Abstract
Three crystalline N-trimethyltriindoles endowed with different functionalities at 3, 8 and 13 positions (either unsubstituted or with three methoxy or three acetyl groups attached) are investigated, and clear correlations between the electronic nature of the substituents and their solid-state organization, electronic properties and semiconductor behavior are established. The three compounds give rise to similar columnar hexagonal crystalline structures; however, the insertion of electron-donor methoxy groups results in slightly shorter stacking distances when compared with the unsubstituted derivative, whereas the insertion of electron-withdrawing acetyl groups lowers the crystallinity of the system. Functionalization significantly affects hole mobilities with the triacetyl derivative showing the lowest mobility within the series in agreement with the lower degree of order. However, attaching three methoxy groups also results in lower hole mobility values in the OFETs (0.022 vs. 0.0014 cm2 V−1 s−1) in spite of the shorter stacking distances. This counterintuitive behavior has been explained with the help of DFT calculations performed to rationalize the interplay between the intramolecular and intermolecular properties, which point to lower transfer integrals in the trimethoxy derivative due to the HOMO wave function extension over the peripheral methoxy groups. The results of this study provide useful insights into how peripheral substituents influence the fundamental charge transport parameters of chemically modified triindole platforms of fundamental importance to design new derivatives with improved semiconducting performance.
Highlights
In the last few years, the heptacyclic molecule 10,15- dihydro-5H-diindolo[3,2-a:30,20 -c]carbazole has been identified as a highly promising p-type organic semiconductor in the construction of electronic and optoelectronic devices
Owing to its excellent hole-transporter ability, numerous triindole-based materials have been successfully incorporated in OFETs [1,2,3,4] and dye-sensitized [5,6,7] or perovskite-based [8,9] solar cells exhibiting excellent performances
Two new crystalline N-trimethyltriindoles endowed with different substituents at
Summary
In the last few years, the heptacyclic molecule 10,15- dihydro-5H-diindolo[3,2-a:30 ,20 -c]carbazole ( known in the literature as triindole or triazatruxene) has been identified as a highly promising p-type organic semiconductor in the construction of electronic and optoelectronic devices. The triindole core, has been identified as an excellent aromatic core in the construction of high mobility p-type semiconducting discotic liquid crystals. By attaching a number of peripheral flexible chains to this molecule, it is possible to induce in this heptacyclic platform columnar mesomorphism giving rise to liquid crystalline materials that exhibit excellent hole mobilities values and can be processed from solution or melt [17,18,19]. Molecules 2022, 27, 1121 a number of peripheral flexible chains to this molecule, it is possible to induce in this hep of tacyclic platform columnar mesomorphism giving rise to liquid crystalline materials that exhibit excellent hole mobilities values and can be processed from solution or melt [17,18,19]. Mesomorphism can be induced in this core by means of elecInterestingly, can be core induced this core by means of electronic factors
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