Polymorphism of crystalline host–guest complexes and unsolvated hosts. Part 6. Pseudo-dimorphism of complexes between 1,1′-binaphthyl-2,2′-dicarboxylic acid and ethanol. X-Ray crystal structures of the β-form and of the unsolvated host compound

Abstract

Depending on crystallization conditions, under ordinary conditions or from solution in ethanol at 60 °C, 1,1-binaphthyl-2,2′-dicarboxylic acid (BNDA) yields pseudo-dimorphous inclusion complexes with ethanol: α-form with 1:2 and β-form with 2:1 BNDA–ethanol host–guest ratio, respectively. At 100 °C crystallized from ethanol, unsolvated BNDA is obtained. All three structures are formed as a result of packing of infinite chains which are generated by different types of H-bonding. In the α-form, BNDA molecules are incorporated in 12-membered loops involving host–guest–host (–H · · · 2G· · · H–) type H-bonds while in the β-form [triclinic (P ), a = 9.982(3), b = 13.327(3), c = 14.544(3) Å, α = 81.21(3), β = 81.21(3), γ = 88.76(3)°, Z = 4, R = 0.066 for 3713 reflections] four BNDA molecules are associated by H-bonds typical for dimers of carboxylic acids and these tetramers are incorporated into chains via the α-form mode of interaction, establishing –4H · · · 2G · · · 4H · · · 2G– type of association in the chains. In the unsolvated BNDA [orthorhombic (Pccn), a = 24.348(5), b = 11.165(2), c = 12.868(3) Å, Z = 8, R = 0.128 for 849 observations] the structure is formed by chains of carboxylic acid dimers only.