Water superstructures within organic arrays; hydrogen-bonded water sheets, chains and clusters

Area of Science:

• Supramolecular Chemistry
• Crystal Engineering
• Materials Science

Background:

• Controlling the assembly of water molecules is crucial for developing advanced materials.
• Organic molecules can act as hosts to template water structures.
• 1,4-dihydroquinoxaline-2,3-dione derivatives offer unique structural features for host-guest chemistry.

Purpose of the Study:

• To investigate the use of 1,4-dihydroquinoxaline-2,3-dione derivatives as supramolecular hosts for water molecules.
• To explore the formation of extended water arrays within these host molecules.
• To systematically study the influence of host structure on water organization and hydrogen bonding.

Main Methods:

• Synthesis and crystallization of four 1,4-dihydroquinoxaline-2,3-dione derivatives (qd, mqd, dmqd, Phqd).
• Single-crystal X-ray diffraction analysis of hydrated structures.
• Analysis of hydrogen bonding networks within the crystal lattices.

Main Results:

• Observed formation of zero-, one-, and two-dimensional water arrays templated by the organic hosts.
• The structure of dmqd·6H₂O features a 2D water sheet with pentagonal and octagonal units.
• Phqd·3H₂O forms 1D water chains, while qd and dmqd hydrates show 1D chains or 0D water tetramers.
• Some hydrated structures contained only discrete water molecules, lacking extended arrays.

Conclusions:

• 1,4-dihydroquinoxaline-2,3-dione derivatives effectively act as supramolecular hosts to control water organization.
• The balance between hydrophilic and hydrophobic regions in the host molecules dictates the dimensionality of water arrays.
• This work provides a foundation for designing functional materials based on tailored water structures.