Introduction
Coordination complex usually consists of a metallic coordination center and can be surrounded by bound molecules. Thus these are known these coordination complexes are known as ligands as they bind several molecules strongly almost irreversibly. Coordination complexes therefore coordinate covalent bonds on the molecule.
There is specific nomenclature for coordination complexes. Particularly, the donor atom is the ligand that is bonded to the central atom. Here we are making Aluminium acetylacetonate, Al(acac)3, also referred to as Al(acac)3, and the metal ion is the aluminum and the donor atoms are the acetylacetonate. If there are more than one donor atom bonded to the central atom it is called a polydentate (multiple bonded) ligand. For aluminium acetylacetonate there are three acetylacetonate ligands on the aluminium central atom. Formation of these kind of complexes is call chelation or coordination and are therefore called chelate complexes.
Aluminium acetylacetonate has some general properties that are interesting. It has a 324.305179 g/mol and monoisotopic mass/exact mass of 324.115352 g/mol. Additionally, aluminium acetylacetonate has D3 symmetry and is isomorphous with The molecule has D3 symmetry, being isomorphous with other octahedral tris(acetylacetonate). (Dymock, 1974). The importance of knowing the symmetry of the molecule and building these structures helps 1) to characterize crystal structures 2) explain or predict some of the molecules properties like dipole moment or chirality 3) gives an understanding of the its spectroscopic transitions for Raman and infared spectroscopy (Slabzhennikov, 2006) 4) gives an indication of how or where a chemical reaction can occur on a molecule.
The aim of this study was to synthesize and use analytical methods Nuclear Magnetic Resonance and Mass Spectrometry to characterize the properties. This experiment is the stepping stone in understanding how chemical geometries could be used to form similar useful chemicals with nearly predetermined properties. Specifically, Aluminium acetylacetonate can act as a precursor to aluminum oxide films which is useful for cosmetic fillers, paints and catalysis (Hudson, 2002).
Experimental
All materials and laboratory equipment were provided by the laboratory. All safety equipment was used. The procedure was outlined in the lab notebook and presented here in brief with any deviations
Synthesis Procedure of Al(acac)3 and filtering
Under the fumehood 3.34 g of acetylacetone was added to 20 mL of water to a conical flask. Aqueous ammonia was added to the solution while stirring with a glass rod until the oily droplets disappeared from the flask and to form the water soluble acac soluton. A solution of 0.005 mole of hydrated aluminum sulfate was precipitated in deionized water and then added to the acac solution trying to form as little Al(acac)3 precipitate as possible. Any precipitated Al(acac)3 was filtered using a Buchner funnel flask. The product was washed with 10 mL distilled water and air dried. Product was transferred to a labelled glass vial and then analyzed.
Balanced chemical reaction and calculation of chemical
Acetylacetone is has a central hydrogen and this is removed to give the acac- ion:
Final chemical reaction is
Al^3+(aq) + 3acac- → Al(acac)3
Al3+(aq) + 3acac- → Al(acac)3
Yield was calculated using the following equation:
Al2(SO4)3 * 18 H2O = 666
Theoretical yield is g x 1/ ??? g/mol =???? moles
Actual Yield (grams) / Theoretical Yield (grams) x 100 % = Percent Yield
A vial containing was weighed without or product then with our product to determine the final weight.
Results and discussion
After the reaction a final weight of g ( g/mol) x : stoichiometry of Al(acac)3 was obtained which gave a percent yield of % based on g of starting material.
The material was white with a yellow tinge.
Analysis of Al(acac)3 using NMR and MS
Figure 1 13C NMR for Al(acac)3
Shift (ppm) Group
191.4506 CO
101.0921 CH
26.7414 CH3
Figure 2 1HNMR Spectrum for Al(acac)3
Shift (ppm) Group
5.9988 CH
2.1704 CH3
2.0642 CH3
2.0134 CH3
1.9843 CH3
1.8525 CH3
With a higher resolutions spectrometer they could have observed individual spectral shifts for both 1HNMR and 13CNMR. The 18 methyl protons should also show two distinct groups (Wong, 2011). The two NMR show how coordinated and symmetrical this chemical as the carbons and hydrogens respectively are within the same environment.
m/Z Group
225.05 Al(acac)2
347.10 Al(acac)3*Na
671.21 2*(Al(acac)3)*Na
One acac can fragment in the mass spectrometer.
Conclusion
We made Al(acac)3 in a one step reaction and analyzed it with NMR and MS. By understanding how to make chemicals with D3 symmetry we can learn how similar chemical reactions can take place with the same coordination. Additionally, we can predict that the D3 symmetry compounds (although we did not do it here) may have similar spectrophotometric properties.
Questions
Curcumin is the chemical that is responsible in tumeric. This is the same compound that stains people’s shirts when they go to Indian restaurants.
The chemical structure for Curcumin is:
In order to make this you would have to make the enol form in order to make complex. (Subhan, 2013). There has to be the formation of the proton with ethanol and mixing with base to shift it in favour of the complex to remove this proton. Both oxygen centres can bind to the metal ring to form the six-membered ring.
2. A pure sample of Al(acac)3 can be made without the impurity of Aluminum hydroxide by
in the final step could be added whereby the Al(acac)3 dissolving the powder in acetone. The aluminum hydroxide will have a different phase then the Al(acac)3 and can be sucked off with a pipette. This is a standard wash procedure.
References
Dymock, K., & Palenik, G. J. (1974). Tris (acetylacetonato) gallium (III). Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry, 30(5), 1364-1366.
Slabzhennikov, S. N., Ryabchenko, O. B., & Kuarton, L. A. (2006). Interpretation of the IR spectra of aluminum, gallium, and indium tris (acetylacetonates). Russian Journal of Coordination Chemistry, 32(8), 545-551.
Hudson, L. K., Misra, C., Perrotta, A. J., Wefers, K., & Williams, F. S. (2002). Aluminum oxide. Ullmann's encyclopedia of industrial chemistry.
Wong, A., Smith, M. E., Terskikh, V., & Wu, G. (2011). Obtaining accurate chemical shifts for all magnetic nuclei (1H, 13C, 17O, and 27Al) in tris (2, 4-pentanedionato-O, O′) aluminium (III)—A solid-state NMR case study. Canadian Journal of Chemistry, 89(9), 1087-1094.
Subhan, M. A., Alam, K., Rahaman, M. S., Rahman, M. A., & Awal, R. (2013). Synthesis and Characterization of Metal Complexes Containing Curcumin (C 21 H 20 O 6) and Study of their Anti-microbial Activities and DNA-binding Properties. Journal of Scientific Research, 6(1), 97-109.
