The hydrogen-bonding environments at the COOH moiety in eight polycrystalline polymorphs of palmitic acid are explored using solid-state NMR. Although most phases have no previously reported crystal structure, measured 13 C chemical shift tensors for COOH moieties, combined with DFT modeling establish that all phases crystallize with a cyclic dimer ( R 22(8)) hydrogen bonding arrangement. Phases A 2 , B m and E m have localized OH hydrogens while phase C has a dynamically disordered OH hydrogen. The phase designated A s is a mix of five forms, including 27.4% of B m and four novel phases not fully characterized here due to insufficient sample mass. For phases A 2 , B m , E m , and C the anisotropic uncertainties in the COOH hydrogen atom positions are established using a Monte Carlo sampling scheme. Sampled points are retained or rejected at the ±1 σ level based upon agreement of DFT computed 13 COOH tensors with experimental values. The collection of retained hydrogen positions bear a remarkable resemblance to the anisotropic displacement parameters ( i.e. thermal ellipsoids) from diffraction studies. We posit that this similarity is no mere coincidence and that the two are fundamentally related. The volumes of NMR-derived anisotropic displacement ellipsoids for phases with localized OH hydrogens are 4.1 times smaller than those derived from single crystal X-ray diffraction and 1.8 times smaller than the volume of benchmark single crystal neutron diffraction values.
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Functionalized anthrathienothiophenes: synthesis, properties, and integration into OFETs
For more than two decades, the silylethyne functionalization scheme has been used to induce strong π-stacking interactions in linear acenes and heteroacenes. As part of our efforts to better understand the crystal engineering aspects of silylethyne functionalization, along with an interest in studying the impact of ring topology on the electronic and optical properties of heteroacenes, we describe here the integration of thieno[3,2- b ]thiophene (a non-linear isomer of the well-known anthradithiophene) into our well established crystal engineering scheme. By utilizing the thienothiophene moiety coupled with an asymmetric solubilizing group (isopropenyldiisopropylsilylethyne), we were able to achieve charge carrier mobilities ( μ ) upwards of 0.22 cm 2 V −1 s −1 . Based on their increased stability and promising initial mobilities, the use of this thienothiophene moiety may offer a new approach to the formation of larger heteroacene analogues with more than 5 aromatic rings.
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- Award ID(s):
- 1849213
- NSF-PAR ID:
- 10410814
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 10
- Issue:
- 39
- ISSN:
- 2050-7526
- Page Range / eLocation ID:
- 14439 to 14443
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2TC02977D
