Synthesis of Contorted Polycyclic Aromatic Compounds via Alkyne Benzannulation on Zigzag-Edged Dibenzochrysene Derivatives.

Organic dyes are interesting building blocks for the preparation of organic semiconductors as they possess synthetic handles that can be used to functionalize them and, consequently, change their electronic properties. However, reactions to extend their π-conjugated framework through ring annulation have only been scarcely tested. Herein, we report the use of alkyne benzannulation on 2,8-dibromo-dibenzo[def,mno]chrysene (vat orange 3) and 2,9-dibromo-dibenzo[b,def]chrysene (vat orange 1) to extend the conjugation and reduce their bandgap. Unexpectedly, the ring closure reaction takes place at the most sterically hindered positions (peri to the substituent) to yield contorted polycyclic compounds. More surprisingly, both TIPS-acetylene-functionalized derivatives underwent a tandem dearomative spirocyclization to form bent polycyclic compounds. Absorption spectroscopy reveals that ring annulation on both 2,9-dibromo-dibenzo[b,def]chrysene and 2,8-dibromo-dibenzo[def,mno]chrysene resulted in a decrease of 0.38 and 0.12 eV in bandgap values, respectively, despite inducing a contorted conformation.

π-Extended 4,5-Fused Bis-Fluorene: Highly Open-Shell Compounds and their Cationic Tetrathiafulvalene Derivatives.

The synthesis of diradical organic compounds has garnered significant attention due to their thermally accessible spin inversion and optoelectronic properties. Yet, preparing such stable structures with high open-shell behavior remains challenging. Herein, we report the synthesis and properties of four π-extended, fused fluorene derivatives with high diradical character, taking advantage of a molecular design where the closed-shell does not include any Clar sextet, comparatively to a maximum of 5 in the corresponding open-shell state. This led to an unusual open-shell triplet ground state with an outstanding singlet-triplet energy difference (ΔEST) of ca. 19 kcal/mol, one of the highest values reported to date for an all-carbon conjugated scaffold. Incorporation of dithiafulvene units at each end of the molecule (at the five-membered rings) furnishes extended tetrathiafulvalenes (TTFs) undergoing reversible oxidations to the radical cation and diradical dication. The various pro-aromatic structures presented herein show highly localized spin density and a limited conjugation due to the confined π-electrons in the aromatic cycles, as supported by 1H NMR, UV/Visible, EPR spectroscopy and DFT calculations.

Annulated Azuleno[2,1,8-ija]azulenes: Synthesis and Properties.

Non-alternant non-benzenoid hydrocarbons exhibit very different optical and electronic properties than their well-studied benzenoid analogues. However, preparing such structures with extended conjugation length, remains challenging. Herein, we report the synthesis and properties of azuleno[2,1,8-ija]azulene derivatives using a two-step sequence involving a four-fold aldol condensation between aromatic dialdehydes and readily available tetrahydropentalene-2,5-(1H,3H)-dione. Molecules with band gap values ranging from 1.69 to 2.14 eV and molar extinction coefficients (ϵ) of nearly 3×105  M-1 cm-1 have been prepared. These annulene-like structures exhibit significant diatropic ring currents (aromatic), as supported by 1 H NMR spectroscopy and DFT calculations. Field-effect transistors (OFETs) using azuleno[2,1,8-ija]azulene derivatives as semiconductors exhibit charge mobility values of up to 0.05 cm2  V-1 s-1 .

Pyrrole-Embedded Linear and Helical Graphene Nanoribbons.

Linear and helical graphene nanoribbons (L-PyGNR and H-PyGNR) bearing electron-rich pyrrole units have been synthesized by using the photochemical cyclodehydrochlorination (CDHC) reaction. The pyrrole units in the polymer backbone make the polymer electron-rich with moderate bandgap values and relatively high HOMO energy levels. The planarization of the pyrrole unit through cyclization yields a bandgap value almost 0.5 eV lower than that measured for polypyrrole. Conductivity values in the thin film up to 0.12 S/cm were measured for the chemically oxidized L-PyGNR (four-point method). Both GNRs showed excellent fluorescence sensing properties for TNT in solution with KSV values up to 6.4 × 106 M-1.

Sarcopenia in cardiac surgery: Dual X-ray absorptiometry study from the McGill frailty registry.

BACKGROUND: To determine the prevalence and prognostic value of sarcopenia measured by dual x-ray absorptiometry (DXA) and physical performance tests in patients undergoing coronary artery bypass surgery or heart valve procedures. METHODS: Adults undergoing cardiac surgery were prospectively enrolled and completed a questionnaire, physical performance battery, and a DXA scan (GE Lunar) to measure appendicular muscle mass indexed to height2 (AMMI). Patients were categorized as sarcopenic based on European Working Group 2 guidelines if they had low AMMI defined as <7 kg/m2 for men or <5.5 kg/m2 for women, and low muscle strength defined as 5 chair rise time ≥15 seconds. Cox proportional hazards regression was used to test the association between sarcopenia and all-cause mortality over a median follow-up of 4.3 years. RESULTS: The cohort consisted of 141 patients with a mean age of 69.7 ± 10.0 years and 21% females. The prevalence rates of low AMMI, slow chair rise time, and sarcopenia (low AMMI and slow chair rise time) were 24%, 57%, 13%, respectively. The 4-year survival rate was 79% in the non-sarcopenic group as compared to 56% in the sarcopenic group (Log-rank P = 0.01). In the multivariable model, each standard deviation of decreasing AMMI and increasing chair rise time was associated with a hazard ratio for all-cause mortality of 1.84 (95% CI 1.18, 2.86) and 1.79 (95% CI 1.26, 2.54), respectively. CONCLUSION: Lower-extremity muscle strength and DXA-based muscle mass are objective indicators of sarcopenia that are independently predictive of all-cause mortality in older cardiac surgery patients.

Electron Acceptors Based on Cyclopentannulated Anthanthrenes.

We demonstrate the preparation of anthanthrene derivatives with fused five-membered rings. These new derivatives are prepared by a palladium catalyzed cyclopentannulation reaction from precursors derived from the low-cost dye Vat Orange 3 (4,10-dibromoanthanthrone). The new cyclopentaanthanthrene compounds possess reduced optical and electrochemical gaps (∼0.9 eV) compared to anthanthrene derivatives and are electron acceptors with lowest unoccupied molecular orbital energies from ∼ -3.4 to -3.9 eV.

Emerging Bottom-Up Strategies for the Synthesis of Graphene Nanoribbons and Related Structures.

The solution-phase synthesis is one of the most promising strategies for the preparation of well-defined graphene nanoribbons (GNRs) in large scale. To prepare high quality, defect-free GNRs, cycloaromatization reactions need to be very efficient, proceed without side reaction and mild enough to accommodate the presence of various functional groups. In this Minireview, we present the latest synthetic approaches for the synthesis of GNRs and related structures, including alkyne benzannulation, photochemical cyclodehydrohalogenation, Mallory and Pd- and Ni-catalyzed reactions.

Malnutrition and Mortality in Frail and Non-Frail Older Adults Undergoing Aortic Valve Replacement.

BACKGROUND: Older adults undergoing aortic valve replacement (AVR) are at risk for malnutrition. The association between preprocedural nutritional status and midterm mortality has yet to be determined. METHODS: The FRAILTY-AVR (Frailty in Aortic Valve Replacement) prospective multicenter cohort study was conducted between 2012 and 2017 in 14 centers in 3 countries. Patients ≥70 years of age who underwent transcatheter or surgical AVR were eligible. The Mini Nutritional Assessment-Short Form was assessed by trained observers preprocedure, with scores ≤7 of 14 considered malnourished and 8 to 11 of 14 considered at risk for malnutrition. The Short Performance Physical Battery was simultaneously assessed to measure physical frailty, with scores ≤5 of 12 considered severely frail and 6 to 8 of 12 considered mildly frail. The primary outcome was 1-year all-cause mortality, and the secondary outcome was 30-day composite mortality or major morbidity. Multivariable regression models were used to adjust for potential confounders. RESULTS: There were 1158 patients (727 transcatheter AVR and 431 surgical AVR), with 41.5% females, a mean age of 81.3 years, a mean body mass index of 27.5 kg/m2, and a mean Society of Thoracic Surgeons-Predicted Risk of Mortality of 5.1%. Overall, 8.7% of patients were classified as malnourished and 32.8% were at risk for malnutrition. Mini Nutritional Assessment-Short Form scores were modestly correlated with Short Performance Physical Battery scores (Spearman R=0.31, P<0.001). There were 126 deaths in the transcatheter AVR group (19.1 per 100 patient-years) and 30 deaths in the surgical AVR group (7.5 per 100 patient-years). Malnourished patients had a nearly 3-fold higher crude risk of 1-year mortality compared with those with normal nutritional status (28% versus 10%, P<0.001). After adjustment for frailty, Society of Thoracic Surgeons-Predicted Risk of Mortality, and procedure type, preprocedural nutritional status was a significant predictor of 1-year mortality (odds ratio, 1.08 per Mini Nutritional Assessment-Short Form point; 95% CI, 1.01-1.16) and of the 30-day composite safety end point (odds ratio, 1.06 per Mini Nutritional Assessment-Short Form point; 95% CI, 1.001-1.12). CONCLUSIONS: Preprocedural nutritional status is associated with mortality in older adults undergoing AVR. Clinical trials are needed to determine whether pre- and postprocedural nutritional interventions can improve clinical outcomes in these vulnerable patients.

Polycyclic Aromatic Hydrocarbons as Potential Building Blocks for Organic Solar Cells.

Since the discovery of graphene in the early 2000's, polycyclic aromatic hydrocarbons (PAHs) have been resurrected and new synthetic tools have been developed to prepare unprecedented structures with unique properties. One application that has been overlooked for this class of molecules is organic solar cells (OSCs). In this account, we present the recent development in the preparation of moderate to low band gap PAHs that could potentially be used as semiconducting materials in OSCs. Our focus is directed toward all-carbon PAHs as well as their polymeric analogs.

Wurster-Type Nanographenes as Stable Diradical Dications.

Three new and stable diradical dications based on the 4,10-dibromoanthanthrone have been synthesized and characterized. In their dicationic state, the amines show a biradical character in the ground state. Their magnetic properties have been investigated by NMR and EPR spectroscopies. The dicationic salts shows strong and broad optical absorption in the near-infrared region. The main driving force to obtain a ground state biradical is the high steric hindrance that prevents planarization of the diphenylamines with the anthanthrone aromatic core. The radical cations are isolated in two perpendicular π-systems as demonstrated by X-ray diffraction structures. This work provides a new bridging unit in the search for biradical bis(triarylamines) salts.

Wurster-Type Anthanthrene Polyradicaloid Cations.

4,10-dibromoanthanthrone, a highly robust building block, is used to synthesize a bis(triarylamine) polymer. The polymer can be oxidized twice to form a polycationic macromolecule showing magnetic properties by electron paramagnetic resonance spectroscopy. In its dicationic state, the presence of isolated radicals is possible because of the interrupted conjugation between the diphenylamine with the anthanthrone core. The high steric hindrance prevents the planarity of the adjacent groups resulting in a polyradical cationic polymer. The oxidized polymer has a strong absorption in the near-infrared region along with reversible redox stages.

Toward Thiophene-Annulated Graphene Nanoribbons.

Narrow thiophene-edged graphene nanoribbons (GNRs) were prepared from polychlorinated thiophene-containing poly(p-phenylene)s using the photochemical, metal-free cyclodehydrochlorination (CDHC) reaction. 1 H NMR and Raman spectroscopy confirmed the structures of the GNRs. The regioselectivity of the CDHC reaction allows the preparation of both laterally symmetrical and unsymmetrical GNRs and, consequently, the modulation of their optical and electronic properties.

Low-Temperature Synthesis of Carbon-Rich Nanoparticles with a Clickable Surface for Functionalization.

Carbon nanoparticles (CNPs) are promising materials for optoelectronic and biomedical applications thanks to their optical properties, low production cost, and superior biocompatibility compared to traditional semiconductor quantum dots. The countless synthetic methods reported allow a library of diverse CNP structures and optical properties, guiding their subsequent applications. However, the current drawbacks lie mainly within these synthetic processes, as many of them require harsh conditions preventing control over morphology and often generating chemically inert nanoparticles. Thus, more advances on low temperature and controllable synthetic processes are desirable. In this study, we suggest a new strategy to synthesize CNPs with tunable size, while avoiding the use of harsh conditions and allowing easy surface functionalization. The metastable state of polyyne-containing materials appoints them as ideal precursors for low-temperature preparation of carbon-rich structures. Our approach is to synthesize octatetrayne-containing particles prompt to spontaneous reaction, including topochemical polymerization, followed by aromatization, to avoid harsh carbonization steps. For the particle synthesis, the well-known dispersion polymerization process has been adapted for homocoupling of terminal butadiynes, generating the octatetrayne-containing particles. The method was proven reproducible, scalable, and versatile, as the particles' size can be modulated between 50 and 170 nm. Surface functionalization via thiol-yne click chemistry was completed with a pyrene-modified thiol ligand to provide the CNPs with photoactive properties in the visible range. The functionalized particles exhibit fluorescence at 470 nm arising from excimer formation.

Helically Coiled Graphene Nanoribbons.

Graphene is a zero-gap, semiconducting 2D material that exhibits outstanding charge-transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution-phase, bottom-up synthesis is the most promising in terms of structural precision and large-scale production. Herein, we report the synthesis of a well-defined, helically coiled GNR from a polychlorinated poly(m-phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1 H NMR, FT-IR, XPS, TEM, and Raman spectroscopy. This Riemann surface-like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state.

Breaking Bonds and Forming Nanographene Diradicals with Pressure.

New anthanthrone-based polycyclic scaffolds possessing peripheral crowded quinodimethanes have been prepared. While the compounds adopt a closed-shell butterfly-shaped structure in the ground state, a curved-to-planar fluxional inversion is accessible with a low energy barrier through a biradicaloid transition state. Inversion is primarily driven by the release of strain associated with steric hindrance at the peri position of the anthanthrone core; a low-lying diradical state is accessible through planarization of the core, which is attained in solution at moderate temperatures. The most significant aspect of this transformation is that planarization is also achieved by application of mild pressure in the solid state, wherein the diradical remains kinetically trapped. Complementary information from quantum chemistry, 1 H NMR, and Raman spectroscopies, together with magnetic experiments, is consistent with the formation of a nanographene-like structure that possesses radical centers localized at the exo-anthanthrone carbons bearing phenyl substituents.

Operative and Functional Outcome After Pulmonary Endarterectomy for Advanced Thromboembolic Pulmonary Hypertension.

AIM: To evaluate the midterm hemodynamic and functional outcome of pulmonary endarterectomy (PEA) for patients with advanced chronic thromboembolic pulmonary hypertension (CTEPH). METHODS: Thirty-eight consecutive patients underwent PEA for CTEPH from May 2004 to March 2012. All patients were followed prospectively at six months postoperatively and annually thereafter. Each patient underwent serial cardiopulmonary exercise testing (CPET) and transthoracic echocardiography, and were followed for up to four years. RESULTS: Overall, 31.5% (12/38) of patients had Jamieson class II disease while 65.8% (25/38) had class III disease. There were three in-hospital mortalities (7.9%), all of which had baseline pulmonary vasculature resistance (PVR) greater than 1400 dynes-sec-cm(-5) . Preoperative PVR and mean pulmonary artery pressure were 1209 ± 723 dynes-sec-cm(-5) and 50 ± 14 mmHg, respectively, signifying a high-risk operative group. Ninety-seven percent of patients were in NYHA class III or IV preoperatively. At median follow-up of 29 months 89.5% (17/19) of patients were in NYHA class I or II. CPET revealed a progressive increase in peak oxygen consumption from 16.5 ± 4.1 ml/kg/min at first follow-up, to a plateau of 20.2 ± 5.6 ml/kg/min (p = 0.032) at two years. CONCLUSIONS: CPET can be used to quantify progress in functional capacity post-CTEPH, although improvements in peak oxygen consumption plateau at two years.

Regioselective Synthesis of Nanographenes by Photochemical Cyclodehydrochlorination.

Novel nanographenes were prepared by a photochemical cyclodehydrochlorination (CDHC) reaction. Chlorinated precursors were irradiated in acetone in the presence of a base or in pure benzene and underwent multiple (up to four) regioselective cyclization reactions to provide rigid π-conjugated molecules. Pure compounds were recovered in good yields by simple filtration at the end of the reaction. The CDHC reaction showed compatibility with both electron-poor and electron-rich substrates, thus allowing the synthesis of pyridine- and thiophene-fused nanographenes. It also enabled the synthesis of sterically hindered contorted π-conjugated molecules without causing full aromatization. A kinetic study showed that the CDHC reaction under the conditions used is a very fast process, and some reactions are completed within minutes. The CDHC reaction thus shows great potential as an alternative to other reactions involving harsher conditions for the preparation of nanographenes.

Superextended Tetrathiafulvalene: Synthesis, Optoelectronic Properties, Fullerenes Complexation, and Photooxidation Study.

Superextended tetrathiafulvalene compounds were prepared by the substitution of gem-dichlorovinylene with 1,2-benzenedithiol. This strategy allowed for the efficient synthesis of a highly π-extended 9,10-bis(benzo-1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (sExTTF) moiety, which exhibits an intense light absorption in the visible spectrum and a reversible oxidation process. A macrocyclic host for fullerenes containing two sExTTF units was synthesized. Complexation studies revealed that fullerenes promote the photooxidation of the 1,3-dithiolylidene bond. This grants new insights into the nature of the low-energy band that appeared in several reports on fullerene complexation with hosts containing the 1,3-dithiolylidene moiety.

Synthesis and Properties of Rhomboidal Macrocyclic Subunits of Graphdiyne-Like Nanoribbons.

Rhomboidal macrocyclic subunits of graphdiyne-like nanoribbon (GDNR) bearing both alkyne and diyne units, allowing for multichannel π-conjugation, were synthesized using an oxidative Glaser-type ring closing reaction. These subunits, called the "meshes" of the nanoribbon, possess phenyl groups with decyloxy solubilizing chains on each corner. The yields of the ring closing reaction highly depend on the metal (Cu or Pd) catalyst used for the macrocyclization step. Increasing the width of the meshes from one macrocycle to two fused macrocycles resulted in a decrease of the bandgap by 0.23 eV as shown by optical spectroscopy. The optimized geometries of the meshes alongside their HOMO and LUMO orbitals were calculated using DFT calculations at the B3LYP/6-31+G** level of theory. The results showed a nearly planar conformation for both meshes with HOMO and LUMO orbitals entirely delocalized over the molecules.

Synthesis of Carboxylate Cp*Zr(IV) Species: Toward the Formation of Novel Metallocavitands.

With the intent of generating metallocavitands isostructural to species [(CpZr)3(µ(3)-O)(µ(2)-OH)3(κO,O,µ(2)-O2C(R))3](+), the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids was carried out. Depending on the reaction conditions, five new complexes were obtained, which consisted of Cp*2ZrCl(κ(2)-OOCPh) (1), (Cp*ZrCl(κ(2)-OOCPh))2(µ-κ(2)-OOCPh)2 (2), [(Cp*Zr(κ(2)-OOCPh))2(µ-κ(2)-OOCPh)2(µ(2)-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2](µ-Cl)(µ-OH)(µ-O2CC6H5)[Cp*Zr]]2(µ-O2CC6H5)2 (4), and [Cp*ZrCl4][(Cp*Zr)3(κ2-OOC(C6H4Br)3(µ3-O)(µ2-Cl)2(µ2-OH)] [5](+)[Cp*ZrCl4](-). The structural characterization of the five complexes was carried out. Species 3·Et2O exhibits host-guest properties where the diethyl ether molecule is included in a cavity formed by two carboxylate moieties. The secondary interactions between the cavity and the diethyl ether molecule affect the structural parameters of the complex, as demonstrated be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural to the [(CpZr)3(µ(3)-O)(µ(2)-OH)3(κO,O,µ(2)-O2C(R))3](+) metallocavitands.