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Selenium-gold interaction plays an important role in crystal materials, molecular self-assembly, and pharmacochemistry involving gold. In this paper, we unveiled the mechanism and nature of selenium-gold interaction by studying complexes F2CSe...AuY (Y = CN, F, Cl, Br, OH, and CH3). The results showed that the formation of selenium-gold interaction is mainly attributed to the charge transfer from the lone pair of Se atom to the Au--Y anti-bonding orbital. Energy decomposition analysis indicated that the polarization energy is nearly equivalent to or exceeds the electrostatic term in the selenium-gold interaction. Interestingly, the chalcogen-gold interaction becomes stronger with the increase of chalcogen atomic mass in F2CX...AuCN (X = O, S, Se, and Te). The cyclic ternary complexes are formed with the introduction of NH3 into F2CSe...AuY, in which selenium-gold interaction is weakened and selenium-nitrogen interaction is strengthened due to the synergistic effects. [ABSTRACT FROM AUTHOR]

The three structures of rare gas inserted fluorohydrides HRgF (Rg=He, Ar, and Kr) with all real frequencies are obtained at the QCISD(T)/aug-cc-pVTZ level. The static first hyperpolarizabilities (β0) at the QCISD/aug-cc-pVQZ level are 8 a.u. (HF), 384 a.u. (HHeF), 737 a.u. (HArF), and 465 a.u. (HKrF). The β0 value remarkably increases by about 50–90 times from 8 a.u. (HF) to 384–737 a.u. (HRgF) due to the inserted rare gas (Rg). The Rg atomic number dependence of β0 for HRgF (Rg=He, Ar, and Kr) is found at the first time. The order of β0 is unmonotonic to be HHeFHKrF, but not monotonic (HHeF0 relates to both the geometric effect (expanded H...F distance by Rg) and the electronic effect of Rg. From HHeF to HArF and from HArF to HKrF, the preponderant effect on β0 is variational. From HHeF to HArF, the geometric effect is preponderant and the β0 value increases; from HArF to HKrF, the electronic effect of Rg is preponderant and the β0 value decreases. Thus, the rare gas atomic number dependence of β0 is unmonotonic. Furthermore, as the order of β0 is consistent with that of the difference between the ground and excited-state dipole moments (Δμ), the Δμ may be one mainly controlling factor of β0. The nature of H–Rg bond is also explored that special short H–He bond of 0.811 Å is only a half single bond due to its Wiberg bond index of 0.51, while the long H–Ar and H–Kr bonds are almost single bond with the Wiberg bond index of about 0.8. [ABSTRACT FROM AUTHOR]