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Solution Precipitate

Cu

Ag

Fe

Zn

Co

Mn

Cr

Ni

ColorMetal Observations

60mg DA in 5mL DDI water

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Department of Chemistry and of ColoradoColorado Springs

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Background: Metal complexes are commonly formed by transition metal ions and ligands. Ligands are molecules with extra electrons on atoms like oxygen and nitrogen. These electrons form a bond by filling the empty d-orbitals of the transition metal. Complexes are often very colorful, which is evident of the splitting of the d-orbitals.

Synthesis of 1-benzyl-1H-1,2,3-triazole-4-carboxylic acid and 1-benzyl-1H-1,2,3-4,5-dicarboxylic acid for use as ligands in metal binding

Maggi Braasch-Turi, Allen Schoffstall*, & Renee Henry¥

Abstract: Allyl azide and many 1-benzyl-1H-1,2,3-triazole-4-carboxylic acid and 1-benzyl-1H-1,2,3-4,5-dicarboxylic acid were synthesized to be used as ligands for metal coordination complexes. Benzyl bromide was reacted with sodium azide to form benzyl azide. Benzyl azide was reacted with methyl propiolate and dimethylacetylene dicarboxylate to form triazole derivatives via Huisgen “click” cycloaddition. The methyl esters were converted to carboxylic acids via base-promoted hydrolysis. The corresponding monocarboxylic acid and dicarboxylic acid were used to form coordination complexes with various transition metals. The dicarboxylic acid was reacted in a basic medium with a metal salt to form a precipitate. The metal salts produced Ag+, Fe2+, Fe3+, Zn2+, Co2+, Mn2+, Cr3+, and Ni2+ in solution. The solids formed were analyzed with infrared spectroscopy (IR) and far infrared spectroscopy (FIR) to observe possible geometries of the complex.

Benzyl Azide3

Methyl 1-Benzyl-1H-1,2,3-triazole-4-carboxylate3,5

1-Benzyl-1H-1,2,3-triazole-4-carboxylic acid3,5

1-Benzyl-1H-1,2,3-triazole-4,5-dicarboxylic acid (DA)3,5,7

Metal Binding8

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Motivation: A call for new ways to recycle metals was published in C & EN’s April 2015 issue1. Naturally found metals and ores are becoming scarce. Scientists are working towards recovering metals from other sources, such as biosolids from sewage. Studies have shown that biosolids are a valuable source of many lucrative metals. If a sustainable method is discovered, metals could be recovered from sewage sludge as well as from contaminated water and soil. This would decrease the need for mining more metals from the ground.

Chloropentaamminecobalt (II) chloride Hexaamminecobalt(III) chloride

Tried 3 different procedures to isolate allyl azide• Extracted with ethyl acetate & rotovap

• Co-evaporated • Extracted with dichloromethane & rotovap

• Co-evaporated, 4.128% yield• Extracted with dichloromethane & ice bath rotovap2

• 62.235% yieldThis branch of research was discontinued, however, for future work, this would still be a preferable starting material because of the allyl group might easily be modified into other functionalities. Another avenue would be to continue the synthesis in situ.

References:

In this study, new ligands were synthesized and analyzed for its metal binding ability for the reclamation of metals in aqueous solution.

General Procedure4:1) Dissolve ligand in DDI water2) Add 1M sodium bicarbonate

dropwise until pH is 73) Dissolve metal salt

(Calculated from 3:1 ligand: metal ratio)

4) Stir overnight5) Refrigerate for 2 hours6) Vacuum filter precipitate7) Rinse with ethanol and diethyl ether8) Characterize with MIR and FIR

1:1 t-butanol:H2O reflux, 1 hr

Sodium ascorbate, 1M CuSO41:1 t-butanol:H2O

reflux, 1 hr

THF, 3M NaOH

Reflux, 2 hrs

1:1 t-butanol:H2O reflux, 2 hrs

THF, 3M NaOH

Reflux, 2 hrs

Acetone63°C, 4 hrs

• Yellow-brown, oily liquid.• 88.59% yield Trial Combinations:

-20mg DA in 20mL DDI water-60mg DA in 60mL DDI water-60mg DA in 20mL DDI water-60mg DA in 5mL DDI water

Results show less water and lots of ligand produce more precipitate.

Precipitate started out white. After a few days of sitting out, the solid turned brown.

No visible precipitate. The top was left off the flask over the weekend to evaporate the water off to induce precipitation.

Fe2+ decayed to Fe3+ almost immediately in solution. This was possible due to the age of the ferrous chloride tetrahydrate reagent bottle.

Precipitation occurred almost immediately.

Precipitate starts out white in solution, but turns pink/purple when exposed to light out of solution.

Zn metal should make white complexes because of the full d-orbital. Without a empty spaces in the split d-orbital, electrons cannot jump up to higher levels to produce colors.

Solution is pink, but precipitate is a dark purple.

Solution is lavender, but precipitate is a dark green.Very small crystals have formed in the other trials.

Lots of precipitate was produced, however it was blown away in the fume hood.

Future Work:• Metal binding experiments will be performed with 1-benzyl-1H-1,2,3-

triazole-4-carboxylic acid using 5mL DDI water and 60mg of the ligand. FIR and MIR spectra will be taken to analyze for complex formation.

• Debenzylation of the ligands is another path for the ligands to see how their geometries differ without the extra hindrance.

• White-yellow crystalline solid• 93.01% yield

• Brown-yellow, very viscous oil• 74.40% yield

• White, fluffy, crystalline solid• 83.58% yield

M3+/2+/+ + 3DA [M(DA)3]3+/2+/+

This diagram1 shows how certain metals can be recycled or how they are currently unable to be recycled.

Allyl Azide3

• Off-white crystalline solid• 91.06% yield

1) Ritter, S.K. Wanted: New Ways to Recycle Metals. C&EN 2015, 93, pp 25-27.2) Yang, B.; Zhang, H.; Peng, H.; Xu, Y.; Wu, B.; Weng, W.; Li, L.The Royal Society of Chemistry, 2013.3) Butler, C. Lab Group Meeting, 2015.4) Drake, H. Lab Group Meeting, 2015.5) Moulin, F. Helvetica Chimica Acta, 1952,35, 167–180.6) Yoshida, S.; Hatakeyama, Y.; Johmoto, K.; Uekusa, H.; Hosoya, T.Journal of the American Chemical Society

2014,136 (39), 13590–13593.7) Georgiyants, V. A.; Perekhoda, L. O.Synthesis and study of 1-benzyl-1H-1,2,3-triazole-4,5-dicarboxylic acid,

2005,2, 3–6.8) Lanjewar, R. B.; Waditwar, A. M.; Garg, A. N.Journal of Radioanalytical and Nuclear Chemistry, 1987,125, 75–84.

Acknowledgements: I would like to formally acknowledge the following people and organizations in supporting me during the summer. Thank you very much for all of your help. I learned more this summer than any laboratory class could ever teach me.

• National Science Foundation• Department of Chemistry and Biochemistry at UCCS• Dr. Allen Schoffstall

• Dr. Renee Henry• Christopher Butler• Dr. Al Hagedorn

Dimethyl 1-Benzyl-1H-1,2,3-triazole-4,5-dicarboxylate3,5,6