Síntese, estrutura cristalina e propriedades magnéticas de complexos resultantes da interação de cobalto(II), níquel(II) e cobre(II) com tpymt ou Hbpcam
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2017-07-27
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Universidade Federal de Goiás
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The synthesis, spectroscopic characterization, structural study and magnetic properties of four
new compounds of formula [Co(bpcam)2]ClO4dmsoH2O (1), [Co(bpcam)2]2[Co(NCS)4]dmsoH2O
(2), [Ni(bpcam)2]H2O (3) e [Cu(bpcam)Cl(H2O)] (4) [bpcam = bis(2-pyrimidylcarbonyl)amidate]
are reported. The Co(II)-assisted hydrolysis of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt) in
mild conditions leads to a mononuclear unit of [CoIII(bpcam)2]+ which is isolated as perclorate (1)
and tetrakis(N-thiocianate)cobaltate(II) (2) salts. The compounds 3 and 4 are obtained by reacting
Hbpcam with the metallic salts nickel(II) perchlorate hexahydrate (3) and copper(II) chloride
dihydrate (4) in stoichiometric ratios. Differently from the literature data, the hydrolysis of tpymt
in the presence of copper(II) chloride also results in 4, which contains bpcam-. Each bpcamgroup
in 1-4 acts as a tridentate ligand being coordinated to the cobalt(III) (1 and 2)/nickel(II)
(3)/ copper(II) (4) ions through three nitrogen atoms in a meridional arrangement giving rise to
six-coordinate (1 and 3) or five-coordinate (4) metallic ions, whereas six-coordinate cobalto(III)
and four-coordinate cobalt(II) coexist in 2. Cyclic voltammetry of 1 in acetonitrile shows the
occurrence of one quasi reversible CoIII ↔ CoII process. Variable-temperature magnetic
susceptibility measurements on samples of 2-4 were carried out in the temperature range 1.9-295
K. The continuous decreasing of T from 2,68 cm3mol-1K at room temperature to 1.32 cm3mol-1K
at 1,9 K observed for 2 is assigned to zero-field splitting (ZFS) of pseudotetraedral complex
[Co(NCS)4]2- anion. A Curie law for a magnetically isolated nickel(II) ion in the high
temperatures domain is observed for 3 and the small decrease of T below 10 K being due to zerofield
splitting effects. The magnetic behavior for 4 follows a Curie-Weiss law for magnetically
isolated copper(II) ions with occurrence of weak antiferromagnetic intermolecular interactions.
The fitting of experimental data of 2 and 3 through the spin Hamiltonian [M = Co (2) e Ni (3)]
led to the following values: = 2.37 (2) e 2.12 (3) e || = 34.7 (2) e 1.72 (3). Finally, the analysis of
the magnetic susceptibility data of 4 leads to a Curie-Weiss law with gCu = 2,08 e = 0,8 K, being
the Weiss constant.
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SOUZA FILHO, Renato Rabelo de. Síntese, estrutura cristalina e propriedades magnéticas de complexos resultantes da interação de cobalto(II), níquel(II) e cobre(II) com tpymt ou Hbpcam. 2017. 68 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Goiânia, 2017.