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A series of tris(3-hydroxy-2-methyl-4-pyridinonato)aluminum(III) and -gallium(III) complexes have been prepared and characterized wherein the pyridinones have a variety of substituents at the ring nitrogen atom (H, CH3, n-C6HH). They have been studied by a number of techniques including variable-pH 27Al NMR, variable-temperature NMR, and single-crystal X-ray diffraction. The complexes M(C7H8N02)3• 12H20 (¿V-methyl) are isostructural for M = Al and Ga, crystallizing in the trigonal space group with the following crystal parameters for Al (Ga): a = 16.600 (2) (16.6549 ( 6)) Á, c = 6.877 (1) (6.8691 (4)) Á, Z = 2. The data were refined by using 1662 (1653) reflections with I > 3 [»(/)] to R and Rw values of 0.045 (0.047) and 0.051 (0.055), respectively. They form rigidly fac geometries with extensive hydrogen bonding to channels of water molecules, and this involves every available O atom in the unit cell. The resulting structure resembles an exclusion complex; hence, we have termed it an exoclathrate. The Al and Ga complexes with N-H and N-CH3 are water soluble with some lipophilicity and exhibit a wide window of stability to hydrolysis. The dominance of hydrogen bonding is demonstrated in the solid-state structures and is also significant to the solution properties in water. Some of these compounds are being employed in biological studies of A1 neurotoxicity and experiments in 67Ga localization.

Atomic hydrogen provides a unique test case for computational electronic structure methods, since its electronic excitation energies are known analytically. With only one electron, hydrogen contains no electronic correlation and is therefore particularly susceptible to spurious self-interaction errors introduced by certain computational methods. In this paper we focus on many-body perturbationtheory (MBPT) in Hedin's GW approximation. While the Hartree-Fock and the exact MBPT self-energy are free of self-interaction, the correlation part of the GW self-energy does not have this property. Here we use atomic hydrogen as a benchmark system for GW and show that the selfinteraction part of the GW self-energy, while non-zero, is small. The effect of calculating the GW self-energy from exact wavefunctions and eigenvalues, as distinct from those from the local-density approximation, is also illuminating. PACS numbers: 31.25.Jf, 31.15.Lc, 31.15.Ar I. INTRODUCTIONAb initio many-body quantum mechanical calculations are crucially important to our understanding of the behavior of atomic, molecular and condensed matter systems. It is well known that prediction of the behavior of these systems requires the description of electronic correlation. Whilst density-functional theory (DFT) in the local-density approximation (LDA) does this with startling success in many cases, it does so at the expense of a non-physical electron self-interaction. For delocalized electron systems this self-interaction becomes negligible, but in atomic or strongly localized electronic systems it plays an important role. If one is interested in the calculation of quasiparticle excitation spectra, manybody perturbation-theory (MBPT) is formally a correct way to proceed. For solids, MBPT in Hedin's GW approximation [1] has become the method of choice, but it is also increasingly being applied to molecular systems and clusters. The GW self-energy can be decomposed into correlation and exchange parts, where the latter is the same as the Fock operator encountered in Hartree-Fock theory and thus self-interaction free. While the exact self-energy must also be free of self-interaction, the correlation part of the GW self-energy does not have this property. To investigate the influence of self-interaction in the GW approach the hydrogen atom provides an ideal case, because the exact solution is known analytically.Hydrogen in its solid phase has previously been studied within the GW approximation by Li et al.[2], who * Present address:

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A series of 3-hydroxy-2-methyl-4(1H)-pyridinones has been prepared with the substituents H, CH3, n-C6HII, and CH2CH2NH2 at the ring N. The dipyridinone 1,6-bis(3-hydroxy-2-methyl-4( 1 H)-pyridinn 1yl)hexane has also been synthesized. The products with H and CH3 substituents have been studied by single crystal X-5ay diffraction. Crystals of 3-hydroxy-2-methyl-4-pyridinone are monoclinic, a = 6.835 1(4), b = 10.2249(4), c = 8.6525(4) A, P = 105.215(4)", Z = 4, space group P21 n and those of 3-hydroxy-l,2-dimethyl-4-pyridinone are orthorhombic, a = 7.3036(4), b = 13.0490(6), c = 13.7681(7) 9' , Z = 8, space group Pbca. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.037 and 0.044 for 914 and 857 reflections with I 2 3 a ( I ) , respectively. Bond lengths and angles in the two compounds were normal. All the compounds have been studied by mass spectrometry, and by infrared and proton nmr spectroscopies. The importance of hydrogen bonding to both the solution and solid state properties of these compounds has been confirmed by these techniques. Introduction There is considerable literature on 4-pyridinones (1) but a limited amount of information is available on the 3-hydroxy-4-pyridinones. Much of the preparative work on the latter is scattered and inaccessible, having been reported in the form of patents, and we discovered when we became interested in them, that a considerable effort was required before we had the requisite compounds for further study.As part of a project to examine neutral water soluble complexes of aluminum, gallium, and other metals, we have prepared and characterized a series of N-substituted-3-hydroxy-2-methyl-4-pyridinones (1) to be used as ligands for these metals in aqueous solution. Recently, there has been significant interest in these compounds, and the related pyrones (e.g. malt01 2), as binding groups for various' metal ions. This