This paper presents a detailed study of the solid-state chemical, spectral, structural, and charge transport properties of the materials which result from treating nickel phthalocyanine (NiPc) with elemental iodine. A range of NiPcI* stoichiometries is obtained where x = 0 to ca. 3.0; electrical conductivities of compressed polycrystalline samples are comparable with those of other "molecular metals". Single crystals were obtained for NiPcI10. These crystallize in the space group D^-PA/mcc,

The electron-capture decay of a cobalt-57 atom triggers an Auger event resulting in the loss of several electrons from the molecule in which it is incorporated. The 14.4 keY Miissbauer emission conveys information regarding the chemical forms in which the daughter iron-57 is stabilized within IO~ 7 sec following electron capture. The electronic relaxation occurs very rapidly and several tens of e V electronic excitation energy is deposited on the molecule during charge neutralization. Emission Miissbauer spectra of cobalt-57 labeled complexes of the strong field ligands phenanthroline and ethylenediamine. namely [ 57 Co(III)(phenhl(C10.),.2H,O, [ 57 Co(III)(phen),(en)]Cl,.H,O, ["Co(III)(phen)(en),] (N0 3 h, and["Co(III)(en)3]Cl, were studied. The chelate molecules possess varying degree of conjugation. The presence of strong field ligands in the chelates made it easier to identify the high spin ionic iron species Pe H and Pe3+, which can form only as a result of fragmentation. Molecules which have no conjugation, e.g., ["Co(III)(en),l'+, or which possess small degree of conjugation like ["Co(III)(phen) (en),l' + , fragment in practically 100% of the Auger events. On the other hand, the molecules of ['7Co(III)(phen),(en)1'+ , which possess relatively higher degree of conjugation, escape fragmentation in about 20% of the events; while the highly conjugated molecules of [ 57 Co(III) (phen),]3+ seem to escape fragmentation in almost 100% of the events. One can perhaps conclude that the probability of fragmentation of a molecule as a consequence of the Auger event diminishes with higher degree of conjugation in the molecule. It is speculated that the aftereffects of the Auger event result in collective excitation of the 7T-electrons in a highly conjugated system. The de-excitation of the "plasmon" occurs rapidly, presumably through emission of a single electron or an energetic photon. The mixed ligand chelates, ['7Co(III)(phen),(en)]3+ and ['7Co(III)(phen) (en),l'+ show an interesting phenomenon. The cationic iron species formed as a result of fragmentation recombines with electron(s) to form an electronically excited cation, presumably 57Pe+2 which interacts with neighboring cobalt chelate molecules. The phenanthroline ligands are preferentially transferred onto the electronically excited cation forming ["Pe(III)(phen),l'+ quite efficiently. The transfer of ligands occur in less than 10-7 sec., as is evidenced by the manifestation of the tris-phenanthroline chelate in the emission Miissbauer spectra.

Single crystals of NiPcI 1.0 (Pc = phthalocyanine), which are composed of one-dimensional stacks of (NiPc) +0.33 molecules and chains of I 3 - molecules, exhibit metallic electrical conductivity in the stacking direction. At room temperature the mean free path of the carrier is 3.3 to 8.2 angstroms.

The design of a four-probe ac conductivity measurement system is described. The system is capable of making precision conductance measurements from 10(-8) to 10(-5) S at 20 to 200 Hz. Driven coaxial shields and a controlled current source are utilized to eliminate phase shift/attenuation errors, and make the measurement of conductances on a variety of materials a routine procedure requiring a minimum of operator intervention.

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