Design and Applications of Single-Component Radical Conductors

To achieve single-component organic conductors with metallic conductivity has been one of the most exciting goal in field conductors. Generally, materials are electrical insulators because electrons paired, and band gap between HOMO LUMO is large. Besides, lack efficient molecular orbital overlap may lead to a small bandwidth materials. Organic radicals can extremely low large by chemical modulations fine tuning intermolecular radical interactions, which makes compounds very promising (SCRCs). In last two decades, SCRCs even show behavior under ambient conditions, increases from 10−6 over 102 S cm−1. This review timely summarizes recent progresses design their applications electronics, inspire further explorations SCRCs. conducting have garnered considerable research attention material sciences shown immense potential development advanced electronic devices. External doping enable charge-transfer different components regarded as general way fabricate However, inevitably leads several challenging issues such efficiency, doping-induced changes microstructure, poor stability, limits application electronics. Developing provides an interesting avenue address those realize novel applications. As generally exhibit bandwidth, obtaining conductor still critical challenge. modulations, spin-spin interactions among enhance overlap, greatly facilitates carrier transport. Consequently, this minireview progress that complement silicon technologies modern microelectronic The integration property, flexibility, solution processability stimulated rapid electronics.1Heeger A.J. Semiconducting polymers: fourth generation polymeric (nobel lecture).Angew. Chem. Int. Ed. 2001; 40: 2591-2611Crossref PubMed Scopus (1348) Google Scholar usually paired highest occupied orbitals (HOMOs) lowest unoccupied (LUMOs) too generate free charge carriers. 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Boudouris B.W. nonconjugated polymer glass conductivity.Science. 2018; 359: 1391-1395Crossref (111) oxidation-reduction reaction also Second, tight inter (intra)-molecular radical-radical formation π-dimer intra-chain-like compact π-π stacking two-dimensional (2D) modes increase decrease activation energy, excessively strong σ-dimer σ-polymer, breaks original π-system, impeding Third, hydrogen-bonding-facilitating intramolecular carriers, heavy atoms causing enhancement atomic fast redox increasing rate transportation non-conjugated should considered while designing During significantly increased >102 cm−1, they These electrical, magnetic, optical characteristics. advancements provided route toward simultaneously contributed applications, form focus review. Because limited space, strongly encouraged read previous reviews more details.11Oakley PLY NBMO entire backbone building block SCRCs.10Haddon air propensity σ-dimerization limit practical proved 1,9-dithiophenalenyl (DTPLY) fused sulfur substitution perchlorophenalenyl (PCPLY) substituted electron-withdrawing were air-stable monomeric 2).26Beer Mandal Donnadieu B. electronically stabilized radical: effect chemistry solid-state structure.Cryst. Growth Des. 7: 802-809Crossref (72) Scholar,27Koutentis P.A. Chen Cao Best T.P. Beer Brock C.P. Perchlorophenalenyl radical.J. 123: 3864-3871Crossref (128) DTPLY PCPLY insulating σDTPLY < 10–6 cm–1 σPCPLY = 10–10 cm–1. found tert-butyl (TBPLY) pentafluorophenyl (TPPLY) substitutions at β positions achieved stabilization.28Kubo Phenalenyl-based open-shell polycyclic aromatic hydrocarbons.Chem. 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Light-mediated c-c sigma-bond driven crystallization dimer.J. 126: 14297-14302Crossref (48) 34Pal Siegrist 1478-1484Crossref (73) 35Mandal Samanta Lidsky New family aminophenalenyl-based conductors: synthesis, solid properties.J. 127: 8185-8196Crossref (64) 36Pal characterization germanium (IV) derived 9-hydroxyphenalenone: X-ray tris-(9-oxophenalenone)-germanium salts.Polyhedron. 24: 2076-2083Crossref (14) 37Mandal Jensen D.W. valence bond oxygen-functionalized 128: 1982-1994Crossref (114) 38Pal Trisphenalenyl-based 2008; 130: 3942-3951Crossref (51) halves orthogonal another, prevents chain state.Figure 3Chemical Structures, Stacking, Synthetic Routes PLY-Based SCRCsShow full caption(A) List recently developed SCRCs.(B) Radical contacts monomer (P5, P7, P9–P11), (P1–P4, P6, P14), (P6), reprinted permission al.33Liao Copyright 2004 American Chemical Society, 2D (P8, P12, P13), Pal al.19Pal 2005 Association Advancement Science.(C) Schematic P5.View Large Image ViewerDownload Hi-res image Download (PPT) (A) (B) Science. (C) P5. P1–P14 obtained slow solvent diffusion reduction (P1–P14)+(BPh4−) CH3CN cobaltocene degassed dry acetonitrile. sensitive, but quite conditions 3C). Based structures P1–P14, alkyl chains heteroatoms property systematically investigated. Table 1, P5 hexyl nitrogen exhibits 5 10−2 measured using four-probe method.17Chi Small disproportionation (ΔE2−1 ΔE21/2−ΔE11/2) −0.37 V P5, indicating on-site facilitate delocalization. evidenced fact closest distance planes 3.63 Å, larger van der Waals contact (3.4 Å) C–C. Similar ΔE2−1 other (ethyl pentyl, P1–P4,30Chi octyl, P631Chi Scholar). Compared much stronger these structure. For P3 shorter butyl inter-radical 3.3 Å radius,30Chi indicates contact. (3.5 dimeric lie outside sum distances carbon atoms, suggests lattice blocks isolated consistent moderate conductivity, 2.4 although formed continuous long-range P1–P4 considerably conductivity. With longer octyl P6+(BPh4−) when exposed light.33Liao 3B, inter-plane decreases 1.6 contrast 3.4 (prepared dark condition). P6 1.1 10−5 paramagnetic property. becomes diamagnetic pair bonding. Benzyl-substituted P7 forms stacked absence causes behave 1.4 10−3 Though suitable channels calculations suggest localization separation results semiconducting behavior.34Pal Cyclohexyl-substituted P8 clearly mode.19Pal Both (3.3 radius, high-symmetry 3 10−1 value Further, temperature-independent Pauli paramagnetism, characteristic temperature-dependent magnetic π-dimer. typical thermal-activate hopping Therefore, mode clarified Anderson-modified Pauling bonding (RVB) similar lithium. Oxygen-functionalized P12 P13 RVB mode, where 1 respectively.37Mandal ScholarTable 1Electrical Properties SCRCsSCRCsEgoptical (eV)Ebandwidth (eV)Eactivation (eV)σ (S cm−1)Ref.P1aSingle crystal.0.28––1.0 10−2Chi al.30Chi ScholarP2aSingle crystal.–––1.4 10−6Chi al.31Chi