Isomorphism in a Series of Five Homologous Compounds

Area of Science:

• Solid-state chemistry
• Crystallography
• Organic materials science

Background:

• Isomorphism, where molecules maintain crystal structure despite chemical variation, is poorly understood, especially for chiral molecules.
• The interplay between molecular chirality and crystal lattice symmetry presents challenges in predicting solid-state behavior.
• Homologous compounds often exhibit diverse crystalline forms, contrasting with the phenomenon of isomorphism.

Purpose of the Study:

• To investigate isomorphism in a homologous series of organic molecules.
• To explore the relationship between molecular structure, chirality, and crystal packing in detail.
• To present a rare case of isomorphic molecular packing in chiral crystals derived from achiral precursors.

Main Methods:

• Synthesis and crystallographic analysis of five m-Y-phenyl-N,N-diisopropylglyoxylamide derivatives (Y = H, F, Cl, Br, I).
• Manual resolution of enantiomorphic crystals using Pasteur's method.
• Quantitative analysis using continuous chirality measures and unit cell similarity index.
• Thermal analyses and detailed crystallographic studies.

Main Results:

• A structurally consistent series of five derivatives exhibiting isomorphism was successfully synthesized and characterized.
• Achiral molecules in solution formed conglomerates of twisted chiral conformations in the solid state.
• Consistent chiral behavior at molecular and crystalline levels was confirmed, validating the isomorphic nature.
• Systematic trends in thermal stability and persistence of packing motifs were observed.

Conclusions:

• Introduced a rare class of chiral molecular materials with isomorphic packing derived from chemically distinct achiral molecules.
• Demonstrated the ability of these compounds to maintain consistent supramolecular chirality and packing motifs.
• Highlighted the broad relevance of these systems for pharmaceuticals and functional materials where solid-state structure impacts performance.