Group 12 dihalides: structural predilections from gases to solids.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Solid-State Chemistry

Background:

• Group 12 dihalides (MX(2): M=Zn, Cd, Hg; X=F, Cl, Br, I) exhibit diverse structural behaviors.
• Understanding structure-property relationships is crucial for predicting material characteristics.

Purpose of the Study:

• To investigate the connections between Group 12 dihalide structures in vapor and crystal phases.
• To analyze the influence of relativistic effects on molecular geometry.
• To compare structural trends across different Group 12 metals and halogens.

Main Methods:

• Density functional theory (B3PW91) and Møller-Plesset perturbation theory (MP2) were employed for molecular structure calculations.
• Analysis of monomer, dimer, and crystal structures was performed.
• Frontier orbital interactions were considered to explain observed geometries.

Main Results:

• All monomers are linear; mercury dihalides exhibit shorter bonds due to relativistic effects.
• Zinc and cadmium dihalide dimers adopt D(2h) symmetry, while mercury dihalide dimers show a looser C(2h) structure.
• Group 12 dihalide crystals range from extended solids to molecular structures, reflecting monomer and dimer characteristics.

Conclusions:

• A clear link exists between the structures of Group 12 dihalide monomers, dimers, and their resulting crystal forms.
• Relativistic effects significantly impact mercury dihalide properties.
• Structural comparisons with Group 2 dihalides highlight unique trends in Group 12.