FORMATION OF ISOLATED GUEST DIMERS VS HOST GUEST COORDINATION - X-RAY CRYSTAL-STRUCTURES OF 4 CARBOXYLIC-ACID INCLUSION-COMPOUNDS FORMED BY ROOF-SHAPED AND SCISSOR-LIKE HOST MOLECULES

The crystal structures of the inclusion compounds of trans-9,10-dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid host (1) with formic acid (1a), acetic acid (1b), and propionic acid (1c) as guests, and of the coordinatoclathrate of the 1,1′-binaphthyl-2,2′-dicarboxylic acid host (2) with acetic acid as guest (2b) have been studied by single crystal X-ray diffraction. These studies show that inclusion of small carboxylic acids by carboxylic acid hosts like 1 and 2 results in formation of isolated, hydrogen-bonded guest dimers. Additional H-bond contacts between host and guest carboxylic groups are only formed in cases 1a and 2b. The dimeric acidic guest units are sitting in the cavities of the host or host-guest framework and have no other interactions than those of a weak Van der Waals' type with the neighbouring molecules. Crystal data:1·formic acid (1:2): triclinic (PĪ), a = 11.6769(6), b = 9.4067(4), c = 9.0020(4) Å, a = 81.522(4), β = 100.310(6), γ = 104.208(6)°, Z = 2, R = 0.048 for 2392 reflections;1·acetic acid (1:1): monoclinic (P21/n), a = 9.717(2), b = 14.462(2), c = 13.038(3)Å, β = 104.27(1)°, Z=4, R=0.046 for 3042 observations;1·propionic acid (1:1): monoclinic (P21/n), a = 9.897(4), b = 14.671(7), c = 13.284(7) Å, β = 105.92(6)°, Z = 4, R = 0.056 for 2302 reflections;2·acetic acid (2:3): triclinic (PĪ), a = 12.746(1), b = 17.781(2), c = 11.010(1) Å, α = 105.606(4), β = 112.992(8), γ = 81.175(6)°, Z = 2, R = 0.067 for 4375 observations. © 1990 Kluwer Academic Publishers.