Binary and ternary charge-transfer complexes using 1,3,5-tri-nitro-benzene.

Area of Science:

• Crystal engineering
• Supramolecular chemistry
• Organic solid-state chemistry

Background:

• 1,3,5-tri-nitro-benzene is a well-known electron acceptor.
• Charge-transfer complexes are formed between electron donors and acceptors.
• Crystal engineering aims to design materials with specific properties by controlling crystal packing.

Purpose of the Study:

• To synthesize and characterize novel binary and ternary charge-transfer complexes involving 1,3,5-tri-nitro-benzene.
• To investigate the structural features, including stacking interactions and hydrogen bonding, of these complexes.
• To explore the application of crystal engineering in modifying the packing and properties of charge-transfer complexes.

Main Methods:

• Synthesis of four charge-transfer complexes: three binary and one ternary.
• Single-crystal X-ray diffraction analysis to determine the molecular and crystal structures.
• Analysis of intermolecular interactions, including C-H···O hydrogen bonds and hydrogen bonds within complex (IV).

Main Results:

• Successful synthesis of three binary complexes (I-III) and one ternary complex (IV) with 1,3,5-tri-nitro-benzene.
• All complexes exhibit alternating donor and acceptor stacks with weak C-H···O hydrogen bonds.
• Complex (IV) showcases crystal engineering, with a third molecule stabilized by strong hydrogen bonds between carboxylic acid and pyridine groups.

Conclusions:

• The synthesized charge-transfer complexes display characteristic alternating donor-acceptor stacking motifs.
• Weak C-H···O hydrogen bonds play a role in stabilizing the crystal structures.
• Complex (IV) exemplifies successful crystal engineering through the incorporation of a third molecule, leading to enhanced structural stability via specific hydrogen bonding.