Name: 1,3,5-triphenylbenzene and corannulene as electron receptors for lithium solvated electron solutions
Uploaded: 2016-10-10T13:00:00.000+00:00
Duration: 6 min 56 s
Description: Watch this Scientific Journal Video about 1,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions at JoVE.com

The authors acknowledge funding from the Singapore Ministry of Education Tier 2 Research Fund (project MOE2013-T2-2-002) for this project.

1. Preparation Procedure for 1,3,5-Triphenylbenzene (1)
<ol>
	<li>Place a mixture of acetophenone (4.0 g, 33.3 mmol) and 100 ml of absolute ethanol into a round bottom three neck 250 ml flask equipped with magnetic stirrer, reflux condenser, nitrogen inlet, bubbler, dropping funnel and thermometer. Add silicon tetrachloride (11.9 g, 8.0 ml, 70.2 mmol, 2.1 eq.) to the mixture in one portion at 0 &#176;C under nitrogen using the dropping funnel.</li>
	<li>Observe the evolution of gaseous hydrogen chloride for 10 min. Then stir the reaction mixture at 40 &#176;C for 20 hr.</li>
	<li>Cool down the reaction mixture to 23 &#176;C and pour in 200 g of water mixed with ice (1:1 mass ratio).</li>
	<li>Extract the resulting mixture with dichloromethane (2 x 100 ml) using an extraction funnel.</li>
	<li>Wash the combined extracts once with saturated NaCl solution (100 ml), and dry over 15 g of anhydrous MgSO4. Filter the liquid part off and then concentrate using a rotary evaporator.</li>
	<li>Purify the product via recrystallization from ethanol (dissolution in minimal amount of ethanol followed by partial evaporation of the solvent, keeping at 6 &#176;C overnight, and rapid filtration) to obtain 2.2 g (yield 63%) of 1,3,5-triphenylbenzene (1) as pale yellow crystals. 
	Note: 1H-NMR (400 MHz, CDCl3): &#948;= 7.41 (m, 3H), 7.50 (m, 6H), 7.72 (d, 6H, J = 7.33Hz), 7.80 (s, 3H). 13C-NMR (400 MHz, CDCl3): &#948;= 125.21, 127.39, 127.57, 128.88, 141.18, 142.38.</li>
</ol>
2. LiSES Prepared with 1,3,5-Triphenylbenzene
<ol>
	<li>Preparation of 1,3,5-triphenylbenzene-based LiSES 
	NOTE: 1,3,5-triphenylbenzene used in this paper was synthesized as per procedure described above. The 1,3,5-triphenylbenzene -based LiSES are denoted by LixTPB(THF)24.7 where x denotes the Li:PAH molar ratio and TPB denotes 1,3,5-triphenylbenzene. Prepare LixTPB(THF)24.7 inside an argon-filled glovebox at ambient temperature via the following steps:
	<ol>
		<li>Measure out well defined quantities of metallic Li, THF and TPB separately inside the glovebox to achieve the target molar composition of LixTPB(THF)24.7 for x = 1, 2, 3, and 4. Use 41.6 mg, 83.3 mg, 124.9 mg, 166.6 mg of Li for x = 1, 2, 3 and 4 respectively.</li>
		<li>For each of the four LiSES samples to be prepared, dissolve 1.84 g of TPB in 12 ml of THF inside four separate glass bottles to form 12 ml of colorless solutions of TPB(THF)24.7 for each bottle. Use a 0.5 M 1,3,5-triphenylbenzene in all the solutions.</li>
		<li>Add the weighed metallic Li foils to the four bottles and seal the bottles with Parafilm.</li>
		<li>Stir the mixture in each bottle overnight using a glass-coated magnetic stirrer to ensure the complete dissolution of metallic Li.</li>
	</ol>
	</li>
	<li>Conductivity Measurements
	<ol>
		<li>Carry out all conductivity measurements using a standard conductivity cell probe based on the four-electrode technique. Attach the cell probe to a meter. The probe has a secondary function to measure the solution&#39;s temperature at the same time and display both conductivity and temperature measurements.</li>
		<li>Prior to measurements, calibrate the meter using 50 ml of standard 0.01 M aqueous KCl solution provided by the conductivity probe&#39;s manufacturer outside the glovebox.</li>
		<li>Carry out all the conductivity measurements for 1,3,5-triphenylbenzene-based LiSES, LixTPB(THF)24.7 for x = 1, 2, 3, 4 inside the glovebox.</li>
		<li>For each of these LiSES, pour out the sample into a short glass cylinder and immerse the probe into the solution. Record the conductivity measurement over a period of one to two hours till each sample returns to an ambient temperature. The time taken for each sample to return to ambient temperature is ~1-2 hr. The probe will remain immersed in the sample for the entire duration of conductivity measurement.</li>
	</ol>
	</li>
</ol>
3. Corannulene
<ol>
	<li>Preparation of corannulene-based LiSES 
	NOTE: The corannulene used in this paper was synthesized at the School of Physical and Mathematical Sciences, NTU using a multistep literature procedure.9 The corannulene-based LiSES are denoted by LixCor(THF)247 where x denotes the Li:PAH molar ratio and Cor denotes the corannulene. Prepare LixCor(THF)247 inside an argon-filled glovebox at ambient temperature via the following steps:
	<ol>
		<li>Measure out well defined quantities of metallic Li, THF and Cor separately inside the glovebox to achieve the target molar composition of LixCor(THF)247 for x = 1, 2, 3, 4 and 5. Use 4.2 mg, 8.3 mg, 12.5 mg, 16.6 mg and 20.8 mg of Li for x = 1, 2, 3, 4 and 5 respectively.</li>
		<li>Next, for each of the five LiSES samples (x = 1, 2, 3, 4 and 5) to be prepared, dissolve 0.15 g of Cor in 12 ml of THF inside five separate glass bottles to form 12 ml of colorless solution of Cor(THF)247 in each bottle. Use a corannulene concentration of 0.05 M).</li>
		<li>Next, add the weighed metallic Li foils to the five bottles of Cor(THF)247 and seal the bottles with Parafilm.</li>
		<li>Stir the mixture in each bottle overnight using a glass-coated magnetic stirrer to ensure the complete dissolution of the metallic lithium.</li>
	</ol>
	</li>
	<li>Conductivity Measurements
	<ol>
		<li>For conductivity versus temperature measurements, remove each of the five bottles containing LixCor(THF)247 for x = 1, 2, 3, 4 and 5 individually from the glovebox, wrap it with an additional layer of para-film and immerse it inside an insulated Styrofoam container filled with dry ice. 
		NOTE: The LiSES samples did not come into contact with either moisture or oxygen while outside the glovebox because the bottles were sealed.</li>
		<li>Cool each bottle down to about 10 &#176;C by keeping each bottle immersed in the dry ice for about 30 min before being transferred back into the glovebox for conductivity measurements.</li>
		<li>Purge the ante-chamber of the glovebox at least 5 times for each cooled sample to ensure that no traces of water of condensation accompany the bottle back into the glovebox.</li>
		<li>Similar to the manner in which conductivity versus temperature measurements were collected for naphthalene-based LiSES samples1, measure the conductivity of LixCor(THF)247 (x = 1, 2, 3, 4, 5) over a period of one to two hours till each sample returned to ambient temperature. The probe will remain immersed in the sample for the entire duration of conductivity measurement.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Tan, K. S., Yazami, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical-Chemical+and+Electrochemical+Studies+of+the+Lithium+Naphthalenide+Anolyte.">Physical-Chemical and Electrochemical Studies of the Lithium Naphthalenide Anolyte.</a> Electrochim Acta. 180, 629-635 (2015).</li><li>Tan, K. S., Grimsdale, A. C., Yazami, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+Characterisation+of+Biphenyl-Based+Lithium+Solvated+Electrons+Solutions.">Synthesis and Characterisation of Biphenyl-Based Lithium Solvated Electrons Solutions.</a> J Phys Chem B. 116, 9056-9060 (2012).</li><li>Rinaldi, A., Tan, K. S., Wijaya, O., Wang, Y., Yazami, R., Menictas, C., Skyllas-Kazacos, M., Lim, T. M., Hughes, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ch.+11.">Ch. 11.</a> Advances in batteries for large- and medium-scale energy storage applications in power systems and electric vehicles. , (2014).</li><li>Wang, Y., Tan, K. S., Yazami, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Materials Challenges In Alternative &amp; Renewable Energy (MCARE 2014). , (2014).</li><li>Yazami, R., Tan, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> in 8th annual Li Battery Power. , (2012).</li><li>Yazami, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hybrid+Electrochemical+Generator+With+A+Soluble+Anode.">Hybrid Electrochemical Generator With A Soluble Anode.</a> US patent. , (2010).</li><li>Yazami, R., Tan, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid+Metal+Battery.">Liquid Metal Battery.</a> US patent. , (2015).</li><li>Lim, Z. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+assessment+of+new+cyclopenta-2,4-dienone+derivatives+for+energy+storage+applications.">Synthesis and assessment of new cyclopenta-2,4-dienone derivatives for energy storage applications.</a> Synthetic Met. 200, 85-90 (2015).</li><li>Butterfield, A. M., Gilomen, B., Siegel, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kilogram-Scale+Production+of+Corannulene.">Kilogram-Scale Production of Corannulene.</a> Org. Process Res. Dev. 16, 664-676 (2012).</li><li>Elmorsy, S. S., Pelter, A., Smith, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+direct+production+of+tri-+and+hexa-substituted+benzenes+from+ketones+under+mild+conditions.">The direct production of tri- and hexa-substituted benzenes from ketones under mild conditions.</a> Tetrahedron Lett. 32, 4175-4176 (1991).</li><li>Zabula, A. V., Filatov, A. S., Spisak, S. N., Rogachev, A. Y., Petrukhina, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Main+Group+Metal+Sandwich:+Five+Lithium+Cations+Jammed+Between+Two+Corannulene+Tetraanion+Decks.">A Main Group Metal Sandwich: Five Lithium Cations Jammed Between Two Corannulene Tetraanion Decks.</a> Science. 333, 1008-1011 (2011).</li></ol>

The authors have nothing to disclose.

For the 1,3,5-triphenylbenzene-based LiSES, a sample with a light color shows that it has a low concentration of solvated electrons. LixTPB(THF)24.7 (for x = 1, 2, 3, 4) demonstrates a behavior in its conductivity versus x similar to that seen for LiSES made from biphenyl and naphthalene1, 2.There is an initial increase in conductivity with increase of Li:PAH ratio from 1 to 2 and a subsequent decrease in conductivity upon further increasing the molar ratio to 3 and 4, with conductivity value of Li4TPB(THF)24.7 even lower than for Li1TPB(THF)24.7.
From Figure 4, it can be seen that the relationship between &#963; and T is linear for all five samples and each profile has a negative slope. This indicates that LixCor(THF)247 exhibits a metallic behavior similar to that of both the biphenyl and the naphthalene-based LiSES1,2. The relationship between &#963; (&#181;S/cm) and T(K) for LixCor(THF)247 can be expressed as:
&#963;(x,T) = &#963;0[1-&#945;(T-T0)] (1)
where &#963;0 is conductivity at T0 and &#945; is the temperature coefficient and both terms are &#34;x&#34; dependent. The respective data for all five profiles are presented in Table 2.
The low conductivities of all five samples, measured in the range of 102 &#956;S/cm instead of mS/cm can be attributed to the fact that the LixCor(THF)247 solutions are all very dilute in THF as compared to the LiSES that the authors have studied earlier based on biphenyl and naphthalene.
As LiSES are both oxygen and moisture sensitive, the most critical steps in experiments with LiSES are as follows. 1) First, ensure that both processes for preparing LiSES and conductivity measurements are performed completely within the argon-filled glovebox to prevent contact of the LiSES with moisture and oxygen. This is because contact with either moisture or oxygen will lead to the LiSES being neutralized to form hydroxides and oxides of Li which are useless for solvating the electrons and detrimental to the conductivity. 2) Second, ensure that each bottled sample of the LiSES is not in contact with either moisture or oxygen when it is taken out for cooling in dry ice.
A modification of the existing method for stirring solutions is the use of a custom-made borosilicate glass-coated magnetic stirrer for preparing LiSES instead of using Teflon-coated (C2F4)n ones that are readily available in the market. The (C2F4)n reacts upon contact with metallic Li and LiSES to give C and LiF. Visually, the stirrer will have turned black (carbon is left on the stirrer) and the F ions will have gone into the LiSES as LiF and affect the conductivity measurements. As carbon is porous, further use of the now-carbon coated stirrer to stir future LiSES will introduce iron (from the magnet) into the solutions.
The usage of customized glass-coated stirrers for LiSES preparation instead of Teflon-coated stirrers is very significant. Although this may be overlooked as a simple process, black-colored Teflon sticks or Teflon-coated stirrers turning black after use can easily be mistaken as having been made dirty by the stirring process without the realization that 1) LiF is formed with F being stripped from the polymer by the LiSES and mixed into the solution and 2) that the black color actually indicates an irreversible damage of the polymer coating turning into carbon. Hence the existing method of using Teflon coated stirrers does not work for LiSES preparation.
Troubleshooting the technique for cooling LiSES is done to ensure that each of the LiSES sample is not frozen solid during cooling but instead just cooled to about 10 &#176;C in the dry ice. Otherwise, time will be wasted waiting for frozen LiSES to defrost in the glovebox. This is achieved by trial and error in timing (optimum: 30 min) since the bottles cannot be unsealed for temperature measurement of the LiSES outside the glovebox.
There are three limitations for the LiSES experiments. Firstly, as the LiSES are both sensitive to both moisture and oxygen, preparations of the LiSES samples and conductivity measurements must be restricted to the argon environment inside a glovebox. Most conductivity measuring devices available are bulky and cannot fit inside a glovebox. The manufacturers of these devices assume that the user&#39;s samples are not air-sensitive. Hence the conductivity measurements described in this paper were made using a handheld meter and probe. Secondly, as described in the protocol section for the cooling experiment, the samples were cooled to about 10&#160;&#176;C before being transferred back inside the glovebox. This temperature is an estimate because the bottles cannot be unsealed outside the glovebox for temperature measurements. Thirdly, the limitation of experimenting with the Cor PAH is that it is very difficult to obtain a large amount of Cor in lab conditions unlike biphenyl or naphthalene. This will rule out the possibility of obtaining a larger quantity to prepare a higher concentration solution of Cor in THF.
The future application of the techniques described here is to study the physical and electrochemical properties of LiSES prepared using other types of PAHs so as to select the ideal candidate as lithium solvated electrons solution anode material for room temperature refillable LiSES batteries.

Lithium solvated electron solutions (LiSES) prepared using simple two-ring polyaromatic hydrocarbons (PAH) such as biphenyl and naphthalene can potentially be utilized as liquid anodes in refuelable lithium cells1-7. In the LiSES, these simple PAH molecules served as the electron receptors for solvated electrons from dissolved metallic lithium.
Progressing from these two-ring systems, the authors have since then carried out conductivity measurement studies on LiSES which are prepared using more complex PAHs, starting with the group of cyclopenta-2,4-dienone derivatives8. These PAHs include larger PAHs (&#62;two benzene rings) and PAHs with substituents incorporated into their aromatic rings. A larger PAH molecule with more than two rings is expected to accommodate more lithium atoms per PAH molecule than either biphenyl or naphthalene thus resulting in LiSES with a higher energy density. The objective of introducing substituents into PAHs is to make the PAH accept electrons more readily and become more stable as polyanions in LiSES.
As part of ongoing efforts to develop LiSES with higher energy density, this paper will report on the characterization of LiSES prepared from corannulene made by the literature procedure9 as well as 1,3,5-triphenylbenzene, TPB synthesized by a slightly modified literature 10. 1,3,5-triphenylbenzene, as shown in Figure 1(1), can be classified as a biphenyl derivative with two additional phenyl rings at positions 3 and 5 of the same ring. Since this molecule has four benzene rings, it should uptake 4 atoms of Li per molecule, which is more than for biphenyl (maximum 2.5 mole equivalents of Li per PAH in 0.5 M solution) and naphthalene (&#60;2.5 mole equivalents of lithium per molecule).
Corannulene is a five-ring PAH arranged into a bowl shape as shown in Figure 1(2). Zabula et al.11 have demonstrated the feasibility of dissolving metallic lithium in a solution of corannulene/tetrahydrofuran (THF) to form a solution with five Li+ ions sandwiched between two stable tetraanions of corannulene.
<img alt="Figure 1" src="/files/ftp_upload/54366/54366fig1.jpg" /> 
Figure 1: The molecular structures of 1,3,5-triphenylbenzene (1) and corannulene (2). 1,3,5-triphenylbenzene is classified as a biphenyl derivative with two additional phenyl rings at positions 3 and 5 of the same ring. Corannulene is a five-ring PAH with its five benzene rings arranged into a bowl shape. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54366/54366fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Thus, both 1,3,5-triphenylbenzene and corannulene are potential candidates for high energy density LiSES.

<table><tbody><tr><td>Tetrahydrofuran Anhydrous, &amp;#8805;99.9%, Inhibitor-free</td><td>Sigma Aldrich</td><td>401757-100ML</td><td></td></tr><tr><td>Lithium Foil&amp;nbsp;</td><td>Alfa Aesar</td><td>010769.14</td><td></td></tr><tr><td>Cond 3310 Conductivity Meter</td><td>WTW</td><td>Not Applicable</td><td></td></tr><tr><td>1,3,5-triphenylbenzene</td><td></td><td></td><td>Synthesized from acetophenone according to procedure described in literature</td></tr><tr><td>Silicon tetrachloride</td><td>Sigma Aldrich</td><td>215120-100G</td><td></td></tr><tr><td>acetophenone</td><td>TCI</td><td>A0061-500g</td><td></td></tr><tr><td>Ethanol</td><td>Merck Millipore</td><td>1.00983.2511</td><td></td></tr><tr><td>Corannulene</td><td></td><td></td><td>Synthesized by literature procedure</td></tr></tbody></table>

1,3,5-triphenylbenzene and corannulene as electron receptors for lithium solvated electron solutions

The authors report on conductivity studies carried out on lithium solvated electron solutions (LiSES) prepared using two types of polyaromatic hydrocarbons (PAH), namely 1,3,5-triphenylbenzene and corannulene, as electron receptors. The solid PAHs were first dissolved in tetrahydrofuran (THF) to form a solution. Metallic lithium was then dissolved into these PAH/THF solutions to yield either blue or greenish blue solutions, colors which are indicative of the presence of solvated electrons. Conductivity measurements at ambient temperature carried out on 1,3,5-triphenylbenzene-based LiSES, denoted by LixTPB(THF)24.7 (x = 1, 2, 3, 4), showed an increase of conductivity with increase of Li:PAH ratio from x = 1 to 2. However, the conductivity gradually decreased upon further increasing the ratio. Indeed the conductivity of LixTPB(THF)24.7 for x = 4 is even lower than for x = 1. Such behavior is similar to that of the previously reported LiSES prepared from biphenyl and naphthalene. Conductivity versus temperature measurements on corannulene-based LiSES, denoted by LixCor(THF)247 (x = 1, 2, 3, 4, 5), showed linear relationships with negative slopes, indicating a metallic behavior similar to biphenyl and naphthalene-based LiSES.

Reaction between various amounts of lithium and mixtures of 1,3,5-triphenylbenzene with THF gives greenish blue or deep blue colored solutions as shown in Figure 2. A light color indicates that the particular sample of LiSES has a low concentration of solvated electrons. 1,3,5-triphenylbenzene demonstrates increase of conductivity with increase of Li:PAH ratio from 1 to 2 in 0.5 M THF solution (Table 1). However, conductivity value gradually decreases upon further increasing the molar ratio. The conductivity value for Li:PAH = 4 is even lower than for Li:PAH = 1. This behavior is similar to that seen for LiSES made from biphenyl and naphthalene1, 2.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Mole eq. of Li per 1</td>
			<td>1</td>
			<td>2</td>
			<td>3</td>
			<td>4</td>
		</tr>
		<tr>
			<td>Conductivity (mS/cm)</td>
			<td>1.69</td>
			<td>2.04</td>
			<td>1.62</td>
			<td>1.33</td>
		</tr>
	</tbody>
</table>
Table 1: The conductivity readings (in mS/cm) for Li SES prepared using LixTPB(THF)24.7 (x = 1, 2, 3, 4). LixTPB(THF)24.7 means 0.5 M solution of TPB in THF with different Li mole ratio.
<img alt="Figure 2" src="/files/ftp_upload/54366/54366fig2.jpg" /> 
Figure 2: After all the metallic Li had dissolved in TPB(THF)24.7, the colors of LixTPB(THF)24.7 ranged from light blue (for x = 1) to very dark blue (for x = 4). A lighter color indicates a lower concentration of solvated electrons in the TPB(THF)24.7 solution. This photograph shows a solution of Li3TPB(THF)24.7 for x = 3 which has a dark blue color. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54366/54366fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
For the Cor-based LiSES, when all the metallic Li (for x = 1, 2, 3, 4, 5) had dissolved in Cor(THF)247 , the colors of the LiSES ranged from green (for x = 1) to very dark green (for x = 5). As the concentration of Cor in THF was very low (0.05 M), the volume expansion of the solution versus the amount of Cor dissolved in THF was negligible. The color change of the solution as metallic lithium was dissolved over a period of 24 hr to form Li3.0Cor(THF)247 is shown in Figure 3. The solution&#39;s color changed from colorless at t = 0 hr to light green and finally to dark green when all the lithium had dissolved. The temperature dependence of conductivity of LixCor(THF)247 solutions (x = 1, 2, 3, 4 and 5) in the temperature range of 284 K to 298 K is presented in Figure 4. The conductivity versus temperature profiles shows linear trend between &#963; and T for all five samples with each profile having a negative slope. The data is then used to compute both the conductivity &#963;0 at T0 and the temperature coefficient &#945; for Table 2.
<img alt="Figure 3" src="/files/ftp_upload/54366/54366fig3.jpg" /> 
Figure 3: The three photographs in Figure 3 arranged in chronological order show the color change of the solution for Li3.0Cor(THF)247 as metallic Li is dissolved in Cor(THF)247 over 24 hr. The colors range from colorless when the metallic Li is first added (at t = 0 hr) to light green (at t = 1 hr) when some Li has dissolved and finally to dark green (at t = 24 hr) when all the Li is dissolved. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54366/54366fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/54366/54366fig4.jpg" /> 
Figure 4: Conductivity versus temperature measurements for LixCor(THF)247 solutions (x = 1, 2, 3, 4 and 5) for the temperature range of 284 K to 298 K, which show linear trends for all 5 samples (x = 1, 2, 3, 4 and 5) with negative gradients. The negative gradients indicate that all these samples exhibit metallic behavior. The conductivity versus temperature data of these 5 samples are used to compute both the conductivity &#963;0 at T0 and the temperature coefficient &#945; for Table 2. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/54366/54366fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>x</td>
			<td>&#963;0 (102 &#181;S/cm)</td>
			<td>&#945; (10-2 K-1)</td>
		</tr>
		<tr>
			<td>1</td>
			<td>1.25</td>
			<td>5.36</td>
		</tr>
		<tr>
			<td>2</td>
			<td>2.77</td>
			<td>3.79</td>
		</tr>
		<tr>
			<td>3</td>
			<td>0.23</td>
			<td>21.7</td>
		</tr>
		<tr>
			<td>4</td>
			<td>1.04</td>
			<td>4.44</td>
		</tr>
		<tr>
			<td>5</td>
			<td>1.45</td>
			<td>4.20</td>
		</tr>
	</tbody>
</table>
Table 2: &#963;0 and &#945; for LixCor(THF)247 (for x = 1, 2, 3, 4, 5) based on Equation (1). &#963;0 and &#945; are both obtained from the conductivity versus temperature data of Figure 4. The results shown in this table indicate an &#39;x&#39; dependence for both &#963;0 and &#945;.

Watch this Scientific Journal Video about 1,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions at JoVE.com

1,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions

The authors report on conductivity studies carried out on lithium solvated electron solutions (LiSES) prepared using 1,3,5-triphenylbenzene (TPB) and corannulene as electron receptors.

The authors report on conductivity studies carried out on lithium solvated electron solutions (LiSES) prepared using two types of polyaromatic ...

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7.7K Views.  Nanyang Technological University. The authors report on conductivity studies carried out on lithium solvated electron solutions (LiSES) prepared using 1,3,5-triphenylbenzene (TPB) and corannulene as electron receptors.

Video: 1,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Engineering

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar polyaromatic units, which are two corannulene moieties and a racemic hexahelicene linking them. The compound described in this work is a good host for fullerenes. Several common organic reactions, such as free-radical reactions, C-C coupling or click chemistry, are employed demonstrating the versatility of functionalization that this compound can accept. All of these reactions work for planar aromatic molecules. With subtle modifications, it is possible to achieve similar results for nonplanar polyaromatic compounds.

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Here, we present a protocol to synthesize a complex organic compound comprised of three nonplanar polyaromatic units, assembled easily with reasonable yields.

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that derive from initial 2-bromo-2-butene lithiation followed by acid mediated dienol cyclization. The revised synthesis and purification of the ligand avoids the use of mechanical stirring while still permitting access to significant quantities (39 g) of Cp*H in good yield (58%). The procedure offers other additional benefits, including a more controlled quench of excess lithium during the production of the intermediate heptadienols and a simplified isolation of Cp*H of sufficient purity for metallation with transition metals. The ligand was subsequently used to synthesize [Cp*MCl2]2 complexes of both iridium and ruthenium to demonstrate the utility of the Cp*H prepared and purified by our method. The procedure outlined herein affords substantial quantities of a ubiquitous ancillary ligand support used in organometallic chemistry while minimizing the need for specialized laboratory equipment, thus providing a simpler and more accessible entry point into the chemistry of 1,2,3,4,5-pentamethylcyclopentadiene.

Reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented. The revised protocol for the synthesis and purification of the ligand minimizes the need for specialized laboratory equipment while simplifying reaction workups and product purification. Use of Cp*H in the synthesis of [Cp*MCl2]2 complexes (M = Ru, Ir) is also described.

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals

Protocols for the isolation of the commonly employed cyclic (alkyl)(amino) carbene (CAAC) and N-heterocyclic carbene (NHC) are reported. Furthermore, the synthesis of their mixed CAAC&#8211;NHC &#8220;Wanzlick&#8221; dimer and the synthesis of the related stable organic &#8220;olefin&#8221; radical are presented. The main goal of this manuscript is to give a detailed and general protocol for the synthetic chemist of any skill level on how to prepare free heterocyclic carbenes by deprotonation using filter cannulas. Due to the air-sensitivity of the synthesized compounds, all experiments are performed under inert atmosphere using either Schlenk technique or a dinitrogen filled glovebox. Controlling Wanzlick&#8217;s equilibrium (i.e., the dimerization of free carbenes), is a crucial requirement for the application of free carbenes in coordination chemistry or organic synthesis. Thus, we elaborate on the specific electronic and steric requirements favoring the formation of dimers, heterodimers, or monomers. We will show how proton catalysis allows for the formation of dimers, and how the electronic structure of carbenes and their dimers affects the reactivity with either moisture or air. The structural identity of the reported compounds is discussed based on their NMR spectra.

We present protocols for the isolation of stable heterocyclic carbenes. The synthesis of a cyclic (alkyl)(amino) carbene (CAAC) and an N-heterocyclic carbene (NHC) is demonstrated using filter cannulas and Schlenk technique. We furthermore present the synthesis of the related oxygen-sensitive, electron-rich mixed &#8220;Wanzlick dimer&#8221; and the reduced stable organic radical.

Protocols for the isolation of the commonly employed cyclic (alkyl)(amino) carbene (CAAC) and N-heterocyclic carbene (NHC) are reported. Furthermore, the ...

Magnetometric Characterization of Redox-Active MOFs Solid-State Electrochemistry

Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks

Electrochemical energy storage has been a widely discussed application of redox-active metal-organic frameworks (MOFs) in the past 5 years. Although MOFs show outstanding performance in terms of gravimetric or areal capacitance and cyclic stability, unfortunately their electrochemical mechanisms are not well understood in most cases. Traditional spectroscopic techniques, such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS), have only provided vague and qualitative information about valence changes of certain elements, and the mechanisms proposed based on such information are often highly disputable. In this article, we report a series of standardized methods, including the fabrication of solid-state electrochemical cells, electrochemistry measurements, the disassembly of cells, the collection of MOF electrochemical intermediates, and physical measurements of the intermediates under the protection of inert gases. By using these methods for quantitatively clarifying the electronic and spin state evolution within a single electrochemical step of redox-active MOFs, one can provide clear insight into the nature of electrochemical energy storage mechanisms not only for MOFs, but also for all other materials with strongly correlated electronic structures.

Author Spotlight: Magnetometric Characterization of Intermediates in the Solid-State Electrochemistry of Redox-Active Metal-Organic Frameworks  

Ex situ magnetic surveys can directly provide bulk and local information on a magnetic electrode to reveal its charge storage mechanism step by step. Herein, electron spin resonance (ESR) and magnetic susceptibility are demonstrated to monitor the evaluation of paramagnetic species and their concentration in a redox-active metal-organic framework (MOF).

Electrochemical energy storage has been a widely discussed application of redox-active metal-organic frameworks (MOFs) in the past 5 years. Although MOFs ...

1,3,5-Triphenylbenzene and Corannulene as Electron Receptors for Lithium Solvated Electron Solutions

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