Intermolecular Interactions between Eosin Y and Caffeine Using¹H-NMR Spectroscopy

Abstract

DETECHIP has been used in testing analytes including caffeine, cocaine, and tetrahydrocannabinol (THC) from marijuana, as well as date rape and club drugs such as flunitrazepam, gamma-hydroxybutyric acid (GHB), and methamphetamine. This study investigates the intermolecular interaction between DETECHIP sensor eosin Y (DC1) and the analyte (caffeine) that is responsible for the fluorescence and color changes observed in the actual array. Using 1H-NMR, 1H-COSY, and 1H-DOSY NMR methods, a proton exchange from C-8 of caffeine to eosin Y is proposed.

In Situ Monitoring of Competitive Coformer Exchange Reaction by 1H MAS Solid-State NMR

“…The intermolecular hydrogen bonding involving NH···O or O–H···O and intramolecular hydrogen bonding involving O–H···O are observed in the range 13–21 ppm, depending on the hydrogen bonding strength . The spectrum of caffeine (Figure a) contains three methyl groups and one methylene group, and the peaks at 7.8 and 3.4 ppm correspond to the methylene hydrogen and the methyl groups, respectively . In the spectrum of glutaric acid (Figure c), two peaks are seen, one at 12.6 ppm, which is assigned to the acidic group, and the other at 2.2 ppm, corresponding to the −CH 2 group.…”

“…In this case also, the 24 The spectrum of caffeine (Figure 1a) contains three methyl groups and one methylene group, and the peaks at 7.8 and 3.4 ppm correspond to the methylene hydrogen and the methyl groups, respectively. 37 In the spectrum of glutaric acid (Figure 1c), two peaks are seen, one at 12.6 ppm, which is assigned to the acidic group, and the other at 2.2 ppm, corresponding to the −CH 2 group. These are in good agreement with reported values in the literature.…”

Characterization of the interaction between boscalid and tannic acid and its effect on the antioxidant properties of tannic acid

“…The 1 H‐NMR spectra were used to study the intermolecular interactions between boscalid and TA. The changes in the position and intensity on the NMR spectrum would indicate the characteristic peaks of molecules (Okuom et al., 2013). Figure 3A shows the 1 H‐NMR spectra of TA, the corresponding O–H protons peaks were 9.99 and 9.28 ppm, the C–H protons peaks on the benzene ring were 7.50–6.71 ppm, and the C–H protons peaks on the central glucose ring were 6.49–4.30 ppm (labeled a–c in Figure 3A).…”

“…Figure 3C,D shows a certain low‐field shift of the peak (Ha) associated with the O–H hydrogen atom of TA for the boscalid–TA complex, probably due to the hydrogen bonds between the amino group of boscalid and the hydroxyl group of TA. The formation of hydrogen bonds in NMR spectra is characterized by a decrease in the density of the electron cloud around the O–H hydrogen protons, a decrease in the shielding effect, an increase in the chemical shift value, and a shift of the spectrum to lower fields (Chen, Gao, et al., 2020; Okuom et al., 2013; Xie et al., 2019). The peaks related to the C–H hydrogen atoms of TA (Hb, Hc) also existed a low‐field shift, which may be due to the altered spatial environment of TA influenced by boscalid, resulting in strong CH–π interactions on the benzene and central glucose rings of TA (Hashidzume et al., 2010).…”

The Identification of Seven Chemical Warfare Mimics Using a Colorimetric Array

“…The color changes of the sensors in the array can been attributed to several mechanisms, including acid–base reactions, solvatochromic dye interactions, redox reactions, dipole–dipole interactions, and proton transfer reactions [27,28,29].…”