exist weak π–π interactions among the bipyridine groups. The XPS spectra indicate that the oxidation states of Mo and Cu in 1 are +6 and +2, respectively. Photoluminescence properties of 1 and the free 2,2′-bipyridine ligand have been both analyzed, showing that the presence of ligand-to-metal-charge-transfer (LMCT) transitions and metal–ligand coordination have an important effecting on the photoluminescence.

Functionalized, carbon nanotube material for the catalytic degradation of organophosphate nerve agents

Recent world events have emphasized the need to develop innovative, functional materials that will safely neutralize chemical warfare (CW) agents in situ to protect military personnel and civilians from dermal exposure. Here, we demonstrate the efficacy of a novel, proof-of-concept design for a Cu-containing catalyst, chemically bonded to a single-wall carbon nanotube (SWCNT) structural support, to effectively degrade an organophosphate simulant. SWCNTs have high tensile strength and are flexible and light-weight, which make them a desirable structural component for unique, fabric-like materials. This study aims to develop a self-decontaminating, carbon nanotube-derived material that can ultimately be incorporated into a wearable fabric or protective material to minimize dermal exposure to organophosphate nerve agents and to prevent accidental exposure during decontamination procedures. Carboxylated SWCNTs were functionalized with a polymer, which contained Cu-chelating bipyridine groups, and their catalytic activity against an organophosphate simulant was measured over time. The catalytically active, functionalized nanomaterial was characterized using X-ray fluorescence and Raman spectroscopy. Assuming zeroth-order reaction kinetics, the hydrolysis rate of the organophosphate simulant, as monitored by UV-vis absorption in the presence of the catalytically active nanomaterial, was 63 times faster than the uncatalyzed hydrolysis rate for a sample containing only carboxylated SWCNTs or a control sample containing no added nanotube materials. Open image in new window

A Solid Chelating Ligand: Periodic Mesoporous Organosilica Containing 2,2′-Bipyridine within the Pore Walls

Synthesis of a solid chelating ligand for the formation of efficient heterogeneous catalysts is highly desired in the fields of organic transformation and solar energy conversion. Here, we report the surfactant-directed self-assembly of a novel periodic mesoporous organosilica (PMO) containing 2,2'-bipyridine (bpy) ligands within the framework (BPy-PMO) from a newly synthesized organosilane precursor [(i-PrO)3Si-C10H6N2-Si(Oi-Pr)3] without addition of any other silane precursors. BPy-PMO had a unique pore-wall structure in which bipyridine groups were densely and regularly packed and exposed on the surface. The high coordination ability to metals was also preserved. Various bipyridine-based metal complexes were prepared using BPy-PMO as a solid chelating ligand such as Ru(bpy)2(BPy-PMO), Ir(ppy)2(BPy-PMO) (ppy = 2-phenylpyridine), Ir(cod)(OMe)(BPy-PMO) (cod = 1,5-cyclooctadiene), Re(CO)3Cl(BPy-PMO), and Pd(OAc)2(BPy-PMO). BPy-PMO showed excellent ligand properties for heterogeneous Ir-catalyzed direct C-H borylation of arenes, resulting in superior activity, durability, and recyclability to the homogeneous analogous Ir catalyst. An efficient photocatalytic hydrogen evolution system was also constructed by integration of a Ru-complex as a photosensitizer and platinum as a catalyst on the pore surface of BPy-PMO without any electron relay molecules. These results demonstrate the great potential of BPy-PMO as a solid chelating ligand and a useful integration platform for construction of efficient molecular-based heterogeneous catalysis systems.

Giant Electroactive M4L6 Tetrahedral Host Self-Assembled with Fe(II) Vertices and Perylene Bisimide Dye Edges

Self-assembly of octahedral Fe(II) ions and linear perylene bisimide (PBI) dyes with 2,2'-bipyridine groups covalently attached at the imide positions quantitatively yields an Fe4(PBI)6 tetrahedron by the directional bonding approach. With an edge length of 3.9 nm and estimated internal volume >950 Å(3), tetrahedron T is one of the largest M4L6 tetrahedra ever reported. Importantly, many of the desirable photo- and electroactive properties of the PBI ligands are transferred to the nanoscale metallosupramolecule. Tetrahedron T absorbs strongly across the visible spectrum out to 650 nm and exhibits a total of 7 highly reversible electrochemical oxidation and reduction waves spanning a 3.0 V range. This facile cycling of 34 electrons between +18 and -16 charged species is likely enabled due to the porous nature of the tetrahedron that allows the necessary counterions to freely flow in and out of the host. Host-guest encapsulation of C60 by T in acetonitrile was studied by (13)C NMR spectroscopy, UV-vis spectroscopy, and ESI-MS, confirming that the tetrahedron is a suitable host for large, functional guest molecules.

Hierarchical Assembly of Collagen Peptide Triple Helices into Curved Disks and Metal Ion-Promoted Hollow Spheres

A 27 amino acid collagen-based peptide (Hbyp3) was designed to radially display nine hydrophobic bipyridine moieties from a triple helical scaffold. Self-assembly of such functionalized triple helices led to the formation of micrometer-scaled disks with a curved morphology, presumably mediated by aromatic interactions, with a height that is in the range of the length of the triple helical peptide. Higher order assembly of these curved disks into micrometer-sized hollow spheres was accomplished through metal-ligand interactions between bipyridine groups of the disks and metal ions such as Fe(II), Co(II), Zn(II) and Cu(II). The thickness of the shell of these hollow spheres corresponds well with the thickness of the collagen peptide-based triple helix and the corresponding self-assembled disks. Addition of a metal ion chelator was found to reverse the assembly of the hollow spheres back to the curved disk structures. These data support the formation of the hollow spheres from the self-assembled disks of Hbyp3 upon addition of metal ions.

A New Family of 4f-3d Heterometallic Metal–Organic Frameworks with 2,2′-Bipyridine-3,3′-dicarboxylic Acid: Syntheses, Structures and Magnetic Properties

Eight isostructural lanthanide(III)-cobalt(II) heterometallic metal–organic frameworks (MOFs), {[Ln2Co(BPDC)4(H2O)6]·xH2O}n (Ln = La (1-La, x = 9), Pr (2-Pr, x = 11), Nd (3-Nd, x = 8), Sm (4-Sm, x = 9), Eu (5-Eu, x = 6), Gd (6-Gd, x = 6.5), Tb (7-Tb, x = 7), Dy (8-Dy, x = 8); H2BPDC = 2,2′-bipyridine-3,3′-dicarboxylic acid), have been prepared and characterized. In these complexes, two crystallographically independent Ln3+ ions are connected via carboxyl groups into binuclear units, which are further linked into a lanthanide chain through bridging BPDC2–. Each Co2+ ion is chelated by the bipyridine groups of three BPDC2– and further links the lanthanide chain to form a three-dimensional framework. The framework with one-dimensional channels occupied by water molecules possesses a new topology with the short (Schlafli) vertex symbol {3·62}{32·66·73·83·9}{62·7}. The magnetic properties of the eight heterometallic MOFs have been studied, in which only 8-Dy displays slow relaxation of the magnetization at low...

Cellular Uptake of a Polypyridyl Ruthenium Complex Revealed Using a Fluorescent Rhodamine‐modified Ruthenium Complex

AbstractA fluorescent polypyridyl ruthenium complex was successfully prepared using an amide bond linkage to link two rhodamine moieties through bipyridine groups. Although photo‐induced electron transfer (PET) quenched the fluorescent intensity, the quantum yield of the rhodamine‐modified Ru(II) complex was 0.17 in water, sufficient for observing the fluorophore behaviour in biological systems. The rhodaminemodified Ru(II) complex was found to inhibit the bacterial growth of E. coli. In vitro fluorescence images of human hepatoma cells (SK‐Hep1) showed that a fluorescent polypyridyl ruthenium complex not only supported the above observation but also preferably accumulated in the cytoplasmic region inside the cell. These observations suggest that in addition to strong Ru–DNA interactions, Ru‐protein interactions in the cytoplasmic regions are strong and are therefore important to the development of metallopharmaceuticals.

Synthesis and characterization of a zinc metal–organic framework with chiral nano-pores

Zn3(BPDC)2(O2CH)2·2Et2NCHO is a new metal–organic framework with 2,2′-bipyridine-5,5′-dicarboxylate (BPDC) groups as linkers. Although synthesized solvothermally from achiral components, this MOF has a three dimensional (3D) structure with chiral nano-pores. The zinc centers are linked together by carboxylate groups into trinuclear chains; the two terminal zinc atoms are also bound to bipyridine groups.

(OC-6-35)-(2,2′-Bipyridine-κ2N,N′)dimethyl(3-sulfidopropionato-κ2S,O)platinum(IV)

The title complex, [Pt(CH3)2(SCH2CH2CO2)(C10H8N2)], is formed by the unusual oxidative addition of the disulfide, R 2S2 (R = CH2CH2CO2H), to (2,2′-bipyridine)­dimethyl­platin­um(II) with elimination of RSH. The product contains an unusual six-membered thiol­ate–carboxyl­ate chelate ring. This slightly distorted octa­hedral complex exhibits cis angles ranging from 77.55 (11) to 97.30 (8)° due to the presence of the thiol­ate–carboxyl­ate chelate ring and the constrained bipyridine group. The crystal packing appears to be controlled by a combination of π-stacking [centroid–centroid distance = 3.611 (2) Å] and C—H⋯O inter­actions.

Further Understanding of the Electronic Interactions between N719 Sensitizer and Anatase TiO2 Films: A Combined X-ray Absorption and X-ray Photoelectron Spectroscopic Study

In this study, the electronic properties of N719 adsorbed onto anatase were comparably investigated by using X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) techniques. Sensitized TiO2 films made from two different nanocrystalline anatase powders were investigated: a commercial one (Solaronix) and our synthetic variety produced through aqueous synthesis. This was done to investigate how our aqueous-produced nanocrystalline anatase substrates compared with commercial products and to observe whether both nanocrystalline anatase anodes behaved in a similar manner in terms of their bonding and electronic interactions. Surface coordination changes to Ti−O groups previously reported via Ti K-edge extended X-ray absorption fine structure (EXAFS) data [using transmission or fluorescence yield (FY)] between the pure TiO2 and the adsorbed state were not observed in our measurements via the Ti L or K X-ray absorption near-edge structure (XANES) (nor EXAFS) data for both substrates via a surface-sensitive detection technique (total electron yield, TEY). This is likely due to the probing depth of TEY mode (5−10 nm), in which the coordination changes that occur to the surface groups, which should in turn affect the XANES spectrum, are not observed at Ti K- or L-edge XANES spectrum. The C and N K-edge XANES spectra of the N719 adsorbed onto two TiO2 films were for the first time evaluated in this work. From the C K-edge XANES data, the spectral changes revealed that additional electronic states occur between dye molecules and TiO2 surface. The C K-edge XANES spectra allowed us to propose that electronic interactions do not only occur through the covalent bonding of the anchoring groups but also through the aromatic electron density of the bipyridine groups and the d states found in TiO2. This was further confirmed via XPS analysis by monitoring the N bipyridine groups before and after sensitization. XPS used in combination with XAS (in TEY mode) provided complementary information owing to its higher surface sensitivity. The Ti 2p and O 1s XPS spectra showed that adsorption of the dye on TiO2 leads to a change of the surface dipole and/or a change in the Fermi level position in the band gap, which shifts all the core levels of TiO2. These are not equal for both TiO2 substrates in spite of them being nanocrystallnine anatase. This effect was found to be greater for the N719−aqueous TiO2 system than the respective Solaronix one. For the N 1s and S 2p XPS, the shift toward higher energy indicated that there exists an additional H-bonding interaction of the NCS ligand of the dye molecule with the TiO2 surface groups (OH/H2O).

Morphological Transformation between Nanofibers and Vesicles in a Controllable Bipyridine–Tripeptide Self‐Assembly

Tuning structures: Stimulus-responsive peptide self-assembly requires a balance of conformational change and structural continuity of stable β sheets. In an amphiphilic bipyridine–tripeptide model, temperature, and ultrasound switch a reversible morphological transformation between vesicles and nanofibers (see picture) through the synergistic effects of terminal β-sheet-forming peptides, flexible linkers, and rotatable bipyridine groups.

Determination of the charge transport abilities of polymorphs [C6F5Cu]2(4,4′-bipy) with different interactions: a density functional theoretical investigation

Due to the different molecular stacking conformations, two kinds of intermolecular interactions, arene–arene π-stacking interaction and Cu–Cu interaction coexist in the polymorphs of [C6F5Cu]2(4,4′-bipy) crystals, 3-α and 3-β. However, the relative magnitude of the two kinds of intermolecular interactions in 3-α and 3-β is different. With the help of first-principle band structure calculations, the relationship between the charge transport abilities and the intermolecular interactions in the two polymorphs was investigated for the first time. The analysis of band structures and Г point wave functions of the band-edge state in the valence band of crystal 3-α shows that the Cu–Cu interaction so-called cuprophilic interaction determines the hole transport ability, although this interaction is weaker than that in crystal 2 of C6F5Cu(py) discussed in our previous work, which is a promising hole transport material. For polymorph crystal 3-β, the wave functions of LUMO are mainly localized on the bipyridine (bpy) groups, which are result from the arene–arene π-stacking interaction between the bpy groups. Such a π–π stacking interaction dominates the electron transport ability in the conduction band of 3-β and makes the electron main carrier for transporting. The results are also supported by the analysis of effective masses and density of states (DOS). Thus, the charge transport properties are dominated by different intermolecular interactions due to the different molecule stacking in the two polymorphs.

Oligonuclear polypyridylruthenium(ii) complexes incorporating flexible polar and non-polar bridges: synthesis, DNA-binding and cytotoxicity

The paper reports the synthesis and characterisation of a series of flexible di-bidentate bridging ligands in which two 4-methyl-2,2'-bipyridine groups are linked at the 4'-position by polymethylene (bb(n)), linear polyether (bbO(n)) or linear alkylamine (bbN(n)) chains of varying length (n). The enantiomers (ΔΔ/ΛΛ) of the rac forms of the ruthenium(ii) dinuclear complexes incorporating these ligands -i.e. [{Ru(phen)(2)}(2)(μ-BL)](4+) (phen = 1,10-phenanthroline; BL = bb(n), bbO(n) or bbN(n)) - have been isolated by reaction of Δ- or Λ-[Ru(phen)(2)(py)(2)](2+) (py = pyridine) with the respective bridging ligands. Mononuclear species - in which only one of the bidentate moieties of the bridging ligand is coordinated - have also been isolated, as well as trinuclear and tetranuclear species involving the bb(7) bridge. Fluorescence displacement studies of the DNA-binding of the dinuclear complexes containing the bbO(n) and bbN(n) bridges generally revealed a lower affinity than their bb(n) analogues for an oligonucleotide containing a single bulge site; the mononuclear complexes showed a lower affinity - and the trinuclear and tetranuclear complexes a higher affinity - than the dinuclear species, revealing an interesting interplay of lipophilicity, electrostatics and size in the complex/nucleic acid interaction. Cytotoxicity studies of these complexes against a murine leukaemia cell line revealed that the presence of the polyether or polyamine links in the chain lowered the cytotoxicity compared with their polymethylene analogues, and that the bb(7)-bridged trinuclear and tetranuclear complexes showed considerably enhanced cytotoxicity compared with the dinuclear Rubb(7) analogue.

Synthesis and linear and nonlinear optical properties of metal-terminated bis(dioxaborine) polymethines

Rh(III) and Ir(III) can be complexed to bipyridine groups attached to the termini of bis(dioxaborine)-capped heptamethines; these chromophores exhibit large third-order polarisabilities at 1.55 μm, while retaining good film-forming properties and linear optical transparency in the near infrared.

Thermodynamic Insights into the Dynamic Switching of a Cyclodextrin in a Bistable Molecular Shuttle

A prototypical molecular shuttle formed by dodecamethylene and 4,4′-bipyridinium units and an α-cyclodextrin (CD) was investigated employing molecular dynamics simulations. The free-energy profile characterizing the shuttling process of the α-CD along the molecular thread was determined using the adaptive biasing force method, revealing two thermodynamically stable states separated by a pronounced energy barrier. The free-energy barrier with respect to the stable states is calculated to be +20.6 kcal/mol, in excellent agreement with the experimentally measured quantity. Partitioning of the free energy into contributions of different nature indicates that the shuttling process is primarily controlled by the favorable inclusion of the dodecamethylene chain and the unfavorable inclusion of the cationic bipyridinium group by α-CD. The predominant contribution to the energy barrier stems from the disruption of the solvation shell of the charged group. Deciphering the molecular mechanism of the shuttling proces...

Synthesis and Chemical Properties of Diacetylenes with Pyridinium and 4,4′‐Bipyridinium Groups

AbstractDiacetylenes (DAs) having a dipolar D‐π‐A structure (D=donor: amino group; π=π‐conjugation core; A=acceptor: pyridinium (Py) and bipyridinium (BPy) groups), i.e., 4 (APBPyDA) and 5 (APPyPyDA), or an A‐π‐A structure, i.e., 7 (DBPyDA) and 8 (PyDA(Cl)), were obtained by 1 : 1 and 1 : 2 reactions of 4,4′‐(buta‐1,3‐diyne‐1,4‐diyl)bis[benzenamine] (APDA; 3) with 1‐(2,4‐dinitrophenyl)‐1′‐hexyl‐4,4′‐bipyridinium bromide chloride (1 : 1 : 1) (1), 1‐(2,4‐dinitrophenyl)‐4‐(pyridin‐4‐yl)pyridinium chloride (2), or 1‐(2,4‐dinitrophenyl)pyridinium chloride (6) (Schemes 1 and 2). The anion‐exchange reactions of 8 with NaI and Li(TCNQ) (TCNQ−=2,2′‐(cyclohexa‐2,5‐diene‐1,4‐diylidene)bis[propanedinitrile] radical ion (1−)) yielded the corresponding I− and TCNQ− salts 9 (PyDA(I)) and 10 (PyDA(TCNQ)). Compounds 10 and 4 exhibited a UV/VIS absorption due to a charge transfer between the TCNQ− and the pyridinium groups and a strong solute–solvent interaction of a dipolar solute molecule in the polar environment, respectively. Compounds 8–10 exhibited photoluminescence in solution, whereas 4 and 7 did not because of the presence of the 4,4′‐bipyridinium quenching groups. Differential‐scanning‐calorimetry (DSC) measurements suggested that the DAs obtained in this study can be converted into poly(diacetylenes) by thermal polymerization.

Reversible Formation and Destruction of Micelles of Amphiphilic Compounds in Aqueous Media. Competition with Pseudorotaxane Formation

Abstract N-Alkyl-4,4′-bipyridiniums [4,4′-bpy-N-(CH2)nOAr]+(Cl−) (n = 6 and 10, Ar = C6H3-3,5-t-Bu2, C6H3-3,5-(OMe)2, and C6H2-2,4,6-Me3), having the cationic bipyridinium group and a long hydrophobic alkyl chain, were prepared from the reaction of 4,4′-bipyridine with the corresponding alkyl chlorides. The amphiphilic compounds in water form micelles which encapsulate added pyrene in the hydrophobic core. Addition of α-cyclodextrin to the micellar solution converts a part of the aggregated amphiphilic molecules to their pseudorotaxane with α-cyclodextrin. Formation of the pseudorotaxanes is favored at lower temperature, as is observed by temperature dependent change of the absorption spectra.

Macrocyclic Polycations Made to Order

The cationic 4,4′-bipyridinium group is one of the most effective units to create functional rotaxane structures. This work shows a general synthesis of highly rigid materials and initial demonstrations of their ability to complex neutral donor molecules and charged molecules with complementary charge.

A transparent and luminescent ionogel based on organosilica and ionic liquid coordinating to Eu3+ ions

Herein we present a facile method to prepare a transparent and luminescent ionogel monolith by hydrolysis and condensation of the silylated bipyridine, which can sensitize the luminescence of europium(III) in the presence of a carboxyl-functionalized ionic liquid where Eu3+ ions are coordinated to the oxygen atoms of carboxylate groups from the ionic liquid. FT-IR, TG and photoluminescence spectroscopy were employed to characterize the obtained ionogel. The FT-IR spectrum shows that Eu3+ ions are coordinated to the ionic liquid via the oxygen atoms in the ionogel. Excitation and emission spectra verify that the energy transfer from the bipyridine groups (covalently bound to silica) to Eu3+ ions occurs. The 5D0 quantum efficiency value and the number of water molecules coordinated to Eu 3+ ions in the ionogel have been estimated.