Competition between hydrogen and halogen bonding in the structures of 5,10-dihydroxy-5,10-dihydroboranthrenes.
X-ray crystallographic and computational studies are reported for a series of boranthrenes, substituted with halogen atoms. The role of competitive hydrogen (O-H...O, O-H...F, C-H...O) and halogen (Cl...Cl, O...Br, F...F) bonding interactions on the molecular arrangement in the crystal structures is discussed. The structural analysis and calculations reveal that the O-H...O hydrogen bond in the unsubstituted derivative 5,10-dihydroxy-5,10-dihydroboranthrene, C12H10B2O2, is of moderate strength (ca -20 kJ mol(-1)), but weaker than that in the related thiophene derivative 4,8-dihydro-4,8-dihydroxy-p-diborino[2,3-b:5,6-b]dithiophene, C8H6B2O2S2 (ca -40 kJ mol(-1)). This is due to shielding of the OH group by the H atoms in the β-position of the boranthrene unit. Structural diversity derived from the flexibility of the O-H...O hydrogen bond facilitates the occurrence of other competitive interactions. For instance, in the 1,6-difluoro derivative, C12H8B2F2O2, the crystal packing results from O-H...F and F...F interactions. In turn, the 1,6-dibromo derivative, C12H8B2Br2O2, is dominated by Br...O halogen-bond interactions. In the most interesting case, the 1,6-dichloro derivative, C12H8B2Cl2O2, molecular disorder leads to the formation of two different supramolecular arrangements co-existing in the crystal lattice, one based on the Cl...Cl and C-H...O bonds, and the other stabilized by O-H...O hydrogen bonds. Calculations performed with density-functional theory (DFT; CRYSTAL09) and PIXEL methodologies show that both lattices are characterized by similar energy values (ca -100 kJ mol(-1)). A mixed arrangement with random or short-range-ordered molecular orientations can also be expected.
Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warszawa 00-664, Poland.
Krzysztof
K
Durka
Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warszawa 00-664, Poland.
Sergiusz
S
Luliński
Department of Chemistry, University of Warsaw, Pasteura 1, Warszawa 02-093, Poland.
Katarzyna N
KN
Jarzembska
Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warszawa 00-664, Poland.
Jaromir
J
Smętek
Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, Warszawa 00-664, Poland.
Janusz
J
Serwatowski
Department of Chemistry, University of Warsaw, Pasteura 1, Warszawa 02-093, Poland.
Krzysztof
K
Woźniak
X-ray structural analysis; boranthrenes; energy calculations; halogen bonding; hydrogen bonding