Highly stable preferential carbon monoxide oxidation by dinuclear heterogeneous catalysts.

Atomically dispersed catalysts have been shown highly active for preferential oxidation of carbon monoxide in the presence of excess hydrogen (PROX). However, their stability has been less than ideal. We show here that the introduction of a structural component to minimize diffusion of the active metal center can greatly improve the stability without compromising the activity. Using an Ir dinuclear heterogeneous catalyst (DHC) as a study platform, we identify two types of oxygen species, interfacial and bridge, that work in concert to enable both activity and stability. The work sheds important light on the synergistic effect between the active metal center and the supporting substrate and may find broad applications for the use of atomically dispersed catalysts.

Children's empathy moderates the association between perceived interparental conflict and child health.

Interparental conflict is known to negatively impact child well-being, including behavioral and physiological well-being. Children's empathy - that is, vicariously experiencing others' emotions - may increase children's sensitivity to and the biological repercussions of interparental conflict. Although empathy represents a valued trait and is an important part of socioemotional development, its influence on children's physical health is unknown. This study examined whether empathy moderates the association between perceived interparental conflict and both child systemic inflammation and parent-rated overall child health in a sample of children between the ages of seven to nine. Children and their parents participating in the long-term evaluation of the Family Foundations program, a randomized trial of a perinatal preventative intervention, provided data approximately eight years following enrollment into the program. We collected peripheral blood samples via dried blood spots, anthropometric measurements, and child and parent psychosocial questionnaires. Results indicated significant positive main effects of child empathy on both C-reactive protein (CRP; B = 0.26, SE = 0.11, p =.026) and Interleukin-6 (IL-6; B = 0.20, SE = 0.10, p =.045) levels. Further, child affective empathy moderated the associations between perceived interparental conflict and both CRP (B = 0.39, SE = 0.19, p =.050) and parent-reported child health (B = 0.30, SE = 0.13, p =.021), such that greater empathy strengthened the negative associations between interparental conflict and child health. Overall, findings suggests that there may be a biological cost of being more empathic in high-conflict environments and highlight the need for tools to help more empathic children appropriately manage vicarious emotions.

Milk production of cows grazing pasture supplemented with grain mixes containing canola meal or corn grain or both over the first 100 days of lactation.

Grain mixes varying in proportions of wheat grain, barley grain, canola meal, and corn grain were fed to grazing dairy cows in early lactation to determine the contribution of canola meal and corn grain to milk yield, BW, BCS, eating behavior, and blood serum metabolite concentrations. The experiment used 80 multiparous, seasonally calving Holstein-Friesian dairy cows during the first 100 d of lactation, the treatment period, and over the subsequent carryover period of 100 d, during which all cows were fed a common diet. Cows were divided into 4 cohorts (blocks) based on calving date and within each cohort, 5 cows were randomly allocated to each of the 4 treatments. Dietary treatments included disc-milled grain mixes comprising (on a DM basis) (1) a control treatment of wheat (25%) and barley (75%); (2) wheat (25%), barley (50%), and canola meal (25%); (3) wheat (25%), barley (50%), and corn (25%), and (4) wheat (25%), barley (25%), canola meal (25%), and corn (25%). Treatment diets were introduced at 19 DIM ± 4.7 d, which included a 7-d adaptation period and were applied up until 100 DIM. Each grain mix was fed at 9 kg of DM/cow per day, offered twice daily, in equal proportions in the parlor at milking times. In addition to the grain mix, all cows grazed perennial ryegrass pasture at a daily allowance of ∼35 kg of DM/cow per day (measured to ground level). Results were analyzed in terms of corn and canola presence or absence in the diet. Including canola meal in grain mixes increased grain intake and pasture intake by 0.6 and 2.1 kg of DM/cow per day, respectively, resulting in an increased milk yield of 2.6 kg/cow per day during the first 100 d of lactation. Including canola meal also increased yields of milk fat and protein, and concentrations of milk fat, as well as increasing mean BW and BCS over the 100 d. The inclusion of canola meal in the grain mixes also resulted in greater blood serum BHB and urea concentrations, compared with feeding grain mixes that did not contain canola meal. The inclusion of corn grain provided no milk production benefits and did not change BW, BCS, or any feeding behavior variables. There were no carryover effects on milk production from either canola meal or corn grain after the treatment period. In summary, the results demonstrate that the provision of canola meal in grain mixes can improve milk production and increase mean BCS. Further, there are no benefits to milk yield when a proportion of barley is substituted for corn, in a wheat and barley grain mix fed to grazing dairy cows in early lactation. However, these results are dependent on the level of inclusion and the feeding system employed.

Mean affect and affect variability may interact to predict inflammation.

INTRODUCTION: Individuals with greater affect variability (i.e., moment-to-moment fluctuations possibly reflecting emotional dysregulation) are at risk for greater systemic inflammation, which is associated with cardiovascular disease. Some evidence suggests that affect variability is linked with poorer health indicators only among those with higher average levels of affect, particularly for positive affect (PA), and that associations may be non-linear. The present study sought to examine whether links between both PA and negative affect (NA) variability and inflammation are moderated by average level of affect. METHODS: Participants (N = 300, 50 % female, ages 21-70, 60 % non-Hispanic White, 19 % Hispanic, 15 % non-Hispanic Black) completed a lab assessment and provided a blood sample to measure systemic inflammation (i.e., TNF-α, IL-6, CRP). Affect was collected via a two-day ecological momentary assessment protocol where reports were collected about every 45-min during waking hours. Momentary affect ratings were averaged across both days (i.e., iM), separately for PA and NA, for each participant. Affect variability was calculated as the person-specific SD (i.e., iSD) of affect reports, separately for PA and NA. Linear and quadratic interactions were tested. Models included covariates for sex, race, and body mass index. RESULTS: There were significant interactions between NA iM and NA iSD predicting TNF-α (b = 6.54; p < 0.05) and between PA iM and PA iSD predicting IL-6 (b = 0.45; p < 0.05). Specifically, the association between these affect variability indicators and inflammatory markers were suggestive of a positive association among those with higher average affect but a negative association among those with lower average affect. There was no evidence of non-linear associations between affect and inflammation. DISCUSSION: Incorporating interactive effects between affect variability and average affect may be an important consideration in understanding affective-inflammatory associations.

First-generation College Students Have Greater Systemic Inflammation than Continuing-Generation College Students Following the Initial College Transition: A Brief Report.

BACKGROUND: First-generation college students ("first-gens") are often at a disadvantage socially and academically; whether they are at risk physiologically is unknown despite the well-established link between greater education and better long-term health. PURPOSE: To examine whether first-gens have higher levels of cardiovascular disease (CVD) risk markers relative to continuing-generation college students ("continuing-gens"). METHODS: A panel of CVD risk markers was assessed among 87 emerging adults (41 first-gens) twice over their first year of college. RESULTS: Compared to continuing-gens, first-gens had greater systemic inflammation (composite of averaged z-scores for C-reactive protein and interleukin-6; B = 0.515, SE = 0.171, p = .003) during the fall but not spring semester (p > .05). Associations were independent of family home ownership and childhood adversity, even though first-gens were more likely to live in rental homes and reported riskier home environments. Lower childhood subjective social status (SSS) accounted for greater systemic inflammation among first-gens as evidenced by an indirect effect of college generation status on systemic inflammation through childhood SSS (a1b1 = 0.261, bootstrapped SE = 0.103, 95% boot CI [0.078, 0.482]). There were no differences in metabolic risk and latent virus regulation by college generation status in either semester (p > .10). CONCLUSIONS: This is the first study to find that first-gens have higher levels of systemic inflammation than continuing-gens following the college transition and that childhood SSS may be one explanatory pathway. First-gens may benefit from university resources that address social class differences, which should be provided early on so that first-gens can reap the health-relevant benefits of higher education, at least in the short term.

Effect of forage type on swallowed bolus mass and a method for counting swallows in dairy cattle.

Dry matter intake (DMI) is a primary determinant of milk production in grazing dairy cows and an ability to measure the DMI of individual cows would allow herd managers to formulate supplementary rations that consider the amount of nutrients ingested from grass. The 2 related aims of this experiment were to define the mean number of swallowed boli and mass of the swallowed boli in Holstein-Friesian dairy cattle offered a variety of forages commonly fed in the dairy industry of southeastern Australia, and to evaluate 2 indirect methods for counting the number of swallows. Twelve ruminally-fistulated, lactating Holstein-Friesian cows were randomly assigned to 3 replicated 4 × 4 Latin square designs and offered 4 forages: fresh chicory (FC), fresh perennial ryegrass (RP), alfalfa hay (AH), and perennial ryegrass silage (RS). The experiment was conducted over 28 d with each of 4 periods consisting of 7 d with 3 d of measurement. Forage diets were offered to individual cows following the partial evacuation of the rumen. The first 20 min after forage was offered constituted the measurement period, during which all swallowed boli were manually captured by samplers who placed their hand through the ruminal fistula and over the cardia entrance of the rumen of each cow. Concurrently, microphones and video cameras were used for the indirect measurement of swallows. The average swallowed bolus mass overall was 17.4 g dry matter (DM) per bolus with the lowest mass observed in cows offered FC (8.9 g DM/bolus), followed by RP (14.9 g DM/bolus), compared with cows offered AH (23.6 g DM/bolus) and RS (22.3 g DM/bolus). The swallowing rate was greater in cows offered FC (78 swallows/20 min) than in cows offered RP, AH, and RS (62.3 swallows/20 min). The audio recording method showed greater concordance (Lin's concordance correlation coefficient = 0.90) with the physical capturing of the boli through the rumen, than the video recording method did (Lin's concordance correlation coefficient = 0.54). It is concluded that the mass of the swallowed boli is related to forage type and that using a microphone attached to the cow's forehead can provide an accurate measure of the number of swallows when verified against the actual number of swallows counted by manual interception of the boli at the rumen cardia.

Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex.

Electrocatalytic ammonia oxidation at room temperature and pressure allows energy-economical and environmentally friendly production of nitrites and nitrates. Few molecular catalysts, however, have been developed for this six- or eight-electron oxidation process. We now report [Cu(bipyalk)]+, a homogeneous electrocatalyst that realizes the title reaction in water at 94% Faradaic efficiency. The catalyst exhibits high selectivity against water oxidation in aqueous media, as [Cu(bipyalk)]+ is not competent for water oxidation.

Assembling a cohort for in-depth, longitudinal assessments of the biological embedding of child maltreatment: Methods, complexities, and lessons learned.

As championed by the work of Ed Zigler, investing in nurturing environments for all children is a chief tenet of primary prevention that will have far-reaching benefits to the health and welfare of all members of society. Children who endure child maltreatment (CM) are among society's most vulnerable. Prospective longitudinal research aimed at a comprehensive understanding of the mechanisms linking CM to subsequent adverse health consequences is needed to improve outcomes and to strengthen causal inference. This paper outlines the methods of the Child Health Study (CHS), a large, state-wide longitudinal cohort of recently maltreated and nonmaltreated youth aged 8-13 who will be assessed every 2 years. The CHS is designed to include in-depth assessments of multiple environmental, behavioral, neural, physiological, and molecular mechanisms through which CM may impact a broad spectrum of youth development, including behavioral and physical health outcomes. In addition to describing the conceptual framework and methods underlying the CHS, we provide information on valuable "lessons learned" in the hopes of supporting future research efforts facing similar challenges. The ultimate goal of this research is demonstrating how policies regarding CM impact the well-being, resilience and recovery of survivors and that they are worthy of large public investment.

Using estimated nutrient intake from pasture to formulate supplementary concentrate mixes for grazing dairy cows.

In pasture-based dairy systems, feeding a complex concentrate mix in the parlor during milking that contains cereal grains and protein supplements has been shown to have milk production advantages over feeding straight cereal grain. This experiment had the aim of testing whether further milk production advantages could be elicited by adjusting the composition of the concentrate mix in an attempt to match the expected nutrient intake from pasture during late spring. The experiment used 96 lactating dairy cows, grazing perennial ryegrass pasture offered at a target allowance of 30 kg of dry matter/cow per day (to ground level) during late spring (mid October to November) in southeastern Australia. Cows were allocated into 3 replicates of 4 treatment groups, with 24 cows in each treatment. Each treatment group was offered 1 of 4 dietary treatments in the parlor at milking: control consisting of crushed wheat and barley grains; formulated grain mix (FGM) consisting of crushed wheat, barley, and corn grains and canola meal; designer grain mix 1 (DGM1) consisting of the same ingredients as the FGM grain mix but formulated using the CPM Dairy nutrition model to take into account the expected nutrient intake from pasture; and designer grain mix 2 (DGM2) consisting of the same ingredients as DGM1 but with canola meal replaced by urea and a fat supplement (Megalac, Volac Wilmar, Gresik, Indonesia). Concentrate mixes were offered at 8.0 kg of dry matter/cow per day, except for DGM2 cows, which were offered 7.5 kg of dry matter/cow per day. The experiment ran for a total of 28 d; after a 14-d adaptation period, nutrient intake, milk production, and body weight were measured over a 14-d measurement period. Milk yield (kg) of cows fed the FGM diet was greater than that of the control cows but was not different from that of the DGM1 and DGM2 cows. However, milk fat and protein yields (kg) were greater for cows fed the FGM diet than for all other diets. There was no difference in estimated daily pasture or total dry matter intakes between the 4 treatment groups, despite cows fed the DGM2 treatment consuming less of the concentrate mix (average 6.5 kg of dry matter/cow per day when offered 7.5 kg of dry matter/cow per day). This research has demonstrated the potential for using a nutrition model to take into account the expected nutrient intake from pasture to formulate a concentrate mix (DGM1) to achieve similar milk yields, but also highlighted the need for near real-time analyses of the pasture to be grazed so as to also capture benefits in terms of milk fat and protein yield.

Neuroendocrine coordination and youth behavior problems: A review of studies assessing sympathetic nervous system and hypothalamic-pituitary adrenal axis activity using salivary alpha amylase and salivary cortisol.

Externalizing and internalizing behavior problems can have deleterious psychosocial consequences for youth. Both sympathetic nervous system (SNS) and hypothalamic-pituitary adrenal (HPA) axis activity and reactivity may contribute to behavior problems but have largely been studied separately, with inconsistent findings. Because the SNS and HPA axis interact to carry out physiological processes (e.g., responding to stressors), considering SNS and HPA axis activity jointly may elucidate disparate findings. This review discusses studies that simultaneously assessed SNS and HPA axis (re)activity and youth behavior problems using measures of salivary alpha amylase (sAA) and salivary cortisol. Multiple patterns of SNS and HPA axis coordination were associated with problem behaviors, especially when considering individual differences and youth's psychosocial context. Importantly, many study findings may be artifacts of widespread methodological differences. The reviewed studies lay the foundation for future research on neuroendocrine coordination as a contributing factor to youth problem behaviors and some recommendations for future research are discussed.

Influence of proportion of wheat in a pasture-based diet on milk yield, methane emissions, methane yield, and ruminal protozoa of dairy cows.

Wheat is the most common concentrate fed to grazing dairy cows in Australia, but no studies have examined the effects of wheat proportion in a pasture-based diet on milk production and methane emissions. In this 47-d experiment, 32 Holstein dairy cows were offered 1 of 4 diets during d 1 to 36. Cows in each of the dietary treatment groups were individually offered no wheat (W0) or wheat at 3 kg of dry matter (DM)/d (W3), 6 kg of DM/d (W6), or 9 kg of DM/d (W9). The remainder of the diet was 2.2 kg of DM of concentrate mix and freshly harvested perennial ryegrass (Lolium perenne) such that all individual cows were offered a total diet of approximately 20.2 kg of DM/d. From d 37 to 47 the diets of cows receiving treatments W0 and W3 remained unchanged, but cows in treatments W6 and W9 received the W3 diet. Individual cow feed intakes, milk yields, milk compositions, and methane emissions were measured for d 31 to 35 (period 1) and d 45 to 47 (period 2). During period 1, the mean intakes of cows offered the W0, W3, W6, and W9 diets were 19.2, 20.4, 20.2, and 19.8 kg of DM/d. Diet caused differences in energy-corrected milk, and means for W0, W3, W6, and W9 were 29.5, 32.4, 33.0, and 32.9 kg/d, respectively. Milk fat percentage differed with respective means of 3.93, 3.94, 3.69, and 3.17. Diets also caused differences in methane emissions, with means for W0, W3, W6, and W9 of 440, 431, 414, and 319 g/d. During period 1, the cows fed the W9 diet produced less methane and had lower methane yields (g/kg of DMI) and intensities (g/kg of energy-corrected milk) than cows fed the W3 diet. However, in period 2 when the wheat intake of cows in the W9 treatment was reduced to the same level as in the W3 treatment, their methane emissions, yields, and intensities were similar to those offered the W3 treatment, yet protozoa numbers in ruminal fluid were still much lower than those in cows offered the W3 treatment. Our research shows that for diets based on perennial ryegrass and crushed wheat, only the diet containing more than 30% crushed wheat resulted in substantially depressed milk fat concentration and reduced methane emissions, methane yield, and methane intensity. Thus, although feeding a diet with a high proportion of wheat can cause substantial methane mitigation, it can come at the cost of depression in milk fat concentration.

Prospective Relations Between Prenatal Maternal Cortisol and Child Health Outcomes.

OBJECTIVE: The aim of the study was to investigate prospective, longitudinal associations between maternal prenatal cortisol response to an interpersonal stressor and child health for the subsequent 3 years. METHODS: One hundred twenty-three women expecting their first child provided salivary cortisol samples between 12 and 32 weeks of gestation (M (SD) = 22.4 (4.9) weeks) before and after a videotaped couple conflict discussion with their partner. Mothers reported on overall child health and several indicators of child illness (sick doctor visits, fevers, ear, and respiratory infections) when children were 6 months (n = 114), 1 (n = 116), and 3 (n = 105) years old. Associations between maternal prenatal cortisol reactivity and recovery and later child health at each of the three time points were analyzed using longitudinal regression models. RESULTS: Greater cortisol reactivity in response to the couple conflict discussion was associated with maternal self-report of better overall child health (p = .016, 95% CI = 0.06-1.30, Cohen's f = 0.045) across the study period. Greater cortisol reactivity was also associated with lower incidence rate ratios for maternal reports of sick doctor visits (incidence rate ratio 95% CI = 0.25-0.83, p = .006), fevers (95% CI = 0.25-0.73, p = .002), ear infections (95% CI = 0.25-0.58, p < .001), and respiratory infections (95% CI = 0.08-1.11, p = .073). Cortisol recovery was unrelated to study outcomes (all p's > 0.05). Maternal prenatal depressive symptoms moderated the association between cortisol reactivity and overall child health (p = .034, 95% CI = 0.07-1.87 for interaction term) but no other health outcomes (p's > 0.05). Among women with lower depressive symptoms, cortisol reactivity was not associated with overall child health; among women with higher levels of depressive symptoms, greater cortisol reactivity was associated with better overall child health. CONCLUSIONS: This study provides longitudinal evidence that greater maternal cortisol reactivity to a salient interpersonal stressor during pregnancy is associated with fewer child health problems and better maternal report of overall child health during infancy and into early childhood. TRIAL REGISTRATION: Clinicaltrials.gov ID NCT01901536.

Chemical Oxidation of a Coordinated PNP-Pincer Ligand Forms Unexpected Re-Nitroxide Complexes with Reversal of Nitride Reactivity.

Because of the thermodynamic demands of N2 cleavage, N2-derived nitride complexes are often unreactive. The development of multistep N2 functionalization reactions hinges on methods for modulating nitride reactivity with supporting ligands. Here, we describe the reactions of N2-derived Re-nitride complexes, including the first Re nitrides supported by a nitroxide-containing pincer ligand, and unusual examples of Re6+-nitride complexes. The previously reported N2-derived complex (PNP)Re(N)(Cl) (PNP = N(CH2CH2PtBu2)2) can be oxidized by O atom transfer to the backbone amide to form a novel nitroxide-pincer complex or by 1e- to form a rare S = 1/2 Re6+-nitride complex. The Re-nitrido interaction in a series of Re- and ligand-oxidized complexes is characterized using 15N NMR spectroscopy, IR spectroscopy, and DFT calculations, and shows changes in the Re-N bond order from both ligand- and metal-centered oxidations. Chemical oxidation of the supporting ligand to form a nitroxide-pincer ligand results in subtle electronic changes at Re and a more electron-deficient nitride ligand. Combined ligand- and metal-centered oxidation to form a Re6+-nitroxide complex results in a reversal of reactivity at the nitride ligand from nucleophilic to electrophilic. These systematic electronic structure and reactivity studies demonstrate methods for inducing reactivity in N2-derived nitride complexes.

Aspects of the parent-child relationship and parent metabolic outcomes.

Much is known about the effect of parent-child relationships on child health; less is known about how parent-child relationships influence parent health. To assess the association between aspects of the parent-child relationship and parent metabolic outcomes, and whether these associations are moderated by parent gender. Five metabolic outcomes (systolic and diastolic blood pressure, heart rate, total cholesterol and glycated hemoglobin) were assessed among 261 parents (45.83 ± 5.50 years) of an adolescent child (14.57 ± 1.072 years). Parents completed questionnaires assessing their child's hassles and the quality of their days with their child. Parents' perceptions of their child's hassles were associated with parent heart rate (B = 2.954, SE = 1.267, p = 0.021) and cholesterol (B = 0.028, SE = 0.011, p = 0.010), such that greater perceived child hassles were associated with higher heart rate and cholesterol levels, on average. These associations were not moderated by parent gender (all ps > 0.30). Parent report of their day with their child was not associated with parent metabolic outcomes (all ps > 0.20). Parent gender moderated the association between parent report of their day with their child and parent systolic blood pressure (B = 13.861, SE = 6.200, p = 0.026), such that less positive reports were associated with higher blood pressure readings among fathers, but not mothers. This study suggests that parent metabolic health may in part be influenced by aspects of the parent-child relationship.

Effect of dietary fat supplementation on methane emissions from dairy cows fed wheat or corn.

Diets that contain high proportions of either wheat or supplementary fat have been individually reported to reduce enteric methane production. The objective of this research was to determine the effect of dietary fat supplementation on methane emissions and milk yield from cows fed diets containing either corn or wheat grains. It was hypothesized that cows fed a diet containing wheat would produce less methane and have lower methane yield (methane per kg of dry matter intake; MY) than cows fed a diet containing corn and that methane mitigation from fat supplementation would occur irrespective of the type of grain in the basal diet. The experiment involved 32 Holstein-Friesian dairy cows allocated to 1 of 4 treatment groups (n = 8) and individually fed different diets restricted to approximately 90% of their mean ad libitum intake measured during a covariate period. All animals were offered 11.5 kg of dry matter/d of alfalfa hay, 1.8 kg of dry matter/d of solvent-extracted canola meal, and 1 of 4 dietary supplements. Dietary supplements were 8 kg of dry matter/d of either corn or wheat, or these same treatments with the addition of 0.8 kg of canola oil. In this 5-wk experiment, d 1 to 7 served as the covariate period, d 8 to 14 as the transition period, d 15 to 28 as the adaptation period, and d 29 to 35 as the experimental period. Cows were fed their full treatment diets from d 15 to 35 during which time milk production and feed intake were measured daily. During d 29 to 35, methane production was measured for individual cows daily using the sulfur hexafluoride tracer method. The resulting averages for milk production and feed intake were analyzed by analysis of covariance with factorial grain by fat as treatment structure, animal as the unit within blocks, and the corresponding milk production or feed intake covariate averages as principal covariate. Data on milk fatty acids, ruminal fluid data on pH, ammonia, volatile fatty acids, protozoa, and methane were analyzed by ANOVA using the same treatment and blocking structures excluding the principal covariate. Cows fed a diet containing wheat had greater MY than cows fed a diet containing corn. Irrespective of the type of grain in the diet, increasing the fat concentration from 2 to 6% dry matter reduced MY. It is concluded that the grain component in the basal diet does not affect the mitigating effects of dietary fat supplements on MY.

Is Sexual Abuse a Unique Predictor of Sexual Risk Behaviors, Pregnancy, and Motherhood in Adolescence?

This study tested sexual abuse as a unique predictor of subsequent adolescent sexual behaviors, pregnancy, and motherhood when in company with other types of maltreatment (physical abuse, neglect) and alternative behavioral, family, and contextual risk factors in a prospective, longitudinal study of maltreated (n = 275) and comparison (n = 239) nulliparous females aged 14-19 years old assessed annually through 19 years old. Hierarchical regression was used to disentangle risk factors that account for the associations of maltreatment type on risky sexual behaviors at 19 years old, adolescent pregnancy, and adolescent motherhood. Findings indicate that sexual and physical abuse remain significant predictors of risky sexual behaviors, and that sexual abuse remains a significant predictor of adolescent motherhood when alternative explanatory variables are controlled.

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2 )-C(sp3 )Coupling Reactions.

A number of new transition metal catalyzed methods for the formation of C(sp2 )-C(sp3 ) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2 )-C(sp3 ) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2 )-C(sp3 ) coupling through stoichiometric studies and also explore their catalytic activity.

A Pyridine Alkoxide Chelate Ligand That Promotes Both Unusually High Oxidation States and Water-Oxidation Catalysis.

Water-oxidation catalysis is a critical bottleneck in the direct generation of solar fuels by artificial photosynthesis. Catalytic oxidation of difficult substrates such as water requires harsh conditions, so the ligand must be designed both to stabilize high oxidation states of the metal center and to strenuously resist ligand degradation. Typical ligand choices either lack sufficient electron donor power or fail to stand up to the oxidizing conditions. Our research on Ir-based water-oxidation catalysts (WOCs) has led us to identify a ligand, 2-(2'-pyridyl)-2-propanoate or "pyalk", that fulfills these requirements. Work with a family of Cp*Ir(chelate)Cl complexes had indicated that the pyalk-containing precursor gave the most robust WOC, which was still molecular in nature but lost the Cp* fragment by oxidative degradation. In trying to characterize the resulting active "blue solution" WOC, we were able to identify a diiridium(IV)-mono-µ-oxo core but were stymied by the extensive geometrical isomerism and coordinative variability. By moving to a family of monomeric complexes [IrIII/IV(pyalk)3] and [IrIII/IV(pyalk)2Cl2], we were able to better understand the original WOC and identify the special properties of the ligand. In this Account, we cover some results using the pyalk ligand and indicate the main features that make it particularly suitable as a ligand for oxidation catalysis. The alkoxide group of pyalk allows for proton-coupled electron transfer (PCET) and its strong σ- and π-donor power strongly favors attainment of exceptionally high oxidation states. The aromatic pyridine ring with its methyl-protected benzylic position provides strong binding and degradation resistance during catalytic turnover. Furthermore, the ligand has two additional benefits: broad solubility in aqueous and nonaqueous solvents and an anisotropic ligand field that enhances the geometry-dependent redox properties of its complexes. After discussion of the general properties, we highlight the specific complexes studied in more detail. In the iridium work, the isolated mononuclear complexes showed easily accessible Ir(III/IV) redox couples, in some cases with the Ir(IV) state being indefinitely stable in water. We were able to rationalize the unusual geometry-dependent redox properties of the various isomers on the basis of ligand-field effects. Even more striking was the isolation and full characterization of a stable Rh(IV) state, for which prior examples were very reactive and poorly characterized. Importantly, we were able to convert monomeric Ir complexes to [Cl(pyalk)2IrIV-O-IrIVCl(pyalk)2] derivatives that help model the "blue solution" properties and provide groundwork for rational synthesis of active, well-defined WOCs. More recent work has moved toward the study of first-row transition metal complexes. Manganese-based studies have highlighted the importance of the chelate effect for labile metals, leading to the synthesis of pincer-type pyalk derivatives. Beyond water oxidation, we believe the pyalk ligand and its derivatives will also prove useful in other oxidative transformations.

Chronic Family Stress and Adolescent Health: The Moderating Role of Emotion Regulation.

OBJECTIVE: The aim of the study was to assess whether the association between chronic family stress and physiological measures is moderated by emotion regulation strategies in an adolescent sample. METHODS: Chronic family stress was assessed via a semistructured interview and emotion regulation strategies (cognitive reappraisal and suppression) via questionnaire among 261 adolescents (14.57 (1.07) years). Several metabolic (waist-hip ratio, systolic and diastolic blood pressure) and inflammatory markers (basal and stimulated proinflammatory cytokine production in response to bacterial challenge) as well as glucocorticoid sensitivity were assessed. RESULTS: There were no main effects of chronic family stress, cognitive reappraisal, or suppression on physiological measures (all p's > .10). Emotion regulation moderated the association between chronic family stress and physiological measures. As chronic family stress increased, adolescents higher in cognitive reappraisal had smaller waist-hip ratios (B = -.003, SE = .001, p = .015) and lower systolic blood pressure (B = -.303, SE = .143, p = .035), although no moderation was found with respect to inflammatory markers and glucocorticoid sensitivity (all p's > .30). In addition, as chronic family stress increased, adolescents higher in suppression showed evidence of higher stimulated proinflammatory cytokine production (B = .046, SE = .020, p = .021) and lower glucocorticoid sensitivity (B = .051, SE = .021, p = .015), although basal inflammation and metabolic measures were not moderated by suppression (all p's > .50). CONCLUSIONS: This study suggests that the types of emotion regulation strategies used by adolescents may affect the extent to which chronic family stress affects important metabolic and immune processes.

Reversible Ligand-Centered Reduction in Low-Coordinate Iron Formazanate Complexes.

Coordination of redox-active ligands to metals is a compelling strategy for making reduced complexes more accessible. In this work, we explore the use of redox-active formazanate ligands in low-coordinate iron chemistry. Reduction of an iron(II) precursor occurs at milder potentials than analogous non-redox-active ß-diketiminate complexes, and the reduced three-coordinate formazanate-iron compound is characterized in detail. Structural, spectroscopic, and computational analysis show that the formazanate ligand undergoes reversible ligand-centered reduction to form a formazanate radical dianion in the reduced species. The less negative reduction potential of the reduced low-coordinate iron formazanate complex leads to distinctive reactivity with formation of a new N-I bond that is not seen with the ß-diketiminate analogue. Thus, the storage of an electron on the supporting ligand changes the redox potential and enhances certain reactivity.