Thermally Activated n-Doping of Organic Semiconductors Achieved by N-Heterocyclic Carbene Based Dopant.

Molecular doping plays an important role in the modification of carrier density of organic semiconductors thus enhancing their optoelectronic performance. However, efficient n-doping remains challenging, especially owing to the lack of strongly reducing and air-stable n-dopants. Herein, an N-heterocyclic carbene (NHC) precursor, DMImC, is developed as a thermally activated n-dopant with the excellent stability in air. Its thermolysis in situ regenerates free NHC and subsequently dopes typical organic semiconductors. In sequentially doped FBDPPV films, DMImC does not disturb the π-π packing of the polymer and achieves good miscibility with the polymer. As a result, a high electrical conductivity of up to 8.4 S cm-1 is obtained. Additionally, the thermally activated doping and the excellent air stability permit DMImC to be noninteractively co-processed with polymers in air. Our results reveal that DMImC can be served as an efficient n-dopant suitable for various organic semiconductors.

Synthesis, crystal structure determination, and spectroscopic analyses of 1-chloro-2-(2,6-diisopropylphenyl)-4,4-dimethyl-2-azaspiro[5.5]undecane-3,5-dione: an unyielding precursor to a cyclic (alkyl)(amido)carbene.

The synthesis, single-crystal X-ray structure, and 1H and 13C NMR spectrocopic analyses of an unyielding precursor molecule to a cyclic (alkyl)(amido)carbene, 1-chloro-2-(2,6-diisopropylphenyl)-4,4-dimethyl-2-azaspiro[5.5]undecane-3,5-dione, C24H34ClNO2 (1), is reported. Despite the use of several bases, 1 could not be deprotonated to afford the corresponding carbene. The crystal structure of 1 was compared to the crystal structures of two structurally similar HCl adducts of stable carbenes (compounds 4 and 5), which revealed no significant differences in the geometries about the `carbene' C atoms. To better understand the reactivity differences observed for 1 when compared to 4 and 5, modified percent buried volume (%Vbur) calculations were performed. These calculations revealed that the H atom bound to the carbene C atom is the most sterically hindered in compound 1 when compared to 4 and 5 (%Vbur = 84.9, 81.3, and 79.3% for 1, 4, and 5, respectively). Finally, close inspection of the quadrant-specific %Vbur values indicated that the approach of a deprotonating base to the H atom bound to the carbene C atom is significantly blocked in 1 (69.9%) when compared to 4 and 5 (50.4 and 56.5%, respectively).

Crystal structure of zwitterionic 3,3'-[1,1'-(butane-1,4-di-yl)bis-(1H-imidazol-3-ium-3,1-di-yl)]bis-(propane-1-sulfonate) dihydrate.

The crystal structure of the title compound, C16H26N4O6S2·2H2O, a water-soluble di-N-heterocyclic carbene ligand precursor was determined using a single crystal grown by the slow cooling of a hot N,N-di-methyl-formamide solution of the compound. The dihydrate crystallizes in the monoclinic space group P21/c, with half of the zwitterionic mol-ecule and one water mol-ecule of crystallization in the asymmetric unit. The remaining part of the mol-ecule is completed by inversion symmetry. In the mol-ecule, the imidazole ring planes are parallel with a plane-to-plane distance of 2.741 (2) Å. The supra-molecular network is consolidated by hydrogen bonds of medium strength between the zwitterionic mol-ecules and the water mol-ecules of crystallization, as well as by π-π stacking inter-actions between the imidazole rings of neighbouring mol-ecules and C-H⋯O hydrogen-bonding inter-actions.