On quinacridones and their supramolecular mesomerism within the crystal lattice

After making a comparison between inorganic pigments and quinacridone, several experimental results ensuing from 30 years of research are presented. Following this, the bridging hydrogen bond and crystal engineering are treated with some definitions, the pigment finishing is touched upon and the pi...sigma correlation is introduced. This is regarded as mesomerism between two non-covalent bond types, namely charge transfer and H bonds. It is compared with the lattice of the carbon blacks and thus used to explain the excellent stability of the quinacridones. In conclusion, Desiraju's supramolecular synthons serve in the interpretation of the somewhat abstract pi...sigma correlation. Quinacridone crystals are made up solely of pi...pi charge transfer bonds and bridging hydrogen bonds i.e. they contain both of these non-covalent bonding types in compact form. This means that each and every quinacridone molecule is in itself a source of supramolecular mesomerism which encompasses the entire crystal lattice. (C) 2002 Elsevier Science Ltd. All rights reserved.