Preface 1950-2000: Fifty years of theoretical research on porphyrins
Despite its long and distinguished history, porphyrin chemistry continues to be an amazingly vibrant area of research. This is particularly true of current theoretical research on porphyrins, so much so that it may surprise many that the first quantum chemical calculations were carried out more than half a century ago [1]. This piece of trivia provided a good excuse for assembling a special issue of the Journal of Porphyrins and Phthalocyanines commemorating 'Fifty Years of Theoretical Research on Porphyrins.' Some of the serious motivation behind this project was as follows.
Constraints of time did not permit myself [2] and other authors of The Porphyrin Handbook (Volume 7, Physical and Theoretical Characterization) to achieve as complete a coverage of the electronic structural aspects of porphyrins as we would have liked. I believe that the articles in this volume achieve some of that missing coverage. Another goal was to showcase the accomplishments of quantum chemistry with respect to some major topics of interest to porphyrin chemists, e.g. excited states, heme-diatomic interactions, ligand noninnocence, etc. Yet a third goal was to collect within one volume a mix of electronic structure-related articles from both theoreticians and experimentalists to highlight the increasing complementarity of computational and experimental research. I believe that these goals have indeed been met, for which I sincerely thank all the contributors to this volume, each of whom responded most kindly and enthusiastically to my invitation to contribute an original or review article. Here are some specifics about the articles in this issue.
For me, it is a particular honor to have as the opening paper in this issue an article by