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Alkyl- π engineering in state control toward versatile optoelectronic soft materials

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ABSTRACT

Organic π-conjugated molecules with extremely rich and tailorable electronic and optical properties are frequently utilized for the fabrication of optoelectronic devices. To achieve high solubility for facile solution processing and desirable softness for flexible device fabrication, the rigid π units were in most cases attached by alkyl chains through chemical modification. Considerable numbers of alkylated-π molecular systems with versatile applications have been reported. However, a profound understanding of the molecular state control through proper alkyl chain substitution is still highly demanded because effective applications of these molecules are closely related to their physical states. To explore the underlying rule, we review a large number of alkylated-π molecules with emphasis on the interplay of van der Waals interactions (vdW) of the alkyl chains and π–π interactions of the π moieties. Based on our comprehensive investigations of the two interactions’ impacts on the physical states of the molecules, a clear guidance for state control by alkyl-π engineering is proposed. Specifically, either with proper alkyl chain substitution or favorable additives, the vdW and π–π interactions can be adjusted, resulting in modulation of the physical states and optoelectronic properties of the molecules. We believe the strategy summarized here will significantly benefit the alkyl-π chemistry toward wide-spread applications in optoelectronic devices.

No MeSH data available.


AFM (a) and high-resolution scanning tunneling microscopy (STM) (b) images of 1a on HOPG spin-coated from a CHCl3 solution. (c) Schematic illustration showing the molecular organization of 1a in the lamellae. (d) Cyclic voltammogram of 3a on HOPG (0.1 M tetra-n-butylammonium perchlorate, acetonitrile (CH3CN), Ar atmosphere, scan rate 0.1 V s−1, 20 °C). Reprinted with permission from T Nakanishi et al 2006 J. Am. Chem. Soc.128 6328, © 2006 American Chemical Society.
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Figure 7: AFM (a) and high-resolution scanning tunneling microscopy (STM) (b) images of 1a on HOPG spin-coated from a CHCl3 solution. (c) Schematic illustration showing the molecular organization of 1a in the lamellae. (d) Cyclic voltammogram of 3a on HOPG (0.1 M tetra-n-butylammonium perchlorate, acetonitrile (CH3CN), Ar atmosphere, scan rate 0.1 V s−1, 20 °C). Reprinted with permission from T Nakanishi et al 2006 J. Am. Chem. Soc.128 6328, © 2006 American Chemical Society.

Mentions: The interaction between the appended alkyl chains of alkylated-π molecules and solid substrates, highly oriented pyrolytic graphite (HOPG) in particular, was reported to be able to drive the corresponding π molecules to form lamellae and other complicated ordered structures and therefore organize into epitaxially ordered molecular patterns [41, 42]. This technique, although widely utilized for the establishment of 2D alignments [43, 44], was seldom employed for the construction of 1D architectures [45]. Taking into consideration the significance of the 1D C60 structure in electronic nanodevices, our group applied the technique to fabricate perfectly aligned 1D C60 nanowires by spin-coating a dilute CHCl3 solution of compound 1a onto HOPG surfaces (figure 7(a)) [46]. The nanowires, with the C60 heads locating at the center in a zigzag fashion and the substituted alkyl chains stretching outward (figure 7(b)), possess lengths exceeding several hundred of nanometers. The periodicity of the nanostripes corresponds well to twice the molecular length of 1a, revealing a perfect lamellar structure with fully extended alkyl chains of all-trans conformation (figure 7(c)).


Alkyl- π engineering in state control toward versatile optoelectronic soft materials
AFM (a) and high-resolution scanning tunneling microscopy (STM) (b) images of 1a on HOPG spin-coated from a CHCl3 solution. (c) Schematic illustration showing the molecular organization of 1a in the lamellae. (d) Cyclic voltammogram of 3a on HOPG (0.1 M tetra-n-butylammonium perchlorate, acetonitrile (CH3CN), Ar atmosphere, scan rate 0.1 V s−1, 20 °C). Reprinted with permission from T Nakanishi et al 2006 J. Am. Chem. Soc.128 6328, © 2006 American Chemical Society.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036497&req=5

Figure 7: AFM (a) and high-resolution scanning tunneling microscopy (STM) (b) images of 1a on HOPG spin-coated from a CHCl3 solution. (c) Schematic illustration showing the molecular organization of 1a in the lamellae. (d) Cyclic voltammogram of 3a on HOPG (0.1 M tetra-n-butylammonium perchlorate, acetonitrile (CH3CN), Ar atmosphere, scan rate 0.1 V s−1, 20 °C). Reprinted with permission from T Nakanishi et al 2006 J. Am. Chem. Soc.128 6328, © 2006 American Chemical Society.
Mentions: The interaction between the appended alkyl chains of alkylated-π molecules and solid substrates, highly oriented pyrolytic graphite (HOPG) in particular, was reported to be able to drive the corresponding π molecules to form lamellae and other complicated ordered structures and therefore organize into epitaxially ordered molecular patterns [41, 42]. This technique, although widely utilized for the establishment of 2D alignments [43, 44], was seldom employed for the construction of 1D architectures [45]. Taking into consideration the significance of the 1D C60 structure in electronic nanodevices, our group applied the technique to fabricate perfectly aligned 1D C60 nanowires by spin-coating a dilute CHCl3 solution of compound 1a onto HOPG surfaces (figure 7(a)) [46]. The nanowires, with the C60 heads locating at the center in a zigzag fashion and the substituted alkyl chains stretching outward (figure 7(b)), possess lengths exceeding several hundred of nanometers. The periodicity of the nanostripes corresponds well to twice the molecular length of 1a, revealing a perfect lamellar structure with fully extended alkyl chains of all-trans conformation (figure 7(c)).

View Article: PubMed Central - PubMed

ABSTRACT

Organic π-conjugated molecules with extremely rich and tailorable electronic and optical properties are frequently utilized for the fabrication of optoelectronic devices. To achieve high solubility for facile solution processing and desirable softness for flexible device fabrication, the rigid π units were in most cases attached by alkyl chains through chemical modification. Considerable numbers of alkylated-π molecular systems with versatile applications have been reported. However, a profound understanding of the molecular state control through proper alkyl chain substitution is still highly demanded because effective applications of these molecules are closely related to their physical states. To explore the underlying rule, we review a large number of alkylated-π molecules with emphasis on the interplay of van der Waals interactions (vdW) of the alkyl chains and π–π interactions of the π moieties. Based on our comprehensive investigations of the two interactions’ impacts on the physical states of the molecules, a clear guidance for state control by alkyl-π engineering is proposed. Specifically, either with proper alkyl chain substitution or favorable additives, the vdW and π–π interactions can be adjusted, resulting in modulation of the physical states and optoelectronic properties of the molecules. We believe the strategy summarized here will significantly benefit the alkyl-π chemistry toward wide-spread applications in optoelectronic devices.

No MeSH data available.