Synthesis, characterization and molecular structures of homologated analogs of 2-bromo-3-(n-alkylamino)-1,4-napthoquinone

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• 作者：Sunita Salunke-Gawali ; Omkar Pawar ; Milind Nikalje ; Rishikesh Patil ; Thomas Weyherm眉ller ; Vedavati G. Puranik ; V. Badireenath Konkimalla
• 关键词：蟺&ndash ; 蟺 Stacking ; Aminonaphthoquinone ; Hydrogen bonding ; Michael addition ; 2 ; 3-Dibromo-1 ; 4-naphthoquinone
• 刊名：Journal of Molecular Structure
• 出版年：6 January, 2014
• 年：2014
• 卷：1056-1057
• 期：Complete
• 页码：97-103
• 全文大小：1376 K

文摘

Four analogues of 2-bromo-3-(n-alkylamino)-1,4-napthoquinone (where n-alkyl is methyl in L-1Br, ethyl in L-2Br, propyl in L-3Br and butyl in L-4Br) are synthesized and characterized. A reaction mechanism is proposed for the formation of L-1Br to L-4Br from the starting material 2,3-dibromo-1,4-naphthoquinone. The 谓_NH frequency in the FT-IR spectra is affected by the intramolecular hydrogen bonding in L-1Br to L-4Br and is observed 鈭?267 cm^鈭? in L-2Br. A shift of 鈭?5 cm^鈭? is observed in the 谓_CBr frequency in all the compounds as compared to 2,3-dibromo-1,4-naphthoquinone (627 cm^鈭?). A broad charge transfer band is observed between 400 and 600 nm in the UV-Vis spectra, which imparts red colour to all the compounds. Molecular structures of L-2Br and L-3Br were studied by single crystal X-ray diffraction studies. Molecules of L-2Br crystallize in Pca2₁, whereas the molecule L-3Br crystallizes in the P-1 space group. Molecules of L-2Br forms a polymeric chain through NH鈰疧 interaction and forms beautiful butterfly like arrangement of molecules when viewed down the 鈥?em>a鈥?axis. Ladder like polymeric chain of molecules is observed in L-3Br via CH鈰疧 and NH鈰疧 interactions. Every alternating neighbouring chains of L-3Br, show 蟺-蟺 stacking interactions between the quinonoid rings of the molecules, however this interaction is not observed in L-2Br.