The preparation of crystalline pyrene, perylene, and azulene perchlorates is reported. Details of the novel method, growth on the anode in an electrolytic cell, are given. Crystalline samples of each compound give EPR resonances with very narrow linewidths, about 0.1 G. The resonances from the pyrene and perylene salts each consist of two components. One follows a Curie law and dominates at low temperature. It is attributed to “impurities,” probably lattice defects. The other component, dominating at high temperature, arises from thermally generated Wannier triplet excitons. The excitation energies are 0.18 and 0.27 eV for the pyrene and perylene salts, respectively. The azulene salt yielded only the “impurity” signal within the available temperature range.
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