Low Ea Research Articles

An environmentally-benign NaNbO3 based perovskite antiferroelectric alternative to traditional lead-based counterparts

NaNbO3-based lead-free AFE R-phase ceramics with Pnma space group and nanoscale stripe domain exhibit completely reversible field induced AFE–FE phase transition, featuring a relatively low EA–F of ∼8 kV mm−1 and a large repeatable strain of ∼0.29%.

Water diffusion with temperature enabling predictions for sorption and transport behavior in thermoset materials

Water desorption kinetics for a number of epoxy materials (five amine and one anhydride cured), with glass transitions from below room temperature to 245 °C, were studied using thermogravimetry and near-infrared spectroscopy between ambient and 200 °C. Computational models based on 1D finite difference or 3D finite element Fickian diffusion processes were then applied to determine the underlying diffusivity. Classical Fickian diffusion with a constant D was sufficient to describe the water desorption behavior for all evaluated materials and conditions, with water induced swelling affecting the diffusion process no more than through small dimensional changes. The temperature dependence for diffusivity displayed mostly a single activation energy (Ea) between 44 and 62 kJ mol−1 for all materials except one, which showed a change from 75 kJ mol−1 below Tg (∼65 °C), to 53 kJ mol−1 above. The obtained diffusivities and their Ea were then used to predict and illustrate the sorption behavior for other geometries and temperatures. The trends for these materials were discussed within the existing theories for fractional free volume, effective crosslink density and chemical composition. Unexpectedly, this study shows that Tg has no or only limited influence on water diffusivity in contrast with the Cohen-Turnbull model. Water sorption (solubility in the material) is of similar magnitude independent of temperature (i.e. low Ea) as anticipated. Only a fraction of the water uptake was found to be associated with free volume utilization, with the majority of water resulting in material volume changes, which as a consequence means that dynamic water uptake and drying will result in changing stress conditions (expansion and contraction) for glassy thermosets even under ambient conditions.

Bimetallic palladium–iridium alloy nanoparticles as highly efficient and stable catalyst for the hydrogen evolution reaction

Addressed herein, a highly efficient, durable and uniformly dispersed activated carbon supported palladium–iridium nanomaterials (3.42 ± 0.34 nm) were reported for the first time as a catalyst in dimethylamine-borane dehydrogenation reaction at the room temperature. The activated carbon supported palladium-iridium nanosheet (Pd–Ir NPs) is obtained by a simple ultrasonic reduction method, and the fabricated nanocatalyst have been defined by Ultra-Violet-Visible (UV–VIS), Raman spectroscopy, X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). These newly prepared Pd–Ir nanocomposites were found to be highly efficient and stable for dehydrocoupling of dimethylamine borane. The catalytic activity of the Pd–Ir NPs was excellent by showing the one of the best catalytic activity with a very high turnover frequency (295.1 h−1) and low Ea value of 36.6 ± 2 kJ/mol for DMAB dehydrocoupling. Another important fact about the prepared catalyst is the reusability of the catalyst was very high and easily reused five times without any significant decrease in their catalytic performance. In the current work, the synthesize, characterization and the catalytic performance of the Pd–Ir nanoparticles for the dehydrogenation of the DMAB reaction will be discussed in detail.

Endocrine Effects of Relative Energy Deficiency in Sport.

The term Relative Energy Deficiency in Sport was introduced by the International Olympic Committee in 2014. It refers to the potential health and performance consequences of inadequate energy for sport, emphasizing that there are consequences of low energy availability (EA; typically defined as <30kcal·kg-1 fat-free mass·day-1) beyond the important and well-established female athlete triad, and that low EA affects populations other than women. As the prevalence and consequences of Relative Energy Deficiency in Sport become more apparent, it is important to understand the current knowledge of the hormonal changes that occur with decreased EA. This paper highlights endocrine changes that have been observed in female and male athletes with low EA. Where studies are not available in athletes, results of studies in low EA states, such as anorexia nervosa, are included. Dietary intake/appetite-regulating hormones, insulin and other glucose-regulating hormones, growth hormone and insulin-like growth factor 1, thyroid hormones, cortisol, and gonadal hormones are all discussed. The effects of low EA on body composition, metabolic rate, and bone in female and male athletes are presented, and we identify future directions to address knowledge gaps specific to athletes.

ZIF-67-derived Co3O4 rhombic dodecahedron as an efficient non-noble-metal catalyst for hydrogen generation from borohydride hydrolysis

Abstract As Co3O4 is one of the most attractive catalysts for H2 generation (HG) from NaBH4 hydrolysis, Co3O4 nanoparticle (NP)-immobilized composites are intensively developed for NaBH4 hydrolysis. Nevertheless, these Co3O4 composites involve complicated fabrication procedures and long preparation time. More importantly, these composites typically consist of a large fraction of “dead” weight of inactive substrates, causing these composites unnecessarily effective. Unlike immobilizing Co3O4 NPs on substrates, this study proposes a Co3O4 catalyst completely comprised of Co3O4 NPs which are framed but the entire Co3O4 catalyst can still exhibit porosity. To this end, a cobaltic zeolitic imidazolate framework (ZIF-67) with morphology of rhombic dodecahedron is adopted as a templated precursor, which is converted into Co3O4 rhombic dodecahedral (RD) granule. Because of cobaltic species and hierarchical structures of ZIF-67, the resulting Co3O4 RD granule can consist of densely packed Co3O4 NPs, but remain porous, making it a promising catalyst for NaBH4 hydrolysis. This ZIF-67 derived Co3O4 (ZIFCoO) exhibits a considerably higher catalytic activity than its precursors, ZIF-67 and carbonized ZIF-67, as well as the commercial Co3O4 NPs. While a higher dose of ZIFCoO facilitates NaBH4 hydrolysis to generate more H2, 500 mg/L of ZIFCoO is the optimal catalyst dose to obtain the highest HG rate. ZIFCoO also exhibits a relatively low Ea as 39.4 kJ/mol compared to most of the reported catalysts. ZIFCoO can be also reused for multiple cycles of HG efficiently. These features make ZIFCoO a conveniently-prepared and promising heterogeneous catalyst for H2 generation from NaBH4 hydrolysis.

Ruthenium supported on ZIF-67 as an enhanced catalyst for hydrogen generation from hydrolysis of sodium borohydride

H2 generation (HG) from NaBH4 hydrolysis represents as a safe, mild and convenient method for storing and releasing H2. As Ru is the most effective metal for catalyzing NaBH4 hydrolysis, continuous efforts are being made to find suitable supports for immobilizing Ru nanoparticles (NPs) to form heterogeneous Ru catalysts. Since NaBH4 hydrolysis typically occurs in water and at high temperature, an ideal support necessitates high stability in water, high surface area, hierarchical structures and even synergy with Ru. In this study, ZIF-67 is particularly selected as a catalytic active support for immobilizing Ru species because ZIF-67 has proven to be highly stable in water and also hierarchically consists of Co, another catalytic active component for HG from NaBH4 hydrolysis. Compared to ZIF-8, ZIF-67 is validated to catalyze NaBH4 hydrolysis for HG, making Ru/ZIF-67 an enhanced Ru-based catalyst. Ru/ZIF also exhibited a higher catalytic activity than the equivalent Ru species, suggesting that the supporting of Ru on ZIF-67 enhanced catalytic activities of Ru species. As the effect of Ru loading on Ru/ZIF was evaluated, a higher Ru loading significantly boosted catalytic activities by substantially reducing Ea. HG from Ru/ZIF-catalyzed hydrolysis of NaBH4 could be optimized in the presence of 7.5 wt% of NaOH to exhibit a low Ea of 36.4 kJ mol−1, which is much lower than most of reported Ru-based catalysts. In addition, Ru/ZIF can be also re-used with consistent catalytic activities without regeneration. These results validate that Ru/ZIF67 composite is a promising and effective catalyst for H2 production from NaBH4 hydrolysis.

Distinct bioenergetic signatures in particulate versus mineral-associated soil organic matter

Physical and chemical stabilization, environmental conditions, and organic matter composition all play vital roles in determining the persistence of soil organic matter (SOM). Fundamentally, SOM stability depends on the balance of microbial bioenergetics between the input of energy needed to decompose it (i.e., activation energy; Ea) and the net energy gained (i.e., energy density; ED) from its decomposition. This relationship is complicated in soils by chemical and physical protection mechanisms, which require additional energies to overcome for decomposition to occur. In this study, we analyze the bioenergetics of soil density fractions, which vary in their degrees of organic matter-mineral association, and show that the relationship of ED and Ea has the ability to provide information about relative differences in SOM chemical composition and stability. Our results demonstrate distinct bioenergetic signatures between particulate, light (free and occluded) fractions versus mineral-associated, heavy fractions isolated from soil samples collected at two depths from a climosequence along an elevation gradient in the Sierra Nevada, California. While there were no significant differences in ED and Ea within each fraction across climates, the light fractions (LF) were characterized by larger ED and Ea values, whereas the heavy fractions (HF) were characterized by smaller ED and Ea values. Combined with CHN analyses, we conclude that SOM in HF pools is likely comprised of relatively simple organic compounds that have long turnover rates because of chemical association with soil minerals, whereas the LF pools are comprised of more chemically complex molecules with low chemical reactivity and high Ea.

Highly efficient polymer supported monodisperse ruthenium-nickel nanocomposites for dehydrocoupling of dimethylamine borane

In the present study, highly effective and reusable monodisperse ruthenium–nickel (Ru-Ni) nanomaterials supported on poly(N-vinyl-2-pyrrolidone) (Ru-Ni@PVP) were synthesized (3.51 ± 0.38 nm) by a facile sodium-hydroxide-assisted reduction method; Ru and Ni reduction in PVP solution was accomplished. The prepared nanocomposites were characterized by TEM, HRTEM, XRD, and XPS and performed as a catalyst for dehydrocoupling of dimethylamine-borane (DMAB). It was found that Ru-Ni nanomaterials are one of the most active catalysts at low concentrations and temperature for dehydrocoupling of DMAB. This catalyst with its turnover frequency of 458.57 h−1 exhibits one of the best results among all the catalysts prepared in the literature for dehydrocoupling of DMAB. Significantly low Ea value (36.52 ± 3 kJ mol−1) was also found for dehydrocoupling of DMAB.

Characterization and polarization DRT analysis of a stable and highly active proton-conducting cathode

The development of high active cathode materials owning low activation energy (Ea) is the most critical core for protonic solid oxide fuel cells (P-SOFCs). Considering this challenge, we herein develop Ba0.9La0.1Co0.4Fe0.4Zr0.1Y0.1O3-δ-BaZr0.1Ce0.7Y0.2O3-δ (BLCFZY-BZCY) composite as a new proton conducting cathode for P-SOFCs. Anode supported single cells with BLCFZY-BZCY cathode show remarkable performance and low electrode Ea of 83.41 kJ mol−1. High power densities of 752 and 206 mW cm−2 are achieved at 700 and 500 °C, respectively, while corresponding electrode interfacial polarization resistances (Rp) are 0.08 and 1.2 Ω cm2. Interestingly, the electrode polarization processes with a high resolution based on the impedance spectra data were further analyzed using the distribution function of relaxation time (DRT). Three same polarization peaks (P1, P2, P3) meaning three rate-limiting steps are existed in the DRT curves with different temperature, where P3 resulting from the cathode-electrolyte interfacial resistance with oxygen species involved reactions is the dominant rate-limiting step with a proportion of over 49.6% while the anode-electrolyte interfacial resistance corresponding to P1 has almost no increase, from 0.03 Ωcm2 to 0.09 Ωcm2. The experimental results demonstrate BLCFZY-BZCY composite can be a promising proton conducting cathode for P-SOFCs.

Low Energy Availability Associated With Lower BMD And Bone Stress Injury Site In Female Athletes

Low energy availability (LEA) is a risk factor for impaired bone health and bone stress injury (BSI). Additionally, those with BSI at trabecular-rich bone sites are at higher risk for low BMD vs. those with BSI at only cortical-rich sites. PURPOSE: To evaluate the association of LEA with BMD and site of BSI in female athletes. METHODS: 1000 female athletes (ages 15-30 years) presenting to a sports medicine clinic completed a 400+ question survey covering topics related to relative energy deficiency in sport (RED-S), including female athlete triad risk factors and athletic activity. Comprehensive chart review was completed to identify athletes with history of BSI and available dual energy x-ray absorptiometry (DXA). LEA was defined as meeting ≥ 1 criterion: self-reported history of eating disorder/disordered eating (ED/DE), high score on the Brief Eating Disorder in Athletes Questionnaire (BEDA-Q), and/or high score on the Eating Disorder Screen for Primary Care (ESP). Athletes with BSI of the pelvis, femoral neck, sacrum, and/or calcaneus were categorized into the trabecular-rich BSI group; all others were categorized into the cortical-rich BSI group. Associations between EA status, BSI location, and DXA were assessed by chi-squared or t-test analysis (p<0.05). RESULTS: Of the 1000 patients surveyed, 126 had a history of both BSI and available DXA. Of these patients, 53.2% had LEA. Patients with LEA had lower BMD Z-scores than those with normal EA at the lumbar spine (-0.92±1.06 vs. -0.49±0.98, p=0.022), total hip (-0.27±0.75 vs. 0.29±0.77, p=0.009), and femoral neck (-0.34±0.87 vs. 0.23±0.97, p=0.028). Patients with ≥ 1 trabecular BSI accounted for 21.4% of the sample. In the trabecular-rich BSI group, 70.4% had LEA, while 48.5% of those in the cortical-rich group had LEA (p=0.043). Additionally, those with trabecular-rich BSI had lower BMD than the cortical-rich BSI group at the lumbar spine (-1.19±1.10 vs. -0.58±0.99, p=0.015), but not at other sites assessed by DXA. CONCLUSIONS: Our findings support the well-established relationship between LEA and impaired BMD. We also found that trabecular-rich BSI is associated with low EA and independently associated with low BMD. Therefore, trabecular BSI may serve as a clinical indicator for further bone health evaluation and assessment for LEA, including ED/DE.

Management of the female athlete triad.

The female athlete triad (FAT) is defined by the American College of Sports Medicine (ACSM) as low energy availability (low EA), functional hypothalamic amenorrhoea and osteoporosis. In low EA, lutein dysfunction first develops, followed by anovulation and, subsequently, oligomenorrhea, leading to amenorrhea. Moreover, low estradiol concentrations due to amenorrhea decrease bone mineral density (BMD). In athletes with one of the factors of FAT, the risk of a stress fracture is 2.4-4.9 times higher and may increase the risk of fracture throughout the lifespan. Low EA is the starting point of FAT, and the FAT concept emphasizes the importance of energy intake that is commensurate with exercise energy expenditure in athletes. In amenorrheic athletes who undergo gynecological examination, it is important to appropriately evaluate whether the cause is low EA and to review exercise energy expenditure and energy intake. It remains difficult even for experts to calculate available energy using the ACSM definition formula when evaluating energy deficiency. Moreover, performing early FAT screening during teenage years and cooperation between the department of obstetrics and gynecology and sports dietitians are also issues. The aim of this paper is to review the management of FAT from the viewpoint of gynecologists.

Thermodynamics characterization and potential textile applications of Trichoderma longibrachiatum KT693225 xylanase

Abstract Our study was a trial to participate in solving two main problems namely, environmental pollution resulting from accumulation and bad disposal of agro-industrial wastes, and high cost of industrial xylanase enzyme production. This was achieved through successful xylanase production by solid-state fermentation of low cost disposable agricultural wastes by marine fungal isolate Trichoderma longibrachiatum KT693225. The highest xylanase production 7.13 ± 0.11 U ml−1 was obtained utilizing rice straw (RS) waste after 7days of fermentation. Xylanase was purified by fractional precipitation with ethanol causing 4.24-fold purification. The 75% ethanol fraction was rich in cellulase, pectinase and α-amylase enzymes beside xylanase. The maximal xylanase activity was obtained at 60 °C, pH 5% and 2.5% xylan concentration. The Km and Vmax were calculated to be 20 mg ml−1 and 20 µmol min−1 ml−1, respectively. The thermostability of T.longibrachiatum KT693225 xylanase was indicated by low Ea (activation energy)and high Ed (energy of denaturation). High T1/2 (half life), D-value (decimal reduction time), ΔH° (enthalpy), ΔG° (free energy) and low Kd (denaturation rate constant), ΔS° (entropy) values at 70 °C emphasized high T.longibrachiatum KT693225 xylanase stability. T.longibrachiatum KT693225 xylanase showed high effectiveness at several textile wet-processing stages including desizing, bioscouring and biofinishing of cellulosic fabrics without adding any additives. These findings in this study have great implications for the future applications of xylanases.

Within-day energy deficiency and reproductive function in female endurance athletes.

We aimed to estimate and compare within-day energy balance (WDEB) in athletes with eumenorrhea and menstrual dysfunction (MD) with similar 24-hour energy availability/energy balance (EA/EB). Furthermore, to investigate whether within-day energy deficiency is associated with resting metabolic rate (RMR), body composition, S-cortisol, estradiol, T3 , and fasting blood glucose. We reanalyzed 7-day dietary intake and energy expenditure data in 25 elite endurance athletes with eumenorrhea (n=10) and MD (n=15) from a group of 45 subjects where those with disordered eating behaviors (n=11), MD not related to low EA (n=5), and low dietary record validity (n=4) had been excluded. Besides gynecological examination and disordered eating evaluation, the protocol included RMR measurement; assessment of body composition by dual-energy X-ray absorptiometry, blood plasma analysis, and calculation of WDEB in 1-hour intervals. Subjects with MD spent more hours in a catabolic state compared to eumenorrheic athletes; WDEB<0kcal: 23.0hour (20.8-23.4) vs 21.1hour (4.7-22.3), P=.048; WDEB<-300kcal: 21.8hour (17.8-22.4) vs 17.6hour (3.9-20.9), P=.043, although similar 24-hour EA: 35.6 (11.6) vs 41.3 (12.7) kcal/kg FFM/d, (P=.269), and EB: -659 (551) vs -313 (596) kcal/d, (P=.160). Hours with WDEB <0kcal and <-300kcal were inversely associated with RMRratio (r=-.487, P=.013, r=-.472, P=.018), and estradiol (r=-.433, P=.034, r=-.516, P=.009), and positively associated with cortisol (r=.442, P=.027, r=.463, P=.019). In conclusion, although similar 24-hour EA/EB, the reanalysis revealed that MD athletes spent more time in a catabolic state compared to eumenorrheic athletes. Within-day energy deficiency was associated with clinical markers of metabolic disturbances.

Plasma–surface interaction at atmospheric pressure: A case study of polystyrene etching and surface modification by Ar/O2 plasma jet

In this paper, the authors studied atmospheric pressure plasma–surface interactions using a well-characterized radio-frequency Ar/O2 plasma jet with polystyrene (PS) polymer films in controlled gas environments as a model system. A number of plasma processing parameters, such as the treatment distance, environmental gas composition, and substrate temperature, were investigated by evaluating both the changes in the thickness and the surface chemical composition of PS after treatment. The authors found that the polymer average etch rate decayed exponentially with the nozzle–surface distance, whereas the surface oxygen composition increased to a maximum and then decreased. Both the exponential decay constant and the oxidation maximum depended on the composition of the gaseous environment which introduced changes in the density of reactive species. The authors previously reported a linear relationship between measured average etch rates and estimated atomic O flux based on measured gas phase atomic O density. In this work, the authors provided additional insights into the kinetics of surface reaction processes. The authors measured the substrate temperature dependence of the PS etch rate and found that the apparent activation energy (Ea) of the PS etching reaction was in the range of 0.10–0.13 eV. Higher values were obtained with a greater nozzle-to-surface distance. This relatively low Ea value suggests that additional energetic plasma species might be involved in the etching reactions, which is also consistent with the different behavior of etching and surface oxidation modification reactions at the polymer surface as the treatment distance is varied.

Highly monodisperse RuCo nanoparticles decorated on functionalized multiwalled carbon nanotube with the highest observed catalytic activity in the dehydrogenation of dimethylamine−borane

Herein we report the discovery of a superior dimethylamine−borane dehydrogenation catalyst, more active than the prior best heterogeneous catalyst (Celik B.; Yıldız Y.; Sert H.; Erken E.; Koskun Y.; and Sen F.; RSC Advances 2016, 6, 24097–24102) reported to date for the dehydrogenation of dimethylamine−borane. The new catalyst system consists of well dispersed ruthenium-cobalt nanomaterials decorated on functionalized multiwalled carbon nanotube (3.72 ± 0.37 nm) prepared by the use of the ultrasonic double reduction method. The morphology and structure composition of catalytically effective, recyclable and reproducible catalysts were fully characterized by using different analytical techniques such as UV–Vis, XPS, TEM, XRD and HR-TEM-EELS analyses. This catalyst showed best ever catalytic activity with a very high turnover frequency (775.28 h−1) and low Ea value of 13.72 ± 2 kJ/mol for DMAB dehydrocoupling in the ambient conditions yielding 100% of the cyclic product (Me2NBH2)2 at room temperature. Besides, RuCo@ƒ-MWCNT catalyst exhibits great reusability, high catalytic performance and excellent durability for dimethylamine-borane dehydrogenation reaction.

Highly efficient catalytic dehydrogenation of dimethyl ammonia borane via monodisperse palladium–nickel alloy nanoparticles assembled on PEDOT

Addressed herein, the synthesis of the monodisperse poly(3,4-ethylenedioxythiophene)(PEDOT) supported palladium–nickel nanomaterials (3.32 ± 0.36 nm) and their applications as a catalyst in dimethylamine-borane (DMAB) dehydrogenation is outlined. Microwave assistance procedure was used in preparation of nanomaterials where palladium and cobalt cations were reduced in PEDOT solution (Pd–Ni@PEDOT) in microwave conditions. The characterization of the nanocatalyst was performed by using UV-VIS, XRD, XPS, TEM and HR-TEM-EELS analyses. The Pd–Ni@PEDOT NPs were found to be highly effective and stable for the dehydrogenation of DMAB. The catalytic activity of Pd–Ni@PEDOT was one of the highest one among the all prepared catalysts in literature even at lower temperatures and concentrations, yielding to give high turnover frequency (451.2 h−1) and low Ea (50.78 ± 2 kJ/mol) for dehydrocoupling of DMAB.

Polymer-graphene hybride decorated Pt nanoparticles as highly efficient and reusable catalyst for the dehydrogenation of dimethylamine–borane at room temperature

Addressed herein, we report a reduced graphene oxide (rGO) nanosheet coupled with polyaniline (PANI) for platinum (Pt) nanoparticles as supporting materials. The PANI-coupled rGO (PANI@rGO) nanosheet is prepared by a simple one-step chemical assembly strategy, and Pt nanoparticles are anchored on the support of PANI@rGO through the reaction of PANI with a platinum salt. The designed PANI efficiently exposes the surface of rGO sheets and stabilizes metal nanoparticles. Consequently, the Pt@PANI-rGO catalyst exhibits good reusability, durability and high catalytic performance for dimethylamine–borane dehydrogenation reaction. The structure morphology and properties of Pt@PANI-rGO NPs were characterized by using several different techniques such as UV–Vis, XPS, TEM, XRD and HR-TEM-EDX analyses. This newly prepared catalyst can be reused again at low concentrations and temperature. They showed a high turnover frequency (42.94 h−1) and low Ea value of 15.1 ± 2 kJ/mol for DMAB dehydrocoupling in the ambient conditions. The proposed nano architecture offers a new pathway to promote the performances of rGO in various applications; moreover, this work provides a powerful and universal synthetic strategy for such an architecture.

PH Dependence of Chitosan Enzymolysis.

As a means of making chitosan more useful in biotechnological applications, it was hydrolyzed using pepsin, chitosanase and α-amylase. The enzymolysis behavior of these enzymes was further systematically studied for its effectiveness in the production of low-molecular-weight chitosans (LMWCs) and other derivatives. The study showed that these enzymes depend on ion hydronium (H3O+), thus on pH with a pH dependence fitting R2 value of 0.99. In y = 1.484 + 0.114, the equation of pH dependence, when increases by one, y () increases by 1.484. From the temperature dependence study, the activation energy (Ea) and pre-exponential factor (A) were almost identical for two of the enzymes, but a considerable difference was observed in comparison with the third enzyme. Chitosanase and pepsin had nearly identical Ea, but α-amylase was significantly lower. This serves as evidence that the hydrolysis reaction of α-amylase relies on low-barrier hydrogen bonds (LBHBs), which explains its low Ea in actual conditions. The confirmation of this phenomenon was further derived from a similarly considerable difference in the order magnitudes of A between α-amylase and the other two enzymes, which was more than five. Variation of the rate constants of the enzymatic hydrolysis of chitosan with temperature follows the Arrhenius equation.

Octahedral iron(II) complexes with pyridyl triazine and bipyridine ligands – synthesis, computational studies, mechanisms and kinetics with 1,10-phenanthroline and 2,2′,6,2″-terpyridine

[Bis(3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)(2,2′-bipyridine)iron(II)], [Fe(PDT)2(bpy)]2+ (1), [bis(3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine)(2,2′-bipyridine)iron(II)], [Fe(PPDT)2(bpy)]2+ (2), [bis(2,2′-bipyridine)(3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine)iron(II)], [Fe(PDT)(bpy)2]2+ (3), and [bis(2,2′-bipyridine)(3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine)iron(II)], [Fe(PPDT)(bpy)2]2+ (4) have been synthesized and characterized. Substitution of the triazine and bipyridine ligands from the complexes by nucleophiles (nu), namely 1,10-phenanthroline (phen) and 2,2′,6,2″-terpyridine (terpy) was studied in a sodium acetate-acetic acid buffer over the pH range 3–6 at 25, 35, and 45°C under pseudo-first order conditions. Reactions are first order in the concentration of complexes 1–4. The reaction rates increase with increasing [nu] and pH whereas ionic strength has no effect on the rate. Straight-line plots with positive slopes are observed when the kobs values are plotted against [nu] or 1/[H+]. The substitution reactions proceed by dissociative as well as associative paths and the latter path is predominant. Observed low Ea values and negative ΔS# values support the dominance of the associative path. Phenyl groups on the triazine ring modulate the reactivity of the complexes. The π-electron cloud on the phenyl rings stabilizes the charge on metal center by inductive donation of electrons toward the metal center, resulting in a decrease in reactivity of the complex and the order is 1 < 2 < 3 < 4. Density functional theory (DFT) calculations also support the interpretations drawn from the kinetic data.

High temperature ionic conduction mediated by ionic liquid incorporated within the metal-organic framework UiO-67(Zr)

IL@MOF (IL=ionic liquid; MOF=metal organic framework) as a new type hybrid ionic conductor has attracted research interest. Ionic liquids incorporated within MOFs not only promote the ionic conductivity of ILs, but also mediate the working temperature. In our report, 1-Ethyl-3-methylimidazolium Chloride (EMIMCl) was introduced into the pores of UiO-67(Zr) MOF by taking simple strategy basing on capillary action through specific grinding and diffusing in heating process. The working temperature of EMIMCl@UiO-67 is up to 200°C. And it shows high ionic conductivity (1.67×10−3S·cm−1 at 200°C). The activation energy was estimated to be 0.37eV. It is noteworthy that the hybrid material can be regarded as a fast-ion conductor based on the value of high conduction and low Ea. The high-temperature and humidity-independent ion conduction as well as low activation energy make this material potentially useful for electrochemical devices.