An organometallic compound represented by Formula 1, an organic light-emitting device including the organometallic compound, and a diagnostic composition including the organometallic compound:

M11(L11)n11(L12)n12  Formula 1



wherein, in Formula 1,
M11 is a first-row transition metal, a second-row transition metal, or a third-row transition metal,
L11 is a ligand represented by Formula 1-1,
L12 is a monodentate ligand or a bidentate ligand,
n11 is 1, and
n12 is 0, 1, or 2:










wherein, in Formula 1-1,
Y11, A11, T11 k11, k12, k13, b11, E11 to E13 and R11 to R17 are described in the specification, and *1 to *4 each independently indicate a binding site to M11.