Search

Aiming to obtain novel functional semiconducting materials for their use in organic electronics, the combination of strong donor moieties with electron-withdrawing units is one of the most useful strategies to obtain ambipolar semiconductors with tunable properties. Nowadays most of the efforts headed to efficient materials are based on small changes in the alkyl pendant chains or by replacing single atoms. However, a precise design of new functional materials is still challenging. For this reason, in this work we present a new synthetic approach for achieving redox amphoteric organic semiconductors by tuning their opto-electrochemical properties via rational chemical modifications. All these materials present low-lying LUMO levels, lower than −4.00 eV with broad absorption up to 800 nm in the UV-Vis-NIR spectra. In addition, they have been characterized by DFT, absorption and Raman vibrational spectroscopies, while their charge stabilization abilities are studied by means of spectroelectrochemical techniques. The results point out to a quite complex electronic scenario that goes beyond the expected cumulative effects of the independent molecular units constituting the final molecular assembly. [ABSTRACT FROM AUTHOR]

A new imine-based covalent organic framework (COF) functionalized in its cavities with moieties of the chromophore Nile Red has been synthesized and characterized. Using mechanical (ultrasonics) and chemical (acid-self-exfoliation) methods, exfoliation of the COF powder has been explored in water and water/organic media. In the latter, the obtained colloids exhibit dual emission originating from the Nile Red units (red) and the COF framework (green) that can be employed to prepare ratiometric sensors of polarity and acidity. Thus, taking advantage of the in situ exfoliation of the material in methacrylic monomers, free-standing polymeric films that preserve the optical properties of the exfoliated COF have been prepared. Finally, 3D liquid crystal display (LCD) additive manufacturing has been employed to prepare the dual emissive composites as tailored 3D-printed objects. [ABSTRACT FROM AUTHOR]

In this work, a series of nitrogen-doped polycyclic aromatic mono and dicarboximides was designed, and their synthesis is reported by an innovative synthetic procedure that avoids metal-based cross-coupling reactions. A combined theoretical, electrochemical, optical spectroscopy and material characterization study allows the investigation of the interplay of different effects such as (i) the type of solubilizing chain, (ii) the all-acceptor vs. donor–acceptor nature of the novel systems, and (iii) the molecular ordering, on the ability to stabilize multiple charges and on the OTFT device response characteristics. The amphoteric redox behavior of some of the novel systems allow to obtain ambipolar mobilities while the electron mobility values of the three all-acceptor systems can be rationalized in terms of supramolecular aggregation and enhanced film-forming ability. [ABSTRACT FROM AUTHOR]

A 1,1,2,2-tetrakis(4-aminophenyl)ethene with three paths of π-conjugation, linear-cis, linear-trans and a cross-conjugation, has been prepared. The molecule is able to bind to gold electrodes forming molecular junctions for single-molecule conductance measurements. Only two regimes of conduction are found experimentally. The modelling of the conductance allows to assign them to through-bond transmission in the linear case, while the cross-conjugated channel is further assisted by through-space transmission, partially alleviating the destructive quantum interference. [ABSTRACT FROM AUTHOR]

In this work, a series of naphthalimide fused thienopyrazine derivatives was designed, and their synthesis and characterization are reported herein. The interaction of this building block with a donor terthiophene fragment laterally substituted by a series of donor and acceptor constituents was analyzed in depth. This strategy was proven to efficiently modulate both the energy and topology of the frontier molecular orbitals involved in the charge transport mechanism. The interplay between the donor and acceptor strengths of the different units composing the material structure is thus essential to efficiently modulate charge carriers and transport properties and to finely tune the optical and electronic structures of the presented organic semiconductors. [ABSTRACT FROM AUTHOR]

A novel naphthalene diimide-based covalent organic framework (NDI-COF) has been synthesized and successfully exfoliated into COF nanosheets (CONs). Electrochemical measurements reveal that the naphthalene diimide units incorporated into NDI-CONs act as efficient electrocatalyst for oxygen reduction in alkaline media, showing its potential for the development of metal-free fuel cells. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are organic porous materials with many potential applications, which very often depend on the presence of chemical functionality at the organic building blocks. Functionality that cannot be introduced into COFs directly via de novo syntheses can be accessed through post-synthetic modification (PSM) strategies. Current strategies for the post-synthetic modification of COFs involve (i) incorporation of a variety of active metal species by using metal complexation through coordination chemistry, (ii) covalent bond formation between existing pendant groups and incoming constituents and (iii) chemical conversion of linkages. (iv) The post-synthetic modification is sometimes assisted by a monomer truncation strategy for the internal functionalization of COFs. (v) Even more intriguing methods that go beyond PSM are herein termed building block exchange (BBE) which encompasses framework-to-framework transformations taking advantage of the fact that reversible bond formation is a characteristic feature of COFs. This strategy allows the use of protoCOF structures (i.e., the utilization of a parent COF as a template) for the evolution of new COF structures with completely new components. [ABSTRACT FROM AUTHOR]

An imine-based covalent organic framework (COF) decorated in its cavities with uracil groups has shown selective recognition towards adenine in water. These results show how the confinement of the base-pair inside the COF's pores allows a remarkable selective recognition in aqueous media. [ABSTRACT FROM AUTHOR]

An imine-linked covalent organic framework ([HC≡C]0.5-TPB-DMTP-COF), endowed with reactive ethynyl groups on the walls of one-dimensional pores, has been used as a platform for pore-wall surface engineering with triazole and thiol groups to yield TPB-DMTP-COF-SH, which is suitable to interact very efficiently with mercury ions. The evaluation of the carefully designed TPB-DMTP-COF-SH is addressed as an effective and selective system for mercury sorption. The obtained results reveal an extraordinary capacity and a great efficiency of the polymeric material with a very high distribution coefficient value Kd = 3.23 × 109. Thus, the level of mercury of a highly concentrated aqueous solution, 10 mg L−1 of Hg(ii), is dramatically decreased, below the limits of what is considered to be drinking water, upon treatment with TPB-DMTP-COF-SH for a few minutes. The TPB-DMTP-COF-SH retention value of Hg(ii) from water is 99.98% within 2 minutes and its record uptake capacity is 4395 mg g−1 which represents the highest value reported so far. Besides TPB-DMTP-COF-SH captures other extremely toxic heavy metal ions such as Sn(ii) and Pb(ii) being quite selective versus Cd(ii) or As(iii). These results suggest that TPB-DMTP-COF-SH constitutes a realistic alternative for the remediation of contaminated spaces from an environmental perspective. [ABSTRACT FROM AUTHOR]

Covalent organic-frameworks (COFs) are an emerging class of porous and ordered materials formed by condensation reactions of organic molecules. Recently, the Schiff-base chemistry or dynamic imine-chemistry has been widely explored for the synthesis of COFs. The main reason for this new tendency is based on their high chemical stability, porosity and crystallinity in comparison to previously reported COFs. This critical review article summarizes the current state-of-the-art on the design principles and synthetic strategies toward COFs based on Schiff-base chemistry, collects and rationalizes their physicochemical properties, as well as aims to provide perspectives of potential applications which are at the forefront of research in materials science. [ABSTRACT FROM AUTHOR]

Dipyrazino[2,3-f:2′,3′-h]quinoxaline also known as 1,4,5,8,9,12-hexaazatriphenylene (HAT) is an electron deficient, rigid, planar, aromatic discotic system with an excellent π–π stacking ability. Because it is one of the smallest two-dimensional N-containing polyheterocyclic aromatic systems, it has been used as the basic scaffold for larger 2D N-substituted polyheterocyclic aromatics. Furthermore, it is the building block of choice in a plethora of molecular, macromolecular and supramolecular systems for a variety of applications. This review is aimed to critically review the research performed during the almost three decades of research based on HAT from the synthetic, theoretical and application points of view. The design principles and synthetic strategies towards HAT derivatives will be established and their use in n-type semiconductors, sensors, nonlinear optical chromophores, liquid crystals, microporous polymers for energy storage and nano and microstructures will reveal the relevance of HAT as a basic scaffold in the areas of organic materials and nanoscience. [ABSTRACT FROM AUTHOR]

A novel naphthalimide derivative endowed with a diketone functionality has been synthesized and used to develop a family of highly symmetric, flat, n-type semiconducting naphthalimide-based pyrazinacenes. By changing the symmetry of these compounds and the number of naphthalimide constituents, fine tuning of their electrochemical, photophysical, and morphological properties is achieved. [ABSTRACT FROM AUTHOR]

A PEDOT-based conductive copolymer soluble in organic solvents was synthesized electrochemically using dihexyl-EDOT and azidomethyl-EDOT as monomers and was successfully post-functionalized by "click"-cycloaddition reaction with a functionalized terminal alkyne under mild heterogeneous conditions., (This journal is © The Royal Society of Chemistry 2012)