Silicon Forms a Rich Diversity of Aliphatic Polyol Complexes in Aqueous Solution

Area of Science:

• Inorganic Chemistry
• Supramolecular Chemistry
• Biochemistry

Background:

• Silicon (Si) complexation in aqueous solutions is crucial for biological and geochemical processes.
• Previous understanding suggested a requirement for specific hydroxyl group arrangements (threo) for hypercoordinate Si complex formation.

Purpose of the Study:

• To investigate aqueous silicon complexation by alditols and aldonic acids.
• To elucidate the structural diversity and formation conditions of hypercoordinate silicon species.

Main Methods:

• High-sensitivity 29Si Nuclear Magnetic Resonance (NMR) spectroscopy utilizing isotopically enriched solutions.
• Computational theoretical modeling to analyze complex structures and interactions.

Main Results:

• Established that aliphatic polyols do not require a threo hydroxyl group arrangement to form hypercoordinate Si complexes.
• Identified thirteen distinct molecular assemblages with 4-, 5-, or 6-coordinate Si centers.
• Detected significant concentrations of 5-coordinate Si bis-ligand complexes under biologically relevant conditions.

Conclusions:

• The formation of hypercoordinate silicon complexes is more versatile than previously thought.
• The presence of a threo group enhances formation constants but is not essential for complexation.
• Diverse silicon coordination environments exist in aqueous solutions with polyols, including biologically relevant ones.