Synthesis and Functions of Oligomeric and Multidentate Dipyrrin Derivatives and their Complexes

The dipyrrin–metal complexes and especially the boron complex 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) have recently attracted considerable attention because of their interesting properties and possible applications. We have developed two unique and useful ways to extend versatility and usefulness of the dipyrrin complexes. The first one is the linear and macrocyclic oligomerization of the BODIPY units. These arrangements of the B–F moieties of the oligomerized BODIPY units provide sophisticated functions, such as unique recognition ability toward cationic guest, associated with changes in the photophysical properties by utilizing unprecedented interactions between the B–F and a cationic species. The second one is introduction of additional ligating moieties into the dipyrrin skeleton. The multidentate N2Ox dipyrrin ligands thus obtained form a variety of complexes with 13 and 14 group elements, which are difficult to synthesize using the original N2 dipyrrin derivatives. Interestingly, these unique complexes exhibit novel structures, properties, and functions such as guest recognition, stimuli-responsive structural conversion, switching of the optical properties, excellent stability of the neutral radicals, etc. We believe that these multifunctional dipyrrin complexes will advance the basic chemistry of the dipyrrin complexes and develop their applications in the materials and medicinal chemistry fields.1 Introduction2 Linear Oligomers of Boron–Dipyrrin Complexes3 Cyclic Oligomers of Boron–Dipyrrin Complexes4 A Cyclic Oligomer of Zinc–Dipyrrin Complexes5 Group 13 Element Complexes of N2Ox Dipyrrins6 Chiral N2 and N2Ox Dipyrrin Complexes7 Group 14 Element Complexes of N2O2 Dipyrrins8 Other N2O2 Dipyrrin Complexes with Unique Properties and Functions9 Conclusion