Near‐Infrared Circularly Polarised Luminescence from Helically Extended Chiral N,N,O,O ‐Boron Chelated Dipyrromethenes

Synthetically straightforward pi-extension of helically chiral N,N,O,O-boron chelated borondipyrromethenes (BODIPYs) has been achieved by incorporation of naphthyl rings into the BODIPY 3- and 5-positions. The effect of this extension on the photophysical and chiroptical properties is strongly dependent on the regiochemistry of the naphthyl substituents (4 exo, 4 lin, 4 endo). The most helicene-like regioisomer 4 endo is a near infra-red (NIR) emitter (lambda(em)(max)=751 nm) with an emission band between 675-875 nm, displaying circularly polarised luminescence (CPL) with a luminescence dissymmetry factor, vertical bar g(lum)vertical bar=5.7x10(-3) and CPL brightness, B-CPL=27, rivalling the best NIR CPL-emitting small organic molecules reported to date.