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Polymorphism and Thermally Induced Structural Transformation in Semiconducting Cd(II) Coordination Polymers
Ryohei Akiyoshi1, Honoka Motokawa1, Asuka Nishibe1
1Department of Chemistry, School of Science, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo 669-1330, Japan.
Inorganic Chemistry
|September 2, 2025
Summary
Three semiconducting coordination polymer polymorphs were studied. Thermal treatment induced a structural transformation in KGF-79, creating a polar structure with second harmonic generation activity and photoconductivity.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Semiconducting coordination polymers offer tunable electronic and optical properties.
- Polymorphism in [Cd(2-SNPh)2]n, a cadmium(II)-thiolate coordination polymer, influences structural and functional characteristics.
- Understanding structure-property relationships is crucial for developing advanced materials.
Purpose of the Study:
- To investigate the structural diversity and properties of three polymorphs of a cadmium(II)-thiolate coordination polymer, [Cd(2-SNPh)2]n.
- To elucidate the mechanism of thermally induced structural transformation and its impact on material properties.
- To explore the photoconductive behavior and charge transport mechanisms in these materials.
Main Methods:
- Single-crystal X-ray structural analysis to determine the atomic arrangement of KGF-51 and KGF-71.
- Microcrystal electron diffraction analysis to characterize the 1D triple-strand structure of KGF-79.
- Time-resolved microwave conductivity measurements to assess photoconductivity.
- First-principles calculations to understand charge transport mechanisms.
Main Results:
- KGF-51 exhibits a 1D single-strand ladder chain structure.
- KGF-71 displays a 1D double-strand chain structure stabilized by S···S interactions.
- Thermal treatment of KGF-51 and KGF-71 yields KGF-79, a 1D triple-strand chain structure with enhanced S···S interactions.
- KGF-79 shows a transition from nonpolar to polar structure, resulting in second harmonic generation (SHG) activity.
- All three polymorphs demonstrate photoconductivity attributed to charge transport along (-Cd-S-)n chains via hopping.
Conclusions:
- The study reveals three distinct polymorphs of a cadmium(II)-thiolate coordination polymer with varying dimensionality and structural motifs.
- Thermally induced, irreversible transformation leads to a polar structure (KGF-79) with emergent SHG properties.
- The inorganic (-Cd-S-)n chains are key pathways for charge transport, enabling photoconductivity in all polymorphs through a hopping mechanism.
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