Premium
n‐Dopants Based on Dimers of Benzimidazoline Radicals: Structures and Mechanism of Redox Reactions
Author(s) -
Zhang Siyuan,
Naab Benjamin D.,
Jucov Evgheni V.,
Parkin Sean,
Evans Eric G. B.,
Millhauser Glenn L.,
Timofeeva Tatiana V.,
Risko Chad,
Brédas JeanLuc,
Bao Zhenan,
Barlow Stephen,
Marder Seth R.
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500611
Subject(s) - radical , redox , mechanism (biology) , chemistry , dopant , photochemistry , materials science , doping , organic chemistry , physics , optoelectronics , quantum mechanics
Dimers of 2‐substituted N,N′ ‐dimethylbenzimidazoline radicals, (2‐Y‐DMBI) 2 (Y=cyclohexyl (Cyc), ferrocenyl (Fc), ruthenocenyl (Rc)), have recently been reported as n‐dopants for organic semiconductors. Here their structural and energetic characteristics are reported, along with the mechanisms by which they react with acceptors, A (PCBM, TIPS‐pentacene), in solution. X‐ray data and DFT calculations both indicate a longer CC bond for (2‐Cyc‐DMBI) 2 than (2‐Fc‐DMBI) 2 , yet DFT and ESR data show that the latter dissociates more readily due to stabilization of the radical by Fc. Depending on the energetics of dimer (D 2 ) dissociation and of D 2 ‐to‐A electron transfer, D 2 reacts with A to form D + and A − by either of two mechanisms, differing in whether the first step is endergonic dissociation or endergonic electron transfer. However, the D + /0.5 D 2 redox potentials—the effective reducing strengths of the dimers—vary little within the series (ca. −1.9 V vs. FeCp 2 +/0 ) (Cp=cyclopentadienyl) due to cancelation of trends in the D +/0 potential and D 2 dissociation energy. The implications of these findings for use of these dimers as n‐dopants, and for future dopant design, are discussed.