Halogen···halogen versus OH···O supramolecular interactions in the crystal structures of a series of halogen and methyl substituted cis-9,10-diphenyl-9,10-dihydroanthracene-9,10-diols1

The crystal structures of four p-phenyl-substituted cis-9,10-diphenyl-9,10-dihydroanthracene-9,10-diols, carrying chloro- (1), bromo- (2), iodo- (3) and methyl substituents (4), respectively (with 2 being a previously described compound), have been studied in order to compare the effects of these substituents on the crystalline architecture. Ordinary O–H···O hydrogen bonds govern the packing of the methyl-substituted molecules in 4, whereas interhalogen interactions in competition with conventional hydrogen bonds direct the crystalline arrangement of the halogenated homologues 1–3, yielding somewhat lower symmetry and lower packing coefficient for the latter crystals. All short (Cl···Cl<3.49, Br···Br<3.46, I···I<3.86 Å) interhalogen interactions are symmetrical type-I connections with more or less “head-on” directions, where increasing size of the connected halogens seems to increase a tendency towards deviation from the ideal head-on geometry. Substitution of methyl in 4 for chlorine in 1 changed the crystal packing significantly, whereas the chloro-substituted derivative (1) was found to form a crystal isostructural with its bromo-substituted analogue (2). Two of the short interchloro distances in 1 were found to be slightly longer than the corresponding ones in the bromo analogue. This is rather unusual, although extensive inspection of the literature and the Cambridge Structural Database yielded five more examples of pairs of organic chloro and bromo analogues, forming isostructural crystals with direct Cl···Cl contact distances equal to or slightly longer than the corresponding Br···Br distances.