Axially Chiral Spiro-Conjugated Carbon-Bridged p-Phenylenevinylene Congeners: Synthetic Design and Materials Properties

Abstract

Spiro-conjugated systems are attracting considerable interest for their chiroptical properties and because of their compact structure the small reorganization energy upon electronic excitation or ionization. We report here a modular and convergent synthesis of axially chiral spiro-conjugated carbon-bridged p-phenylenevinylenes (spiro-CPVs) in a racemic and optically active form where two carbon-bridged p-phenylenevinylene molecules are connected by a spiro carbon atom. Our synthetic design focuses on the C 2 symmetry of the spiro-CPV molecules, relying on coupling of two 3-lithio-2-arylindene molecules on a carbon monooxide molecule that serves as the spiro carbon center in the target molecule. We prepared derivatives including those possessing phenol groups that facilitate optical resolution and also serve as a platform for the synthesis of a variety of optically active derivatives, which exhibit circularly polarized photoluminescence with high fluorescence quantum yields, large dissymmetry factors, and high photostability. For example, a bis­(phenylethynyl) derivative exhibited a fluorescence quantum yield of 0.99 and a dissymmetry factor in luminescence of |g lum| = 2.7 × 10–4, values highest among and comparable to those of reported CPL compounds, respectively. A tetrakis-diarylamine derivative shows hole mobility (μh = 3.84 × 10–5 cm2 V–1 s–1; space charge-limited current measurement of a spin-coated film) comparable to that of a popularly used hole-transporting material, spiro-OMeTAD (μh = 2.6 × 10–5 cm2 V–1 s–1), as well as high thermal and phase stability (T 5d = 382 °C, T g = 171 °C).

Rigidly Fused Spiro‐Conjugated π‐Systems

“…The UV-vis absorption spectrum of compound 31 is highly comparable to compound 1, as reported by Poriel and Rault-Berthelot et al [14] However, compound 31 possessed reduced structural rigidity and a larger Stokes shift (15 nm), compared with compound 1 and its equivalents 16-20. Recently, Nakamura et al reported the axially chiral spiro-conjugated carbon-bridged p-phenylenevinylene compound 32, [35] (Scheme 12) which exhibited a PLQY of 74 % and a decomposition temperature of 335°C (with 5 % weight loss). More importantly, a series of compound 32 derivatives with four diarylamine units were efficiently obtained with a higher than 60 % yield, which presented a low hole mobility of 3.84 × 10 À 5 cm 2 V À 1 s À 1 ; highly comparable with the most widely used hole-transporting material: 2,2',7,7'-tetrakis (N,N-bis(p-methoxy-phenyl)amino)-9,9'-spirobifluorene (spiro-OMeTAD).…”

“…More importantly, a series of compound 32 derivatives with four diarylamine units were efficiently obtained with a higher than 60 % yield, which presented a low hole mobility of 3.84 × 10 À 5 cm 2 V À 1 s À 1 ; highly comparable with the most widely used hole-transporting material: 2,2',7,7'-tetrakis (N,N-bis(p-methoxy-phenyl)amino)-9,9'-spirobifluorene (spiro-OMeTAD). [35] Trispirocyclic hydrocarbon compound 33 (Scheme 13), possessing three 9-fluorene moieties around the core of truxene, was synthesized via truxenone with 2-bromobiphenyl coupling. [36] Compound 33 is a colorless solid, sparingly soluble in common organic solvents, and has a melting point of 500°C.…”

Enantioselective Synthesis of Functionalized Diazaspirocycles from 4‐Benzylideneisoxazol‐5(4H)‐one Derivatives and Isocyanoacetate Esters

“…[1f] Spirocyclic compounds have also found some interesting applications as privileged ligands for asymmetric catalysis such as spinol, [2] or in the production of circularly polarized photoluminescence. [3] Furthermore, the spirocyclic motif is becoming a prevalent template in drug discovery, [4] since this structural feature conveys both increased three-dimensionality for potential improved activity, and novelty for patenting purposes. An example of spirocyclic drugs is the marketed fenspiride, [5] used for the treatment of some respiratory diseases (Figure 1).…”

Rhodium(III)‐Catalyzed Asymmetric Access to Spirocycles through C−H Activation and Axial‐to‐Central Chirality Transfer

“…Thus, simple 2D aromatics can be elaborated to 3D structures in precise platforms. Spirocycles are an important class of 3D framework and have found widespread applications in material sciences owing to their outstanding photophysical and optical properties, especially for naphthol‐derived spirocycles . C−H activation has enabled the facile construction of diverse spirocycles .…”

“…Spirocycles are an important class of 3D framework and have found widespread applications in material sciences owing to their outstanding photophysical and optical properties, especially for naphthol‐derived spirocycles . C−H activation has enabled the facile construction of diverse spirocycles . In particular, CpRh III complexes stand out as prominent catalysts in spiroannulations of arenes with unsaturated coupling reagents such as alkynes, alkenes, and diazo reagents .…”