Azafluorenone was discovered decades ago and its derivatives have received widespread attention in various research fields. However, the application of azafluorenone and its derivatives in organic light-emitting diode (OLED) materials is rarely reported and the related device performance is still not satisfactory. In this work, 1,4-diazafluorenone and its two analogues were prepared as precursors and three novel spiro compounds, SAIP, SAIQ, and SABIQ, were synthesized. The basic physical and chemical properties of SAIP, SAIQ, and SABIQ were studied in detail. From SAIP to SAIQ and SABIQ, the triplet energies (ETs) and optical band gaps (Egs) decrease gradually with the extension of the intramolecular conjugation length. In addition, blue/green/red and green/red phosphorescent OLEDs (PHOLEDs) were fabricated with SAIP and SAIQ as host materials, respectively. It is worth noting that all green and red devices based on SAIP or SAIQ showed a relatively high device performance with maximum external quantum efficiencies (EQEs) of 17.8% and 21.4%, respectively. These results further show the high potential of azafluorenone and its analogues in the building of efficient host materials.

Diazaspirocycles: novel platforms for efficient phosphorescent organic light-emitting diodes

The triplet excited state of 4,5-diaza-9-fluorenone (1) shows absorption maxima at 410 and 470 nm and a lifetime of 3 μs, in acetonitrile Its intersystem crossing quantum yield was determined using 9-fluorenone as a secondary standard and a value of 041 ± 001 was obtained The reactivity of the triplet excited state of 1 towards several quenchers, in acetonitrile, was investigated employing the laser flash photolysis technique quenching rate constants ranging from 79 × 104 M−1 s−1 (2-propanol) to 10 × 1010 M−1 s−1 (triethylamine) were obtained From the quenching rate constants obtained one can conclude that 4,5-diaza-9-fluorenone has a ππ* triplet excited state A Hammett plot for the quenching rate constants of triplet 1 by phenols containing polar substituents against σ + gave a reaction constant ρ of –154 ± 010, which demonstrates the electrophilic character of the 4,5-diaza-9-fluorenone triplet excited state

Laser flash photolysis study of the photochemistry of 4,5-diaza-9-fluorenone

The photoreduction by amines and N-phenylglycine, NPG, of six styrylquinoxalin-2(1 H)-ones derivatives substituted in the styryl moiety, R-SQ, was studied by using flash photolysis. The photoreaction is initiated via a single electron transfer from the electron donor (amines or NPG) to R-SQ excited triplet state, 3R-SQ*, with the formation of a triplet state radical ion pair or a charge transfer exciplex, 3[CRIP/CTE]. These species live longer than the respective 3R-SQ* and have very similar transient spectra. In the presence of NPG, these 3[CRIP/CTE] evolve on μs time scale to the respective hydrogenated radicals, R-SQH•, whose transient spectra and reaction rate constants with NPG are reported. The identity of these hydrogenated radicals was supported by the spectra obtained with the α-H donor triethylamine and previous pulse radiolysis studies in 2-propanol. Our findings allow proposing a radical chain reaction mechanism that explains the observed spectral behavior and rationalizes formation of the main product formed by binding of four PhNHCH2• derived from NPG decarboxylation.

Spectral and Kinetic Study of 3-Styrylquinoxalin-2(1 H)-ones Photoreduced by N-Phenylglycine and Amines.

https://www.teses.usp.br/teses/disponiveis/75/75131/tde-24022014-114205/publico/LeticiaFelipeAbdiasPinto_Revisado.pdf

Preparação e caracterização fotoquímica de derivado de S,S-dioxidotioxantona: aplicações em fotopolimerização

The effect of the introduction of nitrogen atoms upon the triplet excited state reactivity of 1,4-diaza-9-fluorenone (1) and 1,4-diaza-9-benz[b]fluorenone (2), in acetonitrile, was investigated employing the nanosecond laser flash photolysis technique. The intersystem crossing quantum yield (Φces) for 1 and 2 was determined using 9-fluorenone as a secondary standard (Φces= 0.48, in acetonitrile) and for both diazafluorenones a value of Φces= 0.28 was found. Quenching rate constants ranged from 8.17x104 L mol-1 s-1 (2-propanol) to 1.02x1010 L mol-1 s-1 (DABCO) for 1,4-diaza-9-fluorenone and from 6.95x105 L mol-1 s-1 (2-propanol) to 5.94x109 L mol-1 s-1 (DABCO) for 1,4-diaza-9-benz[b]fluorenone, depending if the quenching process involves energy, hydrogen or electron transfer. A comparison between quenching rate constants for both diazaflurenones and the parent compound, i.e. 9-fluorenone, a ketone with lowest triple state of ππ* configuration, lead to the conclusion that the reactive triplet excited state for 1,4-diaza-9-fluorenone and 1,4-diaza-9-benz[b]fluorenone has ππ* configuration.

/pdf/estudo-da-reatividade-do-estado-excitado-triplete-de-1-4-4r09tdxs0l.pdf

Andreza A. C. Takaizumi

Papers

Estudo da reatividade do estado excitado triplete de 1,4-diaza-9-fluorenonas frente a doadores de hidrogênio e de elétron