ISSN:
0941-1216
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
5-Ring-Cycloamidines - Deeply Colored Heterocycles with Unusual Properties. II. Molecular- and Electronic StructureThe crystal and molecular structure of two N,N′-aryl-5-amino-imidazole-4-imides were detected by X-ray analysis. The structural parameters are discussed in conjunction with theoretical data obtained by density functional and ab initio quantum theory. The interpretation of the molecular structures derived from the X-ray diffraction study is made more difficult by statistic disorder or by enclosure of water in the crystal. The theory predicts a planar 5-amino-imidazole-4-imide parent structure with an energy barrier to H-transfer of about 25 kcal/mol (DFT RB3LYP/6-311+G** and ab initio G2(MP2) calculations). The CC bond of the five-membered ring is exceedingly long. CC-bond length elongation is also reported for oxalbisamidine. The structure of the parent compound is discussed in terms of polymethinic and antiaromatic substructures. Weinholds's Natural Bond Orbital (NBO) scheme and Natural Resonance Theory (NRT) as well as Schleyer's criterion of the Nucleus Independent Chemical Shift (NICS) is consulted to reveal the very nature of the unique bond system.
Additional Material:
2 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prac.199733901133
