The cationic magnesium moiety of magnesium organohaloaluminate complexes, relevant to rechargeable Mg battery electrolytes, typically takes the thermodynamically favourable dinuclear [Mg2Cl3](+) form in the solid-state. We now report that judicious choice of Lewis donor allows the deliberate synthesis and isolation of the hitherto only postulated mononuclear [MgCl](+) and trinuclear [Mg3Cl5](+) modifications, forming a comparable series with a common aluminate anion [(Dipp)(Me3Si)NAlCl3](-). By pre-forming the Al-N bond prior to introduction of the Mg source, a consistently reproducible protocol is reported. Usage of the green solvent 2-methyltetrahydrofuran in place of THF in the context of Mg/Al battery electrolyte type complexes is also promoted.
Previously it was reported that activation of (t)Bu2Zn by [(TMEDA)Na(μ-dpa)]2 led to tert-butylation of benzophenone at the challenging para-position, where the sodium amide functions as a metalloligand towards (t)Bu2Zn manifested in crystalline [{(TMEDA)Na(dpa)}2Zn(t)Bu2] (TMEDA is N,N,N',N'-tetramethylethylenediamine, dpa is 2,2'-dipyridylamide). Here we find altering the Lewis donor or alkali metal within the metalloligand dictates the reaction outcome, exhibiting a strong influence on alkylation yields and reaction selectivity. Varying the former led to the synthesis of three novel complexes, [(PMDETA)Na(dpa)]2, [(TMDAE)Na(dpa)]2, and [(H6-TREN)Na(dpa)], characterised through combined structural, spectroscopic and theoretical studies [where PMDETA is N,N,N',N'',N''-pentamethyldiethylenetriamine, TMDAE is N,N,N',N'-tetramethyldiaminoethylether and H6-TREN is N',N'-bis(2-aminoethyl)ethane-1,2-diamine]. Each new sodium amide can function as a metalloligand to generate a co-complex with (t)Bu2Zn. Reacting these new co-complexes with benzophenone proved solvent dependent with yields in THF much lower than those in hexane. Most interestingly, sub-stoichiometric amounts of the metalloligands [(TMEDA)Na(dpa)]2 and [(PMEDTA)Na(dpa)]2 with 1 : 1, (t)Bu2Zn-benzophenone mixtures produced good yields of the challenging 1,6-tert-butyl addition product in hexane (52% and 53% respectively). Although exchanging Na for Li gave similar reaction yields, the regioselectivity was significantly compromised; whereas the K system was completely unreactive. Replacing (t)Bu2Zn with (Me3SiCH2)2Zn shut down the alkylation of benzophenone; in contrast, (t)BuLi generates only the reduction product, benzhydrol. Zincation of the parent amine dpa(H) generated the crystalline product [Zn(dpa)2], as structurally elucidated through X-ray crystallography and theoretical calculations. Although the reaction mechanism for the alkylation of benzophenone remains unclear, incorporation of the radical scavenger TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical) into the reaction system completely inhibits benzophenone alkylation.
The hybrid/ electric vehicle (H/EV) market is very dependent on battery models. Battery models inform cell and battery pack design, critical in online battery management systems and can be used as predictive tools to maximise the lifetime of a battery pack. Battery models require parameterization, through experimentation. Temperature affects every aspect of a battery's operation and must therefore be closely controlled throughout all battery experiments. Today, the private-sector prefers climate chambers for experimental thermal control. However, evidence suggests that climate chambers are unable to adequately control the surface temperature of a battery under test. In this study, laboratory apparatus is introduced that controls the temperature of any exposed surface of a battery through conduction. Pulse discharge tests, temperature step change tests and driving cycle tests are used to compare the performance of this conductive temperature control apparatus (CTCA) against a climate chamber across a range of scenarios. The CTCA outperforms the climate chamber in all tests. In CTCA testing, the rate of heat removal from the cell is increased by two orders of magnitude. The CTCA eliminates error due to cell surface temperature rise, which is inherent to climate chamber testing due to insufficient heat removal rates from a cell under test. The CTCA can reduce the time taken to conduct entropic parameterization of a cell by almost 10 days, a 70% reduction in the presented case. Presently, the H/EV industry's reliance on climate chambers is impacting the accuracy of all battery models. The industry must move away from the flawed concept of convective cooling during battery parameterization.
Previous studies of different solvates of 2‐methylpyridyllithium (2‐picolyllithium) have uncovered electronic structures corresponding to aza‐allyl and enamido resonance forms of the metallated pyridine‐based compounds. Here, we report the synthesis and characterization of [2‐CH2Li(THF)2C5H4N], a new THF solvate. X‐ray crystallographic studies reveal a dimeric arrangement featuring a non‐planar eight‐membered [NCCLi]2 ring, in which the primary cation‐anion interaction is between the central Li atom and the C atom of the deprotonated methyl group [length, 2.285(2) Å], suggesting a new carbanionic resonance structure for this 2‐picolyllithium series. The significant carbanionic character of [2‐CH2Li(THF)2C5H4N] was confirmed by gas‐phase DFT calculations [B3LYP/6‐311+G(d)] with the calculated electron density interrogated by means of quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. For comparison these computational analyses were also performed on the literature structures of [2‐CH2Li(2‐Picoline)C5H4N] and [2‐CH2Li(PMDETA)C5H4N]. In a reactivity study, [2‐CH2Li(THF)2C5H4N] was found to undergo nucleophilic addition to pyridine to generate dipyridylmethane in a good yield.
The active species in magnesium electrolytes is regularly assigned as being the thermodynamically stable dinuclear [Mg2Cl3]+ cation. By deliberately targeting other implicated aggregates, their effect on Mg-ion battery performance is easily ascertained.
The terahertz absorption spectra of sodium magnesium chlorophyllin (Chl-Mg-Na) and sodium copper chlorophyllin (Cu-Chl), two major members of the chlorophyll derivative family, have been measured in the range 0.2−3.0 THz (6.6−100 cm -1 ), at room temperature. Additionally, surface-enhanced Raman scattering spectroscopy was used to supplement data in the higher frequency range. The capability of terahertz spectroscopy for quantitative characterization of Chl-Mg-Na intermolecular vibrations was investigated and the sensitivity of the 1.82-THz feature with degree of hydration by changes in the molecular environment was examined. For Cu-Chl derivative, a broad feature was observed around 1.8 THz which currently hinders clear Cu-Chl identification and quantification.
The low-frequency (terahertz) vibrational spectroscopy of two chlorophyll species, Chl-𝑎 and one of its magnesium derivatives (Chl-Mg-Na), has been investigated experimentally. The combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy has enabled a broad frequency range to be covered (0.2 to 18 THz). For Chl-Mg-Na, the terahertz spectra show clear and well-marked features at 1.44, 1.64, and 1.83 THz dominated by intermolecular interactions. The frequency dependent refractive index and absorption coefficient of Chl-Mg-Na were determined using the Fit@TDS software. Below 1.0 THz, a refractive index of 2.09 was measured. In order to acquire further understanding of the observed vibrational modes, a detailed study of the temperature dependence of the line positions of the lowest modes in Chl-Mg-Na was performed. As the temperature is increased from 88 K to 298 K, the feature at 1.83 THz experiences a notable red shift of frequency and line shape broadening, whereas the feature at 1.44 THz shows little change. These results suggest that the 1.83 THz feature is dominated by intermolecular motions occurring over the crystalline unit cell of the Chl-Mg-Na molecular crystal. Finally, terahertz time-domain was used to acquire the spectra of an ornamental plant bearing yellow-green variegated leaves (ivy, Aureomarginata variety), the yellow sectors having lower chlorophyll content compared to green sectors. In dehydrated green tissue, the chlorophyll molecules showed well-marked intermolecular vibrational modes at 1.85 THz, indicating that chlorophyll molecules are prone to pack with an ordered molecular arrangement. These results demonstrate the potential application of THz spectroscopy in agricultural sciences.
The low-frequency (terahertz) vibrational spectroscopy of two chlorophyll species, Chl-𝑎 and one of its magnesium derivatives (Chl-Mg-Na), has been investigated experimentally. The combination of terahertz time-domain spectroscopy and Fourier transform infrared spectroscopy has enabled a broad frequency range to be covered (0.2 to 18 THz). For Chl-Mg-Na, the terahertz spectra show clear and well-marked features at 1.44, 1.64, and 1.83 THz dominated by intermolecular interactions. The frequency dependent refractive index and absorption coe cient of Chl-Mg-Na were determined using the Fit@TDS software.Below 1.0 THz, a refractive index of 2.09 was measured. In order to acquire further understanding of the observed vibrational modes, a detailed study of the temperature dependence of the line positions of the lowest modes in Chl-Mg-Na was performed. As the temperature is increased from 88 K to 298 K, the feature at 1.83 THz experiences a notable red shift of frequency and line shape broadening, whereas the feature at 1.44 THz shows little change. These results suggest that the 1.83 THz feature is dominated by intermolecular motions occurring over the crystalline unit cell of the Chl-Mg-Na molecular crystal. Finally, terahertz time-domain was used to acquire the spectra of an ornamental plant bearing yellow-green variegated leaves (ivy, Aureomarginata variety), the yellow sectors having lower chlorophyll content compared to green sectors. In dehydrated green tissue, the chlorophyll molecules showed well-marked intermolecular vibrational modes at 1.85 THz, indicating that chlorophyll molecules are prone to pack with an ordered molecular arrangement. These results demonstrate the potential application of THz spectroscopy in agricultural sciences.
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