Provided are an organometallic compound, an organic light-emitting device including the same, and a diagnostic composition including the same. The organometallic compound is represented by Formula 1

M(L.sub.A).sub.n1(L.sub.B).sub.n2 wherein, in Formula 1, M is a transition metal, L.sub.A is a ligand represented by Formula 2A, L.sub.B is a ligand represented by Formula 2B,

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An organic light-emitting device including a first electrode, a second electrode, and an organic layer between the first and the second electrode, wherein the organic layer includes an emission layer, and the emission layer includes a first compound as a hole transport compound, a second compound as an electron transport compound, and a third compound represented by Formula 1:

##STR00001##

wherein in Formula 1, M is a transition metal, and at least one selected from A.sub.1 and A.sub.2 includes at least one deuterium.

A light-emitting element having low driving voltage and high emission efficiency is provided. In the light-emitting element, a combination of a guest material and a host material forms an exciplex. The guest material is capable of converting triplet excitation energy into light emission. Light emission from the light-emitting layer includes light emission from the guest material and light emission from the exciplex. The percentage of the light emission from the exciplex to the light emission from the light-emitting layer is greater than 0 percent and less than or equal to 60 percent. The energy after subtracting the energy of light emission from the exciplex from the energy of light emission from the guest material is greater than 0 eV and less than or equal to 0.23 eV.

Provided are compounds that include a ligand L.sub.A of Formula I

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An organic electroluminescence device according to an embodiment of the present disclosure includes a first electrode, a second electrode, and an emission layer. The emission layer includes host compounds and dopant compounds. The hot compounds include a first host compound represented by Formula 1, and a second host compound represented by Formula 2, and the dopant compounds include an assistant dopant compound represented by Formula 3, and a light-emitting dopant compound represented by Formula 4:

##STR00001##

Accordingly, the organic electroluminescence device according to an embodiment may achieve high efficiency and long life.

A novel compound having the formula Os(L).sub.n is disclosed, wherein Os is osmium(IV) metal, L is a ligand coordinating to the Os atom, and n is an integer from 1 to 6, wherein each L can be same or different, wherein at least one L is a multidentate ligand, and wherein the compound is neutral.

A method of making an osmium(II) complex having Formula I, L.sup.1-Os-L.sup.2, wherein L.sup.1 and L.sup.2 are independently a biscarbene tridentate ligand, wherein L.sup.1 and L.sup.2 can be same or different is disclosed. The method includes (a) reacting a precursor of ligand L.sup.1 with an osmium precursor to form an intermediate product, wherein the osmium precursor having the formula OsH.sub.x(PR.sub.3).sub.y, wherein x is an integer from 2 to 6 and y is an integer from 2 to 5, and R is selected from the group consisting of aryl, alkyl and cycloalkyl; and (b) reacting a precursor of ligand L.sup.2 with said intermediate product.

A compound comprising a first ligand L.sub.A having the formula

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Formula I, is disclosed. In Formula I, ring A is a five- or six-membered carbocyclic or heterocyclic ring; Y.sup.1 is selected from carbon and nitrogen; each of X.sup.1 to X.sup.4 is C or N; at least two adjacent R.sup.2s of ring B form a fused structure having the following formula:

##STR00002##

ring C is fused to ring B and the wavy lines are bonds attached to ring B; ring D and ring E are either a 5-membered aromatic ring or a 6-membered aromatic ring; each R.sup.1, R.sup.2, R.sup.3, R.sup.A, R.sup.B, R.sup.C, and R.sup.D is independently selected from a variety of substituents; ligand L.sub.A is coordinated to a metal M and, optionally, linked with other ligands; and M is optionally coordinated to other ligands. Organic light emitting devices and consumer products containing the compounds are also disclosed.

The present invention includes novel hexadentate metal complexes. The complexes hexadentate ligands of the present invention may be useful as improved emitters in an OLED device.

The present invention includes novel metal complexes of 5H-benzimidazo[1,2-a]benzimidazole (BimBim) and related ligands. The novel ligands may coordinate to one or two metal centers. The metal complexes of the present invention comprising these ligands may be useful as emissive materials and n-dopants in OLED devices.