8-Aryl substituted boron-dipyrromethene dyes: crystal structures and computational studies

The single crystal X-ray diffraction structures of 8-[4-(acetoxymethyl)]phenyl-2,6-diethyl-4,4-difluoro-1,3,5,7-tetramethyl-3a,4a-diaza-4- bora-s-indacene (PAr1Ac, 4) and 8-[4-(3-acetoxypropyl)]phenyl-2,6-diethyl-4,4-difluoro-1,3,5,7-tetramethyl-3a,4a-diaza-4-bora-s-indacene (PAr3Ac, 5) are reported. Although, these two compounds are quite similar, their solid structures are quite unlike, showing remarkable differences in the crystal system, number of molecules in the asymmetric unit, molecular conformation, and supramolecular packing motif. The structures obtained from the X-ray diffraction analysis have been used as starting geometries for quantum chemical calculations (overall energy, HOMO and LUMO, dipole moment, and molecular electrostatic potential). Overall, these results are starting points to understand the photophysical and chemical properties of the so-called ‘pyrromethene’ dyes. q 2004 Elsevier B.V. All rights reserved.