9,9‐Diethylfluorenes bearing chloromethyl, bromomethyl, and iodomethyl groups in the 2, 4, and 7 positions of the aromatic skeleton were prepared and their solid‐state structures determined by single‐crystal X‐ray diffraction analysis. The prepared fluorenes represent not only valuable starting materials for a wide range of fluorene‐based compounds but are also interesting objects for the analysis of the supramolecular motifs in the crystalline state. The X‐ray diffraction experiments revealed that the asymmetric unit of each structure contains one molecule, featuring similar conformations, but differ in their modes of non‐covalent intermolecular bonding. The crystal structures of the chloromethyl and bromomethyl substituted compounds 1 and 2 are primarily stabilized by Hal···Hal and C–H···Hal contacts, whereas the packing of the iodine substituted analogous compound 3 is influenced by triangular I3 synthons, C–H···π interactions and to a less degree by C–H···I contacts. The manuscript provides information about new synthetic routes, new molecules as well as about halogen/hydrogen bonding patterns and other noncovalent interactions in the crystalline state. Concerning the syntheses, the efficient one‐step synthesis of 9,9‐diethylfluorene‐2,4,7‐tricarbaldehyde (8) is also worthy of particular mention.

A series of new 9,9-diethylfluorenes consisting of three sidearms each bearing a heterocyclic, bis(carboxymethyl)amino, bis (carbamoylmethyl)amino, bis(ethoxycarbonylmethyl)amino or an amino group were prepared on the basis of 2,4,7-tris (bromomethyl)-9,9-diethylfluorene. Imidazolyl, benzimidazolyl, pyrazolyl, pyrrolyl, 1,3-dioxoisoindolyl and pyridinium groups were taken into account as heterocyclic units, attached to the aromatic skeleton via À CH 2 À , À CH 2 NHCH 2 À or À CH 2 N=CHÀ linkers. In addition to the seventeen 2,4,7-trisubstituted 9,9diethylfluorenes, two macrocyclic compounds were prepared on the basis of 2,7-bis(aminomethyl)-9,9-diethylfluorene. The excellent yield of the macrocyclization reaction is worth a special mention. Both the acyclic and the macrocyclic fluorenebased compounds have, among other things, the potential to act as artificial receptors for different substrates in analogy to the known receptors consisting of a benzene or biphenyl core.

Fluorene derivatives containing four to seven phthalimidomethyl groups (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl-methyl groups) were prepared from 9H-fluorene, 9,9-diethyl-9H-fluorene as well as from 2,7-and 2,4,7-functionalized 9,9-diethyl-9Hfluorenes by using the conditions of the Tscherniac-Einhorn reaction. By reacting the 9,9-diethyl substituted fluorenes with N-(hydroxymethyl)phthalimide the 2,4,6,7-and 2,3,4,6,7-substituted derivatives were obtained. In the absence of the ethyl groups, as in the case of 9H-fluorene, the formation of the sixfold and sevenfold substituted compounds was observed (

The title compound, C20H18O3, crystallizes in the space group P21/c with one molecule in the asymmetric unit of the cell. The fluorene skeleton is nearly planar and the crystal structure is composed of molecular layers extending parallel to the (302) plane. Within a layer, one formyl oxygen atom participates in the formation of a Carene—H...O bond, which is responsible for the formation of an inversion symmetric supramolecular motif of graph set R 2 2(10). A second oxygen atom is involved in an intramolecular Carene—H...O hydrogen bond and is further connected with a formyl hydrogen atom of an adjacent molecule. A Hirshfeld surface analysis indicated that the most important contributions to the overall surface are from H...H (46.9%), O...H (27.9%) and C...H (17.8%) interactions.

New representatives of 2,4,7-trisubstituted 9,9-dialkyl-9H-fluorenes were prepared and used for crystallographic investigations as well as initial binding studies towards metal ions and carbohydrates. The binding studies, which included 1 H NMR spectroscopic titrations and fluorescence measurements, demonstrated the ability of the tested fluorene-based compounds to act as complexing agents for ionic and neutral substrates. Depending on the nature of the subunits of the fluorene derivatives, "turn on" or "turn off" fluorescent chemosensors can be developed. Compounds composed of 4,6-dimethylpyridin-2-yl-aminomethyl moieties have the potential to be used as sensitive "turn-on" chemosensors for some metal ions.