Donor-acceptor type thermally activated delayed fluorescent materials based on imidazo[1,2-f]phenanthridine and analogues

A compound represented by General Formula I:

• wherein:
• each occurrence of Donor represents no substitution or represents a group of Formula A, provided that at least one Donor represents a group of Formula A:
• wherein, in Formula A, * and #represent bonds to adjacent positions on General Formula I:
• represents hydrogen, cyanide, halogen, hydroxy, amino, nitro, thiol, or substituted or unsubstituted:
• C1-C4 alkyl, alkoxy, or aryl;
• or two adjacent groups R4 together form a group of Formula B
• wherein, in Formula B, ‡ and § represent bonds to adjacent positions on Formula A;
• each U1 and U4 independently represents O, S, CRR′, SiRR′, or NAr*, where R and R′ each independently represents hydrogen, cyanide, halogen, hydroxy, amino, nitro, thiol, or optionally substituted C1-C4 alkyl, alkoxy, or aryl, and Ar* represents a substituted or unsubstituted:
• phenyl, pyridyl, naphthyl, pyrimidyl, pyridazinyl, pyrazinyl, pyrazolyl, imidazolyl, oxazolyl, or thiazolyl ring, and Ar* is optionally covalently bonded to V2 to form one or more 5-membered or 6-membered rings,
• R1, R2, R3, and R5 each independently represents hydrogen, cyanide, halogen, hydroxy, amino, nitro, thiol, or substituted or unsubstituted;
• C1-C4 alkyl, alkoxy, or aryl, and
• V2 represents N or substituted or unsubstituted C,
• each X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11, X12, X13, X14, X15, X16, X17, and X18 independently represents substituted or unsubstituted;
• C, N, Si, O, or S, valency permitting,
• each n is independently an integer as permitted by valence, and
• wherein at least one of the following conditions (i) and (ii) is true:
• (i) at least two occurrences of Donor represent a group of Formula A;
• or
• (ii) at least two adjacent groups R4 together form a group of Formula B.