Described herein are compounds containing palladium(II), as the central metal atom, and tetradentate [N{circumflex over ( )}C{circumflex over ( )}C{circumflex over ( )}N] ligands. The compounds are charge neutral, and feature a donor-acceptor structure where a pendant substituted amino group (such as unsubstituted diphenylamine or substituted diphenylamine) and a heteroaryl group (such as pyridine group) serve as donor and acceptor, respectively. This donor-acceptor structure introduces a set of low-energy singlet and triplet charge-transfer excited states with small energy separation allowing for efficient thermally activated delayed fluorescence to take place.