| Summary: | 碩士 === 國立東華大學 === 化學系 === 96 === During past years much scientific interest has been dedicated to the weak intermolecular interactions involving C–H…O or C–H…N hydrogen bonds. Several studies have shown the potential significant effect that pressure has on controlling the strength of C–H…O interactions. Because C–H…O and C–H…N interactions are typically weaker than those of the more conventional O–H…O and N–H…O hydrogen bonds, direct measurement of their strength is very difficult to achieve. Our present study is an attempt to provide the experimental spectroscopic evidence of charge-enhanced C–H…O interactions. Static pressures up to several- megabars can be generated using diamond anvil cells. The static approach is of interest because it allows continuous tuning of the pressure and the possibility to employ a large number of probing techniques that allow in situ measurements. The triethylamine(TEA)/D2O mixture provides a classic textbook model for phase separation in a relatively simple mixture. This mixture has a lower critical solution temperature (LCST), above which it splits into a water-rich phase and a TEA-rich phase. For pure triethylamine, an increase in pressure leads to a blue frequency shift of the C–H bands. Under high-pressure conditions, the relative weights of the strong intramolecular interactions responsible for molecular bonding, and of the weaker intermolecular forces defining the aggregation state, are altered, and the repulsive side of the intermolecular potential is explored. Nevertheless, the high pressure study of the C–H bands for a dilute protonated triethylamine/D2O solution yielded an unusual nonmonotonic pressure dependence. This result indicates charge-enhanced C–H…O hydrogen-bond formation at high pressure.
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