PUB - Publikationen an der Universität Bielefeld

The properties of radical anions and dianions of three related spatial ketones, 9-triptindanone (T1), 9,10-triptindanedione (T2), and 9, 10,11-triptindanetrione (T3), in DMF solutions containing tetraalkylammonium and lithium cations were investigated by electrochemical methods and compared with the properties of radical anions of planar 1-indanone (I1), 1,3-indanedione (I2), and 1,2,3-indanetrione (I3). Electronic communication between carbonyl groups in T2 in the presence of tetraethyl and tetrabutyl cations was found to be two times smaller than for I3, but communication decreases substantially in the presence of Li+. Radical anions T1(center dot-) and T2(center dot-) and dianion T2(2-) that form ion pairs with Li+ cations and corresponding association constants K-ass are equal to 493 +/- 38, 418 +/- 32 and (2.6 +/- 0.9) x 10(7) dm(3) mol(-1), respectively. The chelating structure of the last ion pair is supported by theoretical calculations of the distribution of the negative charge. A linear relationship between log K-ass and maximum values of the surface charge was observed. For T2, the highest equilibrium constant (log K-disp(l) = -2.387 +/- 0.064) was found for the disproportionation of the T2(center dot-) radical anion and its ion pair.