REDOX-SWITCHED BONDING OF PROTONS TO FERROCENOPHANES, FERROCENE CRYPTANDS, AND SIMPLE FERROCENE AMINES - CORRELATION OF X-RAY STRUCTURAL DATA AND CYCLIC VOLTAMMETRY DERIVED REDOX POTENTIALS

To gain a better understanding of the redox-switched bonding of cations to ferrocene crown ethers, the redox potentials of 22 ferrocene nitrogen compounds, including protonated and methylated congeners, were determined. The redox potentials of the ammonium salts are shifted by between +110 and +600 mV relative to those of the neutral ferrocenes. Methylation consistently gives slightly larger positive shifts than protonation. The syntheses and X-ray crystal structures of diprotonated [1,1'-ferrocenediylbis(methylene)]bis(N-7-aza-2,3-benzo-1,4-dioxacyclononane) (orthorhombic, Pbca; a = 11.492(2) angstrom, b = 16.034(3) angstrom, c = 18.030(4) angstrom; V = 3322.3(11) angstrom3; R indices [4(sigma)I] R1 = 4.39%, wR2 = 11.5%), methylated N-methyl-2-aza-[3]-1,1'-ferrocenophane (monoclinic P2(1)/c; a = 8.396(2) angstrom, b = 12.336(2) angstrom, c = 13.414(3) angstrom, beta = 95.16(3)-degrees, V = 1383.7(5) angstrom3; R indices [4(sigma)I] R1 = 2.86%, wR2 = 7.53%), and dimethylated 7,16-(1,1'-ferrocenediylbis(methylene))-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (triclinic P1BAR; a = 10.522(2) angstrom, b = 12.664(3) angstrom, c = 13.374(3) angstrom, alpha = 82.25(3)-degrees, beta = 76.33(3)-degrees, gamma = 78.82(3)-degrees; V = 1691.3(6) angstrom3; R indices [4(sigma)I] R1 = 5.19%, wR2 = 15.4%) are described. The solid state structural data and the cyclic voltammetry derived redox potentials illustrate a linear relationship (y = -2.7 + 2.1x) x 10(2)) between the inverse iron-nitrogen separation (x) and the shifts of the redox potentials (y) and allow the unambiguous assignment of the structures of the protonated isomers of 7,16-(1,1'-ferrocenediylbis(methylene))-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane.