ISSN:
1434-193X
Keywords:
Polymorphism
;
Quinoxalines
;
X-ray analysis
;
Quantum chemical calculations
;
Molecular mechanical calculations
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthesis of 2(1H)-quinoxalinone O-(2′-quinoxalinyl)oxime (3) results in two easily distinguishable crystal forms with different colours, providing a rare example of colour polymorphism. The crystal structures of the two forms have been determined and compared. Intermolecular interactions and light-absorption characteristics of the polymorphs have been analysed by a mixed quantum chemical/molecular mechanical method. In one of the polymorphic forms the crystal field stabilises relatively high energy conformations by enhanced electrostatic interactions. The difference in the light absorption is found to be caused partly by a conformational difference of the molecules. The crystal field increases the difference in the absorption wavelengths and shift them towards higher values.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
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