Publication – Bonifazi Group

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.

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.

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.

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.

peri-Acenoacene Ribbons with Zigzag BN-Doped Peripheries

Franceschini, M., Crosta, M., Ferreira, R. R., Poletto, D., Demitri, N., Zobel, J. P., González, L., and Bonifazi, D. J. Am. Chem. Soc. 2022, 144, 47, 21470-21484 doi: 10.1021/jacs.2c06803 Abstract: Here, we report the synthesis of BN-doped graphenoid nanoribbons, in which peripheral carbon atoms at the zigzag edges have been selectively replaced by boron and nitrogen atoms as BN and NBN motifs. This includes high-yielding ring closure key steps that, through N-directed borylation reaction using solely BBr3, allow the planarization of meta-oligoarylenyl precursors, through the formation of B–N and B–C bonds, to give ter-, quater-, quinque-, and sexi-arylenyl nanoribbons. X-ray single-crystal diffraction studies confirmed the formation of the BN and NBN motifs and the zigzag-edged topology of the regularly doped ribbons. Steady-state absorption and emission investigations at room temperature showed a systematic bathochromic shift of the UV–vis absorption and emission envelopes upon elongation of the oligoarylenyl backbone, with the nanoribbon emission featuring a TADF component. All derivatives displayed phosphorescence at 77 K. Electrochemical studies showed that the π-extension of the peri-acenoacene framework provokes a lowering of the first oxidative event (from 0.83 to 0.40 V), making these nanoribbons optimal candidates to engineer p-type organic semiconductors.

Tweaking the Optoelectronic Properties of S-Doped Polycyclic Aromatic Hydrocarbons by Chemical Oxidation

Matuszewska, O., Battisti, T., Ferreira, R.R., Biot, N., Demitri, N., Mézière, C., Allain, M., Sallé, M., Mañas-Valero, S., Coronado, E., Fresta, E., Costa, R..D. and Bonifazi, D. Chem. Eur. J. 2023, 29, e2022031. DOI: 10.1002/chem.202203115 Abstract Peri-thiaxanthenothiaxanthene, an S-doped analog of peri-xanthenoxanthene, is used as a polycyclic aromatic hydrocarbon (PAH) scaffold to tune the molecular semiconductor properties by editing the oxidation state of the S-atoms. Chemical oxidation of peri-thiaxanthenothiaxanthene with H2O2 led to the relevant sulfoxide and sulfone congeners, whereas electrooxidation gave access to sulfonium-type derivatives forming crystalline mixed valence (MV) complexes. These complexes depicted peculiar molecular and solid-state arrangements with face-to-face p-p stacking organization. Photophysical studies showed a widening of the optical bandgap upon progressive oxidation of the S-atoms, with the bis-sulfone derivative displaying the largest value (E00 = 2.99 eV). While peri-thiaxanthenothiaxanthene showed reversible oxidation properties, the sulfoxide and sulfone derivatives mainly showed reductive events, corroborating their n-type properties. Electric measurements of single crystals of the MV complexes exhibited a semiconducting behavior with a remarkably high conductivity at room temperature (10-1-10-2 S cm-1 and 10-2-10-3 S cm-1 for the O and S derivatives, respectively), one of the highest reported so far. Finally, the electroluminescence properties of the complexes were tested in light-emitting electrochemical cells (LECs), obtaining the first mid-emitting PAH-based LECs.

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.

Customising excitation properties of polycyclic aromatic hydrocarbons by rational positional heteroatom doping: the peri-xanthenoxanthene (PXX) case

C. Valentini, D. Gowland, C. G. Bezzu, D. Romito, N. Demitri, N. Bonini, D. Bonifazi. Chem. Sci. 2022, 13, 6335-6347. DOI: 10.1039/d2sc01038k Abstract In this paper we tackle the challenge of gaining control of the photophysical properties of PAHs through a site-specific N-doping within the structural aromatic framework. By developing a simple predictive tool that identifies C(sp2)-positions that if substituted with a heteroatom would tailor the changes in the absorption and emission spectral envelopes, we predict optimal substitutional patterns for the model peri-xanthenoxanthene (PXX) PAH. Specifically, TDDFT calculations of the electron density difference between the S1 excited state and S0 ground state of PXX allowed us to identify the subtleties in the role of sites i.e., electron donating or withdrawing character on excitation. The replacement of two C(sp2)-atoms with two N-atoms, in either electron donating or withdrawing positions, shifts the electronic transitions either to low or high energy, respectively. This consequently shifts the PXX absorption spectral envelop bathochromically or hypsochromically, as demonstrated by steady-state absorption spectroscopic measurements. Within the series of synthesised N-doped PXX, we tune the optical band gap within an interval of ∼0.4 eV, in full agreement with the theoretical predictions. Relatedly, measurements show the more blueshifted the absorption/emission energies, the greater the fluorescence quantum yield value (from ∼45% to ∼75%). On the other hand, electrochemical investigations suggested that the N-pattern has a limited influence on the redox properties. Lastly, depending on the N-pattern, different supramolecular organisations could be obtained at the solid-state, with the 1,7-pattern PXX molecule forming multi-layered, graphene-like, supramolecular sheets through a combination of weak H-bonding and π–π stacking interactions. Supramolecular striped patterned sheets could also be formed with the 3,9- and 4,10-congeners when co-crystallized with a halogen-bond donor molecule.

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.

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.