Abstract
Copper perchlorophthalocyanine (CuPcCl16, CuC32N8Cl16, Pigment Green 7) is one of the commercially most important green pigments. The compound is a nanocrystalline fully insoluble powder. Its crystal structure was first addressed by electron diffraction in 1972 [Uyeda et al. (1972). J. Appl. Phys. 43, 5181–5189]. Despite the commercial importance of the compound, the crystal structure remained undetermined until now. Using a special vacuum sublimation technique, micron-sized crystals could be obtained. Three-dimensional electron diffraction (3D ED) data were collected in two ways: (i) in static geometry using a combined stage-tilt/beam-tilt collection scheme and (ii) in continuous rotation mode. Both types of data allowed the crystal structure to be solved by direct methods. The structure was refined kinematically with anisotropic displacement parameters for all atoms. Due to the pronounced crystal mosaicity, a dynamic refinement was not feasible. The unit-cell parameters were verified by Rietveld refinement from powder X-ray diffraction data. The crystal structure was validated by many-body dispersion density functional theory (DFT) calculations. CuPcCl16 crystallizes in the space group C2/m (Z = 2), with the molecules arranged in layers. The structure agrees with that proposed in 1972.
Highlights
Copper phthalocyanine (CuPc, Scheme 1) is the most important blue pigment used today (Hunger & Schmidt, 2018).Chlorination of CuPc shifts the colour towards green shades
The structure was solved by direct methods as implemented in SIR (Burla et al, 2012)
The structure analysis from 3D electron diffraction (ED) data was performed on crystals prepared by vacuum deposition [Fig. 4(b)]
Summary
Copper phthalocyanine (CuPc, Scheme 1) is the most important blue pigment used today (Hunger & Schmidt, 2018).Chlorination of CuPc shifts the colour towards green shades. CuPc and CuPcCl16 are registered in the Colour Index as Pigment Blue 15 and Pigment Green 7, respectively (Abel, 1998). The pigments exhibit an excellent photostability and, a very high fastness to light and weathering Their heat stability is outstanding, to more than 500 C, so that they can even be used for the mass colouration of low-melting glass (Schmidt & Kliemt, 2013). Their industrial synthesis is quite easy (see Fig. 1). Their price is quite low, only 5–10 Euro per kilogram
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