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

摘要

The potentially tridentate ligand 2-(8-aminoquinolino)-4,6-di-tert-butylphenol, H[~1L~(AP)], has been synthesized and its coordination chemistry with Mn~(IV), Fe~(III), and Co~(III) has been investigated by X-ray crystallography, electro- and magnetochemistry, electronic, Mossbauer and EPR spectroscopies. The following complexes have been prepared [Mn~(IV)(~1L~(AP)-H_)] (1), S_t = 3/2; [Mn~(IV)(~1L~(AP)-H)(~1L~(ISQ)](PF_6))·CH_2Cl_2 (2), S_t = 1; [Fe~(III)(~1L~(ISQ))_2] (ClO_4)·0.5H_2O (3), S_t = 1/2; [Fe~(III)(~1L~(ISQ) (3,5-dtcat)]_2 (4), S_t = 0; K[Co~(II)(~1L~(IBQ))](NCS)_2 (5), S_t = 1; [Co_2~(III)(NCS)_2](~1L~(AP)-H)_2(~1L~(AP)-H)_2(AQ)] (6), S_t = 0, where (~1L~(AP)-H)~(2-) corresponds to the o-iminophenolate (2-) dianion, (~1L~(ISQ))~- is the o-iminobenzosemiquinonate(1? 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 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 [Fe~(III)(~1L~(ISQ))(3,5-dtcat)] halves. The asymmetrically ligated complex 6 contains two bridging (~1L~(AP)-H)~(2-) ligands and two diamagnetic CoIII ions. In contrast, 5 is correctly described as [CoII(1LISQ)(1LIBQ)]+ rather than [Co~(III)(~1L~(ISQ))_2]~+ since it possesses a temperature-independent magnetic moment of μ_(eff)(10-298 K) = 3.0 μ_B indicating an S_t = 1 ground state which is attained via strong antiferromagnetic coupling (|J| ≥ 200 cm~(-1)) between a high spin cobalt(II) ion (S_(Co)=3/2) and a single radical anion (S_(rad)=1/2).