ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Copper salts of α,ω-dibasic acids, HOOC—(CH2)n-2—COOH, in which n = 2-10, show (cupric malonate excepted) abnormal magnetic moments, which are lower than the theoretical spin value (1.73 B.M.) for one free electron. (Therefore structures may be expected containing two copper atoms, as there are in cupric acetate monohydrate crystals) in cristalline cupric salts of α-ω-dicarboxylates which show subnormal magnetic moments. A nonplanar structure of oxalic radicals is confirmed experimentally as well by radiostructural analysis as by electron diffraction. These data indicate that cupric oxalate crystals have a dimeric structural network or polymeric molecules containing coordination links and do not behave as isolated molecules with one copper atom or as dimeric molecules, as do the crystals of cupric acetate monohydrate. Analogous network structures are possible for cupric salts of α-ω-dicarboxylic acids having an even number of carbon atoms, although the carbon chains may be bent more or less from their normal configurations; the Cu-Cu links could also be simultaneously changed. Indeed, the magnetic moment of the copper salts of the even series increases with increasing length of carbon chains. For the malonate, the rotation of chains within the central carboxylic groups forbids the formation of such network structures. For the other acids of the odd series the flexibility of the carboxylic groups must take part in bringing two copper atoms together. Indeed, cupric malonate shows a normal magnetic moment as observed for most cupric derivatives, and the effective moment per copper atom in the cupric salts of the odd series decreases with increasing length of carbon chains of the acids until the curve of the magnetic moments of the dibasic acids of the even series practically coalesces with that of the odd series (above pimelic acid). These conclusions, which are based on the magnetic moment data of the polymeric structures of cupric salt crystals of α-ω-dicarboxylic acids, are also confirmed by infrared spectral data, especially by the variations of the C—O stretching and the CH2 rotation bands. Analogous structures are also proposed for the abnormal magnetic moments observed for the cupric salts of rubeanic acid, thioxamide, and similar derivates.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1960.1204815046
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