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Zinc(ii) complexes with uncommon aminal and hemiaminal ether derivatives: Synthesis, structure, phosphatase activity and theoretical rationalization of ligand and complex formation
S PURKAIT, P CHAKRABORTY, A FRONTERA, A BAUZá, E ZANGRANDO, D DAS
Published in Royal Society of Chemistry
2018
Volume: 42
   
Issue: 15
Pages: 12998 - 13009
Abstract
Condensation of N-(2-hydroxyethyl)ethylenediamine and pyridine-2-carbaldehyde in the presence of ZnX2 salts (X = ClO4 -, Cl-, Br-, I-) generates four complexes, namely, [ZnL1Cl](ClO4) (1), [ZnL1Cl][ZnCl3(H2O)]·2H2O (2), [ZnL1Br][ZnBr3(H2O)]·2H2O (3), and [Zn(L2)3]I2 (4), where L1 and L2 are aminal and hemiaminal ether derivatives, i.e., (E)-N-((pyridine-2-yl)methylene)-2-((2-pyridine-2-yl)oxazolidin-3-yl)ethanamine and 2-(2-pyridin-2-yl-imidazolidin-1-yl)-ethanol, respectively. No complex with the expected Schiff-base ligand (E)-2-(2-(pyridin-2-ylmethyleneamino)ethylamino)ethanol (L) or with 2-(2-pyridyl-3-(2-hydroxyethyl))oxazolidine (L3) was obtained. The structures of complexes 1, 3, and 4 have been elucidated by single crystal X-ray diffraction. All the complexes have been characterized by detailed NMR (1H, 13C and DEPT-135) and ESI-MS analyses, indicating retention of solid state structures in the solution phase. Complex 1 deserves special mention as during its formation, the ClO4 - ion undergoes reduction to Cl- and thus, it forms a mixed anionic ligand complex. Thorough DFT calculations have been performed at the BP86-D3/def2-TZVP level of theory to rationalize the ligand and complex formation. The calculations suggest that the aminal form (L1) is the most favored species followed by the Schiff-base, whereas the hemiaminal ether form (L3) is the least preferred one. The role of halides during the formation of the monoanionic [ZnX3(H2O)]- species is crucial, and the achieved complex is highly favored when X = Cl and disfavored for X = I; this trend has been rationalized by the DFT calculations. The phosphatase activities of the complexes have been investigated, and their efficiencies follow the order 2 > 1 > 3 > 4. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
About the journal
JournalData powered by TypesetNew Journal of Chemistry
PublisherData powered by TypesetRoyal Society of Chemistry
ISSN1144-0546