Theoretical calculation of newly synthesized tetrazolopyrimidine derivatives as a potential corrosion inhibitor

J. Serb. Chem. Soc. 87 (5) 575–587 (2022) JSCS–5542 Original scientific paper Published 23 March 2022 Theoretical calculation of newly synthesized tetrazolopyrimidine derivatives as a potential corrosion inhibitor ERDEM ERGAN1*, NURULLAH SEKER2, BEGUM CAGLA AKBAS3 and ESVET AKBAS2 1Department of Property Protection and Security, Van Security Vocational School, Van Yuzuncu Yil University, 65080, Van- Turkey, 2Department of Chemistry, Faculty of Science, Van Yuzuncu Yil University, 65080 Van-Turkey and 3Faculty of Pharmacy, University of Inonu, Malatya, Turkey (Received 19 April, revised 14 July, accepted 4 August 2021) Abstract: In this work, we wanted to define a general and comprehensive strategy for the synthesis of tetrazolo[1,5-a]pyrimidine derivatives. For this purpose, we obtained new tetrazolo[1,5-a]pyrimidine molecules via the mercurypromoted desulfurization reaction, including hydrolysis, cyclizations, and eliminations. All of the molecules were characterized by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis. On the other hand, the potentials of compounds as corrosion inhibitors were calculated at B3LYP/6-31G (d, p) level via density functional theory (DFT). Keywords: desulfurization; DFT; characterization; quantum chemical studies; sodium azide. INTRODUCTION Corrosion is the deterioration of metal by reacting with chemicals or the environment. Corrosive solutions are used in many industrial applications. Acid solutions widely used in industry, especially in the cleaning process cause a significant mass loss on the surface.1–3 Many methods are used to prevent corrosion. One of the methods of preventing corrosion is to use protective materials. Organic compounds are also one of the important materials used as protective materials. The organic compounds containing π-bonds, phosphorus, sulfur, oxygen, and nitrogen as well as aromatic rings in their structure interacts with the metal surface and show high inhibition property.4 The compounds containing both nitrogen and sulfur can provide excellent inhibition, compared with compounds containing only nitrogen or sulfur.5 Generally, a strong interaction causes higher * Corresponding author. E-mail: https://doi.org/10.2298/JSC210419067G 575 Available on line at www.shd.org.rs/JSCS/ ________________________________________________________________________________________________________________________ (CC) 2022 SCS. 576 ERGAN et al. inhibition efficiency, the inhibition increases in the sequence O < N < S.6 It has been reported to increase the inhibition efficiency in general that compounds containing heteroatoms (S, N and O) with free electron pairs, delocalized π-electron aromatic rings, molecular weight, alkyl chains, and generally as a result of the existence of substituted groups. Compounds with π-bonds also generally exhibit good inhibitive properties due to the interaction of π-orbital with the metal surface.7 It is preferred that the compounds used for corrosion inhibiting purposes are not harmful to nature. For this reason, pyrimidine derivatives have attracted great attention due to their less environmentally damaging properties.8 However; studies on pyrimidine are limited despite their ease of availability and corrosion inhibition properties. Pyrimidine derivatives are among the important class of organic compounds. They exhibit broad biochemical effects due to the activity of nitrogen atoms in the ring and carbon atoms in the C2/C4/C6 position.9 Due to these properties, pyrimidine derivative compounds are used as active ingredients in drugs such as uramustine, piritrexim, isethionate, tegafur, floxuridine, fluorouracil, cytarabine and methotrexate.10 Pyrimidine derivatives are promising concerning corrosion inhibition.11 Experimental techniques like the weight-loss method, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, etc., have been used to understand the corrosion process and its inhibition.12,13 Although experiments mostly are time-consuming, costly, and lacking in explaining the mechanism of inhibition of the corrosion.14,15 Thus, the quantum chemical calculation method was endorsed as a potent and easy tool to reduce the cost and time and can help in the interpretation of the experimental findings.16,17 Heakal et al.18 used quantum chemical calculations to determine the structural and electronic properties of imidazole-pyrimidine-based new ionic compounds. They compared the theoretical inhibition yields of the compounds prepared in this way. Molecules chosen as inhibitors must be capable of donating electrons to the empty d-orbital of the metal and also be suitable for forming anti-feedback bonds. Pyrimidine compounds have these properties. Therefore, pyrimidine derivatives are expected to be excellent corrosion inhibitors at the industrial level.19 Quantum chemical calculations (QCCs) are widely used to find the corrosion inhibition reactivity of organic molecules. The effectiveness of an inhibitor can be related not only to its spatial molecular structure but also its molecular electronic structure. According to frontier orbital theory, the reaction of reactants mainly occurred on highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and the formation of a transition state is due to an interaction between the frontier orbitals of the reactants. So, it was imp- Available on line at www.shd.org.rs/JSCS/ ________________________________________________________________________________________________________________________ (CC) 2022 SCS. TETRAZOLOPYRIMIDINE DERIVATIVES AS A POTENTIAL CORROSION INHIBITOR 577 ortant to investigate the distribution of HOMO and LUMO for the exploration of the inhibition mechanism. The difference between ELUMO and EHOMO energies is called the energy gap (ΔE). It was generally acknowledged that low values of ΔE will provide good inhibition efficiency because the energy for removing an electron from the last occupied orbital will be low. For the theoretical calculation of the inhibitory effect of a molecule, it is necessary to know the ionization potential (I), the electron affinity (A), the chemical hardness-softness (S), the global electrophilicity index (ω), the interaction between the transmitted electron fraction index (ΔN), the interaction between back donations and non-linear optical (NLO) properties. All these values were calculated according to Shojaie et al. 20 using DFT-based QCCs in the Gaussian 09 software.21 EXPERIMENTAL Chemicals and instruments All chemicals and solvents used in the experiments were assured from Turkey representative of Sigma Aldrich and Fluka (Buchs, Switzerland). All reactions were monitored by thin-layer chromatography (TLC). TLC plates were based on silica gel 60 F254 aluminum plates with a 0.2 mm layer thickness (Merck Co., Darmstadt, Germany). The spots in TLC were determined by the UV lamp. Stuart (UK) SMP30 melting point apparatus was used to measure the (...truncated)