Pyridine and Morpholine Inclusion by a Binaphthyl Host

Abstract

The host compound 3,3′-bis (9-hydroxy-9-fluorenyl)-2,2′-binaphthyl formed three inclusion compounds H.2PYR (1), H.2MOR (2) and H.PYR/MOR (3) with pyridine (PYR), morpholine (MOR) and their equimolar mixture, respectively. 1 crystallized in the triclinic space group P-1 with a = 11.4201(2), b = 13.2910(2), c = 16.2395(2) Å, α = 106.78(1), β = 99.11(1), γ = 112.34(1)^o. 2 crystallized in the monoclinic space group P2₁/c with a = 9.8109(8), b = 38.740(3), c = 11.6655(9) Å, β = 108.444(2)^o. 3 crystallized in the triclinic space group P-1with a = 11.4342(3), b = 13.4093(4), c = 16.1414(6) Å, α = 106.520(15), β = 98.760(18), γ = 112.390(16)^o. The crystal structures of the three inclusion compounds were elucidated and their thermal behaviour was analysed by thermal gravimetry, differential scanning calorimetry and hot stage microscopy. Thermal analysis of the inclusion compounds showed that the guest desorption occurred in two steps with the free guest released at the first step followed by that of hydrogen-bonded guest. The measure of stability of the inclusion compounds derived from thermal analysis revealed that 1 is more stable than 2. In 3, even though there are two different competitive guest molecules (PYR and MOR) present in the structure PYR is preferably encapsulated within the molecular cage, presumably because it is the preferred H-bond acceptor.

Graphical Abstract

The host compound 3,3′-bis (9-hydroxy-9-fluorenyl)-2,2′-binaphthyl formed inclusion compounds with pyridine and morpholine and their equimolar mixture. The crystal structures of the three inclusion compounds were elucidated and their thermal stabilities were analysed by thermal gravimetry, differential scanning calorimetry and hot stage microscopy.