Spirobifluorene Derivatives Research Articles

Macromol. Rapid Commun. 18–19/2007

Cover: Highly contorted polyimides and polyamides based on spirobifluorene derivatives have been prepared. Depending on the overall chain rigidity, the polymers show intrinsic microporosity and enhanced solubility in solvents like chloroform or THF. Further details can be found in the article by J. Weber, Q. Su, M. Antonietti, and A. Thomas* on page 1871.

Extremely Low‐Threshold Amplified Spontaneous Emission of 9,9′‐Spirobifluorene Derivatives and Electroluminescence from Field‐Effect Transistor Structure

AbstractBy doping 2,7‐bis[4‐(N‐carbazole)phenylvinyl]‐9,9′‐spirobifluorene (spiro‐SBCz) into a wide energy gap 4,4′‐bis(9‐carbazole)‐2,2′‐biphenyl (CBP) host, we demonstrate an extremely low ASE threshold of Eth = (0.11 ± 0.05) μJ cm–2 (220 W cm–2) which is the lowest ASE threshold ever reported. In addition, we confirmed that the spiro‐SBCz thin film functions as an active light emitting layer in organic light‐emitting diode (OLED) and a field‐effect transistor (FET). In particular, we succeeded to obtain linear electroluminescence in the FET structure which will be useful for future organic laser diodes.

Photophysical Properties and Electropolymerization of Regioregular Head-to-Tail Oligothiophenes-Functionalized 9,9′-spirobifluorene Derivatives

The photophysical properties of oligothiophenes-functionalized 9,9′-spirobifluorene derivatives in solution and in solid state were investigated in detail. The enhanced red-shift was observed from the absorption and the photoluminescence (PL) spectra of these derivatives in dilute THF solution with the increase of thiophene unit at one branch of 9,9′-spirobifluorene identical with the increased p-electron delocalization and the more effective conjugation length of the whole molecular system. The investigation on the photophysical properties of these compounds further demonstrated that the sp3-hybrid carbon at the spiro-center completely obstructed the correlation between two branches of the 9,9′-spirobifluorene system and made every branch become an independent chromophore. The electrochemical polymerization of 6b as a representative was also investigated.

Synthesis and characterization of highly hindered and thermally stable poly(1,4‐spirobifluorenylenevinylene) derivative

AbstractA new poly(1,4‐spirobifluorenylenevinylene) having advantage PPV and spirobifluorene as new emissive family was synthesized. Compared with PPV derivatives that usually have a tolane bisbenzyl defect, the polymer has the defect free structure because of the steric hindrance of the asymmetric bulky spirobifluorenyl group. Compared with spirobifluorene derivatives that usually have a low solubility, the polymer has the good solubility in common organic solvents. The polymer was amorphous and showed high PL quantum efficiency and high thermal stability with high Tg. The PL emission peaks were shown at 480–490 nm in solution and film, respectively, which may represent the bluest emission peak reported for fully conjugated PPV derivatives. The study of thermal annealing of PL spectrum showed excimer formation inhibited. The thermal and optoelectronic properties of the polymer imply that it is a promising material for the PLED application. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 900–907, 2007.

Spirobifluorene derivatives for ultraviolet organic light-emitting diodes

Four new spirobifluorene (SBF) derivatives, 1,3,5-tris(9,9′-spirobifluoren-2-yl)benzene (TSBFB), 1,3-bis(9,9′-spirobifluoren-2-yl)benzene (BSBFB), 2-(1-naphthyl)-9,9′-spirobifluorene (1SBFN), and 2-(2-naphthyl)-9,9′-spirobifluorene (2SBFN), were prepared as ultraviolet (UV)-emitting materials for organic light-emitting diodes (OLEDs). These SBF derivatives all have high glass transition temperatures ( T g) above 95 °C, affording high-quality amorphous films with good morphological stability, and exhibit strong UV photoluminescence (PL) in solid state, showing no formation of excimers. In multilayer OLEDs using these SBF compounds as the emissive layers, the desired UV electroluminescence was achieved with high external quantum efficiencies of up to 2.9%. These results demonstrate that these compounds are promising UV-emitting materials for OLEDs.

NOVEL SYNTHESIS OF HIGHLY PHENYL-SUBSTITUTED SPIROBIFLUORENE AND CARBAZOLE DERIVATIVES THROUGH DIELS–ALDER REACTION FOR LIGHT-EMITTING DIODES

We synthesized and characterized novel highly phenyl-substituted spirobifluorene and carbazole derivatives such as 3,6-bis[(2,3,4,5-tetraphenyl)phenyl]-9-ethylcarbazole (BTPEC); 3,6-bis(7,10-diphenyl-fluoranthene)-9-ethylcarbazole (BDFEC); 2,7-Bis[(2,3,4,5-tetraphenyl)phenyl]-9,9′-spirobifluorene (BTPSF); and 3,6-bis(7,10-diphenyl-fluo-ran-thene)-9,9′-spirobifluorene (BDFSF), through Diels–Alder reaction. BDFEC showed sky blue PL spectrum at 481 nm and BTPSF showed ultra-violet PL spectrum at 374 nm in chloroform solution. Also BTPEC and BDFSF exhibited PL spectrum at around the UV region, 390 and 467 nm.

Electrode Surface Modification by a Spirobifluorene Derivative. An XPS and Electrochemical Investigation

Ordered thin layers of a spirobifluorene derivative containing an amino group were formed by grafting them onto a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) on gold. Either physical (H-bonding) or chemical bonding (activated by EDCl) was investigated. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy confirmed that both methods can be used to effectively graft 2-amino-9,9'-spirobifluorene molecules onto the SAM surface, giving high surface coverages, with a significantly higher packing in the case of chemisorbed films. EIS measurements also showed that the covalently bonded spirobifluorene SAMs act as an effective barrier to both ion penetration and heterogeneous electron transfer.

Synthesis and characterization of stable blue light‐emitting poly(spirobifluorene) derivatives containing alkoxy group

AbstractPolymers containing alkoxy‐substituted spirobifluorene have been prepared from nickel(0)‐mediated coupling or palladium‐catalyzed Suzuki coupling. The polymers were characterized using various spectroscopies, such as 1H‐NMR, FT‐IR, and elemental analysis. The high glass transition temperature and high decomposition temperature suggested that the resulting polymers possessed a high thermal stability. The obtained polymers possessed weight average molecular weight of 4500–33,000 with polydispersity index of 1.1–1.9 and good solubility. The low onsets of the oxidation potential suggested that the polymers containing alkoxy substituted spirobifluorene possessed a good hole injection property. The photoluminescence and electroluminescence of the polymers containing alkoxy substituted spirobifluorene showed stable blue color by suppressing the excimer formation due to intermolecular interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2316–2324, 2005

High Tg blue emitting materials for electroluminescent devices

A series of 2′,7′-di-tert-butyl-9,9′-spirobifluorene derivatives (flu) incorporating arylamines at the 2- and/or 7-positions were synthesized. These compounds possess a high glass transition temperature ranging from 135 to 215 °C. Incorporation of spirobifluorene was found to be beneficial for raising the glass transition temperature (Tg) of the molecules. Most of the compounds are blue emitting with good solution quantum yields. Blue-emitting double-layer devices with narrow full width at half-maximum (fwhm < 68 nm) were constructed using these materials as the hole-transporting and emitting layer, and TPBI (1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene) as the electron-transporting layer (device I). In double-layer devices of the configuration ITO/flu (40 nm)/Alq3 (40 nm)/Mg : Ag (Alq3 = tris(8-hydroxyquinoline)aluminium) (device II), flu functioned mainly as a hole-transporting layer, and the green light characteristic of Alq3 was detected. Two of the devices of type I have very promising performance, and one of them emits pure blue light (CIE (x,y) = (0.15, 0.09)). One of the compounds was found to be an efficient hole-injection material.

Deep blue widely tunable organic solid-state laser based on a spirobifluorene derivative

We report on amplified spontaneous emission and optically pumped deep blue lasing in the organic spirobifluorene derivative 2,7-bis(biphenyl-4-yl)-2′,7′-di-tert-butyl-9,9′-spirobifluorene. Solid-state lasing is observed in thin films of this material deposited on a distributed-feedback (DFB) grating substrate. The laser wavelength can be tuned from 401.5 to 434.2 nm depending on the grating period of the Bragg reflector. The blue edge of this interval at 401.5 nm makes this laser an extremely short wavelength organic DFB laser. When pumping with a pulsed nitrogen laser at 337 nm, we observe a laser threshold energy density of 83 μJ/cm2. These results render this spiro compound an excellent candidate for blue-emitting diode lasers.

Organic blue light emitting materials based on spirobifluorene

Abstract Spirobifluorene derivative, which is useful for obtaining small molecule or polymer blue light emitting materials, has been prepared. To improve the solubility of final materials, long alkoxy side chains were introduced to spirobifluorene moiety. Coupling reaction with biphenyl led to small molecule blue light emitting material. A polymer blue light emitting material was obtained through Ni(0) mediated polymerization. Using vacuum deposition and spin coating methods, small molecule and polymer light emitting devices were fabricated and their device characteristics were investigated. In this paper, the detailed preparation methods of small molecule and polymer materials, and the device characteristics will be discussed.

Synthesis of regio- and stereoselective alkoxy-substituted spirobifluorene derivatives for blue light emitting materials

Three new octyloxy substituted spirobifluorenes, 2,7-diphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DPBSBF, 1a ), 2,7-dibiphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DBBSBF, 1b ) and 2,7-diterphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DTBSBF, 1c ) were prepared. All the compounds had been fully characterized by 1H and 13C NMR, UV–Vis, DSC, mass spectrometry and gave satisfactory elemental analyses. They possessed good solubility in common organic solvents and good homogeneous film formation. The optical energy band gap of DBBSBF was 3.27 eV between the HOMO energy level, 5.85 eV, measured by UPS and the LUMO, 2.58 eV, calculated from absorption spectrum. A blue organic light emitting diode (OLED) based on the structure of ITO/TPD (60 nm)/DBBSBF (40 nm)/Alq 3 (20 nm)/LiF (1 nm)/Al (100 nm) showed good performance. The luminance of 3125 cd/m 2 was observed at a drive voltage of 12.8 V and the colour coordinate in CIE chromaticity was (0.14, 0.12). The external quantum efficiency was obtained to be 2.8% at 100 cd/m 2.

Regioregular head-to-tail oligothiophene-functionalized 9,9'-spirobifluorene derivatives. 2. NMR characterization, thermal behaviors, and electrochemical properties.

Oligothiophene-functionalized 9,9'-spirobifluorene derivatives exhibit good solubility in polar organic solvents, especially compounds 5a-d to 7a-d due to the introduction of the flexible n-hexyl chain. The structures of all compounds studied are characterized and verified by (1)H and (13)C NMR spectra. The results not only show that these organic conjugated materials with no substituents or n-hexyl substituents are successfully synthesized through the corresponding synthetic methodologies, but also prove that chemical shifts of protons and carbons in the aromatic range change with the attachment and the increase of the thiophene ring at the 9,9'-spirobifluorene fragment. The thermal analysis results demonstrate that these compounds are quite stable, and evaporate from 300 to 700 degrees C. Most of these compounds exhibit a stable amorphous state in the solid state. The electrochemical properties of all compounds studied are also investigated. The results indicate that radical cation behaviors of oligothiophene-modified 9,9'-spirobifluorene derivatives are more stable than those of normal oligothiophenes, that oxidative and reductive peak potentials shift cathodically or anodically, and that the HOMO and LUMO energy levels are also tuned with the increase of the thiophene ring owing to the enhanced pi-electron delocalization and the increasing conjugation length. Oxidative potentials of nonsubstituted oligothiophene-functionalized 9,9'-spirobifluorene derivatives are more sensitive to the increase of thiophene rings than those of 9,9'-spirobifluorene derivatives with n-hexyl groups. The energy levels and band gaps of all compounds studied are also calculated from the onset potentials of n-doping and p-doping and are adjusted by varying thiophene oligomers and their attachment patterns to the 9,9'-spirobifluorene ring to make them suitable for the work functions of the electrodes.

Head-to-tail regioregular oligothiophene-functionalized 9,9'-spirobifluorene derivatives. 1. Synthesis.

Two series of novel fully conjugated oligomers, oligothiophene-functionalized 9,9'-spirobifluorene derivatives, have been developed in this contribution. First, four 9,9'-spirobifluorene bromide derivatives (compounds 1a-d) are prepared through various synthetic routes. Oligothiophene derivatives with or without substituents are synthesized through the Grignard and Suzuki coupling reactions. The Negishi coupling reactions between oligothienylzinc chloride and various 9,9'-spirobifluorene bromides with Pd(PPh(3))(4) as catalyst successfully produce the desired compounds, unsubstituted oligothiophene-functionalized 9,9'-spirobifluorene derivatives, compounds 2 to 4a-d. Since the Negishi coupling reactions afford regioregularly head-to-tail (H-T) oligo(4-n-hexylthiophene)-functionalized 9,9'-spirobifluorene derivatives in poor yields, the Suzuki coupling reactions between sodium 4-n-hexylthienyl-2-boronate 8, and various 9,9'-spirobifluorene-based bromides 1a-d and 9-16 are employed to produce highly regioregular head-to-tail oligothiophene-functionalized 9,9'-spirobifluorene derivatives (compounds 5 to 7a-d) in very high yields. We also investigate the effect of solvents on the Suzuki coupling reactions. The structure and purity of all compounds are verified by FT-IR, (1)H and (13)C NMR, MS, and elemental analysis.

Synthesis, circular dichroism and absolute stereochemistry of chiral spiroaromatic compounds. 9,9′-Spirobifluorene derivatives

The chiral spiroaromatic compounds (+)-2 and (+)-3 with 9,9′-spirobifluorene skeletons have been synthesized and their absolute stereostructures have been unambiguously determined to be R, by application of the CD exciton chirality method; the R absolute stereochemistry of (–)-[6,6]-vespirene 1 was established by chemical correlation with these compounds.

Chiroptische Eigenschaften und absolute Konfiguration von 9, 9′‐Spirobifluoren‐Derivaten

AbstractThe circular dichroism and optical rotatory dispersion of three vespirenes, three vespirones, and of some related 9, 9′‐spirobifluorene derivatives [4] have been measured. The absolute configurations of these compounds have been determined from chiroptical properties (CU., ORD.) in four ways which give mutually consistent results. For the (−)‐vespirenes the (R)‐configuration (Figs. 1 and 2) follows from 1 is treatment.

Optisch aktive 9,9′‐Spirobifluoren‐Derivate

AbstractThe optically active compounds XXIII, XXIV, and XXV, named vespirenes, have been synthetized as first examples of compounds containing a single chirality centre of the type X(A4). The analogous optically active 9,9′‐spirobifluorene derivatives XXI, XXVI, and XXVIII have been prepared for comparison of their chiroptic properties with those of vespirenes.