Photoremovable Protecting Groups: Across the Light Spectrum to Near-Infrared Absorbing Photocages

We discuss the past decade of progress in the field of photoremovable protecting groups that allowed the development of photocages activatable by near-IR light and highlight the individual conceptual advancements that lead to general guidelines to design new such photoremovable protecting groups. We emphasize the importance of understanding the individual photochemical reaction mechanisms that was necessary to achieve this progress and provide an outlook of the subsequent steps to facilitate a swift translation of this research into clinical praxis. Since this issue of CHIMIA is dedicated to the late Prof. Thomas Bally, we decided to provide a personal perspective on the field to which he contributed himself. We tried to write this review with the general readership of CHIMIA in mind in a hope to pay a tribute to the extraordinary dedication and clarity with which Thomas Bally used to explain abstract chemical concepts to his students or colleagues. We are uncertain whether we matched such challenge but we believe that he would have liked such approach very much

Cyanine Renaissance: Tailoring the Properties to Applications

In this account, we provide an overview of the applications that arose from the recently developed synthetic methodology that delivers heptamethine cyanines (Cy7) substituted at the central chain. The ability to easily introduce and manipulate various substituents in different substitution patterns along the cyanine chain enabled rational tailoring of the photophysical and photochemical properties. Exercising this control over the structure–property relationship proved to have a substantial impact in the field of cyanine dyes and was swiftly harnessed in a number of emerging applications in distinct areas, including fluorescent probes, biosensors, dye-sensitized upconversion nanoparticles, phototruncation of cyanines and photocages. While this method unlocked a number of new avenues, many synthetic challenges remain to be conquered in order to fully capitalize on the potential of cyanines, and we provide a short perspective that summarizes them at the end of this manuscript

Cyanine-Flavonol Hybrids for Near-Infrared Light-Activated Delivery of Carbon Monoxide

Carbon monoxide (CO) is an endogenous signaling molecule that controls a number of physiological processes. To circumvent the inherent toxicity of CO, light-activated CO-releasing molecules (photoCORMs) have emerged as an alternative for its administration. However, their wider application requires photoactivation using biologically benign visible and near-infrared (NIR) light. In this work, a strategy to access such photoCORMs by fusing two CO-releasing flavonol moieties with a NIR-absorbing cyanine dye is presented. These hybrids liberate two molecules of CO in high chemical yields upon activation with NIR light up to 820 nm and exhibit excellent uncaging cross-sections, which surpass the state-of-the-art by two orders of magnitude. Furthermore, the biocompatibility and applicability of the system in vitro and in vivo are demonstrated, and a mechanism of CO release is proposed. It is hoped that this strategy will stimulate the discovery of new classes of photoCORMs and accelerate the translation of CO-based phototherapy into practice

Coordination mechanism of cyanine dyes on the surface of core@active shell β-NaGdF4:Yb3+,Er3+ nanocrystals and its role in enhancing upconversion luminescence

The sensitization of lanthanide-doped upconversion nanocrystals (UCNCs) using organic dyes with a broad and intense optical absorption is an interesting approach for efficient excitation-energy harvesting and enhancing the upconversion luminescence of such UCNCs. In this work, an ultrasmall (similar to 6.5 nm in diameter) beta-NaGdF4:Yb3+,Er3+ core and related core@shell UCNCs were sensitized using six NIR-excitable cyanine dyes with a wide range of functional groups and optical properties. The greatest UC enhancement of 680-times was observed for the conjugate between the Cy 754 dye and NaGdF4:Yb3+,Er3+@NaGdF4:10%Yb3+,30%Nd3+ core@shell UCNCs excited using a 754 nm laser. The enhancement was estimated relative to NaGdF4:Yb3+,Er3+@NaGdF4:10%Yb3+,30%Nd3+ core@shell UCNCs capped with oleic acid and excited using a similar intensity (75 W cm(-2)) of a 980 nm laser. UC intensity measurements for identical dye-sensitized UCNCs carried out in methanol and in deuterated methanol under argon, as well as in air, allowed us to reveal the connection of the dye triplet states with UCNC sensitization as well as of the hydroxyl groups with quenching of the excited states of lanthanide ions. For UCNCs dispersed in methanol, the strong quenching UC luminescence was always observed, including core@shell UCNCs (with a shell of similar to 2 nm). A strong influence of the triplet states of the dyes was observed for the two dyes Cy 754 and Cy 792 that bind firmly to UCNCs and allow the distances between the dye and the UCNC to be reduced, whereas the contribution of this sensitization pathway is very insignificant for Cy 740 and Cy 784 dyes that bind weakly to UCNCs

Coordination mechanism of cyanine dyes on the surface of core@active shell β-NaGdF4_{4}:Yb3+^{3+},Er3+^{3+} nanocrystals and its role in enhancing upconversion luminescence

The sensitization of lanthanide-doped upconversion nanocrystals (UCNCs) using organic dyes with a broad and intense optical absorption is an interesting approach for efficient excitation-energy harvesting and enhancing the upconversion luminescence of such UCNCs. In this work, an ultrasmall (∼6.5 nm in diameter) β-NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$ core and related core@shell UCNCs were sensitized using six NIR-excitable cyanine dyes with a wide range of functional groups and optical properties. The greatest UC enhancement of 680-times was observed for the conjugate between the Cy 754 dye and β-NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$@NaGdF$_{4}$:10%Yb$^{3+},30$^{3+} core@shell UCNCs excited using a 754 nm laser. The enhancement was estimated relative to NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$@NaGdF$_{4}$:10%Yb$^{3+},30$^{3+} core@shell UCNCs capped with oleic acid and excited using a similar intensity (75 W cm$^{-2}$) of a 980 nm laser. UC intensity measurements for identical dye-sensitized UCNCs carried out in methanol and in deuterated methanol under argon, as well as in air, allowed us to reveal the connection of the dye triplet states with UCNC sensitization as well as of the hydroxyl groups with quenching of the excited states of lanthanide ions. For UCNCs dispersed in methanol, the strong quenching UC luminescence was always observed, including core@shell UCNCs (with a shell of ∼2 nm). A strong influence of the triplet states of the dyes was observed for the two dyes Cy 754 and Cy 792 that bind firmly to UCNCs and allow the distances between the dye and the UCNC to be reduced, whereas the contribution of this sensitization pathway is very insignificant for Cy 740 and Cy 784 dyes that bind weakly to UCNCs

Pedagogía social : revista interuniversitaria

Monográfico con el título: "Redes territoriales de acción socioeducativa: una apuesta por la innovación social colaborativa"Título, resumen y palabras clave también en portuguésResumen basado en el de la publicaciónEstudio cualitativo, localizado en Estados Unidos, presenta un análisis en profundidad sobre el liderazgo en escuelas y organizaciones comunitarias que ayudan a conectar a los alumnos y a las familias con recursos educativos fundamentales. Los datos han sido recopilados a partir de 132 entrevistas con personas que han experimentado las complejidades sociales de la indigencia. Los resultados sugieren que el liderazgo participativo fomenta el aprendizaje, el simbolismo, el desarrollo de la identidad y la responsabilidad. El tipo de liderazgo promete brindar oportunidades para los desfavorecidos, que no tienen acceso a recursos o relaciones de importancia.ES

Phosphoramidite-based photoresponsive ligands displaying multifold transfer of chirality in dynamic enantioselective metal catalysis

The transfer and amplification of chirality in biological and artificial systems is a fundamental process that allows for a dynamic control of structure and function. Only a few responsive systems harness the dynamic transfer of chirality and can act as photoswitchable chiral inductors. Here we demonstrate that photoresponsive phosphoramidite ligands based on a chiral biaryl-substituted molecular switch can be used to alter the activity and invert the stereoselectivity of a copper-catalysed asymmetric conjugate addition. The phosphoramidites were obtained as pairs of diastereoisomers, each displaying a distinct catalytic activity and stereoselectivity as a result of the light-controlled matched–mismatched interaction between the fixed chirality at the phosphorus atom and the dynamic chirality of the switch. The result is an elegant balance of two competing catalysts, of which the complementary catalytic performance is tunable via light, which takes advantage of the internal dynamic transfer of chirality on reversible alkene photoisomerization. This discovery paves the way for the future development of more complex chirality-dependent photoresponsive and multitasking catalysts. [Figure not available: see fulltext.]

End-capping of amphiphilic nanotubes with phospholipid vesicles:impact of the phospholipid on the cap formation and vesicle loading under osmotic conditions

Soft amphiphilic nanotubes are capped with vesicles comprised of either overall neutral, zwitterionic phospholipids, or those that carry a net charge. The phase transition temperature of the zwitterionic phospholipids plays a crucial role in the phase separation that leads to the end-capped nanotubes. The cationic vesicle caps can be loaded into the nanotubes via osmosis whereas the anionic vesicle caps are stable under hyper-osmotic conditions. Furthermore, no additional salt needs to be added for the cationic vesicle caps to induce the loading of the vesicles into the nanotubes due to the presence of counterions

Driving a Third Generation Molecular Motor with Electrons Across a Surface

Excitation of single molecules with electrons tunneling between a sharp metallic tip of a scanning tunneling microscope and a metal surface is one way to study and control dynamics of molecules on surfaces. Electron tunneling induced dynamics may lead to hopping, rotation, molecular switching, or chemical reactions. Molecular motors that convert rotation of subgroups into lateral movement on a surface can in principle also be driven by tunneling electrons. For such surface-bound motor molecules the efficiency of motor action with respect to electron dose is still not known. Here, the response of a molecular motor containing two rotor units in the form of overcrowded alkene groups to inelastic electron tunneling has been examined on a Cu(111) surface in ultrahigh vacuum at 5 K. Upon vibrational excitation, switching between different molecular conformations is observed, including conversion of enantiomeric states of chiral conformations. Tunneling at energies in the range of electronic excitations causes activation of motor action and movement across the surface. The expected unidirectional rotation of the two rotor units causes forward movements but with a low degree of translational directionality