Hydrogen Bonding-Induced Unique Charge-Transfer Emission from Multichromophoric Polypyridyl Ligands: Ratiometric Probing of Methanol Impurity in Commercial Biofuels

Abstract

This work is focused on utilizing fluorescent molecules for sensing the methanol content in (bio)­fuels. Multichromophoric polypyridyl ligands with pyrene (1) and anthracene (2) as aryl residues have been synthesized. The twisted geometry of the probe molecules in both the solid state and aprotic solvents significantly curtails the electronic communication between the aryl moiety and pyridyl ligand (terpyridine). However, the excited-state hydrogen bonding interactions of methanol with terpyridine nitrogens result in the formation of a nearly planar conformation with larger charge separation. Thus, a broad “structureless” fluorescence spectrum was observed specifically in methanol with an exceptionally large Stokes shift (detection limit: 0.13%). However, the extent of redshift was found to be attributed to the angle of twisting as well as the electronic nature of the aryl moiety. Considering its high sensitivity, probe 1 is utilized for the detection of methanol impurity in soy-based biodiesel samples, like B100, B20, and so on. Interference studies indicate that the presence of competitive byproducts, such as monoglycerides and diglycerides, or unconsumed starting materials, such as fatty acid methyl esters poses no serious threats in methanol detection. Finally, the methanol-specific fluorescence response has been utilized to design paper strips for on-location detection of methanol contamination in biofuel samples.

A pyrene-based ratiometric probe for nanomolar level detection of glyphosate in food and environmental samples and its application for live-cell imaging

“…Unlike pyrene and many of its alkylated derivatives, the absorption spectra of 1 appeared to be slightly broadened and red-shifted, indicating strong electronic communication between the pyrene unit bispicolyl residue. 13 On the other hand, when the fluorescence spectra of 1 were recorded in organic solvents of different polarities, polarity-dependent red-shifts in λ max were observed (Fig. 2b and Fig.…”

Moisture-Sensitive Ratiometric Color-Changing Response: a Useful Tool for Precision Farming

“…The extent of solvation of fluoride ions in a methanol or ethanol medium is reasonably restricted due to limited hydrogen bonding ability. 17 This indicates that 1.F − is selective toward water, even in comparison to other alcoholic solvents.…”

“…When other alcoholic solvents, like MeOH or ethanol, were added to 1 .F – in anhydrous CH 3 CN, the extent of color change was less prominent than that observed with water. The extent of solvation of fluoride ions in a methanol or ethanol medium is reasonably restricted due to limited hydrogen bonding ability . This indicates that 1 .F – is selective toward water, even in comparison to other alcoholic solvents.…”

Highly selective and discriminative detection of small alcohols based on a dual-emission macrocyclic samarium complex

“…In particular, small alcohols (methanol, ethanol and propanol) are frequently used organic solvents for various syntheses in chemical industries. [2][3][4][5][6][7][8][9] Nowadays, the development of reliable, rapid, selective, sensitive and simple techniques for detecting small alcohol has been an urgent demand not only in traditional brewing, pharmaceutical, clinical and chemical elds but also in booming alcohol-based renewable energy industries. Aer many years of great efforts, researchers have reported many technologies for detecting small alcohols using sophisticated instruments, such as the GC, 10 HPLC, 11 FT-IR, 12 NIR, 13 MS, 14 NMR, 15 Raman spectroscopy, 16 and ame ionization detectors.…”

“…For instance, alcohol, found in an early period of human society, has played very important roles in liquors, 2 disinfectants, 3 and fuels. 4 Methanol is a crucial chemical raw material to produce formaldehyde, 5 formic acid, 6 pesticides, 7 and so on. Polyols, the 1,3-PDO, 8 are commonly used as intermediates in drug synthesis, and glycerol 9 is commonly used as humectants in skincare products.…”