England, U.K.), where he obtained his M.Sc. degree in Mathematics under the supervision of Professor C. A. Coulson and his D.Phil. degree in the Faculty of Physical Sciences (Theoretical Chemistry) under Professor P. W. Atkins. Since 1976, he has been a Professor at the Department of Chemistry of the University of Porto. His major contributions have been in the topology of the magnetic currentdensity field and in several aspects of the simulation of liquid/metal and liquid/liquid interfaces. He has served at different levels of responsibility in the University of Porto and as an evaluator for the national research financing agency, Fundac ¸a ˜o para a Cie ˆncia e Tecnologia. He is currently the Vice President of the Portuguese Chemical Society and the Vice Rector of the University of Porto.

Abstract. The Hückel-London-Pople-McWeeny approach to calculating ring currents in conjugated systems is considered in detail, especially the 'topological' variant of this formalism, particularly emphasised during the last five years. A step-by-step account is given of how these calculations are effected in practice, in such a way as to enable any interested reader to carry out these computations himself. The method is illustrated by using it to assess the applicability of the so-called 'Annulene-Within-an-Annulene (AWA) Rule' to 'super-ring' conjugated hydrocarbons -some in which the inner ring and outer perimeter are 'coupled', and others in which they are 'decoupled'. Compliance with the AWA model appears more probable in decoupled super-ring structures than in coupled ones. The Appendix touches on previous work involving Professor D. J. Klein, the honorand of this issue. (doi: 10.5562/cca2291)

No abstract

Abstract. Comparison is made between three different indices that characterise the individual rings of a wide range of condensed benzenoid hydrocarbons. Two of these ("π-electron partitions" and the six-centre delocalisation-indices that have been called "Δ 6 -values") have been introduced only recently as potential indicators of what might be called "local aromaticity", whilst the third ("topological π-electron ringcurrents") was suggested as a possible discriminator in this regard nearly fifty years ago. Whilst linear correlations between ring currents and π-electron partitions within certain restricted classes of ring types are good (with correlation coefficients of up to 0.998), agreement between the two indices over all classes of ring types is poor. Predictions arising from a consideration of π-electron partitions and Δ 6 -values seem, on the other hand, to be in somewhat better accord. It is therefore concluded that, despite its superficially intuitive appeal, the ring-current index is out of step both with π-electron partitions and Δ 6 -values as a general indicator of so-called "local aromaticity". (doi: 10.5562/cca1846)

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