Normal & reversed spin mobility in a diradical by electron-vibration coupling

Abstract

Abstractπ−conjugated radicals have great promise for use in organic spintronics, however, the mechanisms of spin relaxation and mobility related to radical structural flexibility remain unexplored. Here, we describe a dumbbell shape azobenzene diradical and correlate its solid-state flexibility with spin relaxation and mobility. We employ a combination of X-ray diffraction and Raman spectroscopy to determine the molecular changes with temperature. Heating leads to: i) a modulation of the spin distribution; and ii) a “normal” quinoidal → aromatic transformation at low temperatures driven by the intramolecular rotational vibrations of the azobenzene core and a “reversed” aromatic → quinoidal change at high temperatures activated by an azobenzene bicycle pedal motion amplified by anisotropic intermolecular interactions. Thermal excitation of these vibrational states modulates the diradical electronic and spin structures featuring vibronic coupling mechanisms that might be relevant for future design of high spin organic molecules with tunable magnetic properties for solid state spintronics.

Simulation of polymeric mixed ionic and electronic conductors with a combined classical and quantum mechanical model

“…Calculations are accelerated more than two-fold by including in the QM part only a truncated -OCH 3 side chain. We chose B3LYP, the most widely employed functional among the hybrid GGA functionals, since it has been demonstrated to lead to vibronic spectra in good agreement with experimental data also for charged, 72,73 doped 74 or radical species, 75 ensuring that the charge distribution is properly described. Nevertheless, we remark that any further improvement in DFT methods for QM/MM step can be readily included in our workflow.…”

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

“…Conjugated p-systems that possess biradical character [1][2][3][4][5][6] hold tremendous promise as novel architectures for molecular and molecule-based materials due to their remarkable magnetic, optical, and electronic properties. As a result, these p-conjugated biradical systems are expected to contribute to the organic semiconductor, [7][8][9] singlet ssion, 1 break junction, 10 spintronics, 11,12 non-linear optical, and exchange-coupled electron spin qubit [13][14][15][16][17] knowledge base and function as models for understanding the effects of dipolar coupling and molecular vibrations on spin relaxation.…”

The smallest oligothiophene diradicals by asymmetric substitution of quinoidal cores

“…In recent years, diradicals have received growing attention from scientists because of their interesting electronic, magnetic and optical properties. [1][2][3][4][5] The optical band gap of diradical molecules based on conjugated molecules is often narrow, so they are generally good candidates for use as near-infrared absorbing dyes. [6][7][8][9][10] These classes of fully conjugated organic diradicals violate one of Hund's rules in the sense that the high spin state (triplet) is not favoured over the singlet state, given that the multiconfigurational mixing in the latter provides only partial bonding between the unpaired electrons.…”