Unveiling the quantum secrets of triel metal triangles: a tale of stability, aromaticity, and relativistic effects

Abstract

Low lying electronic states of Al3−, Ga3−, In3−, and Tl3− have been characterized using high level multiconfigurational quasi degenerate perturbation theory on the multiconfigurational self-consistent field. Among these species, the singlet Image ID:d4cp00484a-t1.gif states emerge as the predominant energy minima, displaying remarkable stability. However, within the Tl3− series, our investigation leads to the identification of the high-spin Image ID:d4cp00484a-t2.gif, as the most stable spin state, a result corroborated by previous experimental detection via photoelectron spectroscopy. Similarly, we have also identified the singlet state of In3− as the signal detected previously experimentally. By applying Mandado's rules and an array of aromaticity indicators, it is conclusively demonstrated that both the singlet and quintet states exhibit multiple-fold aromaticity, while the triplets exhibit conflicting aromaticity. Furthermore, this investigation highlights the significant impact of relativistic effects, as they enhance the stability of the Image ID:d4cp00484a-t3.gif state relative to its singlet counterpart. These findings shed new light on the electronic structures and properties of these ions, offering valuable insights into their chemical behavior and potential applications