STM images with computer-generated structures using Macro-Model support the conclusion that the image contrast is dominated by the benzyl groups on the circumference of the polypeptide molecules.Acknowledgment. We thank Professor W. Clark Still for both helpful discussions and the use of his molecular modeling program and Professor Koji Nakanishi for the use of his computing facilities. This work was supported by The Joint Services Electronics

We report the preparation, crystallization, and solid-state characterization of a spiro-biphenalenyl radical. The crystal structure shows that the radical is monomeric in the solid state and without intermolecular contacts that fall within the van der Waals atomic separation. Magnetic susceptibility measurements show Curie behavior (1 spin per molecule) throughout the temperature range 10−400 K, confirming the presence of noninteracting spins in the solid. The compound shows a room-temperature conductivity of σ = 0.05 S/cm, the highest yet for a neutral radical conductor. We suggest that the ground state of the radical corresponds to a degenerate Mott−Hubbard insulator. We postulate the presence of delocalized energy bands that are responsible for the transport properties but that are separated from the insulating ground state by an energy gap corresponding to the on-site Coulombic correlation energy. Given the presence of isolated molecules in the crystal lattice, the magnitude of the conductivity, the finding of band transport, and the width of the conduction band (0.5 eV) are unprecedented.

[reaction: see text] Highly stable NH salicylideneanilines have been prepared by reaction of 1,3,5-triformylphloroglucinol with aniline derivatives. The NH form was confirmed by X-ray crystallographic data, as well as by NMR studies. A convenient one-step synthesis of triformylphloroglucinol is also reported.

We have investigated novel bifunctional chelate alternatives to the aminocarboxylate macrocycles NOTA (N(3)O(3)) or DOTA (N(4)O(4)) for application of radioisotopes of Ga to diagnostic nuclear medicine and have found that the linear N(4)O(2) chelate H(2)dedpa coordinates (67)Ga quantitatively to form [(67)Ga(dedpa)](+) after 10 min at RT. Concentration-dependent coordination to H(2)dedpa of either (68)Ga or (67)Ga showed quantitative conversion to the desired products with ligand concentrations as low as 10(-7) M. With (68)Ga, specific activities as high as 9.8 mCi nmol(-1) were obtained without purification. In a 2 h competition experiment against human apo-transferrin, [(67)Ga(dedpa)](+) showed no decomposition. Two bifunctional versions of H(2)dedpa are also described, and these both coordinate to (67)Ga at RT within 10 min. Complete syntheses, characterizations, labeling studies, and biodistribution profiles of the (67)Ga complexes are presented for the new platform chelates. The stability of these platform chelates is higher than that of DOTA.