FT‐Raman, IR and UV‐visible spectral investigations and ab initio computations of a nonlinear food dye amaranth

Abstract

Amaranth (E123, Food Red 9, FD & C Red 2) is a sulfonated azo dye used as a color additive in foodstuffs, pharmaceuticals and cosmetics. FT-IR and FT-Raman spectra of amaranth were recorded and analyzed. Density functional theory (DFT) calculations were performed to derive the equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. The results of the optimized molecular structure gave clear evidence for the intramolecular charge transfer (ICT) and intramolecular hydrogen bonding in the molecule. Azo stretching wavenumbers are lowered owing to conjugation and p-electron delocalization. Time-dependent density functional theory (TD-DFT) calculations of the electronic spectra were performed on the optimized structure and compared with the experimental UV-visible spectrum. Vibrational spectra, natural bonding orbitals (NBO) analysis and optimized geometry indicate C-H· · ·N hydrogen bonding in the molecule. The first hyperpolarizability of the molecule was calculated. The optical nonlinearity of the dye is due to the donation of the electron density from the hydroxyl group of the conjugated system via naphthalene (2) ring into p * -orbital of the azo moiety.

Experimental and ab initio DFT calculated Raman spectrum of Sudan I, a red dye

“…[11,22,23] However, our calculations show that other modes such as movements within the hydrazo group also contribute significantly. Our calculations also indicate that the hydrazo group is involved in most of the vibrations through N-H and C-N N bendings and C-N stretchings.…”

“…Although the spectra look very similar to that of Sudan I in the region 1600-1100 cm −1 , the values of the Raman shifts deviate sufficiently to distinguish them. [22] The structure of the sulfonated yellow azo dye Tartrazine (1H-pyrazole-3-carboxylic acid, 4,5-dihydro-5-oxo-1(4-sulfophenyl)-4-[(4-sulfophenyl)azo] tri-sodium salt, CAS Reg. No.…”

Modified carbon fabric electrodes: preparation and electrochemical behavior toward amaranth electrolysis

“…As can be seen in the spectrum for the initial amaranth solution, two characteristic bands ascribed to SO 3 symmetric and asymmetric stretching vibrations and naphthalene rings deformation at 1,050 cm -1 (I) and 1,190 cm -1 (II) are identified. There is also a less intense band at around 1,625 cm -1 (III) that could correspond to the C-C stretching mode of the naphthalene ring [13]. The final sample from the electroreduction with better specific charge efficiency (on WE2D at 0 mV) was analyzed.…”

“…Samples taken during these processes were analyzed by ultraviolet (UV)-visible and FT-IR-ATR spectroscopies [13]. FT-IR-ATR spectra provided good evidences of the different pathways for the amaranth electrooxidation depending on the type of electrode and the presence/absence of chloride ions.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part III

“…Quite often, SERS was also employed to determine the orientation of the molecules on a metal surface. Such studies are compiled here for the following molecules: 1H-and 3H-imidazo [4,5-b]pyridine and their methyl derivatives, [113] copper(II) chloride and bromide compounds of KCuBr 3 , [114] 5,6-diméthyluracile, [115] [C(NH 2 ) 3 ] 2 M II (H 2 O) 4 (SO 4 ) 2 , M II = Mn, Cd and VO, [116] potassium trimethylsilanolate, [117] 2-aminopyridinium-4-hydroxybenzenosulfonate, [118] the H 4 I 2 O 10 2− ion in CuH 4 I 2 O 10 · 6H 2 O, [119] 2-amino-4,6-dihydroxypyrimidine, [120] 3 (or 4 or 6)-methyl-5-nitro-2-pyridinethiones, [121] 2-methyl-4-nitroaniline (MNA) crystal, [122] 2-amino-5-chloropyridinium hydrogen selenate, [123] the food dye amaranth, [124] transstilbene in the excited singlet state, [125] chloramphenicol, [126] oroxylin, [127] 4-fluoro-N-(2-hydroxy-4-nitrophenyl)benzamide, [128] phenanthridine, [129] 3,5 dichloro hydroxy benzaldehyde and 2,4 dichloro benzaldehyde. [130] Solid State (Minerals, Crystals, Linear Chains, Glasses, Ceramics and Disordered Materials) Minerals A great number of minerals have been studied during 2008 by the Frost group [131 -146] using both Raman and infrared spectroscopies: smithsonite, [131] the uranyl carbonate mineral voglite, [132] hydrotalcite with CO 3 2− and (MoO 4 ) 2− anions in the interlayer, [133] the uranyl phosphate minerals phosphuranylite and yingjiangite, [134] the uranyl carbonate mineral zellerite, [135] the molybdate-containing uranyl mineral calcurmolite, [136] the oxalate mineral wheatleyite Na 2 Cu 2+ (C 2 O 4 ) 2 ·2H 2 O, [137] the nickel silicate mineral pecoraite, [138] synthetic nesquehonite, [139] the uranyl mineral, compreignacite, K 2 [(UO 2 ) 3 O 2 (OH) 3 ] 2 ·7H 2 O, [140] the hydroxy nickel carbonate minerals nullaginite and zaratite, …”