Solvatochromic fluorescent ethynyl naphthalimide derivatives for detection of water in organic solvents

• Published in: Dyes and pigments Vol. 227; p. 112188
• Main Authors: Nhu, Quynh Pham Nguyen, Abbas Abedi, Syed Ali, Chanmungkalakul, Supphachok, Sukwattanasinitt, Mongkol, Chang, Young-Tae, Rashatasakhon, Paitoon
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2024
• Subjects: Fluorescence; Naphthalimide; Organic solvents; Sensor; Solvatochromism; Water; Water; Fluorescence; Solvatochromism; Naphthalimide; Organic solvents; Sensor
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2024.112188

Three new derivatives of (4-methoxyphenyl) ethynyl-naphthalimide were synthesized by Sonogashira coupling reaction. These compounds showed robust and strong fluorescent signals, which shift from blue to orange as the solvent polarity increases. Computational calculations revealed that in low-polarity solvents, the molecules preferred a 90° rotation between the naphthalimide and ethynyl benzene fragments. In high-polarity solvents, where the energy barrier for rotation of the alkyne bond was higher, the molecules favored the 0° conformer, leading to longer emission wavelengths. The compound with a 2-methoxyethyl group tethered to the naphthalimide nitrogen demonstrated sensitivity to water presence in the ranges of 0–30 % (v/v) in THF, 0–15 % (v/v) in DMSO, 0–30 % (v/v) in MeCN, 0–15 % (v/v) in acetone, and 0–40 % (v/v) in EtOH. The detection limits for water were determined to be 0.0523 %, 0.1365 %, 0.0337 %, 0.0570 %, and 0.1170 % (v/v) in THF, DMSO, MeCN, acetone, and EtOH, respectively. The effectiveness of this compound in quantifying ethanol content in spirit samples was successfully demonstrated.
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•Three new naphthalimides exhibited strong fluorescence transitioning from blue to orange based on solvent polarity.•Computational calculations identified conformational preferences influencing emission wavelengths.•One of these compounds was effective for quantifying ethanol in spirit samples.