Recovery from alcohol among urban Alaska Native and American Indian people.

Alaska Native and American Indian (ANAI) people experience dramatic alcohol-related health disparities compared to the general US population. Although the majority of ANAI people reside in urban settings (>70%), data are sparse on alcohol abstinence among urban ANAI people with alcohol use disorder (AUD). We conducted a qualitative study using a phenomenological approach to examine the experiences of 20 urban ANAI adults recovering from AUD. Participants' narratives had their own unique dimensions but shared a clear, interrelated trajectory of pre-alcohol recovery, a turning point, and ongoing alcohol recovery. All participants reported a combination of external and internal motivation to stop using alcohol.

Best Practices for Conducting Clinical Trials With Indigenous Children in the United States.

We provide guidance for conducting clinical trials with Indigenous children in the United States. We drew on extant literature and our experience to describe 3 best practices for the ethical and effective conduct of clinical trials with Indigenous children. Case examples of pediatric research conducted with American Indian, Alaska Native, and Native Hawaiian communities are provided to illustrate these practices. Ethical and effective clinical trials with Indigenous children require early and sustained community engagement, building capacity for Indigenous research, and supporting community oversight and ownership of research. Effective engagement requires equity, trust, shared interests, and mutual benefit among partners over time. Capacity building should prioritize developing Indigenous researchers. Supporting community oversight and ownership of research means that investigators should plan for data-sharing agreements, return or destruction of data, and multiple regulatory approvals. Indigenous children must be included in clinical trials to reduce health disparities and improve health outcomes in these pediatric populations. Establishment of the Environmental Influences on Child Health Outcomes Institutional Development Award States Pediatric Clinical Trials Network (ECHO ISPCTN) in 2016 creates a unique and timely opportunity to increase Indigenous children's participation in state-of-the-art clinical trials.

Perceptions of alcohol misuse among Alaska native health care system stakeholders: A qualitative exploration.

Although alcohol misuse is a priority for health care systems serving Alaska Native and American Indian (ANAI) people, stakeholders' perceptions of misuse are understudied. Patients (n = 34), providers (n = 20), and leaders (n = 16) at a Tribally owned and operated health care system reported that alcohol misuse results from the interaction of factors, including colonization, structural factors, social alienation, social norms about overdrinking introduced at the time of colonizing contact, coping with emotions, and beliefs about ANAI people and alcohol. Childhood exposure to alcohol misuse leads some ANAI people to avoid alcohol altogether, shedding light on the high levels of abstinence observed in ANAI communities.

Retrospective eDNA assessment of potentially harmful algae in historical ship ballast tank and marine port sediments.

Microalgal bloom events can cause major ecosystem disturbances, devastate local marine economies, and endanger public health. Therefore, detecting and monitoring harmful microalgal taxa is essential to ensure effective risk management in waterways used for fisheries, aquaculture, recreational activity, and shipping. To fully understand the current status and future direction of algal bloom distributions, we need to know how populations and ecosystems have changed over time. This baseline knowledge is critical for predicting ecosystem responses to future anthropogenic change and will assist in the future management of coastal ecosystems. We explore a NGS metabarcoding approach to rapidly identify potentially harmful microalgal taxa in 63 historic and modern Australian marine port and ballast tank sediment samples. The results provide a record of past microalgal distribution and important baseline data that can be used to assess the efficacy of shipping guidelines, nutrient pollution mitigation, and predict the impact of climate change. Critically, eDNA surveys of archived sediments were able to detect harmful algal taxa that do not produce microscopic fossils, such as Chattonella, Heterosigma, Karlodinium, and Noctiluca. Our data suggest a potential increase in Australian harmful microalgal taxa over the past 30 years, and confirm ship ballast tanks as key dispersal vectors. These molecular mapping tools will assist in the creation of policies aimed at reducing the global increase and spread of harmful algal taxa and help prevent economic and public-health problems caused by harmful algal blooms.

Incorporating Transgenerational Epigenetic Inheritance into Ecological Risk Assessment Frameworks.

Chronic exposure to environmental contaminants can induce heritable "transgenerational" modifications to organisms, potentially affecting future ecosystem health and functionality. Incorporating transgenerational epigenetic heritability into risk assessment procedures has been previously suggested. However, a critical review of existing literature yielded numerous studies claiming transgenerational impacts, with little compelling evidence. Therefore, contaminant-induced epigenetic inheritance may be less common than is reported in the literature. We identified a need for multigeneration epigenetic studies that extend beyond what could be deemed "direct exposure" to F1 and F2 gametes and also include subsequent multiple nonexposed generations to adequately evaluate transgenerational recovery times. Also, increased experimental replication is required to account for the highly variable nature of epigenetic responses and apparent irreproducibility of current studies. Further, epigenetic end points need to be correlated with observable detrimental organism changes before a need for risk management can be properly determined. We suggest that epigenetic-based contaminant studies include concentrations lower than current "EC10-20" or "Lowest Observable Effect Concentrations" for the organism's most sensitive phenotypic end point, as higher concentrations are likely already regulated. Finally, we propose a regulatory framework and optimal experimental design that enables transgenerational epigenetic effects to be assessed and incorporated into conventional ecotoxicological testing.

Light as a key driver of freshwater biofouling surface roughness in an experimental hydrocanal pipe rig.

Biofouling in canals and pipelines used for hydroelectric power generation decreases the flow capacity of conduits. A pipeline rig was designed consisting of test sections of varying substrata (PVC, painted steel) and light levels (transparent, frosted, opaque). Stalk-forming diatoms were abundant in both the frosted and transparent PVC pipes but negligible in the painted steel and opaque PVC pipes. Fungi were slightly more abundant in the painted steel pipe but equally present in all the other pipes while bacterial diversity was similar in all pipes. Photosynthetically functional biofouling (mainly diatoms) was able to develop in near darkness. Different biological fouling compositions generated differing friction factors. The highest friction factor was observed in the transparent pipe (densest diatom fouling), the lowest peak friction for the opaque PVC pipe (lowest fouling biomass), and with the painted steel pipe (high fouling biomass, but composed of fungal and bacterial crusts) being intermediate between the opaque and frosted PVC pipes.

Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems.

Drinking water assessments use a variety of microbial, physical, and chemical indicators to evaluate water treatment efficiency and product water quality. However, these indicators do not allow the complex biological communities, which can adversely impact the performance of drinking water distribution systems (DWDSs), to be characterized. Entire bacterial communities can be studied quickly and inexpensively using targeted metagenomic amplicon sequencing. Here, amplicon sequencing of the 16S rRNA gene region was performed alongside traditional water quality measures to assess the health, quality, and efficiency of two distinct, full-scale DWDSs: (i) a linear DWDS supplied with unfiltered water subjected to basic disinfection before distribution and (ii) a complex, branching DWDS treated by a four-stage water treatment plant (WTP) prior to disinfection and distribution. In both DWDSs bacterial communities differed significantly after disinfection, demonstrating the effectiveness of both treatment regimes. However, bacterial repopulation occurred further along in the DWDSs, and some end-user samples were more similar to the source water than to the postdisinfection water. Three sample locations appeared to be nitrified, displaying elevated nitrate levels and decreased ammonia levels, and nitrifying bacterial species, such as Nitrospira, were detected. Burkholderiales were abundant in samples containing large amounts of monochloramine, indicating resistance to disinfection. Genera known to contain pathogenic and fecal-associated species were also identified in several locations. From this study, we conclude that metagenomic amplicon sequencing is an informative method to support current compliance-based methods and can be used to reveal bacterial community interactions with the chemical and physical properties of DWDSs.

Engaging stakeholders to develop a depression management decision support tool in a tribal health system.

PURPOSE: Southcentral Foundation, an Alaska Native tribal health organization, has had a depression screening program in primary care since 2001. Program monitoring identified gaps in antidepressant refills and patients' follow-up with behavioral health services. With extensive stakeholder participation, we developed an electronic, patient-centered, depression-management decision support tool (DM-DST). Quality of life and other outcomes are being assessed in a separate study; this case study reports on the multi-year stakeholder engagement process. METHODS: Data sources included interviews with patients and providers from integrated primary care teams, notes from research meetings, steering committee meetings, and consultations with tribal health system leadership, human subjects review committees, providers, and software designers, and a pilot test of the DS-DMT with patients and providers. We analyzed these sources using qualitative methods to assess the impact of stakeholder input on project processes and outcomes. RESULTS: One comprehensive, iPad-based tool was originally planned to facilitate discussions about depression management. Stakeholder input emphasized the role of family and cultural context of depression and management and improving the usability of the DM-DST. Stakeholder direction led us to split the DM-DST into: (1) a brief iPad-based tool to facilitate conversations between patients and providers during clinic visits; and (2) a complementary Web site that provides detailed information and allows patients flexibility and time to learn more about depression and share information and preferences with family and friends. CONCLUSIONS: Stakeholder input across the project substantially modified the DM-DST to ensure cultural applicability to patients and providers and facilitate integration into clinics.

Culturally tailoring a secondary suicide prevention intervention for American Indian and Alaska Native people in substance use treatment.

BACKGROUND: Substance use treatment programs are ideal places for suicide prevention interventions. People who misuse substances are at elevated risk for suicide compared to the general population. However, most treatment programs do not incorporate suicide prevention, and none have been adapted for American Indian and Alaska Native (AI/AN) people. Preventing Addiction Related Suicide (PARS) is a suicide prevention module developed for use with people in treatment for substance misuse. A previous study demonstrated increased suicide help-seeking among this population. OBJECTIVE: Culturally adapt PARS for use with AI/AN communities. METHODS: We conducted focus groups and interviews with stakeholders in three Tribal health systems. We elicited feedback on PARS content, structure, and implementation. Data were analyzed using constant comparison. Results were used to adapt PARS and member checking was used to refine it. RESULTS: Participants unanimously endorsed using PARS in their health systems. Suggested adaptations included shortening the module, using community-specific information, removing jargon and stigmatizing language, and emphasizing cultural connectedness. DISCUSSION: This community-based, qualitative study adapted the PARS module for use with AI/AN communities. Research is needed to evaluate the clinical effectiveness of the adapted module. If found effective, this would represent the first evidence-based suicide prevention intervention among AI/AN individuals in treatment for substance misuse.

Risk, reward, and the double-edged sword: perspectives on pharmacogenetic research and clinical testing among Alaska Native people.

OBJECTIVES: Pharmacogenetic research and clinical testing raise important concerns for individuals and communities, especially where past medical research and practice has perpetrated harm and cultivated distrust of health care systems and clinicians. We investigated perceptions of pharmacogenetics among Alaska Native (AN) people. METHODS: We held four focus groups for 32 ANs in south central Alaska to elicit views about pharmacogenetics in general and for treatment of cardiovascular disease, breast cancer, depression, and nicotine addiction. We analyzed data for perceived risks and rewards of pharmacogenetics. RESULTS: Potential risks of pharmacogenetics included health care rationing, misuse of information, and stigma to individuals and the AN community. Potential rewards included decreased care costs, improved outcomes, and community development. Participants also discussed 8 contingent conditions that could mitigate risks and increase pharmacogenetic acceptability. CONCLUSIONS: Alaska Natives perceive pharmacogenetics as potentially benefitting and harming individuals, communities, and health systems, depending on methods and oversight. Researchers, clinicians, and administrators, especially in community-based clinic and health care systems serving minority populations, must address this "double-edged sword" to effectively conduct pharmacogenetics.

Resources, roadblocks and turning points: a qualitative study of American Indian/Alaska Native adults with type 2 diabetes.

Type 2 diabetes is a worldwide health problem that has reached epidemic proportions in some communities. Alaska Native and American Indian (AN/AI) people are disproportionately diagnosed with type 2 diabetes and incidence is increasing in many Alaska communities. Developing effective interventions requires understanding the social and psychological factors that impact effective management of diabetes, yet little is known about these factors in AN/AI communities. The objective of this study was to explore perceived psychosocial needs and barriers to management of diabetes among AN/AI adults with type 2 diabetes receiving care at the Alaska Native Primary Care Center (ANPCC) to inform programmatic efforts and potential future research. We conducted three focus groups and five interviews with 13 AN/AI adults with type 2 diabetes. Interview and focus group questions elicited perceived factors that affect management of diabetes, with a focus on the psychological, social and spiritual impacts of diabetes. Data were transcribed, coded and analyzed using thematic analysis. Key themes that emerged from these data included resources and roadblocks, as well as turning points in the trajectory of diabetes. Resources are factors with a perceived positive impact on management of diabetes, including: (1) knowledge and education about diabetes, (2) social support from other people with diabetes, (3) spirituality, and (4) self-efficacy. Roadblocks are factors with a perceived negative impact on management of diabetes and include: (1) self-reported lack of knowledge about nutrition and diet, (2) social difficulties caused by dietary restrictions, and (3) co-morbid medical conditions. Finally, turning points are experiences described by participants as having transformed roadblocks in resources and thus facilitating improvement in the management of diabetes. Future programmatic interventions to improve management of diabetes with this population should focus on improving dietary education and social support opportunities for newly-diagnosed individuals. Also, educational and support opportunities for family members and friends of individuals with diabetes should also be offered to facilitate understanding and support of their loved ones' management of diabetes, especially with regard to dietary restrictions in social settings. Efforts should also focus on strengthening newly-diagnosed individuals' self-efficacy and providing ongoing support as individuals progressively adjust to the illness over time and make behavioral changes. Future research with this population should explore the effects of family support groups and the possibility of Web-based or other alternative interventions for improving psychosocial health and management of diabetes efforts.

Culturally Adapting Caring Contacts for Suicide Prevention in Four Alaska Native and American Indian Communities.

AIM: Despite substantial tribal, state, and federal effort, American Indian and Alaska Native (AI/AN) suicide rates have changed little in the last 30 years, prompting attention to new and innovative approaches to this persistent health disparity. Suicide prevention interventions with demonstrated success in other populations may be useful in AI/AN communities. Caring Contacts is a suicide prevention intervention that has been adapted and shown to reduce suicide ideation, attempts, and deaths in other populations. CONCLUSION: Overall, AI/AN study participants in four diverse AI/AN communities endorsed the use of Caring Contacts for suicide prevention in their communities. Intervention adaptations for use in these communities centered primarily on message frequency and timing as well as expanding access to Caring Contacts. The results of this study may be applicable to other populations that experience suicide-related health disparities. METHODS: We used a community-based participatory research approach to gather qualitative data from community members, healthcare providers, and leaders in four AI/AN communities. These data were analyzed thematically and used to adapt Caring Contacts for use in a subsequent clinical trial with AI/AN people at high risk for suicide. RESULTS: A total of 189 community members and other health system stakeholders in four tribal communities participated in focus groups and interviews. Caring Contacts was perceived in all communities to be acceptable. Feedback for intervention adaptations focused on the themes of trial eligibility criteria; instruments; message frequency, timing, and content; and cultural considerations.

Measuring Attitudes About Alcohol Misuse and Dependence Among Alaska Native People Within a Tribal Health Care System.

OBJECTIVES: Attitudes about alcohol misuse and dependence influence alcohol use and help-seeking behavior. Alaska Native and American Indian (AN/AI) people have higher rates of alcohol-related morbidity and mortality but engage in treatment at lower rates than the general population. No validated instruments exist to assess attitudes of AN/AI people about alcohol misuse and dependence to inform treatment and prevention efforts. This study aimed to develop an instrument to assess public attitudes among AN/AI people of alcohol misuse and dependence. METHODS: This multiphase, mixed-methods study was conducted at Southcentral Foundation, a tribally owned health system serving 65,000 AN/AI people in Alaska. We conducted focus groups and interviews with health system users, providers, and leaders to adapt the Public Attitudes About Addiction Survey. The adapted instrument was piloted with 200 people. Cognitive interviews and exploratory and confirmatory factor analyses were used to refine the instrument, which were then administered to 777 AN/AI people. RESULTS: Initial exploratory factor analysis identified 5 factors, including 3 from the original Public Attitudes About Addiction Survey (moral, disease, nature), a combined psychology and sociology factor (psychosocial), and a new factor (environment). A final 4-factor model (psychosocial, moral, disease, nature) with 14 items had good fit with root mean square error of approximation (0.035; comparative fit index = 0.977; Tucker-Lewis index = 0.970; standardized root mean residual = 0.040) and loadings ranging from 0.41 to 0.80. CONCLUSIONS: This study developed the first instrument to assess AN/AI attitudes about alcohol misuse and dependence. This instrument has potential to inform alcohol-related treatment in AN/AI communities. Future research is warranted to adequately measure place-based contributors salient to AN/AI people.

Suicide-related care among patients who have experienced an opioid-involved overdose.

OBJECTIVE: Our objective was to describe suicide prevention care for individuals prescribed opioids or with opioid use disorder (OUD) and identify opportunities for improving this care. METHODS: Adult patients (n = 65) from four health systems with an opioid-involved overdose and clinicians (n = 21) who had contact with similar patients completed 30-60-min semi-structured interviews. A community advisory board contributed to development of all procedures, and interpretation and summary of findings. RESULTS: Patients were mostly female (59%), White (63%) and non-Hispanic (77%); 52 were prescribed opioids, 49% had diagnosed OUD, and 42% experienced an intentional opioid-involved overdose. Findings included: 1) when prescribed an opioid or treated for OUD, suicide risks were typically not discussed; 2) 35% of those with an intentional opioid-involved overdose and over 80% with an unintentional overdose reported no discussion of suicidal ideation when treated for the overdose; and 3) suicide-related follow-up care was uncommon among those with unintentional overdoses despite suicidal ideation being reported by >20%. Clinicians reported that when prescribing opioids or treating OUD, post-overdose suicide-related screening or counseling was not done routinely. CONCLUSIONS: There were several opportunities to tailor suicide prevention care for patients who were treated for opioid-involved overdoses within health systems.

Use of DNA barcoding to reveal species composition of convenience seafood.

Increased education of consumers can be an effective tool for conservation of commercially harvested marine species when product labeling is accurate and allows an informed choice. However, generic labeling (e.g., as white fish or surimi) and mislabeling of seafood prevents this and may erode consumer confidence in seafood product labels in general. We used DNA barcoding to identify the species composition of two types of convenience seafood (i.e., products processed for ease of consumption): fish fingers (long pieces of fish covered with bread crumbs or batter, n = 241) and seafood sticks (long pieces of cooked fish, n = 30). In products labeled as either white fish or surimi, four teleost species were present. Less than 1.5% of fish fingers with species-specific information were mislabeled. Results of other studies show substantially more mislabeling (e.g., >25%) of teleost products, which likely reflects the lower economic gains associated with mislabeling of convenience seafood compared with whole fillets. In addition to species identification, seafood product labels should be required to contain information about, for example, harvesting practices, and our data indicate that consumers can have reasonable confidence in the accuracy of the labels of convenience seafood and thus select brands on the basis of information about current fisheries practice.

Using the electronic health record to identify suicide risk factors in an Alaska Native Health System.

Suicide rates are higher in some Alaska Native and American Indian communities than the general U.S. population. Screening for suicide risk typically requires self-report, but many people may not engage with conventional screening because of distrust or are reluctant to disclose thoughts of suicide. Resource-sensitive methods of detecting suicide risk are needed. This study identifies routinely collected electronic health record data to identify demographic, clinical, and utilization factors associated with suicide-related visits in a tribal health care system. In this retrospective, case-control study, cases were defined as any person with a suicide-related visit from 2012 to 2015. Cases and controls were matched by age, sex, and urban/rural residence. We used conditional logistic regression to estimate odds ratios, which were interpreted as prevalence ratios (PR) based on the rare outcome assumption. The dataset included 314 cases and 1,169 controls. In the year before the index visit, cases had higher prevalence of poisoning or overdose (PR = 13.4, 95% confidence interval [CI] [3.5, 51.7]), emergency department and urgent care visits (PR = 15.8, 95% CI [6.6, 38.1]), and hospitalizations (PR = 4.5, 95% CI [3.0, 6.8]). Electronic health records can be used to identify factors that are significantly associated with suicide risk among those who may not be flagged by screening. Risk detection through electronic health record assessment might increase clinical workload in the short term, but this change would be offset by downstream prevention of suicide-related events. Such efforts could improve suicide risk detection and help to improve suicide-related health disparities in Alaska Native and American Indian populations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Validating a predictive algorithm for suicide risk with Alaska Native populations.

INTRODUCTION: The American Indian/Alaska Native (AI/AN) suicide rate in Alaska is twice the state rate and four times the U.S. rate. Healthcare systems need innovative methods of suicide risk detection. The Mental Health Research Network (MHRN) developed suicide risk prediction algorithms in a general U.S. METHODS: We applied MHRN predictors and regression coefficients to electronic health records of AI/AN patients aged ≥13 years with behavioral health diagnoses and primary care visits between October 1, 2016, and March 30, 2018. Logistic regression assessed model accuracy for predicting and stratifying risk for suicide attempt within 90 days after a visit. We compared expected to observed risk and assessed model performance characteristics. RESULTS: 10,864 patients made 47,413 primary care visits. Suicide attempt occurred after 589 (1.2%) visits. Visits in the top 5% of predicted risk accounted for 40% of actual attempts. Among visits in the top 0.5% of predicted risk, 25.1% were followed by suicide attempt. The best fitting model had an AUC of 0.826 (95% CI: 0.809-0.843). CONCLUSIONS: The MHRN model accurately predicted suicide attempts among AI/AN patients. Future work should develop clinical and operational guidance for effective implementation of the model with this population.

Contingency management for alcohol use disorder reduces cannabis use among American Indian and Alaska Native adults.

OBJECTIVE: Determine whether a culturally tailored contingency management (CM) intervention targeting alcohol abstinence resulted in secondary effects on cannabis use among American Indian and Alaska Native (AI/AN) adults. METHODS: The research team conducted this secondary data analysis to examine cannabis abstinence using data from a randomized control trial of CM for alcohol use among three AI/AN-serving organizations. One hundred and fifty-eight adults met the randomization criteria (i.e., submission of 50% or more urine samples and one alcohol-positive urine test during a 4-week, pre-randomization, observation period). For 12 weeks after randomization, participants received incentives for submitting a urine test negative for ethyl glucuronide (EtG < 150 ng/mL, CM group) or incentives for submitting a urine sample regardless of abstinence (Non-contingent [NC] Control group). Generalized linear mixed effects models assessed group differences in cannabis abstinence during the intervention, verified by urine tetrahydrocannabinol negative tests (11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid <50 ng/mL). RESULTS: At baseline, 42.2% (n = 35) of participants in the NC group and 40.0% (n = 30) of those in the CM group had a cannabis positive urine test. An overall intervention by time interaction was detected for a cannabis negative urine test (χ2 = 13.40, p = 0.001). Compared to the NC group, the CM group had 3.92 (95% CI:1.23-12.46) times higher odds of having a cannabis negative urine test during the intervention period and 5.13 (95% CI:1.57-16.76) times higher odds of having a negative cannabis test at the end of intervention period. CONCLUSION: CM addressing alcohol misuse may be an effective strategy for decreasing cannabis use among AI/AN adults. TRIAL REGISTRATION: ClinicalTrials.gov number, Identifier: NCT02174315.

Redox non-innocence of thioether crowns: spectroelectrochemistry and electronic structure of formal nickel(III) complexes of aza-thioether macrocycles.

The Ni(II) complexes [Ni([9]aneNS(2)-CH(3))(2)](2+) ([9]aneNS(2)-CH(3)=N-methyl-1-aza-4,7-dithiacyclononane), [Ni(bis[9]aneNS(2)-C(2)H(4))](2+) (bis[9]aneNS(2)-C(2)H(4)=1,2-bis-(1-aza-4,7-dithiacyclononylethane) and [Ni([9]aneS(3))(2)](2+) ([9]aneS(3)=1,4,7-trithiacyclononane) have been prepared and can be electrochemically and chemically oxidized to give the formal Ni(III) products, which have been characterized by X-ray crystallography, UV/Vis and multi-frequency EPR spectroscopy. The single-crystal X-ray structure of [Ni(III)([9]aneNS(2)-CH(3))(2)](ClO(4))(6)·(H(5)O(2))(3) reveals an octahedral co-ordination at the Ni centre, while the crystal structure of [Ni(III)(bis[9]aneNS(2)-C(2)H(4))](ClO(4))(6)·(H(3)O)(3)·3H(2)O exhibits a more distorted co-ordination. In the homoleptic analogue, [Ni(III)([9]aneS(3))(2)](ClO(4))(3), structurally characterized at 30 K, the Ni-S distances [2.249(6), 2.251(5) and 2.437(2) Å] are consistent with a Jahn-Teller distorted octahedral stereochemistry. [Ni([9]aneNS(2)-CH(3))(2)](PF(6))(2) shows a one-electron oxidation process in MeCN (0.2 M NBu(4)PF(6), 293 K) at E(½)=+1.10 V versus Fc(+)/Fc assigned to a formal Ni(III)/Ni(II) couple. [Ni(bis[9]aneNS(2)-C(2)H(4))](PF(6))(2) exhibits a one-electron oxidation process at E(½)=+0.98 V and a reduction process at E(½)=-1.25 V assigned to Ni(II)/Ni(III) and Ni(II)/Ni(I) couples, respectively. The multi-frequency X-, L-, S-, K-band EPR spectra of the 3+ cations and their 86.2% (61)Ni-enriched analogues were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6%, 42.8% and 37.2% Ni character in [Ni([9]aneNS(2)-CH(3))(2)](3+), [Ni(bis[9]aneNS(2)-C(2)H(4))](3+) and [Ni([9]aneS(3))(2)](3+), respectively, consistent with DFT calculations, and reflecting delocalisation of charge onto the S-thioether centres. EPR spectra for [(61)Ni([9]aneS(3))(2)](3+) are consistent with a dynamic Jahn-Teller distortion in this compound.

Advanced electron paramagnetic resonance and density functional theory study of a {2Fe3S} cluster mimicking the active site of [FeFe] hydrogenase.

Despite extensive investigations of the active site of the [FeFe] hydrogenases, many details concerning the properties of the "hydrogen converting cluster" are not yet fully understood. The complexity of the so-called H-cluster is one of the main difficulties in studying the properties of its components. The present study is aimed at the mixed-valence EPR active [Fe2(µ-CO)(CO)3(CN)2{MeSCH2C(Me)(CH2S)2}](1-) that is structurally closely related to the redox active binuclear part of the H-cluster in its CO-inhibited oxidized state. In this work, we present a characterization of this compound by advanced pulse EPR methods. The accurate determination of the (57)Fe, (1)H, (2)H, (14)N, and (15)N electron nuclear hyperfine interactions provided a very detailed picture of the electronic structure of this complex. A theoretical study using density functional theory (DFT) calculations identified possible isomers of the compound and further refined the knowledge about its properties. It was found that upon one electron oxidation of the parent Fe(I)-Fe(I) complex, the dominant mixed-valence Fe(I)-Fe(II) species is the one in which the CN ligand of the iron center that is distal to the thioether moves from the basal to the apical position. The unpaired spin distribution of the model complex is found to be clearly different from that of the native H-cluster. These differences are discussed and provide new insight into the functional features of the [FeFe] hydrogenase active site.