Studies of Cobalt-Mediated Electrocatalytic CO_2 Reduction Using a Redox-Active Ligand

The cobalt complex [Co^(III)N_4H(Br)_2]+ (N_4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(7),2,11,13,15-pentaene) was used for electrocatalytic CO_2 reduction in wet MeCN with a glassy carbon working electrode. When water was employed as the proton source (10 M in MeCN), CO was produced (f_(CO)= 45% ± 6.4) near the Co^(I/0) redox couple for [Co^(III)N_4H(Br)_2]+ (E_(1/2) = −1.88 V FeCp_2^(+/0)) with simultaneous H_2 evolution (f_(H2)= 30% ± 7.8). Moreover, we successfully demonstrated that the catalytically active species is homogeneous through the use of control experiments and XPS studies of the working glassy-carbon electrodes. As determined by cyclic voltammetry, CO_2 catalysis occurred near the formal CoI/0redox couple, and attempts were made to isolate the triply reduced compound (“[Co^0N_4H]”). Instead, the doubly reduced (“Co^I”) compounds [CoN4] and [CoN_4H(MeCN)]+ were isolated and characterized by X-ray crystallography. Their molecular structures prompted DFT studies to illuminate details regarding their electronic structure. The results indicate that reducing equivalents are stored on the ligand, implicating redox noninnocence in the ligands for H_2 evolution and CO_2 reduction electrocatalysis

Poster Abstract: Crane Charades: Behavior Identification via Backpack Mounted Sensor Platforms

The Whooping Crane is an endangered species native to North America and there are approximately 575 in existence. There have been recent efforts to provide ecologists with a tool to study the multifaceted behavior of the endangered species. Like many species, cranes display distinctly identifiable movements while being threatened, acting territorial, migrating, or preening. The preliminary experiments described in this poster provide evidence that sensor data presented by a novel sensing platform, the CraneTracker, can be used to identify crane behaviors on-board. With the ability to identify these behaviors, ecologists will have a more granular insight on what occurs during a crane’s life on a daily basis

Poster Abstract: Crane Charades: Behavior Identification via Backpack Mounted Sensor Platforms

The Whooping Crane is an endangered species native to North America and there are approximately 575 in existence. There have been recent efforts to provide ecologists with a tool to study the multifaceted behavior of the endangered species. Like many species, cranes display distinctly identifiable movements while being threatened, acting territorial, migrating, or preening. The preliminary experiments described in this poster provide evidence that sensor data presented by a novel sensing platform, the CraneTracker, can be used to identify crane behaviors on-board. With the ability to identify these behaviors, ecologists will have a more granular insight on what occurs during a crane’s life on a daily basis

Metal complexes with varying intramolecular hydrogen bonding networks

Alfred Werner described the attributes of the primary and secondary coordination spheres in his development of coordination chemistry. To examine the effects of the secondary coordination sphere on coordination chemistry, a series of tripodal ligands containing differing numbers of hydrogen bond (H-bond) donors were used to examine the effects of H-bonds on Fe(II), Mn(II)–acetato, and Mn(III)–OH complexes. The ligands containing varying numbers of urea and amidate donors allowed for systematic changes in the secondary coordination spheres of the complexes. Two of the Fe(II) complexes that were isolated as their Bu4N+ salts formed dimers in the solid-state as determined by X-ray diffraction methods, which correlates with the number of H-bonds present in the complexes (i.e., dimerization is favored as the number of H-bond donors increases). Electron paramagnetic resonance (EPR) studies suggested that the dimeric structures persist in acetonitrile. The Mn(II) complexes were all isolated as their acetato adducts. Furthermore, the synthesis of a rare Mn(III)–OH complex via dioxygen activation was achieved that contains a single intramolecular H-bond; its physical properties are discussed within the context of other Mn(III)–OH complexes

Spectroscopic Confirmation of a Massive Red-Sequence-Selected Galaxy Cluster at z = 1.34 in the SpARCS-South Cluster Survey

The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a z'-passband imaging survey, consisting of deep (z' ~ 24 AB) observations made from both hemispheres using the CFHT 3.6m and CTIO 4m telescopes. The survey was designed with the primary aim of detecting galaxy clusters at z >~ 1. In tandem with pre-existing 3.6um observations from the Spitzer Space Telescope SWIRE Legacy Survey, SpARCS detects clusters using an infrared adaptation of the two-filter red-sequence cluster technique. The total effective area of the SpARCS cluster survey is 41.9 deg^2. In this paper, we provide an overview of the 13.6 deg^2 Southern CTIO/MOSAICII observations. The 28.3 deg^2 Northern CFHT/MegaCam observations are summarized in a companion paper by Muzzin et al. (2008). In this paper, we also report spectroscopic confirmation of SpARCS J003550-431224, a very rich galaxy cluster at z = 1.335, discovered in the ELAIS-S1 field. To date, this is the highest spectroscopically confirmed redshift for a galaxy cluster discovered using the red-sequence technique. Based on nine confirmed members, SpARCS J003550-431224 has a preliminary velocity dispersion of 1050 +/- 230 km/s. With its proven capability for efficient cluster detection, SpARCS is a demonstration that we have entered an era of large, homogeneously-selected z > 1 cluster surveys.Comment: 10 pages, 6 Figures, Submitted to the Ap

Spectroscopic Confirmation of Two Massive Red-Sequence-Selected Galaxy Clusters at z ~ 1.2 in the SpARCS-North Cluster Survey

The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a deep z'-band imaging survey covering the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) Legacy fields designed to create the first large homogeneously selected sample of massive clusters at z > 1 using an infrared adaptation of the cluster red-sequence method. We present an overview of the northern component of the survey which has been observed with Canada-France-Hawaii Telescope (CFHT)/MegaCam and covers 28.3 deg^2. The southern component of the survey was observed with Cerro Tololo Inter-American Observatory (CTIO)/MOSAICII, covers 13.6 deg^2, and is summarized in a companion paper by Wilson et al. We also present spectroscopic confirmation of two rich cluster candidates at z ~ 1.2. Based on Nod-and-Shuffle spectroscopy from GMOS-N on Gemini, there are 17 and 28 confirmed cluster members in SpARCS J163435+402151 and SpARCS J163852+403843 which have spectroscopic redshifts of 1.1798 and 1.1963, respectively. The clusters have velocity dispersions of 490 ± 140 km s^(–1) and 650 ± 160 km s^(–1), respectively, which imply masses (M_(200)) of (1.0 ± 0.9) × 10^(14) M_⊙ and (2.4 ± 1.8) × 10^(14) M_⊙. Confirmation of these candidates as bonafide massive clusters demonstrates that two-filter imaging is an effective, yet observationally efficient, method for selecting clusters at z > 1

Visible Light Sensitized CO2 Activation by the Tetraaza [Co^(II)N_4H(MeCN)]^(2+) Complex Investigated by FT-IR Spectroscopy and DFT Calculations

In situ FT-IR measurements and electronic structure calculations are reported for the reduction of CO_2 catalyzed by the macrocyclic complex [Co^(II)N_4H]^(2+) (N_4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]-heptadeca-1(17),2,11,13,15-pentaene). Beginning from the [Co^(II)N_4H]^(2+) resting state of the complex in wet acetonitrile solution, two different visible light sensitizers with substantially different reducing power are employed to access reduced states. Accessing reduced states of the complex with a [Ru(bpy)_3]^(2+) sensitizer yields an infrared band at 1670 cm^(–1) attributed to carboxylate, which is also observed for an authentic sample of the one-electron reduced complex [CoN_4H(MeCN)]^+ in CO_2 saturated acetonitrile solution. The results are interpreted based on calculations using the pure BP86 functional that correctly reproduces experimental geometries. Continuum solvation effects are also included. The calculations show that Co is reduced to Co^I in the first reduction, which is consistent with experimental d–d spectra of square Co(I) macrocycle complexes. The energy of the CO_2 adduct of the one-electron reduced catalyst complex is essentially the same as for [CoN_4H(MeCN)]^+, which implies that only a fraction of the latter forms an adduct with CO_2. By contrast, the calculations indicate a crucial role for redox noninnocence of the macrocyclic ligand in the doubly reduced state, [Co^I(N_4H) –•], and show that [Co^I(N_4H) –•] binds partially reduced CO_2 fairly strongly. Experimentally accessing [Co^I(N_4H) –•] with an Ir(bpy)_3 sensitizer with greater reducing power closes the catalytic cycle as FT-IR spectroscopy shows CO production. Use of isotopically substituted C^(18)O_2 also shows clear evidence for ^(18)O-substituted byproducts from CO_2 reduction to CO

Reduction of CO_2 by Pyridine Monoimine Molybdenum Carbonyl Complexes: Cooperative Metal–Ligand Binding of CO_2

[(^(Ar)PMI)Mo(CO)_4] complexes (PMI=pyridine monoimine; Ar=Ph, 2,6-di-iso-propylphenyl) were synthesized and their electrochemical properties were probed with cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC). The complexes undergo a reduction at more positive potentials than the related [(bipyridine)Mo(CO)_4] complex, which is ligand based according to IR-SEC and DFT data. To probe the reaction product in more detail, stoichiometric chemical reduction and subsequent treatment with CO_2 resulted in the formation of a new product that is assigned as a ligand-bound carboxylate, [(^(iPr2Ph)PMI)Mo(CO)_3(CO_2)]^(2-), by NMR spectroscopic methods. The CO_2 adduct [(^(iPr2Ph)PMI)Mo(CO)_3(CO_2)]^(2-) could not be isolated and fully characterized. However, the C_C coupling between the CO_2 molecule and the PDI ligand was confirmed by X-ray crystallographic characterization of one of the decomposition products of [(^(iPr2Ph)PMI)Mo(CO)_3(CO_2)])^(2-)

Sensing Through the Continent: Towards Monitoring Migratory Birds Using Cellular Sensor Networks

This paper presents CraneTracker, a novel sensor platform for monitoring migratory birds. The platform is designed to monitor Whooping Cranes, an endangered species that conducts an annual migration of 4, 000 km between southern Texas and north-central Canada. CraneTracker includes a rich set of sensors, a multi-modal radio, and power control circuitry for sustainable, continental-scale information delivery during migration. The need for large-scale connectivity motivates the use of cellular technology in low-cost sensor platforms augmented by a low-power transceiver for ad-hoc connectivity. This platform leads to a new class of cellular sensor networks (CSNs) for time-critical and mobile sensing applications. The CraneTracker is evaluated via field tests on Wild Turkeys, Siberian Cranes, and an on-going alpha deployment with wild Sandhill Cranes. Experimental evaluations demonstrate the potential of energy-harvesting CSNs for wildlife monitoring in large geographical areas, and reveal important insights into the movements and behaviors of migratory animals. In addition to benefiting ecological research, the developed platform is expected to extend the application domain of sensor networks and enable future research applications

Spectroscopic Confirmation of Three Red-sequence Selected Galaxy Clusters at z = 0.87, 1.16, and 1.21 from the SpARCS Survey

The Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) is a z'-passband imaging survey of the 50 deg^2 Spitzer SWIRE Legacy fields, designed with the primary aim of creating the first large, homogeneously selected sample of massive clusters at z > 1. SpARCS uses an infrared adaptation of the two-filter cluster red-sequence technique. In this paper, we report Keck/LRIS spectroscopic confirmation of two new exceptionally rich galaxy clusters, SpARCS J161315+564930 at z = 0.871 ± 0.002, with 14 high-confidence members and a rest-frame velocity dispersion of σ_v = 1230 ± 320 km s^(–1), and SpARCS J161641+554513 at z = 1.161 ± 0.003, with seven high-confidence members (including one active galactic nucleus) and a rest-frame velocity dispersion of σ_v = 950 ± 330 km s^(–1). We also report confirmation of a third new system, SpARCS J161037+552417 at z = 1.210 ± 0.002, with seven high-confidence members and a rest-frame velocity dispersion of σ v = 410 ± 300 km s^(–1). These three new spectroscopically confirmed clusters further demonstrate the efficiency and effectiveness of two-filter imaging for detecting bona fide galaxy clusters at high redshift. We conclude by demonstrating that prospects are good for the current generation of surveys aiming to estimate cluster redshifts and masses at z ≳ 1 directly from optical-infrared imaging