Search

The bottom‐up synthesis of 3D tetrakis(hexa‐peri‐hexabenzocoronenyl)methane, "tetrahedraphene", is reported. This molecular nanographene constituted by four hexa‐peri‐hexabenzocoronene (HBC) units attached to a central sp3 carbon atom, shows a highly symmetric arrangement of the HBC units disposed in the apex of a tetrahedron. The X‐ray crystal structure reveals a tetrahedral symmetry of the molecule and the packing in the crystal is achieved mostly by CH⋅⋅⋅π interactions since the interstitial solvent molecules prevent the π⋅⋅⋅π interactions. In solution, tetrahedraphene shows the same electrochemical and photophysical properties as the hexa‐tBu‐substituted HBC (tBu‐HBC) molecule. However, upon water addition, it undergoes a fluorescence change in solution and in the precipitated solid, showing an aggregation induced emission (AIE) process, probably derived from the restriction in the rotation and/or vibration of the HBCs. Time‐Dependent Density Functional Theory (TDDFT) calculations reveal that upon aggregation, the high energy region of the emission band decreases in intensity, whereas the intensity of the red edge emission signal increases and presents a smoother decay, compared to the non‐aggregated molecule. All in all, the excellent correlation between our simulations and the experimental findings allows explaining the colour change observed in the different solutions upon increasing the water fraction. [ABSTRACT FROM AUTHOR]

The chemical reduction of π‐conjugated bilayer nanographene 1 (C138H120) with K and Rb in the presence of 18‐crown‐6 affords [K+(18‐crown‐6)(THF)2][{K+(18‐crown‐6)}2(THF)0.5][C138H1223−] (2) and [Rb+(18‐crown‐6)2][{Rb+(18‐crown‐6)}2(C138H1223−)] (3). Whereas K+ cations are fully solvent‐separated from the trianionic core thus affording a "naked" 1.3− anion, Rb+ cations are coordinated to the negatively charged layers of 1.3−. According to DFT calculations, the localization of the first two electrons in the helicene moiety leads to an unprecedented site‐specific hydrogenation process at the carbon atoms located on the edge of the helicene backbone. This uncommon reduction‐induced site‐specific hydrogenation provokes dramatic changes in the (electronic) structure of 1 as the helicene backbone becomes more compressed and twisted upon chemical reduction, which results in a clear slippage of the bilayers. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes between C60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C60. Time‐resolved transient absorption measurements on the ns‐time scale showed that the addition of C60 to NG‐1 solutions and photo‐exciting them at 460 nm leads to the solvent‐dependent formation of new species, in particular the formation of the one‐electron reduced form of C60 in benzonitrile was observed. [ABSTRACT FROM AUTHOR]

Keywords: Chemical reduction; DFT calculations; Helical bilayer; Hydrogenation; X-ray crystallography EN Chemical reduction DFT calculations Helical bilayer Hydrogenation X-ray crystallography 1 1 1 02/24/22 20220301 NES 220301 B Die reduktionsinduzierte b Hydrierung eines helikalen Doppelschicht-Nanographen (C SB 138 sb H SB 120 sb ) mit K oder Rb in 18-Krone-6 wird im Forschungsartikel von Israel Fernández, Marina A. Petrukhina, Nazario Martín et al. vorgestellt (e202115747). Rücktitelbild: Site-Specific Reduction-Induced Hydrogenation of a Helical Bilayer Nanographene with K and Rb Metals: Electron Multiaddition and Selective Rb+ Complexation (Angew. Chemical reduction, DFT calculations, Helical bilayer, Hydrogenation, X-ray crystallography. [Extracted from the article]

Reduction‐induced hydrogenation of a helical bilayer nanographene (C138H120) with K or Rb in 18‐crown‐6 is reported by Israel Fernández, Marina A. Petrukhina, Nazario Martín, and co‐workers in their Research Article (e202115747). DFT calculations predict that localization of the first two electrons in the helicene moiety leads to a site‐specific hydrogenation at the carbon atoms located on the edge of the central [6]helicene backbone (pink hydrogens). The third electron forms a radical trianion on the HBC leading to a final Rb complex. [ABSTRACT FROM AUTHOR]

The bottom-up synthesis of 3D tetrakis(hexa-peri-hexabenzocoronenyl)methane, "tetrahedraphene", is reported. This molecular nanographene constituted by four hexa-peri-hexabenzocoronene (HBC) units attached to a central sp 3 carbon atom, shows a highly symmetric arrangement of the HBC units disposed in the apex of a tetrahedron. The X-ray crystal structure reveals a tetrahedral symmetry of the molecule and the packing in the crystal is achieved mostly by CH⋅⋅⋅π interactions since the interstitial solvent molecules prevent the π⋅⋅⋅π interactions. In solution, tetrahedraphene shows the same electrochemical and photophysical properties as the hexa- t Bu-substituted HBC ( t Bu-HBC) molecule. However, upon water addition, it undergoes a fluorescence change in solution and in the precipitated solid, showing an aggregation induced emission (AIE) process, probably derived from the restriction in the rotation and/or vibration of the HBCs. Time-Dependent Density Functional Theory (TDDFT) calculations reveal that upon aggregation, the high energy region of the emission band decreases in intensity, whereas the intensity of the red edge emission signal increases and presents a smoother decay, compared to the non-aggregated molecule. All in all, the excellent correlation between our simulations and the experimental findings allows explaining the colour change observed in the different solutions upon increasing the water fraction., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The chemical reduction of π-conjugated bilayer nanographene 1 (C 138 H 120 ) with K and Rb in the presence of 18-crown-6 affords [K + (18-crown-6)(THF) 2 ][{K + (18-crown-6)} 2 (THF) 0.5 ][C 138 H 122 3- ] (2) and [Rb + (18-crown-6) 2 ][{Rb + (18-crown-6)} 2 (C 138 H 122 3- )] (3). Whereas K + cations are fully solvent-separated from the trianionic core thus affording a "naked" 1 .3 - anion, Rb + cations are coordinated to the negatively charged layers of 1 .3 - . According to DFT calculations, the localization of the first two electrons in the helicene moiety leads to an unprecedented site-specific hydrogenation process at the carbon atoms located on the edge of the helicene backbone. This uncommon reduction-induced site-specific hydrogenation provokes dramatic changes in the (electronic) structure of 1 as the helicene backbone becomes more compressed and twisted upon chemical reduction, which results in a clear slippage of the bilayers., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The formation of supramolecular complexes between C 60 and a molecular nanographene endowed with both positive and negative curvatures is described. The presence of a corannulene moiety and the saddle shape of the molecular nanographene allows the formation of complexes with 1:1, 1:2, and 2:1 stoichiometries. The association constants for the three possible supramolecular complexes were determined by 1 H NMR titration. Furthermore, the stability of the three complexes was calculated by theoretical methods that also predict the photoinduced electron transfer from the curved nanographene to the electron acceptor C 60 . Time-resolved transient absorption measurements on the ns-time scale showed that the addition of C 60 to NG-1 solutions and photo-exciting them at 460 nm leads to the solvent-dependent formation of new species, in particular the formation of the one-electron reduced form of C 60 in benzonitrile was observed., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)