Tricolor Luminescence Switching by Thermal and Mechanical Stimuli in the Crystal Polymorphs of Pyridyl‐substituted Fluorene

Abstract

Stimuli-responsive organic luminescence-switching materials have attracted much attention for ad ecade. Most of the reported examples display areversibletwo-color luminescence switching, and multicolor-switchingm aterials remain extremelyr are. Herein,w er eport as imple organic molecule, 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyridine (MFDP), which exhibits three different crystal polymorphs (V-MFDP, B-MFDP and G-MFDP)w ith different luminescent colors. Furthermore, the three crystal polymorphs show ar e-versible tricolor fluorescent switching from violet to blue and to green upon physicals timuli. The single-crystal structures of the three polymorphs were obtained, and the results indicatet hat the stimuli-responsive properties of the three polymorphs come from the different stacking modes induced by intermoleculari nteractions. The competitionb etween weak p-p stacking and weak hydrogen bonding is the main reason for the the phase transformations among the three crystal polymorphs.Scheme1.The chemical structure and single-crystal structure of MFDP.[a] J.

Chiral Self-Sorting in Truxene-Based Metallacages

“…Thanks to the planar geometry of the central truxene core, the three peripheral nitrogen were found to be in the same plane. The pyridine moieties are twisted around the Ctrux-CPyr axis with an average angle of 40.8(1)°, thus minimizing H-H interactions, as reported for similar compounds [69]. An angle of 120° was found between each pyridine axis in accordance with the C3 symmetry of the Trux3Pyr ligand.…”

Selective Construction of Very Large Stacking-Interaction-Induced Molecular 818 Metalla-knots and Borromean Ring Using Curved Dipyridyl Ligands

“…All mentioned reagents and solvents were purchased from commercial sources and used as supplied unless otherwise mentioned. The starting materials ligand 2,7-di­(pyridin-4-yl)-9 H -fluorene ( L 1 ), 4,4′-(9,9-dimethyl-9 H -fluorene-2,7-diyl)­dipyridine ( L 2 ), and [Cp*RhCl 2 ] 2 were synthesized according to literature methods. NMR spectra were recorded on a Bruker AVANCE I 400 spectrometer.…”

“…Because of its conjugated structure, interesting applications of compounds containing fluorene and its analogues have been discovered in the fields of emitting materials, 29 fluorescent probes, 30,31 magnetic materials, 32 catalysis, 33 and others. 34,35 However, the use of this group in the synthesis of molecular metalla-knots is as yet unknown. This inspired us to modify the fluorene group to make it suitable for use as a ligand in our systems, for combination with metal corner units via coordination-driven assembly.…”

Luminescent polymorphic crystals: mechanoresponsive and multicolor-emissive properties

“…5c). 57 The emission colors of the polymorphs could be switched in response to mechanical grinding. Based on the single-crystal X-ray diffraction analyses, the violet and blue emission of P2 1 2 1 2 1 and P1 ¯polymorphs, respectively, should be attributed to the different dimers of 9.…”