Probing the Effects of the Number and Positions of -OCH3 and -CN Substituents on Color Tuning of Ir(III) Complex Derivatives through a Joint Computational and Experimental Study

We performed a joint theoretical and experimental study on sixteen Ir(III) complexes bearing a similar molecular platform of bis(2-phenylbenzothiozolato-N,C^2' ) iridium(III) (acetylacetonate) by grafting -OCH₃ group and/or -CN group on different positions of the C-related arene moiety of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>C</mml:mi> <mml:mspace/> <mml:mover><mml:mspace/> <mml:mo>^</mml:mo></mml:mover> <mml:mspace/> <mml:mi>N</mml:mi></mml:mrow> </mml:math> ligand (C-ring). Our results reveal that the introduction of -CN renders an overall drop in the FMO energy levels while a reverse increase is observed for -OCH₃ . The ortho- and para-sites of the C-ring are more effective substitution positions to modulate the HOMO energy level due to the fact that the electronic density of HOMO mainly locates at them while the meta-site would induce a stronger impact on LUMO since the electronic density of LUMO mainly distributes over the position. Utilizing the synergistic effects of the substituents and the substituted positions, a wide color-tuning range from 479 nm to 637 nm was achieved, which covers nearly the whole window of visible spectrum. In particular, the tri-substituted Ir35mo4cn complex (λ_em max =637 nm) may be a potential candidate for high efficiency red OLEDs materials due to its greatly enhanced absorption processes, relatively higher ³ MLCT (%), lower ΔE_S1-T1 , enlarged separation between ³ MLCT/π-π* and ³ MC d-d states, and good hole and particle-transporting performances. Finally, six representative complexes were synthesized and their spectra were determined, which confirm the reliability of our computational strategy.

Acquiring High-Performance Deep-Blue OLED Emitters through an Unexpected Blueshift Color-Tuning Effect Induced by Electron-Donating -OMe Substituents

A series of blue-emissive 7-(diphenylamino)-4-phenoxycoumarin derivatives bearing -CF₃ , -OMe, or -N(Me)₂ substituents on the phenoxy subunit were synthesized. Although both the -CF₃ and -N(Me)₂ modifications were found to trigger redshifted fluorescence, the -OMe substitution was demonstrated to exert an unexpected blueshift color-tuning effect toward the deep-blue region. The reason is that the moderate electron-donating -OMe group can endow coumarins with unaltered HOMO but elevated LUMO energy levels. Moreover, the -OMe substitution was found to be beneficial to the thermal stability of these coumarins. Therefore, the trimethoxy-substituted objective compound can act as a high-performance deep-blue organic light-emitting diode (OLED) emitter, and OLED based on it emits deep-blue light with CIE coordinates of (0.148, 0.084), maximum luminance of 7800 cd m^-2 , and maximum external quantum efficiency of 5.1 %. These results not only shed light on the molecular design strategy for high-performance deep-blue OLED emitters through color-tuning, but also show the perspective of coumarin derivatives as deep-blue OLED emitters.

From Mononuclear to Dinuclear Iridium(III) Complex: Effective Tuning of the Optoelectronic Characteristics for Organic Light-Emitting Diodes

Phosphorescent dinuclear iridium(III) complexes that can show high luminescent efficiencies and good electroluminescent abilities are very rare. In this paper, highly phosphorescent 2-phenylpyrimidine-based dinuclear iridium(III) complexes have been synthesized and fully characterized. Significant differences of the photophysical and electrochemical properties between the mono- and dinuclear complexes are observed. The theoretical calculation results show that the dinuclear complexes adopt a unique molecular orbital spatial distribution pattern, which plays the key role of determining their photophysical and electrochemical properties. More importantly, the solution-processed organic light-emitting diode (OLED) based on the new dinuclear iridium(III) complex achieves a peak external quantum efficiency (η(ext)) of 14.4%, which is the highest η(ext) for OLEDs using dinuclear iridium(III) complexes as emitters. Besides, the efficiencies of the OLED based on the dinuclear iridium(III) complex are much higher that those of the OLED based on the corresponding mononuclear iridium(III) complex.

N,N-Diarylamino end-capping as a new strategy for simultaneously enhancing open-circuit voltage, short-circuit current density and fill factor in small molecule organic solar cells

N,N-Diarylamino end-capping strategy for asymmetrical squaraines with simultaneously enhanced V_oc, J_sc and FF in solution-processed small molecule organic solar cells.

The triplet excited state of Bodipy: formation, modulation and application

The accessing of the triplet excited state of one of the most popular fluorophores, boron-dipyrromethene (Bodipy), was summarized.

Highly phosphorescent iridium(iii) complexes based on 2-(biphenyl-4-yl)benzo[d]oxazole derivatives: synthesis, structures, properties and DFT calculations

A series of new 2-(biphenyl-4-yl)benzo[d]oxazole based bis-cyclometalated iridium(iii) complexes have been synthesized, and their high quantum efficiency are presented.

Upgrading malic acid to bio-based benzoates via a Diels–Alder-initiated sequence with the methyl coumalate platform

Malic acid dimerization was optimized to methyl coumalate from which a Diels–Alder strategy produced a variety of bio-based benzoates.

A low bandgap asymmetrical squaraine for high-performance solution-processed small molecule organic solar cells

A low-bandgap asymmetrical squaraine ASQ-5 bearing an indoline substituent for solution-processed organic solar cells with high J_sc and PCE was synthesized.