Organometallic compound, organic light-emitting device including the same, and diagnostic composition including the organometallic compound

1. An organometallic compound represented by Formula 1:

wherein, in Formula 1,

M 1 is beryllium, magnesium, aluminum, calcium, titanium, manganese, cobalt, copper, zinc, gallium, germanium, zirconium, rhutenium, rhodium, palladium, silver, rhenium, platinum, or gold,

X 1 is N, O, or S,

ring A 1 and ring A 3 are each independently a C 5 -C 30 carbocyclic group or a C 2 -C 30 heterocyclic group,

ring A 2 and ring A 4 are each independently a N-containing C 2 -C 30 heterocyclic group,

T 1 is *—N[(L 1 ) a1 -(R 1 ) b1 ]—*′, *—B(R 1 )—*′, *—P(R 1 )—*′, *—C(R 1 )(R 2 )—*′, *—Si(R 1 )(R 2 )—*′, *—Ge(R 1 )(R 2 )—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O) 2 —*′, *—C(R 1 )═C(R 2 )—*′, *—C(═S)—*′, or *—C≡C—*′,

L 1 is a single bond, a substituted or unsubstituted C 5 -C 30 carbocyclic group, or a substituted or unsubstituted C 2 -C 30 heterocyclic group,

a1 is an integer from 1 to 3, wherein, when a1 is 2 or more, two or more L 1 are identical to or different from each other,

R 1 and R 2 are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 10 cycloalkyl group, a substituted or unsubstituted C 2 -C 10 heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10 cycloalkenyl group, a substituted or unsubstituted C 2 -C 10 heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 1 -C 60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), or —P(═O)(Q 8 )(Q 9 ),

R 10 , R 20 , R 30 , and R 40 are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 3 -C 10 cycloalkyl group, a substituted or unsubstituted C 2 -C 10 heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10 cycloalkenyl group, a substituted or unsubstituted C 2 -C 10 heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 1 -C 60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group,- or —P(═O)(Q 8 )(Q 9 ),

provided that when R 10 , R 20 , R 30 , or R 40 is a substituted or unsubstituted C 1 -C 60 heteroaryl group, then the substituted or unsubstituted C 1 -C 60 heteroaryl group is selected from Formulae 10-76 to 10-78, 10-86 to 10-128, 10-131 to 10-139, 10-148 to 10-154, 10-157 to 10-161, and 10-183 to 10-194,

two neighboring groups among R 1 , R 2 , R 10 , R 20 , R 30 , and R 40 are optionally linked to form a substituted or unsubstituted C 5 -C 30 carbocyclic group or a substituted or unsubstituted C 2 -C 30 heterocyclic group,

b1 is an integer from 1 to 5, wherein, when b1 is 2 or more, two or more R 1 are identical to or different from each other,

b10 and b40 are each independently an integer from 1 to 4,

b20 and b30 are each independently an integer from 1 to 3,

when b10 is 2 or more, two or more R 10 are identical to or different from each other, when b20 is 2 or more, two or more R 20 are identical to or different from each other, when b30 is 2 or more, two or more R 30 are identical to or different from each other, and when b40 is 2 or more, two or more R 40 are identical to or different from each other,

a substituent of the substituted C 5 -C 30 carbocyclic group, the substituted C 2 -C 30 heterocyclic group, the substituted C 1 -C 60 alkyl group, the substituted C 2 -C 60 alkenyl group, the substituted C 2 -C 60 alkynyl group, the substituted C 1 -C 60 alkoxy group, the substituted C 3 -C 10 cycloalkyl group, the substituted C 2 -C 10 heterocycloalkyl group, the substituted C 3 -C 10 cycloalkenyl group, the substituted C 2 -C 10 heterocycloalkenyl group, the substituted C 6 -C 60 aryl group, the substituted C 6 -C 60 aryloxy group, the substituted C 6 -C 60 arylthio group, the substituted C 1 -C 60 heteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is

deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 1 -C 60 alkoxy group, or a combination thereof;

a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 1 -C 60 alkoxy group, or a combination thereof, each substituted with deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10 cycloalkyl group, a C 2 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Si(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), —P(═O)(Q 18 )(Q 19 ), or a combination thereof;

a C 3 -C 10 cycloalkyl group, a C 2 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof;

a C 3 -C 10 cycloalkyl group, a C 2 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof, each substituted with deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 1 -C 60 alkoxy group, a C 3 -C 10 cycloalkyl group, a C 2 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Si(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), —P(═O)(Q 28 )(Q 29 ), or a combination thereof; and

—N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), —P(═O)(Q 38 )(Q 39 ), or a combination thereof, and

Q 1 to Q 9 , Q 11 to Q 19 , Q 21 to Q 29 , and Q 31 to Q 39 are each independently hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 1 -C 60 alkoxy group, a C 3 -C 10 cycloalkyl group, a C 2 -C 10 heterocycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group substituted with a C 1 -C 60 alkyl group, and a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof, a C 6 -C 60 aryl group, or a combination thereof.

2. The organometallic compound of claim 1 , wherein

M 1 is Pt, Pd, or Au.

3. The organometallic compound of claim 1 , wherein

ring A 1 and ring A 3 are each independently

i) a 6-membered ring,

ii) a condensed ring in which two or more 6-membered rings are condensed with each other, and

iii) a condensed ring in which a 6-membered ring and a 5-membered ring are condensed with each other,

wherein each 6-membered ring in i), ii), and iii) is a benzene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, or a triazine group, and

each 5-membered ring in iii) is a cyclopentadiene group, a furan group, a thiophene group, a pyrrole group, a silole group, an oxazole group, an isoxazole group, an oxadiazole group, an isoxadiazole group, an oxatriazole group, an isoxatriazole group, a thiazole group, an isothiazole group, a thiadiazole group, an isothiadiazole group, a thiatriazole group, an isothiatriazole group, a pyrazole group, an imidazole group, a triazole group, a tetrazole group, an azasilole group, a diazasilole group, or a triazasilole group.

4. The organometallic compound of claim 1 , wherein

ring A 2 and ring A 4 are each independently a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a furopyridine group, a thienopyridine group, an azafluorene group, an azacarbazole group, an azadibenzofuran group, an azadibenzothiophene group, an azadibenzosilole group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, a tetrazole group, an oxazole group, an isoxazole group, a thiazole group, an isothiazole group, an oxadiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, an indazole group, a benzoxazole group, a benzothiazole group, a benzoxadiazole group, a benzothiadiazole group, a benzotriazole group, a diazaindene group, or a triazaindene group.

5. The organometallic compound of claim 1 , wherein

X 1 is O or S.

6. The organometallic compound of claim 1 , wherein

T 1 is *—N[(L 1 ) a1 -(R 1 ) b1 ]—*′, *—C(R 1 )(R 2 )—*′, *—O—*′, or *—S—*′.

7. The organometallic compound of claim 1 , wherein

L 1 is

a single bond, a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, or a pentacenylene group; or

a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, or a pentacenylene group, each substituted with deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 1 -C 60 alkoxy group, a C 3 -C 10 cycloalkyl group, a C 3 -C 10 cycloalkenyl group, a C 2 -C 10 heterocycloalkyl group, a C 2 -C 10 heterocycloalkenyl group, a C 6 -C 60 aryl group, a C 6 -C 60 aryloxy group, a C 6 -C 60 arylthio group, a C 1 -C 60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, or a combination thereof,

R 1 and R 2 are each independently

a C 1 -C 30 alkyl group;

a C 1 -C 30 alkyl group substituted with deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10 alkyl group, a C 1 -C 10 alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantyl group, a norbornyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or a combination thereof;

a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantyl group, a norbornyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group; or

a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, or an imidazopyrimidinyl group, each substituted with deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10 alkyl group, a C 1 -C 10 alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantyl group, a norbornyl group, a norbornenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, or a combination thereof.

8. The organometallic compound of claim 1 , wherein

L 1 is a single bond or a group represented by Formulae 3-1 to 3-3:

wherein, in Formulae 3-1 to 3-3,

Z 1 is hydrogen, deuterium, a C 1 -C 10 alkyl group, a phenyl group, a biphenyl group, or a terphenyl group,

d4 is an integer from 0 to 4, and

and *′ each indicate a binding site to a neighboring atom.

9. The organometallic compound of claim 1 , wherein

R 1 and R 2 , are each independently hydrogen, deuterium, —F, a cyano group, a nitro group, —SF 5 , —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a group represented by Formulae 9-1 to 9-19, or a group represented by Formulae 10-1 to 10-194, and

R 10 , R 20 , R 30 , and R 40 are each independently hydrogen, deuterium, —F, a cyano group, a nitro group, —SF 5 , —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a group represented by Formulae 9-1 to 9-19, or a group represented by Formulae 10-76 to 10-78, 10-86 to 10-128, 10-131 to 10-139, 10-148 to 10-154, 10-157 to 10-161, and 10-183 to 10-194:

wherein, in Formulae 9-1 to 9-19 and 10-1 to 10-194, * indicates a binding site to a neighboring atom, Ph indicates a phenyl group, and TMS indicates a trimethylsilyl group.

10. The organometallic compound of claim 9 , wherein

R 10 is a group represented by Formulae 9-1 to 9-19.

11. The organometallic compound of claim 9 , wherein

R 20 , R 30 , and R 40 is a group represented by Formulae 10-76 to 10-78, 10-86 to 10-128, 10-131 to 10-139, 10-148 to 10-154, 10-157 to 10-161, and 10-183 to 10-194.

12. The organometallic compound of claim 1 , wherein

a moiety represented by

in Formula 1 is represented by

wherein, in Formulae A 4 -1 to A 4 -10,

X 2 is O, S, or N(R 5 ),

Y 1 is N or C(R 41 ), Y 2 is N or C(R 42 ), Y 3 is N or C(R 43 ), Y 4 is N or C(R 44 ),

Y 5 is N or C(R 55 ), Y 6 is N or C(R 56 ), Y 7 is N or C(R 57 ), Y 8 is N or C(R 58 ),

R 5 , R 41 to R 44 , and R 55 to R 58 are each independently the same as defined in connection with R 40 in claim 1 , and

and *′ each indicate a binding site to a neighboring atom.

13. The organometallic compound of claim 1 , wherein

the organometallic compound represented by Formula 1 is represented by Formulae 1-1 or 1-2:

wherein, in Formulae 1-1 and 1-2,

M 1 , X 1 , and T 1 are each independently the same as described in claim 1 ,

X 2 is O, S, or N(R 5 ),

Y 1 is N or C(R 41 ), Y 2 is N or C(R 42 ), Y 3 is N or C(R 43 ), Y 4 is N or C(R 44 ),

Y 5 is N or C(R 55 ), Y 6 is N or C(R 56 ),

R 11 to R 14 are each independently the same as defined in connection with R 10 in claim 1 ,

R 21 to R 23 are each independently the same as defined in connection with R 20 in claim 1 ,

R 31 to R 33 are each independently the same as defined in connection with R 30 in claim 1 ,

R 5 , R 41 to R 44 , R 55 , and R 56 are each independently the same as defined in connection with R 40 in claim 1 , and

two or more groups of R 11 to R 14 , R 21 to R 23 , R 31 to R 33 , R 41 to R 44 , R 55 , and R 56 are optionally linked to form a benzene ring or a naphthalene ring.

14. The organometallic compound of claim 1 , wherein the organometallic compound is of Compounds 1 to 9:

wherein, in Compounds 1 to 9, Ph indicates a phenyl group.

15. An organic light-emitting device comprising:

a first electrode;

a second electrode; and

an organic layer between the first electrode and the second electrode and comprising an emission layer,

wherein the organic layer comprises an organometallic compound represented by Formula 1 of claim 1 .

16. The organic light-emitting device of claim 15 , wherein

the first electrode is an anode,

the second electrode is a cathode,

the organic layer further comprises a hole transport region between the first electrode and the emission layer and an electron transport region between the emission layer and the second electrode,

the hole transport region comprises a hole injection layer, a hole transport layer, an electron blocking layer, or any combination thereof, and

the electron transport region comprises a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof.

17. The organic light-emitting device of claim 15 , wherein

the emission layer comprises the organometallic compound.

18. The organic light-emitting device of claim 17 , wherein

the emission layer further comprises a host, and an amount of the host is greater than that of organometallic compound.

19. The organic light-emitting device of claim 18 , wherein

the emission layer emits red light having a maximum emission wavelength in a range of about 580 nanometers to about 680 nanometers.

20. A diagnostic composition comprising the organometallic compound of claim 1 .