In this study, the conformational preferences and large amplitude motions (LAM) of a series of methoxypyridines (MOPY) are investigated both computationally, with DFT and coupled cluster methods, and using chirped pulse Fourier transform microwave (CP-FTMW) Spectroscopy. In analogy with the previously investigated 2-MOPY, 3-MOPY shows conformational preference due to electronic and steric interactions between the methoxy group and pyridine ring. Splittings due to methyl rotor LAM occur in the spectra of both 2- and 3-MOPY. Methoxy rotor LAM is also probed predominantly in 4-MOPY. We will report progress on the construction of a new segmented CP-FTMW spectrometer operating in the 8-18 GHz region. Rotational spectroscopy of the 3- and 4-MOPY isomers are used to experimentally characterize the molecular geometry and LAM investigated computationally. In the symmetric 4-MOPY isomer, we calculate the 2-D potential of the methoxy and methyl internal rotation and discuss differences between 4-MOPY and methoxybenzene resulting from the heterocycle electronic structure.

Experimental and theoretical study of large amplitude motions in methoxypyridine

ACS Spring 2022

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