TY - JOUR
T1 - Molecular structure and mild steel/HCl corrosion inhibition of 4,5-Dicyanoimidazole
T2 - Vibrational, electrochemical and quantum mechanical calculations
AU - Abuelela, Ahmed M.
AU - Bedair, Mahmoud A.
AU - Zoghaib, Wajdi M.
AU - Wilson, Lee D.
AU - Mohamed, Tarek A.
N1 - Funding Information:
The NH moiety gives rise to three vibrations; stretch, in-plane deformation and out-of-plane bending vibrations. Owing to intermolecular/intramolecular HB interactions, the NH vibrations are likely to be sensitive to the environment, so they show NH stretch around 3300 cm−1 [29]. Assigned herein for a strong broad band at 3261, suggesting a strong intermolecular HB interactions which agrees with the calculated SPs and recorded X-ray data [25]. On the other hand benzothiazoline-2-thione (BTT) [30], benzoxazoline-2-thione (BOT) [31], Adenine [32] molecules reflect less HB interactions owing to the observed infrared bands at 3402w, 3311sh, 3347sh cm−1, respectively. The higher frequency shift in BTT was due to weak hydrogen bonding showed by its low dimerization percentage 2.5% with respect to its analogue BOT 11.9%. This assignment was confirmed by the calculated percentage of NH/ND which is 0.74 and it is consistent with our previous studies [32-34]. Calculated frequencies due to Deuteration of DCI Hydrogen atoms (CD/ND) are presented in Table 3. The recorded IR intensity (Fig. 1A) is in good agreement with the calculated 102.3 kcal/mol at 3634 cm−1 using B3LYP/6-31g(d) calculations and the potential energy distribution is strongly assigning this mode by 100% while the band is weak in Raman spectrum (Fig. 1B). The NH in-plane bending vibration is found to be highly mixed with CN ring stretch vibrations with contributions ranges 20-33%. Therefore, recorded mode at 1124 (m/w) (IR/Raman) cm−1 is supported by only 25% PED at 1151 cm−1 calculated by B3LYP/6-31g(d). The NH out-of-plane bending is found at 518 (s/w) (IR/Raman) cm−1 in good agreement with that calculated at 567 cm−1 confirmed by 64% PED (Table 3).
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2021/4/15
Y1 - 2021/4/15
N2 - Raman (3500-50 cm−1) and FT-ATR/FT-infrared (3500-500/4000-200 cm−1) spectrum of 4,5-Dicyanoimidazole (DCI) were recorded and analyzed by normal coordinate analysis calculations. In addition, we have studied the molecular structure of DCI by means of B3LYP Density Functional Theory (DFT) using 6-31g(d) basis set. Aided by computational outcomes, all vibrational bands were assigned quantitatively to their corresponding fundamentals. The corrosion inhibition efficiency of DCI towards mild steel in 1.0 M HCl has been investigated experimentally and theoretically. Electrochemical impedance spectroscopy, electrochemical frequency modulation and polarization measurements along with thermodynamic predictions were assigned to both the anodic and cathodic inhibition. DCI-metal interactions and charge reallocation were analyzed in terms of Frontier molecular orbital (FMO) and Natural bond orbital (NBO) analysis. Global reactivity descriptors; ionization potential (IP), electron affinity (A), electronegativity (χ), chemical potential (µ), chemical hardness (η), and electrophilicity index have been calculated and assigned to the inhibition efficiency. Good correlation between the theoretical calculations and experimental measurments has been achieved. The results are compared with similar molecular systems whenever appropriate.
AB - Raman (3500-50 cm−1) and FT-ATR/FT-infrared (3500-500/4000-200 cm−1) spectrum of 4,5-Dicyanoimidazole (DCI) were recorded and analyzed by normal coordinate analysis calculations. In addition, we have studied the molecular structure of DCI by means of B3LYP Density Functional Theory (DFT) using 6-31g(d) basis set. Aided by computational outcomes, all vibrational bands were assigned quantitatively to their corresponding fundamentals. The corrosion inhibition efficiency of DCI towards mild steel in 1.0 M HCl has been investigated experimentally and theoretically. Electrochemical impedance spectroscopy, electrochemical frequency modulation and polarization measurements along with thermodynamic predictions were assigned to both the anodic and cathodic inhibition. DCI-metal interactions and charge reallocation were analyzed in terms of Frontier molecular orbital (FMO) and Natural bond orbital (NBO) analysis. Global reactivity descriptors; ionization potential (IP), electron affinity (A), electronegativity (χ), chemical potential (µ), chemical hardness (η), and electrophilicity index have been calculated and assigned to the inhibition efficiency. Good correlation between the theoretical calculations and experimental measurments has been achieved. The results are compared with similar molecular systems whenever appropriate.
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U2 - 10.1016/j.molstruc.2020.129647
DO - 10.1016/j.molstruc.2020.129647
M3 - Article
AN - SCOPUS:85097073218
SN - 0022-2860
VL - 1230
JO - Journal of Molecular Structure
JF - Journal of Molecular Structure
M1 - 129647
ER -