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Infrared spectra in the mid-infrared region of highly unsaturated Fe+-hydrocarbon complexes isolated in the gas phase are presented. The infrared spectroscopy is a very powerful tool to characterize selectivity prepared molecular ions using a Fourier transform ion cycloton mass spectometer.

We have employed atomic force microscope-based infrared spectroscopy (AFM-IR) to spatially map energy storage polymers inside individual bacteria Rhodobacter capsulatus. AFM-IR allows chemical mapping of sub-cellular features with a spatial resolution of <100 nm. We have used key absorption bands of the energy storage polymer polyhydroxybutyrate (PHB) known from FTIR to spatially map the molecular distribution of PHB inside bacteria. We have also compared FTIR measurements on bulk PHB with AFM-IR measurements of PHB inside bacteria. We observe a shift in the location of the carbonyl absorption peak between bulk PHB and PHB inside bacteria. We have also used finite element analysis to model AFM-IR measurements of PHB granules, allowing for estimation of the real size of the granules. We have also performed transmission electron microscopy (TEM) of R. capsulatusto determine the size distribution of the PHB granules. Sizes measured by AFM-IR correspond well to TEM measurements. [ABSTRACT FROM AUTHOR]

Infrared spectra in the mid-infrared region (800-1600 cm-1) of highly unsaturated Fe+-hydrocarbon complexes isolated in the gas phase are presented. These organometallic complexes were selectively prepared by ion-molecule reactions in a Fourier transform ion cycloton mass spectrometer (FTICR-MS). The infrared multiphoton dissociation (IRMPD) technique has been employed using the free electron laser facility CLIO (Orsay, France) to record the infrared spectra of the mass selected complexes. The experimental IRMPD spectra present the main features of the corresponding IR absorption spectra calculated ab initio. As predicted by these calculations, the experimental spectra of three selectively prepared isomers of Fe+(butene) present differences in the 800-1100 cm-1 range. On the basis of the comparison with calculated IR spectra, the IRMPD spectrum of Fe(butadiene)+ suggests that the ligand presents the s-trans isomeric form. This study further confirms the potentialities of IRMPD spectroscopy for the structural characterization of organometallic ionic highly reactive intermediates in the gas phase. In conjunction with soft ionization techniques such as electrospray, this opens the door to the gas-phase characterization of reactive intermediates associated with condensed phase catalysts. [ABSTRACT FROM AUTHOR]

Dinuclear gold(III) clusters with a rhombic Au2O2 core and 2,2′-bipyridyl ligands substituted in the 6-position (bipyR) are examined by tandem mass spectrometry. Electrospray ionization of the hexafluorophosphate salts affords the complexes [(bipyR)Au(μ-O)2Au(bipyR)]2+ as free dications in the gas phase. The fragmentation behavior of the mass-selected dications is probed by means of collision-induced dissociation experiments which reveal an exceptionally pronounced effect of substitution. Thus, for the parent compound with R = H, i.e., [(bipy)Au(μ-O)2Au(bipy)]2+, fragmentation at the dicationic stage prevails to result in a loss of neutral H2O concomitant with an assumed rollover cyclometalation of the bipyridine ligands. In marked contrast, all complexes with alkyl substituents in the 6-position of the ligands (bipyR with R = CH3, CH(CH3)2, CH2C(CH3)3, and 2,6-C6H3(CH3)2) as well as the corresponding complex with 6,6′-dimethyl-2,2′-dipyridyl as a ligand exclusively undergo Coulomb explosion to produce two monocationic fragments. It is proposed that the additional steric strain introduced to the central Au2O2 core by the substituents on the bipyridine ligand, in conjunction with the presence of oxidizable C-H bonds in the substituents, crucially affects the subtle balance between dication dissociation under maintenance of the 2-fold charge and Coulomb explosion into two singly charged fragments. [ABSTRACT FROM AUTHOR]

First example of coupling a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer (FTICR-MS) with an infrared Free Electron Laser (FEL) is presented. This experimental setup is ideally suited for the direct structural characterization of reactive polyatomic ions. Ultrasensitive measurements of the infrared vibrational spectrum of ionic reactive intermediate selectively prepared is allowed by the association of the high peak power of the FEL, its wide tunability, and the flexibility of FTICR-MS, where several mass selections and ion-molecule reactions can be combined. These possibilities are demonstrated in the case of Fe+ complexes where two photofragmentation pathways compete. The resulting infrared spectrum is in excellent agreement, both with respect to the position and to the relative intensities of the infrared transitions, with predicted by ab initio electronic structure calculations. [Copyright &y& Elsevier]