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This review outlines the work to date concerning the mysteries of both the large optical effects and the bonding mechanisms involved with intercalation in heavy metal iodide systems. Such a system exhibits unusual shifts of the optical band edge to higher energies upon intercalation. The shift depends on which host-guest combination is used. Several models have been developed to describe this system. The bonding mechanism for this system is not clear because some data appear to support a model based on a polarization interaction between the guest and host material whereas other data support a charge transfer or quantum confinement model. There appear to be several different systems being formed by intercalation of the same substances that have different stoichiometry. This riddle may be solved by investigations of the particular methods of intercalation.

temperatures (fast outer-sphere exchange), and the difference ~doutcr = ß « is the limiting value for inner-sphere fast exchange. If (7i"""/H,0-Ni bond is truly constant, then ñ = 6mner(°bsd)/3.90. If » is <5, at least some Ni(H20)4-(CH3OH)22+ must be present. An unique distribution cannot be obtained from these data. The results require that any differences in properties of the species present be small as the data can be well fit with the assumption of only one average single species with 4.91 H20/Ni. The constancy of Q from 119 to 160 °C also suggests that zz(H20) is insensitive to temperature. Otherwise, a considerable number of fortuitous compensations would have to be present to account for the data. Jambor5 has obtained a value of ca. -3 kcal mol"1, using spectrophotometry, for addition of one CH3OH to hexaaquonickel(II). This result, if correct, would make «(H20) at our temperatures even larger than the value 5.8 found by Rorabacher2 at lower temperature. With «(H20) near 5, our results are in fact going to be quite insensitive to the fCs and AH0's for formation of mono-and bis(methanol) complexes

Preparation and Spectral and Electrochemical Characterization of Dirhodium(II) Complexes with Bridging 1,8-Naphthyridine Ligands: 2,7-Bis(2-pyridyl)-l,8-naphthyridine, 5,6-Dihydrodipyrido[2,3-h:3/,2/-y'][l,10]phenanthroline, 2-(2-Pyridyl)-l,8-naphthyridine, and 1,8-Naphthyridine. X-ray Crystal Structure of Tris(M-acetato)(2,7-bis(2-pyridyl)-l,8-naphthyridine)dirhodium(II) Hexafluorophosphate

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