Search

The crystal structure of the title compound [systematic name: 2-(1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene)-6,6-bis(methoxyethoxymethoxymethyl)-1,3-dithiolo[4,5-b][1,4]dithiepine], C(21)H(30)O(6)S(8), a spiro-substituted BEDT-TTF analogue [BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene], has a strongly bent heterocyclic framework. The seven-membered ring adopts a pseudo-chair conformation with notably widened ring bond angles, especially at the methylene C atoms [119.49 (11) and 117.60 (11) degrees]. The axial side chain adopts an extended conformation, but the equatorial side chain curls back on itself and the O atom nearest the ring system is involved in three short contacts to H atoms (2.45-2.53 A). The molecules pack in centrosymmetrically related pairs, which are isolated from each other by columns of the polyether side chains. This study emphasizes the ease of distortion of the neutral bis(propylenedithio)tetrathiafulvalene ring structure, and how the need to accommodate side chains can easily override the tendency of these donor systems to form stacks in the crystalline state.

The title compounds, 2-(dimethylamino)biphenyl-2'-carboxaldehyde, C15H15NO, and 2-(dimethylamino)biphenyl-2',6'-dicarboxaldehyde, C16H15NO2, show similar 1,6-interactions [N...C=O 2.929 (3) to 3.029 (3) A] between the dimethylamino and aldehyde groups located in the ortho positions of the two rings, which lie at 58.1 (1)-62.4 (1) degrees to each other.