RESUMO
We present the synthesis of a new type of an expanded porphyrinoid macrocycle with a saddle-shaped morphology and its complexation of C60 guest molecules. The new macrocycle contains four carbazole and four triazole moieties and can be readily synthesized via a copper-catalyzed click reaction. It shows specific photo-physical properties including fluorescence with a high quantum yield of 60 %. The combination of the saddle-shaped geometry with the expanded π-system allows for host-guest interactions with C60 in a stacked polymer fashion. Evidence for the presence of a host-guest complex is provided both in solution by NMR spectroscopy and in the solid state by X-ray structure analysis.
RESUMO
We introduce a new carbazole-based zwitterionic ligand (DCzGPC) synthesized via Yamaguchi esterification which enhances the efficiency of lead halide perovskite (LHP) nanocrystals (NCs) in light-emitting diodes (LED). A facile ligand exchange of the native ligand shell, monitored by nuclear magnetic resonance (NMR), ultraviolet-visible (UV-vis), and photoluminescence (PL) spectroscopy, enables more stable and efficient LHP NCs. The improved stability is demonstrated in solution and solid-state LEDs, where the NCs exhibit prolonged luminescence lifetimes and improved luminance, respectively. These results represent a promising strategy to enhance the stability of LHP NCs and to tune their optoelectronic properties for further application in LEDs or solar cells.
RESUMO
Solvated tungsten iodide cluster compounds are presented with the homoleptic cluster cation [(W6I8)(CH3CN)6]4+ and the heteroleptic [(W6I8)I(CH3CN)5]3+, synthesized from W6I22 in acetonitrile. Crystal structures were solved and refined on deep red single-crystals of [(W6I8)(CH3CN)6](I3)(BF4)3·H2O, [(W6I8)I(CH3CN)5](I3)2(BF4), and on a yellow single-crystal of [W6I8(CH3CN)6](BF4)4·2(CH3CN) on the basis of X-ray diffraction data. The structure of the homoleptic [(W6I8)(CH3CN)6]4+ cluster is based on the octahedral [W6I8]4+ tungsten iodide cluster core, coordinated by six apical acetonitrile ligands. The electron localisation function of [(W6I8)(CH3CN)6]4+ is calculated and solid-state photoluminescence and its temperature depedence are reported. Additionally, photoluminescence and transient absorption measurements in acetonitrile are shown. Results of the obtained data are compared to compounds containing [(M6I8)I6]2- and [(M6I8)L6]2- (M = Mo or W; L = ligand) clusters.
RESUMO
The assembly of colloidal semiconductive nanocrystals into highly ordered superlattices predicts novel structure-related properties by design. However, those structure-property relationships, such as charge transport depending on the structure or even directions of the superlattice, have remained unrevealed so far. Here, electric transport measurements and X-ray nanodiffraction are performed on self-assembled lead sulfide nanocrystal superlattices to investigate direction-dependent charge carrier transport in microscopic domains of these materials. By angular X-ray cross-correlation analysis, the structure and orientation of individual superlattices is determined, which are directly correlated with the electronic properties of the same microdomains. By that, strong evidence for the effect of superlattice crystallinity on the electric conductivity is found. Further, anisotropic charge transport in highly ordered monocrystalline domains is revealed, which is attributed to the dominant effect of shortest interparticle distance. This implies that transport anisotropy should be a general feature of weakly coupled nanocrystal superlattices.
