249:
174:
53:
44:
859:
31:
1393:
778:
Infrared and Raman assignments indicate that the equalization of the carbon–carbon bond lengths, thus the electronic delocalization, follows with an increase in counter-ion size for salts. This result leads to a further interpretation that the degree of aromaticity is enhanced for salts as a function
1352:
Wang, Chih-Chieh; Ke, Meu-Ju; Tsai, Cheng-Hsiao; Chen, I-Hsuan; Lin, Shin-I; Lin, Tzuen-Yeuan; Wu, Li-Mei; Lee, Gene-Hsiang; Sheu, Hwo-Shuenn; Fedorov, Vladimir E. (2009-02-04). "2− as a
Building Block for Hetero- and Homo-bimetallic Coordination Polymers: From 1D Chains to 3D Supramolecular
1234:
Faria, L. F. O.; Soares, A. L. Jr.; Diniz, R.; Yoshida, M. I.; Edwards, H. G. M.; de
Oliveira, L. F. C. (2010). "Mixed salts containing croconate violet, lanthanide and potassium ions: Crystal structures and spectroscopic characterization of supramolecular compounds".
1063:
Georgopoulos, S. L.; Diniz, R.; Yoshida, M. I.; Speziali, N. L.; Dos Santos, H. F.; Junqueira, G. M. A.; de
Oliveira, L. F. C. (2006). "Vibrational spectroscopy and aromaticity investigation of squarate salts: A theoretical and experimental approach".
696:
above 400 K (127 °C), indeed the organic crystal with the highest spontaneous polarization (about 20 μC/cm). This is due to proton transfer between adjacent molecules in each pleated sheet, rather than molecular rotation.
783:
calculations for the optimized structures and vibrational spectra which were in agreement with experimental findings. The values for calculated theoretical indices of aromaticity also increased with counterion size.
1324:
M., S. C.; Ghosh, A. K.; Zangrando, E.; Chaudhuri, N. R. (2007). "3D supramolecular networks of Co(II)/Fe(II) using the croconate dianion and a bipyridyl spacer: Synthesis, crystal structure and thermal study".
1269:
West, R.; Niu, H. Y. (1963). "New aromatic anions. VI. Complexes of croconate ion with some divalent and trivalent metals (Complexes of divalent transition metal croconates and trivalent metal croconates)".
1183:
Horiuchi, S.; Tokunaga, Y.; Giovannetti, G.; Picozzi, S.; Itoh, H.; Shimano, R.; Kumai, R.; Tokura, Y. (2010). "Above-room-temperature ferroelectricity in a single-component molecular crystal".
1297:
Carranza, J.; Sletten, J.; Lloret, F.; Julve, M. (2009). "Manganese(II) complexes with croconate and 2-(2-pyridyl)imidazole ligands: Syntheses, X-ray structures and magnetic properties".
874:(brown), and iron (purple). These compounds also include hydroxyl groups as well as hydration water and have a more complicated crystal structure. No indication was found of
851:
atom, and to the next metal through its two opposite oxygens, leaving two oxygens unbound. Each metal is bound to three croconate oxygens and to one water molecule.
288:
882:, for example), but the anion can form metal complexes with a large variety of bonding patterns, involving from only one to all five of its oxygen atoms.
661:
In the solid state, croconic acid has a peculiar structure consisting of pleated strips, each "page" of the strip being a planar ring of 4 molecules of
847:
crystal structure, consisting of chains of alternating croconate and metal ions. Each croconate is bound to the preceding metal by one
263:
1158:
1110:
Braga, D.; Maini, L.; Grepioni, F. (2002). "Croconic acid and alkali metal croconate salts: Some new insights into an old story".
1123:
131:
544:
and symmetric, as the double bond and the negative charges become delocalized over the five CO units (with two electrons,
1145:
Dunitz, J. D.; Seiler, P.; Czechtizky, W. (2001). "Crystal structure of potassium croconate dihydrate, after 175 years".
206:
227:
633:" or "egg yolk". The structure of ammonium croconate was determined by Baenziger et al. in 1964. The structure of
380:
354:
780:
1397:
768:
1033:
Gelb, R. I.; Schwartz, L. M.; Laufer, D. A.; Yardley, J. O. (1977). "The structure of aqueous croconic acid".
986:
169:
1428:
1413:
792:
600:
1192:
1073:
71:
244:
1418:
916:
97:
545:
1216:
855:
also forms a compound with the same formula (yellow) but the structure appears to be different.
1423:
1370:
1208:
1162:
1127:
1006:
Schwartz, L. M.; Gelb, R. I.; Yardley, J. O. (1975). "Aqueous dissociation of croconic Acid".
408:
1362:
1334:
1306:
1279:
1244:
1200:
1154:
1119:
1081:
1042:
1015:
953:
891:
875:
800:
704:
salts, the croconate anions and the alkali cations form parallel columns. In the mixed salt
311:
151:
52:
215:
901:
107:
1196:
1077:
248:
173:
896:
688:, while the free molecule is estimated to have a dipole of 7–7.5 D. The solid is
620:
374:
43:
1407:
1220:
689:
677:
344:
162:
17:
1085:
906:
844:
775:
effects, where the delocalized electrons of two stacked croconate anions interact.
701:
438:
195:
911:
858:
772:
693:
604:
541:
1338:
1310:
1248:
334:
142:
1374:
879:
867:
836:
557:
1212:
1166:
1131:
779:
of the size of the counter-ion. The same study provided quantum mechanical
30:
1392:
1159:
10.1002/1521-3773(20010504)40:9<1779::AID-ANIE17790>3.0.CO;2-6
944:
Yamada, K.; Mizuno, N.; Hirata, Y. (1958). "Structure of croconic acid".
871:
573:
569:
465:
442:
1283:
1204:
1124:
10.1002/1521-3765(20020415)8:8<1804::AID-CHEM1804>3.0.CO;2-C
1046:
1019:
957:
866:
The croconate anion also forms compounds with trivalent cations such as
852:
788:
681:
577:
565:
561:
549:
454:
182:
1366:
848:
840:
832:
820:
796:
630:
589:
581:
553:
461:
450:
446:
767:
Salts of the croconate anion and its derivatives are of interest in
373:
Except where otherwise noted, data are given for materials in their
764:), the hydrogen is shared equally by two adjacent croconate units.
619:
Croconic acid and potassium croconate dihydrate were discovered by
857:
685:
608:
596:
499:
130:
120:
878:
between the delocalized electrons and the metal (as are seen in
828:
824:
585:
624:
540:
are also quite stable. The croconate ion, in particular, is
349:> 300 °C (572 °F; 573 K) (decomposes)
232:
51:
42:
564:
but the orange potassium salt can be dehydrated to form a
457:
and forms yellow crystals that decompose at 212 °C.
453:
atoms. It is sensitive to light, soluble in water and
732:, which formally contains both one croconate dianion
603:where the hydrogen atom of the hydroxyl group is
973:Elements of Chemistry: Theoretical and Practical
194:
548:means this is an aromatic configuration). The
106:
843:(purple). These complexes all have the same
623:in 1825, who named the compounds from Greek
580:crystallize in the anhydrous form. Salts of
445:groups adjacent to the double bond and three
272:InChI=1S/C5H2O5/c6-1-2(7)4(9)5(10)3(1)8/h6-7H
8:
1001:
999:
684:it has a large dipole moment of 9–10
247:
172:
150:
22:
946:Bulletin of the Chemical Society of Japan
214:
76:4,5-Dihydroxycyclopent-4-ene-1,2,3-trione
1272:Journal of the American Chemical Society
939:
937:
935:
933:
810:
806:
771:research because of their potential for
751:
735:
723:
719:
715:
711:
707:
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668:
664:
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640:
636:
527:
508:
433:
429:
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414:
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1260:
1258:
1147:Angewandte Chemie International Edition
1105:
1103:
1101:
1099:
1097:
1095:
929:
293:
268:
243:
1178:
1176:
1058:
1056:
163:
748:and one hydrogencroconate monoanion (
560:croconates crystallize from water as
460:The compound is acidic and loses the
275:Key: RBSLJAJQOVYTRQ-UHFFFAOYSA-N
7:
185:
653:was determined by Dunitz in 2001.
14:
1391:
29:
397:4,5-dihydroxycyclopentenetrione
377:(at 25 °C , 100 kPa).
1112:Chemistry – A European Journal
1086:10.1016/j.molstruc.2006.01.035
1066:Journal of Molecular Structure
498:at 25 °C). The resulting
1:
1035:Journal of Physical Chemistry
1008:Journal of Physical Chemistry
592:, and others are also known.
1355:Crystal Growth & Design
38:
1445:
1339:10.1016/j.poly.2006.09.100
823:(yielding a brown solid),
787:The croconate anion forms
625:
15:
1311:10.1016/j.ica.2008.12.002
1249:10.1016/j.ica.2009.09.050
975:(4th ed.). Longmans.
595:Croconic acid also forms
371:
304:
284:
259:
90:
82:
70:
65:
37:
28:
769:supramolecular chemistry
449:groups on the remaining
16:Not to be confused with
1299:Inorganica Chimica Acta
1237:Inorganica Chimica Acta
803:, with general formula
971:Miller, W. A. (1868).
863:
793:coordination compounds
296:O=C1C(O)=C(O)C(=O)C1=O
56:
47:
990:Elements of Chemistry
861:
819:; where M stands for
55:
46:
1400:at Wikimedia Commons
568:. The croconates of
339:142.07
72:Preferred IUPAC name
1284:10.1021/ja00900a013
1205:10.1038/nature08731
1197:2010Natur.463..789H
1078:2006JMoSt.794...63G
1047:10.1021/j100528a010
1020:10.1021/j100588a009
958:10.1246/bcsj.31.543
917:Cyclopentanepentone
876:sandwich-type bonds
25:
864:
601:dimethyl croconate
441:backbone with two
381:Infobox references
57:
48:
23:
1396:Media related to
1367:10.1021/cg800827a
1041:(13): 1268–1274.
1014:(21): 2246–2251.
862:Croconate dianion
839:(dark green), or
801:transition metals
676:held together by
504:hydrogencroconate
409:chemical compound
389:Chemical compound
387:
386:
228:CompTox Dashboard
132:Interactive image
61:
60:
1436:
1395:
1379:
1378:
1361:(2): 1013–1019.
1353:Architectures".
1349:
1343:
1342:
1333:(5): 1105–1112.
1321:
1315:
1314:
1305:(8): 2636–2642.
1294:
1288:
1287:
1266:
1253:
1252:
1231:
1225:
1224:
1191:(7282): 789–92.
1180:
1171:
1170:
1153:(9): 1779–1780.
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1136:
1135:
1118:(8): 1804–1812.
1107:
1090:
1089:
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1024:
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892:Croconate violet
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312:Chemical formula
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39:
33:
26:
1444:
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1403:
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1322:
1318:
1296:
1295:
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1268:
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1256:
1233:
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1182:
1181:
1174:
1144:
1143:
1139:
1109:
1108:
1093:
1062:
1061:
1054:
1032:
1031:
1027:
1005:
1004:
997:
985:
984:
980:
970:
969:
965:
943:
942:
931:
926:
919:(leuconic acid)
902:Rhodizonic acid
888:
827:(dark purple),
816:
812:
808:
804:
759:
756:
755:
753:
749:
743:
740:
739:
737:
733:
729:
725:
721:
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713:
709:
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674:
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659:
650:
646:
642:
638:
634:
617:
535:
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531:
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506:
493:
491:
489:
478:
476:
474:
435:
431:
427:
424:
420:
416:
412:
405:pentagonic acid
395:(also known as
390:
383:
378:
363:
328:
324:
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292:
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280:
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113:
100:
86:
78:
77:
21:
12:
11:
5:
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1386:External links
1384:
1381:
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1344:
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1289:
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1172:
1137:
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1072:(1–3): 63–70.
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952:(5): 543–549.
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927:
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921:
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897:Croconate blue
894:
887:
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814:
795:with divalent
727:
678:hydrogen bonds
658:
655:
648:
621:Leopold Gmelin
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375:standard state
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1441:
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1429:Organic acids
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1425:
1422:
1420:
1417:
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1414:Cyclopentenes
1412:
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1399:
1398:Croconic acid
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869:
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834:
830:
826:
822:
802:
798:
794:
790:
785:
782:
776:
774:
770:
765:
703:
700:In the solid
698:
695:
691:
690:ferroelectric
687:
683:
679:
656:
654:
632:
622:
614:
612:
610:
606:
602:
598:
593:
591:
587:
583:
579:
575:
571:
567:
563:
559:
555:
551:
547:
546:Hückel's rule
543:
524:
505:
501:
486:
471:
467:
463:
458:
456:
452:
448:
444:
440:
411:with formula
410:
406:
402:
398:
394:
393:Croconic acid
382:
376:
370:
366:
360:
356:
353:
352:
348:
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345:Melting point
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164:ECHA InfoCard
161:
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128:
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117:
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109:
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73:
69:
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50:
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41:
40:
36:
32:
27:
19:
18:Crocinic acid
1358:
1354:
1347:
1330:
1326:
1319:
1302:
1298:
1292:
1278:(17): 2586.
1275:
1271:
1243:(1): 49–56.
1240:
1236:
1229:
1188:
1184:
1150:
1146:
1140:
1115:
1111:
1069:
1065:
1038:
1034:
1028:
1011:
1007:
989:
981:
972:
966:
949:
945:
907:Squaric acid
865:
845:orthorhombic
791:crystalline
786:
777:
766:
702:alkali metal
699:
660:
618:
594:
522:
503:
484:
469:
459:
439:cyclopentene
404:
400:
396:
392:
391:
358:
91:Identifiers
83:Other names
912:Deltic acid
694:Curie point
605:substituted
566:monohydrate
437:. It has a
401:crocic acid
367:0.80, 2.24
305:Properties
170:100.201.686
85:Crocic acid
1419:Triketones
1408:Categories
1327:Polyhedron
987:Turner, E.
924:References
870:(yellow),
831:(yellow),
773:π-stacking
562:dihydrates
335:Molar mass
216:6HGY35UXAA
143:ChemSpider
119:3D model (
98:CAS Number
1375:1528-7483
1221:205219520
880:ferrocene
868:aluminium
837:manganese
835:(green),
813:)·3H
726:)·2H
657:Structure
629:meaning "
558:potassium
523:croconate
468:groups (p
464:from the
1424:Enediols
1213:20148035
1167:11353510
1132:11933108
886:See also
872:chromium
789:hydrated
647:·2H
607:with an
599:such as
574:rubidium
570:ammonium
542:aromatic
490: =
475: =
466:hydroxyl
443:hydroxyl
108:488-86-8
1193:Bibcode
1074:Bibcode
853:Calcium
797:cations
692:with a
682:dioxane
615:History
611:group.
578:caesium
550:lithium
462:protons
455:ethanol
407:) is a
355:Acidity
329:
183:PubChem
1373:
1219:
1211:
1185:Nature
1165:
1130:
849:oxygen
841:cobalt
833:nickel
821:copper
631:crocus
626:κρόκος
597:ethers
590:silver
582:barium
554:sodium
500:anions
451:carbon
447:ketone
289:SMILES
196:546874
152:476003
66:Names
1217:S2CID
680:. In
609:alkyl
483:and p
432:(COH)
428:(C=O)
264:InChI
121:JSmol
1371:ISSN
1209:PMID
1163:PMID
1128:PMID
829:zinc
825:iron
586:lead
576:and
556:and
521:and
496:0.01
492:2.24
481:0.08
477:0.80
207:UNII
1363:doi
1335:doi
1307:doi
1303:362
1280:doi
1245:doi
1241:363
1201:doi
1189:463
1155:doi
1120:doi
1082:doi
1070:794
1043:doi
1016:doi
954:doi
805:M(C
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