1056477-95-2Relevant academic research and scientific papers
Mesitylboron-substituted ladder-type pentaphenylenes: Charge-transfer, electronic communication, and sensing properties
Zhou, Gang,Baumgarten, Martin,Muellen, Klaus
experimental part, p. 12477 - 12484 (2009/02/05)
A series of dimesitylboron (B)- or ditolylamino (N)-substituted ladder-type pentaphenylenes (PP) has been designed and synthesized. The UV-vis absorption spectra of compounds BPPN, BPPB, and NPPN reveal an identical maximum wavelength at 432 nm, which indicates that the B and N centers have very similar contributions to the extended conjugation. A rather weak solvatochromism in the UV-vis absorption spectra is observed for compound BPPN, while a remarkable solvatochromic emission is achieved even though the distance between the B and the N centers is as huge as 22 A. The photoluminescence of BPPN shows a bathochromic shift of 108 nm when the solvent polarity is increased from cyclohexane (453 nm) to acetone (561 nm). Compound BPPN acts as a colorimetric and fluorescent chemosensor with high sensitivity (10-5 M) and selectivity for F- over other halogen ions. By inhibiting the charge transfer (CT) from the N center to the B center, the intense green CT emission of compound BPPN rapidly switches into the sky-blue emission of PP when F - is bound to the B center. Furthermore, a CT emission can be switched on and off when compound BPPB is used as F - sensory material. Such an intramolecular CT emission between the two B centers has so far never been reported. Corresponding studies by cyclic voltammetry and differential pulse voltammetry reveal a two-step reduction of the two bridged B centers in compound BPPB, which might suggest that the charge delocalizes through the whole molecule and that the terminal redox centers communicate through the pentaphenylene bridge.
