{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,1,14]],"date-time":"2025-01-14T08:49:43Z","timestamp":1736844583757,"version":"3.33.0"},"reference-count":21,"publisher":"International Union of Crystallography (IUCr)","issue":"1","license":[{"start":{"date-parts":[[2016,1,1]],"date-time":"2016-01-01T00:00:00Z","timestamp":1451606400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/2.0\/uk\/legalcode"},{"start":{"date-parts":[[2016,1,1]],"date-time":"2016-01-01T00:00:00Z","timestamp":1451606400000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/2.0\/uk\/legalcode"}],"content-domain":{"domain":["iucr.org","wiley.com","iucrj.org"],"crossmark-restriction":true},"short-container-title":["Acta Crystallogr E Cryst Commun","Acta Cryst E","Acta Cryst Sect E","Acta Crystallogr E","Acta Crystallogr Sect E","Acta Cryst E Cryst Commun","Acta Cryst Sect E Cryst Commun"],"published-print":{"date-parts":[[2016,1,1]]},"abstract":"<jats:p>The crystal structures of two chromone derivatives,<jats:italic>viz.<\/jats:italic>ethyl 6-(4-methylphenyl)-4-oxo-4<jats:italic>H<\/jats:italic>-chromene-2-carboxylate, C<jats:sub>19<\/jats:sub>H<jats:sub>16<\/jats:sub>O<jats:sub>4<\/jats:sub>, (<jats:bold>1<\/jats:bold>), and ethyl 6-(4-fluorophenyl)-4-oxo-4<jats:italic>H<\/jats:italic>-chromene-2-carboxylate C<jats:sub>18<\/jats:sub>H<jats:sub>13<\/jats:sub>FO<jats:sub>4<\/jats:sub>, (<jats:bold>2<\/jats:bold>), have been determined: (<jats:bold>1<\/jats:bold>) crystallizes with two molecules in the asymmetric unit. A comparison of the dihedral angles beween the mean planes of the central chromone core with those of the substituents, an ethyl ester moiety at the 2-position and a<jats:italic>para<\/jats:italic>-substituted phenyl ring at the 6-position shows that each molecule differs significantly from the others, even the two independent molecules (<jats:italic>a<\/jats:italic>and<jats:italic>b<\/jats:italic>) of (<jats:bold>1<\/jats:bold>). In all three molecules, the carbonyl groups of the chromone and the carboxylate are<jats:italic>trans<\/jats:italic>-related. The supramolecular structure of (<jats:bold>1<\/jats:bold>) involves only weak C\u2014H...\u03c0 interactions between H atoms of the substituent phenyl group and the phenyl group, which link molecules into a chain of alternating molecules<jats:italic>a<\/jats:italic>and<jats:italic>b<\/jats:italic>, and weak \u03c0\u2013\u03c0 stacking interactions between the chromone units. The packing in (<jats:bold>2<\/jats:bold>) involves C\u2014H...O interactions, which form a network of two intersecting ladders involving the carbonyl atom of the carboxylate group as the acceptor for H atoms at the 7-position of the chromone ring and from an<jats:italic>ortho<\/jats:italic>-H atom of the exocyclic benzene ring. The carbonyl atom of the chromone acts as an acceptor from a<jats:italic>meta<\/jats:italic>-H atom of the exocyclic benzene ring. \u03c0\u2013\u03c0 interactions stack the molecules by unit translation along the<jats:italic>a<\/jats:italic>axis.<\/jats:p>","DOI":"10.1107\/s2056989015022781","type":"journal-article","created":{"date-parts":[[2015,12,3]],"date-time":"2015-12-03T16:25:10Z","timestamp":1449159910000},"page":"8-13","update-policy":"https:\/\/doi.org\/10.1107\/cm_01","source":"Crossref","is-referenced-by-count":0,"title":["Crystal structures of ethyl 6-(4-methylphenyl)-4-oxo-4<i>H<\/i>-chromene-2-carboxylate and ethyl 6-(4-fluorophenyl)-4-oxo-4<i>H<\/i>-chromene-2-carboxylate"],"prefix":"10.1107","volume":"72","author":[{"given":"Ligia R.","family":"Gomes","sequence":"first","affiliation":[]},{"given":"John Nicolson","family":"Low","sequence":"additional","affiliation":[]},{"given":"Carlos","family":"Fernandes","sequence":"additional","affiliation":[]},{"given":"Alexandra","family":"Gaspar","sequence":"additional","affiliation":[]},{"given":"Fernanda","family":"Borges","sequence":"additional","affiliation":[]}],"member":"329","published-online":{"date-parts":[[2016,1,1]]},"reference":[{"key":"hb7543_bb1","doi-asserted-by":"crossref","first-page":"8554","DOI":"10.1063\/1.475007","volume":"107","author":"Becke","year":"1997","journal-title":"J. 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