Epitaxial Retrieval of a Disappearing Polymorph

Area of Science:

• Coordination Chemistry
• Crystallography
• Materials Science

Background:

• Polymorphism, the ability of a solid material to exist in more than one crystal form, is crucial in materials science.
• Understanding polymorph behavior is essential for controlling material properties and ensuring reproducibility in synthesis.

Purpose of the Study:

• To investigate the crystallization behavior and identify different solid phases of palladium and platinum complexes containing the 1-oxa-4,7-dithiacyclononane ligand.
• To characterize the observed polymorphs and explore the phenomenon of a 'disappearing polymorph'.

Main Methods:

• Recrystallization of [PdCl2([9]aneS2O)] and [PtCl2([9]aneS2O)] complexes via diethyl ether vapor diffusion into nitromethane solutions.
• Crystallization under varying temperatures and seeding techniques to isolate and stabilize different crystal phases.
• X-ray crystallography to confirm isomorphism and isostructural relationships between phases and complexes.

Main Results:

• Three distinct crystalline phases (α, β, γ) were identified for [PdCl2([9]aneS2O)], with the β phase exhibiting characteristics of a 'disappearing polymorph'.
• Two crystalline phases (α, β) were isolated for [PtCl2([9]aneS2O)], which were isomorphous and isostructural with the corresponding α-1 and β-1 phases.
• The β-2 phase of the platinum complex was successfully used to seed the growth of the disappearing β-1 phase of the palladium complex.

Conclusions:

• The study demonstrates the complex polymorphic behavior of [PdCl2([9]aneS2O)], highlighting the transient nature of the β-1 phase.
• The isostructural relationship between the platinum and palladium complexes provided a method to stabilize and study the disappearing polymorph.
• This research offers insights into controlling crystallization and understanding phase transitions in coordination complexes.