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.

An organic electroluminescent device includes a first electrode, a hole transport region provided on the first electrode, an emission layer provided on the hole transport region, an electron transport region provided on the emission layer, and a second electrode provided on the electron transport region, wherein the emission layer includes an organometallic compound represented by Formula 1. ##STR00001##

A compound comprising a first ligand L.sub.A of Formula I, ##STR00001##
is disclosed. In the structure of Formula I, ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring; Z.sup.1-Z.sup.4 are each independently C or N; at least two consecutive Z.sup.1-Z.sup.4 are C, and are fused to a structure of ##STR00002##
or ##STR00003##
Y.sup.1 and Y.sup.2 are each independently O, S, Se, CRR′, SiRR′, or GeRR′; each R.sup.A, R.sup.B, R.sup.C, R, and R′ is a hydrogen or a substituent; and any two substituents may be joined or fused together to form a ring. In the compound, L.sub.A is complexed to a metal M by the dashed lines in Formula I to form a five-membered chelate ring, and M has an atomic weight greater than 40. Organic light emitting devices and consumer products containing the compounds are also disclosed.

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.

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.

An organic light-emitting device includes: a first electrode; a second electrode; an organic layer between the first electrode and the second electrode and including an emission layer; and at least one organometallic compound represented by Formula 1. The organic light-emitting device including the organometallic compound may have a low driving voltage, a high luminance, a high efficiency, and a long lifespan:

##STR00001##

An organometallic compound represented by Formula 1:

##STR00001## wherein, in Formula 1, M, X.sub.11, X.sub.12, X.sub.13, X.sub.14, A.sub.11, R.sub.11, R.sub.14, b11, n, L.sub.11, and m are described in the specification.

The present disclosure relates to an electron transfer mediator comprising the osmium complex or a salt thereof, a reagent composition for an electrochemical biosensor, and an electrochemical biosensor, where the osmium compound or its salt maintains a stable oxidation-reduction form for an extended time period, a capacity to react with oxidoreductase being capable of performing the redox reaction of the target analytes, and no effect of oxygen partial pressure.

Provided are organometallic compounds. Also provided are formulations comprising these organometallic compounds. Further provided are OLEDs and related consumer products that utilize these organometallic compounds.