Structural and conformational analysis of six-, seven-, and eight-membered cycloalkanes in tris(5-acetyl-3-thienyl)methane inclusion compounds

Abstract

Tris(5-acetyl-3-thienyl)methane (TATM) forms inclusion compounds with cyclohexane, -heptane, and -octane in a host/guest ratio of 2:1. The clathrate compounds have been studied by X-ray crystallography. The inclusion compound with cyclohexane crystallizes in two distinct triclinic unit cells of space group [Formula: see text] in the A form, the unit cell dimensions are a = 8.622(2), b = 10.194(2),c = 12.795(2) Å, α = 79.09(1)°, β = 72.74(1)°,γ = 84.89(1)°, V = 1053.9(4) Å3(220 K); for the B form, a = 11.668(4), b = 13.729(3), c = 14.227(4) Å, α = 89.40(3)°, β = 77.20(4)°, γ = 76.24(4)°, V = 2157(1) Å (room temperature). In the A form the cavity is of the channel type but the guest molecule is located on a centre of inversion while in the B form the cavity is also of the channel type but the guest molecule is in a general position. The inclusion compounds of cycloheptane and cyclooctane crystallize only in the B form. The guest molecules in the B form are disordered. Conformational analyses of the guest molecules have also been performed by a combination of molecular dynamics and energy minimization.