ABSTRACT
The gelation properties and mode of self-assembly of six asymmetrical hexaether triphenylene derivatives mono-functionalized with carboxylic and primary amine groups were investigated. The presence of a carboxylic and amine group attached to the triphenylene core generated stable, thermo- and pH-sensitive supramolecular π-organogels with a reversible response to both stimuli. In order to understand the gelation process, we studied the effect of the spacer length and found a different gelation scope for the acid and basic derivatives that accounts for a different supramolecular self-assembly. The presence of the basic group on the amino derivatives was used to guide and catalyze the templated in situ sol-gel polymerization of TEOS and allowed us, under controlled hydrolytic conditions, to prepare an entangled fibrillar network of silica nanotubes.
ABSTRACT
Crystal structures are presented for two members of the homologous series of 1,2-dibromo-4,5-dialkoxybenzenes, viz. those with decyloxy and hexadecyloxy substituents, namely 1,2-dibromo-4,5-bis(decyloxy)benzene, C(26)H(44)Br(2)O(2), (II), and 1,2-dibromo-4,5-bis(hexadecyloxy)benzene, C(38)H(68)Br(2)O(2), (III). The relative influences which halogen bonding, π-π stacking and van der Waals interactions have on these structures are analysed and the results compared with those already found for the lightest homologue, 1,2-dibromo-4,5-dimethoxybenzene, (I) [Cukiernik, Zelcer, Garland & Baggio (2008). Acta Cryst. C64, o604-o608]. The results confirm that the prevalent interactions stabilizing the structures of (II) and (III) are van der Waals contacts between the aliphatic chains. In the case of (II), weak halogen C-Br···(Br-C)' interactions are also present and contribute to the stability of the structure. In the case of (III), van der Waals interactions between the aliphatic chains are almost exclusive, weaker C-Br···π interactions being the only additional interactions detected. The results are in line with commonly accepted models concerning trends in crystal stability along a homologous series (as measured by their melting points), but the earlier report for n = 1, and the present report for n = 10 and 16, are among the few providing single-crystal information validating the hypothesis.
ABSTRACT
The title compound, C(12)H(16)BrO(2), is an interesting case of a simple organic molecule making use of five different types of intra- and intermolecular interactions (viz. conventional and nonconventional hydrogen bonds, and pi-pi, Br...Br and Br...O contacts), all of them relevant in the molecular and crystal structure geometry. The molecules are strictly planar, with an intramolecular O-H...O hydrogen bond, and associate into two-dimensional structures parallel to (201) through two different types of halogen bonding. The planar structures, in turn, stack parallel to each other interlinked by C-H...pi and pi-pi contacts. Also discussed are the relevant structural features leading to the rather low melting point of the compound.