Synthesis and characterization of 1,4-chalcogenesters bearing 5-membered heterocycles
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Indian Academy of Sciences Sadhana (0123456789().,-volV)FT3](0123456 789().,-volV)
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Synthesis and characterization of 1,4-chalcogenesters bearing 5-membered heterocycles KHALED AL KHALYFEHa,*, DEEB TAHERb,* , WISSAM HELALb, MARCUS KORBc, IMAD HAMADNEHb, AMMAR AL-DUJAILId, AMER IMRAISHe, HANA M HAMMADe, RANDA M AL-AS’ADa, SULTAN T ABU-ORABIf, ALEXANDER HILDEBRANDTg and HEINRICH LANGg a Department
of Chemistry, Faculty of Natural Sciences, Al-Hussein Bin Talal University, P.O. Box 20, Ma’an, Jordan b Department of Chemistry, The University of Jordan, Amman 11942, Jordan c Faculty of Science, School of Molecular Sciences, The University of Western Australia, Crawley, Perth, WA 6009, Australia d Hamdi Mango Center for Scientific Research, The University of Jordan, Amman 11942, Jordan e Department of Biological Sciences, The University of Jordan, Amman 11942, Jordan f Department of Chemistry, Yarmouk University, Irbid 21163, Jordan g Faculty of Natural Sciences, Institute of Chemistry, Inorganic Chemistry, Technische Universita¨t Chemnitz, 09107 Chemnitz, Germany E-mail: [email protected]; [email protected] MS received 29 March 2020; revised 2 July 2020; accepted 6 July 2020
Abstract. Treatment of 1,4-(SeSiMe3)2-C6H4 (1) with two equiv of ClC(O)R (2) (a, R = 2-cC4H3O; b, R = 2-cC4H3S; c, R = 3-cC4H3S) produced the corresponding phenylene carboselenolates 1,4-(SeC(O)R)2C6H4 (3a–c), while the reaction of 1,4-(SLi)2-C6H4 (4) with ClC(O)R (2) in a 1:2 molar ratio gave phenylene carbothiolates 1,4-(SC(O)R)2-C6H4 (5a–c). Compounds 3a–c and 5a–c were characterized by elemental analysis, NMR (1H, 13C{1H}, 77Se{1H}) and IR spectroscopy. The molecular structures of 3a–c and 5a–c in the solid state were determined by single-crystal X-ray structure analysis. The carbochalcogenato groups and the heteroatoms of the 5-membered rings are in an anti-arrangement with respect to each other. Cyclic voltammetry measurements show irreversible reduction processes for the 5-membered heterocyclic redox moiety in which reduction of these compounds lead to decomposition of the original compounds to unidentified species and show redox potentials between 1480 and 1580 mV for 3a-c and 1470-1490 mV for 5a-c, relative to the FcH/FcH? redox couple. Also, thioester-functionalized systems 5a-c show significantly higher reduction potentials as compared to selenoesters 3a-c, reflecting the minor electron-donating effect of the sulfur atoms. The molecular electronic structures of the title compounds were additionally investigated by DFT calculations, revealing different degrees of HOMO-LUMO energy gaps within the series of 3a–c and 5a–c, due to a lowering in LUMO energy, depending on the nature of the heterocyclic ring. The calculations showed that the HOMO and LUMO are mainly located on the selenoester/thioester functionalized heterocyclic. The phase transition temperatures and enthalpies of the title compounds were detected by differential scanning calorimetry (DSC) analysis and the phases are confirmed by polarizing optical micro
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