Bipyridine Units Research Articles

A Conjugated Polymer Containing a B ← N Unit for Unipolar n-Type Organic Field-Effect Transistors

Solution-processed organic field-effect transistors (OFETs) have great potential for next-generation “plastic electronics”. The development of n-type polymer semiconductors still lags far behind that of p-type polymer semiconductors, including material number and device performance. Moreover, the reported high-performance n-type polymer semiconductors are mostly based on amide and imide units. To enrich the family of n-type polymers and promote the development of OFETs, we have proposed using a boron–nitrogen coordination bond (B←N) to develop n-type polymer semiconductors. In this work, we report a B←N-containing conjugated polymer, PBN-13, which is an alternating polymer of a double B←N-bridged bipyridine unit and a 5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole unit. This polymer exhibits strong aggregation ability in solution and good crystallinity in a thin film, which are very desirable for achieving good electron-transporting properties. The OFET device based on PBN-13 shows unipolar ...

Excited-State Dynamics of 2,2′-Bipyridine Moieties Embedded in the Framework of Periodic Mesoporous Organosilica

We investigate the excited-state dynamics of 2,2′-bipyridine (BPy) moieties in a framework of BPy-bridged periodic mesoporous organosilica (BPy-PMO), which is a unique solid chelating ligand that has densely and regularly arranged BPy units that are exposed on the pore surfaces. The steady-state absorption spectrum of BPy-PMO shows broad absorption bands and a prolonged absorption tail compared to its precursor molecule, which suggests that a part of the BPy moieties form dimers and/or aggregates in the ground state. Transient absorption spectra of BPy-PMO after excitation with 295 nm light show mainly intersystem crossing from the lowest singlet excited state (S1) to the lowest triplet excited state (T1) of BPy moieties with a lifetime of 52 ps. Energy transfer (7.2 ps) from the S1 of a BPy monomer to BPy dimers and/or aggregates is also suggested. The lifetime of the excited BPy dimers and/or aggregates is estimated by selective excitation (355 nm) to be 3.4 ns. The lifetime for the T1 of the BPy monomer is estimated to be 700 ns from transient absorption spectra of BPy-PMO after nanosecond 266 nm pulse irradiation. The characteristics of the excitation-relaxation processes of BPy-PMO are discussed.

A pseudorotaxane formed from a cucurbit[7]uril wheel and a bioinspired molecular axle with pH, light and redox-responsive properties

Abstract A pH-, light- and redox-responsive flavylium-bipyridinium molecular dyad (bioinspired in natural anthocyanins) was synthesized and employed to devise a pseudorotaxane with the macrocycle cucurbit[7]uril (CB7) in aqueous solution. The inclusion complex was characterized by UV-Vis absorption, fluorescence emission, NMR and electrochemical techniques which demonstrate formation of a stable binary complex between the dyad and CB7 both under acidic and neutral conditions. It is noteworthy that the flavylium-bipyridinium tricationic dyad is only stable in highly acidic media, undergoing a reversible hydration reaction at slightly acidic or neutral pH to give a trans-chalcone-bipyridinium dication. 1H NMR experiments showed that in this last species the CB7 binds to the bipyridinium unit while in the tricationic species the macrocycle is positioned between the flavylium and the bipyridinium moieties. The different location of the CB7 wheel in the two dyad states allows control of the shuttling movement using light and pH stimuli that trigger the interconversion between these two species.

Solid-Phase Zincke Reaction for the Synthesis of Peptide-4,4′-bipyridinium Conjugates

We present herein the development of a new synthetic strategy for the conjugation of 4,4′-bipyridinium derivatives into peptide scaffolds. The methodology, based on the development of a solid-phase version of the Zincke reaction between activated pyridinium salts and amines, is able to produce the desired conjugates in a straightforward fashion, with the bipyridinium units attached at the N-terminus of peptides or at Lys side chains of N-terminal acetylated peptides.

(2,2-Bipyridine-κ2 N,N′)chlorido[η6-1-methyl-4-(propan-2-yl)benzene]ruthenium(II) tetraphenylborate

The title complex, [RuCl(C10H14)(C10H8N2)](C24H20B), has monoclinic (P21) symmetry at 100 K. It was prepared by the reaction of the dichlorido[1-methyl-4-(propan-2-yl)benzene]ruthenium(II) dimer with 2,2′-bipyridine, followed by the addition of ammonium tetraphenylborate. The 1-methyl-4-(propan-2-yl)benzene group, the 2,2′-bipyridine unit and a chloride ion coordinate the ruthenium(II) atom, with the 1-methyl-4-(propan-2-yl)benzene ring and bipyridine moieties trans to each other. In the crystal, the complex cations are linked by C—H...Cl hydrogen bonds, forming chains parallel to [010]. These chains are linked by a number of C—H...π interactions, involving the phenyl rings of the tetraphenylborate anion and a pyridine ring of the bpy ligand, resulting in the formation of layers parallel to (10\overline{1}).

Towards the Stepwise Assembly of Molecular Borromean Rings. A Donor-Acceptor Ring-in-Ring Complex

The assembly of molecular Borromean Rings from constitutionally independent rings in a stepwise manner depends on the preparation of robust “ring-in-ring” complexes. The π-electron rich macrocycle bis-1,5-dinaphtho[50]crown-14 (1) is shown to form a donor-acceptor ring-in-ring complex with the π-electron poor cyclophane cyclobis(paraquat-4,4'-biphenylene) (24+) in solution. In the crystal superstructure of [1⊂2]·4PF6, CH···O interactions between the polyether loops of 1 and the bipyridinium units of 24+ could disfavor the threading of dialkylammonium components of a third ring.
 

Large Synthetic Molecule that either Folds or Aggregates through Weak Supramolecular Interactions Determined by Solvent.

Weak noncovalent interactions between large disclike molecules in poorly solvating media generally lead to the formation of fibers where the molecules stack atop one another. Here, we show that a particular chiral spacing group between large aromatic moieties, which usually lead to columnar stacks, in this case gives rise to an intramolecularly folded structure in relatively polar solvents, but in very apolar solvents forms finite aggregates. The molecule that displays this behavior has a C3 symmetric benzene-1,3,5-tris(3,3′-diamido-2,2′-bipyridine) (BTAB) core with three metalloporphyrin units appended to it through short chiral spacers. Quite well-defined chromophore arrangements are evident by circular dichroism (CD) spectroscopy of this compound in solution, where clear exciton coupled bands of porphyrins are observed. In more polar solvents where the molecules are dispersed, a relatively weak CD signal is observed as a result of intramolecular folding, a feature confirmed by molecular modeling. The intramolecular folding was confirmed by measuring the CD of a C2 symmetric analogue. The C3 symmetric BTAB cores that would normally be expected to stack in a chiral arrangement in apolar solvents show no indication of CD, suggesting that there is no transfer of chirality through it (although the expected planar conformation of the 2,2′-bipyridine unit is confirmed by NMR spectroscopy). The incorporation of the porphyrins on the 3,3′-diamino-2,2′-bipyridine moiety spaced by a chiral unit leaves the latter incapable of assembling through supramolecular π–π stacking. Rather, modeling indicates that the three metalloporphyrin units interact, thanks to van der Waals interactions, favoring their close interactions over that of the BTAB units. Atomic force microscopy shows that, in contrast to other examples of molecules with the same core, disclike aggregates (rather than fibrillar one dimensional aggregates) are favored by the C3 symmetric molecule. The closed structures are formed through nondirectional interlocking of porphyrin rings. The chiral spacer between the rigid core and the porphyrin moieties is undoubtedly important in determining the outcome in polar or less polar solvents, as modeling shows that this joint in the molecule has two favored conformations that render the molecule relatively flat or convex.

Complexation of bipyridinium guests in the cavity of Acyclic Cucurbit[n]uril receptor

ABSTRACTA series of bipyridinium guests have been synthesised, and their inclusion complexes with acyclic CB[n]-type receptor have been investigated by NMR, UV-Vis spectroscopy, and X-ray diffraction. Novel [3]pseudorotaxane was formed by C-H … O, π-π and ion–dipole interactions. The impact of their complexation on the equilibrium between monomer and dimer of bipyridinium cation radicals has also been studied by UV-Vis-NIR and EPR spectroscopy. Upon reduction, the bipyridinium units linked by flexible pentylene chain preferred the formation of the dimer in the presence of acyclic CB[n]-type receptor, whereas those connected by rigid xylene bridge were suppressed as monomeric form due to the steric effect.

Novel Organic Electrode Materialsfor Innovative Thick Electrode Based Aqueous Batteries

Thanks to the use of abundant chemical elements, organic chemistry provides great opportunities for discovering innovative electrode materials, which could be prepared (i) from renewable resources (biomass) and (ii) via eco-efficient processes, making the concept of greener and sustainable batteries possible [1]. Two types of reaction mechanisms can be used: n-type involving charge transfer with cation release/uptake and p-type involving anion uptake/release [2-5]. We are putting a lot of efforts on greener and sustainable organic batteries. In this communication, we report on novel materials, their uncommon reaction mechanism, and the performance of full aqueous cells. We focus on aqueous organic batteries as a new promising green technology, barely studied yet, for which negative electrodes are missing. We have designed and synthesized novel mixed p- and n-type “bi-block” oligomer negative electrodes with repeating units made of naphthalene diimide and bipyridinium units [6]. They demonstrate optimal potential, extremely fast kinetics and highly competitive capacity and cyclability in both neutral aqueous Na and Mg electrolytes, including ocean water. Based on these findings, full organic cells bearing millimeter thick electrodes were assembled and tested [7]. These findings make a big step forward the design of low-cost rocking-chair dual-ion aqueous batteries. References 1) P. Poizot, F. Dolhem, Energy Environ. Sci. 4, 2003 (2011). 2) Z. Song and H. Zhou, Energy Environ. Sci. 6, 2280 (2013). 3) S. Gottis, A.-L. Barrès, F. Dolhem, P. Poizot, ACS Appl Mater Interfaces 6, 10870 (2014). 4) E. Deunf, P. Moreau, E. Quarez, D. Guyomard, F. Dolhem, P. Poizot, J. Mater. Chem. A, 4, 6131 (2016). 5) E. Deunf, P. Jimenez, D. Guyomard, F. Dolhem, P. Poizot, Electrochem. Comm., 72, 64 (2016). 6) S. Perticarari, Y. Sayed-Ahmad-Baraza, C. Ewels, P. Moreau, D. Guyomard, P. Poizot, F. Odobel, J. Gaubicher, Adv. Energy Mater., 8, 1701988 (2018). 7) S. Perticarari, E. Grange, T. Doizy, Y. Pellegrin, E. Quarez, K. Oyaizu, A. J. Fernandez, D. Guyomard, P. Poizot, F. Odobel and J. Gaubicher, Chem. Mat., in revision

Photoinduced Intercomponent Processes in Selectively Addressable Bichromophoric Dyads Made of Linearly Arranged Ru(II) Terpyridine and Expanded Pyridinium Components.

Three new linearly arranged bichromophoric systems 1-3 have been prepared, and their photophysical properties have been studied, taking also advantage of femtosecond pump-probe transient absorption spectroscopy. The three compounds contain the same chromophores, that is a Ru(II)-terpy-like species and a fused expanded bipyridinium (FEBP) unit, separated by three different, variously methylated biphenylene-type bridges. The chromophores have been selected to be selectively addressable, and excitation involving the Ru-based or the FEBP-based dyes results in different excited-state decays. Upon Ru-based excitation at 570 nm, oxidative photoinduced electron transfer (OPET) takes place in 1-3 from the 3MLCT state; however, the charge-separated species does not accumulate, indicating that the charge recombination rate constant exceeds the OPET rate constant. Upon excitation of the organic dye at 400 nm, the FEBP-based 1π-π* level is prepared, which undergoes a series of intercomponent decay events, including (i) electron-exchange energy transfer leading to the MLCT manifold (SS-EnT), which successively decays according to 570 nm excitation, and (ii) reductive photoinduced electron transfer (RPET), leading to the preparation of the charge-separated (CS) state. Reductive PET, involving the FEBP-based singlet state, is much faster than oxidative PET, involving the MLCT triplet state, essentially because of driving force reasons. The rate constant of CR is intermediate between the rate constants of OPET and RPET, and this makes 1-3 capable to selectively read the 400 nm excitation as an active input to prepare the CS state, whereas excitation at wavelengths longer than 480 nm is inefficient to accumulate the CS state. Moreover, intriguing differences between the rate constants of the various processes in 1-3 have been analyzed and interpreted according to the superexchange theory for electron transfer. This allowed us to uncover the role of the electron-transfer and hole-transfer superexchange pathways in promoting the various intercomponent photoinduced decay processes occurring in 1-3.

Bis-4-aza[6]helicene: A Bis-helicenic 2,2'-Bipyridine with Chemically Triggered Chiroptical Switching Activity.

A novel enantiopure bis-helicenic 2,2'-bipyridine system was prepared using a Negishi coupling. Thanks to the bipyridine unit, the coordination with ZnII and protonation processes were studied, revealing efficient tuning of photophysical (UV/visible and emission) and chiroptical properties (electronic circular dichroism and circularly polarized emission) of the system. The coordination/decoordination and protonation/deprotonation processes appeared reversible, thus constituting novel chiroptical switches.

Preparation and Thermoelectric Properties Study of Bipyridine-Containing Polyfluorene Derivative/SWCNT Composites.

Polymer/inorganic thermoelectric composites have witnessed rapid progress in recent years, but most of the studies have focused on the traditional conducting polymers. The limited structures of traditional conducting polymers restrain the development of organic thermoelectric composites. Herein, we report the preparation and thermoelectric properties of a series of composites films based on SWCNTs and bipyridine-containing polyfluorene derivatives. The value of the power factor around 12 μW m−1 K−2 was achieved for the composite F8bpy/SWCNTs with a mass ratio of 50/50, and the maximum value of 62.3 μW m−1 K−2 was obtained when the mass ratio reached 10/90. Moreover, taking advantage of the bipyridine unit could chelate various kinds of metal ions to form polymer complexes. The enhanced power factor of 87.3 μW m−1 K−2 was obtained for composite F8bpy-Ni/SWCNTs with a mass ratio of 50/50. Finally, the thermoelectric properties of the bipyridine-containing polyfluorene derivative/SWCNT composites were conveniently tuned by chelating with different metal ions.

Tunable photochromic properties of hybrid solids controlled by the conjugated length of non-photochromic units

The photochromic performance of two hybrid zincophosphite frames could be tuned via enlarging the conjugated length of the non-photochromic bipyridine unit.

Directed Self-Assembly of Trimeric DNA-Bindingchiral Miniprotein Helicates.

We propose that peptides are highly versatile platforms for the precise design of supramolecular metal architectures, and particularly, for the controlled assembly of helicates. In this context, we show that the bacteriophage T4 Fibritin foldon (T4Ff) can been engineered on its N-terminus with metal-chelating 2,2′-bipyridine units that stereoselectively assemble in the presence of Fe(II) into parallel, three-stranded peptide helicates with preferred helical orientation. Modeling studies support the proposed self-assembly and the stability of the final helicate. Furthermore, we show that these designed mini-metalloproteins selectively recognize three-way DNA junctions over double-stranded DNA.

Programmable Multicomponent Self-Assembly Based on Aromatic Amino Acids.

Construction of integrated self-assembly with ordered structures from two or more organic building blocks is currently a challenge, since it suffers from intrinsic systematic complexity and diverse competitive pathways. Here, it is reported that aromatic amino acid building units can be incorporated into two- or three-component coassembly driven primarily by hydrogen bonding interactions without the assistance of metal-ligand and macrocycle-based host-guest interactions. The key strategy is to employ a C3 -symmetric molecule with alternative hydrogen bonding donor/acceptor sites that are able to bind either carboxylic acid or pyridine appended building units. Aromatic amino acids, C3 -symmetric compound, and bipyridine unit constitute a unique ternary mutual binding system, where three coassembly pathways including two pairwise formations and one ternary combination are unveiled, giving rise to two- and three-component self-assemblies with ordered structures, respectively. The pathway complexity lies in the structural parameter of aromatic amino acids, which can be programmable by controlling substituents at the α-position of amino acids.

Supramolecular Networks and Wires Dominated by Intermolecular BiEDOT Interactions

The ditopic ligand bpy-PE2P-bpy self-assembles on surfaces and has been investigated by high resolution scanning tunneling microscopy. The molecule shows a cis-to-trans isomerization from its bipyridine terminal units, whereas the biEDOT central bridge is always locked in its trans conformation thanks to the intramolecular sulfur–oxygen interactions. The cis-bpy-PE2P-bpy conformers form linear supramolecular stripe and herringbone structures. Upon protonation, they are transformed to the trans conformers which form both a zigzag structure and different supramolecular wires of variable width. Long single molecular wires can be easily obtained. In the various supramolecular organizations, the intermolecular hydrogen bonds between the bipyridine units vary. On the contrary, the biEDOT moieties are always aligned in a similar way as that observed in crystallized PEDOT nanofibrils and the intermolecular biEDOT interactions remain identical. Our work contributes to the understanding of the impact of EDOT–EDOT interactions on the properties of organic and molecular devices.

Rational design of a hexameric protein assembly stabilized by metal chelation.

Protein-based self-assembled nanostructures hold tremendous promise as smart materials. One strategy to control the assembly of individual protein modules takes advantage of the directionality and high affinity bonding afforded by metal chelation. Here, we describe the use of 2,2'-bipyridine units (Bpy) as side chains to template the assembly of large structures (MW approx. 35 000 Da) in a metal-dependent manner. The structures are trimers of independently folded 3-helix bundles, and are held together by 2 Me(Bpy)3 complexes. The assemblies are stable to thermal denaturation, and are more than 90% helical at 90°C. Circular dichroism spectroscopy shows that one of the 2 possible (Bpy)3 enantiomers is favored over the other. Because of the sequence pliability of the starting peptides, these constructs could find use to organize functional groups at controlled positions within a supramolecular assembly.

Asymmetric Synthesis of Diastereo‐ and Enantiopure Bioxahelicene 2,2′‐Bipyridines

A versatile asymmetric synthesis of five C2 symmetric enantio‐ and diastereopure bioxa[5]‐ and bioxa[6]helicene 2,2′‐bipyridines was developed. It relied either on a double intramolecular [2+2+2] cycloisomerization of dicyanotetrayne (forming simultaneously the 2,2′‐bipyridine unit and biazaoxahelicene backbone) or one‐pot/sequential intramolecular [2+2+2] cycloisomerization of triyne accompanied by an intermolecular haloazaoxahelicene reductive homocoupling. We reached an effective central‐to‐helical‐to‐axial chirality transfer that was controlled by the 1,3‐allylic‐type strain and sterically constricted atropoisomerization of the embedded 2,2′‐bipyridine unit. The chiroptical properties of the bioxahelicene 2,2′‐bipyridines were studied along with their fluorescence properties.

Densely Charged Dodecacationic [3]- and Tetracosacationic Radial [5]Catenanes

Summary Here, we report the efficient syntheses of a dodecacationic [3]catenane, which consists of three mechanically interlocked 4+ charged rings despite their mutual Coulombic repulsion, and a tetracosacationic radial [5]catenane, which consists of four 4+ charged rings mechanically interlocked around an 8+ charged ring and bears up to 24 positive charges in its co-constitution. The solid-state structures, determined by single-crystal X-ray crystallography, show that the two mechanical bonds in the [3]catenane result in the nano-confinement of 12 positive charges within a volume of less than 1.65 nm3, corresponding to 7.3 positive charges per nm3, whereas the radial [5]catenane has a charge density of 6.0 positive charges per nm3 and a molecular length of up to 3.7 nm. The template-directed strategy for constructing mechanically interlocked molecules, consisting of multiply charged rings, represents a departure in chemistry tantamount to producing a blueprint for exploring a novel class of organic molecules that boast large numbers and high densities of like charges.

Electrochemiluminescence of metallated porous organic polymers

Electrochemiluminescence (ECL) has received considerable attention given its diverse applications, and the preparation of new luminophores remains interesting. Herein we report the synthesis of porous organic polymers containing bipyridine units that can coordinate ruthenium(II) and iridium(III) to form metallated porous organic polymers (MPOPs). We studied electrochemical behaviour and ECL of two MPOPs in the presence of tri-n-propylamine (TPrA) as the co-reactant. They generated ECL at 655 nm and 620 nm upon anodic polarization. The mechanism of ECL generation was investigated by dynamic ECL spooling spectroscopy. Considering MPOPs possess abundant pores, we believe they are potential in the fabrication of solid-state ECL sensors.