O-Capped Heteroadamantyl-Substituted Hydrazines and Their Oxidation Products

The mixed valence bishydrazine radical cation 6(+), obtained by oxidation of 2,6-bi-(2'-oxa-6'-azaadamantane-6'-yl)-2,6-diazaadamantane-2,6-diyl (6) with silver or nitrosonium salts, has been prepared and studied. 6 is obtained along with lesser amounts of the trishydrazine, some of the tetrahydrazine, and apparently traces of the pentahydrazine upon reaction of deprotonated 2-oxa-6-azaadamantane with 2,6-dichloro-2,6-diazaadamantane. The EPR spectrum of 6(+) shows that its charge is localized on one hydrazine unit on the EPR time scale. It shows a Hush-type Robin-Day class 11 mixed valence band in its optical spectrum despite the fact that the nitrogen lone pairs are held in a perpendicular geometry that would lead to no electronic interaction between the nitrogen atoms that are separated by only four a bonds if its nitrogens were planar. The electron transfer distance that is estimated from the calculated dipole moment of 6(+) is the same as that obtained using the average distance between the electrons of the triplet state of the dication 6(2+), calculated from its dipolar EPR splitting, as a model for the electron transfer distance of 6(+), 3.7 angstrom. Using Hush's Gaussian approximation for the optical spectrum with this electron transfer distance produces an estimate of the electronic coupling V(ab) through the saturated bridge of about 400 cm(-1), which is consistent with the observed EPR spectrum of 6(+). From the observed dipolar splitting, the trishydrazine diradical dication has its remote hydrazine units oxidized, although the monocation presumably forms at the central hydrazine unit, which lacks substitution by the more electron-withdrawing oxygen atoms.