Data mining algorithms have been used to analyze the infrared multiple photon dissociation (IRMPD) patterns of gas-phase lithiated disaccharide isomers irradiated with either a line-tunable CO(2) laser or a free electron laser (FEL). The IR fragmentation patterns over the wavelength range of 9.2-10.6 μm have been shown in earlier work to correlate uniquely with the asymmetry at the anomeric carbon in each disaccharide. Application of data mining approaches for data analysis allowed unambiguous determination of the anomeric carbon configurations for each disaccharide isomer pair using fragmentation data at a single wavelength. In addition, the linkage positions were easily assigned. This combination of wavelength-selective IRMPD and data mining offers a powerful and convenient tool for differentiation of structurally closely related isomers, including those of gas-phase carbohydrate complexes.

The thermal decomposition pathways of the tungsten dimethylhydrazido complexes Cl 4 (RCN)W(NNMe 2 ) (1a: R=CH 3 ; 1b: R=Ph), precursors for single source deposition of WN x C y , were investigated using a combination of experiments and calculations. Raman scattering studies were performed in an impinging-jet, up-flow, aerosol-assisted CVD reactor to identify reaction intermediates. Density Functional Theory calculations (B3LYP/LanL2DZ) were used to estimate Raman active frequencies and explore the reaction surface. Dimethylamine and methylmethyleneimine, products from N-N cleavage of the hydrazido ligand, were observed under deposition conditions and identified by comparison with previously reported Raman shifts and calculated frequencies.

No abstract

A moderate-resolution infrared multiple photon dissociation (IRMPD) spectrum of protonated bis(2-methoxyethyl) ether (diglyme) was obtained using a grating-tuned CO2 laser. The experimental spectrum compares well with one calculated theoretically at the MP2 level and exhibits defined peaks over the span of the CO2 laser output lines as opposed to a relatively featureless spectrum over this wavelength range obtained using free electron laser infrared radiation. The lowest energy structure corresponding to the calculated vibrational spectrum is consistent with structures previously calculated at the same level of theory. Alternative structures were calculated at lower levels of theory for comparison and investigation of the energetics of proton-heteroatom interactions. Broadening of the IRMPD action spectrum due to energetic phenomena characteristic of proton bridges was not observed and thus did not obscure the correlation between theoretical calculations and experimentally determined spectra as it may have in previous studies.