Stable Au(I) catalysts for oxidant-free C-H Functionalization with Iodoarenes.

The development of oxidant-free gold-catalyzed cross coupling reactions involving aryl halides have been hamstrung by the lack of gold catalysts capable of performing oxidative addition at Au(I) centers. Herein, we report the development of novel tricoordinate Au(I) catalysts supported by N,N-bidentate ligands and ligated by phosphine or arsine ligands for C-H functionalization without external oxidants to form biaryls with no homocoupling. The unsymmetrical character of the Au(I) catalyst is critical to facilitating this necessary orthogonal transformation.

Regioselective Hydrogenation of a 60-Carbon Nanographene Molecule toward a Circumbiphenyl Core.

Regioselective peripheral hydrogenation of a nanographene molecule with 60 contiguous sp carbons provides unprecedented access to peralkylated circumbiphenyl (1). Conversion to the circumbiphenyl core structure was unambiguously validated by MALDI-TOF mass spectrometry, NMR, FT-IR, and Raman spectroscopy. UV-vis absorption spectra and DFT calculations demonstrated the significant change of the optoelectronic properties upon peripheral hydrogenation.

Reply to the 'Comment on "Relating side chain organization of PNIPAm with its conformation in aqueous methanol"' by A. Pica and G. Graziano, Soft Matter, 2017, 13, DOI: 10.1039/C7SM01065F.

We have recently proposed preferential binding by a cosolvent as the mechanism for chain collapse under co-non-solvency. Here we summarise our earlier works and provide further evidence that alcohol preferentially binds to PNIPAm, forming cosolvent bridges, and thus drives the transition. We also clarify some of the common misconceptions evoked in this debate with Pica and Graziano (PG), reinforcing the arguments of our earlier reply-comment [Soft Matter, 2017, 13, 2292] and published works.

Reply to the 'Comment on "Relating side chain organization of PNIPAm with its conformation in aqueous methanol"' by N. van der Vegt and F. Rodriguez-Ropero, Soft Matter, 2017, 13, DOI: 10.1039/C6SM02139E.

In a comment van der Vegt and Rodriguez-Ropero (vdVRR) challenged our explanation of the co-non-solvency effect of PNIPAm in aqueous methanol solutions. They argue, based on a careful selection of published studies including some of their own, that direct repulsions between the different constituents are sufficient to understand this phenomenon. According to vdVRR, the emerging view of entropic collapse, put forward by Flory (1910-1985) to explain common polymers in poor solvents, would be enough to explain co-non-solvency.

Relating side chain organization of PNIPAm with its conformation in aqueous methanol.

Combining nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and μs long all-atom simulations with two million particles, we establish a delicate correlation between increased side chain organization of PNIPAm and its collapse in aqueous methanol mixtures. We find that the preferential binding of methanol with PNIPAm side chains, bridging distal monomers along the polymer backbone, results in increased organization. Furthermore, methanol-PNIPAm preferential binding is dominated by hydrogen bonding.

Conjugated polymers with large effective Stokes shift: benzobisdioxole-based poly(phenylene ethynylene)s.

Phenyleneethynylene-based conjugated copolymers using benzo[1,2-d:4,5-d']bis[1,3]dioxole (BDO) in the repeating unit are reported. The electronic structure of the BDO unit imparts a localized HOMO topology while the LUMO is delocalized over the polymer backbone, so that the lowest optical absorption band of the polymer has considerable intramolecular charge transfer character. This contrasts with published donor-acceptor polymers with localized LUMO and delocalized HOMO.

Phthalimide-based polymers for high performance organic thin-film transistors.

The synthesis and characterization of two new thiophene copolymers with backbone phthalimide units is reported. Thin-film optical and wide-angle X-ray diffraction measurements indicate extended electronic conjugation and close intermolecular pi-stacking for both polymers. Ambient carrier mobility of thin-film transistors prepared from these polymers is as high as 0.

Conjugated polymers from naphthalene bisimide.

Stille coupling of regioisomerically pure dibromonaphthalene bisimides (NBI) with various stannylated thiophene-based monomers yields (very) high molecular weight donor-acceptor conjugated polymers. Electrochemical and optical absorption measurements reveal that LUMO energies are essentially invariant and dictated by the NBI units, while HOMO energies are dictated by the thienyl comonomers. Optical energy gaps ranging from 1.

Benzodichalcogenophenes with perfluoroarene termini.

Benzodichalcogenophenes are functionalized at their termini via SN Ar reactions of their bismetalates with perfluoroarenes. The identities of X, Y, and W are varied to study the effects on LUMO energy levels and crystallization motif. X-ray crystallography reveals that nearly all new derivatives crystallize with coplanar ring systems within slipped 1D or 2D pi-stacks.

Highly fluorinated benzobisbenzothiophenes.

Expedient, facile syntheses of highly fluorinated benzobisbenzothiophenes (BBBT) are reported. Defined peripheral arrangements of sulfur and fluorine atoms lead to extensive crystalline networks of edge-to-edge S-F close contacts. The effects of various substitution patterns on self-assembly and electronic properties are described.

Helical packing of discotic hexaphenyl hexa-peri-hexabenzocoronenes: theory and experiment.

The arrangement of discotic hexa-peri-hexabenzocoronenes (HBCs) into columnar helical superstructures has been investigated in relation to their molecular architecture. The supramolecular structure of two hexaphenyl-substituted HBC derivatives, differing only in the chiral/achiral nature of the attached alkyl side chains, was studied by circular dichroism and temperature-dependent wide-angle X-ray diffraction on oriented filaments. A structural model in agreement with the experimental observations was developed on the basis of accompanying quantum-chemical calculations.

Transition-metal-free synthesis of alternating thiophene-perfluoroarene copolymers.

The fluoride-activated coupling between silyl-functionalized thiophene monomers and perfluoroarenes leads to moderately high-molecular-weight alternating copolymers in excellent yields and high chemical purity. The method bypasses transition-metal catalysis and the associated need for perfluoroarenes carrying additional functional "handles". Small-molecule model studies provide insight into the relative reactivities of functional groups in this synthetic pathway.

Influence of molecular order on the local work function of nanographene architectures: a Kelvin-probe force microscopy study.

We report a Kelvin-probe force microscopy (KPFM) investigation on the structural and electronic properties of different submicron-scale supramolecular architectures of a synthetic nanographene, including extended layers, percolated networks and broken patterns grown from solutions at surfaces. This study made it possible to determine the local work function (WF) of the different pi-conjugated nanostructures adsorbed on mica with a resolution below 10 nm and 0.05 eV.

Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes.

We present structural studies of Langmuir (L) and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone). Grazing-incidence X-ray diffraction (GIXD) and X-ray reflectivity, both utilizing synchrotron radiation, show that these amphiphilic HBCs form well-defined Langmuir monolayers at the air-water interface, with a pi-stacked columnar structure where the HBC cores are rotated around the surface normal and tilted relative to the water surface.

High charge-carrier mobility in pi-deficient discotic mesogens: design and structure-property relationship.

Hexaazatrinaphthylene (HATNA) derivatives with six alkylsulfanyl chains of different length (hexyl, octyl, decyl and dodecyl) have been designed to obtain new potential electron-carrier materials. The electron-deficient nature of these compounds has been demonstrated by cyclic voltammetry. Their thermotropic behaviour has been studied by means of differential scanning calorimetry and polarised optical microscopy.

Partial fluorination overcomes herringbone crystal packing in small polycyclic aromatics.

[structure: see text] We report the synthesis and characterization of partially fluorinated condensed tetracyclic aromatic compounds. Typical edge-to-face/herringbone packing of nonfluorinated analogues is replaced here by columnar stacks with disk planes orthogonal to the columnar axes. Enhanced pi-overlap results with overlaid electron-poor and -rich regions.

Oligomers of hexa-peri-hexabenzocoronenes as "super-oligophenylenes": synthesis, electronic properties, and self-assembly.

Hexa-peri-hexabenzocoronene (HBC) is a remarkable polycyclic aromatic hydrocarbon and is often called "superbenzene" because of its similarity to benzene. In this article we present the facile synthesis of oligomers of HBC, up to trimers (3, 4, 5a-c) with different modes of connection. UV-vis and fluorescence spectroscopy studies reveal that the oligomers are electronically decoupled.

Controlled self-assembly of hexa-peri-hexabenzocoronenes in solution.

Disc-shaped hexa-peri-hexabenzocoronenes (HBCs) peripherally substituted by flexible dodecyl chains (molecule 1) or rigid polyphenylene dendrons (molecules 2a,b and 3) were efficiently synthesized. Steric hindrance arising from the substituents, from less hindered dodecyl to bulky dendrons, was utilized to program the self-assembly of the HBC cores in solution. The high tendency of the hexadodecyl-substituted HBC 1 to aggregate was determined by concentration and temperature-dependent (1)H NMR spectroscopic measurements and nonlinear least-squares analysis of the experimental data.

The optical and charge transport properties of discotic materials with large aromatic hydrocarbon cores.

The optical absorption and charge transport properties of a series of discotic molecules consisting of peripherally alkyl-substituted polycyclic aromatic cores have been investigated for core sizes, n, of 24, 42, 60, 78, 96, and 132 carbon atoms. In dilute solution, the wavelength maximum of the first absorption band increases linearly with n according to lambda(max) = 280 + 2n and the spectral features become increasingly broadened. The two smallest core compounds display a slight red-shift and increased spectral broadening in spin-coated films.

Self-assembly of electron donor-acceptor dyads into ordered architectures in two and three dimensions: surface patterning and columnar "double cables".

We report the synthesis and characterization of covalent dyads and multiads of electron acceptors (A) and donors (D), with the purpose of exploiting their nanophase separation behavior toward (a) two-dimensional (2D) surface patterning with well-defined integrated arrays of dissimilar molecular electronic features and (b) bulk self-assembly to noncovalent columnar versions of the so-called "double cable" systems, the likes of which could eventually provide side-by-side percolation pathways for electrons and holes in solar cells. Soluble, alkylated hexa-peri-hexabenzocoronenes (HBCs) bearing tethered anthraquinones (AQs) are shown by scanning tunneling microscopy (STM) to self-assemble at the solution-graphite interface into either defect-rich polycrystalline monolayers or extended 2D crystalline domains, depending on the number of tethered AQs. In the bulk, the thermal stability of the room-temperature HBC columnar phase is increased, which is attributed to the desired nanotriphase separation of HBC columns, insulating alkyl sheaths, and AQ units.

A hexa-peri-hexabenzocoronene cyclophane: an addition to the toolbox for molecular electronics.

Cyclophanes with the largest-to-date polycyclic aromatic hydrocarbon (hexa-peri-hexabenzocoronene, HBC) to be entrained in such a structural motif are reported. The two disks are covalently captured by intermolecular ring-closing olefin metathesis of dienes in good yield. DSC, optical microscopy, and WAXD show the new cyclophanes to self-assemble to thermotropic columnar liquid crystal mesophases similar to monomeric analogues.