Large Fluorescence Response by Alcohol from a Bis(benzoxazole)–Zinc(II) Complex: The Role of Excited State Intramolecular Proton Transfer

• Published in: The journal of physical chemistry. B 2013-04, Vol.117 (15), p.4127-4133
• Main Authors: Wang, Junfeng, Chu, Qinghui, Liu, Xiumin, Wesdemiotis, Chrys, Pang, Yi
• Format: Article
• Language: English
• Subjects: Alcohols - chemistry; Anions; Atomic and molecular physics; Benzoxazoles - chemistry; Cations; Coordination Complexes - chemistry; Drug Stability; Emission spectroscopy; Exact sciences and technology; Excitation; Fluorescence; Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion); Methyl alcohol; Molecular properties and interactions with photons; Molecular Structure; Physics; Protons; Spectrometry, Fluorescence; Spectrometry, Mass, Electrospray Ionization; Stability; Zinc; Zinc - chemistry
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp401612u

The formation of a bis(HBO) anion is known to turn on the fluorescence to give red emission, via controlling the excited-state intramolecular proton transfer (ESIPT). The poor stability of the formed anion, however, hampered its application. The anion stability is found to be greatly improved by attaching the anion to Zn2+ cation (i.e., forming zinc complex), whose emission is at λem ≈ 550 and 760 nm. Interestingly, addition of methanol to the zinc complex induces a remarkable red fluorescence (λem ≈ 630 nm, ϕfl ≈ 0.8). With the aid of spectroscopic studies (1H NMR, UV–vis, fluorescence, and mass spectra), the structures of the zinc complexes are characterized. The emission species is identified as a dimer-like structure. The study thus reveals an effective fluorescence switching mechanism that could further advance the application of ESIPT-based sensors.