The high-spin dichloro Mn 2+ and Fe 2+ complexes of 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (1) and 4, 10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (2) provide durable new compounds of these elements for important fundamental studies and applications. The compounds are especially noteable for their exceptional kinetic stabilities and redox activity. The X-ray crystal structures of all four complexes demonstrate that the ligands enforce a distorted octahedral geometry on the metals with two cis sites occupied by labile chloride ligands. Magnetic measurements reveal that all are high spin with typical magnetic moments. Cyclic voltammetry of the complexes shows reversible redox processes at +0.110 and +0.038 V (versus SHE) for the Fe 3+ /Fe 2+ couples of Fe(1)Cl 2 and Fe(2)Cl 2 , respectively, while the Mn 3+ /Mn 2+ and Mn 4+ /Mn 3+ couples were observed at +0.585 and +1.343 V, and +0.466 and +1.232 V for the complexes Mn(1)Cl 2 and Mn(2)Cl 2 , respectively. Mn 2+ (1) was found to react with H 2 O 2 and other oxidizing agents to produce the Mn 4+ (1) complex. The catalytic efficacy of Mn 4+ (1) in aqueous solution has been assessed in the epoxidation reaction of carbamazepine and hydrogen abstraction reaction with 1,4-cyclohexadiene. The complex has been found to be a selective catalyst, exhibiting moderate catalytic activity in oxygen transfer, but significantly more effective catalytic activity in hydrogen abstraction reactions.

The demand for renewable energy sources worldwide has gained tremendous research attention over the past decades. Technologies such as wind and solar have been widely researched and reported in the literature. However, economical use of these technologies has not been widespread due partly to cost and the inability for service during of-source periods. To make these technologies more competitive, research into energy storage systems has intensified over the last few decades. The idea is to devise an energy storage system that allows for storage of electricity during lean hours at a relatively cheaper value and delivery later. Energy storage and delivery technologies such as supercapacitors can store and deliver energy at a very fast rate, offering high current in a short duration. The past decade has witnessed a rapid growth in research and development in supercapacitor technology. Several electrochemical properties of the electrode material and electrolyte have been reported in the literature. Supercapacitor electrode materials such as carbon and carbon-based materials have received increasing attention because of their high specific surface area, good electrical conductivity and excellent stability in harsh environments etc. In recent years, there has been an increasing interest in biomass-derived activated carbons as an electrode material for supercapacitor applications. The development of an alternative supercapacitor electrode material from biowaste serves two main purposes: (1) It helps with waste disposal; converting waste to a useful product, and (2) it provides an economic argument for the substantiality of supercapacitor technology. This article reviews recent developments in carbon and carbon-based materials derived from biowaste for supercapacitor technology. A comparison between the various storage mechanisms and electrochemical performance of electrodes derived from biowaste is presented.Sustainability 2019, 11, 414 2 of 22 renewable energy sources such as solar energy, geothermal energy, wind energy, biofuels, etc., while electrochemical energy storage devices such as supercapacitors, rechargeable batteries, etc. have also attracted significant research [9][10][11]. It is not an overstatement to say that successful development of any renewable energy source (e.g., windmills and solar cells), hybrid and electric vehicles and smart grids depend significantly upon the availability of a suitable energy storage system. A considerable amount of literature has been published on the use of supercapacitors as a viable storage device for renewable energy. Over 20,000 articles, books etc. were published in 2017, a higher number of research work is projected for 2018 (data from google scholar). There has been a geometric increase in the research published since the year 2000. Since supercapacitors were first experimented in 1957 by engineers at General Electric, they have found commercial applications in portable electronics, transportation and aerospace industry [12,13]. These applications of supercapacitors ...

High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ~510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ~1.55 F/cm2 at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ~65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices.

In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.

Polymerizations in 1,2-dichlorobenzene solutions containing 0.33 volume fraction of styrene or methyl methacrylate (MMA) and relative weights of monomer/C 60/azo(bisisobutyronitrile) (AIBN) of 100:1.00:1.12 at 75 °C form high molecular weight materials in which all of the C60 is incorporated covalently. To understand the structures of the polymers and their mechanism of formation, samples were isolated after low conversion of monomer and analyzed. Molar size exclusion chromatograms from UV detection of fullerenes, differential refractive index detection of the mass of the polymer, and differential viscometry detection of the specific solution viscosity of the polymer show that the fullerene reacts rapidly, and both polystyrene/C 60 and PMMA/C60 products isolated after low conversion of monomer contain many fullerenes per molecule. Lower intrinsic viscosity and higher absolute molecular weight of the fullerene-containing polymers compared with linear polystyrenes at equal retention time show that the polymer structures are branched. Elemental analyses, NMR spectra, and size exclusion chromatograms show that the C 60 content is higher and the polymer chain lengths are shorter in the low-conversion polystyrene/C60 than in the low-conversion PMMA/C60. C60 itself polymerizes when initiated by AIBN. NMR analyses of polymers formed by initiation with AIBN-R-13 C show that in both polystyrene/C60 and PMMA/C60 at low conversion 62-72% of the 2-cyano-2-propyl groups are bound to polymer chain ends, and 28-38% are bound to fullerenes. Neither low molar mass AIBN/C60 adducts nor the polymers at any degree of conversion initiate further polymerization of monomer. Thus, the formation of 2-cyano-2-propyl to fullerene and polymer to fullerene carbon-carbon bonds is irreversible. After high conversion both polystyrene/C60 and PMMA/C60 contain much linear polymer. The average number of fullerene units per molecule decreases with increasing reaction time, and after complete reaction of monomer, all polystyrene/ C60 samples and some PMMA/C60 samples still have an average of more than one fullerene unit per macromolecule at the high end of the molecular weight distribution. Fullerene radicals were detected by ESR spectroscopy in all of the solid polymers recovered at low and high conversion. Evaluation of a radical chain mechanism for the copolymerizations using estimated rate constants for the microscopic steps shows that the fullerene must exist as clusters early in the polymerization, and that the clusters break down to macromolecules containing smaller numbers of fullerene units as the polymerization continues.