Molecular doping is a powerful method to fine‐tune the thermoelectric properties of organic semiconductors, in particular to impart the requisite electrical conductivity. The incorporation of ...molecular dopants can, however, perturb the microstructure of semicrystalline organic semiconductors, which complicates the development of a detailed understanding of structure–property relationships. To better understand how the doping pathway and the resulting dopant counterion influence the thermoelectric performance and transport properties, a new dimer dopant, (N‐DMBI)2, is developed. Subsequently, FBDPPV is then n‐doped with dimer dopants (N‐DMBI)2, (RuCp*mes)2, and the hydride‐donor dopant N‐DMBI‐H. By comparing the UV–vis–NIR absorption spectra and morphological characteristics of the doped polymers, it is found that not only the doping mechanism, but also the shape of the counterion strongly influence the thermoelectric properties and transport characteristics. (N‐DMBI)2, which is a direct electron‐donating dopant with a comparatively small, relatively planar counterion, gives the best power factor among the three systems studied here. Additionally, temperature‐dependent conductivity and Seebeck coefficient measurements differ between the three dopants with (N‐DMBI)2 yielding the best thermoelectric properties. The results of this study of dopant effects on thermoelectric properties provide insight into guidelines for future organic thermoelectrics.
A novel dimeric n‐dopant (N‐DMBI)2, is designed and synthesized to understand the effects of molecular dopants on thermoelectric properties. This study shows how the counterion shape, and the doping mechanism affect the thermoelectric performance and the transport pathway of n‐type conducting polymers, and reveals what type of n‐dopant is preferable.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The molecule of the title compound, C
18
H
10
Br
2
S
4
, has a C-shape, with
C
s
molecular symmetry. The dihedral angle between the planes of the dithiol and phenyl rings is 8.35 (9)°. In the ...crystal, molecules form helical chains along 001, the shortest interactions being π...S contacts within the helices. The intermolecular interactions were investigated by Hirshfeld surface analysis. Density functional theory (DFT) was used to calculate HOMO–LUMO energy levels of the title compound and its
trans
isomer.
Structures of three cocrystals of nootropic racetams were studied. They included two cocrystals of phenylpiracetam (PPA) with 4-hydroxybenzoic acid (HBA) with different stoichiometries, PPA·HBA and ...PPA·2HBA, and cocrystal of 2-(4-phenyl-2-oxopyrrolidin-1-yl)-N’-isopropylideneacetohydrazide (PPAH) with 4-hydroxybenzamide (HBD), PPAH·HBD·(acetone solvate). X-ray study of the pure forms of PPA and PPAH was also carried out to identify variations of molecular synthons under the influence of conformers. The cocrystal structures revealed the diversity of supramolecular synthons namely, amide-amide, amide-acid, acid-acid, and hydroxyl-hydroxyl; however, very similar molecular chains were found in PPA and PPA·2HBA, and similar molecular dimers in PPAH and PPAH·HBD. In addition, conformational molecular diversity was observed as disorder in PPA·2HBA as it was observed earlier for rac-PPA that allows for the consideration that cocrystal as an example of partial solid solution. Quantum chemical calculations of PPA and PPAH conformers demonstrated that for most conformers, energy differences do not exceed 2 kcal/mol that suggests the influence of packing conditions (in this case R- and S-enantiomers intend to occupy the same molecular position in crystal) on molecular conformation.
A new polymorph of the title compound, C
10
H
13
NO, was obtained by recrystallization of the commercial product from a water/ethanol mixture (1:1
v
/
v
). Crystals of the previously reported racemic ...and homochiral forms of 2-phenylbutyramide were grown from water–acetonitrile solution in 1:1 volume ratio Khrustalev
et al.
(2014).
Cryst. Growth Des.
14
, 3360–3369. While the previously reported racemic and enantiopure forms of the title compound adopt very similar supramolecular structures (hydrogen-bonded ribbons), the new racemic polymorph is stabilized by a single N—H...O hydrogen bond that links molecules into chains along the
c
-axis direction with an antiparallel (centrosymmetric) packing in the crystal. Hirshfeld molecular surface analysis was employed to compare the intermolecular interactions in the polymorphs of the title compound.
The mol-ecule of the title compound, C
H
Br
S
, has a C-shape, with
mol-ecular symmetry. The dihedral angle between the planes of the di-thiol and phenyl rings is 8.35 (9)°. In the crystal, ...mol-ecules form helical chains along 001, the shortest inter-actions being π⋯S contacts within the helices. The inter-molecular inter-actions were investigated by Hirshfeld surface analysis. Density functional theory (DFT) was used to calculate HOMO-LUMO energy levels of the title compound and its
isomer.
•Six novel co-crystal structures of aromatic hydrocarbons and DDQ acceptor are being reported.•Robust π-π interactions mediate mixed stacks as the primary structural motif of all the ...co-crystals.•Auxiliary hydrogen bonds contribute to packing variations between samples.•Among all six co-crystals, co-crystals chrysene-DDQ and carbazole-DDQ have the highest crystal densities.
Co-crystals formed by polynuclear aromatic hydrocarbons (PAH) chrysene, benz(a)anthracene, triphenylene(9,10-benzophenanthrene), benzo(a)pyrene, dibenza,canthracene, and 9H-carbazole as π-electron-donor (D) molecules, with π-electron acceptor, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were synthesized, and their crystal structures were determined using single-crystal X-ray diffraction analysis. All co-crystals exhibit 1:1 donor / acceptor ratio and adopt mixed-stacking motifs. The donor(D)-acceptor (DDQ) π-π interactions in stacks are complemented by different sets of D…D, D…DDQ and DDQ…DDQ intermolecular interactions between stacks whose diversity originates from different degree of D/DDQ mismatch and manifests in dissimilar crystal packing motifs. The parallel face-to-face stacking was registered in chrysene-DDQ, while benz(a)anthracene-DDQ reveals brickwork crystal packing with significant parallel slippage. The rest four co-crystals show fairly different herringbone-type crystal packing with rearrangement of intermolecular interactions. The distribution of intermolecular contacts and impact of π-π interactions were evaluated through Hirshfeld surface analysis. Molecular orbital energies as well as bandgaps were calculated using DFT. Degree of charge-transfer was estimated based on bond length distribution in the acceptor molecule for each of the co-crystals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
RuCp*(1,3,5-R 3 C 6 H 3 ) 2 {Cp* = η 5 -pentamethylcyclopentadienyl, R = Me, Et} have previously been found to be moderately air stable, yet highly reducing, with estimated D + /0.5D 2 (where D 2 and ...D + represent the dimer and the corresponding monomeric cation, respectively) redox potentials of ca. −2.0 V vs. FeCp 2 +/0 . These properties have led to their use as n-dopants for organic semiconductors. Use of arenes substituted with π-electron donors is anticipated to lead to even more strongly reducing dimers. RuCp*(1-(Me 2 N)-3,5-Me 2 C 6 H 3 ) + PF 6 − and RuCp*(1,4-(Me 2 N) 2 C 6 H 4 ) + PF 6 − have been synthesized and electrochemically and crystallographically characterized; both exhibit D + /D potentials slightly more cathodic than RuCp*(1,3,5-R 3 C 6 H 3 ) + . Reduction of RuCp*(1,4-(Me 2 N) 2 C 6 H 4 ) + PF 6 − using silica-supported sodium–potassium alloy leads to a mixture of isomers of RuCp*(1,4-(Me 2 N) 2 C 6 H 4 ) 2 , two of which have been crystallographically characterized. One of these isomers has a similar molecular structure to RuCp*(1,3,5-Et 3 C 6 H 3 ) 2 ; the central C–C bond is exo , exo , i.e. , on the opposite face of both six-membered rings from the metals. A D + /0.5D 2 potential of −2.4 V is estimated for this exo , exo dimer, more reducing than that of RuCp*(1,3,5-R 3 C 6 H 3 ) 2 (−2.0 V). This isomer reacts much more rapidly with both air and electron acceptors than RuCp*(1,3,5-R 3 C 6 H 3 ) 2 due to a much more cathodic D 2 ˙ + /D 2 potential. The other isomer to be crystallographically characterized, along with a third isomer, are both dimerized in an exo , endo fashion, representing the first examples of such dimers. Density functional theory calculations and reactivity studies indicate that the central bonds of these two isomers are weaker than those of the exo , exo isomer, or of RuCp*(1,3,5-R 3 C 6 H 3 ) 2 , leading to estimated D + /0.5D 2 potentials of −2.5 and −2.6 V vs. FeCp 2 +/0 . At the same time the D 2 ˙ + /D 2 potentials for the exo , endo dimers are anodically shifted relative to those of RuCp*(1,3,5-R 3 C 6 H 3 ) 2 , resulting in much greater air stability than for the exo , exo isomer.
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