Mercury mono oxide (HgO) is a well-known solid, which consist of zigzag –O–Hg–O–Hg– chains with linear O–Hg–O units, and is well characterized in solid state. However, gas phase experimental characterization of diatomic HgO is limited. The HgO molecule has been so far identified and characterized by matrix isolation infrared spectroscopy and mass spectrometry. In contrast to less experimental investigation, lots of theoretical quantum computational studies are available on HgO. This is due to the significant role of HgO in the depletion of gaseous elemental mercury in the atmosphere and its subsequent deposition in the Arctic and Antarctic regions after the polar sun rise as well as its correlation with ozone depletion phenomenon. The high temperature mass spectrometric measurements along with the thermodynamic law reported that the dissociation energy of HgO is 53 ± 8 kcal mol . The measured experimental dissociation energy value of the cation contradicts the computed theoretical binding energy (4.0 kcalmol ) of the neutral HgO molecule relative to the ground state of atoms (HgS0 and O P2). [8,9] In addition, the application of relativistic effects to the nonrelativistic calculations destabilizes the molecule further. An accurate ab initio electronic structure calculation by Filatov and Cremer indicate that the dimer of mercury mono oxide (HgO)2 has two isomers: O–Hg2–O and Hg–O2–Hg, and the computed atomization energies of mercury monoxide dimmers are found to be 125 and 128 kcalmol , respectively, which when corrected for zero-point vibrational energies and thermal energies yield atomization energy per monomer of 59.6–60.8 kcal mol , which is in good in agreement with experimental dissociation energy value. Thus, they argued that the dissociation energy determined by the high temperature Knudsen cell mass spectrometry corresponds to the dissociation of (HgO)2 but not because of the dissociation of HgO into Hg and O atoms. Accordingly, the discrepancy in the experimental and calculated dissociation energy value of HgO or (HgO)2 raised question about the existence of intact HgO molecule or its clusters in gas phase. The large difference in electronegativity of χ(Hg) = 1.44 and χ(O) = 3.50 favors ionic bonding with large dipole moment (8.0 D), which allows dipole-dipole interactions between two HgO molecules and thus facilitates the formation of HgO clusters. Tossell systematically explored the structures and stabilities of (HgO)n clusters using quantum chemical methods with different functional and found that the clusters of HgO are more stable for larger n values, and the stability varies when

Solid Mercury Dihydride: Mercurophilic Bonding in Molecular HgH2 Polymers.

Mercury mono oxide cluster ions (HgO)n+ by laser desorption ionization time of flight mass spectrometry.

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Atomic mercury subjected to mercury arc irradiation reacts in solid hydrogen to give the linear HgH(2) molecule with strong IR absorptions at 1902 and 773 cm(-1). Annealing leads to HgH(2) dimer and trimer, and warming above 7 K allows the hydrogen matrix to sublime and solid HgH(2) to form. This covalent molecular solid is characterized by strong IR absorptions at 1802 and 673 cm(-1) and by decomposition at 150-170 K.

Solid Mercury Dihydride: Mercurophilic Bonding in Molecular HgH2 Polymers.

Citations

Mercury mono oxide cluster ions (HgO)n+ by laser desorption ionization time of flight mass spectrometry.

References

Solid mercury dihydride: mercurophilic bonding in molecular HgH(2) polymers

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