Triply N-Confused Hexaphyrins: Near-Infrared Luminescent Dyes with a Triangular Shape

摘要

Molecular shape confines the spatial distribution of electrons that govern the properties of a molecule.In general, the larger the size, the more flexibility the molecule can have. In the field of expanded porphyrins, understanding the shape-property relationship is becoming more important because of their potential applications as functional dyes that absorb and emit light in the near-infrared (NIR) region. However, the large flexibility of the molecules results in them displaying a variety of structures with many conformers and tautomers, and this frequently makes analysis of their shape-property relationship difficult. Thus, it is desirable to fix the molecular shape by controlling, for example, the linker, position of the substituents, number of π electrons, protonation, metalation, and components of the rings. In the case of hexa-phyrin(1.1.1.1.1.1), where six pyrrole rings and meso carbon atoms are connected alternately, the compound has been shown to display various conformations, such as a dumbbell, rectangle, and figure-of-eight, depending on the substituents on the framework. Structural flexibility of hexaphyrins, or more generally, expanded porphyrins, is usually accompanied by inversion or rotation of the constituent pyrrole rings. Thus, regulation of pyrrole ring inversion is a way to force the molecule into a stable shape.