TY - JOUR
T1 - N-Dopants Based on Dimers of Benzimidazoline Radicals
T2 - Structures and Mechanism of Redox Reactions
AU - Zhang, Siyuan
AU - Naab, Benjamin D.
AU - Jucov, Evgheni V.
AU - Parkin, Sean
AU - Evans, Eric G.B.
AU - Millhauser, Glenn L.
AU - Timofeeva, Tatiana V.
AU - Risko, Chad
AU - Brédas, Jean Luc
AU - Bao, Zhenan
AU - Barlow, Stephen
AU - Marder, Seth R.
N1 - Publisher Copyright:
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
PY - 2015/7/1
Y1 - 2015/7/1
N2 - 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 C-C 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 (D2) dissociation and of D2-to-A electron transfer, D2 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+/0.5D2 redox potentials - the effective reducing strengths of the dimers - vary little within the series (ca. -1.9V vs. FeCp2+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D+/0 potential and D2 dissociation energy. The implications of these findings for use of these dimers as n-dopants, and for future dopant design, are discussed. Benzimidazoline dimers are effective n-dopants for organic electronics. Vis-NIR kinetics help elucidate the mechanisms by which they react with acceptors (A); these depend on both the dimer and A and can be rationalized using electrochemistry and dissociation energies (see scheme). X-ray diffraction shows central C-C bond lengths do not correlate with dissociation energy.
AB - 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 C-C 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 (D2) dissociation and of D2-to-A electron transfer, D2 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+/0.5D2 redox potentials - the effective reducing strengths of the dimers - vary little within the series (ca. -1.9V vs. FeCp2+/0) (Cp=cyclopentadienyl) due to cancelation of trends in the D+/0 potential and D2 dissociation energy. The implications of these findings for use of these dimers as n-dopants, and for future dopant design, are discussed. Benzimidazoline dimers are effective n-dopants for organic electronics. Vis-NIR kinetics help elucidate the mechanisms by which they react with acceptors (A); these depend on both the dimer and A and can be rationalized using electrochemistry and dissociation energies (see scheme). X-ray diffraction shows central C-C bond lengths do not correlate with dissociation energy.
KW - density functional calculations
KW - doping
KW - reaction mechanism
KW - redox chemistry
KW - structure elucidation
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U2 - 10.1002/chem.201500611
DO - 10.1002/chem.201500611
M3 - Article
C2 - 26088609
AN - SCOPUS:84937001181
SN - 0947-6539
VL - 21
SP - 10878
EP - 10885
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 30
ER -