Organic pigments such as indigos, quinacridones, and phthalocyanines are widely produced industrially as colorants for everyday products as various as cosmetics and printing inks. Herein we introduce a general procedure to transform commercially available insoluble microcrystalline pigment powders into colloidal solutions of variously sized and shaped semiconductor micro- and nanocrystals. The synthesis is based on the transformation of the pigments into soluble dyes by introducing transient protecting groups on the secondary amine moieties, followed by controlled deprotection in solution. Three deprotection methods are demonstrated: thermal cleavage, acid-catalyzed deprotection, and amine-induced deprotection. During these processes, ligands are introduced to afford colloidal stability and to provide dedicated surface functionality and for size and shape control. The resulting micro- and nanocrystals exhibit a wide range of optical absorption and photoluminescence over spectral regions from the visible to the near-infrared. Due to excellent colloidal solubility offered by the ligands, the achieved organic nanocrystals are suitable for solution processing of (opto)electronic devices. As examples, phthalocyanine nanowire transistors as well as quinacridone nanocrystal photodetectors, with photoresponsivity values by far outperforming those of vacuum deposited reference samples, are demonstrated. The high responsivity is enabled by photoinduced charge transfer between the nanocrystals and the directly attached electron-accepting vitamin B2 ligands. The semiconducting nanocrystals described here offer a cheap, nontoxic, and environmentally friendly alternative to inorganic nanocrystals as well as a new paradigm for obtaining organic semiconductor materials from commercial colorants.

The catalytic activity of several metal complexes in ionic liquids towards Michael addition of acetylacetone to methyl vinyl ketone is found to be strongly dependent on the presence of halogenide impurities of the solvent. The tested metal complexes are Ni(acac)₂·2H₂O, FeCl₃·6H₂O, Yb(TfO)₃ (TfO = triflate) and Co(acac)₂, and the ionic liquids used as solvents are [bmim]BF₄ and [bmim]PF₆ (bmim = 1-n-butyl-3-methylimidazolium). The rationalisation of the halogenide effect in terms of ligand exchange from the starting complex with the excess chloride of impure ionic liquids is demonstrated in the case of the cobalt based system where the formation of the poorly active CoCl₄ ²⁻ species is detected by UV-Vis analysis.