Effects of Gamma Radiation on Single- and Multicomponent Organic Crystalline Materials

Abstract

Exploration of highly ionizing radiation damage to organic materials has mainly been limited to polymers and singlecomponent organic crystals due to their use in coatings and scintillation detection. Additional efforts are needed to create new tunable organic systems with stability in highly ionizing radiation to rationally design novel materials with controllable chemical and physical properties. Cocrystals are a promising class of compounds in this area because of the ability to rationally design bonding and molecular interactions that could lead to novel material properties. However, currently it is unclear if cocrystals exposed to radiation will maintain crystallinity, stability, and physical properties. Herein, we report the effects of γ radiation on both single-component-and multicrystalline organic materials. After irradiation with 11 kGy dose both single-(trans-stilbene, trans-1,2-bis(4-pyridyl)ethylenewhere n = 1, 2, or 3)), and multicomponent materials (4,4′-bpe)•(1,n-C 6 I 2 F 4 ), (4,4′-bpe)•(1,n-C 6 Br 2 F 4 ), and (4,4′bpe)•(1,n-C 6 H 6 O 2 ) were analyzed and compared to their preirradiated forms. Radiation damage was evaluated via single-crystaland powder-X-ray diffraction, Raman spectroscopy, differential scanning calorimetry, and solid-state fluorimetry. Single-crystal X-ray diffraction analysis indicated minimal changes in the lattice postirradiation, but additional crystallinity changes for bulk materials were observed via powder X-ray diffraction. Overall, cocrystalline forms with 4,4′-bpe were more stable than the related singlecomponent systems and were related to the relative stability of the individual conformers to γ radiation. Fluorescence signals were maintained for trans-stilbene and 4,4′-bpe, but quenching of the signal was observed for the cocrystalline forms to varying degrees. Three of the single components, 1,2-diiodotetrafluorobenzene (1,2-C 6 I 2 F 4 ), 1,4-diiodotetrafluorobenzene (1,4-C 6 I 2 F 4 ), and 1,4dibromotetrafluorobenzene (1,4-C 6 Br 2 F 4 ), also underwent sublimation within an hour of exposure to air postirradiation. Further analysis using differential scanning calorimetry (DSC) and Raman spectroscopy attributed this phenomenon to removal of impurities adsorbed to the crystal surface during irradiation.

RETRACTED: Organic Cocrystal Design to Promote Absorption and Triplet Excitons Formation for Sensitive Scintillator

“…[35] Impressively, Tori Z. Forbes et al demonstrated that organic cocrystals could reduce structural defects when exposed to gamma radiation, especially in terms of maintaining crystallinity, stability, and physical properties, compared to polymers and single organic crystals. [36] However, the fundamental mechanism underlying the performance of organic cocrystals when exposed to radiation, the guiding principles for selecting and designing cocrystal compositions, and the influence of structural intricacies on the final scintillation properties remain enigmatic. A comprehensive understanding of these scientific intricacies forms the pivotal cornerstone for the extension of this material system to X-ray scintillation applications.…”

Atomistic‐Level Effects of Noncovalent Interactions and Crystalline Packing for Organic Material Structural Integrity upon Exposure to Gamma Radiation

“…In this study, we utilize experimental and computational approaches to examine the impact of γ radiation exposure on single‐component ( trans ‐stilbene, trans ‐1,2‐bis(4‐pyridyl)ethylene ( 4,4’‐bpe ), 1, n ‐diiodotetrafluorobenzene ( 1, n ‐C 6 I 2 F 4 ), 1, n ‐dibromotetrafluorobenzene ( 1, n ‐C 6 Br 2 F 4 ), 1, n ‐dihydroxybenzene ( 1, n ‐C 6 H 6 O 2 ) (where n =1, 2, or 3)) and as binary cocrystals ( 4,4’‐bpe ) ⋅ ( 1, n ‐C 6 I 2 F 4 ), ( 4,4’‐bpe ) ⋅ ( 1, n ‐C 6 Br 2 F 4 ), and ( 4,4’‐bpe ) ⋅ ( 1, n ‐C 6 H 6 O 2 ), where n =1, 2, or 3 (Scheme 1). These materials were chosen based on their similarity to common organic scintillators, aromaticity, and to introduce a variety of crystalline packing and halogen/hydrogen bonding arising from the systematic changes in functional group placement [16] . In this study, organic crystalline materials were exposed to a variety of γ radiation doses (0, 1, 5, 10, 20 kGy), then evaluated by electron paramagnetic resonance (EPR) spectroscopy before and after each irradiation.…”

“…[10][11][12][13] Cocrystal engineering has previously been utilized for the rational design of materials for pharmaceutics, [14] optoelectronics, [15] and solid-state reactions, [8,9] and also can be used as a basis for the construction of radiation stable materials. [16] Using this tunability, atomistic-level changes in crystal packing and noncovalent interactions (i. e., hydrogen bonding, halogen bonding, π-π stacking) can be explored to relate structural integrity to γ radiation dose.…”

“…These materials were chosen based on their similarity to common organic scintillators, aromaticity, and to introduce a variety of crystalline packing and halogen/hydrogen bonding arising from the systematic changes in functional group placement. [16] In this study, organic crystalline materials were exposed to a variety of γ radiation doses (0, 1, 5, 10, 20 kGy), then evaluated by electron paramagnetic resonance (EPR) spectroscopy before and after each irradiation. The linear energy transfer of γ radiation is small such that the energy transferred and absorbed is negligible regardless of density within organic systems, [17] therefore EPR is necessary to monitor atomistic-level changes which would otherwise be difficult to observe experimentally.…”

“…Cocrystals are a major focus of this work because the presence of multiple molecules within the extended lattice allows for the control of tunable properties such as dimensionality, composition, and intermolecular interactions [10–13] . Cocrystal engineering has previously been utilized for the rational design of materials for pharmaceutics, [14] optoelectronics, [15] and solid‐state reactions, [8,9] and also can be used as a basis for the construction of radiation stable materials [16] . Using this tunability, atomistic‐level changes in crystal packing and noncovalent interactions (i. e., hydrogen bonding, halogen bonding, π–π stacking) can be explored to relate structural integrity to γ radiation dose.…”