Benzobisthiadiazole-based high-spin donor–acceptor conjugated polymers with localized spin distribution

Abstract

Stable organic semiconductors (OSCs) with a high-spin ground-state can profoundly impact emerging technologies such as organic magnetism, spintronics, and medical imaging. Over the last decade, there has been a significant...

Non-Aufbau orbital ordering and spin density modulation in high-spin donor–acceptor conjugated polymers

“…It is clear from the calculated diradical character that increasing the oligomer chain length increases y 0 , as observed in other studies. 19,20 Although the analysis of MOs indicates the presence of more than two unpaired electrons in these polymers, the calculated tetraradical character is very low ( y 1 < 0.10).…”

“…5,18 However, the mechanism to control the spin distribution and alignment of unpaired electrons in molecular orbitals (MOs) is not well studied. 9,19–23…”

“…5,18 However, the mechanism to control the spin distribution and alignment of unpaired electrons in molecular orbitals (MOs) is not well studied. 9,[19][20][21][22][23] The unpaired electrons in open-shell OSCs can be in a spinpaired low-spin singlet (S = 0) ground-state or both spins can be aligned in a spin-parallel high-spin triplet (S = 1) state, overcoming the effect of double-spin polarization. 19,20,24 The relative preference for a low-and high-spin ground-state can be controlled by the electron distribution along the molecular backbone.…”

“…9,[19][20][21][22][23] The unpaired electrons in open-shell OSCs can be in a spinpaired low-spin singlet (S = 0) ground-state or both spins can be aligned in a spin-parallel high-spin triplet (S = 1) state, overcoming the effect of double-spin polarization. 19,20,24 The relative preference for a low-and high-spin ground-state can be controlled by the electron distribution along the molecular backbone. 5,9,20,25,26 The closed-shell materials with a low-spin ground-state tend to accumulate the spin density at the core of the molecular backbone, 20 whereas the open-shell materials with a high-spin ground-state show either a delocalized 19,21 or an end localized orbital topology.…”

Stable acceptor-donor-acceptor type open-shell diradical with ultra-narrow bandgap and efficient photothermal conversion

“…With different formation and stabilization mechanisms of diradicals, another emerging radical system is donoracceptor (D-A) narrow bandgap organic semiconductors. 12 Many compounds have been reported to exhibit obvious diradical character using strong electron-rich donors to combine with acceptor units such as benzo[1,2-c:4,5c']bis[1,2,5]thiadiazole [23][24][25][26][27] (BBT) and diketopyrrolopyrrole [28][29][30] (DPP). Significantly, our group revealed that it is the open-shell quinoid resonance structure of D-A-D type narrow bandgap small molecules that results in their diradical character (Figure 1B), 28,29 and further proposed the mechanism of aggregate-induced radical.…”