Document Detail


Potassium cation affinities of matrix assisted laser desorption ionization matrices determined by threshold collision-induced dissociation: application to benzoic acid derivatives.
MedLine Citation:
PMID:  17672435     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
Threshold collision-induced dissociation of K+(xBA) complexes with xenon is studied using guided ion beam mass spectrometry. The xBA ligands studied include benzoic acid and all of the mono- and dihydroxy-substituted benzoic acids: 2-, 3-, and 4-hydroxybenzoic acid and 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, and 3,5-dihydroxybenzoic acid. In all cases, the primary product corresponds to endothermic loss of the intact xBA ligand. The cross section thresholds are interpreted to yield 0 and 298 K bond dissociation energies (BDEs) for K+-xBA after accounting for the effects of multiple ion-neutral collisions, the kinetic and internal energy distributions of the reactants, and dissociation lifetimes. Density functional theory calculations at the B3LYP/6-31G* level of theory are used to determine the structures of the xBA ligands and their complexes with K+. Theoretical BDEs are determined from single-point energy calculations at the B3LYP/6-311+G(2d,2p) and MP2(full)/6-311+G(2d,2p) levels using B3LYP/6-31G* optimized geometries. Four favorable binding modes for the K+(xBA) complexes are found. In all complexes to an xBA ligand that does not have a 2-hydroxyl substituent, the most favorable binding mode corresponds to a single interaction with the carbonyl oxygen atom. Formation of a 4-membered ring via chelation interactions with both oxygen atoms of the carboxylic acid group is found to be the most favorable binding mode for all of the 2-hydroxy-substituted systems except K+(2,3-dihydroxybenzoic acid). In these complexes, a hydrogen-bonding interaction between the hydrogen atom of the carboxylic acid moiety and the oxygen atom of the 2-hydroxy substituent provides additional stabilization. Formation of a 5-membered chelation ring via interaction of K+ with the oxygen atoms of adjacent hydroxyl substituents is also favorable and corresponds to the ground-state geometry for the K+(23DHBA) complex. Formation of a 6-membered chelation ring via interaction of K+ with the carbonyl and 2-hydroxyl oxygen atoms is also quite favorable but does not correspond to the ground-state geometry for any of the systems examined here. The experimental BDEs determined here are in very good agreement with the calculated values.
Authors:
S D M Chinthaka; M T Rodgers
Related Documents :
20452815 - Experimental and theoretical study on molecular structure and ft-ir, raman, nmr spectra...
21880325 - Rheological behaviour and spectroscopic investigations of cerium-modified alo(oh) collo...
16539455 - Modeling of molecular packing and conformation in oligofluorenes.
19787965 - Structure, electronic circular dichroism and raman optical activity in the gas phase an...
9739545 - Dl-3-aminoisobutyric acid monohydrate.
17672825 - Oxidative switches in functioning of mammalian copper chaperone cox17.
Publication Detail:
Type:  Journal Article     Date:  2007-08-02
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  111     ISSN:  1089-5639     ISO Abbreviation:  J Phys Chem A     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-08-16     Completed Date:  2007-10-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8152-62     Citation Subset:  -    
Affiliation:
Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Descriptor/Qualifier:

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


Previous Document:  Evidence against signal enhancement as a mechanism of direct selection by color.
Next Document:  Melting of alloy clusters: effects of aluminum doping on gallium cluster melting.