Optical nature of non‐substituted triphenylmethyl cation: Crystalline state emission, thermochromism, and phosphorescence

Abstract

Since the discovery of the triphenylmethyl (trityl) cation 120 years ago, a variety of aromatic cations having various colors and luminescence properties have been rigorously studied. Many, differently substituted trityl cations have been synthesized, and their optical properties have been elucidated. However, the optical properties of the parent, non-substituted and highly reactive trityl cation, which was observed to be very weakly luminescent, have not been subjected to detailed investigation. In the effort described herein, we explored the optical nature of non-substituted trityl hexafluorophosphate (PF 6 ) in the crystalline state. Trityl PF 6 was found to exist as two crystal polymorphs including a yellow (Y) and an orange (O) form. Moreover, we observed that these crystalline forms display crystalline-state emission with different colors. The results of X-ray crystallographic analysis showed that the two polymorphs have totally different molecular packing arrangements. Furthermore, an investigation of their optical properties revealed that the O-crystal undergoes a distinct color change to yellow upon cooling as a consequence of a change in the nature of the charge transfer interaction between the cation and PF 6 anion, and that both the Yand O-crystal exhibit phosphorescence.

Redox‐Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems

“…The redox chemistry of pure hydrocarbons is expanding rapidly, and these examples will be covered in another review. Furthermore, although excluded from this review, the development of pure hydrocarbon‐based response systems based on different approaches from electrochemical stimulation is also being actively pursued [132–138] . Based on pure hydrocarbons with aromatic rings that show various stimuli‐responsive properties, it will be possible to develop more sophisticated response systems.…”

Stacked 3D Antiaromaticity in the π-Congested Space Between the Aromatic Rings in the Anthracene Dimer

“…TD-DFT calculations of anthracenophane 1 were performed using CAM-B3LYP functional with a tuned parameter method (μ = 0.150, α = 0.0799, β = 0.9201 [α + β = 1.0]). [10,11] 2.2. X-ray crystallographic analysis using a diamond anvil cell X-ray crystal data under hydrostatic pressure were collected at 296 K on Rigaku XtaLAB Synergy Custom (Detector is Hypix-6000HE.…”

Synthesis, Properties, and Intermolecular Interactions in the Solid States of π-Congested X-Shaped 1,2,4,5-Tetra(9-anthryl)benzenes

“…In an exploration to test these proposals, we observed that CT complexation does not take place between 4a and several acceptors such as 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,7,8,, or 1,2,4,5-tetracyanobenzene (TCNB) owing to the 4a insolubility issue. Although the CT complexation between 4c and the above acceptors also does not occur, 4b does form CT complexes with F4-TCNQ and TCNB, whose single crystals are suitable for the Xray analysis.…”

“…This type of solid state molecular assembly is a distinctive feature of aromatic congested molecules such as the six-fold phenyl embracing, which is six-fold edge-to-face interactions of phenyl rings observed in tetraphenyl phosphonium and triphenylmethyl 2 cation dimers. [7,8] Furthermore, photoirradiation promotes intramolecular [4+4] cycloaddition reactions between neighboring Ant in units the respective di-Ant and tri-Ant substituted benzenes 1a and 2a, which can be thermally reversed. These photo/thermal properties enable these substances to undergo, light heat and mechanical stress stimulated color change responses.…”