Controlled Orientation of Polyconjugated Guest Molecules in Tunable Host Cavities

Abstract

Linear conjugated guest molecules with high aspect ratios form inclusion compounds with guanidinium organodisulfonate (GDS) host frameworks in which organodisulfonate "pillars" connect opposing GS sheets to generate lamellar architectures that reflect templating by the guest. Through judicious selection of pillars having adjustable lengths (l(S-S), as measured by the separation between distal sulfur atoms) and guests of various lengths (l(g)), the framework architecture can be controlled systematically in a manner that enables regulation of the guest orientation and aggregation in the host framework. Inclusion compounds for which l(g)/l(S-S) ≤ 0.9 exhibit a bilayer architecture with 1-D channels containing guests oriented parallel to the long axis of the pillar. Guests with values of l(g) comparable to l(S-S), however, promote the formation of a brick architecture in which the guests and the pillar are arranged in a herringbone motif. Surprisingly, longer guests (l(g) = 1.25l(S-S)) favor the formation of the bilayer architecture despite their larger volume because the guests are forced to align end-to-end as single-file arrays due to the vertical constraints of the 1-D channels. Bithiophene and biphenyl guests (l(g) < l(S-S)) are exceptional, promoting bilayer structures in which turnstile rotations of the pillars afford an unusual motif in which the guests are isolated from one another. The ability to synthesize a large family of compounds based on a common supramolecular building block (the GS sheet) permits construction of a structural "phase diagram" based on two simple molecular parameters, l(g) and l(S-S), that can be used to sort the inclusion compounds according to their framework architectures and enable prediction of crystal structures for new host-guest combinations. The effects of these different framework architectures and packing motifs is manifested as bathochromic shifts in the absorption and emission spectra of the guests compared with their spectra in methanol solutions. This behavior is supported by ab initio TDDFT calculations that reproduce the bathochromic shifts associated with the effects of guest-guest and guest-host interactions, combined with conformational constraints imposed on the guest molecules by the rigid host framework.

3D polyaniline nanoflowers self-assembled from single crystal nanoplates

“…Three dimensional (3D) crystals of organic/polymer semiconductors are expected to form high-quality 3D electronic devices [1][2][3][4][5]. Polyaniline is expected to play an important role in practical applications due to their light weight, conductivity and chemical properties [1,2,[6][7][8][9][10][11][12].…”

Dinitroxide biradical crystals with polar order

“…Expansion to the unit cell afforded the value of 14.96 D (number of molecules per unit cell = 4), thus confirming that the global dipolar moment of the assembly is approximately the sum of each individual small dipole. For the DCM solvate, the dipolar moment of dCdO in this crystalline state (in this conformation) is 3.20 D. That of the unit cell reached 21.50 D due to the number of molecules per unit cell (5) and the presence of the solvent molecules (DCM), which are also oriented in a manner that does not cancel their dipolar moments. Thus, even though this polar arrangement of dinitroxides in the crystalline state is not particularly surprising with respect to other crystalline forms for example of diamagnetic molecules, the fact that such polar assemblies were not observed for the various crystalline forms of the analogous tri-spiro dinitroxide bTbk, or for the sulphur derivative of bTbk (4 S atoms instead of the 4 oxygen ketal atoms), make the present results unexpected and open interesting perspectives for the measurements of magnetic properties.…”

“…[1][2][3][4] For example, the possibility of engineering crystals in which guests are located in precise non-centrosymmetric positions [5][6][7][8][9] holds great promise for second-harmonic generation (SHG) in nonlinear optics. [10][11][12] Yet in the majority of cases, the molecules pack in the crystal to cancel their dipolar moment, often at the origin of crystallization in centrosymmetric space groups.…”

Hydrogen Bonding in Supramolecular Crystal Engineering

“…It has been a widely used building block to construct a variety of interesting rosette supramolecular structures with organic sulfonate or carbonate by strong charge-assisted + N-H···O − hydrogen bonds [87][88][89][90]. The resulting porous frameworks provide opportunities for study of solid-state hostguest behaviors, which is an important aspect of crystal engineering.…”

“…Hickey and coworkers [129] prepared a cocrystal with saccharin (88) employing the peripheral hydrogen bonding capabilities of CBZ dimer. The cocrystal was found to possess favorable dissolution properties, suspension stability and pharmacokinetics using dog models.…”