title: Gas-phase and solution studies of three resorcin[4]arene derivatives using electrospray time-of-flight mass spectrometry.
abstract: Electrospray ionisation mass spectrometry (ESI-MS) has been used to study the relative gas-phase proton and alkali metal (Li, Na, K and Cs) binding affinities of three different resorcin[4]arenes using the kinetic method. Collision-induced dissociation (CID) was used to study the fragmentation of resorcin[4]arene heterodimer sandwich complexes, allowing the relative binding affinity order to be established. All the alkali metal cations have the same gas-phase binding affinity order with the resorcin[4]arene host molecules. At collision energies of > or = 13eV, one of the [resorcin[4]arene+Metal]+, (Metal = Li, Na, K) ions fragmented through break-up of the resorcin[4]arene, whilst the other host resorcin[4]arene remained intact, causing an apparent change in binding affinity at high collision energy. This effect was not observed with caesium, since all complex ions dissociated readily under CID by displacement of the caesium cation. The binding affinity for the protonated resorcin[4]arenes was found to be different from the alkali metal cation binding affinity because of the higher proton affinity of the nitrogen-containing resorcin[4]arenes. It is shown that resorcin[4]arenes containing an oxazine ring can be converted into a ring-opened derivative via an Eschweiler-CLarke reaction in the presence of formic acid. A second ring-opening process also occurs, including a hydrolysis reaction that results in apparent Losses of 12 mass units from the intact resorcin[4]arene. Both these reactions occur in solution before mass spectrometric investigation and cannot be achieved by CID. This observation was confirmed by inducing the Eschweiter-CLarke reaction in a model benzoxazine compound.
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK. j.c.reynolds@lboro.ac.uk
authors.forename: James C
authors.initials: JC
authors.lastname: Reynolds
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Mei Q
authors.initials: MQ
authors.lastname: Chew
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Helen J
authors.initials: HJ
authors.lastname: Martin
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Emma C
authors.initials: EC
authors.lastname: Stubbs
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Marguerite A
authors.initials: MA
authors.lastname: Waters
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Crotty
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Silvestre-Gonzalez
authors.affiliation: School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Chan
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: C L Paul
authors.initials: CL
authors.lastname: Thomas
authors.affiliation: School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, UK.
authors.forename: Philip C Bulman
authors.initials: PC
authors.lastname: Page
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Colin S
authors.initials: CS
authors.lastname: Creaser
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Harry
authors.initials: H
authors.lastname: Heaney
mesh_terms: D001665:Binding Sites; D047250:Calixarenes / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D007700:Kinetics; D008672:Metals, Alkali / Q000737:chemistry*; D010078:Oxazines / Q000737:chemistry; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D011522:Protons; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D056831:Coordination Complexes; D005740:Gases; D008672:Metals, Alkali; D010078:Oxazines; D011522:Protons; D012996:Solutions; C466160:resorcinarene; D047250:Calixarenes; D010649:Phenylalanine