SYNTHESIS, MAGNETIC-SUSCEPTIBILITY, AND MOSSBAUER-SPECTRA OF IRON(III) DIMERS AND IRON(II) POLYMERS CONTAINING 2,5-DIHYDROXY-1,4-BENZOQUINONES

Several iron complexes of the dianions of 2, 5-dihydroxy-1, 4-benzoquinone (DHBQ) and 2, 5-dichloro-3,6-dihydroxy-1, 4-benzoquinone (CA, chloranilate dianion) have been prepared and studied by magnetic susceptibility and Mossbauer spectroscopic methods. Iron(II) salts react with these dihydroxybenzoquinones to give polymeric Fe(DHBQ)(H2O)2 and Fe(CA)(H2O)2. If the reaction is carried out in the presence of pyrazine, pyr, [Fe(CA)(pyr)]n and [Fe(DHBQ)(pyr)]n are obtained. Infrared spectral results are consistent with the presence of bridging bidentate pyr in these complexes and thus sheet polymers. Dimeric Fe2(DHBQ)3(H2O)4 and Fe2(CA)3(H2O)4 4H2O are obtained by reacting FeCl3 with the respective dihydroxybenzoquinone. Magnetic susceptibility vs. temperature data obtained for the polymeric materials are fit to an S=2 Heisenberg linear-chain model with [FORMULA OMMITED] Corresponding values for the CA-containing polymers are [FORMULA OMMITED] respectively. The Heisenberg-Dirac-Van Vleck S1=S2=5/2 spin exch nge model applied to the magnetic susceptibility vs. temperature data for Fe2(DHBQ)3(H2O)4 and Fe2(CA)3(H2O)4 4H2O yields J=-2.0 cm-1 and J=-1.0 cm-1, respectively. The presence of an anisotropy in the recoilless fraction (Goldanskii-Karyagin effect) is observed in the 57Fe Mossbauer spectra of the Fe(III) dimers and is substantiated by measurements on the temperature dependence of the Mossbauer parameters. © 1979, American Chemical Society. All rights reserved.