Exploring the Tl 2 H 2 potential energy surface: A comparative analysis with group 13 systems and experiment

Thallium chemistry is experiencing unprecedented importance. Therefore, it is valuable to characterize some of the simplest thallium compounds. Stationary points along the singlet and triplet Tl  2 H  2 potential energy surface have been characterized. Stationary point geometries were optimized with the CCSD(T)/aug-cc-pwCVQZ-PP method. Harmonic vibrational frequencies were computed at the same level of theory while anharmonic vibrational frequencies were computed at the CCSD(T)/aug-cc-pwCVTZ-PP level of theory. Final energetics were obtained with the CCSDT(Q) method. Basis sets up to augmented quintuple-zeta cardinality (aug-cc-pwCV5Z-PP) were employed to obtain energetics in order to extrapolate to the complete basis set limits using the focal point approach. Zero-point vibrational energy corrections were appended to the extrapolated energies in order to determine relative energies at 0 K. It was found that the planar dibridged isomer lies lowest in energy while the linear structure lies highest in energy. The results were compared to other group 13 M  2 H  2 (M = B, Al, Ga, In, and Tl) theoretical studies and some interesting variations are found. With respect to experiment, incompatibilities exist.

The Role of Prussian Blue-Thallium and Potassium Similarities and Differences in Crystal Structures of Selected Cyanido Complexes of W, Fe and Mo

The synthesis and single X-ray crystal structures of Tl2[W(CN)6(bpy)]·H2O, Tl[W(CN)6(bpy)], Tl57[{Fe(CN)6}12{NO3}9]·9H2O, Tl4[W(CN)8] and Tl4[Mo(CN)8] are described. Salts crystalize in the monoclinic or trigonal (Fe) space group. For all complexes, the very unusual “side-on” coordination of Tl to C and N of cyanido ligands is observed and compared to potassium cations. The very strong bonding to cyanido ligands with an 8–13 coordination number of thallium is described and discussed. The difference between potassium and thallium bonding is an indication of the biological activity of thallium and the role of Prussian blue in the thallium detoxification procedure.

Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.