TD-DFT Study on Thiacalix[4]arene, the Receptor of a Fluorescent Chemosensor for Cu²⁺

Abstract

The electronic and spectral properties of p-tert-butylthiacalix[4]arene (TCA) and its Cu complexes (CuTCA and CuTCA) were characterized by time-dependent density functional theory (TD-DFT). Geometries of TCA, CuTCA, and CuTCA were optimized at the CAM-B3LYP/6-31+G(d,p) level of theory in water using the conductor-like polarizable continuum model. The absorption spectra of TCA, CuTCA, and CuTCA were demonstrated by TD-DFT method. The quenching mechanism of perylene as the fluorophore of a chemosensor based on thiacalix[4]arene was discussed. The addition of Cu to TCA introduced a series of low-lying excited states involving copper d orbitals. The overlap between absorption of TCA complexes and emission of perylene indicated that the quenching of perylene fluorescence is due to fluorescence resonance energy transfer.

Six Fluorene-Based N-Heterocyclic Carbene Silver(I) Complexes: Structural Study and Recognition for Cu2+

“…Therefore, the detection of Cu 2+ plays an important role in life science and environmental science. The fluorescence recognition of Cu 2+ is a useful method because of its high sensitivity and simplicity of the equipment. − Up to now, some fluorescence chemosensors for Cu 2+ have been reported, − but developing more effective chemosensors remains a desirable job for researchers. Herein, we reported the preparation and structure of six fluorene-bridged bisazolium (azolium = benzimidazolium or imidazolium) salts L 1 H 2 ·X 2 -L 6 H 2 ·X 2 (X = Br – or PF 6 – ) and six related NHC silver­(I) complexes [(L 1 Ag) 2 ]­(NO 3 ) 2 ( 1 ), {[L 2 Ag 2 (CH 3 CN) 2 ] 2 }­(PF 6 ) 4 ( 2 ), [(L 3 Ag) 2 (Ag 2 Br 4 )] n ( 3 ), [(L 4 Ag)­(NO 3 )] n ( 4 ), [L 5 Ag 2 Br 2 ] n ( 5 ), and [L 6 (AgCl) 2 ] ( 6 ).…”