Suchergebnisse

A new persistent organic free radical has been synthetized with Br atoms occupying the ortho‐ and para‐positions of a trityl core. After the isolation of its two propeller‐like atropisomers, Plus (P) and minus (M), their absolute configurations were assigned by a combination of theoretical and experimental data. Remarkably, no hints of racemization were observed up to 60 °C for more than two hours, due to the higher steric hindrance imposed by the bulky Br atoms. Therefore, when compared to its chlorinated homologue (t1/2=18 s at 60 °C), an outstanding stability against racemization was achieved. A circularly polarized luminescence (CPL) response of both enantiomers was detected. This free radical shows a satisfactory luminescent dissymmetry factor (|glum(592 nm)|≈0.7×10−3) despite its pure organic nature and low luminescence quantum yield (LQY). Improved organic magnetic CPL emitters derived from the reported structure can be envisaged thanks to the wide possibilities that Br atoms at para‐positions offer for further functionalization. ; The authors are grateful for the financial support received from: MOTHER project (MAT2016-80826-R) granted by the DGI (Spain), GenCat (2017-SGR-918) financed by DGR (Catalunya) and the Spanish Ministry of Economy and Competitiveness (PGC2018-095808-B-I00 and PGC2018-101181-B-I00 projects) and through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2015-0496) and through the "Proyecto Interdisciplinar de Frontera", FIP-2018 HECTIC-PTM. We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023). This study has been also supported by the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. P. M. B. gratefully acknowledges financial support from the Juan de la Cierva-Formación 2015 programme (FJCI-2015-23577) supported by MINECO and, together with J.V, A. G. C. also thanks RyC-2013-12943 contract from MINECO. We also thankthe Servei de Ressonància Magnètica Nuclear, Universitat Autònoma de Barcelona, for allocating instrument time to this project.

Chiroptical properties of two chiral atropisomers of propeller‐like trityl‐based radical derivatives have been analyzed. A new absolute configuration (AC) assignment has been made, according to the combination of experimental and theoretical data. In this sense, their ACs have been determined through the comparison of the Cotton effects recorded by electronic circular dichroism (ECD) with the theoretical ECD of the open shell structures obtained by TD‐DFT calculations. Finally, their circularly polarized luminescence (CPL) responses have been addressed. Remarkably, this is the first description of organic free radicals as intrinsic CPL emitters. Opposite signed CPL has been detected for each pair of conformers, with acceptable luminescent dissymmetry factors (|glum|≈0.5–0.8×10−3) considering their pure organic nature. In fact, highly efficient chiral emissions have been demonstrated, according to the comparison of |glum| with their respective absorption anisotropy factors (|gabs|). This pioneering study lays the foundations for the optimization of new magnetically active organic chiral emitters. ; The authors are grateful for the financial support received from: MOTHER (MAT2016-80826-R) granted by the DGI (Spain), GenCat (2017-SGR-918) financed by DGR (Catalunya) and the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2015-0496) and through the "Proyecto interdisciplinar de frontera", FIP-2018 HECTIC-PTM. We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023). This study has been also supported by the Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. P. M. B. gratefully acknowledges financial support from the Juan de la Cierva-Formación 2015 programme (FJCI-2015-23577) supported by MINECO. A. G. C. also thanks RyC-2013-12943 contract from MINECO. We also acknowledge Prof. O. Trapp for kindly suppling the DCxplorer software.

A cyclophane incorporating two units of a heptagoncontaining extended polycyclic aromatic hydrocarbon (PAH), analogue of the hexa-peri-hexabenzocoronene (HBC) moiety (hept- HBC), is reported. This cyclophane represents a new class of macrocyclic structures that incorporate for the first time sevenmembered rings within extended PAH frameworks. The saddle curvature of the hept-HBC macrocycle units induced by the presence of the non-hexagonal ring along with the flexible alkyl linkers generate a cavity with shape complementarity and appropriate size to enable  interactions with fullerenes. Therefore, the cyclophane forms host-guest complexes with C60 and C70 with estimated binding constants of Ka = 420 ± 2 M-1 and Ka = (6.49 ±0.23) × 103M-1 respectively. As a result, the macrocycle can selectively bind C70 in the presence of an excess of a mixture of C60 and C70. ; We acknowledge Junta de Andalucía (A-FQM-339-UGR18, Programa Operativo FEDER 2014-2020, Consejería de Economía y Conocimiento), the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC‐2015‐STG‐677023), Ministerio de Ciencia, Innovación y Universidades (MICIU/FEDER/AEI, Spain; PGC2018 ‐ 101181 ‐ B ‐ I00) and Universidad de Granada (UGR) (Visiting Scholars PP2016-VS01 and "Intensificación de la Investigación" PP2017-PRI-I-02 programmes from the "Plan Propio de Investigación") for financial support. We thank the CSIRC-Alhambra, Universidad de Granada, for providing supercomputing facilities and time

This feature article focuses on the bottom-up approaches (solution-phase) based on organic synthesis for the preparation of saddle-shaped distorted polycyclic aromatic hydrocarbons (PAHs). We summarise the recent progress on the synthetic strategies followed to obtain well-defined nanographenes containing heptagonal and octagonal carbocycles, highlighting the novel strategy developed by our group together with our recent contributions in the area of distorted aromatics. The presence of seven- or eight-membered rings induces a saddle-shape curvature in the planar network pushing the structure out of the plane, which influences the physical properties exhibited. Some brief details on the optical and electronic properties of these curved nanostructures are also discussed. ; The European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023) and the Ministerio de Economía y Competitividad (MINECO, Spain) (CTQ2015-70283-P).

We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023 and ERC-2013-SYG-610256 NANOCOSMOS) and the innovation program under grant agreement No. 696656 (GrapheneCore1-Graphene-based disruptive technologies) and grant agreement No. 785219 (GrapheneCore2-Graphene-based disruptive technologies) for financial support. Grants PGC2018-101181-B-I00 and MAT2017-85089-C2-1-R funded by MCIN/AEI/ 10.13039/501100011033 and "ERDF A way of making Europe" by the "European Union", and grant PID2020-113142RB-C21 funded by MCIN/AEI/ 10.13039/501100 011033 also provided financial support. We also acknowledge Comunidad de Madrid via Programa de Investigación Tecnologías 2018 (FOTOART-CM S2018/NMT-4367), the Swiss National Science Foundation (grant number 200020-182015), the NCCR MARVEL funded by the Swiss National Science Foundation (grant number 51NF40-182892) and FEDER/Junta de Andalucía-Consejería de Economía y Conocimiento (B-FQM-428-UGR20). C. S. S. and N. R. A. acknowledge Grants RYC2018-024364-I and BES-2015-072642, respectively, funded by MCIN/AEI/ 10.13039/501100011033 and "ESF Investing in your future". I. R. M. acknowledges the University of Granada for her postdoctoral contract (Contrato Puente-Plan Propio UGR). F.V. thanks Ministerio de Universidades for the FPU grant (FPU18/05938). ; On-surface synthesis, complementary to wet chemistry, has been demonstrated to be a valid approach for the synthesis of tailored graphenic nanostructures with atomic precision. Among the different existing strategies used to tune the optoelectronic and magnetic properties of these nanostructures, the introduction of non-hexagonal rings inducing out-of-plane distortions is a promising pathway that has been scarcely explored on surfaces. Here, we demonstrate that non-hexagonal rings, in the form of tropone (cycloheptatrienone) moieties, are thermally transformed into phenyl or cyclopentadienone moieties upon an unprecedented surface-mediated retro–Buchner-type reaction involving a decarbonylation or an intramolecular rearrangement of the CO unit, respectively. ; Junta de Andalucía-Consejería de Economía y Conocimiento B-FQM-428-UGR20, BES-2015-072642, RYC2018-024364-I ; MCIN ; Ministerio de Universidades FPU18/05938 ; European Commission FOTOART-CM S2018/NMT-4367 ; European Research Council ; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung 200020-182015 ; European Social Fund ; Universidad de Granada ; European Regional Development Fund 011033, PID2020-113142RB-C21, S2018/NMT-4367 ; National Center of Competence in Research Materials' Revolution: Computational Design and Discovery of Novel Materials 51NF40-182892 ; Agencia Estatal de Investigación

This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreements No. 716139 and No. 677023), the Swiss National Science Foundation (SNSF, PP00P2_170534, PP00P2_198900), Project PGC2018-101181-B-I00 funded by MCIN/AEI/ 10.13039/501100011033 FEDER "Una manera de hacer Europa", grant A-FQM-230-UGR20 funded by FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades and the German Academic Exchange Service (DAAD, postdoc fellowship to D. G.). Open access funding provided by the University of Zurich. ; We present the concept of combining circularly polarized luminescence (CPL) and excited-state intramolecular proton transfer (ESIPT) features into a single molecule as a strategy to generate high-performance ESIPT-based CPL materials. For this purpose, a [6]helicene bearing two ESIPT structural units was synthesized using a double Suzuki-Miyaura reaction and a double C(sp(2))-H hydroxylation approach. The photophysical properties of the doubly hydroxylated [6]helicene were studied in parallel with a non-hydroxylated [6]helicene control compound, revealing that the presence of a chiral [6]helicene unit results in a strong CPL response and the presence of the ESIPT units in a considerable red shift. The red-shifted emission along with the outstanding g(lum) (approximate to 10(-2)) and a large Stokes shift makes the doubly hydroxylated [6]helicene a promising candidate for use in optoelectronics. ; European Research Council (ERC) 716139 677023 ; Swiss National Science Foundation (SNSF) PP00P2_170534 PP00P2_198900 ; Deutscher Akademischer Austausch Dienst (DAAD) ; University of Zurich ; MCIN/AEI FEDER "Una manera de hacer Europa" PGC2018-101181-B-I00 ; FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades A-FQM-230-UGR20

A unique rippled nanographene constituted by 52 fused rings is presented in which six out-of-plane motifs are fully fused into a triangular aromatic surface of ca. 2.5 nm size. Three units of an unprecedented fully lateral π-extended octabenzo[5]helicene together with three units of saddle-shaped heptagonal rings are combined in a single structure leading to a well-soluble warped nanographene. The two pairs of possible enantiomers have been isolated and their linear, non-linear and chiroptical properties evaluated, revealing an outstanding quantum yield and brightness values at low energy together with good chiroptical responses both in the absorption and emission ; We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023) and the Ministerio de Economía y Competitividad (MINECO, Spain) (CTQ2015-70283- P, UNGR15-CE-3478, BES-2016-076371 and RyC-2013-12943). E.M. thanks the Fundação para a Ciência e a tecnologia (PTDC/NAN-MAT729317/2017 and PTDC/QUI-QFI/29319/2017). We thank the CSIRC-Alhambra from the University of Granada.

We acknowledge the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023), the Ministerio de Ciencia, Innovacion y Universidades (MICIU/FEDER/AEI, Spain, PGC2018-101181-B-I00), the Universidad de Granada (UGR) (Plan Propio - Intensificacion de la Investigacion PP2017-PRI.I-02) and the Swiss National Science Foundation (Spark 2019 Grant CRSK-2_190365) for financial support. We thank the CSIRC-Alhambra, the Service and Support for Science IT (S3IT) of the University of Zurich and Prof.Dr. Michal Juriek for supercomputing facilities. Funding for open access charge: Universidad de Granada/CBUA. ; A new family of chiral saddle-helix hybrid nanographenes is reported. The first hexa-peri-hexabenzocoronene (HBC) analogues bearing a nine-membered carbocycle are presented. Furthermore, for the first time, pi-extended carbo[n]helicenes containing a nine-membered ring as part of the helical moiety have been synthesized. The combination of a [5]helicene moiety and a nonagon ring in a single chiral motif induces a tremendous distortion from planarity into the nanographenic structures compared to other saddle-helix hybrids such as heptagon- and octagon-containing pi-extended carbo[5]helicenes. In fact, the interplanar angle of the two terminal rings reaches the largest angle (134.8 degrees) of a carbohelicene reported to date, thus being by far the most twisted helicene yet prepared. Photophysical properties evaluation showed improved absorption dissymmetry factors (|g(abs)|=4.2x10(-3)) in the new family of nonagon-containing pi-extended carbo[5]helicenes. ; European Research Council (ERC) ERC-2015-STG-677023 ; Ministerio de Ciencia, Innovacion y Universidades (MICIU/FEDER/AEI, Spain) PGC2018-101181-B-I00 ; Universidad de Granada (UGR) (Plan Propio - Intensificacion de la Investigacion) PP2017-PRI.I-02 ; Swiss National Science Foundation (SNSF) European Commission CRSK-2_190365 ; Universidad de Granada/CBUA

A new family of distorted ribbon-shape nanographenes was designed, synthesized and their optical and electrochemical properties were measured, pointing out an unprecedented correlation between their structural characteristics and their two photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven-membered ring containing nanographene presenting a tropone moiety at the edge, its full-carbon analogue and the purely hexagonal one. We have found that the TPA cross-sections and the electrochemical band gaps of the seven-membered ring containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the difference between presenting or not the electron withdrawing group, barely changes these parameters compared with those of the nanoribbon without the heptagon. ; -European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023) -Ministerio de Ciencia Innovación y Universidades (PGC2018-101181-B-I00) -Ministerio de Economía y Competitividad (BES-2016-076371 and RyC-2013-12943).

This review highlights the recent applications of titanocene(III) complexes in the field of natural product synthesis from the seminal precedents to the development of modern catalytic methods. The power of the titanocene(III)-based approaches is demonstrated by the straightforward syntheses of many natural products from readily available starting materials. ; We thank the Regional Government of Andalucía (project P09-FQM-4571), MICINN (project CTQ-2011.22455), and CEI-Biotic for financial support. SPM thanks the Regional Government of Andalucía for her FPI fellowship. DM and AGC thank the Regional Government of Andalucía and the MICINN ( Juan de la Cierva) for their postdoctoral contracts.

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fchem. 2020.00306/full#supplementary-material ; In this work we describe the linear and non-linear (chiro)optical properties of an enantiopure bis-perylenediimide (PDI) cyclohexane derivative. This compound exhibits upconversion based on a two-photon absorption (TPA) process with a cross-section value of 70 GM together with emission of circularly polarized luminescence (CPL), showing a glum in the range of 10−3. This simple structure represents one of the scarce examples of purely organic compounds combining both TPA and CPL responses, together with large values of molar absorptivity and fluorescence quantum yield with emission in the 500–600 nm. Self-assembly induced by introduction of a poor solvent allows for a spectacular shift of the emission into the near-infrared (NIR, 650–750 nm) by formation of well-defined rotationally displaced dimers. Therefore, we are here presenting a versatile platform whose optical properties can be simply tuned by self-assembly or by functionalization of the electron-deficient aromatic core of PDIs. ; Ministerio de Ciencia, Innovacion y Universidades PG2018-101181-B-I00 ; Spanish Government CTQ2017-85454-C2-1-P ; European Research Council (ERC) ERC-2015-STG-677023 ; MINECO RyC-2013-12943 ; Spanish Government ; Portuguese Foundation for Science and Technology ; POCI ; European Union (EU) PTDC/NAN-MAT/29317/2017 PTDC/QUI-QFI/29319/2017 UIDB/00100/2020

This is accepted manuscript, the final published article is available in "García Jiménez, V.; et al. Aggregation-induced emission of [3]cumulenes functionalized with heptagon-containing polyphenylenes. Chemical Communications, online (2018). DOI: http://dx.doi.org/10.1039/C8CC00386F ; We report the luminiscence at room temperature by aggregate formation of [3]cumulenes functionalized with propeller-like heptagon-containing polyphenylenes. These endgroups turn on the emission of a [3]cumulene by steric protection and restriction of their intramolecular rotations in the aggregates. ; European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015 -677023). ; Ministerio de Economía y Competitividad (MINECO, Spain – FEDER) (CTQ2015-70283-P, CTQ2014-53598-R, RyC-2013-12943). ; Fundação para a Ciência e a tecnologia (Portugal, IF/00759/2013, SFRH/BPD/75782/2011,SFRH/BPD/96707/2013,UID/NAN/50024/2013).

Herein we describe a distorted ribbon-shaped nanographene exhibiting unprecedented combination of optical properties in graphene-related materials, namely upconversion based on two-photon absorption (TPA-UC) together with circularly polarized luminescence (CPL). The compound is a graphene molecule of ca. 2 nm length and 1 nm width with edge defects that promote the distortion of the otherwise planar lattice. The edge defects are an aromatic saddle-shaped ketone unit and a [5]carbohelicene moiety. This system is shown to combine two-photon absorption and circularly polarized luminescence and a remarkably long emission lifetime of 21.5 ns. The [5]helicene is responsible for the chiroptical activity while the push–pull geometry and the extended network of sp2 carbons are factors favoring the nonlinear absorption. Electronic structure theoretical calculations support the interpretation of the results. ; This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-2015-STG-677023). We also thank the Ministerio de Economía y Competitividad (MINECO, Spain) (CTQ2015-70283-P, CTQ2014-53598-R, MAT2014-54231-C4-1P, FIS2016-77578-R) and the "Unidad de Excelencia Química Aplicada a Biomedicina y Medioambiente (UGR)". A. G. C., C. S. S. and C. M. C. acknowledge funding from MINECO (Spain) for RyC-2013-12943, IJCI-2014-19291 and BES-2016-076371 contracts, respectively. I. R. M. thanks UGR (Spain) for a postdoctoral scholarship. I. M. and E. M. thank the Fundação para a Ciência e a Tecnologia for financial support (IF/00759/2013 and post-doc grant SFRH/BPD/75782/2011). We thank the CSIRC-Alhambra for supercomputing facilities.