meso-Tetrakis(4-chlorophenyl)porphinato)manganese(III) tetracyanoethenide, [MnTClPP][TCNE], has been prepared and structurally characterized as the toluene and dichloromethane disolvates, and the magnetic and thermal properties of these solvates, as well as their corresponding desolvates, have been determined. The ditoluene solvate (1) has a triclinic unit cell: P1 h, a ) 10.171 (4) Å, b ) 10.189(3) Å, c ) 14.522 (3) Å, R ) 107.51(2)°, ) 85.58(2)°, γ ) 111.51(3)°, Z ) 1. The bis(dichloromethane) solvate (2) belongs to the monoclinic unit cell: P2 1 /n, a ) 9.894(2) Å, b ) 10.697(2) Å, c ) 23.560(5) Å, ) 101.34(2)°, Z ) 2. The cation is typical with average Mn-N distances of 2.012 Å for both the toluene and dichloromethane solvates. The bonding distances for both planar anions are characteristic of [TCNE] •-. Both solvates have an uniform linear chain (1-D) coordination-polymer structure comprised of alternating cations and anions. Each [TCNE] •-binds to two Mn III 's in a trans-µ-N-σ-bound manner with Mn-N spacings of 2.267 (1) and 2.276 Å (2). The Mn-N-C angles are 167.2 and 143.1°, while intrachain Mn‚‚‚Mn separations are 10.189 and 9.894 Å, and the dihedral angle between the MnN 4 and [TCNE] •-mean planes are 86.8 and 52.4°for 1 and 2, respectively. The ν CN absorptions for the toluene and dichloromethane solvates occur at 2201 m and 2160 s cm -1 and 2195 m and 2138 s cm -1 , respectively. Upon thermolysis at 175°C 1 desolvates to R-[MnTClPP][TCNE] with ν CN absorptions at 2201 m and 2159 s cm -1 . In contrast, desolvation of 1 in refluxing n-octane leads to -[MnTclPP][TCNE] with ν CN absorptions at 2190 m and 2132 s cm -1 . Upon facile desolvation of 2 to form γ-[MnTClPP][TCNE] the nitrile absorptions remain essentially unchanged (2195 m and 2137 s cm -1 ). For 1 and R the susceptibilities can be fit by the Curie-Weiss expression with Θ ) -60 K (T > 210 K) and -10 K (T > 250 K) and an effective Θ, Θ′ of +13 (50 < T < 120 K) and 29 K (60 < T < 160 K), respectively. Θ is not observed for the 2 or the -or γ-phase; however, Θ′ for the 2 and the -and γ-phases are 58, 92, and 86 K, respectively. The magnetic data are consistent with linear chain ferrimagnets comprised of antiferromagnetically coupled S ) 2 Mn III sites and S ) 1 / 2 [TCNE] •-sites with the antiferromagnetic intrachain coupling, J/k B (k B ) Boltzmann's constant) determined from fits to the Seiden expression, of -33, -160, -65, -267, and -265 K for the 1, 2, and R-, -, and γ-phases, respectively. Hysteresis with a coercive field of 5.8 kOe is observed for 1 at 2 K. Metamagnetic behavior below 5 K is observed for the 1, 2, and -and γ-phases with critical fields of 10, 27, 27, and 27 kOe, respectively. The ordering temperatures, T c , determined from the maxima in the ′(T) data taken at 10 Hz, are 8.8, 6.7, 11.1, 14.1, and 11.4 K for the phases 1, R, , 2, and γ, respectively. Desolvation of 1 and 2 increases the magnetic disorder and the magnetic coupling.

The ability to quickly store and deliver a significant amount of electrical energy at ultralow temperatures is critical for the energy‐efficient operation of high altitude aircraft and spacecraft, exploration of natural resources in polar regions and extreme altitudes, and astronomical observatories exposed to ultralow temperatures. Commercial high‐power electrochemical capacitors fail to operate at temperatures below –40 °C. According to conventional wisdom, mesoporous electrochemical capacitor electrodes with pores large enough to accommodate fully solvated ions are needed for sufficiently rapid ion transport at lower temperatures. It is demonstrated that strictly microporous carbon electrodes with much higher volumetric capacitance can be efficiently used at temperatures as low as –70 °C. The critical parameters, with respect to electrolyte properties and electrode porosity and microstructure, needed for achieving both rapid ion transport and efficient ion electroadsorption in porous carbons are discussed. As an example, the fabrication of an electrochemical capacitor with an outstanding performance at temperatures as low as –60 and –70 °C is demonstrated. At such low temperatures the capacitance of the synthesized electrodes is up to 123 F g−1 (≈76 F cm−3), which is 50–100% higher than that of the most common commercial electrochemical capacitor electrode at room temperature. At –60 °C selected cells based on ≈0.2 mm electrodes exhibited characteristic charge–discharge time constants of less than 9 s, which is faster than the majority of commercial devices at room temperature. The achieved combination of high energy and power densities at such ultralow temperatures is unprecedented and extremely promising for the advancement of energy storage systems.

Radioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power £5.1 W/kg. A higher specific power would result in more onboard power for the same RTG mass, or less RTG mass for the same onboard power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb 14 MnSb 11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermomechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.

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A correlation between the orientation of [TCNE] •-(TCNE ) tetracyanoethylene) bound to a [Mn III -(por)] + (por ) substituted meso-tetraphenylporphyrin) and the magnitude of magnetic coupling for a series of previously prepared [Mn(por)][TCNE]‚2PhMe linear-chain molecule-based ferrimagnets has been identified. The tetraphenylporphyrin (H 2 TPP), tetrakis(4-chlorophenyl)porphyrin (H 2 TClPP), tetrakis(4-methoxyphenyl)-porphyrin (H 2 TOMePP), tetrakis(2-fluorophenyl)porphyrin (H 2 TFPP), and tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (H 2 TP′P) ligands have all been utilized. Previous structural determinations as the ditoluene solvates indicate that the Mn-N distance varies ∼2.6%, while the Mn-(N-C) TCNE bond angle varies by as much as 25.2% from the mean values over this series of compounds. Hence the overlap between the [TCNE] •-π* SOMO and the Mn III SOMO d orbitals plays a significant role in controlling the magnetic properties. From molecular orbital overlap considerations, as determined from semiempirical INDO/SCF calculations, the expected d π -π* (d π ) d xz , d yz ) overlap is not as important as the σ-d z 2 -π* overlap between Mn III and the [TCNE] •-. Furthermore, the greater the deviation from 90°for the dihedral angle between the mean MnN 4 [Mn(por)] + plane and the [TCNE] •-mean plane increases the σ-d z 2 /p z overlap between Mn III and the [TCNE] •-leading to an increased intrachain coupling as the angle is decreased. An increase in the T min (the temperature at which the minima in the temperature dependence of the moment occurs) is observed as this angle becomes more acute, reflecting the stronger magnetic coupling. This suggests systems with smaller Mn(por) + /[TCNE] •-dihedral and Mn-(N-C) TCNE bond angles should have enhanced intrachain magnetic coupling, J intra , leading to higher T c 's. Pressure may force such systems to have reduced angles and also lead to higher T c 's.