Fluorescence Control of Boron Enaminoketonate Using a Rotaxane Shuttle

Abstract

The effect of rotaxane shuttling on the fluorescence properties of a fluorophore was investigated by exploiting fluorophore-tethered [2]rotaxanes. A fluorescent boron enaminoketonate (BEK) moiety was introduced in a rotaxane via transformation of an isoxazole unit generated as a result of an end-capping reaction using a nitrile N-oxide. The rotaxane exhibited a red shift of the fluorescence maximum along with a remarkable enhancement of the fluorescence quantum yield through wheel translation to the fluorophore.

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

“…Boron ketoiminates (BKIs, 6) are one of the new types of boron-chelating dye [34][35][36][37][38], their optical properties feature a large Stokes shift and high molar absorption coefficients (ε) that are similar to the corresponding boron diketonates. The synthesis and properties of BKIs have been reported recently and they are easily accessible either from the corresponding 1,3-di-ketones 1 or from isoxazoles 2 through a ring-opening reaction (Scheme 3).…”

Fluorescent poly(boron enaminoketonate)s: synthesis via the direct modification of polyisoxazoles obtained from the click polymerization of a homoditopic nitrile N-oxide and diynes

“…One regioisomer was preferentially formed as confirmed by the 1 H NMR spectra. 16,17,37 Table 2 summarizes the thermal properties of the resulting polymers. All polyisoxazoles and PBEKs, except for poly-3, are crystalline polymers, as suggested by the observed melting temperatures.…”

“…All polyisoxazoles and PBEKs, except for poly-3, are crystalline polymers, as suggested by the observed melting temperatures. 16 The crystallinity can be attributed to the interaction between the aromatic groups in the polymer main chain. The thermal decomposition temperatures were sufficiently high, thereby indicating the stability of the resulting polymers.…”

“…applications not only to polymeric materials but also supramolecular chemistry because we have previously reported effective synthesis of rotaxane and polyrotaxane exploiting a cycloaddition of stable nitrile N-oxide. 16,27,30,33,36 The study of stimuli-responsive fluorescent switching system using BEK-containing supramolecular skeleton will be important for future. …”

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

“…UV/Vis and FL spectra of compounds 3b and 3c.Synthesis of boron ketoiminates and α-fluorinated boron ketoiminatesBoron ketoiminates (BKIs, 6) are one of the new types of boron-chelating dye [34][35][36][37][38]. Their optical properties feature a large Stokes shift and high-molar absorption coefficient (ε) that are quite similar to the corresponding boron diketonates.…”