Journal of Molecular Structure 1224 (2021) 129145 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstr Synthesis, electrochemistry, in-situ spectroelectrochemistry and molecular structures of 1,4-naphthoquinone derivatives Nahide Gulsah Deniz a,∗ , Cigdem Sayil a , Duygu Akyüz b , Atif Koca c a Division of Organic Chemistry, Department of Chemistry, Engineering Faculty, Istanbul University-Cerrahpasa, 34320, Avcilar, Istanbul, Turkey b Department of Chemistry, Faculty of Science, Gebze Technical University, 41400, Gebze, Kocaeli, Turkey c Department of Chemical Engineering, Engineering Faculty, Marmara University, 34722, Goztepe, Istanbul, Turkey a r t i c l e i n f o Article history: Received 18 May 2020 Revised 19 August 2020 Accepted 24 August 2020 Available online 25 August 2020 Keywords: Naphthoquinones Spectroelectrochemistry Electrochemical behaviors Cyclic voltammetry in-situ UV-Vis spectroelectrochemistry Crystal structure a b s t r a c t A novel series of 1,4-naphthoquinones substituted containing sulfur, nitrogen, oxygen atoms were synthe- sized. The structures of the novel products were characterized by using the various spectroscopic tech- niques such as 1 H nuclear magnetic resonance (NMR), 13 C NMR, mass spectrometry (MS), Fourier trans- form infrared spectroscopy (FT-IR) and microanalysis. The crystal structures of 2,3-bis(benzylsulfanyl)-1,4- napthoquinone 4 and 2,3-bis(ethylsulfanyl)-1,4-naphthoquinone 7 were determined by using X-ray single crystal diffraction method. Electrochemical behaviors of some 1,4-naphthoquinone (NQ) derivatives 3, 4, 7, 8, 9, 10, 12, 13, 15, 16, 17, 19 and 20 were studied by using cyclic voltammetry, square wave voltamme- try and in-situ UV-Vis spectroelectrochemistry. The substituents of the NQ derivatives significantly altered the redox mechanism. In-situ UV-Vis spectroelectrochemical analyses of NQs supported the proposed re- dox mechanism. © 2020 Elsevier B.V. All rights reserved. 1. Introduction Naphthoquinone derivatives occur naturally as plant con- stituents, and many of these have found use as colorant in the past. The color of the naphthoquinone compounds can be produced in the 1,4-naphthoquinone chromogen by introducing amino and hydroxyl groups into the quinoid ring, into the ben- zenoid ring, or into both rings. The advantage of the naphtho- quinone dyes is their strong and stable coloring ability [1], so they are extensively used in the cosmetics industry in the produc- tion of cosmetic dyes, especially hair dyes. Heterocyclic naphtho- quinone derivatives have been gaining importance in the manu- facturing of dyes and pigments because of their substantivity to cellulosic and hydrophobic fibers [2]. Moreover, particularly 1,4- naphthoquinones are widely distributed phenolic compounds in nature such as naphthoquinones are reported to exhibit diverse pharmacological properties like antibacterial [3], antifungal, antivi- ral, anti-inflammatory antipyretic and anticancer activity [4]. These 1,4-naphthoquinones have the ability to induce oxidative stress which is responsible for initiation of tissue damage selectively in tumor cells and this seems to be a promising approach for target- ing cancer cells [5]. ∗ Correspondence author. E-mail address: yurdakul@istanbul.edu.tr (N.G. Deniz). Because of their biological importance, the redox reactions of the 1,4-naphthoquinone derivatives have been investigated to their usage in various biological and electrochemical fields such as cor- rosion inhibitor, antimicrobials and sensors [6–9]. Thus, it becomes necessary to understand the factors which regulate the potentials and reaction pathways of these 1,4-naphthoquinone species. While the quinone derivatives undergo a two-step reduction with two- step hydrogenation in aqueous media, they are first reduced to its radical anion and then to the dianion in aprotic solvents. While the ideal reduction reactions are the two identical reduction cou- ples with similar peak currents and peak to peak separation, sub- stituent environments of the quinone derivatives frequently cause deviation significantly from those expected for a simple two-step reaction [10–16]. It has been observed that most of their activities are associated with their redox behavior. Thus, electrochemical ex- aminations of synthesized 1,4-naphthoquinone derivatives (3, 4, 7, 8, 9, 10, 12, 13, 15, 16, 17, 19, 20) were carried out in this study in order to use these moieties for the practical applications in elec- trochemical technologies in the future. 2. Materials and methods 2.1. Experimental section Melting points were measured on a Buchi B-540 melting point apparatus. TLC plates silica 60F 254 (Merck, Darmstadt), detection https://doi.org/10.1016/j.molstruc.2020.129145 0022-2860/© 2020 Elsevier B.V. All rights reserved.