Site specific redox properties in ligand differentiated di-nickel complexes inspired by the acetyl CoA synthase active site.

Bimetallic transition metal complexes with site-specific redox properties offer a versatile platform for understanding electron polarization, intramolecular electron transfer processes, and customizing electronic and magnetic properties that might impact reactivity and catalyst design. Inspired by the dissymmetric nickel sites in the Acetyl CoA Synthase (ACS) Active Site, three new bimetallic Ni(N2S2)-Ni(S2C2R2) complexes based on Ni(N2S2) metalloligand donor synthons, Nid, in mimicry of the nickel site distal to the redox-active iron sulfur cluster of ACS, and nickel dithiolene receiver units, designated as Nip, the nickel proximal to the 4Fe4S cluster, were combined to explore the influence of ligand environment on electronic structure and redox properties of each unit. The combination of synthons gave a matrix of three S-bridged dinickel complexes, characterized by X-ray crystallography, and appropriate spectroscopies. Computational modeling is connected to the electronic characteristics of the nickel donor and receiver units. This study demonstrated the intricacies of identifying sites of electrochemical redox processes, within multi-metallic systems containing non-innocent ligands.

Development of (NO)Fe(N2S2) as a Metallodithiolate Spin Probe Ligand: A Case Study Approach.

ConspectusThe ubiquity of sulfur-metal connections in nature inspires the design of bi- and multimetallic systems in synthetic inorganic chemistry. Common motifs for biocatalysts developed in evolutionary biology include the placement of metals in close proximity with flexible sulfur bridges as well as the presence of π-acidic/delocalizing ligands. This Account will delve into the development of a (NO)Fe(N2S2) metallodithiolate ligand that harnesses these principles. The Fe(NO) unit is the centroid of a N2S2 donor field, which as a whole is capable of serving as a redox-active, bidentate S-donor ligand. Its paramagnetism as well as the ν(NO) vibrational monitor can be exploited in the development of new classes of heterobimetallic complexes. We offer four examples in which the unpaired electron on the {Fe(NO)}7 unit is spin-paired with adjacent paramagnets in proximal and distal positions.First, the exceptional stability of the (NO)Fe(N2S2)-Fe(NO)2 platform, which permits its isolation and structural characterization at three distinct redox levels, is linked to the charge delocalization occurring on both the Fe(NO) and the Fe(NO)2 supports. This accommodates the formation of a rare nonheme {Fe(NO)}8 triplet state, with a linear configuration. A subsequent FeNi complex, featuring redox-active ligands on both metals (NO on iron and dithiolene on nickel), displayed unexpected physical properties. Our research showed good reversibility in two redox processes, allowing isolation in reduced and oxidized forms. Various spectroscopic and crystallographic analyses confirmed these states, and Mössbauer data supported the redox change at the iron site upon reduction. Oxidation of the complex produced a dimeric dication, revealing an intriguing magnetic behavior. The monomer appears as a spin-coupled diradical between {Fe(NO)}7 and the nickel dithiolene monoradical, while dimerization couples the latter radical units via a Ni2S2 rhomb. Magnetic data (SQUID) on the dimer dication found a singlet ground state with a thermally accessible triplet state that is responsible for magnetism. A theoretical model built on an H4 chain explains this unexpected ferromagnetic low-energy triplet state arising from the antiferromagnetic coupling of a four-radical molecular conglomerate. For comparison, two (NO)Fe(N2S2) were connected through diamagnetic group 10 cations producing diradical trimetallic complexes. Antiferromagnetic coupling is observed between {Fe(NO)}7 units, with exchange coupling constants (J) of -3, -23, and -124 cm-1 for NiII, PdII, and PtII, respectively. This trend is explained by the enhanced covalency and polarizability of sulfur-dense metallodithiolate ligands. A central paramagnetic trans-Cr(NO)(MeCN) receiver unit core results in a cissoid structural topology, influenced by the stereoactivity of the lone pair(s) on the sulfur donors. This {Cr(NO)}5 radical bridge, unlike all previous cases, finds the coupling between the distal Fe(NO) radicals to be ferromagnetic (J = 24 cm-1).The stability and predictability of this S = 1/2 moiety and the steric/electronic properties of the bridging thiolate sulfurs suggest it to be a likely candidate for the development of novel molecular (magnetic) compounds and possibly materials. The role of synthetic inorganic chemistry in designing synthons that permit connections of the (NO)Fe(N2S2) metalloligand is highlighted as well as the properties of the heterobi- and polymetallic complexes derived therefrom.

A single carbon atom controls the geometry and reactivity of CoII(N2S2) complexes.

Three- vs. two-carbon N-to-N connectors give rise to monomeric, tetrahedral N2S2Co(II) (µeff = 4.24 BM) or dimeric [(N2S2)Co(II)]2 (diamagnetic) complexes, respectively. Differences in the derivative products of the Lewis acid receivers, W0(CO)3 and W0(CO)4, illustrate nucleophilicity of the thiolate sulfur lone pairs in each case, as well as their structural control.

Bond Trading: Intramolecular Metal and Ligand Exchange within a NO/Ni/Co Complex.

With the goal of generating hetero-redox levels on metals as well as on nitric oxide (NO), metallodithiolate (N2 S2 )CoIII (NO- ), N2 S2 = N,N- dibenzyl-3,7-diazanonane-1,9-dithiolate, is introduced as ligand to a well-characterized labile [Ni0 (NO)+ ] synthon. The reaction between [Ni0 (NO+ )] and [CoIII (NO- )] has led to a remarkable electronic and ligand redistribution to form a heterobimetallic dinitrosyl cobalt [(N2 S2 )NiII ∙Co(NO)2 ]+ complex with formal two electron oxidation state switches concomitant with the nickel extraction or transfer as NiII into the N2 S2 ligand binding site. To date, this is the first reported heterobimetallic cobalt dinitrosyl complex.

Sulfur Lone Pairs Control Topology in Heterotrimetallic Complexes: An Experimental and Theoretical Study.

Heterotrimetallic complexes with (N2S2)M metallodithiolates, M = Ni2+, [Fe(NO)]2+, and [Co(NO)]2+, as bidentate chelating ligands to a central trans-Cr(NO)(MeCN) unit were characterized as the first members of a new class, NiCrNi, FeCrFe, CoCrCo. The complexes exhibit a cisoid structural topology, ascribed to the stereoactivity of the available lone pair(s) on the sulfur donors, resulting in a dispersed, electropositive pocket from the N/N and N/S hydrocarbon linkers wherein the Cr-NO site is housed. Computational studies explored alternative isomers (transoid and inverted cisoid) that suggest a combination of electronic and steric effects govern the geometrical selectivity. Electrostatic potential maps readily display the dominant electronegative potential from the sulfurs which force the NO to the electropositive pocket. The available S lone pairs work in synergy with the π-withdrawing ability of NO to lift Cr out of the S4 plane toward the NO and stabilize the geometry. The metallodithiolate ligands bound to Cr(NO) thus find structural consistency across the three congeners. Although the dinitrosyl [(bme-dach)Co(NO)-Mo(NO)(MeCN)-(bme-dach)Co(MeCN)][PF6]2 (CoMoCo') analogue displays chemical noninnocence and a partial Mo-Co bond toward (N2S2)Co'(NCCH3) in an "asymmetric butterfly" topology [Guerrero-Almaraz P.Inorg. Chem.2021, 60(21 (21), ), 15975-15979], the stability of the {Cr(NO)}5 unit prohibits such bond rearrangement. Magnetism and EPR studies illustrate spin coupling across the sulfur thiolate sulfur bridges.

Correction: Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic NiII, PdII and PtII tetrathiolate bridges.

[This corrects the article DOI: 10.1039/D3SC01546G.].

Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic NiII, PdII and PtII tetrathiolate bridges.

Reaction of the nitrosylated-iron metallodithiolate ligand, paramagnetic (NO)Fe(N2S2), with [M(CH3CN)n][BF4]2 salts (M = NiII, PdII, and PtII; n = 4 or 6) affords di-radical tri-metallic complexes in a stairstep type arrangement ([FeMFe]2+, M = Ni, Pd, and Pt), with the central group 10 metal held in a MS4 square plane. These isostructural compounds have nearly identical ν(NO) stretching values, isomer shifts, and electrochemical properties, but vary in their magnetic properties. Despite the intramolecular Fe⋯Fe distances of ca. 6 Å, antiferromagnetic coupling is observed between {Fe(NO)}7 units as established by magnetic susceptibility, EPR, and DFT studies. The superexchange interaction through the thiolate sulfur and central metal atoms is on the order of NiII < PdII ≪ PtII with exchange coupling constants (J) of -3, -23, and -124 cm-1, consistent with increased covalency of the M-S bonds (3d < 4d < 5d). This trend is reproduced by DFT calculations with molecular orbital analysis providing insight into the origin of the enhancement in the exchange interaction. Specifically, the magnitude of the exchange interaction correlates surprisingly well with the energy difference between the HOMO and HOMO-1 orbitals of the triplet states, which is reflected in the central metal's contribution to these orbitals. These results demonstrate the ability of sulfur-dense metallodithiolate ligands to engender strong magnetic communication by virtue of their enhanced covalency and polarizability.

Cooperative redox and spin activity from three redox congeners of sulfur-bridged iron nitrosyl and nickel dithiolene complexes.

The synthesis of sulfur-bridged Fe-Ni heterobimetallics was inspired by Nature's strategies to "trick" abundant first row transition metals into enabling 2-electron processes: redox-active ligands (including pendant iron-sulfur clusters) and proximal metals. Our design to have redox-active ligands on each metal, NO on iron and dithiolene on nickel, resulted in the observation of unexpectedly intricate physical properties. The metallodithiolate, (NO)Fe(N2S2), reacts with a labile ligand derivative of [NiII(S2C2Ph2)]0, NiDT, yielding the expected S-bridged neutral adduct, FeNi, containing a doublet {Fe(NO)}7. Good reversibility of two redox events of FeNi led to isolation of reduced and oxidized congeners. Characterization by various spectroscopies and single-crystal X-ray diffraction concluded that reduction of the FeNi parent yielded [FeNi]-, a rare example of a high-spin {Fe(NO)}8, described as linear FeII(NO-). Mössbauer data is diagnostic for the redox change at the {Fe(NO)}7/8 site. Oxidation of FeNi generated the 2[FeNi]+⇌[Fe2Ni2]2+ equilibrium in solution; crystallization yields only the [Fe2Ni2]2+ dimer, isolated as PF6- and BArF- salts. The monomer is a spin-coupled diradical between {Fe(NO)}7 and NiDT+, while dimerization couples the two NiDT+ via a Ni2S2 rhomb. Magnetic susceptibility studies on the dimer found a singlet ground state with a thermally accessible triplet excited state responsible for the magnetism at 300 K (χMT = 0.67 emu·K·mol-1, µeff = 2.31 µB), and detectable by parallel-mode EPR spectroscopy at 20 to 50 K. A theoretical model built on an H4 chain explains this unexpected low energy triplet state arising from a combination of anti- and ferromagnetic coupling of a four-radical molecular conglomerate.

Screening and Risk Evaluation of Organic Contaminants in an Urban Wetland Fed with Wastewater Effluents.

Wastewater release in an urban wetland in Mexico City entails discharging complex mixtures of hundreds of chemical substances into the aquatic system. Therefore, in order to identify the most important contaminants, a GC-MS screening method coupled with deconvolution software was used. LC50 values from ECOSAR and Toxic Units were obtained to identify the organic pollutants-of-concern and to pinpoint the most ecotoxic sites. The results showed that, even though the area has intensive farming, agrochemicals are not of concern. Industrial and domestic groups make up from about 30%-66% of the pollutants for all sites. Of the 189 identified substances, 17 were detected 44% of the time and the Toxic Unit showed that terbutol, coprostanol, and hexadecane were capable of generating considerable adverse effects on the aquatic ecosystem. Total Toxic Units for each site exhibited a decreasing trend as they distanced from the urban and agricultural area.

Ectasia coronaria y miocardiopatía hipertrófica: una entidad infrecuente / Coronary artery ectasia and hypertrophic cardiomyopathy: case report

Resumen Se presenta el caso de un paciente de 54 años que consulta por angina de esfuerzo de 2 años de evolución en quien se identifica una dilatación ectásica del árbol coronario con lesiones ateroscleróticas críticas y miocardiopatía hipertrófica septal obstructiva. Una revisión bibliográfica revela que es una asociación infrecuente de la cual solo existen reportes de casos aislados.

Abstract We present the case of a 54-year-old patient who presented with a history of 2 years with angina. Invasive studies revealed critical coronary artery stenosis coexisting with obstructive hypertrophic miopathy. This is a rare association with only isolated case reports.

Retrasplante cardíaco: reporte de un caso / Cardiac re-transplantation: case report

RESUMEN: El Trasplante cardíaco es la mejor alternativa para la insuficiencia cardíaca terminal, logrando buenos resultados de sobrevida y calidad de vida a largo plazo. Una de las causas más importantes de morbimortalidad es la falla del injerto, la que puede ser secundaria, entre otros, a rechazo agudo y/o vasculopatía y su presencia requiere considerar todas las alternativas terapéuticas, dentro de las cuales está el retrasplante. Los resultados de sobrevida en retrasplante cardíaco son buenos. No obstante, los pacientes presentan los riesgos de una terapia inmunosupresora más intensa, así como el desarrollo recurrente de vasculopatía del injerto. Por lo que se considera una opción en pacientes cuidadosamente seleccionados, dado que la experiencia internacional demuestra que la sobrevida del retrasplante es menor que en el primer trasplante. Presentamos el caso de un paciente trasplantado a los 42 años, quien desarrolla una enfermedad vascular del injerto e insuficiencia cardíaca con capacidad funcional IV, por lo cual se decidió realizar un retrasplante cardíaco.

ABSTRACT: Cardiac transplantation is the best alternative for terminal heart failure, achieving good long-term survival and life quality. One of the most important causes of morbidity and mortality is graft failure, which may be secondary, among others, to acute rejection and / or vasculopathy and its presence requires the consideration of all therapeutic alternatives, re transplantation being one of them. The results of survival in cardiac retransplantation are good; however, they present the risks of a more intense immunosuppressive therapy as well as the recurrent development of graft vasculopathy. Therefore, it is considered an option in carefully selected patients given that international experience shows that the survival of retransplantation is lower than in primary cases. We present the case of a 42 year old transplanted patient , who developed graft vascular disease with progressive deterioration of his ventricular function leading to functional class IV. for which a cardiaccardiac retransplantation was performed.

TEMPO Containing Radical Polymonothiocarbonate Polymers with Regio- and Stereo-Regularities: Synthesis, Characterization, and Electrical Conductivity Studies.

We report the synthesis of a (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) (TEMPO) appended polymonothiocarbonates through the ring-opening copolymerization of (4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (GTEMPO) in the presence of carbonyl sulfide under ambient conditions. We have prepared the atactic and isotactic versions of this polymer, using enantiopure R or S forms of the GTEMPO monomer in the latter instances. Cyclic voltammetry studies revealed both oxidation and reduction events that were characteristic of TEMPO radicals. Electrical conductivity of these polymers was measured as solid-state films after annealing the samples above their glass transition temperatures. At room temperature the isotactic polymer shows much greater conductivity (ca. 10-4  S cm-1 ) than the atactic (ca. 10-7  S cm-1 ), attributed to the well-defined stereochemistry and regulated charge transport pathway of isotactic polymer chains in contrast to the irregular structure of the atactic counterpart.

Linear and Bent Nitric Oxide Ligand Binding in an Asymmetric Butterfly Complex: CoMoCo'.

Two synthetic approaches to install metallodithiolate ligands on molybdenum centers using the synthons [Mo2(CH3CN)10]4+ and (N2S2)Co(NO) [N2S2 = N,N-bis(2-mercaptoethyl)-1,4-diazacycloheptane and NO = nitric oxide], or [Mo(NO)2(CH3CN)4]2+ (CH3CN = acetonitrile) and [(N2S2)Co]2 lead to a bis-nitrosylated, trimetallic dication, CoMoCo'. This unique asymmetric butterfly complex, with S = 1, has a bent NO within the small {Co(NO)}8 wing (denoted as Co), reflecting CoIII(NO-), and is S-bridged to a linear {Mo(NO)}6 diamagnetic unit. The latter is further S-bridged to a pentacoordinate (N2S2)CoIII(CH3CN) donor in the larger wing and is the origin of the two unpaired electrons, denoted as Co'. The asymmetry in Mo-Co distances, 3.33 Šin the Co wing and 2.73 Šin the Co' wing, indicated a Mo-Co' bonding interaction. The transfer of NO from (N2S2)Co(NO) in the former path is needed to cleave the strong quadruple bond in [Mo≣Mo]4+, with the energetic cost compensated for via a one-electron bond between Mo and Co', as indicated by natural bonding orbital analysis.

Comprehensive health evaluation of an urban wetland using quality indices and decision trees.

In a world where pristine water is becoming scarcer, the need to reuse water becomes imperative. In this context explaining the water quality, purpose fitness and the parameters or conditions of the water body to adjust so as to improve its quality, are of great relevance. The goal of the present study was the use of water, riverine, and biodiversity quality indices to assess the condition of the studied urban wetland, since no single index can provide a complete health assessment of a water body. Decision trees were also used to elucidate the best water parameters to mend in order to recover the overall health of the urban wetland. The decision trees identified relevant physicochemical parameters as well as their approximate concentration at which a healthy water environment can be sustained for zooplankton and proved to be a powerful and simple alternative to customary approaches. Suspended particles and phosphates proved to be important parameters with concentrations approximately lower than 88 mg L-1 and 11 mg L-1, respectively, for a good biodiversity index of zooplankton. Ammonia, total coliforms, BOD, nitrates, and sodium were the main parameters that affected the water quality index. The vegetation coverage and its structure were the driving factors in the riverine quality index of the wetland.

[Cardiac myxomas. Analysis of 78 cases]. / Mixoma cardíaco: experiencia de 28 años en resección quirúrgica.

BACKGROUND: The incidence rates of cardiac tumors are low. AIM: To report the clinical presentation of cardiac myxomas and long-term evolution after resection. MATERIAL AND METHODS: Review of a database of surgical patients undergoing surgical resection of a cardiac myxoma in a public hospital between 1990 and 2018. RESULTS: Seventy-eight patients aged 53 ± 15 years (65% females) were included. The most frequent comorbidities were arterial hypertension (40.5%), hypothyroidism (15%) and diabetes mellitus (12%). The main presenting symptoms were dyspnea (33%), neurological deficit secondary to embolism (30%) and acute pulmonary edema (5%). The most common location was the left atrium, in 87%. During surgery, cardiopulmonary bypass and aortic cross-clamp times were 50.2 ± 19.6 and 33.4 ± 15.2 min, respectively. One patient died due to severe neurological involvement. Follow-up was completed in seventy-seven patients, with a mean echocardiographic follow-up time of 10.4 ± 7.7 years. Thirty-four patients were followed for more than 10 years. Six patients (7.7%) died during the follow-up and in six patients (7%) a recurrence was identified. CONCLUSIONS: Cardiac myxoma usually has nonspecific symptoms. Surgical excision offers excellent short and long-term results. Complications and recurrence rates are low in non-hereditary myxomas but obligates to perform echocardiographic follow-up for early diagnosis of recurrence.

Mixoma cardíaco: experiencia de 28 años en resección quirúrgica / Cardiac myxomas. Analysis of 78 cases

Background: The incidence rates of cardiac tumors are low. Aim: To report the clinical presentation of cardiac myxomas and long-term evolution after resection. Material and Methods: Review of a database of surgical patients undergoing surgical resection of a cardiac myxoma in a public hospital between 1990 and 2018. Results: Seventy-eight patients aged 53 ± 15 years (65% females) were included. The most frequent comorbidities were arterial hypertension (40.5%), hypothyroidism (15%) and diabetes mellitus (12%). The main presenting symptoms were dyspnea (33%), neurological deficit secondary to embolism (30%) and acute pulmonary edema (5%). The most common location was the left atrium, in 87%. During surgery, cardiopulmonary bypass and aortic cross-clamp times were 50.2 ± 19.6 and 33.4 ± 15.2 min, respectively. One patient died due to severe neurological involvement. Follow-up was completed in seventy-seven patients, with a mean echocardiographic follow-up time of 10.4 ± 7.7 years. Thirty-four patients were followed for more than 10 years. Six patients (7.7%) died during the follow-up and in six patients (7%) a recurrence was identified. Conclusions: Cardiac myxoma usually has nonspecific symptoms. Surgical excision offers excellent short and long-term results. Complications and recurrence rates are low in non-hereditary myxomas but obligates to perform echocardiographic follow-up for early diagnosis of recurrence.

Sobrevida a 10 años de pacientes egresados luego de cirugía por endocarditis infecciosa en un hospital público / Hospital mortality and long-term survival of 103 patients with infective endocarditis requiring surgery

Background Infective endocarditis (IE) is a serious disease with high mortality, especially among the most severe cases undergoing surgery. Aim To analyze the clinical features, perioperative mortality and long-term survival of patients with infective endocarditis requiring surgery. Material and Methods Review of medical records of patients who underwent heart valve surgery for active infective endocarditis in a public hospital between 1995 and 2008. Demographic characteristics and comorbidities were described. Perioperative and 10 year survival were analyzed retrieving death certificates from the Chilean Identification Service. Results Data from 103 patients aged 46 ± 14 years (74% males) was analyzed. Thirty five percent of patients had an underlying predisposing heart condition such as congenital heart disease in 18.5% and prosthetic valves in 10%. The most common location was the aortic valve and the most common surgical procedure was heart valve replacement with a mechanical prosthetic valve in 87% of the cases. Pathogen identification in blood cultures was achieved in 48% of the cases. The most common causative microorganisms were S. aureus in 12%, coagulase-negative Staphylococcus in 11%, S. viridans in 10% and Enterococcus in 7%. Hospital mortality was 20.4% and ten-year survival was 65%. Conclusions Patients with severe IE requiring surgical treatment still have high perioperative and late mortality.

Arteria coronaria única y cardiopatía coronaria: origen anómalo de la arteria coronaria derecha desde la descendente anterior: casos clínicos / Anomalous origin of the right coronary artery in the middle third of the anterior descending artery: report of two cases

The anomalous origin of the coronary arteries is uncommon and the origin of the right coronary artery from the middle third of the anterior descending artery is a finding of extreme rarity. We report two patients with coronary atherosclerotic disease and with an acute coronary syndrome, in whom a single left coronary artery was found. The clinical and angiographic characteristics and the treatment of these patients are described.

Childhood asthma in low and middle-income countries: Where are we now?

Pediatric asthma has been increasing in LMICs (Low Middle-Income Countries), leading to an important burden for both children and national health systems. Implementing measures to achieve control are influenced by the degree of organization health systems have, the availability and affordability of essential asthma medications, and the effective implementation of asthma programs and asthma guidelines. In this review authors give an updated view of the current situation of these components of asthma management in LMICs.