It is a pleasure to introduce this issue devoted to the theme of aromaticity, and to comment on some historical considerations and criteria for Special Topic features in Pure and Applied Chemistry (PAC). The core business of the Journal is to publish papers based upon authoritative lectures presented at IUPACsponsored conferences, symposia, and workshops, and to publish IUPAC Recommendations and Technical Reports.Special Topics were originally conceived as a tool to promote new and emerging principles and practice in all branches of chemical sciences, through the medium of works based upon inaugural events or special IUPAC projects. The latter projects were sometimes driven by Divisional or individual initiatives within the Union, but it has come to be recognized that regular IUPAC-sponsored series of international events also offer rich scope for highlighting important advances in specialized subject areas. This is reflected in the recent history of Special Topic issues. The criteria for selection have emerged as timeliness and strong evidence of support and interest from the community of authors and readers. Publication projects arising from the Special Topics initiative generally continue to achieve gratifyingly favorable citation profiles, and thereby support the view that they fulfil an important and distinctive need in current review literature.Proceedings of most events in the International Symposia in Novel Aromatic Compounds (ISNA) series have routinely been published in PAC for some 40 years, and offer convincing evidence of sustained interest in the chemistry and properties of aromatic compounds, and growing interdisciplinary interfaces with materials sciences and nanotechnologies. The series was inaugurated in Sendai, Japan (1970) as an International Symposium on the Chemistry of Nonbenzenoid Aromatic Compounds. After a second meeting four years later, the current, more inclusive series title emerged as a prescient change that heralded astonishing advances in the role of aromaticity in new-age compounds and materials. The early three- to four-year intervals between events have recently diminished to two years, in apparent response to growing topicality and urgency. A case for Special Topic coverage of ISNA-13 is thus persuasively supported by the community that it serves, as well as the strong citation profiles of collections arising from recent events in the series.The passage to publication for this project has been materially supported by enthusiastic authorship cooperation and timely submission of manuscripts, and it is a particular pleasure to pay tribute to the Chair, Prof. François Diederich, and Co-chair, Prof. A. Dieter Schlüter of the Organizing Committee, and for their roles in the compilation of the scientific program and their exceptional devotion in contributing actively to overseeing peer review of the manuscripts. This collection will serve as an overview of current advances and future opportunities in the field of aromatic chemistry, and an enduring and representative record of an outstanding event.James R. BullScientific Editor
170 Years of “Lock-and-Key”: Genital Morphology and Reproductive Isolation
