Discrete versus infinite molecular self-assembly: control in crystalline hydrogen-bonded assemblies based on...

Area of Science:

• Supramolecular Chemistry
• Crystal Engineering
• Materials Science

Background:

• Hydrogen bonding plays a crucial role in the self-assembly of molecular solids.
• The interplay between molecular structure and crystal packing dictates emergent properties.
• 1,2-bis(4-pyridyl)ethane (4,4'-bipyeth) is a versatile building block for coordination polymers and supramolecular networks.

Purpose of the Study:

• To investigate the cocrystallization behavior of 1,2-bis(4-pyridyl)ethane (4,4'-bipyeth) with substituted resorcinols.
• To elucidate the influence of halogen substitution on resorcinol on the resulting solid-state structures.
• To understand the role of steric effects in directing the formation of 1D arrays versus discrete complexes.

Main Methods:

• Cocrystallization of 4,4'-bipyeth with resorcinol, 4-chlororesorcinol, and 4,6-dichlororesorcinol.
• Single-crystal X-ray diffraction analysis to determine the crystal structures.
• Analysis of hydrogen bonding interactions (O-H...N) and steric factors.

Main Results:

• Formation of three distinct molecular solids: (4,4'-bipyeth).(res) 1a, 2(4,4'-bipyeth).2(4-Cl-res) 1b, and 2(4,4'-bipyeth).2(4,6-di-Cl-res) 1c.
• Compound 1a exhibits an infinite 1D polar array structure.
• Compounds 1b and 1c form discrete 0D four-component complexes, attributed to steric hindrance from chlorine substituents.
• O-H...N hydrogen bonds are the primary interaction mediating the assembly in all studied systems.

Conclusions:

• The degree of chlorination on resorcinol significantly impacts the self-assembly outcome.
• Peripheral steric effects effectively prevent solid-state polymerization, favoring discrete molecular assemblies.
• This study highlights the rational design of supramolecular architectures through controlled cocrystallization.