Ab initio and density functional theory computations have been carried out to calculate the structures and vibrational spectra of halobismuthates and haloantimonates of formulas MX6(3-), M2X10(4-), and M2X9(3-) for M = Bi or Sb and X = I, Br, or Cl. The results have been compared to experimental crystal structures and the infrared and Raman spectra of these species as well as the (MX5(2-))n and (MX4(1-))n anions. Even though the calculations neglect the effect of which cation is present, they do a good job in verifying the observed trends in bond distances and bond stretching vibrational frequencies. External bonds across from bridging bonds are the shortest and have the highest stretching frequencies for all of the ions investigated. This supports the previously postulated "trans effect". Since the calculations were carried out for individual noninteracting anions, the computed results can be expected to best represent the idealized species unperturbed by the effect of the cations present. The trans effect results in shortening of the M-X bonds by 0.08-0.13 Å. It also leads to frequency increases of about 20% for the M-X stretching vibrations.

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Solid-phase microextraction (SPME) coupled to LC for the analysis of five diphenylether herbicides (aclonifen, bifenox, fluoroglycofen-ethyl, oxyfluorfen, and lactofen) is described. Various parameters of extraction of analytes onto the fiber (such as type of fiber, extraction time and temperature, pH, impact of salt and organic solute) and desorption from the fiber in the desorption chamber prior to separation (such as type and composition of desorption solvent, desorption mode, soaking time, and flush-out time) were studied and optimized. Four commercially available SPME fibers were studied. PDMS/divinylbenzene (PDMS/DVB, 60 microm) and carbowax/ templated resin (CW/TPR, 50 microm) fibers were selected due to better extraction efficiencies. Repeatability (RSD, < 7%), correlation coefficient (> 0.994), and detection limit (0.33-1.74 and 0.22-1.94 ng/mL, respectively, for PDMS/DVB and CW/TPR) were investigated. Relative recovery (81-104% for PDMS/DVB and 83-100% for CW/TPR fiber) values have also been calculated. The developed method was successfully applied to the analysis of river water and water collected from a vegetable garden.

The infrared and Raman spectra of 2,6-difluoropyridine (26DFPy) along with ab initio and DFT computations have been used to assign the vibrations of the molecule in its S0 electronic ground state and to calculate its structure. The ultraviolet absorption spectrum showed the electronic transition to the S1(π,π*) state to be at 37,820.2 cm−1. With the aid of ab initio computations the vibrational frequencies for this excited state were also determined. TD-B3LYP and CASSCF computations for the excited states were carried out to calculate the structures for the S1(π,π*) and S2(n,π*) excited states. The CASSCF results predict that the S1(π,π*) state is planar and the S2(n,π*) state has a barrier to planarity of 256 cm−1. The TD-B3LYP computations predict a barrier of 124 cm−1 for the S1(π,π*) states, but the experimental results support the planar structure. Hypothetical models for the ring-puckering potential energy function were calculated for both electronic excited states to show the predicted quantum states. The changes in the vibrational frequencies in the two excited states reflect the weaker π bonding within the pyridine ring.

The infrared and Raman spectra of the bicyclic spiro molecule 2-cyclopenten-1-one ethylene ketal (CEK) have been recorded. Density functional theory (DFT) calculations were used to compute the theoretical spectra, and these agree well with the experimental spectra. The structures and conformational energies for the two pairs of conformational minima, which can be defined in terms of ring-bending (x) and ring-twisting (τ) vibrational coordinates, have also been calculated. Utilizing the results from ab initio MP2/cc-PVTZ computations, a two-dimensional potential energy surface (PES) was calculated. The energy levels and wave functions for this PES were then calculated, and the characteristics of these were analyzed. At lower energies, all of the quantum states are doubly degenerate and correspond to either the lower-energy conformation L or to conformation H, which is 154 cm(-1) higher in energy. At energies above the barrier to interconversion of 264 cm(-1), the wave functions show that the quantum levels have significant probabilities for both conformations.