Auxiliary Atomic Relay Center Facilitates Enhanced Magnetic Couplings in Blatter’s Radical

Abstract

The recent accomplishments in obtaining strong ferromagnetic exchange interactions in organic diradicals have made the field quite fascinating and even more promising toward its technological applications. In this context, herein, we report a unique combination of remarkably strong ferromagnetic exchange interactions coupled with molecular rigidity, utilizing superstable Blatter's radical as a spin source. The planar analogues of the parent Blatter's radical obtained by annulation with a chalcogen coupled to nitronyl nitroxide (NN) are investigated using density functional theory along with the wave function-based multiconfigurational self-consistent field methods, for example, complete active space self-consistent field (CASSCF)−Nelectron valence state perturbation theory (NEVPT2). The calculations reveal phenomenal modulation in exchange couplings upon annulation such that remarkably strong ferromagnetic interactions are realized especially for a certain class of the Blatter-NN diradicals. The modulation of spin−spin interactions is rationalized by variation in spin density distribution and molecular torsional angles. We demonstrate that annulation in OMMs opens an additional coupling pathway via auxiliary X-atom acting as the atomic relay center which strongly manipulates the magnitude of exchange couplings.

Predicting Magnetic Coupling and Spin-Polarization Energy in Triangulene Analogues

“…For example, the predicted J values for TRI dimer are −10.08, −10.53, and −6.76 meV using Noodleman’s, Yamaguchi’s, and Ruiz’s methods, respectively, in comparison to the reference value of 7.88 meV. This overestimation of J , as predicted by Noodleman’s and Yamaguchi’s approaches, has been consistently reported in the literature, particularly for organic diradical systems. − Consequently, scaling factors of 0.3–0.5 have been employed to align with experimental J values. − As demonstrated in Figure S26, Tables S1, S2, and , J predictions derived from Noodleman’s and Yamaguchi’s methods exhibit larger MAEs and mean relative errors (MREs) than those obtained using Ruiz’s approach. For example, with B3LYP, PBE0, and M06-2X functionals, the MAEs are 29.60, 34.43, and 21.75 meV for Noodleman’s method, 25.92, 34.62, and 21.86 meV for Yamaguchi’s method, and 13.38, 11.74, and 12.66 meV for Ruiz’s approach.…”

Predicting Magnetic Coupling and Spin-Polarization Energy in Triangulene Analogues

“…This overestimation of J, as predicted by Noodleman's and Yamaguchi's approaches, has been consistently reported in the literature, particularly for organic diradical systems. [65][66][67] Consequently, scaling factors of 0.3-0.5 have been employed to align with experimental J values. [68][69][70] As demonstrated in Figure S27, Tables S1 approach.…”

“…Thus, at least from a numerical perspective, Ruiz's method appears more suitable for extracting J from BS-DFT for these metal-free systems. [66][67][71][72] Hereafter, the detailed analysis of the functionals' performance will be grounded in the results obtained using Ruiz's approach.…”

Proton-transfer regulated magnetic coupling characteristics in Blatter-based diradicals

“…35 There has been a recent surge in designing and synthesizing Blatter radicals, due to their remarkable air, moisture, optical and thermal stability which can be preserved for up to thirty years under ambient conditions, as well as intriguing magnetic properties, and thus their prospects as novel high spin magnetic molecules are excellent. [36][37][38][39] They were first prepared by Blatter and co-workers in 1968. 40 Over the past few years, Koutentis et al introduced various easy synthetic strategies that provide easy access to such superstable Blatter radicals.…”