Synthesis and properties of 9,9-diarylfluorene-based triaryldiamines

Exciplex-forming cohost systems with 2,7-dicyanofluorene acceptors for high efficiency red and deep-red OLEDs

Two 2,7-dicyaonfluorene-based molecules 27-DCN and 27-tDCN are utilized as acceptors (A) to combine with hexaphenylbenzene-centered donors (D) TATT and DDT-HPB for probing the exciplex formation. The photophysical characteristics reveal that the steric hindered 27-tDCN not only can increase the distance of D and A, resulting in a hypsochromic emission, but also dilute the concentration of triplet excitons to suppress non-radiative process. The 27-tDCN-based exciplex-forming blends exhibit better photoluminescence quantum yield (PLQY) as compared to those of 27-DCN-based pairs. In consequence, among these D:A blends, the device employing DDT-HPB:27-tDCN blend as the emissiom layer (EML) exhibits the best EQE of 3.0% with electroluminescence (EL) λmax of 542 nm. To further utilize the exciton electrically generated in exciplex-forming system, two D-A-D-configurated fluorescence emitter DTPNT and DTPNBT are doped into the DDT-HPB:27-tDCN blend. The nice spectral overlap ensures fast and efficient Förster energy transfer (FRET) process between the exciplex-forming host and the fluorescent quests. The red device adopting DDT-HPB:27-tDCN:10 wt% DTPNT as the EML gives EL λmax of 660 nm and maximum external quantum efficiency (EQEmax) of 5.8%, while EL λmax of 685 nm and EQE of 5.0% for the EML of DDT-HPB:27-tDCN:10 wt% DTPNBT. This work manifests a potential strategy to achieve high efficiency red and deep red OLED devices by incorporating the highly fluorescent emitters to extract the excitons generated by the exciplex-forming blend with bulky acceptor for suppressing non-radiative process.

A cascade double 1,4-addition/intramolecular annulation strategy for expeditious assembly of unsymmetrical dibenzofurans

Existing synthetic routes for accessing dibenzofuran core have intrinsic regioselectivity, limiting the substitution patterns available in heteropolycyclic arene products. Here we report a double 1,4-conjugate addition/intramolecular annulation cascade reaction between propargylamines and two equivalents of imidazolium methylides that allows efficient access of structurally versatile dibenzofurans. This transition metal-free protocol proceeds smoothly under bench-top air atmosphere and offers easy manipulation of substituents on the dibenzofuran core, and also provides good-to-excellent product yields with good functional group tolerance, particularly the -Br and -Cl groups which are often incompatible with existing metal-catalyzed C-C and/or C-O bond ring-forming processes. It is worth noting that ladder-type π-systems with all-arene quarternary carbon structure can be straightforwardly generated upon simple late-stage functionalization.

Synthesis of blue emissive functionalized 9,9-disubstituted fluorene derivatives via BF3·OEt2 mediated reaction of co-planar 9-(phenylethynyl)-9H-fluoren-9-ols with isatin imines

A BF₃·Et₂O mediated reaction of co-planar 9-(phenylethynyl)-9H-fluoren-9-ol with various isatin imines afforded title compounds in excellent yield. The products showed luminescence in the blue region with large Stokes shift.

A Sc(OTf)3 catalyzed dehydrogenative reaction of electron-rich (hetero)aryl nucleophiles with 9-aryl-fluoren-9-ols

New pyrenyl substituted 9,9-diarylfluorene with nonplanar conformations, high fluorescence quantum yield and excellent thermal and morphological stability was synthesized by our current protocol.

Natural diarylfluorene derivatives: isolation, total synthesis, and phosphodiesterase-4 inhibition

The first total synthesis of selaginpulvilins A–F and evaluation of their PDE4 inhibitory activities.

Bigger and Brighter Fluorenes: Facile π-Expansion, Brilliant Emission and Sensing of Nitroaromatics

π-Expanded butterfly-like 2D fluorenes and 3D spirobifluorenes 1-5 were synthesized via a DDQ-mediated oxidative cyclization strategy with a high regioselectivity. Through structural modification via π-expansion, it was possible to achieve near-ultraviolet absorption, bright-blue emission, very high near-unity fluorescence quantum yields in solution as well as in film states, and deep-lying HOMO energy levels with excellent thermal stabilities. Furthermore, these electron-rich compounds displayed a notable behavior towards sensing of nitroaromatic explosives, such as picric acid, up to a detection limit of 0.2 ppb.

Extension of light-harvesting area of bulk-heterojunction solar cells by cosensitization with ring-expanded metallophthalocyanines fused with fluorene skeletons

Near-IR absorbing zinc fluorenocyanine complexes 1-3 were designed and synthesized as a cosensitizer for bulk-heterojunction solar cells. Fusing fluorene rings with the porphyrazine rings resulted in narrower band gap and stabilization of both the HOMO and LUMO energy levels compared with a zinc phthalocyanine complex. The synthesized fluorenocyanines 1-3 were incorporated into bulk-heterojunction solar cells based on regioregular poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61. The addition of 3 decorated with eight alkyl chains resulted in improved device performance with a 16% enhancement of the short circuit current compared with that of the reference cell without 3.

The role of triphenylamine in the stabilization of highly efficient polyfluorene-based OLEDs: a model oligomers study

In order to understand the factors responsible for the improved efficiency and stability of organic light-emitting diodes (OLEDs) based on poly(9,9-dioctylfluorene) (PFO) when triphenylamine (TPA) is introduced as lateral fluorene substituent, we synthetize mono-disperse fluorene-thiophene oligomers as model compounds. Their blends with different concentrations of the fluorenone containing oligomer are studied in order to verify if only a reduction of ketonic defect sites or also an impeded energy transfer (ET) towards such sites are responsible for the suppression of the green emission band. We show that the introduction of TPA groups leads specifically both to an antioxidant action and a reduced ET towards residual defect sites, thanks to the environmental micro-encapsulation role played by TPA units surrounding the polymer backbone. As a result, the performances and colour stability of a device fabricated with TPA-substituted PFO (PFTPA) are strongly improved with respect to standard PFO device prepared in the same conditions.

End-Capped Terfluorene Derivatives: Synthesis and Structure - Functional Property Relationships

A series of monodisperse symmetric terfluorenes end-capped with diphenylamino groups or dendrons based on triarylamine and carbazole moieties, OF(3)R´–R, R´ = Bu or Ph, R = H, NPh, or EG, have been synthesized by a convergent approach using palladium-catalyzed Suzuki cross-coupling or copper-catalyzed Buchwald’s amination as the key reaction. The functional properties, which include thermal stabilities, linear and non-linear optical properties, and fluorescence and electrochemical properties of the terfluorene derivatives are also investigated and discussed. The preliminary results show that end-capping of the terfluorene with diphenylamino groups, especially with dendrons, has been shown to offer advantages in terms of lowering the first ionization potential, enhancing thermal stability, and inducing good amorphous morphological stability of the resulting compounds.

Novel Carbazole/Fluorene Hybrids: Host Materials for Blue Phosphorescent OLEDs

[reaction: see text] A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and FIrpic as the guest.

Synthesis and Functional Properties of End-Dendronized Oligo(9,9-diphenyl)fluorenes

[structure: see text] A facile approach for the synthesis of a family of dendrimers OFn-EG with hole-transporting ability moieties by copper-catalyzed Buchwald's double-amination as a key reaction has been developed. These novel dendrimers exhibit good energy transfer efficiencies and very high thermal and electrochemical stabilities and have potential applications as hole transfer and emitting layers in the field of organic emitting diodes (OLEDs) or as host materials for electrophosphorescent applications.

Prediction of glass transition temperatures of OLED materials using topological indices

The QSPR study was performed between topological indices and glass transition temperatures (T(g)s) of organic light-emitting diode materials based on a diverse set of 80 compounds. A five-parameter correlation with the squared correlation coefficient R2 = 0.9304 and an average absolute error of 7.7 K was obtained through step-wise multi-linear regression analysis with leave-one-out cross-validation. The new model proposed is predictive and requires only topological indices in the calculations and has the advantage of the relative ease in calculating the descriptors, which makes it easier to apply. The predicted results of the new model are comparable to those of the existing equation by using the Comprehensives Descriptors for Structural and Statistical Analysis approach.

Doubly ortho-linked quinoxaline/triarylamine hybrid as a bifunctional, dipolar electroluminescent template for optoelectronic applications

The titled hybrid (Q-H) works as a clippable optoelectronic unit. Q-spacer-Q systems function as efficient orange emitters reaching EL intensities (L) of up to 6840 cd m-2 with etaext of 0.77% and operation efficiencies of 1.60 cd A-1 and 0.8 lm W-1. Notably, Q-An acts as a (bluish) green emitter, reaching L of 12347 cd m-2 with similar operational efficiency.

Synthesis of Alkylated Aminofluorenes by Palladium-Catalyzed Substitution at Halofluorenes

New N-substituted 2-amino-9,9-dialkylfluorenes optionally bearing electron-withdrawing substituents such as nitro or cyano in position 7 can be synthesized starting from 2-halo-9,9-dialkylfluorenes by Pd-catalyzed substitution with amines. Chiral amino groups can be introduced by this method too. 2-N,N-Dimethylamino-7-nitro-9H-fluorene was obtained in a convenient way by reductive amination. The N-substituted 2-amino-7-nitro-9H-fluorenes are promising candidates for fluorescence probes for femtosecond solvation dynamics.

Ter(9,9-diarylfluorene)s: Highly Efficient Blue Emitter with Promising Electrochemical and Thermal Stability

Novel ter(9,9-diarylfluorene)s were synthesized by a Suzuki-coupling reaction of 2-bromofluorene (1) and 2,7-fluorenediboronic ester derivatives (3) with high isolated yields (63-86%). The X-ray structure analysis of ter(9,9'-spirobifluorene) (4aa) revealed that the conjugated chromophore adopts a helical conformation. This conformation effectively releases the steric interaction between the fluorene moieties and prevents inter-chromophore interactions. The introduction of aryl groups at the C9 position of fluorene was highly beneficial to the thermal and morphological stability of these oligomers. These terfluorenes exhibit intense blue fluorescence with excellent quantum yields both in solution ( approximately 100%) and in solid state (66-90%), and possess interesting reversible redox properties. Highly efficient blue light-emitting OLED devices were fabricated using 4aa and 4cc as emitters as well as hole transporters. The devices exhibit low turn-on voltage ( approximately 3 V) and high EL external quantum efficiency (2.5-3%).