Structural Transformations of Amino-Acid-Based Polymers: Syntheses and Structural Characterization.

Area of Science:

• Coordination chemistry
• Materials science
• Crystallography

Background:

• Amino acid-based coordination polymers offer tunable properties.
• Understanding structural transformations is key to designing functional materials.
• Zinc(II) complexes are versatile building blocks in coordination chemistry.

Purpose of the Study:

• To synthesize and characterize discrete zinc complexes and coordination polymers.
• To investigate the temperature-driven structural transformation of a discrete zinc complex.
• To elucidate the formation pathways and structures of 1D and 2D coordination polymers derived from l-thioproline.

Main Methods:

• Synthesis and characterization of coordination compounds.
• Powder X-ray diffraction (PXRD) for structural analysis.
• In-situ synchrotron PXRD experiments and simulation studies.

Main Results:

• A discrete complex [Zn(tpro)₂(H₂O)₂] (1) was synthesized.
• Complex 1 transforms into a 1D helical coordination polymer [Zn(tpro)₂]n (2) upon heating.
• A 2D layered structure [Zn(tpro)₂]n (3) with a (4,4) topology was also formed, linked via hydrogen bonding into a 3D network.
• In-situ PXRD confirmed the conversion of 1 to 2 and 3, with their ratio determined by simulation.

Conclusions:

• The 0D discrete zinc complex exhibits temperature-driven structural transformation capabilities.
• Heating facilitates the conversion of the discrete complex into 1D and/or 2D amino acid-based coordination polymers.
• This work demonstrates a pathway for generating diverse coordination polymer architectures from a single precursor complex.