2, 3, 7-Trihydroxy-9-phenyl-fluorone (hereafter H3Z) has been synthesised in its H4Z+, H3Z, H2Z− and Z3− protonation states. X-ray crystal structure determinations have been carried out for (H4Z)(HSO4), H3Z,[EtiPr2NH] H2Z, solvated (PPh4) H2Z and solvated K3Z. In each of these salts the 9-phenyl group adopts a different orientation so as to be involved in intermolecular aromatic interactions. The 3-and 6-phenolic carbon–oxygen bond lengths ...