Medium Diradical Character, Small Hole and Electron Reorganization Energies and Ambipolar Transistors in Difluorenoheteroles

Four difluorenoheteroles having a central quinoidal core with the heteroring varying as furan, thiophene, its dioxide derivative and pyrrole have shown to be medium character diradicals. Solid-state structures, optical, photophysical, magnetic, and electrochemical properties have been discussed in terms of diradical character, variation of aromatic character and captodative effects (electron affinity). Organic field-effect transistors (OFETs) have been prepared, showing balanced hole and electron mobilities of the order of 10^-3  cm²  V^-1  s^-1 or ambipolar charge transport which is first inferred from their redox amphoterism. Quantum chemical calculations show that the electrical behavior is originated from the medium diradical character which produces similar reorganization energies for hole and electron transports. The vision of a diradical as simultaneously bearing pseudo-hole and pseudo-electron defects might justify the reduced values of reorganization energies for both regimes. Structure-function relationships between diradical and ambipolar electrical behavior are revealed.

Strain Switching in van der Waals Heterostructures Triggered by a Spin-Crossover Metal-Organic Framework

Van der Waals heterostructures (vdWHs) provide the possibility of engineering new materials with emergent functionalities that are not accessible in another way. These heterostructures are formed by assembling layers of different materials used as building blocks. Beyond inorganic 2D crystals, layered molecular materials remain still rather unexplored, with only few examples regarding their isolation as atomically thin layers. Here, the family of van der Waals heterostructures is enlarged by introducing a molecular building block able to produce strain: the so-called spin-crossover (SCO). In these metal-organic materials, a spin transition can be induced by applying external stimuli like light, temperature, pressure, or an electric field. In particular, smart vdWHs are prepared in which the electronic and optical properties of the 2D material (graphene and WSe₂ ) are clearly switched by the strain concomitant to the spin transition. These molecular/inorganic vdWHs represent the deterministic incorporation of bistable molecular layers with other 2D crystals of interest in the emergent fields of straintronics and band engineering in low-dimensional materials.

A Trapezoidal Octacyanoquinoid Acceptor Forms Solution and Surface Products by Antiparallel Shape Fitting with Conformational Dipole Momentum Switch

A new compound (1) formed by two antiparallelly disposed tetracyano thienoquinoidal units has been synthesized and studied by electrochemistry, UV/Vis-NIR, IR, EPR, and transient spectroscopy. Self-assembly of 1 on a Au(111) surface has been investigated by scanning tunneling microscopy. Experiments have been rationalized by quantum chemical calculations. 1 exhibits a unique charge distribution in its anionic form, with a gradient of charge yielding a neat molecular in-plane electric dipole momentum, which transforms out-of-plane after surface deposition due to twisted→folded conformational change and to partial charge transfer from Au(111). Intermolecular van der Waals interactions and antiparallel trapezoidal shape fitting lead to the formation of an optimal dense on Au(111) two-dimensional assembly of 1.

A nitrogen-doped asymmetric phenalenyl with a zwitterionic ground state

Herein, an asymmetric N-doped phenalenyl (BTAP) compound has been synthesized and carefully studied for the first time. The synthesis of BTAP reveals a planar configuration and an unexpected zwitterionic ground state with the negative charge delocalized around the circumjacent part and the positive charge mainly localized on the center.

Raman and ROA analyses of twisted anthracenes: connecting vibrational and electronic/photonic structures

In this article the Raman and Raman Optical Activity (ROA) spectra of a series of enantiomeric twisted anthracenes are presented. The evolution of their vibrational spectra is understood in the context of the variation of π-electron delocalization as a result of the twisting imparted by the belt structure and in terms of the modulation of the resonance Raman/ROA effects which are photonic properties also tuned by anthracene twisting. The Raman/ROA vibrational spectra are simulated by several theoretical approaches to account for their vibrational and electronic properties including the theoretical evaluation of resonance effects. We furthermore incorporate a vibrational and ROA activity dissection analysis as provided in the Pyvib2 program valid to establish correlations among vibrational modes of different molecules with different electronic structures and equivalent vibrational dynamics. This paper is one of the very first attempts to use ROA spectroscopy in π-conjugated molecules with twisted and helical morphologies that contrast with the well-known cases of ROA studies of chiral helicenes in which the impact of π-electron delocalization in the electronic/photonic/vibrational (Raman/ROA) spectra is negligible.

Consensus on basic conduct during the hospital admission of patients with acute heart failure

Acute heart failure (AHF) is a highly prevalent clinical entity in individuals older than 45years in Spain. AHF is associated with significant morbidity and mortality and is the leading cause of hospitalisation for individuals older than 65years in Spain, a quarter of whom die within 1year of the hospitalisation. In recent years, there has been an upwards trend in hospitalisations for AHF, which increased 76.7% from 2003 to 2013. Readmissions at 30days for AHF have also increased (from 17.6% to 22.1%), at a relative mean rate of 1.36% per year, with the consequent increase in the use of resources and the economic burden for the healthcare system. The aim of this document (developed by the Heart Failure and Atrial Fibrillation Group of the Spanish Society of Internal Medicine) is to guide specialists on the most important aspects of treatment and follow-up for patients with AHF during hospitalisation and the subsequent follow-up. The main recommendations listed in this document are as follows: (1)At admission, perform a comprehensive assessment, considering the patient's standard treatment and comorbidities, given that these determine the disease prognosis to a considerable measure. (2)During the first few hours of hospital care, decongestive treatment is a priority, and a staged diuretic therapeutic approach based on the patient's response is recommended. (3)To manage patients in the stable phase, consider starting and/or adjusting evidence-based drug treatment (e.g., sacubitril/valsartan or angiotensin-converting enzyme inhibitors/angiotensinII receptor blockers, beta blockers and aldosterone antagonists). (4)At hospital discharge, use a checklist to optimise the patient's management and identify the most efficient options for maintaining continuity of care after discharge.

Consensus on basic conduct during the hospital admission of patients with acute heart failure

Acute heart failure (AHF) is a highly prevalent clinical entity in individuals older than 45 years in Spain. AHF is associated with significant morbidity and mortality and is the leading cause of hospitalisation for individuals older than 65 years in Spain, a quarter of whom die within 1 year of the hospitalisation. In recent years, there has been an upwards trend in hospitalisations for AHF, which increased 76.7% from 2003 to 2013. Readmissions at 30 days for AHF have also increased (from 17.6% to 22.1%), at a relative mean rate of 1.36% per year, with the consequent increase in the use of resources and the economic burden for the healthcare system. The aim of this document (developed by the Heart Failure and Atrial Fibrillation Group of the Spanish Society of Internal Medicine) is to guide specialists on the most important aspects of treatment and follow-up for patients with AHF during hospitalisation and the subsequent follow-up. The main recommendations listed in this document are as follows: 1) At admission, perform a comprehensive assessment, considering the patient's standard treatment and comorbidities, given that these determine the disease prognosis to a considerable measure. 2) During the first few hours of hospital care, decongestive treatment is a priority, and a staged diuretic therapeutic approach based on the patient's response is recommended. 3) To manage patients in the stable phase, consider starting and/or adjusting evidence-based drug treatment (e.g., sacubitril/valsartan or angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers, beta blockers and aldosterone antagonists). 4) At hospital discharge, use a checklist to optimise the patient's management and identify the most efficient options for maintaining continuity of care after discharge.

Single-molecule conductance in a unique cross-conjugated tetra(aminoaryl)ethene

A 1,1,2,2-tetrakis(4-aminophenyl)ethene with three paths of π-conjugation, linear-cis, linear-trans and a cross-conjugation, has been prepared. The molecule is able to bind to gold electrodes forming molecular junctions for single-molecule conductance measurements. Only two regimes of conduction are found experimentally. The modelling of the conductance allows to assign them to through-bond transmission in the linear case, while the cross-conjugated channel is further assisted by through-space transmission, partially alleviating the destructive quantum interference.

Monoradicals and Diradicals of Dibenzofluoreno[3,2-b]fluorene Isomers: Mechanisms of Electronic Delocalization

The preparation of a series of dibenzo- and tetrabenzo-fused fluoreno[3,2-b]fluorenes is disclosed, and the diradicaloid properties of these molecules are compared with those of a similar, previously reported series of anthracene-based diradicaloids. Insights on the diradical mode of delocalization tuning by constitutional isomerism of the external naphthalenes has been explored by means of the physical approach (dissection of the electronic properties in terms of electronic repulsion and transfer integral) of diradicals. This study has also been extended to the redox species of the two series of compounds and found that the radical cations have the same stabilization mode by delocalization that the neutral diradicals while the radical anions, contrarily, are stabilized by aromatization of the central core. The synthesis of the fluorenofluorene series and their characterization by electronic absorption and vibrational Raman spectroscopies, X-ray diffraction, SQUID measurements, electrochemistry, in situ UV-vis-NIR absorption spectroelectrochemistry, and theoretical calculations are presented. This work attempts to unify the properties of different series of diradicaloids in a common argument as well as the properties of the carbocations and carbanions derived from them.

Synthesis and electronic properties of pyridine end-capped cyclopentadithiophene-vinylene oligomers

A series of four oligomers of cyclopentadithiophene-vinylenes end capped with pyridine groups was prepared and their optical and electronic properties studied. Treatment with trifluoroacetic acid (TFA) leads to the bisprotonation of the nitrogens of the pyridine, which has an important impact on the optical properties. Excess treatment with TFA provokes the oxidation of the conjugated core, generating radical cations and dications. The ease of the TFA treatment in solution was extended to protonation in the solid-state where further characterization of the neutral and TFA-treated samples was carried out in electrically active substrates in organic field-effect transistors. Finally, the new molecules were found to be excellent conductors in single-molecule junctions thanks to strong electron delocalization and resonance orbital mediated transport. These studies show the opening of a spectrum of possibilities by suitable terminal substitution of π-cores.

A Chichibabin's Hydrocarbon-Based Molecular Cage: The Impact of Structural Rigidity on Dynamics, Stability, and Electronic Properties

A three-dimensional π-conjugated polyradicaloid molecular cage c-Ph14, consisting of three Chichibabin's hydrocarbon motifs connected by two benzene-1,3,5-triyl bridgeheads, was synthesized. Compared with its linear model compound l-Ph4, the prism-like c-Ph14 has a more rigid structure, which shows significant impact on the molecular dynamics, stability, and electronic properties. A higher rotation energy barrier for the quinoidal biphenyl units was determined in c-Ph14 (15.64 kcal/mol) than that of l-Ph4 (11.40 kcal/mol) according to variable-temperature NMR measurements, leading to improved stability, a smaller diradical character, and an increased singlet-triplet energy gap. The pressure-dependent Raman spectroscopic studies on the rigid cage c-Ph14 revealed a quinoidal-to-aromatic transformation along the biphenyl bridges. In addition, the ellipsoidal cavity in the cage allowed selective encapsulation of fullerene C₇₀ over C₆₀, with an associate constant of about 1.43 × 10⁴ M^-1. Moreover, c-Ph14 and l-Ph4 exhibited similar redox behavior and their cationic species (c-Ph14⁶⁺ and l-Ph4²⁺) were obtained by chemical oxidation, and the structures were identified by X-ray crystallographic analysis. The biphenyl unit showed a twisted conformation in l-Ph4²⁺ and remained coplanarity in c-Ph14⁶⁺. Notably, molecules of c-Ph14⁶⁺ form a one-dimensional columnar structure via close π-π stacking between the bridgeheads.

Cove-Edged Nanographenes with Localized Double Bonds

The efficient synthesis and electronic properties of two large-size cove-edged nanographenes (NGs), CN1 and CN2, are presented. X-ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1) or six (for CN2) localized C=C double bonds embedded in nine (for CN1) or twelve (for CN2) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations. Furthermore, Raman spectra exhibit a band associated with the longitudinal CC stretching mode of olefinic double bonds. Owing to the existence of the additional olefinic bonds, both compounds show a small band gap (1.84 eV for CN1 and 1.37 eV for CN2). They also display moderate fluorescence quantum yield (35 % for CN1 and 50 % for CN2) owing to the contorted geometry, which can suppress aggregation in solution.