Metal Complexation Reactions of Quinolone Antibiotics in a Quadrupole Ion Trap

Stereochemical differentiation of five diastereomeric pairs of ␤-amino acids, di-endo-and di-exo-2,3-disubstituted norbornane and norbornene amino acids, cis-and trans-2-aminocyclohexane-, 2-amino-4-cyclohexene-, and 2-aminocyclopentanecarboxylic acids, was investigated via the kinetic method with metal-bound trimeric complexes. This is the first time that diastereomers (di-endo/di-exo and cis/trans) have been differentiated with metal-bound trimeric complexes and the kinetic method. Moreover, determination of diastereochemical excess by the kinetic method was applied to norbornane ␤-amino acids and cyclopentane ␤-amino acids. Experiments showed that a remarkable differentiation of the studied diastereomers was achieved. It was observed that better selectivity values correlated to more rigid structures. The reference compounds for the studied ␤-amino acids varied from ␣-amino acids to some ␤-amino acids. In addition, variation of the metal ion (Cu 2ϩ and Ni 2ϩ ) had some role in the selectivity values obtained. Ab initio and hybrid density functional theory calculations were performed to clarify the results obtained by mass spectrometry. (J Am Soc Mass Spectrom 2009, 20, 34 -41)

Section: Resultsmentioning

confidence: 99%

Diastereochemical differentiation of some cyclic and bicyclic β-amino acids, via the kinetic method

Hyyryläinen

Pakarinen

Fülöp

et al. 2009

“…A number of groups have studied metal complexes by mass spectrometry and found that the fragmentation pathways of analytes can be significantly altered, allowing new opportunities for structural determination [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71]. The Brodbelt group has shown that metal complexation combined with the use of a neutral auxiliary ligand dramatically increases sensitivity for detection of flavonoids while also providing a richer array of fragments to aid in isomer differentiation [50 -52, 72].…”

mentioning

confidence: 99%

Determination of the glycosylation site of flavonoid monoglucosides by metal complexation and tandem mass spectrometry

Davis

Brodbelt

2004

Self Cite

Metal complexation and tandem mass spectrometry were used to differentiate C-and O-bonded flavonoid monoglucoside isomers. Electrospray ionization of solutions containing a flavonoid glycoside and a metal salt led to the generation of the key [M(II) (L) (L-H)] ϩ complexes, where M is the metal ion and L is the flavonoid glycoside. Thirteen flavonoid monoglucosides were examined in combination with Ca(II), Mg(II), Co(II), Ni(II), and Cu(II). Collisional activated dissociation (CAD) of the [M(II) (L) (L-H)] ϩ complexes resulted in diagnostic mass spectra, in contrast to the CAD mass spectra of the protonated, deprotonated, and sodium-cationized flavonoid glucosides. Five common sites of glycosylation could be predicted based on the fragmentation patterns of the flavonoid glucoside/magnesium complexes, while flavonoid glucoside/calcium complexes also were effective for location of the glycosylation site when MS 3 was employed. Cobalt, nickel and copper complexation had only limited success in this application. The metal complexation methods were also applied for characterization of a flavonoid rhamnoside, and the dissociation pathways of the metal complexes indicate that flavonoid rhamnosides have distinctive dissociation features from flavonoid glucosides. (J Am Soc Mass Spectrom 2004, 15, 1287-1299

“…Details about the effect of ligand flexibility and metal type on dissociation pathways has been gathered from these studies. Additional work has also applied CID to other transition metal complexes [15][16][17][18][19][20][21][22][23][24][25][26]. In general, these studies reveal that rearrangement reactions involving the loss of small neutrals from large ligands or the loss of intact ligands from multi-ligated metal ions are typical.…”

mentioning

confidence: 99%

Gas-phase oon-molecule reactions of transition metal complexes: The effect of different coordination spheres on complex reactivity

Combariza

Vachet

2002

Using a modified quadrupole ion trap mass spectrometer, a series of metal complex ions have been reacted with acetonitrile in the gas phase. Careful control of the coordination number and the type of coordinating functionality in diethylenetriamine-substituted ligands enable the effects of the coordination sphere on metal complex reactivity to be examined. The association reaction kinetics of acetonitrile with these pentacoordinate complexes are followed in order to obtain information about the starting complexes and the reaction dynamics. The kinetics and thermodynamics of acetonitrile addition to the metal complex ions are strongly affected by the chemical environment around the metal center such that significant differences in reactivity are observed for Co(II) and Cu(II) complexes with various coordination spheres. When thiophene, furan, or benzene moieties are present in the coordination sphere of the complex, addition of two acetonitrile molecules is readily observed. In contrast, ligands with better donors react mainly to add one acetonitrile molecule. Among the ligands with good donors, a clear trend in reactivity is observed in which complexes with nitrogen-containing ligands are the least reactive, sulfur-containing complexes are more reactive, and oxygen-containing complexes are the most reactive. In general, equilibrium and reaction rate constants seem to be consistent with the hard and soft acid and base (HSAB) principle. Interestingly, the presence of certain groups (e.g., pyridine and imidazole) in the coordination sphere clearly can change the acid character of the metal as seen by their effect on the binding properties of other functional groups in the same ligand. Finally, we conclude that because complexes with different coordination spheres react to noticeably different extents, ion-molecule (I-M) reactions may be potentially useful for obtaining coordination structure information for transition metal complexes. Along with collision-induced dissociation (CID), I-M reactions can also be tools that provide structural information in a mass spectrometric experiment [5][6][7]. I-M reactions are advantageous as structural probes for several reasons. They are highly selective, efficient, and fast. They are also relatively simple, and there are numerous possible combinations of ions and neutrals that can be analytically useful [7][8][9]. Finally, I-M reactions are inherently softer than CID methods, which require "heating up" ions to induce dissociation.CID of metal complexes has been studied by several investigators but mainly in order to determine the binding strengths of ligands to monovalent metals [10]. Studying the dissociation dynamics of metal complex ions from a structural elucidation standpoint, however, has received less attention. Brodbelt and co-workers have studied the dissociation patterns of polyether, crown ether, and polypyridyl complexes of singly- [11,12] and doubly-charged transition metal ions [13,14]. Details about the effect of ligand flexibility and metal type on dissociation...