One-Step Radical α–α Coupling Accesses Helical Near-Infrared 3-Pyrrolyl Boron Dipyrromethene Dimers

The direct α-α coupling of 3-pyrrolyl boron dipyrromethenes (BODIPYs) affords helical near-infrared (NIR)-active dimers in one step via a radical Pd-catalyzed process. X-ray analysis reveals Z-type helical packing stabilized by π-π stacking and hydrogen-bonding interactions. These dimers showed pronounced bathochromic absorption shifts compared to monomers and solvent-dependent charge-transfer bands up to 905 nm with fluorescence quenching. Density functional theory and time-dependent density functional theory studies confirmed the excited-state behavior, highlighting a concise route to structurally unique NIR photofunctional BODIPY assemblies.