Asymmetric and zwitterionic Blatter diradicals

Abstract

Asymmetric diradical molecular systems with different resonance mechanisms are largely unexplored. Two conjugated asymmetric diradicals with Blatter and phenoxyl moieties (pBP and mBP) have been synthesized and studied in depth.

Variation from closed-shell to open shell electronic structures in oligothiophene bis(dioxolene) complexes

“…If coupling between the SQ SOMO orbitals (also a 2-electron, 2orbital model) in actual or effective symmetry is assumed a priori, congurational mixing between closed-and open-shell singlets is symmetry forbidden. Since there are notable examples where an expanded model is required to explain the electronic structure and the nature of the radical-radical exchange interaction in biradical systems, 21,[57][58][59][60][61][76][77][78][79][80] we have minimally expanded the 2-electron, 2-orbital model to include a doublyoccupied bridge orbital that provides a mechanism for understanding the nature of open-shell singlet states that congurationally mix with quinoidal states. 21,[57][58][59][60][61]67,77,78 With respect to the role of the thiophene bridge units in dening the ground state electronic and geometric structure of the SQ-Th n -SQ series, the explicit consideration and addition of a single bridge-orbital reveals how open-shell and low-energy closed-shell singlet congurations (e.g., 1 A OS and 1 A CS , respectively; Fig.…”

“…If coupling between the SQ SOMO orbitals (also a 2-electron, 2-orbital model) in actual or effective symmetry is assumed a priori , configurational mixing between closed- and open-shell singlets is symmetry forbidden. Since there are notable examples where an expanded model is required to explain the electronic structure and the nature of the radical–radical exchange interaction in biradical systems, 21,57–61,76–80 we have minimally expanded the 2-electron, 2-orbital model to include a doubly-occupied bridge orbital that provides a mechanism for understanding the nature of open-shell singlet states that configurationally mix with quinoidal states. 21,57–61,67,77,78…”

Zwitterionic Open‐Shell Singlet Diradical with Solvent‐Dependent Singlet–Triplet Energy Gap

“…On the basis of these backgrounds, we focused on zwitterionic diradicals. [13][14][15][16][17][18][19][20][21] We envisaged that zwitterions composed of an electron-donating anion and an electronaccepting cation would resonate with singlet diradical canonical structures and have a small ΔE ST . Their singlet states would have larger dipole moments than their triplet states and would be more stabilized in polar solvents than their triplet states.…”

“…On the basis of these backgrounds, we focused on zwitterionic diradicals [13–21] . We envisaged that zwitterions composed of an electron‐donating anion and an electron‐accepting cation would resonate with singlet diradical canonical structures and have a small Δ E ST .…”

Bi-Blatter diradicals: convenient access to regioisomers with tunable electronic and magnetic properties

“…2) and a moderate diradical index y = 0.63. 58 The high propensity of benzo[e] [1,2,4]triazinyl for spin delocalization was used to stabilize an open-shell structure in phenoxy diradicals M and N. 59 These and other [60][61][62] results demonstrate a significant potential of the benzo[e] [1,2,4]triazinyl as a structural element of a broad class of chemically stable diradicals with controllable electronic and magnetic properties.…”