Binding of Nitriles and Isonitriles to V(III) and Mo(III) Complexes: Ligand vs Metal Controlled Mechanism.

The synthesis and structures of nitrile complexes of V(N[tBu]Ar)3, 2 (Ar = 3,5-Me2C6H3), are described. Thermochemical and kinetic data for their formation were determined by variable temperature Fourier transform infrared (FTIR), calorimetry, and stopped-flow techniques. The extent of back-bonding from metal to coordinated nitrile indicates that electron donation from the metal to the nitrile plays a less prominent role for 2 than for the related complex Mo(N[tBu]Ar)3, 1. Kinetic studies reveal similar rate constants for nitrile binding to 2, but the activation parameters depend critically on the nature of R in RCN. Activation enthalpies range from 2.9 to 7.2 kcal·mol-1, and activation entropies from -9 to -28 cal·mol-1·K-1 in an opposing manner. Density functional theory (DFT) calculations provide a plausible explanation supporting the formation of a π-stacking interaction between a pendant arene of the metal anilide of 2 and the arene substituent on the incoming nitrile in favorable cases. Data for ligand binding to 1 do not exhibit this range of activation parameters and are clustered in a small area centered at ΔH‡ = 5.0 kcal·mol-1 and ΔS‡ = -26 cal·mol-1·K-1. Computational studies are in agreement with the experimental data and indicate a stronger dependence on electronic factors associated with the change in spin state upon ligand binding to 1.

Physical and mental health impact of COVID-19 on children, adolescents, and their families: The Collaborative Outcomes study on Health and Functioning during Infection Times - Children and Adolescents (COH-FIT-C&A).

BACKGROUND: The COVID-19 pandemic has altered daily routines and family functioning, led to closing schools, and dramatically limited social interactions worldwide. Measuring its impact on mental health of vulnerable children and adolescents is crucial. METHODS: The Collaborative Outcomes study on Health and Functioning during Infection Times (COH-FIT - www.coh-fit.com) is an on-line anonymous survey, available in 30 languages, involving >230 investigators from 49 countries supported by national/international professional associations. COH-FIT has thee waves (until the pandemic is declared over by the WHO, and 6-18 months plus 24-36 months after its end). In addition to adults, COH-FIT also includes adolescents (age 14-17 years), and children (age 6-13 years), recruited via non-probability/snowball and representative sampling and assessed via self-rating and parental rating. Non-modifiable/modifiable risk factors/treatment targets to inform prevention/intervention programs to promote health and prevent mental and physical illness in children and adolescents will be generated by COH-FIT. Co-primary outcomes are changes in well-being (WHO-5) and a composite psychopathology P-Score. Multiple behavioral, family, coping strategy and service utilization factors are also assessed, including functioning and quality of life. RESULTS: Up to June 2021, over 13,000 children and adolescents from 59 countries have participated in the COH-FIT project, with representative samples from eleven countries. LIMITATIONS: Cross-sectional and anonymous design. CONCLUSIONS: Evidence generated by COH-FIT will provide an international estimate of the COVID-19 effect on children's, adolescents' and families', mental and physical health, well-being, functioning and quality of life, informing the formulation of present and future evidence-based interventions and policies to minimize adverse effects of the present and future pandemics on youth.

The collaborative outcomes study on health and functioning during infection times in adults (COH-FIT-Adults): Design and methods of an international online survey targeting physical and mental health effects of the COVID-19 pandemic.

BACKGROUND: . High-quality comprehensive data on short-/long-term physical/mental health effects of the COVID-19 pandemic are needed. METHODS: . The Collaborative Outcomes study on Health and Functioning during Infection Times (COH-FIT) is an international, multi-language (n=30) project involving >230 investigators from 49 countries/territories/regions, endorsed by national/international professional associations. COH-FIT is a multi-wave, on-line anonymous, cross-sectional survey [wave 1: 04/2020 until the end of the pandemic, 12 months waves 2/3 starting 6/24 months threreafter] for adults, adolescents (14-17), and children (6-13), utilizing non-probability/snowball and representative sampling. COH-FIT aims to identify non-modifiable/modifiable risk factors/treatment targets to inform prevention/intervention programs to improve social/health outcomes in the general population/vulnerable subgrous during/after COVID-19. In adults, co-primary outcomes are change from pre-COVID-19 to intra-COVID-19 in well-being (WHO-5) and a composite psychopathology P-Score. Key secondary outcomes are a P-extended score, global mental and physical health. Secondary outcomes include health-service utilization/functioning, treatment adherence, functioning, symptoms/behaviors/emotions, substance use, violence, among others. RESULTS: . Starting 04/26/2020, up to 14/07/2021 >151,000 people from 155 countries/territories/regions and six continents have participated. Representative samples of ≥1,000 adults have been collected in 15 countries. Overall, 43.0% had prior physical disorders, 16.3% had prior mental disorders, 26.5% were health care workers, 8.2% were aged ≥65 years, 19.3% were exposed to someone infected with COVID-19, 76.1% had been in quarantine, and 2.1% had been COVID 19-positive. LIMITATIONS: . Cross-sectional survey, preponderance of non-representative participants. CONCLUSIONS: . Results from COH-FIT will comprehensively quantify the impact of COVID-19, seeking to identify high-risk groups in need for acute and long-term intervention, and inform evidence-based health policies/strategies during this/future pandemics.

pH Changes That Induce an Axial Ligand Effect on Nonheme Iron(IV) Oxo Complexes with an Appended Aminopropyl Functionality.

Nonheme iron enzymes often utilize a high-valent iron(IV) oxo species for the biosynthesis of natural products, but their high reactivity often precludes structural and functional studies of these complexes. In this work, a combined experimental and computational study is presented on a biomimetic nonheme iron(IV) oxo complex bearing an aminopyridine macrocyclic ligand and its reactivity toward olefin epoxidation upon changes in the identity and coordination ability of the axial ligand. Herein, we show a dramatic effect of the pH on the oxygen-atom-transfer (OAT) reaction with substrates. In particular, these changes have occurred because of protonation of the axial-bound pendant amine group, where its coordination to iron is replaced by a solvent molecule or anionic ligand. This axial ligand effect influences the catalysis, and we observe enhanced cyclooctene epoxidation yields and turnover numbers in the presence of the unbound protonated pendant amine group. Density functional theory studies were performed to support the experiments and highlight that replacement of the pendant amine with a neutral or anionic ligand dramatically lowers the rate-determining barriers of cyclooctene epoxidation. The computational work further establishes that the change in OAT is due to electrostatic interactions of the pendant amine cation that favorably affect the barrier heights.

How Metal Ion Lewis Acidity and Steric Properties Influence the Barrier to Dioxygen Binding, Peroxo O-O Bond Cleavage, and Reactivity.

Herein we quantitatively investigate how metal ion Lewis acidity and steric properties influence the kinetics and thermodynamics of dioxygen binding versus release from structurally analogous Mn-O2 complexes, as well as the barrier to Mn peroxo O-O bond cleavage, and the reactivity of Mn oxo intermediates. Previously we demonstrated that the steric and electronic properties of MnIII-OOR complexes containing N-heterocyclic (NAr) ligand scaffolds can have a dramatic influence on alkylperoxo O-O bond lengths and the barrier to alkylperoxo O-O bond cleavage. Herein, we examine the dioxygen reactivity of a new MnII complex containing a more electron-rich, less sterically demanding NAr ligand scaffold, and compare it with previously reported MnII complexes. Dioxygen binding is shown to be reversible with complexes containing the more electron-rich metal ions. The kinetic barrier to O2 binding and peroxo O-O bond cleavage is shown to correlate with redox potentials, as well as the steric properties of the supporting NAr ligands. The reaction landscape for the dioxygen chemistry of the more electron-rich complexes is shown to be relatively flat. A total of four intermediates, including a superoxo and peroxo species, are observed with the most electron-rich complex. Two new intermediates are shown to form following the peroxo, which are capable of cleaving strong X-H bonds. In the absence of a sacrificial H atom donor, solvent, or ligand, serves as a source of H atoms. With TEMPOH as sacrificial H atom donor, a deuterium isotope effect is observed (kH/kD = 3.5), implicating a hydrogen atom transfer (HAT) mechanism. With 1,4-cyclohexadiene, 0.5 equiv of benzene is produced prior to the formation of an EPR detected MnIIIMnIV bimetallic species, and 0.5 equiv after its formation.

Kinetic Studies on the Oxoiron(IV) Complex with Tetradentate Aminopyridine Ligand PDP*: Restoration of Catalytic Activity by Reduction with H2O2.

Oxoiron(IV) is a common catalytic byproduct observed in the oxidation of alkenes by the combination of H2O2 and nonheme iron catalysts including complex 1, FeIIPDP* (where PDP* = bis(3,5-dimethyl-4-methoxypyridyl-2-methyl)-(R,R)-2,2'-bipyrrolidine). The oxoiron(IV) species have been proposed to arise by O-O homolysis of the peroxyiron(III) or acylperoxyiron(III) intermediates formed during the presumed FeIII-FeV catalytic cycle and have generally been regarded as off-pathway. We generated complex 1IV═O (λmax = 730 nm, ε = 350 M-1 cm-1) directly from 1 and an oxygen atom donor IBXi-Pr (isopropyl 2-iodoxybenzoate) in acetonitrile in the temperature range from -35 to +25 °C under stopped-flow conditions. Species 1IV═O is metastable (half-life of 2.0 min at +25 °C), and its decay is accelerated in the presence of organic substrates such as thioanisole, alkenes, benzene, and cyclohexane. The reaction with cyclohexane-d12 is significantly slower (KIE = 4.9 ± 0.4), suggesting that a hydrogen atom transfer to 1IV═O is the rate limiting step. With benzene-d6, no significant isotope effect is observed (KIE = 1.0 ± 0.2), but UV-vis spectra show the concomitant formation of an intense 580 nm band likely due to the Fe(III)-phenolate chromophore, suggesting an electrophilic attack of 1IV═O on the aromatic system of benzene. Treatment of 1IV═O with H2O2 resulted in rapid decay of its 730 nm visible band (k = 102.6 ± 4.6 M-1 s-1 at -20 °C), most likely occurring by a hydrogen atom transfer from H2O2. In the presence of excess H2O2, the oxoiron(IV) is transformed into peroxyiron(III), as seen from the formation of a characteristic 550 nm visible band and geff = 2.22, 2.16, and 1.96 electron paramagnetic resonance (EPR) spectroscopy signals. Reductively formed 1III-OOH was able to re-enter the catalytic cycle of alkene epoxidation by H2O2, albeit with lower yields versus those of oxidatively formed (i.e., 1 + H2O2) peroxyiron(III) owing to a loss of ca. 40% active iron. As such, the oxoiron(IV) species can be reintroduced to the catalytic cycle with extra H2O2, acting as an iron reservoir. Alternatively, peroxycarboxylic acids, which have a stronger O-H bond dissociation energy, do not reduce 1IV═O, ensuring that more oxidant is productively employed in substrate oxidation. While this reaction with H2O2 may occur for other nonheme oxoiron(IV) complexes, the only previously reported examples are 3IV═O and 4IV═O, which are reduced by hydrogen peroxide 130- and 2900-fold more slowy, respectively (as in Angew. Chemie - Int. Ed. 2012 , 51 ( 22 ), 5376 - 5380 , DOI: 10.1002/anie.201200901 ).

Carbon Nanotubes and Graphene Promote Pyrolysis of Free-Base Phthalocyanine.

Unsubstituted phthalocyanines (including free-base H2Pc and many of its metal complexes) are among the most stable organic compounds. They can sublime without decomposition under reduced pressure and temperatures of up to 550 °C. This property was previously employed to design a novel approach to noncovalent functionalization of pristine single-walled carbon nanotubes (SWNTs) with 3d metal(II) phthalocyanine complexes. However, when we attempted to use the same sublimation protocol to prepare a SWNTs-H2Pc hybrid, an unexpected side effect of partial H2Pc pyrolysis was detected, phthalonitrile being a main decomposition product, under the conditions when H2Pc is supposed to be totally stable. By using density functional theory calculations, we offer an explanation for the thermal behavior of H2Pc based on its covalent attachment to the pentagonal-ring topological defects, which are very common in all graphene-derived carbon nanomaterials and capable of reacting with amines via nucleophilic addition process.

Ligand-Directed Reactivity in Dioxygen and Water Binding to cis-[Pd(NHC)2(η2-O2)].

Reaction of [Pd(IPr)2] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and O2 leads to the surprising discovery that at low temperature the initial reaction product is a highly labile peroxide complex cis-[Pd(IPr)2(η2-O2)]. At temperatures ≳ -40 °C, cis-[Pd(IPr)2(η2-O2)] adds a second O2 to form trans-[Pd(IPr)2(η1-O2)2]. Squid magnetometry and EPR studies yield data that are consistent with a singlet diradical ground state with a thermally accessible triplet state for this unique bis-superoxide complex. In addition to reaction with O2, cis-[Pd(IPr)2(η2-O2)] reacts at low temperature with H2O in methanol/ether solution to form trans-[Pd(IPr)2(OH)(OOH)]. The crystal structure of trans-[Pd(IPr)2(OOH)(OH)] is reported. Neither reaction with O2 nor reaction with H2O occurs under comparable conditions for cis-[Pd(IMes)2(η2-O2)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene). The increased reactivity of cis-[Pd(IPr)2(η2-O2)] is attributed to the enthalpy of binding of O2 to [Pd(IPr)2] (-14.5 ± 1.0 kcal/mol) that is approximately one-half that of [Pd(IMes)2] (-27.9 ± 1.5 kcal/mol). Computational studies identify the cause as interligand repulsion forcing a wider C-Pd-C angle and tilting of the NHC plane in cis-[Pd(IPr)2(η2-O2)]. Arene-arene interactions are more favorable and serve to further stabilize cis-[Pd(IMes)2(η2-O2)]. Inclusion of dispersion effects in DFT calculations leads to improved agreement between experimental and computational enthalpies of O2 binding. A complete reaction diagram is constructed for formation of trans-[Pd(IPr)2(η1-O2)2] and leads to the conclusion that kinetic factors inhibit formation of trans-[Pd(IMes)2(η1-O2)2] at the low temperatures at which it is thermodynamically favored. Failure to detect the predicted T-shaped intermediate trans-[Pd(NHC)2(η1-O2)] for either NHC = IMes or IPr is attributed to dynamic effects. A partial potential energy diagram for initial binding of O2 is constructed. A range of low-energy pathways at different angles of approach are present and blur the distinction between pure "side-on" or "end-on" trajectories for oxygen binding.

{1,1'-Bis[(pyridin-2-yl)meth-yl]-2,2'-bipiperid-yl}(perchlorato)copper(II) perchlorate.

The title complex, [CuII(ClO4)(mesoPYBP)](ClO4) {PYBP = 1,1'-bis-[(pyridin-2-yl)meth-yl]-2,2'-bipiperidyl, C22H30N4}, was prepared and found to crystallize with two crystallographically independent complex salt moieties. The metal atoms of the cations adopt a pseudo-square-pyramidal coordination geometry, where the tetra-dentate amino-pyridine ligands (PYBP) are wrapped around the Cu atoms in the equatorial plane. The Cu-O bonds involving an O atom of the coordinating perchlorate anion are approximately perpendicular to the plane. The two remaining non-coordinating perchlorate anions are involved in several C-H⋯O hydrogen bonds with the PYBP ligand and balance the total charge of the complex salt. The two crystallographically independent moieties are related to each other via a pseudo-translation along the a-axis direction. Exact translational symmetry is broken by (i) a difference in the conformation of one of the piperidine rings, featuring a chair conformation in one of the cations, and a sterically disfavored boat conformation in the other; and (ii) by modulation of the non-coordinating perchlorate anions.

Synthesis and crystal structure of [2,7,12-trimethyl-3,7,11,17-tetra-aza-bicyclo-[11.3.1]hepta-deca-1(17),13,15-triene-κ(4) N]copper(II) bis-(perchlorate).

The title copper(II) complex of a pyridine-containing macrocycle (PyMAC), [Cu(C16H28N4)](ClO4)2, has been prepared. The crystal structure reveals the Cu(II) atom to be octahedrally coordinated by a tetradentate aminopyridine macrocyclic ligand surrounding the metal cation in a square-planar geometry. Two weakly bound perchlorate counter-ions occupy the axial sites above and below the macrocyclic plane. The crystal studied was refined as a two-component pseudo-merohedral twin; the refined fractional contribution of the minor component is 38.77 (8).

Drug-Induced Liver Injury during Antidepressant Treatment: Results of AMSP, a Drug Surveillance Program.

BACKGROUND: Drug-induced liver injury is a common cause of liver damage and the most frequent reason for withdrawal of a drug in the United States. The symptoms of drug-induced liver damage are extremely diverse, with some patients remaining asymptomatic. METHODS: This observational study is based on data of Arzneimittelsicherheit in der Psychiatrie, a multicenter drug surveillance program in German-speaking countries (Austria, Germany, and Switzerland) recording severe drug reactions in psychiatric inpatients. Of 184234 psychiatric inpatients treated with antidepressants between 1993 and 2011 in 80 psychiatric hospitals, 149 cases of drug-induced liver injury (0.08%) were reported. RESULTS: The study revealed that incidence rates of drug-induced liver injury were highest during treatment with mianserine (0.36%), agomelatine (0.33%), and clomipramine (0.23%). The lowest probability of drug-induced liver injury occurred during treatment with selective serotonin reuptake inhibitors ([0.03%), especially escitalopram [0.01%], citalopram [0.02%], and fluoxetine [0.02%]). The most common clinical symptoms were nausea, fatigue, loss of appetite, and abdominal pain. In contrast to previous findings, the dosage at the timepoint when DILI occurred was higher in 7 of 9 substances than the median overall dosage. Regarding liver enzymes, duloxetine and clomipramine were associated with increased glutamat-pyruvat-transaminase and glutamat-oxalat-transaminase values, while mirtazapine hardly increased enzyme values. By contrast, duloxetine performed best in terms of gamma-glutamyl-transferase values, and trimipramine, clomipramine, and venlafaxine performed worst. CONCLUSIONS: Our findings suggest that selective serotonin reuptake inhibitors are less likely than the other antidepressants, examined in this study, to precipitate drug-induced liver injury, especially in patients with preknown liver dysfunction.

Utilizing heavy metal-laden water hyacinth biomass in vermicomposting.

We studied the efficiency of water treatment by water hyacinth (Eichhornia crassipes) from heavy metals (Zn, Cd, Pb, Cu), as well as a possibility of using water hyacinth biomass obtained during treatment for vermicomposting by Eisenia fetida and the vermicompost quality in a model experiment. The results showed that the concentration of heavy metals in the trials with water hyacinth decreased within 35 days. We introduced water hyacinth biomass to the organic substrate for vermicomposting, which promoted a significant weight gain of earthworms and growth in their number, as well as a 1.5- to 3-fold increase in coprolite production. In the trial with 40 % of Eichhornia biomass in the mixture, we observed a 26-fold increase in the number and a 16-fold weight gain of big mature individuals with clitellum; an increase in the number of small individuals 40 times and in the number of cocoons 140 times, as compared to the initial substrate. The utilization of water hyacinth biomass containing heavy metals in the mixture led to a 10-fold increase in the number of adult individuals and cocoons, which was higher than in control. We found out that adding 10 % of Eichhornia biomass to the initial mixture affected slightly the number of microorganisms and their species diversity in the vermicompost. Adding Eichhornia biomass with heavy metals reduced the total number of microorganisms and sharply diminished their species diversity. In all trials, adding water hyacinth in the mixture for vermicomposting had a positive impact on wheat biometric parameters in a 14-day laboratory experiment, even in the trial with heavy metals.

Role of axial base coordination in isonitrile binding and chalcogen atom transfer to vanadium(III) complexes.

The enthalpy of oxygen atom transfer (OAT) to V[(Me3SiNCH2CH2)3N], 1, forming OV[(Me3SiNCH2CH2)3N], 1-O, and the enthalpies of sulfur atom transfer (SAT) to 1 and V(N[t-Bu]Ar)3, 2 (Ar = 3,5-C6H3Me2), forming the corresponding sulfides SV[(Me3SiNCH2CH2)3N], 1-S, and SV(N[t-Bu]Ar)3, 2-S, have been measured by solution calorimetry in toluene solution using dbabhNO (dbabhNO = 7-nitroso-2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) and Ph3SbS as chalcogen atom transfer reagents. The V-O BDE in 1-O is 6.3 ± 3.2 kcal·mol(-1) lower than the previously reported value for 2-O and the V-S BDE in 1-S is 3.3 ± 3.1 kcal·mol(-1) lower than that in 2-S. These differences are attributed primarily to a weakening of the V-Naxial bond present in complexes of 1 upon oxidation. The rate of reaction of 1 with dbabhNO has been studied by low temperature stopped-flow kinetics. Rate constants for OAT are over 20 times greater than those reported for 2. Adamantyl isonitrile (AdNC) binds rapidly and quantitatively to both 1 and 2 forming high spin adducts of V(III). The enthalpies of ligand addition to 1 and 2 in toluene solution are -19.9 ± 0.6 and -17.1 ± 0.7 kcal·mol(-1), respectively. The more exothermic ligand addition to 1 as compared to 2 is opposite to what was observed for OAT and SAT. This is attributed to less weakening of the V-Naxial bond in ligand binding as opposed to chalcogen atom transfer and is in keeping with structural data and computations. The structures of 1, 1-O, 1-S, 1-CNAd, and 2-CNAd have been determined by X-ray crystallography and are reported.

Electron-transfer studies of a peroxide dianion.

A peroxide dianion (O2(2-)) can be isolated within the cavity of hexacarboxamide cryptand, [(O2)⊂mBDCA-5t-H6](2-), stabilized by hydrogen bonding but otherwise free of proton or metal-ion association. This feature has allowed the electron-transfer (ET) kinetics of isolated peroxide to be examined chemically and electrochemically. The ET of [(O2)⊂mBDCA-5t-H6](2-) with a series of seven quinones, with reduction potentials spanning 1 V, has been examined by stopped-flow spectroscopy. The kinetics of the homogeneous ET reaction has been correlated to heterogeneous ET kinetics as measured electrochemically to provide a unified description of ET between the Butler-Volmer and Marcus models. The chemical and electrochemical oxidation kinetics together indicate that the oxidative ET of O2(2-) occurs by an outer-sphere mechanism that exhibits significant nonadiabatic character, suggesting that the highest occupied molecular orbital of O2(2-) within the cryptand is sterically shielded from the oxidizing species. An understanding of the ET chemistry of a free peroxide dianion will be useful in studies of metal-air batteries and the use of [(O2)⊂mBDCA-5t-H6](2-) as a chemical reagent.

Pycup--a bifunctional, cage-like ligand for (64)Cu radiolabeling.

In developing targeted probes for positron emission tomography (PET) based on (64)Cu, stable complexation of the radiometal is key, and a flexible handle for bioconjugation is highly advantageous. Here, we present the synthesis and characterization of the chelator pycup and four derivatives. Pycup is a cross-bridged cyclam derivative with a pyridyl donor atom integrated into the cross-bridge resulting in a pentadentate ligand. The pycup platform provides kinetic inertness toward (64)Cu dechelation and offers versatile bioconjugation chemistry. We varied the number and type of additional donor atoms by alkylation of the remaining two secondary amines, providing three model ligands, pycup2A, pycup1A1Bn, and pycup2Bn, in 3-4 synthetic steps from cyclam. All model copper complexes displayed very slow decomplexation in 5 M HCl and 90 °C (t1/2: 1.5 h for pycup1A1Bn, 2.7 h for pycup2A, 20.3 h for pycup2Bn). The single crystal crystal X-ray structure of the [Cu(pycup2Bn)](2+) complex showed that the copper was coordinated in a trigonal, bipyramidal manner. The corresponding radiochemical complexes were at least 94% stable in rat plasma after 24 h. Biodistribution studies conducted in Balb/c mice at 2 h postinjection of (64)Cu labeled pycup2A revealed low residual activity in kidney, liver, and blood pool with predominantly renal clearance observed. Pycup2A was readily conjugated to a fibrin-targeted peptide and labeled with (64)Cu for successful PET imaging of arterial thrombosis in a rat model, demonstrating the utility of our new chelator in vivo.

H2O2 activation with biomimetic non-haem iron complexes and AcOH: connecting the g = 2.7 EPR signal with a visible chromophore.

Mechanistic studies of H2O2 activation by complexes related to [(BPMEN)Fe(II)(CH3CN)2](2+) with electron-rich pyridines revealed that a new intermediate formed in the presence of acetic acid with a 465 nm visible band can be associated with an unusual g = 2.7 EPR signal. We postulate that this chromophore is an acylperoxoiron(III) intermediate.

Family history of major depression and residual symptoms in responder and non-responder depressed patients.

BACKGROUND: Little is known about the extent to which a family history of major depression (MD) affects residual depressive symptoms in responder and non-responder patients suffering from MD. METHODS: Nine hundred eighty-six patients with MD were recruited within the context of a large multicenter project. Information about the family history of MD, as well as about total depressive symptoms and specific depressive clusters, was collected and analyzed. RESULTS: No significant difference was observed in overall depressive symptoms between patients with and those without a family history of MD. However, non-responder patients with a family history of MD showed significantly higher scores in core symptoms as compared with responder patients without a family history of MD. CONCLUSIONS: Non-responder MD patients with a positive family history of MD could represent a slightly different sub-group of MD patients with more consistent core depressive symptoms as compared with responder patients without a family history of MD. However, taking into account the retrospective assessment of data, the use of positive or negative family history as a dichotomous indicator of familial loading and the cross-sectional design of the present study, further research is needed to draw more definitive conclusions.

Rationalization of the barrier height for p-Z-styrene epoxidation by iron(IV)-oxo porphyrin cation radicals with variable axial ligands.

A versatile class of heme monoxygenases involved in many vital functions for human health are the cytochromes P450, which react via a high-valent iron(IV) oxo heme cation radical species called Compound I. One of the key reactions catalyzed by these enzymes is C═C epoxidation of substrates. We report here a systematic study into the intrinsic chemical properties of substrate and oxidant that affect reactivity patterns. To this end, we investigated the effect of styrene and para-substituted styrene epoxidation by Compound I models with either an anionic (chloride) or neutral (acetonitrile) axial ligand. We show, for the first time, that the activation enthalpy of the reaction is determined by the ionization potential of the substrate, the electron affinity of the oxidant, and the strength of the newly formed C-O bond (approximated by the bond dissociation energy, BDE(OH)). We have set up a new valence bond model that enables us to generalize substrate epoxidation reactions by iron(IV)-oxo porphyrin cation-radical oxidants and make predictions of rate constants and reactivities. We show here that electron-withdrawing substituents lead to early transition states, whereas electron-donating groups on the olefin substrate give late transition states. This affects the barrier heights in such a way that electron-withdrawing substituents correlate the barrier height with BDE(OH), while the electron affinity of the oxidant is proportional to the barrier height for substrates with electron-donating substituents.

Social adjustment among treatment responder patients with mood disorders.

BACKGROUND: Patients with major depression (MD) show reduced social adjustment when compared with healthy controls. However, even among treatment responders, significant differences in social adjustment occur. The main aim of the present work is to study several socio-demographic and clinical variables possibly influencing social adjustment in MD patients who responded to treatment. METHODS: Two hundred and eleven MD patients experiencing a depressive episode who responded to their current treatment were recruited within the context of a large European multicentre project. Our primary outcome measure was the association between 19 socio-demographic and clinical variables and total social adjustment scores, as measured with the Social Adjustment Scale (SAS). Secondary outcome measures included the associations between the same variables and SAS sub-scales, and the associations between these variables and self-esteem, as measured with the Rosenberg Self-Esteem Scale. RESULTS: A co-morbidity with anxiety disorders and the severity of residual depression symptoms were the strongest independent factors associated with poorer social adjustment, in terms of total and most sub-areas' SAS scores. Other variables associated with total and sub-areas' SAS scores were identified as well, although some variations across different areas were observed. LIMITATIONS: The cross-sectional design, the retrospective assessment of data and the lack of a placebo control group. CONCLUSIONS: Our results confirm that a co-morbidity with anxiety disorders and higher residual depression symptoms could reduce social adjustment among responder MD patients. Further longitudinal studies are needed to confirm our results.

Thermodynamic and kinetic study of cleavage of the N-O bond of N-oxides by a vanadium(III) complex: enhanced oxygen atom transfer reaction rates for adducts of nitrous oxide and mesityl nitrile oxide.

Thermodynamic, kinetic, and computational studies are reported for oxygen atom transfer (OAT) to the complex V(N[t-Bu]Ar)3 (Ar = 3,5-C6H3Me2, 1) from compounds containing N-O bonds with a range of BDEs spanning nearly 100 kcal mol(-1): PhNO (108) > SIPr/MesCNO (75) > PyO (63) > IPr/N2O (62) > MesCNO (53) > N2O (40) > dbabhNO (10) (Mes = mesityl; SIPr = 1,3-bis(diisopropyl)phenylimidazolin-2-ylidene; Py = pyridine; IPr = 1,3-bis(diisopropyl)phenylimidazol-2-ylidene; dbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene). Stopped flow kinetic studies of the OAT reactions show a range of kinetic behavior influenced by both the mode and strength of coordination of the O donor and its ease of atom transfer. Four categories of kinetic behavior are observed depending upon the magnitudes of the rate constants involved: (I) dinuclear OAT following an overall third order rate law (N2O); (II) formation of stable oxidant-bound complexes followed by OAT in a separate step (PyO and PhNO); (III) transient formation and decay of metastable oxidant-bound intermediates on the same time scale as OAT (SIPr/MesCNO and IPr/N2O); (IV) steady-state kinetics in which no detectable intermediates are observed (dbabhNO and MesCNO). Thermochemical studies of OAT to 1 show that the V-O bond in O≡V(N[t-Bu]Ar)3 is strong (BDE = 154 ± 3 kcal mol(-1)) compared with all the N-O bonds cleaved. In contrast, measurement of the N-O bond in dbabhNO show it to be especially weak (BDE = 10 ± 3 kcal mol(-1)) and that dissociation of dbabhNO to anthracene, N2, and a (3)O atom is thermodynamically favorable at room temperature. Comparison of the OAT of adducts of N2O and MesCNO to the bulky complex 1 show a faster rate than in the case of free N2O or MesCNO despite increased steric hindrance of the adducts.