Latin American surgical outcomes study: study protocol for a multicentre international observational cohort study of patient outcomes after surgery in Latin American countries.

Background: Reported data suggest that 4.2 million deaths will occur within 30 days of surgery worldwide each year, half of which are in low- and middle-income countries. Postoperative complications are a leading cause of long-term morbidity and mortality. Patients who survive and leave the hospital after surgical complications regularly experience reductions in long-term survival and functional independence, resulting in increased costs. With a high volume of surgery performed, there is a growing perception of the substantial impact of even minor enhancements in perioperative care. The Latin American Surgical Outcomes Study (LASOS) is an international, multicentre, prospective cohort study of adults submitted to in-patient surgery in Latin America aiming to provide detailed data describing postoperative complications and surgical mortality. Methods: LASOS is a 7 day cohort study of adults undergoing surgery in Latin America. Details of preoperative risk factors, intraoperative care, and postoperative outcomes will be collected. The primary outcome will be in-hospital postoperative complications of any cause. Secondary outcomes include in-hospital all-cause mortality, duration of hospital stay after surgery, and admission to a critical care unit within 30 days after surgery during the index hospitalisation. Results: The LASOS results will be published in peer-reviewed journals, reported and presented at international meetings, and widely disseminated to patients and public in participating countries via mainstream and social media. Conclusions: The LASOS may augment our understanding of postoperative complications and surgial mortality in Latin America. Clinical trial registration: NCT05169164.

Triplet exciton generation in bulk-heterojunction solar cells based on endohedral fullerenes.

Organic bulk-heterojunctions (BHJ) and solar cells containing the trimetallic nitride endohedral fullerene 1-[3-(2-ethyl)hexoxy carbonyl]propyl-1-phenyl-Lu(3)N@C(80) (Lu(3)N@C(80)-PCBEH) show an open circuit voltage (V(OC)) 0.3 V higher than similar devices with [6,6]-phenyl-C[61]-butyric acid methyl ester (PC(61)BM). To fully exploit the potential of this acceptor molecule with respect to the power conversion efficiency (PCE) of solar cells, the short circuit current (J(SC)) should be improved to become competitive with the state of the art solar cells. Here, we address factors influencing the J(SC) in blends containing the high voltage absorber Lu(3)N@C(80)-PCBEH in view of both photogeneration but also transport and extraction of charge carriers. We apply optical, charge carrier extraction, morphology, and spin-sensitive techniques. In blends containing Lu(3)N@C(80)-PCBEH, we found 2 times weaker photoluminescence quenching, remainders of interchain excitons, and, most remarkably, triplet excitons formed on the polymer chain, which were absent in the reference P3HT:PC(61)BM blends. We show that electron back transfer to the triplet state along with the lower exciton dissociation yield due to intramolecular charge transfer in Lu(3)N@C(80)-PCBEH are responsible for the reduced photocurrent.

Electrochemical considerations for determining absolute frontier orbital energy levels of conjugated polymers for solar cell applications.

Narrow bandgap conjugated polymers in combination with fullerene acceptors are under intense investigation in the field of organic photovoltaics (OPVs). The open circuit voltage, and thereby the power conversion efficiency, of the devices is related to the offset of the frontier orbital energy levels of the donor and acceptor components, which are widely determined by cyclic voltammetry. Inconsistencies have appeared in the use of the ferrocenium/ferrocene (Fc + /Fc) redox couple, as well as the values used for the absolute potentials of standard electrodes, which can complicate the comparison of materials properties and determination of structure/property relationships.

Endohedral fullerenes for organic photovoltaic devices.

So far, one of the fundamental limitations of organic photovoltaic (OPV) device power conversion efficiencies (PCEs) has been the low voltage output caused by a molecular orbital mismatch between the donor polymer and acceptor molecules. Here, we present a means of addressing the low voltage output by introducing novel trimetallic nitride endohedral fullerenes (TNEFs) as acceptor materials for use in photovoltaic devices. TNEFs were discovered in 1999 by Stevenson et al. ; for the first time derivatives of the TNEF acceptor, Lu(3)N@C(80), are synthesized and integrated into OPV devices. The reduced energy offset of the molecular orbitals of Lu(3)N@C(80) to the donor, poly(3-hexyl)thiophene (P3HT), reduces energy losses in the charge transfer process and increases the open circuit voltage (Voc) to 260 mV above reference devices made with [6,6]-phenyl-C(61)-butyric methyl ester (C(60)-PCBM) acceptor. PCEs >4% have been observed using P3HT as the donor material. This work clears a path towards higher PCEs in OPV devices by demonstrating that high-yield charge separation can occur with OPV systems that have a reduced donor/acceptor lowest unoccupied molecular orbital energy offset.

Metal nitride cluster fullerene M3N@C80 (M=Y, Sc) based dyads: synthesis, and electrochemical, theoretical and photophysical studies.

The first pyrrolidine and cyclopropane derivatives of the trimetallic nitride templated (TNT) endohedral metallofullerenes I(h)-Sc(3)N@C(80) and I(h)-Y(3)N@C(80) connected to an electron-donor unit (i.e., tetrathiafulvalene, phthalocyanine or ferrocene) were successfully prepared by 1,3-dipolar cycloaddition reactions of azomethine ylides and Bingel-Hirsch-type reactions. Electrochemical studies confirmed the formation of the [6,6] regioisomers for the Y(3)N@C(80)-based dyads and the [5,6] regioisomers in the case of Sc(3)N@C(80)-based dyads. Similar to other TNT endohedral metallofullerene systems previously synthesized, irreversible reductive behavior was observed for the [6,6]-Y(3)N@C(80)-based dyads, whereas the [5,6]-Sc(3)N@C(80)-based dyads exhibited reversible reductive electrochemistry. Density functional calculations were also carried out on these dyads confirming the importance of these structures as electron transfer model systems. Furthermore, photophysical investigations on a ferrocenyl-Sc(3)N@C(80)-fulleropyrrolidine dyad demonstrated the existence of a photoinduced electron-transfer process that yields a radical ion pair with a lifetime three times longer than that obtained for the analogous C(60) dyad.

"Open rather than closed" malonate methano-fullerene derivatives. The formation of methanofulleroid adducts of Y3N@C80.

Cycloaddition of bromomalonates to Y3N@C80 unexpectedly gave rise to fulleroid derivatives with unusually high stability. Complete characterization of these derivatives is described including X-ray crystallography, 1H NMR, 13C NMR, HMQC, UV-visible, HPLC, MALDI-MS, and electrochemistry. Density functional theory calculations are also presented, which provide a rationale for the formation of the fulleroid and reveal the underlying thermodynamic basis for their stability.

1H NMR spectroscopic studies of the conformational isomers of pyrrolidinofullerenes.

Mixed bis-adduct derivatives of C60 containing a pyrrolidine and a malonate methano group were synthesized. Three regioisomers, the e', the trans-2, and the trans-3, were isolated and characterized. In-depth NMR studies of these methano-pyrrolidinofullerenes showed that the nitrogen inversion on the pyrrolidine moiety is not a fast event in the 1H NMR time scale as previously regarded. Solvent effects, variable temperature experiments, and protonation of the pyrrolidine nitrogen are addressed.

Reactivity differences between carbon nano onions (CNOs) prepared by different methods.

The carbon nanoparticles obtained from either arcing of graphite under water or thermal annealing of nanodiamonds are commonly called carbon nano onions (CNOs), or spherical graphite, as they are made of concentric fullerene cages separated by the same distance as the shells of graphite. A more careful analysis reveals some dramatic differences between the particles obtained by these two synthetic methods. Physicochemical methods indicate that the CNOs obtained from nanodiamonds (N-CNOs) are smaller and contain more defects than the CNOs obtained from arcing (A-CNOs). These properties explain the enhanced reactivity of the N-CNOs in cycloaddition and oxidation reactions, as well as in reactions involving radicals. Given the easier functionalization of the N-CNOs, they are the most obvious choice for studying the potential applications of these multi-shelled fullerenes.

X-Ray crystallographic and EPR spectroscopic characterization of a pyrrolidine adduct of Y3N@C80.

Crystallographic data for the pyrrolidine adduct Y3N@C80C4H9N x 2.5CS2 reveals a slightly pyramidalized Y3N unit with idealized mirror symmetry that straddles the site of addition but does not directly interact with the addend.

Unexpected chemical and electrochemical properties of M3N@C80 (M = Sc, Y, Er).

The unexpected isomerization of N-ethyl [6,6]-pyrrolidino-Y3N@C80 to the [5,6] regioisomer is reported, as well as the synthesis, characterization, and electrochemical analysis of Er3N@C80 derivatives. A complete electrochemical study of the M3N@C80 species (M = Sc, Y, Er) and their derivatives is presented. We introduce electrochemistry as a new tool in the characterization of the [5,6] and [6,6] regioisomers of trimetallic nitride endohedral metallofullerenes.

Ion recognition properties of self-assembled monolayers (SAMs).

In the search for new sensors, self-assembled monolayers (SAMs) have gained intensive interest due to their nanometre size, highly-ordered structures, and molecular recognition properties. This article presents an overview of ion recognition at SAM-modified surface/solution interfaces, and brings up to date the most notable examples for the sensing of cations and anions. Sensing is achieved with SAMs containing redox active and inactive receptors using techniques such as fluorescence spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy.

Trimetallic nitride endohedral metallofullerenes: reactivity dictated by the encapsulated metal cluster.

The first derivatives of Y(3)N@C(80) have been synthesized and fully characterized. 1,3-Dipolar cycloaddition of N-ethylazomethine ylide yielded mainly the pyrrolidine monoadduct of the icosahedral (I(h)()) symmetry cage exclusively at a [6,6] double bond. The same regioselectivity on a [6,6] double bond was observed when the endohedral compound was cyclopropanated with diethyl bromomalonate. These results are in pronounced contrast to those observed for icosahedral symmetry Sc(3)N@C(80), for which all reported derivatives add completely regioselectively to [5,6] double bonds. (1)H NMR, (13)C NMR, and HMQC spectroscopy revealed that the addition pattern on Y(3)N@C(80) resulted in a pyrrolidinofullerene derivative with unsymmetric pyrrolidine carbons and symmetric geminal protons. The cyclopropanated monoadduct exhibited symmetric ethyl groups on the malonate, consistent with regioselective addition at a [6,6] double bond. Attempts to perform the same cyclopropanation reaction on (I(h)()) Sc(3)N@C(80) failed to yield any identifiable products. These observations clearly indicate that the reactivity of trimetallic nitride endohedral metallofullerenes toward exohedral chemical functionalization is profoundly affected and effectively controlled by the nature of the endohedral metal cluster.

Heptapeptide mimic of ohmefentanyl binding in the discontinuous mu-opiod receptor.

[reaction: see text] Ohmefentanyl binds to the rat mu-opiod receptor via two dipeptide sequences (Trp-His and Asp-Tyr) that are separated by 170 residues. A turn-inducing tripeptide, Pro-Aib-Aib, holds the dipeptides in a conformation that binds the narcotic (K(b) = 7.1 x 10(4) M(-)(1)) in THF. Binding is specific for ohmefentanyl over morphine and is accompanied by a conformational change in the heptapeptide host. Control experiments with a Gly-Gly-Gly tripeptide linking the dipeptides show no evidence of binding.

The first fulleropyrrolidine derivative of Sc3N@C80: pronounced chemical shift differences of the geminal protons on the pyrrolidine ring.

The first pyrrolidine adduct on Sc(3)N@C(80) was synthesized and fully characterized. Addition of the N-ethylazomethine ylide occurs regioselectively on a [5,6] double bond on the surface of the icosahedral symmetry Sc(3)N@C(80), exactly in the same position as that described previously for a Diels-Alder adduct of the same compound.(11a,b) This addition pattern results in symmetric pyrrolidine carbons and unsymmetric geminal hydrogens on the pyrrolidine ring, as confirmed by (1)H and (13)C NMR spectroscopy, especially by HMQC. The shielding environment experienced by these geminal hydrogens differs by 1.26 ppm, indicative of pronounced ring current effects on the surface of this endohedral fullerene. This represents the first fully characterized pyrrolidine adduct on an endohedral metallofullerene.

Chemosensors for the marine toxin saxitoxin.

Eleven anthracylmethyl crown ethers have been synthesized and evaluated as fluorescence sensors for the marine toxin saxitoxin. Fluorescence enhancement data are consistent with a 1:1 binding complex for all crowns. The binding constants are in the range of 10(4) M(-)(1) in ammonium phosphate buffer (pH 7.1) in 80% ethanol solvent. Selectivity for sensing saxitoxin versus several organic analytes has been demonstrated for the first time. Possible modes of binding are presented, and relevance to saxitoxin monitoring programs are discussed.

An improved synthesis of a trifurcated newkome-type monomer and orthogonally protected two-generation dendrons.

The one-step synthesis of amino-polyether tri-tert-butyl ester monomer 2, by condensation of TRIS with tert-butyl acrylate, is reported. The nitrogen of the monomer can be protected with a Cbz group; subsequent removal of the tert-butyl esters with formic acid affords a triacid that is coupled to three monomers to afford an orthogonally protected two-generation, trifurcated polyether-polyamide dendron. The Cbz protecting group may be removed from the second-generation dendron without disturbing the tert-butyl esters of the periphery.