Organic electroluminescent materials and devices
Provided is a compound comprising a structure of wherein the variables are defined herein.
1. A compound comprising a structure of
wherein:
M is BR 1 R 2 or ZnR 3 R 4 ;
X 1 -X 4 , and X 7 -X 9 are each independently CR or N with R being the same or different;
X 5 and X 6 are each independently CR, N, or NR with R being the same or different;
the bond between X 5 and X 6 is either a single bond or a double bond;
R, R 1 , R 2 , R 3 , and R 4 are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and
any two adjacent R, R 1 , R 2 , R 3 , or R 4 can be joined or fused to form a ring.
2. The compound of claim 1 , wherein the bond between X 5 and X 6 is a double bond.
3. The compound of claim 1 , wherein the bond between X 5 and X 6 is a double bond with both X 5 and X 6 being CR.
4. The compound of claim 3 , wherein the two R substituents are joined together to form a fused ring.
5. The compound of claim 1 , wherein the bond between X 5 and X 6 is a single bond, and X 5 is NR with R forming a fused ring with ring A, or X 6 is CR with R forming a fused ring with ring C.
6. The compound of claim 1 , wherein R, R 1 , R 2 , R 3 , and R 4 are each independently a hydrogen or a substituent selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.
7. The compound of claim 1 , wherein M is BR 1 R 2 .
8. The compound of claim 1 , wherein R 1 and R 2 are each independently selected from the group consisting of halogen, alkyl, aryl, heteroaryl and combinations thereof.
9. The compound of claim 1 , wherein M is ZnR 3 R 4 .
10. The compound of claim 9 , wherein R 3 and R 4 are selected from the group consisting of halogen, alkyl, aryl, heteroaryl, carboxylate, acetylacetonate, and combinations thereof.
11. The compound of claim 1 , wherein the compound has a structure of
12. The compound of claim 1 , wherein the structure of Formula I is selected from the group consisting of:
wherein X 10 -X 23 are each independently N or CR; Y A for each occurrence is independently selected from the group consisting of BR e , NR e , PR e , O, S, Se, C═O, S═O, SO 2 , CR e R f , SiR e R f , and GeR e R f ; R e and R f can be fused or joined to form a ring; R e and R f are each independently hydrogen or a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and two adjacent R can be fused or joined to form a ring.
13. The compound of claim 1 , wherein LA-M portion represents the structure of Formula I, wherein M is the same M in Formula I and L A represents the remaining structure in Formula I, and the compound can be selected from the group consisting of L A -M-L A , L A -M-L C , and L A -M-L B , wherein in L A -M-L A and L A -M-L C , M is Zn, and in L A -M-L B M is B,
wherein L A -M portion is selected from the group consisting of: L A I-(Ri)(Rj)(Rk), L A II-(Ri)(Rj)(Rk), L A III-(Ri)(Rj), L A IV-(Ri)(Rj)(Rk), L A V-(Ri)(Rj)(Rk), L A VI-(Ri)(Rj), L A VII-(Ri)(Rj), L A VIII-(Ri)(Rj), L A IX-(Ri)(Rj), L A X-(Ri)(Rj)(Rk), L A XI-(Ri)(Rj)(Rk), L A XII-(Ri)(Rj), L A XIII-(Ri)(Rj), L A XIV-(Ri)(Rj), L A XV-(Ri)(Rj)(Rk), L A XVI-(Ri)(Rj)(Rk), L A XVII-(Ri)(Rj)(Rk), L A XVIII-(Ri)(Rj), L A XIX-(Ri)(Rj), L A XX-(Ri)(Rj), L A XXI-(Ri)(Rj), L A XXII-(Ri)(Rj)(Rk), L A XXIII-(Ri)(Rj), L A XXIV-(Ri)(Rj), L A XXV-(Ri)(Rj)(Rk), L A XXVI-(Ri)(Rj)(Rk), L A XXVII-(Ri)(Rj)(Rk), L A XXVIII-(Ri)(Rj), L A XXIX-(Ri)(Rj), L A XXX-(Ri)(Rj), L A XXXI-(Ri)(Rj), L A XXXII-(Ri)(Rj)(Rk), L A XXXIII-(Ri)(Rj), L A XXXIV-(Ri)(Rj), L A XXXV-(Ri)(Rj)(Rk), L A XXXVI-(Ri)(Rj)(Rk), L A XXXVII-(Ri)(Rj)(Rk), L A XXXVIII-(Ri)(Rj), L A XXXIX-(Ri)(Rj), L A XL-(Ri)(Rj), L A XLI-(Ri)(Rj)(Rk), L A XLII-(Ri)(Rj), L A XLIII-(Ri)(Rj), L A XLIV-(Ri)(Rj), L A XLV-(Ri)(Rj)(Rk)(Rl), L A XLVI-(Ri)(Rj)(Rk)(Rl), L A XLVII-(Ri)(Rj)(Rk)(Rl), L A XLVIII-(Ri)(Rj)(Rl), L A XLIX-(Ri)(Rj)(Rl), L A L-(Ri)(Rj)(Rl), L A LI-(Ri)(Rj)(Rl), L A LII-(Ri)(Rj)(Rk)(Rl), L A LIII-(Ri)(Rj)(Rk), L A LIV-(Ri)(Rj)(Rk), L A LV-(Ri)(Rj)(Rk), L A LVI-(Ri)(Rj)(Rk), L A LVII-(Ri)(Rj)(Rk), L A LVIII-(Ri)(Rj)(Rk), L A LIX-(Ri)(Rj)(Rk), L A LX-(Ri)(Rj)(Rk), L A LXI-(Ri)(Rj)(Rk), and L A LXII-(Ri)(Rj)(Rk), wherein i, j, and k are independently an integer from 1 to 60, and l is an integer from 1 to 50, wherein
L A -M portion
Structure
for L A I-(Ri)(Rj)(Rk), L A I-(Rl)(Rl)(Rl) to L A I- (R60)(R60)(R60) having the structure
for L A II-(Ri)(Rj)(Rk), L A II-(Rl)(Rl)(Rl) to L A II- (R60)(R60)(R60) having the structure
for L A III-(Ri)(Rj), L A III-(Rl)(Rl) to L A III-(R60)(R60) having the structure
for L A IV-(Ri)(Rj)(Rk), L A IV-(Rl)(Rl)(Rl) to L A IV- (R60)(R60)(R60) having the structure
for L A V-(Ri)(Rj)(Rk), L A V-(Rl)(Rl)(Rl) to L A V- (R60)(R60)(R60) having the structure
for L A VI-(Ri)(Rj), L A VI-(Rl)(Rl) to L A VI-(R60)(R60) having the structure
for L A VII-(Ri)(Rj), L A VII-(Rl)(Rl) to L A VII-(R60)(R60) having the structure
for L A VIII-(Ri)(Rj), L A VIII-(Rl)(Rl) to L A VIII-(R60)(R60) having the structure
for L A IX-(Ri)(Rj), L A IX-(Rl)(Rl) to L A IX-(R60)(R60) having the structure
for L A X-(Ri)(Rj)(Rk), L A X-(Rl)(Rl)(Rl) to L A X- (R60)(R60)(R60) having the structure
for L A XI-(Ri)(Rj)(Rk), L A XI-(Rl)(Rl)(Rl) to L A XI- (R60)(R60)(R60) having the structure
for L A XII-(Ri)(Rj), L A XII-(Rl)(Rl) to L A XII-(R60)(R60) having the structure
for L A XIII-(Ri)(Rj), L A XIII-(Rl)(Rl) to L A XIII-(R60)(R60) having the structure
for L A XIV-(Ri)(Rj), L A XIV-(Rl)(Rl) to L A XIV-(R60)(R60) having the structure
for L A XV-(Ri)(Rj)(Rk), L A XV-(Rl)(Rl)(Rl) to L A XV- (R60)(R60)(R60) having the structure
for L A XVI-(Ri)(Rj)(Rk), L A XVI-(Rl)(Rl)(Rl) to L A XVI- (R60)(R60)(R60) having the structure
for L A XVII-(Ri)(Rj)(Rk), L A XVII-(Rl)(Rl)(Rl) to L A XVII- (R60)(R60)(R60) having the structure
for L A XVIII-(Ri)(Rj), L A XVIII-(Rl)(Rl) to L A XVIII- (R60)(R60) having the structure
for L A XIX-(Ri)(Rj), L A XIX-(Rl)(Rl) to L A XIX-(R60)(R60) having the structure
for L A XX-(Ri)(Rj), L A XX-(Rl)(Rl) to L A XX-(R60)(R60) having the structure
for L A XXI-(Ri)(Rj), L A XXI-(Rl)(Rl) to L A XXI-(R60)(R60) having the structure
for L A XXII-(Ri)(Rj)(Rk), L A XXII-(Rl)(Rl)(Rl) to L A XXII- (R60)(R60)(R60) having the structure
for L A XXIII-(Ri)(Rj), L A XXIII-(Rl)(Rl) to L A XXIII- (R60)(R60) having the structure
for L A XXIV-(Ri)(Rj), L A XXIV-(Rl)(Rl) to L A XXIV- (R60)(R60) having the structure
for L A XXV-(Ri)(Rj)(Rk), L A XXV-(Rl)(Rl)(Rl) to L A XXV- (R60)(R60)(R60) having the structure
for L A XXVI-(Ri)(Rj)(Rk), L A XXVI-(Rl)(Rl)(Rl) to L A XXVI- (R60)(R60)(R60) having the structure
for L A XXVII-(Ri)(Rj)(Rk), L A XXVII-(Rl)(Rl)(Rl) to L A XXVII-(R60)(R60)(R60) having the structure
for L A XXVIII-(Ri)(Rj), L A XXVIII-(Rl)(Rl) to L A XXVIII- (R60)(R60) having the structure
for L A XXIX-(Ri)(Rj), L A XXIX-(Rl)(Rl) to L A XXIX- (R60)(R60) having the structure
for L A XXX-(Ri)(Rj), L A XXX-(Rl)(Rl) to Compound XXX- (R60)(R60) having the structure
for L A XXXI-(Ri)(Rj), L A XXXI-(Rl)(Rl) to L A XXXI- (R60)(R60) having the structure
for L A XXXII-(Ri)(Rj)(Rk), L A XXXII-(Rl)(Rl)(Rl) to L A XXXII-(R60)(R60)(R60) having the structure
for L A XXXIII-(Ri)(Rj), L A XXXIII-(Rl)(Rl) to L A XXXIII- (R60)(R60) having the structure
for L A XXXIV-(Ri)(Rj), L A XXXIV-(Rl)(Rl) to L A XXXIV- (R60)(R60) having the structure
for L A XXXV-(Ri)(Rj)(Rk), L A XXXV-(Rl)(Rl)(Rl) to L A XXXV-(R60)(R60)(R60) having the structure
for L A XXXVI-(Ri)(Rj)(Rk), L A XXXVI-(Rl)(Rl)(Rl) to L A XXXVI-(R60)(R60)(R60) having the structure
for L A XXXVII-(Ri)(Rj)(Rk), L A XXXVII-(Rl)(Rl)(Rl) to L A XXXVII-(R60)(R60)(R60) having the structure
for L A XXXVIII-(Ri)(Rj), L A XXXVIII-(Rl)(Rl) to L A XXXVIII-(R60)(R60) having the structure
for L A XXXIX-(Ri)(Rj), L A XXXIX-(Rl)(Rl) to L A I-(R60)(R60) having the structure
for L A XL-(Ri)(Rj), L A XL-(Rl)(Rl) to L A XL-(R60)(R60) having the structure
for L A XLI-(Ri)(Rj)(Rk), L A XLI-(Rl)(Rl)(Rl) to L A XLI- (R60)(R60)(R60) having the structure
for L A XLII-(Ri)(Rj), L A XLII-(Rl)(Rl) to L A XLII-(R60)(R60) having the structure
for L A XLIII-(Ri)(Rj), L A XLIII-(Rl)(Rl) to L A XLIII- (R60)(R60) having the structure
for L A XLIV-(Ri)(Rj), L A XLIV-(Rl)(Rl) to L A XLIV- (R60)(R60) having the structure
for L A XLV-(Ri)(Rj)(Rk)(Rl), L A XLV-(Rl)(Rl)(Rl)(Rl) to L A XLV-(R60)(R60)(R60)(R50) having the structure
for L A XLVI-(Ri)(Rj)(Rk)(Rl), L A XLVI-(Rl)(Rl)(Rl)(Rl) to L A XLVI-(R60)(R60)(R60)(R50) having the structure
for L A XLVII-(Ri)(Rj)(Rk)(Rl), L A XLVII-(Rl)(Rl)(Rl)(Rl) to L A XLVII-(R60)(R60)(R60)(R50) having the structure
for L A XLVIII-(Ri)(Rj)(Rl), L A XLVIII-(Rl)(Rl)(Rl) to L A XLVIII-(R60)(R60)(R50) having the structure
for L A XLIX-(Ri)(Rj)(Rl), L A XLIX-(Rl)(Rl)(Rl) to L A XLIX- (R60)(R60)(R50) having the structure
for L A L-(Ri)(Rj)(Rl), L A L-(Rl)(Rl)(Rl) to L A L- (R60)(R60)(R50) having the structure
for L A LI-(Ri)(Rj)(Rl), L A LI-(Rl)(Rl)(Rl) to L A LI- (R60)(R60)(R50) having the structure
for L A LII-(Ri)(Rj)(Rk)(Rl), L A LII-(Rl)(Rl)(Rl)(Rl) to L A LII- (R60)(R60)(R60)(R50) having the structure
for L A LIII-(Ri)(Rj)(Rl), L A LIII-(Rl)(Rl)(Rl) to L A LIII- (R60)(R60)(R50) having the structure
for L A LIV-(Ri)(Rj)(Rl), L A LIV-(Rl)(Rl)(Rl) to L A LIV- (R60)(R60)(R50) having the structure
for L A LV-(Ri)(Rj)(Rk)(Rl), L A LV-(Rl)(Rl)(Rl)(Rl) to L A LV- (R60)(R60)(R60)(R60) having the structure
for L A LVI-(Ri)(Rj)(Rk)(Rl), L A LVI-(Rl)(Rl)(Rl)(Rl) to L A LVI-(R60)(R60)(R60)(R60) having the structure
for L A LVII-(Ri)(Rj)(Rk), L A LVII-(Rl)(Rl)(Rl) to L A LVII- (R60)(R60)(R60) having the structure
for L A LVIII-(Ri)(Rj)(Rk), L A LVIII-(Rl)(Rl)(Rl) to L A LVIII- (R60)(R60)(R60) having the structure
for L A LIX-(Ri)(Rj)(Rk), L A LIX-(Rl)(Rl)(Rl) to L A LIX- (R60)(R60)(R60) having the structure
for L A LX-(Ri)(Rj)(Rk), L A LX-(Rl)(Rl)(Rl) to L A LX- (R60)(R60)(R60) having the structure
for L A LXI-(Ri)(Rj)(Rk), L A LXI-(Rl)(Rl)(Rl) to L A LIX- (R60)(R60)(R60) having the structure
for L A LXII-(Ri)(Rj)(Rk), L A LXII-(Rl)(Rl)(Rl) to L A LXII- (R60)(R60)(R60) having the structure
wherein M-L B portion is selected from the group consisting of: L B I, L B II-(Rx)(Ry), L B III-(Rx)(Ry), L B IV-(Rx)(Ry), L B V-(Rx)(Ry), L B VI-(Rx)(Ry), L B VII-(Rx)(Ry)(Rz), and L B VIII-(Rx)(Ry), wherein x and y are each independently an integer from 1 to 60, and z is an integer from 1 to 50, wherein:
M-L B portion
Structure
L B I having the structure
for L B II-(Rx)(Ry), L B II-(Rl)(Rl) to L B II-(R60)(R60) having the structure
for L B III-(Rx)(Ry), L B III-(Rl)(Rl) to L B III-(R60)(R60) having the structure
for L B IV-(Rx)(Ry), L B IV-(Rl)(Rl) to L B IV-(R60)(R60) having the structure
for L B V-(Rx)(Ry), L B V-(Rl)(Rl)(Rl) to L B V-(R60)(R60)(R60) having the structure
for L B VI-(Rx)(Ry), L B VI-(Rl)(Rl) to L B VI-(R60)(R60) having the structure
for L B VII-(Rx)(Ry)(Rz), L B VII-(Rl)(Rl)(Rl) to L B VII- (R60)(R60)(R50) having the structure
for L B VIII-(Rx)(Ry), L B VIII-(Rl)(Rl) to L B VIII-(R60)(R60) having the structure
wherein M-L C portion is selected from the group consisting of: L C I-(Rm)(Rn)(Ro), L C II-(Rm)(Rn), L C III-(Rm)(Rn)(Ro), L C IV-(Rm)(Rn)(Ro), L C V-(Rm)(Rn)(Ro), L C VI-(Rm)(Rn)(Ro), L C VII-(Rm)(Rn), L C VIII-(Rm)(Rn), L C IX-(Rm)(Rn), L C X-(Rm)(Rn), L C XI-(Rm)(Rn)(Ro), L C XII-(Rm)(Rn), L C XIII-(Rm)(Rn)(Ro), L C XIV-(Rm)(Rn), L C XV-(Rm)(Rn)(Ro), L C XVI-(Rm)(Rn), L C XVII-(Rm)(Rn)(Ro), and L C XIII-(Rm)(Rn)(Ro), wherein m, n, and o are each independently an integer from 1 to 60, wherein
M-L C portion
Structure
for L C I-(Rm)(Rn)(Ro), L C I-(Rl)(Rl)(Rl) to L C I- (R60)(R60)(R60) having the structure
for L C II-(Rm)(Rn), L C II-(Rl)(Rl) to L C II-(R60)(R60) having the structure
for L C III-(Rm)(Rn)(Ro), L C III-(Rl)(Rl)(Rl) to L C III- (R60)(R60)(R60) having the structure
for L C IV-(Rm)(Rn)(Ro), L C IV-(Rl)(Rl)(Rl) to L C IV- (R60)(R60)(R60) having the structure
for L C V-(Rm)(Rn)(Ro), L C V-(Rl)(Rl)(Rl) to L C V- (R60)(R60)(R60) having the structure
for L C VI-(Rm)(Rn)(Ro), L C VI-(Rl)(Rl)(Rl) to L C VI- (R60)(R60)(R60) having the structure
for L C VII-(Rm)(Rn), L C VII-(Rl)(Rl) to L C VII-(R60)(R60) having the structure
for L C VIII-(Rm)(Rn), L C VIII-(Rl)(Rl) to L C VIII-(R60)(R60) having the structure
for L C IX-(Rm)(Rn), L C IX-(Rl)(Rl) to L C IX-(R60)(R60) having the structure
for L C X-(Rm)(Rn), L C X-(Rl)(Rl) to L C X-(R60)(R60) having the structure
for L C XI-(Rm)(Rn)(Ro), L C XI-(Rl)(Rl)(Rl) to L C XI- (R60)(R60)(R60) having the structure
for L C XII-(Rm)(Rn), L C XII-(Rl)(Rl) to L C XII-(R60)(R60) having the structure
for L C XIII-(Rm)(Rn)(Ro), L C XIII-(Rl)(Rl)(Rl) to L C XIII- (R60)(R60)(R60) having the structure
for L C XIV-(Rm)(Rn), L C XIV-(Rl)(Rl) to L C XIV-(R60)(R60) having the structure
for L C XV-(Rm)(Rn)(Ro), L C XV-(Rl)(Rl)(Rl) to L C XV- (R60)(R60)(R60) having the structure
for L C XVI-(Rm)(Rn), L C XVI-(Rl)(Rl) to L C XVI-(R60)(R60) having the structure
for L C XVII-(Rm)(Rn)(Ro), L C XVII-(Rl)(Rl)(Rl) to L C XVII- (R60)(R60)(R60) having the structure
for L C XVIII-(Rm)(Rn), L C XVIII-(Rl)(Rl) to L C XVIII- (R60)(R60) having the structure
wherein R1 to R60 have the following structures:
14. The compound of claim 1 , wherein the compound of Formula I is selected from the group consisting of:
15. The compound of claim 1 , wherein the compound is selected from the group consisting of:
16. An organic light emitting device (OLED) comprising:
an anode;
a cathode; and
a first organic layer disposed between the anode and the cathode,
wherein the first organic layer comprises a compound of
wherein:
M is BR 1 R 2 or ZnR 3 R 4 ;
X 1 -X 4 , and X 7 -X 9 are each independently CR or N with R being the same or different;
X 5 and X 6 are each independently CR, N, or NR with R being the same or different;
the bond between X 5 and X 6 is either a single bond or a double bond;
R, R 1 , R 2 , R 3 , and R 4 are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and
any two adjacent R, R 1 , R 2 , R 3 , or R 4 can be joined or fused to form a ring.
17. The OLED of claim 16 , wherein the compound is a fluorescent emitter.
18. The OLED of claim 16 , wherein the first organic layer further comprises a phosphorescent sensitizer, and the compound is a fluorescent acceptor, wherein the phosphorescent sensitizer is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:
wherein:
T is B, Al, Ga, In;
each of Y 1 to Y 13 is independently selected from the group consisting of carbon and nitrogen;
Y′ is selected from the group consisting of BR e , NR e , PR e , O, S, Se, C═O, S═O, SO 2 , CR e R f , SiR e R f , and GeR e R f ;
R e and R f can be fused or joined to form a ring;
each R a , R b , R c , and R d independently represent zero, mono, or up to a maximum allowed number of substitutions to its associated ring;
each of R a1 , R b1 , R c1 , R d1 , R a , R b , R c , R d , R e and R f is independently a hydrogen or a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;
the general substituents defined herein; and
any two adjacent R a , R b , R c , R d , R e and R f can be fused or joined to form a ring or form a multidentate ligand.
19. The OLED of claim 16 , wherein one or more organic layers, disposed between the anode and cathode, comprise a host, wherein the host comprises at least one chemical moiety selected from the group consisting of triphenylene, carbazole, indolocarbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene, 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene, aza-triphenylene, aza-carbazole, aza-indolocarbazole, aza-dibenzothiophene, aza-dibenzofuran, aza-dibenzoselenophene, and aza-(5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene).
20. A consumer product comprising an organic light-emitting device (OLED) comprising:
an anode;
a cathode; and
an organic layer disposed between the anode and the cathode,
wherein the organic layer comprises a compound comprising a structure of
wherein:
M is BR 1 R 2 or ZnR 3 R 4 ;
X 1 -X 4 , and X 7 -X 9 are each independently CR or N with R being the same or different;
X 5 and X 6 are each independently CR, N, or NR with R being the same or different;
the bond between X 5 and X 6 is either a single bond or a double bond;
R, R 1 , R 2 , R 3 , and R 4 are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and
any two adjacent R, R 1 , R 2 , R 3 , or R 4 can be joined or fused to form a ring.