Light emitting devices and compouds

A TADF compound according to formula I:

• wherein the ring II:
• represents an aromatic spacer ring with each Het bonded to adjacent carbon atoms and each moiety D bonded to adjacent carbon atoms, and
• wherein each Het is an aromatic heterocyclic acceptor moiety and each D is a donor moiety
• wherein the compound formula I is according to ring III:
• wherein R* is, independently for each occurrence, selected from the group consisting of —H, alkyl, aryl or heteroaryl,
• the aromatic heterocyclic acceptor moieties Het are, independently for each occurrence selected from the group consisting of:
• wherein-L represents the bonding position to ring II or III, X represents O, S or NR2 and groups R2 are, independently for each occurrence, selected from the group consisting of —H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated;
• substituted or unsubstituted aryl or heteroaryl;
• wherein groups R1 are, independently for each occurrence, selected from the group consisting of —H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated;
• substituted or unsubstituted aryl or heteroaryl, —CF3, —OMe, —SF5, —NO2, halo, aryl, aryl hydroxy, amino, alkoxy, alkylthio, carboxy, cyano, thio, formyl, ester, acyl, thioacyl, amido, sulfonamido and carbamate, and
• wherein donor moieties D are independently for each occurrence selected from:
• wherein -L represents the bonding position to ring II or III that is para to the nitrogen in structures C, D, G and H;
• X1 is selected from the group consisting of O, S, NR, SiR2, PR and CR2, wherein each R is independently selected from the group consisting of —H, alkyl, aryl or heteroaryl;
• each Ar is independently for each occurrence selected from the group consisting of substituted or unsubstituted aryl or heteroaryl;
• and
• represents, independently for each occurrence a substituted or unsubstituted aryl or heteroaryl ring fused to the central ring of structures A, B,C, D, E or F, inclusive of a five or a six membered substituted or unsubstituted aryl or heteroaryl ring;
• and
• n ( )indicates the optional presence of saturated —CH2— groups in the rings annelated to the benzene ring, wherein n is independently for each occurrence, 0, 1, or 2.