Microporous Triptycene‐Based Affinity Materials on Quartz Crystal Microbalances for Tracing of Illicit Compounds

Abstract

Triptycene‐based organic molecules of intrinsic microporosity (OMIMs) with extended functionalized π‐surfaces are excellent materials for gas sorption and separation. In this study, the affinities of triptycene‐based OMIM affinity materials on 195 MHz high‐fundamental‐frequency quartz crystal microbalances (HFF‐QCMs) for hazardous and illicit compounds such as piperonal and (–)‐norephedrine were determined. Both new and existing porous triptycene‐based affinity materials were investigated, resulting in very high sensitivities and selectivities that could be applied for sensing purposes. Remarkable results were found for safrole – a starting material for illicit compounds such as ecstasy. A systematic approach highlights the effects of different size of π‐surfaces of these affinity materials, allowing a classification of the properties that might be optimal for the design of future OMIM‐based affinity materials.

Triptycene End-Capped Quinoxalinophenanthrophenazines with Aromatic Substituents – Synthesis, Characterization, and Single-Crystal Structure Analysis

“…In all four crystal structures the prominent formation of cofacial π-π dimers was found, in accordance to those previously described. [22][23][24] However, in none of the structures the QPPs formed a continuous π-stacked pattern. Nevertheless, to compare the dimer formation by π stacking, the degree of overlap of the π-surfaces can best be described by the offset in x-and y-direction, where x is defined as the long axis of the πsystem and y as the short axis (for details see Fig.…”

“…13,14 As mentioned already, π-stacking is unfortunately less directional than other supramolecular motifs and therefore ideal arrangements are more difficult to achieve. [9][10][11] During our initial work on organic molecules with intrinsic microporosities, [15][16][17][18][19][20][21][22] we observed a hexagonal packing of D 3h -symmetric triptycene-based large quinoxalinophenanthrophenazines (QPPs) via an unusual strong π-π interaction of the QPP blades with those of adjacent QPP molecules. 23 This packing motif could only be broken by triptycene-end-capping.…”

“…23 To our delight, we found the same dimer formation also for D 3hsymmetric QPP with a central triptycene core bearing three πplanes that contain triisopropylsilylethynyl groups at the peripheral phenylene rings. 22 This encouraged us to further systematically study the influence of smaller substituents such as bromide, methoxy, or cyano at the peripheral rings on the packing motif. Again, the dimer formation was observed for all derivatives under specific crystallization conditions (e.g.…”

Triptycene End‐Capped Quinoxalinophenanthrophenazines (QPPs): Influence of Substituents and Conditions on Aggregation in the Solid State

“…As an example, sublimated thin films of pentacene typicallyc onsist of two different crystallographic phases. [28] During our work on triptycene-based organic molecules of intrinsicm icroporosity (OMIMs), [29][30][31][32][33] we observed the formation of hexagonal arrangements of these molecules by ar elatively tight p stacking of the large aromatic quinoxalinophenanthrophenazine (QPP) planes, despite the existing tert-butyl groups at the pyrene units. [26,27] Very recently,o ne-dimensionalm ixed stacks of acene and azaacene derivatives with a high structuralo verlap of the p planes through an hydrogenbonding-assisted encapsulatingapproach, which shouldbeoptimal for charge transport,have been reported.…”

“…[26,27] Very recently,o ne-dimensionalm ixed stacks of acene and azaacene derivatives with a high structuralo verlap of the p planes through an hydrogenbonding-assisted encapsulatingapproach, which shouldbeoptimal for charge transport,have been reported. [28] During our work on triptycene-based organic molecules of intrinsicm icroporosity (OMIMs), [29][30][31][32][33] we observed the formation of hexagonal arrangements of these molecules by ar elatively tight p stacking of the large aromatic quinoxalinophenanthrophenazine (QPP) planes, despite the existing tert-butyl groups at the pyrene units. [34] Fascinated by this structural motif, four structurally related QPP model compounds were synthesized, and the influence of tert-butyl groups and the triptycene endcaps weres tudied experimentally and theoretically (Figure1).…”