Hydrostatic Pressure‐Controlled Ratiometric Luminescence Responses of a Dibenzo[a,j]phenazine‐Cored Mechanoluminophore

Abstract

Understanding changes in excited state properties under the influence of an external stimulus, such as pressure or temperature, is important in the context of optimizing molecular components for a number of applications including sensors and imaging reagents. Herein, we use UV/Vis absorption, fluorescence and excitation spectroscopies and fluorescence lifetime measurements supported by calculations to probe the effect of hydrostatic pressure on the excited state characteristics of a conformationally-divergent mechanochromic compound PTZ-DBPHZ (containing two phenothiazine moieties attached to a dibenzo[a,j]phenazine core) in toluene and methylcyclohexane. We demonstrate that hydrostatic pressure can be used to manipulate the equilibria between excited state conformers. This work provides new perspectives for mechanoresponsive materials and as an attractive alternative to conventional ratiometric sensors.[a] Prof.

Ground- and excited-state dynamic control of an anion receptor by hydrostatic pressure

“…Indeed, we have recently revealed that optical properties, molecular and biomolecular recognition behavior and photo-physical/chemical processes in solutions of various molecular, supramolecular, macromolecular and biomacromolecular systems are precisely regulated by hydrostatic pressure. [53][54][55][56][57][58][59][60][61][62][63] Hence, these trends prompted us to newly investigate an applicable supramolecular recognition system under hydrostatic pressures.…”

Hydrostatic‐Pressure‐Controlled Molecular Recognition: A Steroid Sensing Case Using Modified Cyclodextrin

“…As shown in Figure 4, the fluorescence intensities of H gradually decrease with increasing pressure. It is well‐known that fluorescence intensities of common organic fluorophores increase with increasing pressure due to increasing solvent viscosities, [45,59,60] enabling us to rule out the pressure effect on the dansyl branch itself. The d I /d P at 0.1–20 MPa is steeper, rather than the gentler slope at ≥40 MPa, which means that the included fluorescence branch is kicked out to more polar solvent (bulk water) at the early pressurization stage.…”

“…The high‐pressure apparatus was used for spectroscopic measurements. The details were reported previously [59–64] . Sapphire windows were employed for UV/vis and fluorescence spectroscopy and lifetime measurements, while birefringence‐free diamond windows were employed for circular dichroism spectroscopy.…”

“…The effects on homogeneous solutions upon hydrostatic pressurization are presented herein, rather than the solid‐state chemistry under high pressure using diamond anvil cells [57,58] . Specifically, we have so far demonstrated that emission behavior of the mechanochromic luminogens [59,60] and the chromophoric polymers, [61,62] solvatochromism of the Reichardt's dye, [63] and chiroptical properties of the hexaarylbenzenes [64] are critically regulated by hydrostatic pressure. Therefore, these research trends prompted us to construct a novel pressure‐controlled molecular recognition system.…”

Alchemy of donor–acceptor–donor multi-photofunctional organic materials: from construction of electron-deficient azaaromatics to exploration of functions

“…Takeda, Penfold, and Fukuhara recently investigated the effect of hydrostatic pressure on the photophysical properties of 9e in solution, where the fluctuation of molecular conformations would be more sensitive toward the materials environments. 32 In contrast to the solid states, 9e in toluene shows 3 distinct CT emissions derived from the 3 different conformers (eq-eq, ax-eq, and ax-ax types) (Fig. 12a).…”