Full‐Color Fluorescence Solvatochromism of Push‐Pull Type Indenoindene Derivatives

Full‐color fluorescence solvatochromism was demonstrated using two carbon‐bridged oligo(phenylenevinylene) (COPV) derivatives Ph₂N‐COPV1(Bu)‐COCH₃ and [Ph₂N‐COPV1(Bu)]₂CO with a push–pull system, where the donor and acceptor moieties are diphenylamino and a carbonyl group, respectively. In non‐polar cyclohexane, the molecules exhibited blue photoluminescence (λ_PL=443 and 464 nm) with a locally excited character, while in polar solvents, a charge‐transfer character emerged. In methanol, red emission was observed (λ_PL=602 and 572 nm). The difference in luminescence maxima between cyclohexane and methanol corresponds to 0.74 and 0.59 eV for Ph₂N‐COPV1(Bu)‐COCH₃ and [Ph₂N‐COPV1(Bu)]₂CO, respectively, which are larger than those of previously reported push–pull systems. The photoluminescence quantum yields of Ph₂N‐COPV1(Bu)‐COCH₃ in aprotic solvents were 0.90 and higher regardless of solvent polarity, while they decreased in protic solvents. The molecules also display high extinction coefficients of up to 2.8x10⁴ and 6.4x10⁴ M⁻¹ cm⁻¹. These data demonstrate the effectiveness of the use of structurally rigid planar COPV framework. Furthermore, [Ph₂N‐COPV1(Bu)]₂CO showed significant responses to water content in tetrahydrofuran‐water mixed solvents, which highlights its potential for sensing applications.