Role of peripheral substitution on electronics and self-assembly of discotic semiconductors: The case of diazatruxenone

• Published in: Journal of molecular liquids 2023-11, Vol.390, p.123085, Article 123085
• Main Authors: Gámez-Valenzuela, Sergio, Benito-Hernández, Angela, Ortiz, Rocío Ponce, Golemme, Attilio, Termine, Roberto, Delgado, M. Carmen Ruiz, Gómez-Lor, Berta
• Format: Article
• Language: English
• Subjects: Charge-transport; Diazatruxenone; Mesophase; Organic electronics; Self-assembling
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2023.123085

The donor-acceptor character of diazatruxenones confers them an inherent dipole moment whose magnitude and directionality can be manipulated by appropriate functionalization. By maximizing the strength of this dipole, it is possible to induce columnar mesomorphism in this discotic platform with just two flexible alkyl chains, presumably driven by the antiparallel dipole-dipole arrangement of neighbouring molecules within the columns. [Display omitted] •Peripheral substitution significantly affects the self-assembling properties of diazatruxenones.•Functionalization influences the magnitude and directionality of the dipole moment inherent in diazatruxenones.•Peripheral electron-withdrawing groups induce mesomorphism in diazatruxenones through dipole–dipole interactions.•The antiparallel arrangement of dipoles in neighbouring diazatruxenones favors  SCLC-determined hole transport. In this paper we present two sets of diazatruxenones functionalized at the 3,8 or 2,7 positions with two phenyl rings substituted at the para positions with groups of different electronic nature. With the aim to shed light on the role of the positional isomeric effect and of the electronic nature of the attached peripheral substituents on the final properties of these systems, we have performed a joint experimental and theoretical investigation linking thermal analysis, UV–Vis spectroscopy, electrochemistry and SCLC measurements with DFT calculations. The donor–acceptor character of these molecules not only confers them an interesting amphoteric redox behaviour but also creates a significant in-plane dipole moment. We have found that the different functionalization has only a slight impact on the electronic properties of these systems but exerts a significant influence on the strength and directionality of their dipole moment with strong implications in their self-assembly. Particularly, derivatives functionalized with electron acceptors, present the highest dipole moments within the series and form stable columnar mesophases, probably driven by the antiparallel dipole–dipole arrangement of neighbouring molecules. DFT calculations confirms that cofacially stacked dimers with their dipoles opposed allow for efficient electronic couplings helping to rationalize the favourable hole mobilities determined for the 3,8-disubstituted diazatruxenones with electron-acceptor groups by means of the space charge–limited current technique.