Photoreduction of Anthracenes Catalyzed by peri-Xanthenoxanthene: a Scalable and Sustainable Birch-type Alternative

C. De Luca, D. Zanetti, T. Battisti, R. R. Ferreira, S. Lopez, A. H. McMillan, S. C. Lesher-Pérez, L. Maggini, D. Bonifazi. Chem. Eur. J. 2023, e202302129. DOI: https://doi.org/10.1002/chem.202302129. Abstract: The typical Birch reduction transforms arenes into 1,4-cyclohexadienes using alkali metals, an alcohol as a proton source, and an amine as solvent. Capitalizing on the strong photoreductive properties of peri-xanthenoxanthene (PXX), herein we report the photocatalyzed “Birch-type” reduction of acenes employing visible blue light irradiation at room temperature in the presence of air. Upon excitation at 405 or 460 nm in the presence of a mixture of N,N-diisopropylethylamine (DIPEA)and trifluoromethanesulfonimide (HNTf2) in DMSO, PXX photocatalyzes the selective reduction of full-carbon acene derivatives (24–75%). Immobilization of PXX onto polydimethylsiloxane (PDMS) beads (PXX-PDMS) allowed the use of the catalyst in heterogeneous batch reactions, yielding 9-phenyl-9,10-dihydroanthracene in high yields (68%). The catalyst could be easily recovered and reused, with no notable catalytic performance drop observed after five reaction cycles. Integration of the PXX-PDMS beads into a microreactor enabled the reduction of acenes under continuous flow conditions, there by validating the sustainability and scalability of this heterogeneous phase approach.

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HOMO Energy-Level Lifting in p-Type O-Doped Graphenoids: Synthesis of Electrochromic Alkoxy-Decorated Xanthenoxanthenes

A. Rossignon, B. B. Berna, A. J. Parola, C. A. T. Laia D. Bonifazi. Organic Materials 2022, 4, 240–254. DOI: 10.1055/a-1976-0291. Abstract: A series of novel O-doped polycyclic aromatic hydrocarbons, bearing a different number of electron-donating alkoxy substituents, has been prepared using a novel copper-promoted anaerobic protocol for the cyclisation of highly electron rich peri-xanthenoxanthene molecular modules. The effect of the number and position of the alkoxy substituents on the optoelectronic properties has thus been investigated, unveiling p-type semiconducting properties. All molecules displayed a significant colour change upon oxidation, suggesting that these compounds can be used to devise chromogenic materials to engineer electrochromic devices.

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Engineering Te-Containing Recognition Modules for ChalcogenBonding: Towards Supramolecular Polymeric Materials

D. Romito, D. Bonifazi. Helv. Chim. Acta 2023, 106, e202200159. DOI: 10.1002/hlca.202200159 Abstract: Aiming at the preparation of one-dimensional (1D) chalcogen-bonded supramolecular polymers at the solid state, this work describes the different syntheses which have been challenged to obtain ditopic molecular modules. At first, tellurazolopyridyl (TZP) rings have been chosen as recognition units, given their well-proven ability and persistency to self-assemble through double Te⋅⋅⋅N chalcogen bonds (ChBs). The second synthetic strategy dealt with the preparation of pyridyl-modified ebselen Te-containing analogues. By attempting several synthetic protocols, the targeted ebselen derivatives could not be obtained, whereas an unexpected Te-containing lactone as well as a spiro-type Te(IV)-containing derivatives were isolated, with the latter investigated by X-ray diffraction (XRD) analysis.

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Boron Nitride-Doped Polyphenylenic Organogels

J. Dosso, H. Oubaha, F. Fasano, S. Melinte, J.-F. Gohy, C.E. Hughes, K.D.M. Harris, N. Demitri, M. Abrami, M. Grassi, D. Bonifazi. Chem. Mater. 2022, 34, 23, 10670–10680. DOI: https://doi-org.uaccess.univie.ac.at/10.1021/acs.chemmater.2c01766 Abstract: Herein, we describe the synthesis of the first boron nitride-doped polyphenylenic material obtained through a [4 + 2] cycloaddition reaction between a triethynyl borazine unit and a biscyclopentadienone derivative, which undergoes organogel formation in chlorinated solvents (the critical jellification concentration is 4% w/w in CHCl3). The polymer has been characterized extensively by Fourier-transform infrared spectroscopy, solid-state 13C NMR, solid-state 11B NMR, and by comparison with the isolated monomeric unit. Furthermore, the polymer gels formed in chlorinated solvents have been thoroughly characterized and studied, showing rheological properties comparable to those of polyacrylamide gels with a low crosslinker percentage. Given the thermal and chemical stability, the material was studied as a potential support for solid-state electrolytes. showing properties comparable to those of polyethylene glycol-based electrolytes, thus presenting great potential for the application of this new class of material in lithium-ion batteries.

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IGDQ motogenic peptide gradient induces directional cell migration through integrin (αv)β3 activation in MDA-MB-231 metastatic breast cancer cells

S. Ayama-Canden, R. Tondo, L. Piñeros, N. Ninane, C. Demazy, M. Dieu, A. Fattaccioli, T. Tabarrant, S. Lucas, D. Bonifazi, C. Michiels. Neoplasia 2022, Vol. 31, No. C., 100816. DOI: https://doi.org/10.1016/j.neo.2022.100816 Abstract In the context of breast cancer metastasis study, we have shown in an in vitro model of cell migration that IGDQ-exposing (IsoLeu-Gly-Asp-Glutamine type I Fibronectin motif) monolayers (SAMs) on gold sustain the adhesion of breast cancer MDA-MB-231 cells by triggering Focal Adhesion Kinase and integrin activation. Such tunable scaffolds are used to mimic the tumor extracellular environment, inducing and controlling cell migration. The observed migratory behavior induced by the IGDQ-bearing peptide gradient along the surface allows to separate cell subpopulations with a “stationary” or “migratory” phenotype. In this work, we knocked down the integrins α5(β1) and (αv)β since they are already known to be implicated in cell migration. To this aim, a whole proteomic analysis was performed in beta 3 integrin (ITGB3) or alpha 5 integrin (ITGA5) knock-down MDA-MB-231 cells, in order to highlight the pathways implied in the integrin-dependent cell migration. Our results showed that i) ITGB3 depletion influenced ITGA5 mRNA expression, ii) ITGB3 and ITGA5 were both necessary for IGDQ-mediated directional single cell migration and iii) integrin (αv)β3 was activated by IGDQ fibronectin type I motif. Finally, the proteomic analysis suggested that co-regulation of recycling transport of ITGB3 by ITGA5 is potentially necessary for directional IGDQ-mediated cell migration.

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Expanding the Library of 2-Phenylbenzotellurazoles: Red-ShiftingEffect of Ethoxy Functionalities on the UV/Vis Absorption Properties

D. Romito, L. Amendolare, K. K. Kalathila, D. Bonifazi. Synthesis 2023, 55, 359–367. DOI: 10.1055/s-0041-1737898 Abstract: This work describes the high-yield synthesis of a novel series of benzotellurazoles bearing a phenyl ring in 2-position, which is differently functionalized with ethoxy chains. Changing the number and the position of these functional groups determines differences in the self-assembly in the solid state, as well as in the photophysical properties of the targeted molecules. As anticipated by theoretical calculations of the HOMO-LUMO gap of each molecule, the presence of ethoxy chains in o– and p-positions determines up to 20 nm red-shifts in the absorption peaks, when compared to unsubstituted benzotellurazole. Similarly, more significant changes are observed in the chemical shifts of 125Te NMR spectra for those derivatives bearing o– and p-ethoxy functionalization.

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On-Surface Synthesis of Rigid Benzenoid- and Nonbenzenoid-Coupled Porphyrin–Graphene Nanoribbon Hybrids

J. Deyerling, M. Pörtner, L. Đorđević, A. Riss, D. Bonifazi, W. Auwärter. J. Phys. Chem. C 2022, 126, 19, 8467–8476. DOI: https://doi-org.uaccess.univie.ac.at/10.1021/acs.jpcc.2c00912 Abstract On-surface synthesis made the fabrication of extended, atomically precise π-conjugated nanostructures on solid supports possible, with graphene nanoribbons (GNRs) and porphyrin-derived oligomers standing out. To date, examples combining these two prominent material classes are scarce, even though the chemically versatile porphyrins and the atomistic details of the nanographene spacers promise an easy tunability of structural and functional properties of the resulting hybrid structures. Here, we report the on-surface synthesis of extended benzenoid- and nonbenzenoid-coupled porphyrin–graphene nanoribbon hybrids by sequential Ullmann-type and cyclodehydrogenation reactions of a tailored Zn(II) 5,15-bis(5-bromo-1-naphthyl)porphyrin (Por(BrNaph)2) precursor on Au(111) and Ag(111). Using bond-resolved noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM), we characterize the structures of reaction intermediates and products in detail and provide insight into the effects of the annealing protocol. We further demonstrate the stability and rigidity of the extended one-dimensional porphyrin–GNR oligomers by employing an STM-based manipulation procedure, which allows for spectroscopic measurement upon lifting.

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peri-Xanthenoxanthene (PXX): a Versatile Organic Photocatalyst in Organic Synthesis

C. Pezzetta, A. Folli, O. Matuszewska, D. Murphy, R. W. M. Davidson, D. Bonifazi. Adv. Synth. Catal. 2021, 363, 1-15. DOI: 10.1002/adsc.202100030 Abstract Recent years have witnessed a continuous development of photocatalysts to satisfy the growing demand of photophysical and redox properties in photoredox catalysis, with complex structures or alternative strategies devised to access highly reducing or oxidising systems. We report herein the use of peri-xanthenoxanthene (PXX), a simple and inexpensive dye, as an efficient photocatalyst. Its highly reducing excited state allows activation of a wide range of substrates, thus triggering useful radical reactions. Benchmark transformations such as the addition of organic radicals, generated by photoreduction of organic halides, to radical traps are initially demonstrated. More complex dual catalytic manifolds are also shown to be accessible: the β-arylation of cyclic ketones is successful when using a secondary amine as organocatalyst, while cross-coupling reactions of aryl halides with amines and thiols are obtained when using a Ni co-catalyst. Application to the efficient two-step synthesis of the expensive fluoro-tetrahydro-1H-pyrido[4,3-b]indole, a crucial synthetic intermediate for the investigational drug setipiprant, has been also demonstrated.

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Substituent-Controlled Tailoring of Chalcogen-Bonded Supramolecular Nanoribbons in the Solid State

N. Biot, D. Romito, D. Bonifazi. Cryst. Growth Des. 2021, 21, 1, 536–543. DOI: 10.1021/acs.cgd.0c01318 Abstract In this work, we design and synthesize supramolecular 2,5-substituted chalcogenazolo[5,4-β]pyridine (CGP) synthons arranging in supramolecular ribbons at the solid state. A careful choice of the combination of substituents at the 2- and 5-positions on the CGP scaffold is outlined to accomplish supramolecular materials by means of multiple hybrid interactions, comprising both chalcogen and hydrogen bonds. Depending on the steric and electronic properties of the substituents, different solid-state arrangements have been achieved. Among the different moieties on the 5-position, an oxazole unit has been incorporated on the Se- and Te-congeners by Pd-catalyzed cross-coupling reaction and a supramolecular ribbon-like organization was consistently obtained at the solid state.

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BN-Doped Metal–Organic Frameworks: Tailoring 2D and 3D Porous Architectures through Molecular Editing of Borazines

F. Fasano, J. Dosso, G. Bezzu, M. Carta, F. Kerff, N. Demitri, B. -L. Su, D. Bonifazi. Chem. Eur. J. 2021 , 27, 4124 –4133. DOI: 10.1002/chem.202004640 Abstract Building on the MOF approach to prepare porous materials, herein we report the engineering of porous BN-doped materials using tricarboxylic hexaarylborazine ligands, which are laterally decorated with functional groups at the full-carbon ‘inner shell’. Whilst an open porous 3D entangled structure could be obtained from the double interpenetration of two identical metal frameworks derived from the methyl substituted borazine, the chlorine-functionalised linker undergoes formation of a porous layered 2D honeycomb structure, as shown by single-crystal X-ray diffraction analysis. In this architecture, the borazine cores are rotated by 60° in alternating layers, thus generating large rhombohedral channels running perpendicular to the planes of the networks. An analogous unsubstituted full-carbon metal framework was synthesised for comparison. The resulting MOF revealed a crystalline 3D entangled porous structure, composed by three mutually interpenetrating networks, hence denser than those obtained from the borazine linkers. Their microporosity and CO2 uptake were investigated, with the porous 3D BN-MOF entangled structure exhibiting a large apparent BET specific surface area (1091 m2 g−1) and significant CO2 reversible adsorption (3.31 mmol g−1) at 1 bar and 273 K.

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