Controlling the Formation of Two Concomitant Polymorphs in Hg(II) Coordination Polymers

Area of Science:

• Crystal Engineering
• Coordination Chemistry
• Materials Science

Background:

• Controlling crystalline form is crucial in crystal engineering.
• Polymorphism, arising from different molecular arrangements, presents significant challenges in synthesis and characterization.
• Understanding the factors governing preferential polymorph formation is key to targeted material design.

Purpose of the Study:

• To achieve selective synthesis of two concomitant polymorphs of {[Hg(Pip)2(4,4′-bipy)]·DMF}.
• To investigate the structural differences and stability of the observed polymorphs.
• To correlate structural variations with solid-state photoluminescence properties.

Main Methods:

• Selective synthesis by modifying reaction conditions.
• Characterization using unit cell measurements and decomposition temperature analysis.
• Crystal structure elucidation and Density Functional Theory (DFT) calculations.

Main Results:

• Two polymorphs, P1A and P1B, of {[Hg(Pip)2(4,4′-bipy)]·DMF} were selectively synthesized.
• Structural analysis revealed differences in Hg(II) core arrangements and intermolecular interactions (Hg···π, π···π).
• DFT calculations indicated P1B is more stable than P1A due to enhanced interchain interactions, leading to varied photoluminescence.

Conclusions:

• Selective synthesis of polymorphs is achievable by controlling reaction parameters.
• Polymorphism in this mercury complex is influenced by metal-ligand coordination and non-covalent interactions.
• Structural differences directly impact solid-state photoluminescence, offering avenues for tuning material properties.