Learning with our peers: peer-led versus instructor-led debriefing for simulated crises, a randomized controlled trial.

BACKGROUND: Although peer-assisted learning is known to be effective for reciprocal learning in medical education, it has been understudied in simulation. We aimed to assess the effectiveness of peer-led compared to instructor-led debriefing for non-technical skill development in simulated crisis scenarios. METHODS: Sixty-one undergraduate medical students were randomized into the control group (instructor-led debriefing) or an intervention group (peer debriefer or peer debriefee group). After the pre-test simulation, the participants underwent two more simulation scenarios, each followed by a debriefing session. After the second debriefing session, the participants underwent an immediate post-test simulation on the same day and a retention post-test simulation two months later. Non-technical skills for the pre-test, immediate post-test, and retention tests were assessed by two blinded raters using the Ottawa Global Rating Scale (OGRS). RESULTS: The participants' non-technical skill performance significantly improved in all groups from the pre-test to the immediate post-test, with changes in the OGRS scores of 15.0 (95% CI [11.4, 18.7]) in the instructor-led group, 15.3 (11.5, 19.0) in the peer-debriefer group, and 17.6 (13.9, 21.4) in the peer-debriefee group. No significant differences in performance were found, after adjusting for the year of medical school training, among debriefing modalities (P = 0.147) or between the immediate post-test and retention test (P = 0.358). CONCLUSIONS: Peer-led debriefing was as effective as instructor-led debriefing at improving undergraduate medical students' non-technical skill performance in simulated crisis situations. Peer debriefers also improved their simulated clinical skills. The peer debriefing model is a feasible alternative to the traditional, costlier instructor model.

Competence By Design: a transformational national model of time-variable competency-based postgraduate medical education.

Postgraduate medical education is an essential societal enterprise that prepares highly skilled physicians for the health workforce. In recent years, PGME systems have been criticized worldwide for problems with variable graduate abilities, concerns about patient safety, and issues with teaching and assessment methods. In response, competency based medical education approaches, with an emphasis on graduate outcomes, have been proposed as the direction for 21st century health profession education. However, there are few published models of large-scale implementation of these approaches. We describe the rationale and design for a national, time-variable competency-based multi-specialty system for postgraduate medical education called Competence by Design. Fourteen innovations were bundled to create this new system, using the Van Melle Core Components of competency based medical education as the basis for the transformation. The successful execution of this transformational training system shows competency based medical education can be implemented at scale. The lessons learned in the early implementation of Competence by Design can inform competency based medical education innovation efforts across professions worldwide.

Implementing Competence Committees on a National Scale: Design and Lessons Learned.

Competence committees (CCs) are a recent innovation to improve assessment decision-making in health professions education. CCs enable a group of trained, dedicated educators to review a portfolio of observations about a learner's progress toward competence and make systematic assessment decisions. CCs are aligned with competency based medical education (CBME) and programmatic assessment. While there is an emerging literature on CCs, little has been published on their system-wide implementation. National-scale implementation of CCs is complex, owing to the culture change that underlies this shift in assessment paradigm and the logistics and skills needed to enable it. We present the Royal College of Physicians and Surgeons of Canada's experience implementing a national CC model, the challenges the Royal College faced, and some strategies to address them. With large scale CC implementation, managing the tension between standardization and flexibility is a fundamental issue that needs to be anticipated and addressed, with careful consideration of individual program needs, resources, and engagement of invested groups. If implementation is to take place in a wide variety of contexts, an approach that uses multiple engagement and communication strategies to allow for local adaptations is needed. Large-scale implementation of CCs, like any transformative initiative, does not occur at a single point but is an evolutionary process requiring both upfront resources and ongoing support. As such, it is important to consider embedding a plan for program evaluation at the outset. We hope these shared lessons will be of value to other educators who are considering a large-scale CBME CC implementation.

Novel use of transesophageal echocardiography to optimize hemodynamics and patient positioning during prone scoliosis surgery and safety considerations in the setting of intraoperative neuromonitoring: a case report.

PURPOSE: The prone position can lead to anatomical compression of the thoracic cavity resulting in reduced cardiac output, especially in the context of chest wall deformities commonly present in patients with scoliosis. There are no protocols for using transesophageal echocardiography (TEE) to optimize prone positioning and for safe use of TEE during cases requiring neuromonitoring. CLINICAL FEATURES: We present a case of a 23-yr-old male with Cornelia de Lange syndrome undergoing elective posterior spinal fusion for syndromic scoliosis who developed severe refractory hypotension and cardiac arrest in the prone position. After hemodynamic stabilization in the intensive care unit, the patient returned to the operating room on postoperative day 2 for completion of his spinal fusion. Transesophageal echocardiography determined the optimal position of longitudinal bolster placements associated with minimal left ventricular compression in the supine position. The patient was then proned and intraoperative hemodynamics during the second surgery remained stable. Owing to the special considerations of using TEE in the prone position with neuromonitoring, we describe technical aspects to consider to protect the equipment and patient. CONCLUSION: Patients with compliant chest walls or thoracic deformities are at risk of hemodynamic instability in the prone position. Intraoperative TEE can be used in the supine patient prior to proning to determine optimal longitudinal bolster positioning to minimize cardiac compression. Transesophageal echocardiography used during spine surgery in the prone position with neuromonitoring and motor-evoked potentials requires special considerations for patient safety.

RéSUMé: OBJECTIF: La position ventrale peut entraîner une compression anatomique de la cavité thoracique provoquant une réduction du débit cardiaque, en particulier dans le contexte de déformations de la paroi thoracique, fréquentes chez les patients atteints de scoliose. Il n'existe aucun protocole guidant l'utilisation de l'échocardiographie transœsophagienne (ETO) pour optimiser le positionnement ventral et pour favoriser l'utilisation sécuritaire de l'ETO dans les cas nécessitant un neuro-monitorage. CARACTéRISTIQUES CLINIQUES: Nous présentons le cas d'un homme de 23 ans atteint d'un syndrome de Cornelia de Lange bénéficiant d'une fusion spinale postérieure non urgente pour traiter une scoliose syndromique; le patient a manifesté une hypotension réfractaire sévère et un arrêt cardiaque en position ventrale. Après stabilisation hémodynamique à l'unité de soins intensifs, le patient est retourné en salle d'opération au jour postopératoire 2 pour terminer sa fusion spinale. L'échocardiographie transœsophagienne a permis de déterminer la position optimale des traversins longitudinaux qui était associée à une compression ventriculaire gauche minimale en décubitus dorsal. Le patient a ensuite été positionné sur le ventre, et les valeurs hémodynamiques peropératoires sont restées stables au cours de la deuxième chirurgie. En raison des considérations particulières de l'utilisation de l'ETO en position ventrale avec neuro-monitorage, nous décrivons les aspects techniques à prendre en compte pour protéger l'équipement et le patient. CONCLUSION: Les patients présentant des parois thoraciques compliantes ou des déformations thoraciques sont à risque d'instabilité hémodynamique en position ventrale. L'ETO peropératoire peut être utilisée chez le patient en décubitus dorsal avant le positionnement ventral pour déterminer le positionnement optimal des traversins longitudinaux afin de minimiser la compression cardiaque. L'utilisation de l'échocardiographie transœsophagienne lors d'une chirurgie du rachis en position ventrale avec neuro-monitorage et potentiels évoqués moteurs nécessite des considérations particulières en ce qui a trait à la sécurité des patients.

Validity of entrustment scales within anesthesiology residency training.

INTRODUCTION: Competency-based medical education requires robust assessment in authentic clinical environments. Using work-based assessments, entrustment scales have emerged as a means of describing a trainee's ability to perform competently. Nevertheless, psychometric properties of entrustment-based assessment are relatively unknown, particularly in anesthesiology. This study assessed the generalizability and extrapolation evidence for entrustment scales within a program of assessment during anesthesiology training. METHODS: Entrustment scores were collected during the first seven blocks of training for three resident cohorts. Entrustment scores were assessed during daily evaluations using a Clinical Case Assessment Tool (CCAT) within the preoperative, intraoperative, and postoperative setting. The reliability of the entrustment scale was estimated using generalizability theory. Spearman's correlations measured the relationship between median entrustment scores and percentiles scores on the Anesthesia Knowledge Test (AKT)-1 and AKT-6, mean Objective Structured Clinical Examination (OSCE) scores, and rankings of performance by the Clinical Competence Committee (CCC). RESULTS: Analyses were derived from 2,309 CCATs from 35 residents. The reliability or generalizability (G) coefficient of the entrustment scale was 0.73 (95% confidence interval [CI], 0.70 to 0.76), and the internal consistency was 0.86 (95% CI, 0.84 to 0.88). Intraoperative entrustment scores significantly correlated with the AKT-6 (rho = 0.51, P = 0.01), mean OSCE (rho = 0.45, P = 0.04), and CCC performance rankings (rho = 0.52, P = 0.006). CONCLUSION: As part of an assessment program, entrustment scales used early during anesthesiology training showed evidence of validity. Intraoperative entrustment scores had good reliability and showed acceptable internal consistency. Interpreting entrustment scores in this setting may constitute a valuable adjunct complementing traditional summative evaluations.

RéSUMé: INTRODUCTION: La formation médicale fondée sur les compétences nécessite une évaluation rigoureuse dans des environnements cliniques authentiques. Se fondant sur des évaluations basées sur le travail, les échelles de confiance sont apparues comme une méthode pour décrire la capacité d'un résident à performer de façon compétente. Toutefois, les propriétés psychométriques de l'évaluation basée sur la confiance sont relativement peu connues, particulièrement en anesthésiologie. Cette étude a évalué les données de généralisabilité et d'extrapolation des échelles de confiance dans le cadre d'un programme d'évaluation pendant la formation en anesthésiologie. MéTHODE: Les notes sur les échelles de confiance ont été colligées pendant les sept premiers blocs de formation de trois cohortes de résidents. Les notes sur les échelles de confiance ont été évaluées pendant les évaluations quotidiennes à l'aide d'un Outil d'évaluation des compétences cliniques (CCAT ­ Clinical Case Assessment Tool) dans les cadres préopératoire, peropératoire et postopératoire. La fiabilité de l'échelle de confiance a été estimée à l'aide de la théorie de la généralisabilité. Les corrélations de Spearman ont mesuré la relation entre des notes moyennes sur l'échelle de confiance et les scores de percentile aux examens de connaissances en anesthésiologie AKT-1 et AKT-6, les scores moyens à l'Examen clinique objectif structuré (ECOS), et les classements de performance par le Comité de compétences cliniques (CCC). RéSULTATS: Les analyses ont été dérivées à partir de 2309 résultats CCAT de 35 résidents. Le coefficient de fiabilité ou de généralisabilité (G) de l'échelle de confiance était de 0,73 (intervalle de confiance [IC] 95 %, 0,70 à 0,76), et la cohérence interne était de 0,86 (IC 95 %, 0,84 à 0,88). Les scores de confiance peropératoires étaient corrélés de manière significative aux scores sur l'AKT-6 (rho = 0,51, P = 0,01), aux scores moyens à l'ECOS (rho = 0,45, P = 0,04) et aux classements de performance du CCC (rho = 0,52, P = 0,006). CONCLUSION: Dans le cadre d'un programme d'évaluation, la validité des échelles de confiance utilisées en début de la formation en anesthésiologie a été éprouvée. Les scores de confiance peropératoires ont démontré une bonne fiabilité et une cohérence interne acceptable. L'interprétation des scores de confiance dans ce cadre pourrait constituer un ajout précieux qui complèterait les évaluations sommatives.

Logging in: a comparative analysis of electronic health records versus anesthesia resident-driven logbooks.

PURPOSE: Resident logbooks (RLBs) documenting clinical case exposure are widespread in medical education despite evidence of poor accuracy. Electronic health records (e.g., anesthesia information management systems [AIMS]) may provide advantages for auditing longitudinal case exposure. We evaluated the agreement between AIMS and RLBs for tracking case exposure during anesthesiology residency. METHODS: We performed a historical cohort study with anesthesiology residents (2011-2018, all of whom used a RLB contemporaneously with AIMS) working in a multisite academic health sciences network. The primary outcome was total case-load logging; secondary outcomes were volumes for seven surgical specialties (general, gynecology, neuro, orthopedic, thoracic, urology, and vascular surgery). Correlation of case numbers tracked by AIMS vs RLB was assessed using Pearson correlation; agreement was determined using Bland-Altman plots and intraclass correlation coefficients (ICC). RESULTS: Data from 27 anesthesiology residents were collected. Overall, mean (standard deviation) case numbers were generally greater with AIMS vs RLB [649 (103) vs 583 (191); P = 0.049). Total case volumes between systems had moderate correlation (r = 0.50) and agreement (intraclass correlation coefficient [ICC], 0.42; 95% CI, 0.34 to 0.59). Bland-Altman plots showed variable agreement between AIMS and RLB data [mean (SD) bias = 66 (166) cases]. For general, gynecology, neuro, orthopedic, thoracic, urology, and vascular surgery, there was a range of poor to moderate agreement (ICC, 0.23-0.57) between AIMS and RLB. CONCLUSION: For anesthesiology resident case-logging, the number of cases logged in an AIMS was higher with lower variance compared with RLBs. Anesthesia information management systems vs RLB data showed low-moderate correlation and agreement. Given the additional time and resources required for RLBs, AIMS may be a superior method for tracking cases where available.

RéSUMé: OBJECTIF: Les logbooks des résidents documentant leur exposition à des cas cliniques sont répandus dans la formation médicale et ce, malgré des données probantes déplorant leur manque de précision. Les dossiers médicaux informatisés (par ex., les systèmes de gestion de l'information en anesthésie [SGIA]) pourraient présenter des avantages pour le contrôle de l'exposition longitudinale des résidents aux cas. Notre étude a évalué la concordance entre les SGIA et les logbooks pour l'exposition aux cas pendant la résidence en anesthésiologie. MéTHODE: Nous avons réalisé une étude de cohorte historique auprès de résidents en anesthésiologie (2011­2018, tous les résidents ayant utilisé un logbook simultanément aux SGIA) travaillant dans un réseau universitaire de sciences de la santé multisite. Le critère d'évaluation principal était l'enregistrement du nombre de cas total; les critères d'évaluation secondaires comprenaient les volumes pour sept spécialités chirurgicales (soit la chirurgie générale, gynécologique, orthopédique, thoracique, urologique, vasculaire et la neurochirurgie). La corrélation entre le nombre de cas enregistrés dans les SGIA vs les logbooks a été évaluée à l'aide d'une corrélation de Pearson; l'agrément a été déterminé à l'aide d'un graphique de Bland­Altman et de coefficients de corrélation intraclasse (CCI). RéSULTATS: Les données de 27 résidents en anesthésiologie ont été colligées. Globalement, les nombres de cas moyens (écart type) étaient en général plus élevés dans les SGIA que dans les logbooks [649 (103) vs 583 (191); P = 0,049). Les volumes de cas totaux entre les systèmes présentaient une corrélation (r = 0,50) et un agrément (coefficient de corrélation intraclasse [CCI], 0,42; IC 95 %, 0,34 à 0,59) modérés. Les graphiques de Bland­Altman ont démontré un agrément variable entre les données des SGIA et celles des logbooks [biais moyen (ÉT) = 66 (166) cas]. Pour les chirurgies générales, gynécologiques, orthopédiques, thoraciques, urologique, vasculaires et neurochirurgies, l'agrément allait de faible à modéré (CCI, 0,23-0,57) entre les SGIA et les logbooks. CONCLUSION: En ce qui a trait à l'enregistrement des cas des résidents en anesthésiologie, le nombre de cas enregistrés dans un SGIA était plus élevé et présentait une variance moindre que dans les logbooks. Les données des systèmes de gestion de l'information en anesthésie vs des logbooks ont affiché une corrélation et un agrément faible à modéré. Étant donné le temps et les ressources supplémentaires nécessaires pour compléter les logbooks, les SGIA pourraient constituer une méthode supérieure pour le suivi des cas, lorsqu'un tel système est disponible.

Evaluation of attractive interactions in the second coordination sphere of iron complexes containing pendant amines.

The interactions between pendant amines in the second coordination sphere and ligands in the first coordination sphere are important for understanding the structures and reactivity of complexes containing PR2NR'2 ligands, which have been shown to be highly active H2 oxidation/production catalysts. A series of [Fe(PPh2NBn2)2(X)(Y)]n+ complexes have been prepared and structurally characterized. These complexes have two different ligands with which the pendant amines of the diphosphine ligand can interact. The solid state structure of cis-Fe(PPh2NBn2)2Cl2 reveals that the six-membered rings adjacent to the P atoms are in a boat confirmation, resulting in close NP distances that suggests the P atoms have a greater affinity for the lone pair of electrons on the N atom than chloride ligands. Similarly, boat conformations are observed for both rings adjacent to the hydride ligands of trans-[HFe(PPh2NBn2)2(CH3CN)]+ and trans-HFe(PPh2NBn2)2Cl, resulting in short NH distances. Spectroscopic and computational studies of trans-[HFe(PPh2NBn2)2(CO)]+, trans-[HFe(PPh2NBn2)(PPh2NBn2H)(CO)]2+, and trans-[HFe(PPh2NBn2)2(H2)]+ indicate the complexes are more stable when the pendant amines in boat conformations are adjacent to the hydride ligand. These data suggest an attractor ordering of H- > CO > H2 > PR3 > Cl- ∼ CH3CN.

A Systematic Review of the Impact of Surgical Special Care Units on Patient Outcomes and Health Care Resource Utilization.

Perioperative intermediate care units (termed surgical special care units) have been widely implemented across health systems because they are believed to improve surveillance and management of high-risk surgical patients. Our objective was to conduct a systematic review to investigate the effects of a 3-level model of perioperative care delivery (ie, ward, surgical special care unit, or intensive care unit) compared to a 2-level model of care (ie, ward, intensive care unit) on postoperative outcomes. Our protocol was registered with PROSPERO, the international prospective register of systematic reviews (CRD42015025155). Randomized controlled studies and nonrandomized comparator studies were included. We performed a systematic search of Medline, Cumulative Index to Nursing and Allied Health Literature, Embase, and the Cochrane library (inception - 11/2017). The primary outcome was mortality; secondary outcomes included length of stay and hospital costs. We identified 1995 citations with our search, and 21 studies met eligibility criteria (2 randomized controlled studies and 19 nonrandomized comparator studies; 44,134 patients in total). Surgical special care units were characterized by continuous monitoring (12 studies), the absence of mechanical ventilation (8 studies), nurse-to-patient ratios (range, 1:2-1:4), and number of beds (median: 5; range: 3-33). Thirteen studies reported on mortality. Notable findings included no observed difference in overall in-hospital mortality, but an apparent increase in intensive care unit mortality in a 3-level model of care. This may reflect a decanting of lower acuity patients from the intensive care unit to the surgical special care unit. No significant difference was found in hospital length of stay; however, 2 studies demonstrated reductions in hospital costs with the implementation of a surgical special care unit. Significant clinical and methodological heterogeneity precluded pooled analysis. Given the prevalence of surgical special care units, the results of our review suggest that additional methodologically rigorous investigations are needed to understand the effect of these units on the surgical population.

Preparing anesthesiology faculty for competency-based medical education.

PURPOSE: Competency-based medical education (CBME) is quickly becoming the dominant organizing principle for medical residency programs. As CBME requires changes in the way medical education is delivered, faculty will need to acquire new skills in teaching and assessment in order to navigate the transition. In this paper, we examine the evidence supporting best practices in faculty development, propose strategies for faculty development for CBME-based residency programs, and discuss the results of faculty development initiatives at the pioneering anesthesia CBME residency program at the University of Ottawa. SOURCE: Review of the current literature and information from the University of Ottawa anesthesia residency program. PRINCIPAL FINDINGS: Faculty development is critical to the success of CBME programs. Attention must be paid to the competence of faculty to teach and assess all of the CanMEDS roles. At the University of Ottawa, some faculty development initiatives were very successful, while others were hindered by factors both internal and external to the residency program. Many faculty development activities had low attendance rates. CONCLUSIONS: Faculty development must be considered in the rollout of any new educational initiative. Experts suggest that faculty development for CBME should incorporate educational activities using multiple teaching and delivery methods, and should be offered longitudinally through the planning, development, and implementation phases of curriculum change. Additionally, these educational activities must continue until all faculty have demonstrated an acceptable level of competence. Faculty buy-in is paramount to the successful delivery of any faculty development program that is not mandatory in nature.

Cerebral Oximetry Monitoring to Maintain Normal Cerebral Oxygen Saturation during High-risk Cardiac Surgery: A Randomized Controlled Feasibility Trial.

BACKGROUND: Cerebral oxygen desaturation during cardiac surgery has been associated with adverse perioperative outcomes. Before a large multicenter randomized controlled trial (RCT) on the impact of preventing desaturations on perioperative outcomes, the authors undertook a randomized prospective, parallel-arm, multicenter feasibility RCT to determine whether an intervention algorithm could prevent desaturations. METHODS: Eight Canadian sites randomized 201 patients between April 2012 and October 2013. The primary outcome was the success rate of reversing cerebral desaturations below 10% relative to baseline in the intervention group. Anesthesiologists were blinded to the cerebral saturation values in the control group. Intensive care unit personnel were blinded to cerebral saturation values for both groups. Secondary outcomes included the area under the curve of cerebral desaturation load, enrolment rates, and a 30-day follow-up for adverse events. RESULTS: Cerebral desaturations occurred in 71 (70%) of the 102 intervention group patients and 56 (57%) of the 99 control group patients (P = 0.04). Reversal was successful in 69 (97%) of the intervention group patients. The mean cerebral desaturation load (SD) in the operating room was smaller for intervention group patients compared with control group patients (104 [217] %.min vs. 398 [869] %.min, mean difference, -294; 95% CI, -562 to -26; P = 0.03). This was also true in the intensive care unit (P = 0.02). There were no differences in adverse events between the groups. CONCLUSIONS: Study sites were successful in reversal of desaturation, patient recruitment, randomization, and follow-up in cardiac surgery, supporting the feasibility of conducting a large multicenter RCT.

OptiSpot: minimizing application deployment cost using spot cloud resources.

The spot instance model is a virtual machine pricing scheme in which some resources of cloud providers are offered to the highest bidder. This leads to the formation of a spot price, whose fluctuations can determine customers to be overbid by other users and lose the virtual machine they rented. In this paper we propose OptiSpot, a heuristic to automate application deployment decisions on cloud providers that offer the spot pricing model. In particular, with our approach it is possible to determine: (i) which and how many resources to rent in order to run a cloud application, (ii) how to map the application components to the rented resources, and (iii) what spot price bids to use to minimize the total cost while maintaining an acceptable level of performance. To drive the decision making, our algorithm combines a multi-class queueing network model of the application with a Markov model that describes the stochastic evolution of the spot price and its influence on virtual machine reliability. We show, using a model developed for a real enterprise application and historical traces of the Amazon EC2 spot instance prices, that our heuristic finds low cost solutions that indeed guarantee the required levels of performance. The performance of our heuristic method is compared to that of nonlinear programming and shown to markedly accelerate the finding of low-cost optimal solutions.

Water-assisted proton delivery and removal in bio-inspired hydrogen production catalysts.

Electrocatalysts for H2 production are envisioned to play an important role in renewable energy utilization systems. Nickel-based catalysts featuring pendant amines functioning as proton relays in the second coordination sphere of the metal center have led to catalysts achieving turnover frequencies as high as 10(7) s(-1) for H2 production. The fastest rates are observed when water is present in solution, with rates up to 10(3) times faster than those found in dry solvent. The focus of this paper is to provide mechanistic insight into the unexpected enhancement due to water. Addition of H2 to [Ni(P(Cy)2N(R')2)2](2+) was previously shown to give three isomers of a Ni(0) product with two protonated amines, where the N-H can be endo or exo to the Ni. By investigating the deprotonation of these two N-protonated Ni(0) intermediates resulting from the addition of H2 to [Ni(P(Cy)2N(R')2)2](2+), we observe by NMR spectroscopy studies an enhancement in the rate of deprotonation for protons positioned on the pendant amine next to the metal (endo) vs. protons that are positioned away from the metal (exo). Computational studies suggest that for smaller bases, the desolvation energy of the exogenous base is the primary contribution limiting the rate of endo deprotonation, while steric accessibility and facile proton movement also contribute. For more bulky bases, steric accessibility can play the dominant role. The significant reduction in these barriers observed in the presence of water has important implications for disfavoring less productive catalytic pathways and increasing catalytic rates.

Toward molecular catalysts by computer.

CONSPECTUS: Rational design of molecular catalysts requires a systematic approach to designing ligands with specific functionality and precisely tailored electronic and steric properties. It then becomes possible to devise computer protocols to design catalysts by computer. In this Account, we first review how thermodynamic properties such as redox potentials (E°), acidity constants (pKa), and hydride donor abilities (ΔGH(-)) form the basis for a framework for the systematic design of molecular catalysts for reactions that are critical for a secure energy future. We illustrate this for hydrogen evolution and oxidation, oxygen reduction, and CO conversion, and we give references to other instances where it has been successfully applied. The framework is amenable to quantum-chemical calculations and conducive to predictions by computer. We review how density functional theory allows the determination and prediction of these thermodynamic properties within an accuracy relevant to experimentalists (∼0.06 eV for redox potentials, ∼1 pKa unit for pKa values, and 1-2 kcal/mol for hydricities). Computation yielded correlations among thermodynamic properties as they reflect the electron population in the d shell of the metal center, thus substantiating empirical correlations used by experimentalists. These correlations point to the key role of redox potentials and other properties (pKa of the parent aminium for the proton-relay-based catalysts designed in our laboratory) that are easily accessible experimentally or computationally in reducing the parameter space for design. These properties suffice to fully determine free energies maps and profiles associated with catalytic cycles, i.e., the relative energies of intermediates. Their prediction puts us in a position to distinguish a priori between desirable and undesirable pathways and mechanisms. Efficient catalysts have flat free energy profiles that avoid high activation barriers due to low- and high-energy intermediates. The criterion of a flat energy profile can be mathematically resolved in a functional in the reduced parameter space that can be efficaciously calculated by means of the correlation expressions. Optimization of the functional permits the prediction by computer of design points for optimum catalysts. Specifically, the optimization yields the values of the thermodynamic properties for efficient (high rate and low overpotential) catalysts. We are on the verge of design of molecular electrocatalysts by computer. Future efforts must focus on identifying actual ligands that possess these properties. We believe that this can also be achieved through computation, using Taft-like relationships linking molecular composition and structure with electron-donating ability and steric effects. We note also that the approach adopted here of using free energy maps to decipher catalytic pathways and mechanisms does not account for kinetic barriers associated with elementary steps along the catalytic pathway, which may make thermodynamically accessible intermediates kinetically inaccessible. Such an extension of the approach will require further computations that, however, can take advantage of Polanyi-like linear free energy relationships linking activation barriers and reaction free energies.

Amino acid modified Ni catalyst exhibits reversible H2 oxidation/production over a broad pH range at elevated temperatures.

Hydrogenases interconvert H2 and protons at high rates and with high energy efficiencies, providing inspiration for the development of molecular catalysts. Studies designed to determine how the protein scaffold can influence a catalytically active site have led to the synthesis of amino acid derivatives of [Ni(P2(R)N2(R'))2](2+) complexes, [Ni(P2(Cy)N2(Amino acid))2](2+) (CyAA). It is shown that these CyAA derivatives can catalyze fully reversible H2 production/oxidation at rates approaching those of hydrogenase enzymes. The reversibility is achieved in acidic aqueous solutions (pH = 0-6), 1 atm 25% H2/Ar, and elevated temperatures (tested from 298 to 348 K) for the glycine (CyGly), arginine (CyArg), and arginine methyl ester (CyArgOMe) derivatives. As expected for a reversible process, the catalytic activity is dependent upon H2 and proton concentrations. CyArg is significantly faster in both directions (∼300 s(-1) H2 production and 20 s(-1) H2 oxidation; pH = 1, 348 K, 1 atm 25% H2/Ar) than the other two derivatives. The slower turnover frequencies for CyArgOMe (35 s(-1) production and 7 s(-1) oxidation under the same conditions) compared with CyArg suggests an important role for the COOH group during catalysis. That CyArg is faster than CyGly (3 s(-1) production and 4 s(-1) oxidation) suggests that the additional structural features imparted by the guanidinium groups facilitate fast and reversible H2 addition/release. These observations demonstrate that outer coordination sphere amino acids work in synergy with the active site and can play an important role for synthetic molecular electrocatalysts, as has been observed for the protein scaffold of redox active enzymes.

Heterolytic cleavage of hydrogen by an iron hydrogenase model: an Fe-H⋠⋠⋠H-N dihydrogen bond characterized by neutron diffraction.

Hydrogenase enzymes in nature use hydrogen as a fuel, but the heterolytic cleavage of H-H bonds cannot be readily observed in enzymes. Here we show that an iron complex with pendant amines in the diphosphine ligand cleaves hydrogen heterolytically. The product has a strong Fe-H⋅⋅⋅H-N dihydrogen bond. The structure was determined by single-crystal neutron diffraction, and has a remarkably short H⋅⋅⋅H distance of 1.489(10) Šbetween the protic N-H(δ+) and hydridic Fe-H(δ-) part. The structural data for [Cp(C5F4N)FeH(P(tBu)2N(tBu)2H)](+) provide a glimpse of how the H-H bond is oxidized or generated in hydrogenase enzymes. These results now provide a full picture for the first time, illustrating structures and reactivity of the dihydrogen complex and the product of the heterolytic cleavage of H2 in a functional model of the active site of the [FeFe] hydrogenase enzyme.

Development of molecular electrocatalysts for energy storage.

Molecular electrocatalysts can play an important role in energy storage and utilization reactions needed for intermittent renewable energy sources. This manuscript describes three general themes that our laboratories have found useful in the development of molecular electrocatalysts for reduction of CO2 to CO and for H2 oxidation and production. The first theme involves a conceptual partitioning of catalysts into first, second, and outer coordination spheres. This is illustrated with the design of electrocatalysts for CO2 reduction to CO using first and second coordination spheres and for H2 production catalysts using all three coordination spheres. The second theme focuses on the development of thermodynamic models that can be used to design catalysts to avoid high- and low-energy intermediates. In this research, new approaches to the measurement of thermodynamic hydride donor and acceptor abilities of transition-metal complexes were developed. Combining this information with other thermodynamic information such as pKa values and redox potentials led to more complete thermodynamic descriptions of transition-metal hydride, dihydride, and related species. Relationships extracted from this information were then used to develop models that are powerful tools for predicting and understanding the relative free energies of intermediates in catalytic reactions. The third theme is control of proton movement during electrochemical fuel generation and utilization reactions. This research involves the incorporation of pendant amines in the second coordination sphere that can facilitate H-H bond heterolysis and heteroformation, intra- and intermolecular proton-transfer steps, and coupling of proton- and electron-transfer steps. Studies also indicate an important role for the outer coordination sphere in the delivery of protons to the second coordination sphere. Understanding these proton-transfer reactions and their associated energy barriers is key to the design of faster and more efficient molecular electrocatalysts for energy storage.

Thermochemical and mechanistic studies of electrocatalytic hydrogen production by cobalt complexes containing pendant amines.

Two cobalt(tetraphosphine) complexes [Co(P(nC-PPh2)2N(Ph)2)(CH3CN)](BF4)2 with a tetradentate phosphine ligand (P(nC-PPh2)2N(Ph)2 = 1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5-diaza-3,7-diphosphacyclooctane; alkyl = (CH2)2, n = 2 (L2); (CH2)3, n = 3 (L3)) have been studied for electrocatalytic hydrogen production using 1:1 [(DMF)H](+):DMF. A turnover frequency (TOF) of 980 s(-1) with an overpotential at Ecat/2 of 1210 mV was measured for [Co(II)(L2)(CH3CN)](2+), and a TOF of 980 s(-1) with an overpotential at Ecat/2 of 930 mV was measured for [Co(II)(L3)(CH3CN)](2+). Addition of water increases the TOF of [Co(II)(L2)(CH3CN)](2+) to 18,000 s(-1). The catalytic wave for each of these complexes occurs at the reduction potential of the corresponding HCo(III) complex. Comprehensive thermochemical studies of [Co(II)(L2)(CH3CN)](2+) and [Co(II)(L3)(CH3CN)](2+) and species derived from them by addition/removal of protons/electrons were carried out using values measured experimentally and calculated using density functional theory (DFT). Notably, HCo(I)(L2) and HCo(I)(L3) were found to be remarkably strong hydride donors, with HCo(I)(L2) being a better hydride donor than BH4(-). Mechanistic studies of these catalysts reveal that H2 formation can occur by protonation of a HCo(II) intermediate, and that the pendant amines of these complexes facilitate proton delivery to the cobalt center. The rate-limiting step for catalysis is a net intramolecular isomerization of the protonated pendant amine from the nonproductive exoisomer to the productive endo isomer.

Synthesis and electrochemical studies of cobalt(III) monohydride complexes containing pendant amines.

Two new tetraphosphine ligands, P(nC-PPh2)2N(Ph)2 (1,5-diphenyl-3,7-bis((diphenylphosphino)alkyl)-1,5-diaza-3,7-diphosphacyclooctane; alkyl = (CH2)2, n = 2 (L2); (CH2)3, n = 3 (L3)), have been synthesized. Coordination of these ligands to cobalt affords the complexes [Co(II)(L2)(CH3CN)](2+) and [Co(II)(L3)(CH3CN)](2+), which are reduced by KC8 to afford [Co(I)(L2)(CH3CN)](+) and [Co(I)(L3)(CH3CN)](+). Protonation of the Co(I) complexes affords [HCo(III)(L2)(CH3CN)](2+) and [HCo(III)(L3)(CH3CN)](2+). The cyclic voltammetry of [HCo(III)(L2)(CH3CN)](2+), analyzed using digital simulation, is consistent with an ErCrEr reduction mechanism involving reversible acetonitrile dissociation from [HCo(II)(L2)(CH3CN)](+) and resulting in formation of HCo(I)(L2). Reduction of HCo(III) also results in cleavage of the H-Co bond from HCo(II) or HCo(I), leading to formation of the Co(I) complex [Co(I)(L2)(CH3CN)](+). Under voltammetric conditions, the reduced cobalt hydride reacts with a protic solvent impurity to generate H2 in a monometallic process involving two electrons per cobalt. In contrast, under bulk electrolysis conditions, H2 formation requires only one reducing equivalent per [HCo(III)(L2)(CH3CN)](2+), indicating a bimetallic route wherein two cobalt hydride complexes react to form 2 equiv of [Co(I)(L2)(CH3CN)](+) and 1 equiv of H2. These results indicate that both HCo(II) and HCo(I) can be formed under electrocatalytic conditions and should be considered as potential catalytic intermediates.