New High Pressure Crystal Structures of 2,2-Dimethylbutane and 2,3-Dimethylaniline: Combined X‑ray, Raman, and Theoretical Studies

Crystals of 2,2-dimethylbutane (DMB) and 2,3-dimethylaniline (DMA) have been crystallized from liquid under high-pressure in a diamond anvil cell. Single crystals of both compounds were obtained at 2.7 and 0.3 GPa, respectively. High-pressure X-ray measurements were performed, and new high pressure crystal structures of DMA and DMB have been refined. The freezing critical pressure for DMA (0.185 GPa) was measured with a piston–cylinder apparatus. The phase transition is accompanied by a considerable rise in molecular volume of 7.3%. For both compounds, experimental Raman spectra measured for the liquid and crystal forms have been compared to quantum chemically predicted spectra calculated for the isolated molecules and applying periodic computations. All the computational results obtained for the high frequency modes were shifted to higher values and needed to be scaled to reproduce experimental findings. The differences in the frequency values due to phase transitions of DMA and DMB were reproduced by theoretical calculations of the isolated molecules and periodic systems. The frequency values derived from periodic theoretical calculations agree better with the experimental frequencies measured for a given crystal structure (RMSDs equal to 16 and 31 cm–1 for DMA and DMB, respectively), whereas the frequency values obtained for the gas phase calculations agree better with experimental results collected for the liquid state (RMSDs equal to 9 and 17 cm–1 for DMA and DMB, respectively). The influence of the “empirical dispersion correction” (when unit cell parameters were constrained during optimization to the experimental values) on frequency values obtained from periodic calculations was also investigated. Computed theoretical frequencies obtained with the use of the correction agree better with experimental results

New High Pressure Crystal Structures of 2,2-Dimethylbutane and 2,3-Dimethylaniline: Combined X‑ray, Raman, and Theoretical Studies

Crystals of 2,2-dimethylbutane (DMB) and 2,3-dimethylaniline (DMA) have been crystallized from liquid under high-pressure in a diamond anvil cell. Single crystals of both compounds were obtained at 2.7 and 0.3 GPa, respectively. High-pressure X-ray measurements were performed, and new high pressure crystal structures of DMA and DMB have been refined. The freezing critical pressure for DMA (0.185 GPa) was measured with a piston–cylinder apparatus. The phase transition is accompanied by a considerable rise in molecular volume of 7.3%. For both compounds, experimental Raman spectra measured for the liquid and crystal forms have been compared to quantum chemically predicted spectra calculated for the isolated molecules and applying periodic computations. All the computational results obtained for the high frequency modes were shifted to higher values and needed to be scaled to reproduce experimental findings. The differences in the frequency values due to phase transitions of DMA and DMB were reproduced by theoretical calculations of the isolated molecules and periodic systems. The frequency values derived from periodic theoretical calculations agree better with the experimental frequencies measured for a given crystal structure (RMSDs equal to 16 and 31 cm^–1 for DMA and DMB, respectively), whereas the frequency values obtained for the gas phase calculations agree better with experimental results collected for the liquid state (RMSDs equal to 9 and 17 cm^–1 for DMA and DMB, respectively). The influence of the “empirical dispersion correction” (when unit cell parameters were constrained during optimization to the experimental values) on frequency values obtained from periodic calculations was also investigated. Computed theoretical frequencies obtained with the use of the correction agree better with experimental results

New High Pressure Crystal Structures of 2,2-Dimethylbutane and 2,3-Dimethylaniline: Combined X‑ray, Raman, and Theoretical Studies

Crystals of 2,2-dimethylbutane (DMB) and 2,3-dimethylaniline (DMA) have been crystallized from liquid under high-pressure in a diamond anvil cell. Single crystals of both compounds were obtained at 2.7 and 0.3 GPa, respectively. High-pressure X-ray measurements were performed, and new high pressure crystal structures of DMA and DMB have been refined. The freezing critical pressure for DMA (0.185 GPa) was measured with a piston–cylinder apparatus. The phase transition is accompanied by a considerable rise in molecular volume of 7.3%. For both compounds, experimental Raman spectra measured for the liquid and crystal forms have been compared to quantum chemically predicted spectra calculated for the isolated molecules and applying periodic computations. All the computational results obtained for the high frequency modes were shifted to higher values and needed to be scaled to reproduce experimental findings. The differences in the frequency values due to phase transitions of DMA and DMB were reproduced by theoretical calculations of the isolated molecules and periodic systems. The frequency values derived from periodic theoretical calculations agree better with the experimental frequencies measured for a given crystal structure (RMSDs equal to 16 and 31 cm–1 for DMA and DMB, respectively), whereas the frequency values obtained for the gas phase calculations agree better with experimental results collected for the liquid state (RMSDs equal to 9 and 17 cm–1 for DMA and DMB, respectively). The influence of the “empirical dispersion correction” (when unit cell parameters were constrained during optimization to the experimental values) on frequency values obtained from periodic calculations was also investigated. Computed theoretical frequencies obtained with the use of the correction agree better with experimental results

Fullerene-Functionalized Halogen-Bonding Heteroditopic Hosts for Ion-Pair Recognition

Despite their hydrophobic surfaces with localized π-holes and rigid well-defined architectures providing a scaffold for preorganizing binding motifs, fullerenes remain unexplored as potential supramolecular host platforms for the recognition of anions. Herein, we present the first example of the rational design, synthesis, and unique recognition properties of novel fullerene-functionalized halogen-bonding (XB) heteroditopic ion-pair receptors containing cation and anion binding domains spatially separated by C60. Fullerene spatial separation of the XB donors and the crown ether complexed potassium cation resulted in a rare example of an artificial receptor containing two anion binding sites with opposing preferences for hard and soft halides. Importantly, the incorporation of the C60 motif into the heteroditopic receptor structure has a significant effect on the halide binding selectivity, which is further amplified upon K+ cation binding. The potassium cation complexed fullerene-based receptors exhibit enhanced selectivity for the soft polarizable iodide ion which is assisted by the C60 scaffold preorganizing the potent XB-based binding domains, anion−π interactions, and the exceptional polarizability of the fullerene moiety, as evidenced from DFT calculations. These observations serve to highlight the unique properties of fullerene surfaces for proximal charged guest binding with potential applications in construction of selective molecular sensors and modulating the properties of solar cell devices

The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study

Aim The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. Methods This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. Results Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. Conclusion One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease