Linear or Cyclic? Theoretical Investigation of Astrophysically Relevant Magnesium-Bearing MgCH Carbon Chains and Related Isomers.

Magnesium-containing molecules, including MgCH, MgCH, and MgCH, have been detected in the interstellar medium, largely facilitated by their high dipole moments. However, despite great efforts, MgCH species remain elusive. Given the challenges in obtaining experimental data for these molecules, theoretical studies play a crucial role in guiding their detection. In this work, we present a theoretical analysis of MgCH isomers (n = 4-7) using density functional theory and coupled-cluster methods to identify low-lying isomers and characterize their structural and electronic properties. Our findings reveal that across the entire series investigated, the global minimum geometry is linear for even values of n, whereas for odd values, a cyclic geometry is favored. Additionally, our calculations highlight the enhanced stability of anionic MgCH systems, providing insights that could aid future astronomical detections in the interstellar medium.