Crystal and molecular structure of unsubstituted and p-methoxy-substituted acetylbenzoylmethanatoboron difluoride

The crystal structures of two borines were solved by direct methods and refined by full-matrix least-squares procedure. 6-methyl-4-phenyl-1,3,2-(2H)-2,2-difluorodioxaborine, C10H9BF2O2 (compound 1): orthorhombic, space group Pnma, a = 12.534(2) Å, b = 7.109(2) Å, c = 10.933(2) Å, V = 974.2(3) Å3, Z = 4 and d = 1.43Mg m−3, R = 0.039 (Rw = 0.036) for 88 parameters and 752 observations with I > 3σ(I). 4-(p-anisyl)-6-methyl-1,3,2-(2H)-2,2-difluorodioxaborine, C11H11BF2O3 (compound 2): monoclinic, space group P21/m, a = 6.8889(8) Å, b = 7.071(1) Å, c = 11.695(2) Å, β = 98.55(1)°, V = 563.3(9) Å3, Z = 2 and d = 1.42Mg m−3, R = 0.039 (Rw = 0.036) for 100 parameters and 1003 observations with I > 3σ(I). The crystal structure analysis of compound 1 and 2 reveals that the difference in their absorption and fluorescence spectra, by going from solution to the solid state, reflects their packing in the crystal lattice which enables a charge transfer process to be developed between two planar molecules at ca. 3.5 Å from each other in two different but parallel planes.