Synthesis, structure, spectral and electron-transfer properties of octahedral-[CoIII(L)2]+/[ZnII(L)2] and square planar-[CuII(L){OC(=O)CH3}] complexes incorporating anionic form of tridentate bis(8-quinolinyl)amine [N1C9H6–N2–C9H6N3, L−] ligand
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Title |
Synthesis, structure, spectral and electron-transfer properties of octahedral-[CoIII(L)2]+/[ZnII(L)2] and square planar-[CuII(L){OC(=O)CH3}] complexes incorporating anionic form of tridentate bis(8-quinolinyl)amine [N1C9H6–N2–C9H6N3, L−] ligand
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Creator |
MAITI, DEBABRATA
PAUL, HIMADRI CHANDA, NRIPEN CHAKRABORTY, SOMA MONDAL, BIPLAB PURANIK, VEDAVATI G LAHIRI, GOUTAM KUMAR |
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Subject |
stoichiometry
geometry crystal structure x-ray diffractometers |
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Description |
The reaction of bis(8-quinolinyl)amine [N1C9H6–N2H–C9H6N3, LH] with CoII(ClO4)2 · 6H2O in methanol under aerobic conditions results in a new class of [CoIIIN6]+ (1+) chromophore incorporating an sp2-amido nitrogen center (N2) in the ligand frame. During the course of the reaction, the cobalt ion has been oxidized from its starting +2 oxidation state to +3 state in 1. The reaction of LH with the Cu-acetate yields monomeric square planar complex, [CuII(L){OC(=O)CH3}] (2). The same copper complex 2 is also obtained from Cu(ClO4) · 6H2O in presence of CH3COONa as base. On the other hand, the reaction of Zn(ClO4) · 6H2O with LH results in octahedral complex ZnII(L)2 (3). The Cu(II) complex 2 displays a four-line EPR spectrum at room temperature. Crystal structure of the free ligand (LH) shows that the amine proton [N(2)H] is hydrogen-bonded with the terminal quinoline nitrogen centers [N(1) and N(3)]. The crystal structure of 1 confirms the meridional geometry of the complex cation. The square planar geometry of copper complex 2 is confirmed by its crystal structure where the acetate function behaves as a monodentate ligand. The free ligand, LH, is found to be highly acidic in acetonitrile–water (1:1) medium and correspondingly the amine proton (NH) readily dissociates leading to its L− form even in absence of any external base. The pKb value of L− is determined to be 2.6. Both cobalt and copper complexes do not show any expected spin-allowed d–d transitions, possibly have masked by the intense charge-transfer transitions. However, in case of cobalt complex 1, one very weak unusual spin-forbidden 1A1g → 3T1g transition has been observed at 935 nm. The quasi-reversible cobalt (III)⇋cobalt(II) reduction of 1 is observed at E0, −1.0 V versus SCE.
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Publisher |
Elsevier
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Date |
2009-04-03T09:04:27Z
2011-11-25T20:35:31Z 2011-12-26T13:08:09Z 2011-12-27T05:56:09Z 2009-04-03T09:04:27Z 2011-11-25T20:35:31Z 2011-12-26T13:08:09Z 2011-12-27T05:56:09Z 2004 |
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Type |
Article
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Identifier |
Polyhedron 23(5), 831-840
0277-5387 http://dx.doi.org/10.1016/j.poly.2003.11.053 http://hdl.handle.net/10054/1118 http://dspace.library.iitb.ac.in/xmlui/handle/10054/1118 |
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Language |
en
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