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1.
Chemistry ; 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32608525

RESUMO

Three novel donor-π-bridge-donor (D-π-D) hole-transporting materials (HTMs) featuring triazatruxene electron-donating units bridged by different 3,4-ethylenedioxythiophene (EDOT) π-conjugated linkers have been synthesized, characterized, and implemented in mesoporous perovskite solar cells (PSCs). The opto-electronic properties of the new dumbbell-shaped derivatives (DTTXs) are highly influenced by the chemical structure of the EDOT-based linker. Red-shifted absorption and emission and a stronger donor ability were observed in passing from DTTX-1 to DTTX-2 due to the extended π-conjugation. DTTX-3 featured an intramolecular charge transfer between the external triazatruxene units and the azomethine-EDOT central scaffold, resulting in a more pronounced red shift. The three new derivatives have been tested in combination with the state-of-the-art triple-cation perovskite [(FAPbI3)0.87(MAPbBr3)0.13]0.92[CsPbI3]0.08 in standard mesoporous PSCs. Remarkable power conversion efficiencies of 17.48% and 18.30% were measured for DTTX-1 and DTTX-2, respectively, close to that measured for the benchmarking HTM spiro-OMeTAD (18.92%). PSCs with DTTX-3 reached a PCE value of 12.68%, which is attributed to the poorer film-formation in comparison to DTTX-1 and DTTX-2. These PCE values are in perfect agreement with the conductivity and hole mobility values determined for the new compounds and spiro-OMeTAD. Steady-state photoluminescence further confirm the potential of DTTX-1 and DTTX-2 for hole-transport applications as an alternative to spiro-OMeTAD.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32592432

RESUMO

The synthesis of radical polymers with control over chemical composition and structure is a milestone in materials science and has re-emerged recently because of the development of new synthetic methods to produce stable radical organic compounds. However, their synthesis is remarkably challenging due to the inherent reactivity induced by the presence of unpaired electrons in their structure. Here, we report on the synthesis and characterization of atomically precise one-dimensional diradical peripentacene polymers on a Au(111) surface. By means of high-resolution scanning probe microscopy complemented by theoretical simulations, we provide an evidence of their magnetic properties, which arise from the presence of two unpaired spins at their termini. In addition, we probe a transition of their magnetic properties related to the length of the polymer. Peripentacene dimers exhibit an antiferromagnetic (S = 0) singlet ground state. They are characterized by singlet-triplet spin-flip inelastic excitations with an effective exchange coupling (J eff ) of 2.5 meV, whereas trimers and longer peripentacene polymers reveal a paramagnetic nature and feature Kondo fingerprints at each terminus due to the unpaired spin. Our work provides access to the precise fabrication of polymers featuring diradical character and potentially useful in carbon-based optoelectronics and spintronics.

3.
J Mater Chem B ; 8(20): 4505-4515, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32369088

RESUMO

Non-viral nucleic acid vectors able to display high transfection efficiencies with low toxicity and overcoming the multiple biological barriers are needed to further develop the clinical applications of gene therapy. The synthesis of hexakis-adducts of [60]fullerene endowed with 12, 24 and 36 positive ammonium groups and a tridecafullerene appended with 120 positive charges has been performed. The delivery of a plasmid containing the green fluorescent protein (EGFP) gene into HEK293 (Human Embryonic Kidney) cells resulting in effective gene expression has demonstrated the efficacy of these compounds to form polyplexes with DNA. Particularly, giant tridecafullerene macromolecules have shown higher efficiency in the complexation and transfection of DNA. Thus, they can be considered as promising non-viral vectors for transfection purposes.

4.
Chemistry ; 26(29): 6292-6295, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32432399

RESUMO

This Special Issue of Chemistry-A European Journal is dedicated to the Chemical Functionalization of 2D Materials, and features some great contributions from experts in the field of 2D materials. This issue was originally assembled to support the Symposium G "Chemical Functionalization of 2D Materials" at the European Materials Research Society (E-MRS) 2020 Spring Meeting, which was originally scheduled to be held in Strasbourg, France, from May 25th to 29th, 2020. Although the E-MRS 2020 Spring Meeting has been cancelled due to the COVID-19 outbreak, the publication of this Special Issue has proceeded and has become even more important as the contributors discuss diverse and timely research themes related to 2D materials. In this Editorial, a brief overview of the different types of 2D materials is given, together with the chemical functionalization schemes that can be applied to them to achieve new properties as well as enable improved performance in applications. Some of the articles featured in this Special Issue are also highlighted, with the hope that they will inspire readers and further advance the field.

5.
Nat Nanotechnol ; 15(6): 437-443, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32313219

RESUMO

Topological band theory predicts that a topological electronic phase transition between two insulators must proceed via closure of the electronic gap. Here, we use this transition to circumvent the instability of metallic phases in π-conjugated one-dimensional (1D) polymers. By means of density functional theory, tight-binding and GW calculations, we predict polymers near the topological transition from a trivial to a non-trivial quantum phase. We then use on-surface synthesis with custom-designed precursors to make polymers consisting of 1D linearly bridged acene moieties, which feature narrow bandgaps and in-gap zero-energy edge states when in the topologically non-trivial phase close to the topological transition point. We also reveal the fundamental connection between topological classes and resonant forms of 1D π-conjugated polymers.

6.
J Org Chem ; 85(4): 2426-2437, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-31922748

RESUMO

The reaction of C60 with pregnen-20-carboxaldehyde, a biologically active synthetic steroid, by using a 1,3-dipolar cycloaddition reaction (Prato's protocol) results in the formation of pyrrolidine rings bearing a new stereogenic center on the C2 of the five-membered ring. The formation of the fullerene-steroid hybrids proceeds with preference for the Re face of the 1,3-dipole, with formation of a diastereomeric mixture in 73:15 ratio. The investigation of the chiroptical properties of these conjugates allowed determining the absolute configuration of the new fulleropyrrolidines. In addition, a thorough spectroscopical study permitted to determine the structure of the two mono-cycloadducts. The electrochemical properties of the new hybrids were also evaluated by cyclic voltammetry, both systems exhibit three quasi-reversible reduction waves which are cathodically shifted in regard to the parent C60. Theoretical calculations help supporting the experimental data. A conformational study combining semiempirical methods and density functional theory has predicted the most stable diastereomer. On the basis of this agreement, a possible reaction mechanism is presented. Additionally, a molecular docking simulation has been carried out using the HIV-1 protease as receptor, thus paving the way to study the possible application of these stereoisomers in biomedicine.

7.
Nanoscale ; 12(6): 3614-3622, 2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-31912074

RESUMO

Water soluble 2D crystalline monolayers of fullerenes grow on planar assemblies of engineered consensus tetratricopeptide repeat proteins. Designed fullerene-coordinating tyrosine clamps on the protein introduce specific fullerene binding sites, which facilitate fullerene nucleation. Through reciprocal interactions between the components, the hybrid material assembles into two-dimensional 2 nm thick structures with crystalline order, that conduct photo-generated charges. Thus, the protein-fullerene hybrid material is a demonstration of the developments toward functional materials with protein-based precision control of functional elements.

8.
J Org Chem ; 85(1): 224-233, 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31760753

RESUMO

Three hole-transporting materials (HTMs) were prepared following a straightforward synthetic route by cross-linking arylamine-based ligands with a simple thieno[3,2-b]thiophene (TbT) core. The novel HTMs were fully characterized with standard techniques to gain insight into their optical and electrochemical properties and were incorporated in solution-processed mesoporous (FAPbI3)0.85(MAPbBr3)0.15 perovskite-based solar cells. The similar molecular structure of the synthesized HTMs was leveraged to investigate the role that the bridging units between the conjugated TbT core and the peripheral arylamine units plays on their properties and thereby on the photovoltaic response. A remarkable power conversion efficiency exceeding 18% was achieved for one of the TbT derivatives, which was slightly higher than the value measured for the benchmark spiro-OMeTAD.

9.
J Am Chem Soc ; 142(4): 1895-1903, 2020 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-31876150

RESUMO

A series of molecular precursors, containing one (1 and 3) or three (2 and 4) pyrene anchors, covalently linked to porphyrins (free base or Zn), were prepared and characterized. All of them enable their π-π stacking onto low-dimensional nanocarbons including single-walled carbon nanotubes (SWCNTs) and nanographene (NG), their individualization, and their characterization. Microscopic (TEM, AFM) and spectroscopic (steady-state UV-vis and fluorescence, spectroelectrochemistry, and transient absorption measurements) techniques were at the forefront of the characterizations and were complemented by Raman spectroscopy and theoretical calculations. Of great importance is the Raman analysis, which corroborated n-doping of the nanocarbons due to the interactions with 1-4 when probed in the solid state. In solution, the situation is, however, quite different. Efficient charge separation was only observed for the graphene-based system NG/3.

10.
J Am Chem Soc ; 142(9): 4162-4172, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-31859500

RESUMO

Two novel homo and hetero three-dimensional nanographenes, NG1 and NG2, featuring a cyclooctatetraene core are designed, synthesized, and characterized. A concise and efficient bottom-up methodology was employed during which 24 new carbon-carbon bonds were formed. By means of a Scholl reaction nanographenes with 53 fused rings are realized, which exhibited good solubility in common organic solvents. The resulting saddle-like structures of NG1 and NG2 are electron-rich and show good chemical and electrochemical stability. Their molecular structures are fully elucidated by single-crystal X-ray crystallography. From their crystal structure analysis is concluded that both nanographenes are chiral and crystallize as a racemic mixture. Our work was rounded-off by excited state investigations such as electron and energy transfer with electron-acceptors and -donors.

12.
Angew Chem Int Ed Engl ; 58(45): 16097-16100, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31550074

RESUMO

Induced π acidity from polarizability is emerging as the most effective way to stabilize anionic transition states on aromatic π surfaces, that is, anion-π catalysis. To access extreme polarizability, we propose a shift from homogeneous toward heterogeneous anion-π catalysis on higher carbon allotropes. According to benchmark enolate addition chemistry, multi-walled carbon nanotubes equipped with tertiary amine bases outperform single-walled carbon nanotubes. This is consistent with the polarizability of the former not only along but also between the tubes. Inactivation by π-basic aromatics and saturation with increasing catalyst concentration support that catalysis occurs on the π surface of the tubes. Increasing rate and selectivity of existing anion-π catalysts on the surface of unmodified nanotubes is consistent with transition-state stabilization by electron sharing into the tubes, i.e., induced anion-π interactions. On pristine tubes, anion-π catalysis is realized by non-covalent interfacing with π-basic pyrenes.

13.
J Am Chem Soc ; 141(38): 15403-15412, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31469952

RESUMO

After the last epidemic of the Zika virus (ZIKV) in Brazil that peaked in 2016, growing evidence has been demonstrated of the link between this teratogenic flavivirus and microcephaly cases. However, no vaccine or antiviral drug has been approved yet. ZIKV and Dengue viruses (DENV) entry to the host cell takes place through several receptors, including dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), so that the blockade of this receptor through multivalent glycoconjugates supposes a promising biological target to inhibit the infection process. In order to get enhanced multivalency in biocompatible systems, tridecafullerenes appended with up to 360 1,2-mannobiosides have been synthesized using a strain-promoted cycloaddition of azides to alkynes (SPAAC) strategy. These systems have been tested against ZIKV and DENV infection, showing an outstanding activity in the picomolar range.

14.
Acc Chem Res ; 52(6): 1565-1574, 2019 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-31181912

RESUMO

Chirality is a fascinating property present in naturally occurring and artificial molecules and materials, observable as chiroptical behavior. The emerging area of carbon nanostructures has undergone tremendous development, with a wide variety of carbon nanoforms reported over the last two decades. However, despite interest in merging chirality and nanocarbons, this has been successfully achieved only in empty fullerenes, whereas in other kinds of fullerenes or carbon nanostructures such as carbon nanotubes, graphene, and graphene quantum dots (GQDs), to name the most popular systems, it is almost unknown. Therefore, controlling chirality in carbon nanostructures currently represents a major challenge for the chemical community. In this Account, we show our progress in the synthesis of chiral molecular carbon nanostructures, namely, metallofullerenes, endohedral fullerenes, GQDs, and curved molecular nanographenes, by using asymmetric catalysis and both top-down and bottom-up chemical approaches. Furthermore, we bring in a new family of lesser-known molecular chiral bilayer nanographenes, where chirality is introduced from the starting helicene moiety and a single enantiomer of the nanographene is synthesized. Some important landmarks in the development of chiral molecular carbon nanostructures shown in this Account are the application of synthesis-tailored, enantiomerically pure metallofullerenes as catalysts for hydrogen transfer reactions and the use of endohedral fullerenes to determine the effect of the incarcerated molecule in the carbon cage on the cis-trans stereoisomerization of optically active pendent moieties. Furthermore, the first top-down synthesis of chiral GQDs by functionalization with chiral alcohols is also presented. An emerging alternative to GQDs, when the desire for purity and atomistic control outweighs the cost of multistep synthesis, is the bottom-up approach, in which molecular nanographenes are formed in precise sizes and shapes and enantiomeric control is feasible. In this regard, a singular and amazing example is given by our synthesis of a single enantiomer of the first chiral bilayer nanographene, which formally represents a new family of molecular nanographenes with chirality controlled and maintained throughout their syntheses. The aforementioned synthetic chiral nanostructures represent groundbreaking nanocarbon systems where chirality is a further dimension of structural control, paving the way to a new scenario for carbon nanoforms in which chirality selection determines the properties of these novel carbon-based materials. Fine-tuning of such properties is envisioned to impact biomedical and materials science applications.

15.
Phys Chem Chem Phys ; 21(22): 11670-11675, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31125037

RESUMO

A new series of fullerene receptors based on exTTF macrocycles with alkyl ether chains of increasing length is reported. The novel macrocyclic receptors are able to favourably interact with fullerene C60 through a synergistic combination of π-π, CHπ and nπ noncovalent interactions. We identify that the highest affinity towards C60 recognition is achieved for the host with the tightest fit; that is, the smallest receptor with a cavity large enough to host the buckyball inside (log Ka = 5.2 in chlorobenzene at 298 K). However, besides this expected observation, theoretical calculations evidence that the most stable self-assembling configuration corresponds for all the receptors to an outside-ring binding mode, in which the C60 guest is out of the cavity of the receptor. The higher stability of this configuration results from the smaller deformation energy it implies for the receptor, and allows to explain the experimental trends in the association constants.

16.
Angew Chem Int Ed Engl ; 58(21): 6932-6937, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30835927

RESUMO

The synthesis and characterization of a covalent all-fullerene C60 -Lu3 N@Ih -C80 electron donor-acceptor conjugate has been realized by sequential 1,3-dipolar cycloaddition reactions of azomethine ylides on Lu3 N@Ih -C80 and C60 . To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu3 N@Ih -C80 ) and acceptor (C60 ) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 with syn and 8 with anti orientation, with the anti-RSSS isomer being the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C60 ⋅- -Lu3 N@Ih -C80 ⋅+ charge-separated state is formed. Spin conversion from the charge-separated singlet state C60 ⋅- -Lu3 N@Ih -C80 ⋅+ into the corresponding triplet state is facilitated by the heavy-atom effect stemming from the Lu3 N-cluster, which, in turn, slows down the charge recombination by one order of magnitude.

17.
Chem Commun (Camb) ; 55(22): 3223-3226, 2019 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-30806381

RESUMO

Water-soluble fluorescent graphene quantum dots have been successfully prepared through a top-down approach, that is, starting with graphite, and covalently functionalizing it with π-extended tetrathiafulvalene. Charge transfer investigations reveal noticeably slower charge recombination when compared with exTTF nanoconjugates featuring carbon nanodots, for which a larger presence of trap states is observed.

18.
Angew Chem Int Ed Engl ; 58(20): 6559-6563, 2019 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-30761719

RESUMO

Engineering low-band-gap π-conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on-surface synthesis protocol to overcome such difficulties and produce poly(p-anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400 K, resulting in anthracene-based polymers. High-resolution nc-AFM measurements confirm the nature of the ethynylene-bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface-stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π-conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on-surface synthesis.

19.
Chemistry ; 25(13): 3224-3228, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30657215

RESUMO

We report on the site-selective synthesis of PCBM-like [70]fullerene site-isomers, where the elusive ß-site-isomers are, for the first time, the major product in a (cyclo)addition chemical reaction involving [70]fullerene. The reaction involves an straightforward cyclopropanation of [70]fullerene from sulfonium salts, affording a mixture of α and ß site-isomers in good yields. Amazingly, the preference for the α- or ß-site-isomer can be efficiently controlled by means of the solvent polarity! DFT theoretical calculations (DMF and toluene) nicely predict that, although the formation of the α-adduct is, as expected, thermodynamically favored, the selectivity of the process is determined by the energy difference of the respective transition states. Furthermore, the employ of α or/and ß site-isomers, as pure materials or as a mixture of them, used as templating agent, has been evaluated in perovskite solar cells. The positive influence of the [70]fullerenes by passivating the voids/pin-holes and/or deep slits, is reflected in highly efficient and stable bulk heterojunction perovskite solar cells, whose performance (around 20 %) is slightly but consistently depending on the isomeric fullerene composition. These experimental findings pave the way to investigate a new reactivity on C70 and to explore the properties of the less-known ß-derivatives.

20.
Angew Chem Int Ed Engl ; 58(8): 2310-2315, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30549401

RESUMO

Engineering high-recognition host-guest materials is a burgeoning area in basic and applied research. The challenge of exploring novel porous materials with advanced functionalities prompted us to develop dynamic crystalline structures promoted by soft interactions. The first example of a pure molecular dynamic crystalline framework is demonstrated, which is held together by means of weak "sticky fingers" van der Waals interactions. The presented organic-fullerene-based material exhibits a non-porous dynamic crystalline structure capable of undergoing single-crystal-to-single-crystal reactions. Exposure to hydrazine vapors induces structural and chemical changes that manifest as toposelective hydrogenation of alternating rings on the surface of the [60]fullerene. Control experiments confirm that the same reaction does not occur when performed in solution. Easy-to-detect changes in the macroscopic properties of the sample suggest utility as molecular sensors or energy-storage materials.

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