The invention relates to small, conjugatable, orthogonal and tunable fluorophores for imaging of small bioactive molecules. The invention further relates to processes for the preparation of the compounds, and uses of the compounds in therapeutic, diagnostic, surgery and analytical applications. The invention provides a compound of formula (I), a derivative or a salt thereof. Wherein X is selected from the group consisting of NH, O, S, SeR5R6, CR7R8; R1 is selected from the group consisting of amines, alcohols, thiols, thiophenols, selenols, selenophenols and aryl groups; R2 and R3 are independently H or a halogen; R4 tis either H, nitro or cyano; R5 is either absent or methyl or oxygen; R6 is either absent or methyl or oxygen; and R7 and R8 are independently selected from the group consisting of linear or cyclic alkyl groups containing halogen, amino, cyano or carboxylic ester substituents, and alkyl aryl groups.

##STR00001##

To provide a light-emitting element with high emission efficiency and low driving voltage. The light-emitting element includes a guest material and a host material. A HOMO level of the guest material is higher than a HOMO level of the host material. An energy difference between the LUMO level and a HOMO level of the guest material is larger than an energy difference between the LUMO level and a HOMO level of the host material. The guest material has a function of converting triplet excitation energy into light emission. An energy difference between the LUMO level of the host material and the HOMO level of the guest material is larger than or equal to energy of light emission of the guest material.

A light emitting element that includes a first electrode, a second electrode on the first electrode, and an emission layer between the first electrode and the second electrode is provided. The emission layer includes an organometallic compound represented by Formula 1. The light emitting element has a reduced driving voltage, emits light having an increased color purity, and exhibits a high efficiency and a long lifespan.

##STR00001##

The present invention relates to organic light-emitting devices comprising (a) an anode, (i) a cathode, and (e) an emitting layer between the anode and cathode, comprising 2 to 40% by weight of a triplet emitter X having a difference of the singlet energy (E.sub.S1(X)) and the triplet energy (E.sub.T1(X)) of less than or equal to 0.4 eV [Δ(E.sub.S1(X))−(E.sub.T1(X))≤0.4 eV], 0.05 to 5.0% by weight of a fluorescent emitter Y and 55 to 97.95% by weight of a host compound(s), wherein the amount of the triplet emitter X, the fluorescent emitter Y and the host compound(s) adds up to a total of 100% by weight and the singlet energy of the triplet emitter X (E.sub.S1(X)) is greater than the singlet energy of the fluorescent emitter Y (E.sub.S1(Y)) [(E.sub.S1(X))>E.sub.S1(Y)]. By doping, for example, an emitting layer containing a luminescent organometallic complex having a small S.sub.1-T.sub.1 splitting, with a fluorescent emitter the emission decay time can significantly be shortened without sacrificing external quantum efficiency (EQE) because of very efficient energy transfer.

The present invention relates to phosphorous host materials and an organic electroluminescent device comprising the same. By using the phosphorous host material of the present invention, an organic electroluminescent device having significantly improved operational lifespan can be produced.

An iridium complex has the structure:

##STR00001##

wherein X′ and X″ independently represent carbon or nitrogen; X.sup.1, X.sup.2, X.sup.3, and X.sup.4 independently represent carbon or nitrogen; R.sup.1 and R.sup.5 independently represent substituted or unsubstituted C.sub.1-C.sub.12 alkyl; R.sup.2, R.sup.3, and R.sup.4 independently represent hydrogen, C.sub.1-C.sub.12 alkyl, substituted or unsubstituted C.sub.6-C.sub.12 aryl, or —C.sub.mF.sub.2m+1, m is from 1 to 3; each of m and n is from 1 to 3; A.sup.1 and A.sup.2 independently represent an unsaturated 5-membered or 6-membered ring; B is —O—, —NR— or —CR.sub.2—, A.sup.2 may join with —NR— or —CR.sub.2— to form a C.sub.9-C.sub.14 N-heteroaromatic or aromatic ring; b is 0 or 1; R.sup.6 is hydrogen, fluorine, substituted or unsubstituted C.sub.1-C.sub.12 alkyl, substituted or unsubstituted C.sub.1-C.sub.6 alkoxyl, substituted or unsubstituted C.sub.6-C.sub.12 aryl, substituted or unsubstituted C.sub.1-C.sub.6 amino, or —C.sub.xF.sub.2x+1, x is from 1 to 3; and p is from 1 to 3.

Platinum, palladium, and gold complexes suitable for use as phosphorescent emitters or as delayed fluorescent and phosphorescent emitters having one of the following structures:

##STR00001## ##STR00002##

The present disclosure relates to an organic electroluminescent compound and an organic electroluminescent device comprising the same. By comprising the organic electroluminescent compound of the present disclosure, an organic electroluminescent device having low driving voltage, high luminous efficiency, and/or improved lifespan characteristics can be provided.

The present disclosure relates to an organic electroluminescent compound, and an organic electroluminescent device comprising the same. By comprising the organic electroluminescent compound of the present disclosure, an organic electroluminescent device having improved driving voltage, luminous efficiency, lifespan characteristic, and/or power efficiency can be provided.

The present disclosure relates to the fields of near-infrared surgical navigation fluorescent molecules, cell marker imaging and so on, and in particular discloses an active targeting near-infrared fluorescent small molecule structure and a preparation method thereof. The present disclosure prepares the active targeting near-infrared fluorescent small molecule with pemetrexed disodium and derivatives thereof as active targeting groups by utilizing an organic total synthesis method. Such active targeting near-infrared fluorescent molecule has the advantages of high active targeting property, strong specificity, good water solubility, high fluorescence quantum yield and so on.