Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

The selectivity of our previously described gold-catalyzed tandem reaction, 1,2-indole migration followed by aura-iso-Nazarov cyclization, of 3-propargylindoles bearing (hetero)aromatic substituents at both the propargylic and terminal positions, was reversed by the proper choice of the catalyst and the reaction conditions. Thus, 3-(inden-2-yl)indoles, derived from an aura-Nazarov cyclization (instead of an aura-iso-Nazarov cyclization), were obtained in moderate to good yields from a variety of 3-propargylindolesMICINN (CTQ2010-15358 and CTQ2009-09949), Junta de Castilla y Leon (BU021A09 and GR-172), MEC (FPU predoctoral fellowship to D.M.), Ramón y Cajal (contract to M.A F R.), Juan de la Cierva (contract to P.G.G.

Enantiopure Double ortho-Oligophenylethynylene-Based Helical Structures with Circularly Polarized Luminescence Activity

We thank the Ministerio de Economia y Competitividad (CTQ2017-85454-C2-1-P and CTQ2017-85454-C2-2-P), Ministerio de Ciencia e Innovacion (PID2020-113059GB-C21 and PID2020-113059GB-C22) and Junta de Andalucia (P20.00162) (Spain) for funding and P.R. and A. O. G. also for FPU contracts. Funding for open access charge is acknowledged to Universidad de Granada / CBUA.We also thank Big&Open Data Innovation Laboratory (BODaI-Lab), University of Brescia, granted by Fondazione Cariplo and Regione Lombardia, for access to resources of Computing Center CINECA (Bologna), Italy. Support from the Italian MIUR (Grant No. 2017A4XRCA) is also acknowledged.In this paper, we describe the optical and chiroptical properties of an enantiopure multipodal ortho-oligophenylethynylene (S,S,S,S)-1 presenting four chiral sulfoxide groups at the extremes. The presence of these groups together with alkynes allows the coordination with carbophilic Ag(I), and/or oxophilic Zn(II) cations, yielding double helical structures in an enantiopure way. In this sense, different behaviors in absorption, fluorescence, ECD and CPL spectra have been found depending on the stoichiometry and nature of the metal. We have observed that Zn(II) coordination favors an intensity increase of the electronic circular dichroism (ECD) spectra of compound (S,S,S,S)-1 yielding an M-helicity in the ortho-oligophenylene ethynylene (o-OPE) backbone. On the other hand, ECD spectra of final Ag(I) complex shows two different bands with an opposite sign to the free ligand, thus giving the P-helical isomer. In addition, circularly polarized luminescence (CPL) exhibit an enhanced intensity and negative sign in both complexes. Computational studies were also carried out, supporting the experimental results.Spanish Government CTQ2017-85454-C2-1-P CTQ2017-85454-C2-2-PInstituto de Salud Carlos III Spanish Government European Commission PID2020-113059GB-C21 PID2020-113059GB-C22Junta de Andalucia European Commission P20.00162University of Brescia / CBUAFondazione CariploMinistry of Education, Universities and Research (MIUR) 2017A4XRCARegione Lombardi

Photostability and Dynamic Helical Behavior in Chiral Poly(phenylacetylene)s with a Preferred Screw-Sense

Data Availability Statement The data that support the findings of this study are available in the supplementary material of this article.Acknowledgements We thank Servicio de Microscopía Electrónica (RIAIDT, USC). Financial support from AEI (PID2019-109733GBI00), Ministerio de Ciencia e Innovación (PID2019- 107307RB-100 and PID2020-117605GB-100, PID2020- 113059GB-C21, PID2020-113059GB-C22). Xunta de Galicia (ED431C 2018/30, ED431C 2021/40, Centro Singular de Investigación de Galicia acreditación 2019–2022, ED431G 2019/03 and the European Regional Development Fund (ERDF) is gratefully acknowledged. F.R.T. thanks Xunta de Galicia for a predoctoral contract. We acknowledge CESGA for computational time and we also thank Servicio de Nanotecnología y Análisis de Superficies (CACTI-CINBIO, UVigo).Helical polymers such as poly(phenylacetylene)s (PPAs) are interesting materials due to the possibility of tuning their helical scaffold (sense and elongation) once they have been prepared and by the presence of external stimuli. The main limitation in the application of PPAs is their poor photostability. These polymers degrade under visible light exposure through a photochemical electrocyclization process. In this work, it was demonstrated, through a selected example, how the photochemical degradation in PPAs is directly related to their dynamic helical behavior. Thus, while PPAs with dynamic helical structures show poor photostability under UV/Vis light exposure, poly-(R)-1, bearing an enantiopure sulfoxide group as pendant group and designed to have a quasistatic helical behavior, shows a large photostability due to the restricted conformational composition at the polyene backbone, needed to orient the conjugated double bonds prior to the photochemical electrocyclization process and the subsequent degradation of the material.AEI (PID2019-109733GBI00)Ministerio de Ciencia e Innovación (PID2019- 107307RB-100 and PID2020-117605GB-100, PID2020- 113059GB-C21, PID2020-113059GB-C22)Xunta de Galicia (ED431C 2018/30, ED431C 2021/40, Centro Singular de Investigación de Galicia acreditación 2019–2022, ED431G 2019/03 and the European Regional Development Fund (ERDF

A Red-Emitting, Multidimensional Sensor for the Simultaneous Cellular Imaging of Biothiols and Phosphate Ions

The development of new fluorescent probes for cellular imaging is currently a very active field because of the large potential in understanding cell physiology, especially targeting anomalous behaviours due to disease. In particular, red-emitting dyes are keenly sought, as the light in this spectral region presents lower interferences and a deeper depth of penetration in tissues. In this work, we have synthesized a red-emitting, dual probe for the multiplexed intracellular detection of biothiols and phosphate ions. We have prepared a fluorogenic construct involving a silicon-substituted fluorescein for red emission. The fluorogenic reaction is selectively started by the presence of biothiols. In addition, the released fluorescent moiety undergoes an excited-state proton transfer reaction promoted by the presence of phosphate ions, which modulates its fluorescence lifetime, τ, with the total phosphate concentration. Therefore, in a multidimensional approach, the intracellular levels of biothiols and phosphate can be detected simultaneously using a single fluorophore and with spectral clearing of cell autofluorescence interferences. We have applied this concept to different cell lines, including photoreceptor cells, whose levels of biothiols are importantly altered by light irradiation and other oxidants.This work was funded by grants CTQ2014-56370-R, CTQ2014-53598, and CTQ2014-55474-C2-2-R from the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF), and grant FQM2012-790 from the Consejería de Innovación, Ciencia y Empresa (Junta de Andalucı́a), including costs to publish in open access

Enantiopure double ortho-oligophenylethynylene-based helical structures with circularly polarized luminescence activity

In this paper, we describe the optical and chiroptical properties of an enantiopure multipodal ortho-oligophenylethynylene (S,S,S,S)-1 presenting four chiral sulfoxide groups at the extremes. The presence of these groups together with alkynes allows the coordination with carbophilic Ag(I), and/or oxophilic Zn(II) cations, yielding double helical structures in an enantiopure way. In this sense, different behaviors in absorption, fluorescence, ECD and CPL spectra have been found depending on the stoichiometry and nature of the metal. We have observed that Zn(II) coordination favors an intensity increase of the electronic circular dichroism (ECD) spectra of compound (S,S,S,S)-1 yielding an M-helicity in the ortho-oligophenylene ethynylene (o-OPE) backbone. On the other hand, ECD spectra of final Ag(I) complex shows two different bands with an opposite sign to the free ligand, thus giving the P-helical isomer. In addition, circularly polarized luminescence (CPL) exhibit an enhanced intensity and negative sign in both complexes. Computational studies were also carried out, supporting the experimental result

Two-dimensional carbon-based conductive materials with dynamically controlled asymmetric Dirac cones

The design of two dimensional graphene-type materials with an anisotropic electron flow direction in the X- and Y-axes opens the door for the development of novel electronic materials with multiple functions in nanoelectronics. In the present work, we have studied the electronic transport properties of a new family of 2D graphene-graphyne hybrids presenting conformationally free phenylethylene subunits. This system ensures two different conductive pathways that are perpendicular to each other: an acene nanoribbon subunit, in the X-axis, with graphene-type conduction, and a free to rotate phenylethylene subunit, in the Y-axis, in which the magnitude of the conduction depends dynamically on the corresponding torsion angle. Our calculations have confirmed that this system presents two different conduction pathways, which are related to the presence of asymmetric Dirac-type cones. Moreover, the Dirac cones can be dynamically modified in the presence of an external gate electrode, which is unprecedented in the literatureWe thank the MICINN (project CTQ-2011.22455) and the Regional Government of Andalucía (project P09-FQM-04571) for financial support and the ‘Centro de Supercomputación de la Universidad de Granada (UGRGRID-CSIRC)’ for computation time. NF and DM thank MICINN for their research contract

Exploring Potentialities and Limitations of Stapled o- Oligo(PhenyleneEthynylene)s (o-OPEs) as Efficient Circularly Polarized Luminescence Emitters

In this paper we have studied the chiroptical properties of a family of o-OPE derivatives with different steric hindrance. Experimental results show high dissymmetry factors (gabs and glum up to 1.1x10-2) and very similar ECD and CPL for all the derivatives, that makes this basic o-OPE scaffold a robust pure organic emitter. VCD spectra are used to characterize conformational properties in solution. DFT and TD-DFT calculations support experimental results also proving that ECD and CPL are almost exclusively linked to helical moiety and not to size or conformation of substituents. As chiroptical properties of these emitters are independent of substituents, this OPE scaffold can be used as basic skeleton for the design of sensing probes with high CPL efficiencies.We thank MICINN (CTQ2014-53598-R) and Junta de Andalucía (FQM1484) for financial support. Computing Center CINECA Via Magnanelli 6/3 40033 – Casalecchio di Reno (Bologna) Italy and Regione Lombardia for the LISA Grant No. “ChiPhyto: HPL13POZE1” is acknowledged for access to computational facilities. P. Reiné thanks MICINN for a FPU fellowship

Efficient acetate sensor in biological media based on a selective Excited State Proton Transfer (ESPT) reaction

We have synthesized a new fluoride−containing xanthenic dye able to dynamically and quantitatively detect acetate anion, a biologically relevant analyte, in water. We studied deeply the photophysical properties of the compound and verified its use as an acetate probe in synthetic serum.MINECO-FEDER CTQ2014-53598Junta Andalucía FQM2012-79

2D self-assembly of o-OPE foldamers for chiroptical barcoding

We report on the preparation and characterization of two dimensional (2D) films of (S,S,P)-1 and (R,R,M)-1ortho-oligophenylene ethylene (o-OPE) enantiomers presenting high values of circularly polarized luminescence (CPL). The amphiphilic character of these two molecules allows a precise 2D self-assembly at the air/water interface and an efficient transfer onto a glass solid support. The morphological and chiroptical characterization of the solid supports after the transfer of 1, 8, 16 and 32 Langmuir films of (S,S,P)-1 and (R,R,M)-1 has been carried out. The strong chiroptical values of these monomers allow reliable ECD measurements to be obtained after a single transfer, with ECD values increasing as the number of transferred films increases. The semi-liquid behavior of the monomers on the solid substrate allows CPL measurements free of photoselection artifacts that show values similar to those obtained in solution and independent of monomer concentration. All these properties have allowed us to develop the first simple organic molecule (SOM)-based chiroptical barcoding presenting positive and negative regions as a proof of concept

Novel ortho-OPE metallofoldamers: binding-induced folding promoted by nucleating Ag(i)-alkyne interactions

We have developed a new family of ortho-oligophenylene ethynylene (o-OPE) metallofoldamers. The folding of these helicates is induced by nucleating carbon-metal interactions between Ag(i) cations and the alkynes of the inner core of the o-OPEs. These o-OPEs form metal-organic assemblies where at least three alkyne moieties are held in close proximity to form novel Ag(i)-complexes with the metal ion lodged into the helical cavity. NMR titration experiments and photokinetic studies have provided quantitative data about the thermodynamic and kinetic features of such binding/folding phenomena. X-ray diffraction and DFT studies have been performed to extract structural information on how the Ag(i) cation is accommodated into the cavity. The great simplicity and versatility of these new metallofoldamers open up the possibility to develop novel structures with applications in material science and/or in asymmetric catalysisThis research was funded by the Regional Government of Andalucía (project P09-FQM-4571) and the ICIQ Foundation. DM thanks Regional Government of Andalucía for her contract. AML thanks MICINN for her FPU fellowship. The authors thank the Centro de Servicios de Informática y Redes de Comunicaciones (CSIRC), Universidad de Granada, for providing the computing tim