A fluorescent calix[4]arene with naphthalene units at the upper rim exhibits long fluorescence emission lifetime without fluorescence quenching.

Masaki Takahashi,Kohei Yazaki,Yoshihisa Sei,Makoto Obata,Naoya Tsuji

doi:10.1039/d1ra01743h

Abstract

We synthesised a new compound with four naphthyl groups in the upper rims of calix[4]arene (1). Compared to the monomer unit, compound 1 has redshifted absorption and fluorescence, together with high fluorescence quantum yield and long fluorescence lifetime, which is extremely rare because long fluorescence lifetime emission tends to reduce the quantum yield. Single-crystal X-ray analysis and quantum calculations in the S1 state revealed π–π through-space interactions between naphthalene rings.

Highlights

We synthesised a new compound with four naphthyl groups in the upper rims of calix[4]arene (1)
It was reported that bright and long-lived uorescence can be obtained from the excimer state[13,16,17,18,19] that was conventionally thought to be the cause of quenching due to the low-energy excimer trap states with forbidden radiative transition and activated non-radiative process.[20,21,22,23,24]. Most of these reports were in the solid state, where the molecular movement is suppressed and the luminescence occurs in a single crystal.[16,17,18,19]
Molecular orbital calculation con rmed that the p orbitals of the naphthalene rings of tetranaphthylcalixarene have a binding interactions in LUMO of the S1 state

Summary

Introduction

We synthesised a new compound with four naphthyl groups in the upper rims of calix[4]arene (1). The new molecule showed both a long uorescence wavelength and a high quantum yield. A er measuring the conformation of tetranaphthylcalix[4]arene in a single crystal, structural optimisation of the ground state and excited state (S1) was performed by time-dependent density functional theory (TD-DFT) at the DFT-D3-CAM-B3LYP/6-31G(d) level.

Results

Conclusion