Guest-exchange and guest-release via gas-solid contact in clathrate crystals based on 2,5-bis(9-hydroxyfluoren-9-yl) thieno[3,2-b] thiophene as a host compound

The host compound 2,5-bis(9-hydroxyfluoren-9-yl)thieno[3,2-b]thiophene (1) afforded clathrate crystals represented by the formula (1)(guest)(2) for th e guests EtOH, n-PrOH, and i-PrOH. Their X-ray crystal analyses revealed th at the host frameworks are isostructural. The guest molecules, which are em bedded in a channel-type of host void, were exchanged with other guest spec ies by vapor contact. Upon exposure of these crystals to methanol vapor, gu est elimination was induced to give the guest-free host 1 crystal [beta-for m, P (1) over bar, a = 13.111(4), b = 13.724(3), c = 9.766(3) Angstrom, alp ha = 97.11(2), beta = 98.64(3), gamma = 64.56(2)degrees, V = 1565.3(8) Angs trom(3)]. The crystal thus obtained is a polymorphic form of the guest-free 1 crystal which is obtained by recrystallization from dichloromethane [alp ha-form, P2(1)/n, a = 17.403(3), b = 20.654(4), c = 8.695(1) Angstrom, beta = 99.73(1)degrees, V = 3080.4(9) Angstrom(3)]. Once the guest molecules ha ve been lost, gas-sorptive enclathration was not accomplished for either of these polymorphic host crystals; host 1 does not act as an apohost.