An X-ray crystallographic study of the inclusion properties of additionally dimethylated members of the 2′-hydroxy-2,2,4-trimethylflavan host series

Consideration of the shape and hydrogen bonding pattern of anentire guest unit, in the known 2:1:2 complex of 2′-hydroxy-2,4,4,7,4′-pentamethylflavan (1) with 1,4-dioxan and water, has indicated a structurally compatible guest,trans-1,4-bis(hydroxymethyl)cyclohexane (3b) which is selectively clathrated from a mixture with itscis isomer (3a). The new complex is triclinic, space group,P \(\bar 1\) , witha=8.137(1),b=9.106(1),c=14.552(2) Å, α=93.56(1), β=94.08(1), γ=98.62(1)°, and two host and one guest molecule in the unit cell. A novel hydrogen bonded host-guest arrangement has also been found for host (1), involving ethanol and piperazine triclinic, space groupP \(\bar 1\) , witha=8.438(1),b=10.252(1),c=14.052(1) Å, α=71.28(1), β=89.72(1), γ=83.88(1)δ]; while for the 1:1 ether adduct of (1) the triclinic unit cell, space groupP \(\bar 1\) , is approximately doubled in volume a=8.309(2),b=10.546(3),c=26.664(6) Å, α=102.10(2), β=100.48(2), γ=81.04(2)°], there now being two crystallographically independent host-guest units involving ?OH·OEt₂ hydrogen bonds of length 2.71(1) Å and 2.77(1)Å. In the 2:1 complex of the isomeric host 2′-hydroxy-2,4,4,6,5′-pentamethylfavan (2) withN, N′-dimethylpiperazine (5) triclinic space groupP \(\bar 1\) , witha=7.411(1),b=10.143(3),c=15.109(3)Å, α=98.73(2), β=88.30(1), γ=109.72(2)°] the centrosymmetric chair-shaped guest molecule is clamped by two axially oriented ?OH...N hydrogen bonds of length 2.759(3)Å.