Assembly of 3D coordination polymers from 2D sheets by [2+2] cycloaddition reaction

Area of Science:

• Materials Science
• Coordination Chemistry
• Photochemistry

Background:

• Coordination polymers (CPs) are versatile materials with tunable properties.
• Metal-organic frameworks (MOFs) offer porous structures for various applications.
• Photochemical reactions can be utilized for materials synthesis.

Purpose of the Study:

• To synthesize novel 2D interdigitated Zn(II) coordination polymers (CPs).
• To explore the use of ligands containing C=C bonds in CP synthesis.
• To investigate photochemical and mechanochemical synthesis routes for MOFs.

Main Methods:

• Synthesis of three 2D Zn(II) CPs using monotopic ligands with C=C bonds.
• Photochemical reactions involving 4-styryl pyridine (4spy) and 2'-fluoro-4-styryl pyridine (2F-4spy) ligands.
• Mechanochemical grinding with Zn(OAc)2 as an alternative synthesis method.

Main Results:

• Quantitative formation of cyclobutane rings in CPs synthesized via photochemical reactions.
• Successful mechanochemical synthesis using Zn(OAc)2, contrasting with Zn(NO3)2.
• Formation of different structural units (paddle wheel and tetrahedral) based on ligands (4-vinylpyridine, 4spy, 2F-4spy).
• Photoluminescence properties varied with coordination geometry due to charge-transfer and ligand-centered fluorescence.

Conclusions:

• Photochemical reactions provide a unique route for MOF synthesis via cyclobutane formation.
• Mechanochemistry offers an alternative, solvent-free synthesis pathway for specific Zn(II) CPs.
• Ligand choice dictates the resulting CP structure and coordination geometry.
• Coordination geometry significantly influences the photoluminescence behavior of the synthesized CPs.