Two fluoradene derivatives: pseudosymmetry, eccentric ellipsoids and a phase transition

Area of Science:

• Crystallography
• Materials Science
• Organic Chemistry

Background:

• Fluoradene derivatives are complex polycyclic aromatic hydrocarbons.
• Pseudosymmetry in crystal structures can complicate diffraction analysis.
• Understanding crystal packing is crucial for predicting material properties.

Purpose of the Study:

• To determine the crystal structures of two novel fluoradene derivatives.
• To investigate the nature and extent of pseudosymmetry in these structures.
• To analyze the relationship between molecular conformation and crystal packing.

Main Methods:

• Single-crystal X-ray diffraction was used to collect diffraction data.
• Crystal structures were solved and refined using standard crystallographic software.
• Analysis of atomic coordinates and Wilson statistics were employed to study pseudosymmetry.

Main Results:

• Two fluoradene derivatives, 7b-triisopropylsilylfluoradene and 7b-(2,4-dinitrophenyl)fluoradene, were structurally characterized.
• Both compounds exhibit significant pseudosymmetry in their crystal structures, with varying unit cell configurations (P1, Z'=2 and P2(1)/c, Z'=1 or 2).
• Temperature-dependent studies indicated a phase transition in one derivative, influenced by pseudosymmetric packing.

Conclusions:

• Pseudosymmetry is a prominent feature in these fluoradene derivatives, impacting their crystallographic descriptions.
• Detailed structural analysis, including pseudocell refinements and intensity analysis, is essential for understanding deviations from ideal symmetry.
• The findings contribute to the understanding of structure-property relationships in curved polycyclic aromatic systems.