Pyrrolylquinoline-BF2 and BPh2 BODIPY-Type Analogues: Synthesis, Structural Analysis and Photophysical Properties

Two new pyrrolylquinoline-substituted heteroaromatic-containing compounds bearing a central boron bridge have been prepared by a short, high-yielding sequence consisting of Suzuki-coupling of 8-bromoquinoline and N-Boc 2-pyrroleboronic acid, thermolytic tert-butyloxycarbonyl deprotection, and subsequent boron chelation (either using boron trifluoride or triphenylborane). Both derivatives display longer wavelength absorption maxima (lambda(abs)(max)) than a previously reported indolopyridine-BPh2 analogue, in agreement with the smaller HOMO-LUMO energy gap predicted by DFT quantum chemical calculations. Both of the pyrrolylquinoline-boron chelates display weak emission (quantum yields 0.3-0.9%) and the BPh2 complex displays a very broad, long-wavelength emission (lambda(em)(max) = 715 nm, MeCN), which may be due to dimer emission and results in a large pseudo-Stokes' shift (7753 cm(-1)) for this compound.

Automated summary

Two new pyrrolylquinoline-substituted heteroaromatic-containing compounds with a central boron bridge were synthesized via a high-yielding sequence. Both derivatives exhibit longer wavelength absorption maxima compared to a previously reported analogue, with weak emission and a large pseudo-Stokes' shift observed in one of the complexes.