Explicitly correlated coupled cluster calculations for propadienylidene (H(2)CCC)

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Astrochemistry

Background:

• Propadienylidene (H(2)CCC) is a reactive carbene relevant to combustion and astrochemistry.
• Accurate molecular properties are crucial for understanding its role in these processes.

Purpose of the Study:

• To computationally investigate the vibrational properties of propadienylidene (H(2)CCC) and its isotopologues.
• To reassign observed infrared (IR) absorption bands based on theoretical calculations.

Main Methods:

• Explicitly correlated coupled cluster theory (CCSD(T)-F12x) was used for electronic structure calculations.
• Vibrational configuration interaction (VCI) was employed to compute accurate vibrational wavenumbers.
• Theoretical predictions were compared with experimental infrared matrix isolation spectroscopy data.

Main Results:

• The symmetric CH stretching vibration (ν(1)) of H(2)CCC is predicted at 2984 cm(-1).
• Observed IR bands at 3049.5 and 3059.6 cm(-1) are reassigned to the combination tone ν(2) + ν(4).
• Specific IR bands were assigned to fundamental vibrations (ν(6) and ν(8)) of HDCCC.

Conclusions:

• The study provides accurate vibrational wavenumbers for propadienylidene and its isotopologues.
• Reassignment of experimental IR bands enhances the understanding of propadienylidene spectroscopy.
• A recommended value for the zero-point vibrational energy of H(2)CCC was determined.