Influencing the coordination mode of tbta (tbta = tris[(1-benzyl- 1H-1,2,3-triazol-4-yl)methyl]amine) in dicobalt complexes through changes in metal oxidation states

The complexes [(tbta)Co(μ-CA-2H)Co(tbta)(CH3CN)](BF4)21 and [(tbta)Co(μ-OH)2Co(tbta)](BF4)42 (tbta = tris[(1-benzyl- 1H-1,2,3-triazol-4-yl)methyl]amine and CA = chloranilic acid) were synthesized and characterized by X-ray crystallography, SQUID magnetometry and NMR spectroscopy. The reactions to form these complexes deliver 1 as a paramagnetic species containing two high spin Co(II) centers, and 2 as a diamagnetic compound with two low spin Co(III) centers. Structural analysis shows that in 1 the capped-octahedral environment around the Co(II) centers is highly distorted with rather long bonds between the metal and donor atoms. The tbta ligand binds to the Co(II) centers through the three triazole nitrogen donor atoms in a facial form, with the Co–N(amine) distance of 2.494(2) Å acting as a capping bond to the octahedron. In the crystal an unusual observation of one acetonitrile molecule statistically occupying the coordination sites at both Co(II) centers is made. 1 displays a series of intermolecular C–HCl and π–π interactions leading to extended three- dimensional structures in the solid state. These interactions lead to the formation of voids and explain why only one acetonitrile molecule can be bound to the dinuclear complexes. In contrast to 1, the cobalt centers in 2 display a more regular octahedral environment with shorter cobalt–donor atom distances, as would be expected for a low spin Co(III) situation. The tbta ligand acts as a perfect tetradentate ligand in this case with the cobalt–N(amine) distance of 2.012(3) Å falling in the range of a normal bond. Thus, we present the rare instances where the ligand tbta has been observed to bind in a perfectly tetradentate fashion in its metal complexes. The room temperature magnetic moment of 6.30 μB for 1 shows values typical of two high spin Co(II) centers, and this value decreases at temperatures lower than 30 K indicating a weak antiferromagnetic coupling and zero field splitting. Mass spectrometric analysis of 2 provided evidence for the formation of an oxo- bridged dicobalt complex in the gas phase

Influencing the coordination mode of tbta (tbta = tris[(1-benzyl- 1H-1,2,3-triazol-4-yl)methyl]amine) in dicobalt complexes through changes in metal oxidation states

The complexes [(tbta)Co(μ-CA-2H)Co(tbta)(CH3CN)](BF4)21 and [(tbta)Co(μ-OH)2Co(tbta)](BF4)42 (tbta = tris[(1-benzyl- 1H-1,2,3-triazol-4-yl)methyl]amine and CA = chloranilic acid) were synthesized and characterized by X-ray crystallography, SQUID magnetometry and NMR spectroscopy. The reactions to form these complexes deliver 1 as a paramagnetic species containing two high spin Co(II) centers, and 2 as a diamagnetic compound with two low spin Co(III) centers. Structural analysis shows that in 1 the capped-octahedral environment around the Co(II) centers is highly distorted with rather long bonds between the metal and donor atoms. The tbta ligand binds to the Co(II) centers through the three triazole nitrogen donor atoms in a facial form, with the Co–N(amine) distance of 2.494(2) Å acting as a capping bond to the octahedron. In the crystal an unusual observation of one acetonitrile molecule statistically occupying the coordination sites at both Co(II) centers is made. 1 displays a series of intermolecular C–HCl and π–π interactions leading to extended three- dimensional structures in the solid state. These interactions lead to the formation of voids and explain why only one acetonitrile molecule can be bound to the dinuclear complexes. In contrast to 1, the cobalt centers in 2 display a more regular octahedral environment with shorter cobalt–donor atom distances, as would be expected for a low spin Co(III) situation. The tbta ligand acts as a perfect tetradentate ligand in this case with the cobalt–N(amine) distance of 2.012(3) Å falling in the range of a normal bond. Thus, we present the rare instances where the ligand tbta has been observed to bind in a perfectly tetradentate fashion in its metal complexes. The room temperature magnetic moment of 6.30 μB for 1 shows values typical of two high spin Co(II) centers, and this value decreases at temperatures lower than 30 K indicating a weak antiferromagnetic coupling and zero field splitting. Mass spectrometric analysis of 2 provided evidence for the formation of an oxo- bridged dicobalt complex in the gas phase

Probing bistability in FeII and CoII complexes with an unsymmetrically substituted quinonoid ligand

The generation of molecular platforms, the properties of which can be influenced by a variety of external perturbations, is an important goal in the field of functional molecular materials. We present here the synthesis of a new quinonoid ligand platform containing an [O,O,O,N] donor set. The ligand is derived from a chloranilic acid core by using the [NR] (nitrogen atom with a substituent R) for [O] isoelectronic substitution. Mononuclear FeII and CoII complexes have been synthesized with this new ligand. Results obtained from single crystal X-ray crystallography, NMR spectroscopy, (spectro)electrochemistry, SQUID magnetometry, multi-frequency EPR spectroscopy and FIR spectroscopy are used to elucidate the electronic and geometric structures of the complexes. Furthermore, we show here that the spin state of the FeII complex can be influenced by temperature, pressure and light and the CoII complex displays redox-induced spin-state switching. Bistability is observed in the solid-state as well as in solution for the FeII complex. The new ligand presented here, owing to the [NR] group present in it, will likely have more adaptability while investigating switching phenomena compared to its [O,O,O,O] analogues. Thus, such classes of ligands as well as the results obtained on the reversible changes in physical properties of the metal complexes are likely to contribute to the generation of multifunctional molecular materials

Chloridotris(3,5-dimethyl-1H-pyrazole-κN 2)(formato-κO)copper(II)–dichlorido­bis(3,5-dimethyl-1H-pyrazole-κN 2)copper(II) (2/1)

The asymmetric unit of the title compound, [Cu(CHO2)Cl(C5H8N2)3]2·[CuCl2(C5H8N2)2] or 2[A]·[B], contains one A mol­ecule and one half-molecule of B, located on a centre of inversion. The CuII environments in A and B are different. In A, the CuII atom is coordinated by three N atoms from three 3,5-dimethyl-1H-pyrazole (L) ligands, one O atom from a formate ligand and a chloride anion in an axial position [Cu—Cl = 2.4275 (7) Å] in a distorted tetra­gonal–pyramidal geometry. The CuII atom in B is coordinated by two N atoms from two L ligands and two chloride anions [Cu—Cl = 2.2524 (6) Å] in a distorted square-planar geometry. In the crystal, inter­molecular N—H⋯O hydrogen bonds link mol­ecules A into centrosymmetric dimers. Inter­molecular N—H⋯Cl hydrogen bonds further link these dimers with the B mol­ecules, forming chains propagating in [101]

Di- and Tetrairon(III) mu-Oxido Complexes of an N3S-Donor Ligand : Catalyst Precursors for Alkene Oxidations

The new di- and tetranuclear Fe(III) mu-oxido complexes [Fe-4(mu-O)(4) (PTEBIA)(4)]CF3SO3)(4)(CH3CN)(2)] (1a) , [Fe-2(mu-O)Cl-2(PTEBIA)(2)(CF3SO3)(2) (1b), and [Fe-2(mu-O)(HCOO)(2)(PTEBIA)(2)](ClO4)(2) (MeOH) (2) were prepared from the sulfur-containing ligand (2-((2,4-dimethylphenyl)thiO)-N,N-bis ((1-methyl-benzimidazol-2-yl)methyl)ethanamine (PTEBIA). The tetrairon complex 1a features four mu-oxido bridges, while in dinuclear 1b, the sulfur moiety of the ligand occupies one of the six coordination sites of each Fe(III) ion with a long Fe-S distance of 2.814(6) angstrom . In 2, two Fe(III) centers are bridged by one oxido and two formate units, the latter likely formed by methanol oxidation. Complexes 1a and 1 b show broad sulfur-toiron charge transfer bands around 400-430 nm at room temperature, consistent with mononuclear structures featuring Fe-S interactions. In contrast, acetonitrile solutions of 2 display a sulfur-to-iron charge transfer band only at low temperature (228 K) upon addition of H2O2/CH3COOH, with an absorption maximum at 410 nm. Homogeneous oxidative catalytic activity was observed for 1a and 1b using H2O2 as oxidant, but with low product selectivity. High valent iron-oxo intermediates could not be detected by UV-vis spectroscopy or ESI mass spectrometry. Rather, evidence suggest preferential ligand oxidation, in line with the relatively low selectivity and catalytic activity observed in the reactions.Peer reviewe

Bis(acetato-κ2 O,O′)bis­(3,5-dimethyl-1H-pyrazole-κN 2)copper(II)

In the title compound, [Cu(C2H3O2)2(C5H8N2)2], the CuII atom has a distorted tetra­gonal–bipyramidal geometry, with the equatorial plane formed by two N atoms belonging to two 3,5-dimethyl-1H-pyrazole ligands and two O atoms from two acetate anions. The second O atoms of the acetate groups provide elongated Cu—O axial contacts, so that the acetates appear to be coordinated in a pseudo-chelate fashion. The pyrazole ligands are situated in cis positions with respect to each other. In the crystal structure, mol­ecules are linked through inter­molecular N—H⋯O hydrogen bonds, forming a one-dimensional chain

Effect of Hydrocortisone on Mortality and Organ Support in Patients With Severe COVID-19: The REMAP-CAP COVID-19 Corticosteroid Domain Randomized Clinical Trial.

Importance: Evidence regarding corticosteroid use for severe coronavirus disease 2019 (COVID-19) is limited. Objective: To determine whether hydrocortisone improves outcome for patients with severe COVID-19. Design, Setting, and Participants: An ongoing adaptive platform trial testing multiple interventions within multiple therapeutic domains, for example, antiviral agents, corticosteroids, or immunoglobulin. Between March 9 and June 17, 2020, 614 adult patients with suspected or confirmed COVID-19 were enrolled and randomized within at least 1 domain following admission to an intensive care unit (ICU) for respiratory or cardiovascular organ support at 121 sites in 8 countries. Of these, 403 were randomized to open-label interventions within the corticosteroid domain. The domain was halted after results from another trial were released. Follow-up ended August 12, 2020. Interventions: The corticosteroid domain randomized participants to a fixed 7-day course of intravenous hydrocortisone (50 mg or 100 mg every 6 hours) (n = 143), a shock-dependent course (50 mg every 6 hours when shock was clinically evident) (n = 152), or no hydrocortisone (n = 108). Main Outcomes and Measures: The primary end point was organ support-free days (days alive and free of ICU-based respiratory or cardiovascular support) within 21 days, where patients who died were assigned -1 day. The primary analysis was a bayesian cumulative logistic model that included all patients enrolled with severe COVID-19, adjusting for age, sex, site, region, time, assignment to interventions within other domains, and domain and intervention eligibility. Superiority was defined as the posterior probability of an odds ratio greater than 1 (threshold for trial conclusion of superiority >99%). Results: After excluding 19 participants who withdrew consent, there were 384 patients (mean age, 60 years; 29% female) randomized to the fixed-dose (n = 137), shock-dependent (n = 146), and no (n = 101) hydrocortisone groups; 379 (99%) completed the study and were included in the analysis. The mean age for the 3 groups ranged between 59.5 and 60.4 years; most patients were male (range, 70.6%-71.5%); mean body mass index ranged between 29.7 and 30.9; and patients receiving mechanical ventilation ranged between 50.0% and 63.5%. For the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively, the median organ support-free days were 0 (IQR, -1 to 15), 0 (IQR, -1 to 13), and 0 (-1 to 11) days (composed of 30%, 26%, and 33% mortality rates and 11.5, 9.5, and 6 median organ support-free days among survivors). The median adjusted odds ratio and bayesian probability of superiority were 1.43 (95% credible interval, 0.91-2.27) and 93% for fixed-dose hydrocortisone, respectively, and were 1.22 (95% credible interval, 0.76-1.94) and 80% for shock-dependent hydrocortisone compared with no hydrocortisone. Serious adverse events were reported in 4 (3%), 5 (3%), and 1 (1%) patients in the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively. Conclusions and Relevance: Among patients with severe COVID-19, treatment with a 7-day fixed-dose course of hydrocortisone or shock-dependent dosing of hydrocortisone, compared with no hydrocortisone, resulted in 93% and 80% probabilities of superiority with regard to the odds of improvement in organ support-free days within 21 days. However, the trial was stopped early and no treatment strategy met prespecified criteria for statistical superiority, precluding definitive conclusions. Trial Registration: ClinicalTrials.gov Identifier: NCT02735707

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Synthesis, properties and heterogenization of donor-stabilized organoaluminium compounds

In dieser Arbeit wurden neue Organoaluminiumverbindungen mit intramolekularer Stickstoff- und Sauerstoffkoordination synthetisiert und charakterisiert. Aus dem Lithiumsalz des Liganden und dem ensprechenden Dialkylaluminiumchlorid wurden [8-(Dimethylamino)naphthyl]diethyl/diisobutyl-aluminium (2, 4) hergestellt. Bis[8-(dimethylamino)naphthyl]ethylaluminium (3) wurde bei der ersten Reaktion als zweites Produkt isoliert, da das verwendete Diethylaluminiumchlorid noch Ethylaluminiumdichlorid enthielt. Trimethylaluminium und N,N-Dimethylnaphthylamin reagieren zum entsprechenden Addukt (5), das isoliert wurde. Über die Reaktion von Diethyl- und Diisobutylaluminiumchlorid mit den Lithium- oder Grignardverbindungen des Liganden wurden (8-Ethoxynaphthyl)diethylaluminium (7), (2-Methoxybenzyl)diisobutylaluminium (14) und Bis[(2-methoxyphenyl)diisobutylaluminium] (11) erhalten. Viele Reaktionen von Dialkylaluminiumchloriden oder Aluminiumtrichlorid mit Lithium- oder Grignardverbindungen der sauerstoffsubstituierten Liganden führten aber aufgrund von Ligandenaustauschreaktionen zu Verbindungen mit zwei Donorfunktionalitäten: Bis(8-ethoxynaphthyl)aluminiumchlorid (8), Bis(8-methoxynaphthyl)methyl/ethyl-aluminium (9, 10), Bis(2-methoxybenzyl)aluminiumchlorid (12) und Bis(2-methoxybenzyl)methylaluminium (13). Die hergestellten Verbindungen sind nicht mehr pyrophor und wesentlich unempfindlicher gegenüber Luft als herkömmliche Trialkylaluminiumverbindungen. Die Aktivitäten von 4, 7, 10 und 14 in der Ziegler-Natta-Ethenpolymerisation mit Titantetrachlorid als Katalysator wurden ermittelt. Dabei sind 7 und 14 besonders aktive Cokatalysatoren, die die Aktivität des sonst oft verwendeten Triethylaluminiums noch übertreffen. Die Kristallstrukturen von 2 bis 5 und 8 bis 13 wurden bestimmt, darunter auch erstmals strukturell charakterisierte, intramolekular sauerstoffstabilisierte Triorganoaluminium- (9, 10, 13) bzw. Diorganoaluminumchloridverbindungen (8, 12). Die während der Reaktion der donorstabilisierten Organoaluminiumverbindungen mit Titantetrachlorid gebildeten Produkte, die die Polymerisationsaktivität beeinflussen können, wurden mit Hilfe von 1H-NMR-Methoden untersucht. Als Testsubstanzen kamen stickstoffstabilisierte Dimethylaluminiumorganyle zum Einsatz. Neben der Übertragung der Methylgruppen konnte auch indirekt die Übertragung des Donorliganden bei einer Verbindung nachgewiesen werden. Nach der Alkylierung verbleibende Organoaluminiumchloride konnten im Fall einer anderen Verbindung gefunden werden. Die Kristallstrukturen von Lewis-Säure-Base-Komplexen intramolekular donorstabilisierter Dimethylaluminiumalkoxide mit Trimethylaluminium, einer bisher wenig untersuchten Verbindungsklasse, wurden bestimmt und mit ähnlichen Verbindungen aus der Literatur verglichen. Untersucht wurden Alkoxide mit Stickstoff-, Sauerstoff- und Schwefelkoordination. Aus den kristallographischen Daten wurden molekulare Parameter erhalten, die eine Beziehung zwischen den Lewis-Basizitäten des Donoratoms und des Alkoxid-Sauerstoffatoms und einer starken oder weniger starken Stabilisierung bzw. Koordination der jeweiligen Aluminiumzentren herstellen. Eine Reihe von donorstabilisierten Aluminiumverbindungen, Triethylaluminium und Titantetrachlorid wurde heterogenisiert. Als Trägermaterialien kamen selbst synthetisiertes und handelsübliches Magnesiumchlorid zum Einsatz. Es wurde untersucht, ob die für Titantetrachlorid bekannte aktivitätssteigernde Wirkung des Magnesiumchlorids auch bei der Aluminiumverbindung, die als Cokatalysator eingesetzt wird, auftritt. In der Ziegler-Natta-Ethenpolymerisation sind die geträgerten Titantetrachlorid-Katalysatoren bzw. Aluminiumorganyl-Cokatalysatoren aktiver als die ungeträgerten Komponenten. Allerdings ist die geträgerte Aluminiumverbindung nicht fest an die Magnesiumchlorid-Oberfläche gebunden und löst sich unter Polymerisationsbedingungen vom Träger. Das dabei frei werdende Magnesiumchlorid ist für die Steigerung der Aktivität der heterogenen Cokatalysatoren verantwortlich. Eine einfache Zugabe von Magnesiumchlorid zum sonst homogen eingesetzten Katalysator / Cokatalysator bewirkt ebenfalls eine Aktivitätssteigerung

Secondary bonding interactions in biomimetic [2Fe-2S] clusters

A series of synthetic [2Fe-2S] complexes with terminal thiophenolate ligands and tethered ether or thioether moieties has been prepared and investigated in order to provide models for the potential interaction of additional donor atoms with the Fe atoms in biological [2Fe-2S] clusters. X-ray crystal structures have been determined for six new complexes that feature appended Et (1(C)), OMe (1(O)), or SMe (1(S)) groups, or with a methylene group (2(C)), an ether-O (2(O)), or an thioether-S (2(S)) linking two aryl group. The latter two systems provide a constrained chelate arrangement that induces secondary bonding interactions with the ether-O and thioether-S, which is confirmed by density functional theory (DFT) calculations that also reveal significant spin density on those fifth donor atoms. Structural consequences of the secondary bonding interactions are analyzed in detail, and effects on the spectroscopic and electronic properties are probed by UV-vis, Mossbauer, and H-1 NMR spectroscopy, as well by SQUID measurements and cyclic voltammetry. The potential relevance of the findings for biological [2Fe-2S] sites is considered