Regulating and Predicting the Polyhedral Crystal Morphology in Spirofluorene Molecular Systems

Area of Science:

• Materials Science
• Crystallography
• Organic Chemistry

Background:

• Organic steric molecules exhibit diverse polyhedral crystal morphologies.
• The precise relationships between molecular structure, supramolecular interactions, aggregation, and crystal morphology remain elusive.

Purpose of the Study:

• To demonstrate the feasibility of predicting crystal morphology using periodic bond chain (PBC) theory.
• To elucidate the influence of molecular structure and intermolecular interactions on crystal habit in spiro-molecules.

Main Methods:

• Utilized periodic bond chain (PBC) theory combined with interaction energy (IE) calculations.
• Analyzed two model spiro-molecules: spiro[fluorene-9,9'-xanthene] (SFX) and spiro[cyclopenta[1,2-b:5,4-b']dipyridine-5,9'-xanthene] (SDAFX).
• Quantified PBC vectors on a supramolecular level.

Main Results:

• SFX, dominated by van der Waals forces, exhibited a single PBC direction, resulting in irregular 1D rod-like crystals.
• SDAFX, with additional N heteroatoms, displayed 3D-oriented PBCs due to hydrogen bonding and other interactions, leading to an octahedral crystal structure.
• The study successfully predicted crystal morphologies based on molecular and supramolecular properties.

Conclusions:

• Periodic bond chain (PBC) theory, enhanced by interaction energy analysis, provides a robust method for predicting organic crystal morphology.
• The presence of heteroatoms and resulting intermolecular interactions significantly influence the dimensionality of PBCs and the final crystal habit.
• Developed a quantitative approach for PBC vector analysis in organic molecular systems, advancing crystallization studies.