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

Sulfoxide-Induced Homochiral Folding of ortho-Phenylene Ethynylenes (o-OPEs) by Silver(I) Templating: Structure and Chiroptical Properties

A new family of homochiral silver complexes based on carbophilic interactions with ortho-phenylene ethynylene (o-OPE) scaffolds containing up to two silver atoms are described. These compounds represent a unique class of complexes with chirality at the metal. Chiral induction is based on the inclusion of chiral sulfoxides, which allow efficient transfer of chirality to the helically folded o-OPE, leading to circularly polarized luminescence (CPL)- and vibrational circular dichroism (VCD)-active compounds. In the presence of silver(I) cations, carbophilic interactions dominate, which promote helical structures with a defined helicity. This is one of the very scarce examples of the use of such interactions in the attractive field of abiotic foldamers. The switching event has been extensively studied by using different chiroptical techniques, including circular dichroism, CPL, and VCD, and represents one of the few CPL switches described in the literature.We thank MINECO (FEDER-funded grant CTQ2014-53598-R). Computing Center CINECA, Bologna, Italy; Regione Lombardia for LISA grant no. “ChiPhyto: HPL13POZE1”, and the “Centro de Supercomputación de la UGR” (UGRGRID) are acknowledged for access to computational facilities. S.R. thanks the MECD for an FPU fellowship

Síntesis y propiedades de nuevos azocompuestos como interruptores moleculares quirales y nuevos inhibidores de la fluorescencia

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Orgánica. Fecha de lectura: 13-12-2019Esta tesis tiene embargado el acceso al texto completo hasta el 13-06-2021El trabajo ha sido financiado por el Ministerio de Economía y Competitividad y del Ministerio de Ciencia e Innovación (Proyectos: CTQ2014-53894-R y CTQ2017-85454-C2-2-P)

Selectivity in the chiral self-assembly of nucleobase-arylazopyrazole photoswitches along DNA templates

The control of supramolecular DNA assembly through external stimuli such as light represents a promising approach to control bioreactions, and modulate hybridization or delivery processes. Here, we report on the design of nucleobase-containing arylazopyrazole photoswitches that undergo chiral organization upon self-assembly along short DNA templates. Chiroptical spectroscopy shows that the specific nucleobases allow selectivity in the resulting supramolecular DNA complexes, and UV light irradiation triggers partial desorption of the arylazopyrazole photoswitches. Molecular modeling studies reveal the differences of binding modes between the two configurations in the templated assembly. Remarkably, our results show that the photoswitching behaviour controls the self-assembly process along DNA, opening the way to potential applications as nano- and biomaterialsPID2020-119306GB-100, European Union (CLASSY project, Horizon 2020 No. 862081

Turn-on Fluorescent Biosensors for Imaging Hypoxia-like Conditions in Living Cells

We present the synthesis, photophysical properties, and biological application of nontoxic 3-azo-conjugated BODIPY dyes as masked fluorescent biosensors of hypoxia-like conditions. The synthetic methodology is based on an operationally simple N=N bond-forming protocol, followed by a Suzuki coupling, that allows for a direct access to simple and underexplored 3-azo-substituted BODIPY. These dyes can turn on their emission properties under both chemical and biological reductive conditions, including bacterial and human azoreductases, which trigger the azo bond cleavage, leading to fluorescent 3-amino-BODIPY. We have also developed a practical enzymatic protocol, using an immobilized bacterial azoreductase that allows for the evaluation of these azo-based probes and can be used as a model for the less accessible and expensive human reductase NQO1. Quantum mechanical calculations uncover the restructuration of the topography of the S1 potential energy surface following the reduction of the azo moiety and rationalize the fluorescent quenching event through the mapping of an unprecedented pathway. Fluorescent microscopy experiments show that these azos can be used to visualize hypoxia-like conditions within living cellsThis article is dedicated to Professor M. Carmen Carreño on the occasion of her retirement. We thank MINECO (grant CTQ2017-85454-C2-2-P), MICINN (grant PID2020- 113059GB-C22), MCIU (grant PGC2018-094644-B-C21), the Ramón y Cajal Program (grant RYC-2016-20489), the Fundación La Caixa (grant no. LCF/BQ/DR19/11740024), and the Comunidad Autónoma de Madrid (B2017/BMD-3867 RENIMCM) and co-financed by the European Structural and investment fund for financial support. I.C. and F.R.-G. also acknowledge the Red Española de Supercomputación, the MareNostrum Supercomputer Center, and the Centro de Computación Científica of the UAM (CCC-UAM) for the generous allocation of computer time and for their technical support. We thank the “Servicio de Microscopía óptica y confocal CBMSO” facility for their assistance. We also thank Prof. M. C. Carreño for her advice and helpful discussions during the wor

OFF/ON switching of circularly polarized luminescence by oxophilic interaction of homochiral sulfoxide-containing o-OPEs with metal cations

Here we describe a new class of CPL switches based on oxophilic interactions between chiral sulfoxide-containing ortho-phenylene ethynylene (o-OPE) foldamers and cationic metals. These systems represent a unique case combining high glum values (up to 0.7 × 10−2) and high quantum yields in both folded ON and unfolded OFF CPL states