Two l-Proline Cadmium Thiocyanates with Moderate Second-Harmonic-Generation Responses and Large Birefringences

Area of Science:

• Inorganic Chemistry
• Materials Science
• Crystallography

Background:

• Organic-inorganic hybrid materials offer tunable properties.
• Cadmium thiocyanates are explored for their unique structural and optical characteristics.
• l-proline serves as a versatile bridging ligand in coordination chemistry.

Purpose of the Study:

• To synthesize and characterize new cadmium thiocyanate compounds incorporating l-proline.
• To investigate the structural diversity and optical properties of the synthesized materials.
• To elucidate the relationship between crystal structure and observed properties.

Main Methods:

• Hydrothermal synthesis of cadmium thiocyanate complexes.
• Single-crystal X-ray diffraction for structural determination.
• Optical spectroscopy and first-principle calculations (DFT) for property analysis.

Main Results:

• Two distinct cadmium thiocyanate structures were obtained: a double-chain-like structure (1) and a layered structure (2).
• Compound 2 shows a significant second-harmonic generation (SHG) response (1.58 × KH2PO4) and large birefringence (0.295).
• Both compounds possess wide band gaps (4.68 eV for 1, 4.59 eV for 2), indicating potential for optical applications.

Conclusions:

• The use of l-proline as a bridging ligand leads to diverse structural motifs in cadmium thiocyanates.
• The synthesized compounds demonstrate notable nonlinear optical properties and wide band gaps.
• First-principle calculations confirm the structure-property correlations, highlighting their potential in optoelectronic devices.