Substituent-Controlled Quantum Dynamics in 2-Butynyl Alcohol–Water Dimer: Insights from Rotational Spectroscopy

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Abstract
The binary 2-butynyl alcohol-H2O complex was explored using pulsed-jet Fourier transform microwave spectroscopy with complementary quantum chemical calculations. Distinct tunneling-induced splittings in the rotational spectra reveal two large-amplitude motions: internal rotation of water (V2 = 4.33 kJ mol-1) and concerted tunneling of water and the hydroxyl group (B2 = 6.61 kJ mol-1). The observed isomer is stabilized by dual OH···Ow and Ow-H···πC≡C hydrogen bonds. Electronic structure analyses indicate that methyl substitution strengthens the Ow-H···πC≡C interaction, oppositely modulating these two tunneling pathways─restricting water rotation while facilitating skeletal torsion. These findings demonstrate how substituent effects control tunneling cooperativity in hydrogen-bonded systems, offering mechanistic insight into substituent-controlled quantum hydrogen dynamics in weakly bound clusters.
Funding Information
  • Natural Science Foundation of Guizhou Province (ZK[2023]294)
  • State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences (J24-25-908)
  • Fundamental Research Funds for the Central Universities (2025CDJ-IAISYB-060)
  • National Natural Science Foundation of China (22402216)
  • National Natural Science Foundation of China (22473018)
  • National Natural Science Foundation of China (22473019)
  • National Natural Science Foundation of China (W2512014)
  • Chongqing Talents: Exceptional Young Talents Project (cstc2021ycjhbgzxm0027)

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