Crystal Structures of 9,9-Disubstituted Fluorene Derivatives Bearing Methyl, Hydroxymethyl or Pyridinylmethyl Groups

The wide range of application possibilities of fluorene derivatives, due to their unique physical and chemical properties, has made this class of molecules important for various disciplines. The synthesis of these compounds and the study of their properties are, therefore, of great scientific interest. Due to their reactivity and sensitivity to oxidation, the 9-position of the fluorene skeleton is often double substituted, for example, to ensure the long-term stability of materials. Single crystal structure analysis, among other methods, plays a very important role in the development of various fluorene-based systems. In this paper, the crystal structures of three 9,9-disubstituted fluorene derivatives bearing methyl, hydroxymethyl or pyridinylmethyl groups are described (three solvent-free structures and one toluene solvate). A detailed evaluation of the intermolecular interactions, supported by Hirshfeld surface analysis, is the subject of this article.