Anion mediated, tunable isoguanosine self-assemblies: decoding the conformation influence and solvent effects

Area of Science:

• Supramolecular Chemistry
• Coordination Chemistry
• Nucleic Acid Analogs

Background:

• Guanine derivatives, such as isoG, are known for their self-assembly properties.
• Previous studies on C8-substituted isoG analogs showed limitations in forming higher-order structures due to steric hindrance.
• Cesium (Cs+) ion coordination with nucleic acid structures is an area of interest for developing novel ionophores.

Purpose of the Study:

• To synthesize and investigate novel deoxy isoG derivatives for Cs+ coordination.
• To overcome structural limitations in pentaplex formation observed with earlier C8-phenyl substituted isoG analogs.
• To explore the influence of solvent and counter-anion on the assembly of isoG-Cs+ complexes.

Main Methods:

• Synthesis of modified deoxy isoG derivatives with ribose protection (tert-butyldimethylsilyl ether).
• Coordination studies with Cs+ cations in various solvents (CDCl3, CD3CN) and with different anions (BPh4-, BARF-, PF6-).
• Structural characterization using X-ray crystallography.

Main Results:

• Modified deoxy isoG derivatives enabled controllable formation of stable isoG pentaplexes with Cs+.
• Various assemblies were formed, including singly charged decamers, doubly charged decamers, and 15-mers.
• The X-ray crystal structure of [isoG20Cs3]3+(BARF-)3 revealed the first multi-layer deoxy isoG binding with Cs+, demonstrating a novel ionophore capability beyond simple sandwich assemblies.

Conclusions:

• Modification of the ribose moiety in deoxy isoG derivatives is crucial for achieving higher-order Cs+ complexation.
• Solvent and anion choice significantly influence the type and stability of the formed isoG pentaplexes.
• The newly developed deoxy isoG derivatives represent a promising class of ionophores for selective cation binding and multi-layer self-assembly.