Muoniated radical states in the organic semiconductor phthalocyanine

Phthalocyanine samples of ZnPc, H2Pc, and CuPc were investigated with the muon spin rotation technique. In ZnPc and H2Pc, three muoniated radical states of paramagnetic origin were identified, two of which have hyperfine interactions in the range 110-150 MHz and correspond to muonium addition at the outer benzene rings. The third state has a smaller hyperfine interaction (about 25 MHz) and is tentatively assigned to addition at bridging nitrogen atoms. CuPc has an unpaired electron from the Cu atom, which originates a diamagneticlike signal upon muonium addition. The signal has two components with very different relaxation rates, corresponding to two different spatial couplings of the Cu electron with the muonium's electron.