Germanium, carbon‐germanium, and silicon‐germanium triangulenes

Abstract

A series of germanium-containing triangular molecules have been studied by density functional theory (DFT) calculations. The triangulene topology of the compounds provides for their high-spin ground states and strong sign alternation of spin density and atomic charge distributions. High values of the exchange coupling constants witness ferromagnetic ordering of electronic structures of all studied triangulenes. The compounds bearing more electronegative atoms in a-positions of the triangular networks possess higher aromatic character and stronger ferromagnetic ordering.

Carbon-[n]Triangulenes and Sila-[n]Triangulenes: Which Are Planar?

“…From an X-ray study of the 2,5,8-tritert-butylphenalenyl radical in the crystalline state, 20 the phenalenyl fragment is known to have a slightly distorted D 3h symmetry. The next family member is [3]triangulene or Clar hydrocarbon, 21 whose triplet state has been shown theoretically to have an energy of 20 kcal mol −1 lower than its singlet state. 22 DFT calculations 23 predicted triangulenes with high-spin ground states up to n = 15.…”

“…According to the latter, 2 a planar structure is assumed whenever the substitution fills only all b-atom positions. Conversely, only the first two hybrid structures for [2]triangulene and [3]triangulene retained the highest D 3h symmetry when the substitutions occupied all aatom positions: the symmetry was reported 2 to be reduced for all other [n]triangulenes, with the planar D 3h structures of the silaa- [4]triangulene and - [5]triangulene predicted as saddle points of indexes 2 and 3 [and destabilized relative to the corresponding minima by 9.2 and 9.5 kcal mol −1 without the vibrational zero-point-energy (ZPE) correction]. Such predictions are at the DFT level with the B3LYP functional, and hence, one wonders whether they afford sufficient realism.…”

“…The family of [ n ]­triangulenes attracts much interest due to exhibiting magnetic properties and hence are potential components of molecular memory devices. − While many nanographenes are closed-shell, the title ones have topologies that lead to open-shell electronic structures. Due to frustration with their conjugated networks, they assume high-spin states and show magnetic properties that attract attention.…”

The role of electrostatic potential in the translocation of triangulene across membranes

“…27,28 The rst group of triangulene atomic charges are calculated by DFT which is called ESP. 29 The second group of triangulene atomic charges are acquired from ref. 16, the partial charges of hydrogen atoms and the linked carbon atoms were set to +0.115e and −0.115e, while carbon atoms away from the edge remained neutral.…”

Can the quasi‐molecule concept help in deciphering planarity? The case of polycyclic aromatic hydrocarbons

“…Because they are not the result of an actual chemical break‐up, their quasi‐molecular nature confers them validity once satisfying the spin‐spatial correlation rules; thence, there is freedom in their choice. Following paper I on six and eight ‐electron bare rings of group‐XIV elements, one may then wonder whether hybrid [n]triangulenes (where carbon atoms are replaced by other group XIV elements [90–92], or any other) are planar. A preliminary DFT/B3LYP study on () has shown that the outcoming sila‐radicals are occasionally planar, offering an interesting avenue for their exploration as well as even larger sila‐[n]triangulenes.…”