When periodically packing the intramolecular donor-acceptor structures to form ferroelectric-like lattice identified by second harmonic generation, our CD49 molecular crystal shows long-wavelength persistent photoluminescence peaked at 542 nm with the lifetime of 0.43 s, in addition to the short-wavelength prompt photoluminescence peaked at 363 nm with the lifetime of 0.45 ns. Interestingly, the long-wavelength persistent photoluminescence demonstrates magnetic field effects, showing as crystalline intermolecular charge-transfer excitons with singlet spin characteristics formed within ferroelectric-like lattice based on internal minority/majority carrier-balancing mechanism activated by isomer doping effects towards increasing electron-hole pairing probability. Our photoinduced Raman spectroscopy reveals the unusual slow relaxation of photoexcited lattice vibrations, indicating slow phonon effects occurring in ferroelectric-like lattice. Here, we show that crystalline intermolecular charge-transfer excitons are interacted with ferroelectric-like lattice, leading to exciton-lattice coupling within periodically packed intramolecular donor-acceptor structures to evolve ultralong-lived crystalline light-emitting states through slow phonon effects in ferroelectric light-emitting organic crystal.
Developing an atomistic understanding of ionizing radiation induced changes to organic materials is necessary for intentional design of greener and more sustainable materials for radiation shielding and detection. Cocrystals are promising for these purposes, but a detailed understanding of how the specific intermolecular interactions within the lattice upon exposure to radiation affect the structural stability of the organic crystalline material is unknown. This study evaluates atomistic‐level effects of γ radiation on both single‐ and multicomponent organic crystalline materials and how specific noncovalent interactions and packing within the crystalline lattice enhance structural stability. Dose studies were performed on all crystalline systems and evaluated via experimental and computational methods. Changes in crystallinity were evaluated by p‐XRD and free radical formation was analyzed via EPR spectroscopy. Type of intermolecular interactions and packing within the crystal lattice was delineated and related to the specific free radical species formed and the structural integrity of each material. Periodic DFT and HOMO‐LUMO surface mapping calculations provided atomistic‐level identifications of the most probable sites for the radicals formed upon exposure to γ radiation and relate intermolecular interactions and molecular packing within the crystalline lattice to experimental results.
more » « less- PAR ID:
- 10467578
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 29
- Issue:
- 64
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Polymorphism, the ability for a given material to adopt multiple crystalline packing states, is a powerful approach for investigating how changes in molecular packing influence charge transport within organic semiconductors. In this study, a new “thin film” polymorph of the high‐performance, p‐type small molecule N‐octyldiisopropylsilyl acetylene bistetracene (BT) is isolated and characterized. Structural changes in the BT films are monitored using static and in situ grazing‐incidence X‐ray diffraction. The diffraction data, combined with simulation and crystallographic refinement calculations, show the molecular packing of the “thin film” polymorph transforms from a slipped 1D π‐stacking motif to a highly oriented and crystalline film upon solvent vapor annealing with a 2D brick‐layer π‐stacking arrangement, similar to the so‐called “bulk” structure observed in single crystals. Charge transport is characterized as a function of vapor annealing, grain orientation, and temperature. Demonstrating that mobility increases by three orders of magnitude upon solvent vapor annealing and displays a differing temperature‐dependent mobility behavior.
-
more » « less
Abstract The ultralong‐lived upconversion luminescence with the lifetime of 0.48 s in a broad spectral range (530–650 nm) is observed in CD49 (9‐(3‐(5‐bromopyridin‐3‐yl)prop‐2‐yn‐1‐yl)‐9
H ‐carbazole) crystal designed with donor–acceptor (carbazole–pyridine) structures under infrared excitation, simultaneously accompanied with second harmonic generation (SHG). This phenomenon indicates orderly packing donor–acceptor structures form a nonlinearly polarizable ferroelectric‐like lattice with ultralong‐lived light‐emitting states, leading to much prolonged nonlinear optical behaviors. The persistent upconversion luminescence together with SHG is largely reduced when lowering crystallinity. This implies that nonlinearly polarizable ferroelectric‐like lattice provides the necessary condition to generate persistent upconversion luminescence. Evidently, persistent upconversion luminescence becomes completely lacking when only using ultralong‐lived light‐emitting states without nonlinearly polarizable ferroelectric‐like lattice, exampled by 4‐(dimethylamino)benzonitrile dispersed in polyvinyl alcohol matrix. Magneto‐photoluminescence shows that persistent upconversion luminescence is essentially a super‐delayed fluorescence from crystalline intermolecular charge‐transfer excitons formed in the nonlinearly polarizable ferroelectric‐like lattice. Magnetodielectrics indicate crystalline intermolecular charge‐transfer excitons are coupled with nonlinearly polarizable ferroelectric‐like lattice, leading to prolonged nonlinear optical behaviors shown as persistent upconversion luminescence through super delayed fluorescence. Therefore, crystalline intermolecular charge‐transfer excitons formed in nonlinearly polarizable ferroelectric‐like lattice provide an interesting platform to generate prolonged nonlinear optical behaviors toward developing persistent upconversion luminescence under multiphoton excitation. -
more » « less
Understanding hydrogen-bond interactions in self-assembled lattice materials is crucial for preparing such materials, but the role of hydrogen bonds (H bonds) remains unclear. To gain insight into H-bond interactions at the materials’ intrinsic spatial scale, we investigated ultrafast H-bond dynamics between water and biomimetic self-assembled lattice materials (composed of sodium dodecyl sulfate and β-cyclodextrin) in a spatially resolved manner. To accomplish this, we developed an infrared pump, vibrational sum-frequency generation (VSFG) probe hyperspectral microscope. With this hyperspectral imaging method, we were able to observe that the primary and secondary OH groups of β-cyclodextrin exhibit markedly different dynamics, suggesting distinct H-bond environments, despite being separated by only a few angstroms. We also observed another ultrafast dynamic reflecting a weakening and restoring of H bonds between bound water and the secondary OH of β-cyclodextrin, which exhibited spatial uniformity within self-assembled domains, but heterogeneity between domains. The restoration dynamics further suggest heterogeneous hydration among the self-assembly domains. The ultrafast nature and meso- and microscopic ordering of H-bond dynamics could contribute to the flexibility and crystallinity of the material––two critically important factors for crystalline lattice self-assemblies––shedding light on engineering intermolecular interactions for self-assembled lattice materials.
-
Conventional strategies for materials design have long been used by leveraging primary bonding, such as covalent, ionic, and metallic bonds, between constituent atoms. However, bond energy required to break primary bonds is high. Therefore, high temperatures and enormous energy consumption are often required in processing and manufacturing such materials. On the contrary, intermolecular bonds (hydrogen bonds, van der Waals forces, electrostatic interactions, imine bonds, etc.) formed between different molecules and functional groups are relatively weaker than primary bonds. They, thus, require less energy to break and reform. Moreover, intermolecular bonds can form at considerably longer bond lengths between two groups with no constraint on a specific bond angle between them, a feature that primary bonds lack. These features motivate unconventional strategies for the material design by tuning the intermolecular bonding between constituent atoms or groups to achieve superior physical properties. This paper reviews recent development in such strategies that utilize intermolecular bonding and analyzes how such design strategies lead to enhanced thermal stability and mechanical properties of the resulting materials. The applications of the materials designed and fabricated by tuning the intermolecular bonding are also summarized, along with major challenges that remain and future perspectives that call for further attention to maximize the potential of programming material properties by tuning intermolecular bonding.more » « less
