Four new luminescent organoboron complexes have been synthesized and fully characterized. These compounds are four-coordinate boron chelated by either 8-hydroxyquinolato (q) or functionalized 8-hydroxylquinolato ligands, including BPh2(5-(1-naphthyl)-q) (1), BPh2(5-(2-benzothienyl)-q) (2), B(2-benzothienyl)2q (3), and B(2-benzothienyl)2(2-Me-q) (4). All four compounds have a tetrahedral geometry as established by X-ray diffraction analyses. In solution, compounds 1-4 have an emission maximum at 534, 565, 501, and 496 nm, respectively, at room temperature. They emit similar colors in the solid states without red shifts of the emission band due to the lack of significant intermolecular interactions in the crystal lattices. The substituent group at C5 or C2 position of the 8-hydroxyquinolato ligand has been observed to have a significant impact on the emission energy and the emission quantum efficiency of the boron complexes. Molecular orbital calculations (Gaussian 98) showed that the electronic transition of 1 and 2 is a pi-pi* transition centered on the functionalized 8-hydroxyquinolato group and the electronic transition of 3 and 4 is an interligand charge transfer from the 2-benzothienyl ligand to the hydroxyquinolato ring. A double-layer electroluminescent device using 3 as the emitter has been fabricated, which produced a broad emission band with a significant contribution of exciplex emission.

Eight novel three-coordinate boron compounds with the general formula BAr(2)L, in which Ar is mesityl and L is a 7-azaindolyl- or a 2,2'-dipyridylamino-functionalized aryl or thienyl ligand, have been synthesized by Suzuki coupling, Ullmann condensation methods, or simple substitution reactions (L = p-(2,2'-dipyridylamino)phenyl, 1; p-(2,2'-dipyridylamino)biphenyl, 2; p-(7-azaindolyl)phenyl, 3; p-(7-azaindolyl)biphenyl, 4; 3,5-bis(2,2'-dipyridylamino)phenyl, 5; 3,5-bis(7-azaindolyl)phenyl, 6; p-[3,5-bis(2,2'-dipyridylamino)phenyl]phenyl, 7; 5-[p-(2,2'-dipyridylamino)phenyl]-2-thienyl, 8). The structures of 1, 3, and 5-7 have been determined by X-ray diffraction analyses. These new boron compounds are bright blue emitters. Electroluminescent devices using compound 2 or 8 as the emitter and the electron-transport layer have been successfully fabricated. Molecular orbital calculations (Gaussian 98) have established that the blue emission of compounds 1-8 originates from charge transfer between the pi orbital of the ligand L and the p(pi) orbital of the boron center. The ability of these boron compounds to bind to metal centers to form supramolecular assemblies was demonstrated by treatment of compound 2 with Zn(O(2)CCF(3))(2), which generated a 1:1 chelate complex [2.Zn(O(2)CCF(3))(2)] (10), and also by treatment of compound 4 with AgNO(3), yielding a 2:1 coordination compound [(4)(2).Ag(NO(3))] (11). In the solid state, compounds 10 and 11 form interesting head-to-head and tail-to-tail extended structures that host solvent molecules such as benzene.

New V-shaped bifunctional organosilicon compounds that contain an electron acceptor, B(Mes)2, and an electron donor, N(1-naph)Ph, with the formulae Ph2Si{p-C6H4B(Mes)2}{p-C6H4N(1-naph)ph)} (1), Ph2Si{p-C6H4(Mes)2}{p-biphenyl-N(1-naph)ph} (2), and Si{p-C6H4B(Mes)2}2{p-C6H4N(1-naph)ph)}2 (3) have been synthesized as model compounds for the investigation of through-space charge-transfer emission involving triarylboron and triarylamino centers. The photophysical properties of the new bifunctional organosilicon compounds are compared to two U-shaped compounds sBN and BN in which the boron acceptor and the amino donor groups are linked together by a rigid 1,10-naphthyl group. The results of our investigation establish that dual emission pathways, namely through-space donor-acceptor charge transfer and pi-pi* transitions coexist in the V-shaped molecules 1-3, while charge transfer emission is dominant in the U-shaped molecules. It is found that depending on the geometry of the linker and the BN separation distance, the compound either displays dual emission bands simultaneously or single emission band. In addition, the dual emission pathways in these molecules can be selectively switched on or off by using fluoride ions. The sensitivity of response to fluoride ions by these molecules is also found to be highly dependent on the geometry of the linker and the BN separation distance. The V-shaped molecules are found to be "turn-on" sensors to fluorides with a much higher sensitivity than the U-shaped molecules.

Six new diethynylsilane compounds with the general formula Si(C⋮C−R)2R‘2 (R = p - N-indolylphenyl, R‘ = Me, 1; R‘ = Ph, 2; R = p - N-7-azaindolylphenyl, R‘ = Me, 3; R‘ = Ph, 4; R = p-2,2‘-dipyridylaminophenyl, R‘ = Me, 5; R‘ = Ph, 6) have been synthesized and fully characterized. Compounds 1, 2, and 4 have been found to undergo intramolecular cyclization in the presence of Li-naphthyl to form the corresponding 2,5-dilithiosiloles, which after methylation by CH3I or undergoing Pd-catalyzed cross-coupling reactions with the appropriate arylbromide produced six new silole compounds:  1,1-diphenyl-2,5-dimethyl-3,4-bis(4-N-7-azaindoylphenyl)silole (7), 1,1-diphenyl-2,3,4,5-tetrakis(4-N-indoylphenyl)silole (8), 1,1-dimethyl-2,5-bis(4-N-7-azaindoylphenyl)-3,4-bis(4-N-indoylphenyl)silole (9), 1,1-dimethyl-2,5-bis(p-2,2‘-dipyridylaminophenyl)-3,4-(4-N-indoylphenyl)silole (10), 1,1-dimethyl-2,5-bis(4-(N-1-naphthylphenylamino)phenyl)-3,4-bis(4-N-indoylphenyl)silole (11), and 1,1-dimethyl-2,5-bis(4‘-(N-1-naphthylphenylamino)biphenyl)-3,4-bis(4-N-indoylphenyl)silole (12). Compounds 8−12 are a new class of silole molecules that are functionalized at the 2-, 3-, 4-, and 5-positions by indolylphenyl, 7-azaindolylphenyl, 2,2‘-dipyridylaminophenyl, (N-1-naphthyl)(N-phenyl)aminophenyl, or (N-1-naphthyl)(N-phenyl)aminobiphenyl. The structures of compounds 3, 5, and 8 were determined by single-crystal X-ray diffraction analysis. Siloles 8−12 emit a green color in solution and the solid state, while in contrast silole 7 emits a blue color with the emission maximum at 445 nm. The effects of substituent groups at different positions of the silole ring on structures and luminescent properties have been examined. A single-layer EL device with compound 11 being sandwiched between the ITO anode and the LiF/Al cathode layers has been fabricated successfully.