Name: preparation of sns cobalt(ii) pincer model complexes of liver alcohol dehydrogenase
Uploaded: 2020-03-19T13:00:00
Description: Watch this Scientific Journal Video about Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase at JoVE.com

John Miecznikowski received financial support from the following for this project: the Connecticut NASA Space Grant Alliance (Award Number P-1168), the Fairfield University Science Institute, College of Arts and Sciences Publication Fund, Fairfield University Faculty Summer Research Stipend, and National Science Foundation-Major Research Instrumentation Program (Grant Number CHE-1827854) for funds to acquire a 400 MHz NMR spectrometer. He also thanks Terence Wu (Yale University) for assistance in acquiring electrospray mass spectra. Jerry Jasinski acknowledges the National Science Foundation-Major Research Instrumentation Program (Grant Number CHE-1039027) for funds to purchase an X-ray diffractometer. Sheila Bonitatibus, Emilse Almanza, Rami Kharbouch, and Samantha Zygmont acknowledge the Hardiman Scholars Program for providing their summer research stipend.

1. Synthesis of chloro-(n3-S,S,N)-[2,6-bis(N-isopropyl-N&#8217;-methyleneimidazole-2-thione)pyridine]cobalt(II)tetrachlorocobaltate [4]
<ol>
	<li>To prepare complex 4, add 0.121 g (3.12 x 10-4 mol) of 2,6-bis(N-isopropyl-N&#8217;-methyleneimidazole-2-thione)pyridine (C19H25N5S2)6 to 15 mL of acetonitrile in a 100 mL round bottom flask. Next, to this solution, add 0.0851 g (3.58 x 10-4 mol) of cobalt chl...

<ol>
	<li>Holm, R. H., Kennepohl, P., Solomon, E. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+Functional+Aspects+of+Metal+Sites+in+Biology.">Structural and Functional Aspects of Metal Sites in Biology.</a> Chemical Reviews. 96 (7), 2239-2314 (1996).</li><li>Ibers, J. A., Holm, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+coordination+sites+in+metallobiomolecules.">Modeling coordination sites in metallobiomolecules.</a> Science. 209 (4453), 223-235 (1980).</li><li>Kannan, K. K., 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=Crystal+structure+of+human+erythrocyte+carbonic+anhydrase+B.+Three-dimensional+structure+at+a+nominal+2.2-A+resolution.">Crystal structure of human erythrocyte carbonic anhydrase B. Three-dimensional structure at a nominal 2.2-A resolution.</a> Proceedings of the National Academy of Sciences USA. 72 (1), 51-55 (1975).</li><li>Eklund, H., Br&#228;nd&#233;n, C. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+differences+between+apo-+and+holoenzyme+of+horse+liver+alcohol+dehydrogenase.">Structural differences between apo- and holoenzyme of horse liver alcohol dehydrogenase.</a> Journal of Biological Chemistry. 254, 3458-3461 (1979).</li><li>Miecznikowski, J. R., 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=Syntheses,+Characterization,+Density+Functional+Theory+Calculations+and+Activity+of+Tridentate+SNS+Zinc+Pincer+Complexes.">Syntheses, Characterization, Density Functional Theory Calculations and Activity of Tridentate SNS Zinc Pincer Complexes.</a> Inorganica Chimica Acta. 376, 515-524 (2011).</li><li>Miecznikowski, J. R., 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=Syntheses,+Characterization,+Density+Functional+Theory+Calculations,+and+Activity+of+Tridentate+SNS+Zinc+Pincer+Complexes+Based+on+Bis-Imidazole+or+Bis-Triazole+Precursors.">Syntheses, Characterization, Density Functional Theory Calculations, and Activity of Tridentate SNS Zinc Pincer Complexes Based on Bis-Imidazole or Bis-Triazole Precursors.</a> Inorganica Chimica Acta. 387, 25-36 (2012).</li><li>Sunderland, J. R., 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=Investigation+of+liver+alcohol+dehydrogenase+catalysis+using+an+NADH+biomimetic+and+comparison+with+a+synthetic+zinc+model+complex.">Investigation of liver alcohol dehydrogenase catalysis using an NADH biomimetic and comparison with a synthetic zinc model complex.</a> Polyhedron. 114, 145-151 (2016).</li><li>Miecznikowski, J. R., 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+characterization+of+three-+and+five-coordinate+copper(II)+complexes+based+SNS+ligand+precursors.">Synthesis and characterization of three- and five-coordinate copper(II) complexes based SNS ligand precursors.</a> Polyhedron. 80, 157-165 (2014).</li><li>Miecznikowski, J. R., 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,+Characterization,+and+Computational+Study+of+Three-Coordinate+SNS+Copper(I)+Complexes+based+on+Bis-Thione+Ligand+Precursors.">Synthesis, Characterization, and Computational Study of Three-Coordinate SNS Copper(I) Complexes based on Bis-Thione Ligand Precursors.</a> Journal of Coordination Chemistry. 67, 29-44 (2014).</li><li>Lynn, M. A., 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=Copper(I)+SNS+Pincer+Complexes:+Impact+of+Ligand+Design+and+Solvent+Coordination+on+Conformer+Interconversion+from+Spectroscopic+and+Computational+Studies.">Copper(I) SNS Pincer Complexes: Impact of Ligand Design and Solvent Coordination on Conformer Interconversion from Spectroscopic and Computational Studies.</a> Inorganica Chimica Acta. 495, (2019).</li><li>. Web Elements Available from: <a target="_blank" href="https://www.webelements.com/zinc/atom_sizes.html">https://www.webelements.com/zinc/atom_sizes.html</a> (2019)</li><li>. Web Elements Available from: <a target="_blank" href="https://www.webelements.com/cobalt/atom_sizes.html">https://www.webelements.com/cobalt/atom_sizes.html</a> (2019)</li><li>Caballero, A., D&#237;ez-Barra, E., Jal&#243;n, F. A., Merino, S., Tejeda, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=1,1'-(pyridine-2,6-diyl)bis(3-benzyl-2,3-dihydro-1H-imidazol-2-ylidine),+a+new+multidentate+N-heterocyclic+bis-carbene+and+its+silver(I)+complex+derivative.">1,1'-(pyridine-2,6-diyl)bis(3-benzyl-2,3-dihydro-1H-imidazol-2-ylidine), a new multidentate N-heterocyclic bis-carbene and its silver(I) complex derivative.</a> Journal of Organometallic Chemistry. 617-618, 395-398 (2001).</li><li>Albrecht, M., van Koten, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platinum+Group+Organometallics+Based+on+"Pincer"+Complexes:+Sensors,+Switches,+and+Catalysis.">Platinum Group Organometallics Based on "Pincer" Complexes: Sensors, Switches, and Catalysis.</a> Angewandte Chemie International Edition. 40 (20), 3750-3781 (2001).</li><li>Peris, E., Crabtree, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Key+factors+in+pincer+ligand+design.">Key factors in pincer ligand design.</a> Chemistry Society Reviews. 47, 1959-1968 (2018).</li><li>Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K., Puschmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+complete+structure,+solution,+refinement,+and+analysis+program.">A complete structure, solution, refinement, and analysis program.</a> Journal of Applied Crystallography. 42, 339-341 (2009).</li><li>Sheldrick, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrated+Space+Group+and+Crystal+Structure+Determination.">Integrated Space Group and Crystal Structure Determination.</a> Acta Crystallography. 71, 3-8 (2015).</li><li>Sheldrick, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+Structure+Refinement+with+SHELXL.">Crystal Structure Refinement with SHELXL.</a> Acta Crystallography. 71, 3-8 (2015).</li><li>Pauling, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-metal+bond+lengths+in+complexes+of+transition+metals.">Metal-metal bond lengths in complexes of transition metals.</a> Proceedings of the National Academies of the Sciences of the United States of America. 73, 4290-4293 (1976).</li><li>Trzhtsinskaya, B. V., Abramova, N. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imidazole-2-Thiones:+Synthesis,+Structure,+Properties.">Imidazole-2-Thiones: Synthesis, Structure, Properties.</a> Sulfur Reports. 10 (4), 389 (1991).</li><li>Schneider, G., Eklund, H., Cedergren-Zeppezauer, E., Zeppezauer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+structure+of+the+active+site+in+specifically+metal-depleted+and+cobalt+substituted+horse+liver+alcohol+dehydrogenase+derivatives.">Crystal structure of the active site in specifically metal-depleted and cobalt substituted horse liver alcohol dehydrogenase derivatives.</a> Proceedings of the National Academies of the Sciences of the United States of America. 80, 5289-5293 (1983).</li><li>Yang, L., Powell, D. R., Houser, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+variation+in+copper(I)+complexes+with+pyridylmethylamide+ligands:+structural+analysis+with+a+new+four-coordinate+geometry+index,+&#964;4.">Structural variation in copper(I) complexes with pyridylmethylamide ligands: structural analysis with a new four-coordinate geometry index, &#964;4.</a> Dalton Transactions. , 955-964 (2007).</li></ol>

The preparation of complexes 4 and 5 is facile. The key step is to add the solid CoCl2&#183;6H2O to an acetonitrile solution that contains the respective ligand precursor. The solution turns dark green within seconds after the addition of CoCl2&#183;6H2O to form complex 4. The solution turns bright blue after the addition of CoCl2&#183;6H2O to form complex 5. To ensure complete reaction, t...

The purpose of the presented method is to prepare small-molecule analogs of LADH to further understand the catalytic activity of metalloenzymes. LADH is a dimeric enzyme that contains a cofactor-binding domain and zinc(II) metal-containing catalytic domain1. LADH, in the presence of co-factor NADH, can reduce ketones and aldehydes to their respective alcohol derivatives2. In the presence of NAD+, LADH can perform reverse catalysis of oxidation of alcohols to ketones and aldehydes2. The crystal structure of LADH&#8217;s active site shows that its zinc(II) metal center is bound to one nitrogen atom, provided by a histidine side chain and two sulfur atoms and offered by two cysteine ligands3. Further research has shown that the zinc metal center is ligated with a labile water molecule, resulting in pseudo-tetrahedral geometry around the metal center4.
We have previously reported and utilized SNS pincer ligand precursors as well as metallated the ligand precursors with ZnCl2 to form Zn(II) complexes that contain the tridentate ligand precursor5,6,7. These ligand precursors are shown in Figure 1. These zinc(II) complexes exhibited activity for the stoichiometric reduction of electron-poor aldehydes and are thus model complexes for LADH. Subsequently, the synthesis and characterization of a series of copper(I) and copper(II) complexes that contain SNS ligand precursors have been reported8,9,10.
Although LADH is a zinc(II) enzyme, we are interested in preparing cobalt(II) model complexes of LADH in order to obtain more spectroscopic information about the cobalt(II) analogs of LADH. The cobalt(II) complexes are colored, whereas the zinc(II) complexes are off-white. Since the cobalt(II) complexes are colored, ultraviolet visible spectra of the complexes can be obtained, in which information about the strength of the ligand field in cobalt(II) complexes can also be gathered. By using information from Gaussian calculations and the experimentally obtained ultra-violet visible spectra, information about the strength of the ligand field can be deduced. Cobalt(II) is a good substitute for zinc(II), since both ions have similar ionic radii and similar Lewis acidities11,12.
The presented method involves synthesizing and characterizing model complexes to attempt to mimic the natural catalytic behavior of LADH5,6. We have previously metallated a family of ligand precursors with ZnCl2 to form zinc(II) model complexes of LADH, which modeled the structure and reactivity of the zinc active site in LADH4. Through multiple experiments, these pincer ligands have proven to be robust under different environmental conditions and have remained stable with a diverse collection of attached R-groups.5,6
Tridentate ligands are preferable compared to monodentate ligands, because they have been found to be more successful with metalation due to the strong chelate effects of tridentate ligands. This observation is due to a more favored entropy of tridentate pincer ligand formation in comparison to a monodentate ligand13. Furthermore, tridentate pincer ligands are likely to prevent dimerization of the metal complexes, which is favored because dimerization is likely to slow catalytic activity of a complex14. Thus, using tridentate pincer ligands has been proven successful in organometallic chemistry in the preparation of catalytic active and robust complexes. SNS pincer complexes have been less studied than other pincer systems, as pincer complexes usually contain second and third row transition metals15.
This research on metalloenzymes can help further the understanding of their enzymatic activity, which can be applied to other areas in biology. This method of synthesizing model complexes compared to the alternative method (synthesizing the entire protein of LADH) is favorable for a number of reasons. The first advantage is that model complexes are low in molecular mass and are still capable of accurately representing catalytic activity and environmental conditions of the natural enzyme&#8217;s active site. Second, model complexes are simpler to work with and produce reliable and relatable data.
This manuscript describes the synthetic preparation and characterization of two cobalt(II) pincer model complexes of LADH. Both complexes feature a pincer ligand that contains sulfur, nitrogen, and sulfur donor atoms. The first complex (4) is based on an imidazole precursor, and the second (5) is based on a triazole precursor. The complexes show reactivity for the stoichiometry reduction of electron poor aldehydes in the presence of a hydrogen donor. These reactivity results will be reported in a subsequent manuscript.

<table>
	<tbody>
		<tr>
			<td>100 mL Round Bottomed Flask</td>
			<td>Chem Glass</td>
			<td>CG150691</td>
			<td>100mL Single Neck Round Bottomed Flask, 19/22 Outer Joint</td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Fisher</td>
			<td>HB9823-4</td>
			<td>HPLC Grade</td>
		</tr>
		<tr>
			<td>Chiller for roto-vap</td>
			<td>Lauda</td>
			<td>L000638</td>
			<td>Alpha RA 8</td>
		</tr>
		<tr>
			<td>Cobalt Chloride hexahydrate</td>
			<td>Acros Organics</td>
			<td>AC423571000</td>
			<td>Acros Organics</td>
		</tr>
		<tr>
			<td>Diethyl Ether</td>
			<td>Fisher</td>
			<td>E-138-1</td>
			<td>Diethyl Ether Anhydorus</td>
		</tr>
		<tr>
			<td>graduated cylinder</td>
			<td>Fisher</td>
			<td>S63456</td>
			<td>25 mL graduated cylinder</td>
		</tr>
		<tr>
			<td>hotplate</td>
			<td>Fisher</td>
			<td>11-100-49SH</td>
			<td>Isotemp Basic Stirring Hotplate</td>
		</tr>
		<tr>
			<td>jars</td>
			<td>Fisher</td>
			<td>05-719-481</td>
			<td>250 mL jars</td>
		</tr>
		<tr>
			<td>Ligand</td>
			<td>-----</td>
			<td>-----</td>
			<td>Synthezied previously by Professor Miecznikowski</td>
		</tr>
		<tr>
			<td>medium cotton balls</td>
			<td>Fisher</td>
			<td>22-456-80</td>
			<td>medium cotton balls</td>
		</tr>
		<tr>
			<td>one dram vials</td>
			<td>Fisher</td>
			<td>03-339</td>
			<td>one dram vials with TFE Lined Cap</td>
		</tr>
		<tr>
			<td>pipet</td>
			<td>Fisher</td>
			<td>13-678-20B</td>
			<td>5.75 inch pipets</td>
		</tr>
		<tr>
			<td>pipet bulbs</td>
			<td>Fisher</td>
			<td>03-448-21</td>
			<td>Fisher Brand Latex Bulb for pipet</td>
		</tr>
		<tr>
			<td>recrystallizing dish for sand bath</td>
			<td>Fisher</td>
			<td>08-741 D</td>
			<td>325 mL recrystallizing dish for sand bath</td>
		</tr>
		<tr>
			<td>reflux condensor</td>
			<td>Chem Glass</td>
			<td>CG-1218-A-22</td>
			<td>Condenser with 19/22 inner joint</td>
		</tr>
		<tr>
			<td>Rotovap</td>
			<td>Heidolph Collegiate</td>
			<td>36000090</td>
			<td>Brinkmann; Heidolph Collegiate Rotary Evaporator with Heidolph WB eco bath Heidolph Rotary Evaporator</td>
		</tr>
		<tr>
			<td>sea sand for sandbath</td>
			<td>Acros Organics</td>
			<td>612355000</td>
			<td>washed sea sand for sand bath</td>
		</tr>
		<tr>
			<td>Stir bar</td>
			<td>Fisher</td>
			<td>07-910-23</td>
			<td>Egg-Shaped Magnetic Stir Bar</td>
		</tr>
		<tr>
			<td>Vacum grease</td>
			<td>Fisher</td>
			<td>14-635-5D</td>
			<td>Dow Corning High Vacuum Grease</td>
		</tr>
		<tr>
			<td>vacuum pump for rotovap</td>
			<td>Heidolph Collegiate</td>
			<td>36302830</td>
			<td>Heidolph Rotovac Valve Control</td>
		</tr>
	</tbody>
</table>

preparation of sns cobalt(ii) pincer model complexes of liver alcohol dehydrogenase

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each possessing two sulfur and one nitrogen donor atom functionalities (SNS) and based on bis-imidazole or bis-triazole compounds) are metallated with CoCl2&#183;6H2O to afford tridentate SNS pincer cobalt(II) complexes. Preparation of the cobalt(II) model complexes for liver alcohol dehydrogenase is facile. Based on a quick color change upon adding the CoCl2&#183;6H2O to acetonitrile solution that contains the ligand precursor, the complex forms rapidly. Formation of the metal complex is complete after allowing the solution to reflux overnight. These cobalt(II) complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH). The complexes are characterized using single crystal X-ray diffraction, electrospray mass spectrometry, ultra-violet visible spectroscopy, and elemental analysis. To accurately determine the structure of the complex, its single crystal structure must be determined. Single crystals of the complexes that are suitable for X-ray diffraction are then grown via slow vapor diffusion of diethyl ether into an acetonitrile solution that contains the cobalt(II) complex. For high quality crystals, recrystallization typically takes place over a 1 week period, or longer. The method can be applied to the preparation of other model coordination complexes and can be used in undergraduate teaching laboratories. Finally, it is believed that others may find this recrystallization method to obtain single crystals beneficial to their research.

Synthesis 
The syntheses of complexes 4 and 5 were successfully carried out by reacting an acetonitrile solution containing a bis-thione ligand precursor with cobalt (II) chloride hexahydrate (Figure 2). This reaction occurred at a reflux temperature in the presence of air. In general, complexes 4 and 5 were observed to be soluble in acetonitrile, dimethyl sulfoxide, dichloromethane, and methanol. Compl...

Watch this Scientific Journal Video about Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase at JoVE.com

Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase

The preparation of SNS pincer cobalt(II) model complexes of liver alcohol dehydrogenase is presented here. The complexes can be prepared by reacting the ligand precursor with CoCl2&#183;6H2O and can then be recrystallized by allowing diethyl ether to slowly diffuse into an acetonitrile solution that contains the cobalt complex.

Preparation of SNS Cobalt(II) Pincer Model Complexes of Liver Alcohol Dehydrogenase

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each ...

This method can be used to prepare a chemical model complex of an enzyme liver alcohol dehydrogenase and to grow single crystals. The advantages of this technique are that the complex formation is facile and that the recrystallization method can be applied to the preparation of other coordination complexes. This method can provide insight into the preparation and recrystallization of inorganic coordination compounds and can be applied to any compound of interest to grow single crystals.It takes practice to grow the single crystals. The key is to make the acetonitrile solution that contains the metal complex as concentrated as possible. To prepare complex four, add 0.121 grams of 2, 6-BIS-N-isopropyl-N'methyleneimidzole-2-thione-pyridine and 0.0851 grams of cobalt II chloride hexahydrate to a 100 milliliter round bottom flask containing 15 milliliters of acetonitrile.The reaction should change from a light yellow color to emerald green immediately after the cobalt II chloride hexahydrate is added. Then reflux and stir the reaction for 20 hours to ensure complete reaction before using a rotovap under reduced pressure to remove the solvent. For chloro-N3-S, S, N-2, 6-BIS-N-isopropyl-N'methyleneimidzole-2-thione-pyridine cobalt II tetrachlorocobaltate recrystallization by slow vapor diffusion, dissolve the solute in 10 milliliters of acetonitrile, filer the solution, then aliquot the solution evenly between one dram vials.Add 1.5 milliliters of fresh acetonitrile solution to each vial and snugly cap the vials with cotton. Place the vials in a 240 milliliter jar containing 50 milliliters of diethyl ether and close the jar with a cap. Then allow the crystals to grow for up to a week.To prepare complex five, add 0.183 grams of 2, 6-BIS-N-isopropyl-N'methylenetriazole-2-thione-pyridine and 0.223 grams of cobalt II chloride hexahydrate to 15 milliliters of acetonitrile in a 100 milliliter round bottom flask. The reaction should change color from a light yellow color to royal blue immediately after the cobalt II chloride hexahydrate is added. Then reflux and stir the reaction for 20 hours to ensure complete reaction before removing the solvent using a rotovap under reduced pressure.For chloro-N3-S, S, N-2, 6-BIS-N-isopropyl-N'methylenetriazole-2-thione-pyridine cobalt II tetrachlorocobaltate recrystallization by slow vapor diffusion, dissolve the solute in 10 milliliters of acetonitrile and filter the solution before aliquoting the solution evenly in one dram vials. Fill each vial with 1.5 milliliters of acetonitrile solution and snugly cap the vials with cotton. To grow high-quality single crystals, it's critical that the cotton plug fits snugly within the one dram vial.We use a little less than one cotton ball for each vial. Then place the vials in a jar containing 50 milliliters of diethyl ether, close the jar with a cap, and allow the crystals to grow for up to a week. The synthesis of complexes four and five can be successfully carried out by reacting an acetonitrile solution containing a bis-thione ligand precursor with cobalt II chloride hexahydrate.The acquisition of single crystals of complexes four and five via slow vapor diffusion is an excellent method for growing single crystals for hard to crystallize samples. Elemental analysis of the recrystallized complexes suggests that complexes four and five are pure because the calculated percentages of carbon, hydrogen, and nitrogen are in excellent agreement with the found percentages of carbon, hydrogen, and nitrogen. In addition, ultraviolet visible spectroscopy of complexes four and five reveals that complex four exhibits three peaks in the visible region at 680, 632, and 589 nanometers, and that complex five exhibits four peaks in the visible region at 682, 613, 588, and 573 nanometers.The most important thing to remember is that when you prepare the complex, you must add cobalt chloride hexahydrate to an acetonitrile solution that contains a ligand precursor. The recrystallization method can be applied to any organic or inorganic compound that is difficult to recrystallize. We are currently preparing cobalt II complexes that do not contain cobalt in the counter-anion and screening the complexes for their reactivity.Be sure to conduct all of the reactions in a fume hood.

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Preparation of Carbon Nanosheets at Room Temperature

Amphiphilic molecules equipped with a reactive, carbon-rich "oligoyne" segment consisting of conjugated carbon-carbon triple bonds self-assemble into ...

Facile Preparation of 4-Substituted Quinazoline Derivatives

Reported in this paper is a very simple method for direct preparation of 4-substituted quinazoline derivatives from a reaction between substituted ...

Preparation of Biopolymer Aerogels Using Green Solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...