title: ESI-MS detection of very weak pi-stacking interactions in the mixed-ligand sandwich complexes formed by substituted benzo-crown ethers and metal cations.
abstract: The stability of the mixed-ligand complex formed by amino-benzo-15-crown-5 and nitro-benzo-15-crown-5, with a metal cation, [NH(2)B15C5 + NO(2)B15C5 + K](+), was found to be enhanced by pi-stacking interactions. This conclusion was deduced by comparison of the abundance of the mixed-ligand complex with the abundances of homo-ligand complexes ([(NH(2)B15C5)(2) + K](+), [(NO(2)B15C5)(2) + K](+)), as well as with those of 1:1 complexes ([NH(2)B15C5 + K](+), [NO(2)B15C5 + K](+)). Some solvents and some metal cations with large radii were also found to prevent the existence of pi-stacking interactions.
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, Poznań, Poland. franski@amu.edu.pl
authors.forename: Rafał
authors.initials: R
authors.lastname: Frański
authors.forename: Błazej
authors.initials: B
authors.lastname: Gierczyk
mesh_terms: D002412:Cations; D043844:Crown Ethers / Q000737:chemistry*; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002412:Cations; D043844:Crown Ethers; D008024:Ligands; D008670:Metals