672952-82-8Relevant academic research and scientific papers
Structure, magnetic properties and electronic structure of a nickel(II) complex with redox-active 6-(8-quinolylamino)-2,4-bis(tert-butyl)phenol
Sheepwash, Molina A.L.,Lough, Alan J.,Poggini, Lorenzo,Poneti, Giordano,Lemaire, Martin T.
, p. 2 - 7 (2016)
We report the preparation and electronic structure of a nickel complex 2 containing ligand 6-(8-quinolylamino)-2,4-bis(tert-butyl)phenol 1. The complex is neutral, six-coordinate (pseudo-octahedral) and homoleptic containing two equivalents of 1 and no counteranions. The bond distances measured by single crystal X-ray diffraction studies suggest that the two equivalents of 1 are bound as mono-anion radicals (iminosemiquinone oxidation state). Variable temperature magnetic susceptibility data indicates a quintet (S = 2) ground state for this complex resulting from ferromagnetic coupling between Ni2+ and the coordinated radical anions. Cyclic voltammetry experiments and UV-Vis-NIR spectroscopy indicate the presence of coordinated iminosemiquinone radicals, and these experimental results are corroborated by density functional theory calculations, which support the proposed assignments. Complex 2 is easily oxidized in the presence of ferrocenium hexafluorophosphate or aerial dioxygen to produce a complex with closed shell ligands and spectroscopic features characteristic of ortho-iminoquinone ligands.
Coordination chemistry of 2-(8-aminoquinolino)-4,6-di-tert-butylphenol with manganese(IV), iron(III), and cobalt(II/III): N,O-coordinated o-iminobenzosemiquinonate(1-) π radical monoanions vs. o-iminophenolate(2-) dianions
Min, Kil Sik,Weyhermueller, Thomas,Wieghardt, Karl
, p. 178 - 186 (2007/10/03)
The potentially tridentate ligand 2-(8-aminoquinolino)- 4,6-di-tert-butylphenol, H[1LAP], has been synthesized and its coordination chemistry with MnIV, FeIII, and CoIII has been investigated by X-ray crystallography, electro- and magnetochemistry, electronic, Moessbauer and EPR spectroscopies. The following complexes have been prepared [MnIV(1LAP - H)2] (1), St = 3/2; [MnIV(1LAP - H) (1LISQ)](PF6)·CH2 Cl2 (2), St = 1; [FeIII(1LISQ)2] (ClO4)·0.5H2O (3), St = 1/2; [FeIII(1LISQ) (3,5-dtcat)]2 (4), St = 0; K[CoII(1LISQ)(1 LIBQ)](NCS)2 (5), St = 1; [Co2III(NCS)2(1 LAP - H)2(AQ)] (6), St = 0, where (1LAP - H)2- corresponds to the o-iminophenolate(2-) dianion, (1LISQ)- is the o-iminobenzosemiquinonate(1-) π radical derivative of the ligand H[1LAP], (1LIBQ)0 is the neutral iminobenzoquinone ligand, and 3,5-dtcat is 3,5-di-tert-butylcatecholate(2-) and N,N-coordinated (AQ) is 8-aminoquinoline. It is shown that the π radical anions in 2, 3, 4 couple antiferromagnetically to the respective paramagnetic metal ion. Complex 4 is a dinuclear neutral complex with weak antiferromagnetic coupling between two [FeIII(1LISQ)(3,5-dtcat)] halves. The asymmetrically ligated complex 6 contains two bridging (1LAP - H)2- ligands and two diamagnetic CoIII ions. In contrast, 5 is correctly described as [CoII (1LISQ)(1LIBQ)]+ rather than [CoIII(1LISQ)2]+ since it possesses a temperature-independent magnetic moment of μeff (10-298 K) = 3.0 μB indicating an St = 1 ground state which is attained via strong antiferromagnetic coupling (|J| ≥ 200 cm-1) between a high spin cobalt(II) ion (SCo = 3/2) and a single π radical anion (Srad = 1/2).
