Aniline-phenol recognition: from solution through supramolecular synthons to cocrystals
Arijit Mukherjee1, Karuna Dixit2, Siddhartha P Sarma2
1Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India.
Iucrj
|July 31, 2014
Summary
Crystal engineering reveals stable aniline-phenol tetramers and octamers through hydrogen bonding and π–π stacking. This Long-Range Synthon Aufbau Module (LSAM) design strategy predicts crystal structures and is observed in solution via NMR studies.
Area of Science:
- Crystal Engineering
- Supramolecular Chemistry
- Organic Solid-State Chemistry
Background:
- Aniline-phenol recognition is crucial in supramolecular chemistry.
- Understanding molecular interactions in cocrystals informs material design.
- Previous studies have explored hydrogen bonding in related systems.
Purpose of the Study:
- To investigate aniline-phenol recognition within cocrystal structures.
- To explore the formation and transferability of supramolecular synthons.
- To correlate crystal packing with solution-state behavior.
Main Methods:
- Cocrystallization of halogenated phenols and anilines.
- X-ray crystallography for structural characterization.
- Nuclear Magnetic Resonance (NMR) spectroscopy (1D, 15N, NOE, DOSY, T1) in solution.
Main Results:
- Formation of a cyclic hydrogen-bonded tetramer synthon ([⋯O-H⋯N-H⋯]2).
- Observation of an extended octamer synthon (Long-Range Synthon Aufbau Module - LSAM) via hydrogen bonding and π–π stacking in ten cocrystals.
- Prediction of crystal cell axes based on LSAM and halogen bonding.
- NMR studies confirmed the stability of hydrogen-bonded aggregates and π–π stacking in concentrated solution, which is lost upon dilution.
Conclusions:
- The LSAM is a robust and transferable supramolecular synthon for crystal engineering.
- The observed crystal structures can be predicted using the LSAM concept.
- Aniline-phenol aggregates formed via hydrogen bonding and π–π stacking exist in solution and exhibit concentration-dependent behavior.
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