ODMR of the photoexcited triplet state of donor–acceptor complexes of naphthalene donor with pyromellitic dianhydride, 1,2,4,5-tetracyanobenzene, and 1,3,5-trinitrobenzene acceptors

Odmr measurements of photoexcited triplet state traps were carried out at 1.2 K on polycrystalline donor–acceptor complexes of naphthalene (N) with the acceptors pyromellitic dianhydride (PMDA), 1,2,4,5-tetracyanobenzene (TCNB), and 1,3,5-trinitrobenzene (TNB). The zero field splittings (zfs) are consistent with a locally excited N triplet state with considerable admixture of charge transfer character that increases in the order N/TNB<N/TCNB≈N/PMDA based on zfs. The complexes reveal sublevel-selective enhancements of decay rate constants that are similar for N/TCNB and N/PMDA, but the pattern differs in N/TNB, suggesting a different donor–acceptor interaction for the latter.