New tri- and tetranuclear Co(II) complexes with macrocyclic Schiff base hydrazones
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RIJA, Andrei, BULHAK, Ion, DANILESCU, Olga, BOUROSH, Pavlina. New tri- and tetranuclear Co(II) complexes with macrocyclic Schiff base hydrazones. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 200.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

New tri- and tetranuclear Co(II) complexes with macrocyclic Schiff base hydrazones


Pag. 200-200

Rija Andrei1, Bulhak Ion1, Danilescu Olga1, Bourosh Pavlina2
 
1 Institute of Chemistry of the Academy of Sciences of Moldova,
2 Institute of Applied Physics, Academy of Sciences of Moldova
 
Disponibil în IBN: 7 martie 2019


Rezumat

The new tri- and tetranuclear Co(II) complexes with macrocyclic ligand obtained from 2,6- diacetylpyridine and malonic dihydrazide was synthesized using template method. A mixture of Co(SCN)2 – 2,6-diacetylpyridine – malonic dihydrazide in 1:1:1 molar ratio has been refluxed for about 3 hours giving a green precipitate. The green precipitate was transformed in orange one via deprotonation with ammonia solution. The missing band at 2079 cm-1 in the IR spectrum of orange precipitate prove the absent of NCS anions. The orange precipitate was treated with diverse inorganic acids such as: HCl, HBr, HI, HClO4, HBF4. Crystals suitable for X-ray study of new Co(II) tri- and tetranuclear complex cations with H6L and H8L ligands and inorganic anions in the external sphere have been obtained for following compounds: [Co3(H6L)(H2O)6](ClO4)6 (1), [Co4 (H8L)(H2O)8](BF4)8 (2), [Co3(H6L)(H2O)2Cl4] (Cl)2 (3), [Co4(H8L)(H2O)6Br2](Br)6 (4), [Co3(H6L)(H2O)6]I6 (5), [Co4(H8L)(H2O)8]I8 (6). We suppose that initial obtained green precipitate is a mixture of tri- and tetranuclear, because at protonation, from the same solution, we separate two different type of crystals one being trinuclear and other tetranuclear. In the IR spectrum, 2,6-diacetylpyridine fragment is supported by ν(CH3) 2988-2974, 2902 cm-1 and δ(CH3) ~1460, ~1370 cm-1; dihydrazide fragment by ν(NH) 3261-3180, and ν(C=O) 1650-1635 cm- 1. A broad band at ~3465 cm-1 is attributed to associated ν(OH). The ClO4 ¯ and BF4 ¯ anions show strong bands at 1053 and 1095 cm-1 respectively. The X-ray single crystal study has shown that each Co(II) atom in both tri- and tetranuclear complexes has a pentagonal-bipyramidal environment. The equatorial plan is occupied by O2N3 donor atoms of Schiff base fragment, and apical position are usually occupied by water molecule, but in 3 and 4, some of water molecules are substitute with Cl or Br anions. Thus, macrocyclic ligands (42 and 56 membered) form with each metal four five membered metallocycles. The distances Co–O(cet) and Co–N are similar to those founded in the mononuclear Co(II) complexes with hydrazone Schiff base [1]. Due to CH2 group of malonic fragment each Co(II) moiety are twisted.