Influencing the solid-solid phase transition in phenanthrene by suitable doping

The order-disorder phase transition in solid phenanthrene was studied with differential scanning calorimetry and X-ray powder diffraction. This fully reversible transformation can be influenced by doping phenanthrene with str ucturally similar polycyclic aromatic hydrocarbons or heterocyclic aromatic s. So far, four dopants have been used: benzo[c]cinnoline, phenanthridine, anthracene and carbazole. It was found that the transformation is not influ enced by dopants that form eutectic phase diagrams with phenanthrene (benzo [c]cinnoline, phenanthridine). However, if the dopant is incorporated into the phenanthrene lattice to form a mixed crystal, the transition is inhibit ed above 3.7 mol% anthracene and 6.1 mol% carbazole, respectively. By X-ray diffraction, it is shown that these dopants induce the formation of the hi gh-temperature phase already at room temperature.