title: An electrospray ionization tandem mass spectrometric study of p-tert-butylcalix[6]arene complexation with ammonium hydroxide, and ammonium and sodium ions.
abstract: The formation of complexes involving p-tert-butylcalix[6]arene with neutral and charged species has been investigated by tandem mass spectrometry combined with electrospray ionization. Complexes of p-tert-butylcalix[6]arene with NH4+ ions were observed in the ratios 1:1, 2:1, and 3:1, together with the complexes of p-tert-butylcalix[6]arene with NH4OH and Na+ ions in the ratios 1:1:1, 2:1:1, and 3:1:1. A single 1:1 complex of p-tert-butylcalix[6]arene with Na+ ions was observed. In addition, a doubly charged complex of p-tert-butylcalix[6]arene with NH4OH, Na+, and NH4+ ions in the ratio 6:1:1:1 was observed. The identity of each complex was determined by mass analysis of product ions formed by the application of a declustering potential over the range 20-220 V and by observation of product ion mass spectra wherein the collision energy was varied from 5 to 50 eV. Fragmentation of the complexes is characterized by the facile loss of the ammonia molecule, sodium and ammonium ions, loss of neutral p-tert-butylcalix[6]arene, and successive neutral losses of C4H8 from the six tert-butyl groups in each p-tert-butylcalix[6]arene molecule.
authors.affiliation: Instituto de Pesquisas Energéticas e Nucleares, Av. Prof. Lineu Prestes 2242, Cidade Universitária, São Paulo, SP. Zip Code 05508-000, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Sassine
authors.forename: Helio A
authors.initials: HA
authors.lastname: Martins-Júnior
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Lebre
authors.forename: Felipe
authors.initials: F
authors.lastname: Valli
authors.forename: Maria A F
authors.initials: MA
authors.lastname: Pires
authors.forename: Oscar
authors.initials: O
authors.lastname: Vega
authors.forename: Maria C F C
authors.initials: MC
authors.lastname: Felinto
mesh_terms: D064753:Ammonium Hydroxide; D047250:Calixarenes / Q000032:analysis*; D045424:Complex Mixtures / Q000032:analysis; D006878:Hydroxides / Q000032:analysis*; D007477:Ions; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D012964:Sodium / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D045424:Complex Mixtures; D006878:Hydroxides; D007477:Ions; D000644:Quaternary Ammonium Compounds; C519612:p-tert-butylcalix(6)arene p-bromophenylalanine, potassium salt; D047250:Calixarenes; D010649:Phenylalanine; D064753:Ammonium Hydroxide; D012964:Sodium