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ESR spectra of copper complexes have been interpreted by means of molecular orbital theory, and the ``covalent'' character of both σ and π bonds have been discussed for a variety of compounds. Overlap integrals have been considered in a consistent manner in treating σ bonds. Particular attention has been given to Cu phthalocyanine and several of its derivatives. The in-plane π bonding may be as important in determining the properties of a Cu complex as is the in-plane σ bonding.

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The Stokes–Einstein and Stokes–Einstein–Debye relations hold well in nonsupercooled liquids; however, sizeable deviations from the former appear in supercooled liquids, leading to a ‘‘decoupling’’ of translational diffusion from viscosity and reorientational relaxation. We attribute this breakdown and this ‘‘decoupling’’ to the existence of structured domains in the supercooled liquid.

A theory of ESR linewidths for substances in which the magnetic anisotropy is small and for which the orbital magnetism has been essentially quenched is developed. Nuclear quadrupole moments, zero field splittings, anisotropic Zeeman terms, and intramolecular electron-nuclear dipolar interactions, as well as motional and exchange effects are considered in the strong field case. The theory is developed in a manner that is particularly adaptable to the study of liquids but it is also applied to crystals since the resulting equations, though only applicable for small anisotropies, are particularly simple. The theory provides an extension of previous theories on ESR spectra in liquids. Several applications of the theory are discussed with particular emphasis on V4+ chelates. The theory of exchange in liquids, a phenomenon which is complicated by the noncommutivity of the motional and exchange Hamiltonians is considered in special detail. It is shown that this theory can be used to explain Hausser's results—the existence of an optimum viscosity for the observation of hyperfine structure.

It has long been appreciated that both temperature and density play roles in determining the extremely super-Arrhenius, low-temperature behavior of the viscosity and long α-relaxation times that characterize fragile supercooled liquids. But what has not been generally appreciated, and what we believe we have established (by focusing on a model-free analysis in terms of temperature and density, rather than upon temperature and pressure) is that over the range of densities and temperatures spanned by the experiments carried out at 1 atm pressure, temperature is the dominant control variable. This information is essential input to the formulation of a theory or model of the long-time dynamics of low-temperature fragile liquids, and it suggests a focus on activated dynamics rather than on free volume. This work indicates that, except possibly at very high densities (very high pressures), the glass transition is not a result of congestion due to a lack of free volume.

We have observed what appears to be a first-order phase change from deeply supercooled liquid triphenyl phosphite at 1 atm to a rigid, "apparently" amorphous phase which we denote as the "glacial phase". This is a new, crisper, and rather different addition to the examples of polyamorphism that have recently been studied. In order to "deeply" supercool the liquid, it must be quick-quenched to a low temperature: if heated slowly, but immediately, it crystallizes; if allowed to stand for several hours at low temperature, it transforms to the glacial phase; and if subsequently heated it, too, crystallizes, but at a higher temperature than that for liquid crystallization. The glacial phase can be clearly distinguished from both the normal crystal and the ordinary glass. We propose a model for the formation of this "apparently" amorphous glacial phase.

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