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Quantum Chemical Studies of Potential Associates in Europium (III) Alginate Solutions

Abstract

Metal-alginate complexes (especially, lanthanide gels) are particularly interesting for medical and biological analysis due to their luminescent properties upon UV light excitation. Unfortunately, synthesis and further physical and chemical studies of such complexes is inhibited by their high cost. However, this problem can be solved by using quantum chemical methods to predict potential properties of lanthanide alginates based on the results of their geometry optimization and electronic structure calculation. This study presents the results of quantum chemical analysis of possible structures and UV-vis spectra of europium (III) alginates and comparison of these spectra with existing experimental data. Geometry optimization was performed by PM7/SPARKLE method (software – MOPAC 2012) combined with COSMO solvation model. UV-vis spectra were calculated using ZINDO/S method (Orca software). We have studied 6 possible structures with various metal-to-ligand ratios (1:1, 1:2 and 1:3) and different ligand composition (using both monoprotonated (HAlg- ) and deprotonated alginate ions (Alg2-). The greater amount of ligands participating in coordination lead to significant decrease in complex stability (due to increased number of Ln-O bonds and decrease of their energy) and increase of electron acceptor properties. Comparison between calculated and experimental UV-vis spectra of studied complexes showed that Eu alginate solution contains several types of complex ions, most likely – Eu(Halg)(Alg) and [Eu(Alg)3 ] 3- . This shows that chosen computation method allows to predict UV-vis absorption spectra of lanthanide complexes with polymeric acids which can be used for medical and biological analysis. 

DOI: 
10.18500/1816-9775-2017-17-1-19-23
References

1. Whistler R. L., BeMiller J. N. Industrial Gums, Polysaccharides and Their Derivatives. N.Y. : Academic Press, 1993. P. 219.

2. Weissman S. I. Intramolecular energy transfer. The fluorescence of complexes of europium // J. Chem. Phys. 1942. Vol. 10. P. 214–217

3. Topuz F., Henke A., Richtering W., Groll J. Magnesium ions and alginate do form hidrogels : A rheological study // J. Soft Matter. 2012. Vol. 8 (18). P. 4877–4881.

4. Raghavachari R. Near-Infrared Applications in Biotechnology // CRC Press. 2001. P. 392.

5. Balashova T. V., Pushkarev A. P., Ilichev V. A., Lopatin M. A., Katkova M. A., Baranov E. V., Fukin G. K., Bochkarev M. N. Lanthanide phenolates with heterocyclic substituents. Synthesis, structure and luminescent properties // Polyhedron. 2013. Vol. 50. P. 112–120.

6. Desurvire E. Erbium-Doped Fiber Amplifiers: Principles and Applications. N.Y. : Wiley-Interscience, 1994. P. 800.

7. Dutra J. D. L., Filho M. A., Rocha G. B., Freire R. O., Simas A. M., Stewart J.J.P. Sparkle/PM7 Lanthanide Parameters for the Modeling of Complexes and Materials // J. Chem. Theory Comput. 2013. Aug. 13. Vol. 9 (8). P. 3333–3334.

8. Klamt A., Schüürmann G. COSMO : a new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient // J. Chem. Soc. Perkin Transactions 2. 1993. Iss. 5. P. 799–805.

9. Stewart J. J. P. Stewart Computational Chemistry MOPAC2012 version 12.301M. URL: http://OpenMOPAC.net (дата обращения: 14.10.15).

10. Dolg M., Stoll H., Preuss H. A Combination of Quasirelativistic Pseudopotential and Ligand Field Calculations for Lanthanoid Compounds // Theor. Chim. Acta. 1993.Vol. 85. P. 411–450.

11. Dolg M., Stoll H., Savin A., Preuss H. Energy-a djusted Pseudopotentials for the Rare Earth Elements // Theor. Chim. Acta. 1989. Vol. 75. P. 173–194.

12. Niese F. The ORCA program system // Wiley International Reviews : Computational Molecular Science. 2012. Vol. 2, iss. 5. P. 75–78.

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