Two-Photon Absorption Enhancement by the Inclusion of a Tropone Ring in Distorted Nanographene Ribbons.

A new family of distorted ribbon-shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two-photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven-membered-ring-containing nanographene presenting a tropone moiety at the edge, its full-carbon analogue, and a purely hexagonal one. We have found that the TPA cross-sections and the electrochemical band gaps of the seven-membered-ring-containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non-linear optical properties of those ribbons.

Chiroptical Symmetry Analysis: Exciton Chirality-Based Formulae to Understand the Chiroptical Responses of Cn and Dn Symmetric Systems.

The high sensitivity of chiroptical responses to conformational changes and supramolecular interactions has prompted an increasing interest in the development of chiroptical applications. However, prediction of and understanding the chiroptical responses of the necessary large systems may not be affordable for calculations at high levels of theory. In order to facilitate the development of chiroptical applications, methodologies capable of evaluating the chiroptical responses of large systems are necessary. The exciton chirality method has been extensively used for the interaction between two independent chromophores through the Davydov model. For systems presenting C2 or D2 symmetry, one can get the same results by applying the selection rules. In the present article, the analysis of the selection rules for systems with symmetries Cn and Dn with n = 3 and 4 is used to uncover the origin of their chiroptical responses. We foresee that the use of the Chiroptical Symmetry Analysis (CSA) for systems presenting the symmetries explored herein, as well as for systems presenting higher symmetries will serve as a useful tool for the development of chiroptical applications.

A Triskelion-Shaped Saddle-Helix Hybrid Nanographene.

A unique rippled nanographene consisting of 52 fused rings is presented in which six out-of-plane motifs are fully fused into a triangular aromatic surface with a size of approximately 2.5 nm. Three units of an unprecedented fully lateral π-extended octabenzo[5]helicene together with three units of saddle-shaped heptagonal rings are combined in a single structure, leading to a well-soluble warped nanographene. The two diastereomeric pairs of possible enantiomers were isolated, and their linear, non-linear, and chiroptical properties were evaluated, revealing outstanding quantum yield and brightness values at low energy, together with good chiroptical responses in both absorption and emission.

Circularly Polarized Luminescence of Boronic Acid-Derived Salicylidenehydrazone Complexes Containing Chiral Boron as Stereogenic Unit.

Racemic mixtures of boronic acid-derived salicylidenehydrazone (BASHY) complexes were enantiomerically resolved. The chiroptical properties of the stereoisomers, containing an asymmetric boron as the only stereogenic unit, are translated into mirror-imaged electronic circular dichroism spectra and circularly polarized luminescence (CPL, dissymmetry factors of 3-5 × 10-4) is observed. The spectral position of the CPL emission is determined by the push-pull character of the dye. These features expand the functional scope of the brightly emitting BASHY dye platform.

Undecabenzo[7]superhelicene: A Helical Nanographene Ribbon as a Circularly Polarized Luminescence Emitter.

The synthesis and characterization of an enantiopure superhelicene nanographene is reported in which two saddle-shaped and one planar hexabenzocoronene (HBC) units are arranged in a helicoidal shape to form an undecabenzo[7]carbohelicene. The described compound is the first fully π-extended [7]helicene. Racemic resolution of the helical nanographene permitted analysis of the chiroptical properties and revealed dissymmetry factors in the range of 2×10-3 both in the absorption and in the emission measurements. Remarkably, non-linear photophysical analysis demonstrated a two-photon absorption cross-section of 870 GM at 800 nm and a perfect overlap between linear, non-linear, and chiral emissions.

Diverse Chiral Scaffolds from Diethynylspiranes: All-Carbon Double Helices and Flexible Shape-Persistent Macrocycles.

State-of-the-art chiroptical spectroscopies are valuable tools for structural elucidation. However, the potential of these spectroscopies for everyday applications has not been exploited to date partially due to the lack of sufficiently stable and efficient chiroptical systems. To this end, the development of suitable chiroptical structures is essential. Herein, we present the synthesis of spiro-compounds (P2 )-1 and (P4 )-2 as well as (M2 )-1 and (M4 )-2 exhibiting remarkable chiroptical responses. Theoretical simulations show that (P2 )-1, constituted by two (P)-configured spiranic chiral axes, presents an all-carbon double helix structure with (M)-helicity. On the other hand, molecular dynamic simulations reveal (P4 )-2 to have a single path for geometry-modification along its flat conformational space, certifying it as a chiral flexible shape-persistent macrocycle. Geometric quantification of chirality has been used to compare the spiranic derivatives presented herein.

Opening access to new chiral macrocycles: from allenes to spiranes.

Chiral macrocycles offer great potential and versatility regarding their applications. They have been employed in asymmetric catalysts, as chiral sensors, and as chiral supramolecular frameworks. For these reasons, they have been attracting increasing interest over the years. Despite all of the work developed in this area, most of the reported chiral macrocycles are not conformationally stable and present weak chiroptical responses. Such features substantially limit the scope of applications for these compounds. On the other hand, we have shown that axially chiral allenes can be introduced into macrocycles, conferring conformational stability and outstanding chiroptical responses. However, these allenes photoisomerize when conjugated with electron-donating groups, hampering the possibility of synthesizing systems with tuned optical properties. To overcome all of these limitations with a single structural motif, we propose the use of spiranes to construct new stable, conformationally rigid, and chemically functionalizable macrocyclic structures with strong chiroptical responses. As a first step in this new direction, we theoretically predict the chiroptical responses for macrocycles bearing spiranes to be as strong as with their allenic counterparts. As a side product, we also test the popular Minnesota functional, M06-2X, and compare it with cam-B3LYP, which has been previously analyzed with respect to experimental data in our laboratory. Thus, we hereby propose that spiranes are a good alternative to allenes for the construction of new chiral macrocycles.

Conformational stable alleno-acetylenic cyclophanes bearing chiral axes.

The design and synthesis of chiral cyclophanes containing signaling functional groups as an integral part of the macrocyclic framework offer promising possibilities for chiral sensing, molecular recognition, and chiral supramolecular architectures. Our research group has been involved in the construction and study of chiroptical properties of several allenic meta- and para-cyclophanes bearing anthracene and pyridine rings as spacers. A revision of our results is presented.

Double Protonation of a cis-Bipyridoallenophane Detected via Chiral-Sensing Switch: The Role of Ion Pairs.

We prove that the confinement of the conformational space of pyridoallenophanes leads to intense chiroptical responses. Unlike the cyclic dimer [142], single-conformation [141]pyridoallenophanes isomerize under thermal and photochemical conditions. Yet, less-strained [141]-bipyridoallenophanes are stable and are prepared successfully. They, unexpectedly, undergo double protonation as a result of cooperative ion-pairing and hydrogen bonding. The complex formation forces a single configuration of the axis connecting both pyridyl rings recognized by a diagnostic circular dichroism (CD) signal at 330 nm.

Synthesis of distorted nanographenes containing seven- and eight-membered carbocycles.

This feature article focuses on the bottom-up approaches (solution-phase) based on organic synthesis for the preparation of saddle-shaped distorted polycyclic aromatic hydrocarbons (PAHs). We summarise the recent progress on the synthetic strategies followed to obtain well-defined nanographenes containing heptagonal and octagonal carbocycles, highlighting the novel strategy developed by our group together with our recent contributions in the area of distorted aromatics. The presence of seven- or eight-membered rings induces a saddle-shape curvature in the planar network pushing the structure out of the plane, which influences the physical properties exhibited. Some brief details on the optical and electronic properties of these curved nanostructures are also discussed.

Preparation and characterization of a halogen-bonded shape-persistent chiral alleno-acetylenic inclusion complex.

A chiral bidentate inclusion complex has been formed by halogen-bond interaction between the pyridyl moieties of a pyridoallenoacetylenic host and octafluorodiiodobutane. X-ray crystallography showed that the guest adopts a chiral conformation inside the molecular channels formed by stacking of the host units. A 10 ppm shielding of the (15)N NMR resonance for the pyridil units provided evidence of the formation of the halogen-bond complex in solution.

Morphological self-assembly of enantiopure allenes for upstanding chiral architectures at interfaces.

Chiroptically active allenes are employed for the construction of surface-confined nanostructures. Morphological complementarity between the homochiral units leads to self-assembly of two highly-ordered, upstanding, diastereomeric architectures. The novel, intertwined self-assembled layer structures feature reactive terminal alkynes for further functionalization and carry potential for widespread applications exploiting chiroptical amplification.

Análisis y evaluación de la enfermera referente del paciente en hemodiálisis / Analysis and assessment of the referring nurse of patients on haemodialysis

La enfermera referente es una pieza clave para ofertar cuidados de calidad. Nuestro objetivo ha sido conocer como evalúan los pacientes la figura de la enfermera referente en nuestra unidad de hemodiálisis, para revisar y actualizar su rol y sus tareas. Se seleccionó una muestra de 51 pacientes crónicos que acuden a hemodiálisis en nuestro centro a los que se entregó una encuesta anónima, auto-administrada, diseñada y validada por el personal de la unidad. Los resultados obtenidos indican que los pacientes evalúan positivamente a la enfermera referente confirmándose la utilidad y relevancia de la misma. Sus respuestas definen un perfil básico de enfermera referente: una profesional a la que conocen por su nombre, amable y cortés, con la que se comunican frecuentemente, con extensa formación y experta en su trabajo, capacitada y dispuesta a resolver las dudas y problemas que los pacientes plantean. En definitiva, su enfermera de confianza. Las aportaciones de los encuestados para mejorarlos cuidados, nos sugieren proporcionar más información sobre la dieta y proporcionar espacios de intimidad para la comunicación enfermera-paciente (AU)

The referring nurse is a key element in offering qualitycare. Our aim was to find out how patients assess the referring nurse in our haemodialysis unit, in order to review and update her role and tasks. A sample of 51 chronic patients undergoing haemodialysis in our centre was selected and these patients were given an anonymous self-administered questionnaire, designed and validated by staff of the unit. The results obtained show that patients value there ferring nurse positively, confirming her usefulness and relevance. Their replies define a basic profile for a referring nurse: a professional they know by name, friendly and polite, with whom they communicate frequently, with extensive training and an expert in her work, capable of and willing to over come the doubts and problems that patients raise. In short, the nurse they trust. The contributions of the questionnaire respondents for improving care suggest that we provide more information about diet and provide areas of privacy for nurse-patient communication (AU)