Modulating the Electronic and Solid-State Structure of Organic Semiconductors by Site-Specific Substitution: The Case of Tetrafluoropentacenes.

ABSTRACT: The properties as well as solid-state structures, singlet fission, and organic field-effect transistor (OFET) performance of three tetrafluoropentacenes (1,4,8,11: 10, 1,4,9,10: 11, 2,3,9,10: 12) are compared herein. The novel compounds?10 and 11 were synthesized in high purity from the corresponding 6,13-etheno-bridged precursors by reaction with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate at elevated temperatures. Although most of the molecular properties of the compounds are similar, their chemical reactivity and crystal structures differ considerably. Isomer?10 undergoes the orbital symmetry forbidden thermal [4+4] dimerization, whereas 11 and 12 are much less reactive. The isomers 11 and 12 crystallize in a herringbone motif, but 10 prefers ?-? stacking. Although the energy of the first electric dipole-allowed optical transition varies only within 370?cm-1 (0.05?eV) for the neutral compounds, this amounts to roughly 1600?cm-1 (0.20?eV) for radical cations and 1300?cm-1 (0.16?eV) for dications. Transient spectroscopy of films of 11 and 12 reveals singlet-fission time constants (91±11, 73±3?fs, respectively) that are shorter than for pentacene (112±9?fs). OFET devices constructed from 11 and 12 show close to ideal thin-film transistor (TFT) characteristics with electron mobilities of 2×10-3 and 6×10-2 ?cm2 ?V-1 ?s-1 , respectively.

SUBMITTER: Geiger T 

PROVIDER: S-EPMC7154741 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature