Twists and turns around a square: The many faces of Squaraine chemistry

The purpose of this account is to give an overview of the wide variety of available structures that share the common name 'squaraines', with particular attention to the results achieved by our group in the last ten years. The first section of the report is an introduction and a description of the motivation for our interest in squaraine compounds. The second section includes a survey of the history of squaraines in the scientific literature, and the third section contains a general description of their synthesis and reactivity, together with reports on our direct experiences of their use in materials science, with a focus on squaraines in third-generation photovoltaics, nonlinear optics, and photodynamic therapy. In all of the cases, we highlight the establishment of structure-property relationships directed at the design of materials with improved properties. 1 Introduction and Motivation 2 Squaraines in the Scientific Literature 3 Synthesis of Squaraine Compounds 3.1 Symmetric Derivatives 3.2 Nonsymmetric Derivatives 3.3 Bis-squaraines 3.4 Core-Substituted Squaraines 3.5 Squaraines That We Have Not (Yet) Tried To Make 4 Conclusion © Georg Thieme Verlag Stuttgart, New York.