title: The structure of alkali metal derivatives of azoles: N-sigma versus pi structures.
abstract: High level ab initio calculations have been used to study the relative stability of N-sigma and pi configurations of the neutral alkaline derivatives of azoles. The N-sigma structure is the one normally expected for nonionized azolate salts. However, the results show that in the case of the pyrrole and imidazole the pi configuration is more stable than the N-sigma one. The preference of the N-sigma vs pi configurations is related to the presence or the absence of two contiguous nitrogen atoms in the azole ring. A search in the CSD shows that some pyrrolate and imidazolate salts exist in solid phase in the pi configuration.
authors.affiliation: Instituto de Química Médica (CSIC), Juan de la Cierva, 3, 28006-Madrid, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Blanco
authors.forename: Ibon
authors.initials: I
authors.lastname: Alkorta
authors.forename: Jose
authors.initials: J
authors.lastname: Elguero
mesh_terms: D001393:Azoles / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D008672:Metals, Alkali / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry; D011789:Quantum Theory; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D001393:Azoles; D007093:Imidazoles; D008672:Metals, Alkali; D011758:Pyrroles; D009584:Nitrogen