Neutral alkaline-metal and alkaline-earth-metal derivatives of imidazole and benzimidazole.
A theoretical study of the minima and connecting transition states of the neutral complexes formed by alkaline-metal and alkaline-earth-metal derivatives of imidazolate and benzimidazolate anions has been carried out using B3LYP/6-31+G(d,p), B3LYP/6-311+G(3df,2p), and G3B3 methods. Two and three nondegenerated minima and two and four TS structures have been identified for imidazole and benzimidazole derivatives, respectively. The most stable minima of the alkaline-metal derivatives of both systems correspond to the metal interacting with the imidazole ring, whereas in the alkaline-earth-metal derivatives, the preferred minima depend on the substituent. A remarkable feature of some minima is the fact that some of the metal-aromatic interactions follow the classical π-cation pattern, even though the global structure corresponds to a neutral salt, constituting a class of noncovalent interaction of great interest in the chemistry of aromatic and heterocyclic complexes. A CSD search has confirmed that the two bonding modes, N-σ and π, are present in the solid phase. The π mode has been analyzed by comparison with other azoles.
Molecular Design Group, School of Biochemistry and Immunology, University of Dublin, Trinity College , Dublin 2, Ireland.
Fernando
F
Blanco
David G
DG
Lloyd
Ibon
I
Alkorta
José
J
Elguero
D001562:Benzimidazoles / Q000737:chemistry*; D002413:Cations, Divalent; D002414:Cations, Monovalent; D007093:Imidazoles / Q000737:chemistry*; D008672:Metals, Alkali / Q000737:chemistry*; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013816:Thermodynamics
D001562:Benzimidazoles; D002413:Cations, Divalent; D002414:Cations, Monovalent; D007093:Imidazoles; D008672:Metals, Alkali; D008673:Metals, Alkaline Earth; C029899:imidazole; C031000:benzimidazole