Ca-, Sr-, and Ba-Coordination polymers based on anthranilic acid via mechanochemistry

Area of Science:

• Coordination Chemistry
• Materials Science
• Solid-State Chemistry

Background:

• Coordination polymers (CPs) offer tunable properties for diverse applications.
• Mechanochemical synthesis provides a solvent-free route to novel materials.
• Understanding structure-property relationships in metal-organic materials is crucial.

Purpose of the Study:

• To synthesize novel Ca-, Sr-, and Ba-based coordination polymers (CPs) using a mechanochemical approach.
• To investigate the influence of cation size on the resulting crystal structures and dimensionality.
• To characterize the synthesized CPs using a comprehensive suite of analytical techniques.

Main Methods:

• Mechanochemical synthesis by milling metal hydroxides with anthranilic acid (oABAH).
• Powder X-ray diffraction (PXRD) with Rietveld refinement for crystal structure determination.
• Extended X-ray absorption fine structure (EXAFS) for local coordination environment analysis.
• Comprehensive characterization including elemental analysis, thermal analysis, MAS NMR, imaging, and dynamic vapor sorption (DVS).

Main Results:

• Three new coordination polymers were synthesized: {[Ca(oABA)2(H2O)3]}n (1), {[Sr(oABA)2(H2O)2]·H2O}n (2), and {[Ba(oABA)2(H2O)]}n (3).
• CP 1 exhibits 1D polymeric chains with a hydrogen-bonding network.
• CP 2 is a 1D CP with bridging water molecules, forming an extended network.
• CP 3 is a 2D CP featuring a bridging water molecule.
• Cation radius directly influences inorganic connectivity and structural dimensionality.
• All compounds showed small surface areas, decreasing upon annealing.
• A reversible phase transformation upon heating was observed only in CP 3.

Conclusions:

• The mechanochemical method is effective for synthesizing diverse metal-based coordination polymers.
• Cation size plays a critical role in dictating the dimensionality and connectivity of the resulting CPs.
• The synthesized CPs exhibit distinct structural features and thermal behaviors, with potential for further investigation.