Secondary coordination sphere controlled reversible geometry reorganisations in copper(II) complexes

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Crystallography

Background:

• Copper(II) complexes exhibit diverse coordination geometries.
• Ligand design influences the structural and electronic properties of metal complexes.
• Fluoride ligands can stabilize unusual coordination numbers in metal complexes.

Purpose of the Study:

• To investigate the structural dynamics of copper(II) fluoride complexes with cis-3,5-diamino-trans-hydroxycyclohexane (cis,trans-DAHC).
• To explore the influence of solvent (water) concentration on the coordination geometry and crystal structure.
• To demonstrate reversible geometry reorganizations in metal-organic frameworks.

Main Methods:

• Synthesis of cis,trans-DAHC copper(II) fluoride complexes.
• Single-crystal X-ray diffraction to determine crystal structures.
• Solution-based experiments to control water concentration and observe phase transitions.

Main Results:

• Demonstration of reversible geometry reorganizations in copper(II) fluoride complexes.
• Identification of two distinct crystal forms: blue 5-coordinate syn-[Cu(DAHC)(2)F](F).2CH(3)OH.H(2)O and red 4-coordinate anti-[Cu(DAHC)(2)](F)(2).2H(2)O.
• Correlation between water concentration in the mother liquor and the interconversion between the two crystal forms.

Conclusions:

• The water concentration is a critical factor controlling the coordination geometry and crystal packing of cis,trans-DAHC copper(II) fluoride complexes.
• Reversible structural transformations can be achieved by simple manipulation of solvent conditions.
• This study provides insights into stimuli-responsive materials based on coordination complexes.