РУсскоязычный Архив Электронных СТатей периодических изданий
Журнал структурной химии/2013/№ 2/

COMPUTATIONAL STUDY ON THE STRUCTURE AND PROPERTIES OF TERNARY COMPLEXES OF Ln3+ (Ln = La, Ce, Nd and Sm) WITH 5,7-DICHLOROQUINOLINE-8-OL AND 4-VINYL PYRIDINE

In the present research, we have mainly concentrated on the survey of interactions in Ln3+ (Ln = La, Ce, Nd and Sm) ternary complexes of 5,7-dichloroquinoline-8-ol (DCQ) and 4-vinyl pyridine (VP), [Ln(VP)2(DCQ)3]3+ by means of density functional theory, Hartree-Fock and Sparkle/PM3 semi-empirical computational methods. For VP and DCQ ligands, the cation bin­ding energy sequence follows the order La3+ > Ce3+ > Nd3+ > Sm3+ as expected based on increasing in the hardness and decreasing in the ionic radius of this lanthanide cation series. A similar trend was observed in the calculated binding energy of the aforesaid ligands with the hydrated lanthanide cation series [Ln(H2O)9]3+, while the computed values of deformation energy of ligands upon complexation demonstrated an opposite order in the lanthanide cation series. Moreover, the solvent effects are considered via a polarized continuum model and provided a significant increase in the binding strength while the relative magnitude of binding energies is the same as that in the gas phase. Combining quantum and statistical mechanical calculations, we have also determined quantitatively a reliable estimate of the conformational distribution of the [Sm(VP)2(DCQ)3]3+ complex at various temperatures in the gas phase by computing the molecular partition functions and consequently the analysis of the conformational equilibrium constants.

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For VP and DCQ ligands, the cation binding energy sequence follows the order La3+ > Ce3+ > Nd3+ > Sm3+ as expected based on increasing in the hardness and decreasing in the ionic radius of this lanthanide cation series. <...> A similar trend was observed in the calculated binding energy of the aforesaid ligands with the hydrated lanthanide cation series [Ln(H2O)9]3+, while the computed values of deformation energy of ligands upon complexation demonstrated an opposite order in the lanthanide cation series. <...> Moreover, the solvent effects are considered via a polarized continuum model and provided a significant increase in the binding strength while the relative magnitude of binding energies is the same as that in the gas phase. <...> Combining quantum and statistical mechanical calculations, we have also determined quantitatively a reliable estimate of the conformational distribution of the [Sm(VP)2(DCQ)3]3+ complex at various temperatures in the gas phase by computing the molecular partition functions and consequently the analysis of the conformational equilibrium constants. <...> Keywords: ion imprinting, lanthanide complexes, density functional theory, polarized continuum model, conformational distribution. <...> Schematic representation of ligands: 4-vinyl pyridine (VP) and 5,7dichloroquinoline-8-ol (DCQ) plate in a highly cross-linked polymer matrix. <...> It should be noticed that there are many reports on the lanthanide ion imprinted polymer preparation [ 4—6 ]especially during the past years, which describe a preconcentrative separation of lanthanide cations by co-polymerizing [Ln(VP)2(DCQ)3]3+ ternary complexes, styrene and a cross linker, e.g. divinyl benzene, in the presence of 2,2-azo bis isobutylonitrile as an initiator. <...> In the present investigation, we shall concentrate on the quantum chemistry calculation of intrinsic interactions of lanthanide cations Ln3+ with DCQ and VP ligands from the structural and energetic viewpoints. <...> In addition to ion—ligand interactions, solvation plays an important role in the ion imprinting process. <...> Furthermore, because of the strong electrostatic character of the metal—ligand interactions, which remains effective beyond the first and even second coordination sphere, structural parameters are sensitive to the solvent effect. <...> So, we have also estimated solvent effects on the structure and binding energies of ligands in [Ln(VP)2(DCQ)3]3+ complexes by concerning a continuum representation <...>
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