Novel Mechanisms to Tune Electronic Characteristics in Small-Molecule 
Organic Semiconductors
Eric T. Strand, Joshua E. Barker, Justin J. Dressler, and Michael M. Haley*
Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403-1253, USA; estrand@uoregon.edu
Promise of Organic Semiconductors y : PUHF/6-311G*anti-IIDBT syn-IIDBT 0ΔEST: (SF-NC-)TDDFT syn, anti-IBFBT
PBE50/6-311G*
y0 = 0.61
ΔEST = -8.77 kcal/mol
Gate syn-IIDBT
Dielectric
OSC y = 0.66 syn, anti-IBFBT-sulfoneSource Drain 0
ΔEST = -8.06 kcal/mol
Substrate • Reported in 2018, anti-IIDBT showed high diradical character with a relatively high • Asymmetric scaffold incorporating heteroatoms and 
Transistor Implementation singlet-triplet energy gap (ΔE ). sulfonation locations around the s-indacene core has yet to ST
• Modulating the direction of fusion of terminal benzothiophene units was expected to be explored. 
• Organic semiconductors possess inherent advantages over 
increase electron delocalization around the core system. • IBFBT lacks symmetry on three fronts: fusion directions, 
their current inorganic counterparts. • This in turn increases diradical character, as denoted by calculated y values, and heteroatom incorporation, and sulfonation. 0
• Manufacture is much less energetically harsh, and high 
lowers the singlet-triplet energy gap. • Intriguingly, IBFBT may act as a donor-acceptor system and exhibit ”push-pull” 
solubility enables unique processing techniques.
Synthesis: characteristics which may further act as a mechanism to tune electronic • Solution processing and roll-to-roll printing promise easier characteristics. 
device fabrication. Strand, E. T.; Manuscript in preparation. 2020.
• Bottom-up synthesis of small molecule semiconductors allows 
for high modularity to tailor specific electronic applications. Late-Stage Modification
• Tuning these systems modulates important electronic properties SO SO
such as frontier molecular orbitals. HO HO 1. (COCl)2, DMF, DCM Tunes Molecular OrbitalsOH 1. (COCl)2, DMF, DCM
• OHEstablishing structure-property relationships will be important for 2. AlC2l.3 ,A DlCClM3, DCMO
S O
optimizing these molecules for application in electronic devices. S
Köhler, A.; Bässler, H. Electronic Processes in Organic Semiconductors, 1st Ed.; Wiley-VCH Verlag GmbH; Weinheim, 2015.
Ideal Characteristics Project Diradical HOBr S SS S
OH
y ΔEST
Closed Shell Open Shell Open Shell
Singlet Triplet Indeno[1,2-b]fluorene
Br
HO Br , Fe • DHO2 iradical chBarracter is defined as molecular possession of 
OH AcOH, reflux, 72 h Br OH
two unpaBrired electrons, which interact to produce a single 
Br
HO Br spin state.Sn (mossy) HO Br Barker, J. E.; et al. J. Am. Chem. Soc. 2019.
Br OH AcOH, reflux, 72 h • InBcrreased diradical character leads to favorable Dressler, J. J.; et al. Nat. Chem. 2018, 10, 1134-1140.OH
anti-Dinaphthoindacene Br
Avg. μ = 4.72 ± 1.97 cm2 V-1 s-1 characteristics such as decreased HOMO-LUMO energy 
Max. μ = 7.12 cm2 V-1 s-1
Br Tf O N
gaps. Characterization
• HODegree to which molecule e2 xists TfO Br
Br OH DCM 0 oC, 24 h
• Many diradical molecules are known, but this phenomenon tBu tBu tBu
as a diradical in favor of Br OTfstill is not well understood.
HOMO aromatizing its core is kBnpion wn as • Our lab has since aimed to build a library of analogues to HS R H S S
its TdfOiradical ch S S SBarracter index, y0.Pd(II)Cl2(PPh3
OTf f
)2urther optimize elecBrtronic characteristics. H
Pd2(dba)3, SPhos, Zn(CN) CN2 H R• Slip-stacking in the soKli2dC Os3t, aTotleue ne, H2O 90 oC, 3 h Br
TfO Wet DMF
Br OTf
NC
enhances conductivity through • Our future plans include continued work toward the synthesis of a wide variety of tBu tBu tBu
analogues to better identify properties for optimization of organic semiconductors.
LUMO increased orbitalO oTfverlap, wPdhic2(dbah) 3, SPhos, Zn(CN) CN2
OTf CN • Shifted Raman spectrum, red- Strand, E. T.; Manuscript in preparation. 2020.Pd2(dba)3, SPhos, Zn(CN)is crTufOcial for electron mobility.
2
Wet DMF O syn-IIDBT
TfO Br Wet DMF
NC
NC shifted UV-VIS absorbance, and 
O • Magnetic properties, governn-BuLi, DMF*LC-RBLYP/6–311G(d) ed 
H2SO4 OH Brby THF -78 oC, 24 h
easier population of the triplet state 
HO DEST, allow for access of DiOnaphthoindacene Diindenoanthracene Acknowledgementsreflux anti-IIDBT in HT-SQUID measurements 
O desirable electronic states. Chase, D. T.; et al. Angew. Chem. Int. Ed. 2011, 50, 1127-1130. The authors would like to thank the National Science Foundation, the University of Oregon, Frederickson, C. K.; et al. J. Am. Chem. Soc. 2016, 138, 16827-16838.
Dressler, J. J.; et al. Nat. Chem. 2018, 10, 1134-1140.
ORudebusch, G. E.; et al. Nat. Chem. 2016, 8, 753-759. corroborate that syn-IIDBT and the numerous collaborators including:
O
H Ar2SO4
H2SO
Ar OH
4 possesses a lower DE than anti-HO OH anti-IDBT ST Nakano, M. Department of Materials Engineering Science, Graduate School of Engineering Moredfluxrefluxular SHOOynthetic Tuning IIDBT and exhibits higher diradical Science, Osaka University, Toyonaka, Osaka, Japan.Ar
3 Ar
O
2 Ar character. Casado, J. Department of Physical Chemistry, University of Málaga, Málaga, Spain.
Ar
1 Heterocycle fusion Ar Ar
Ar S syn-IIDBT Petrukhina, M. Department of Chemistry, University of Albany, State University of New 
Ar S
Ar 3 Ar =                , Removal of steric protection at York, Albany, NY, USA.
2 3 Ar Ar Ar
1 = anti 2 Ar Ar Ar
1 Ar highly reactive radical centers 2 = linear without whom this work would not be possible.
3 = syn Pi-expansion 1
Ar produces syn-IIDBT-H2.
Ar Ar
Ar
1 = anti
21 = = l iannetair
32 = = s lyinear syn-BFF
Barker, J. E.; et al. J. Am. Chem. Soc. 2019. 3 = syn Barker, J. E.; et al. J. Am. Chem. Soc. 2019.Dressler, J. J.; et al. Nat. Chem. 2018, 10, 1134-1140. NSF CHE-1565780