화학공학소재연구정보센터
Inorganic Chemistry, Vol.56, No.18, 11406-11416, 2017
Iron(III) Metallacryptand and Metallacryptate Assemblies Derived from Aroylbis(N,N-diethylthioureas)
The reaction of isophthaloylbis (N,N-diethylthiourea), H2L1, with FeCl3 center dot 6H(2)O gives the dinuclear tris-complex [Fe-2(L-1)(3)] (5), possessing a cryptand-like structure. A similar reaction with the ligand 2,6-dipicolinoylbis(N,N-diethylthiourea), H2L2, however, results in the formation of the anionic, mononuclear Fe(III). complex [Fe(L-2)(2)](-) (6), which could be isolated as its "Tl+ salt" by the subsequent addition of Tl(NO3). A tighter view to the solid state structure of the obtained product, however, characterizes compound 6 as a one-dimensional coordination polymer, in which four-coordinate Tl+ ions connect the {[Fe(L-2)(2)](-)} units to infinite chains. When Fe3+ ions and Tl+ ions are added to H2L2 simultaneously in a one-pot reaction, a different product is obtained: a cationic trinuclear complex of the composition {M subset of[Fe-2(L-2)(3)]}(+). It has been isolated as a PF6- salt and represents a {2}-metallacryptate with a nine-coordinate Tl+ ion in the central void. Structurally related products of the compositions {M subset of[Fe-2(L-2)(3)]}(PF6) (M = Na+, K+, Rb+) (8(PF6)) could be isolated from analogous reactions with alkaline salts instead of Tl(NO3). {2}-Metallacryptates with larger central voids were synthesized with the ether-spaced aroylbis(N,N-diethylthiourea) H2L3. The compounds {M subset of[Fe-2(L-3)(3)]}(PF6) (M = K+, Rb+, Tl+ or Cs+) (9(PF6)) were prepared by a similar protocol like those with H2L2 with the simultaneous addition of the metal ions to a solution of H2L3. Due to the larger spacer between the aroylthiourea units, the coordination number of the central M+ ions is 12 by six carbonyl and six ether oxygen atoms. All products were characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis. Cyclic voltammetric studies were carried out with the three representative complexes [Fe-2(L-1)(3)], {K subset of[Fe-2(L-2)(3)]}(PF6), and {K subset of[Fe-2(L-3)(3)]}(PF6). The obtained voltammograms indicate the dependence of the redox properties of the oligonuclear systems on the conjugation in the organic backbones of the ligands.