[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

Abstract

Nanorings, which are macrocyclesp ossessing radially directed p-orbitalsh ave shown fantastic developmenti n the last ten years. Unravelling their unusuale lectronicp roperties has been one of the driving forces of this research field. However,a nd despite promising properties, their incorporationi no rganic electronic devices remains very scarce. In this work, we aim to contribute to bridge the gap between organice lectronics and nanorings by reporting the synthesis, the structurala nd electronic properties and the incorporation in an organic field-effect transistor (OFET) of ac yclic tetracarbazole, namely[ 4]cyclo-N-ethyl-2,7-carbazole( [4]C-Et-Cbz). The structural, photophysicala nd electrochemical properties have been compared to those of structurally related analogues [4]cyclo-9,9-diethyl-2,7-fluorene [4]C-diEt-F (with carbon bridges) and [8]-cycloparaphenylene [8]CPP (withouta ny bridge) in ordert os hed light on the impact of the bridging in nanorings. This work shows that nanorings can be used as an active layer in an OFET and provides a first benchmark in term of OFET characteristicsf or this type of molecules.

Theoretical Insights for Materials Properties of Cyclic Organic Nanorings

“…Prompted by the availability of the crystal structure of N , N ‐dimethylaza‐8‐CPP, DMA‐8‐CPP in the following, the semiconducting properties of this molecule has also been recently investigated [ 112 ] and compared to 6CPP, 8CPP, and 12CPP. Note that another CPP derivative, namely 4‐cyclo‐ N ‐ethyl‐2,7‐carbazole also with radially oriented π‐orbitals, has been recently incorporated [ 232 ] in an organic field‐effect transistor (OFET) with low experimental mobilities () but in agreement with those experimentally found for 10CPP [ 233 ] too. First of all, the hole and electron reorganization energies of DMA‐8‐CPP are similar, and in the case of holes, slightly higher than that calculated for undoped 8CPP, thus indicating a more favored n‐type or ambipolar performance in this case if the rest of conditions remain the same.…”

[n]‐Cyclo‐9,9‐dibutyl‐2,7‐fluorene (n=4, 5): Nanoring Size Influence in Carbon‐Bridged Cyclo‐para‐phenylenes

“…Since the first reported synthesis of nanorings (some cyclopara-phenylenes, CPPs, Chart 1, Top) in 2008, [5] such ringshaped π-conjugated macrocycles have been subject to intense research worldwide. [6][7][8][9][10] Cyclofluorenes (Chart 1, Bottom) belong to the family of bridged CPPs [1][2][3][11][12][13][14] and the first examples were reported in 2015 and 2016 by the groups of Yamago [1] and Huang. [2] In these examples, three or four fluorene units were connected together at their C2 and C7 positions to form highly strained structures.…”

[n]‐Cyclo‐9,9‐dibutyl‐2,7‐fluorene (n=4, 5): Nanoring Size Influence in Carbon‐Bridged Cyclo‐para‐phenylenes

“…This kind of MO diagram is typical of CPPs [19] and bridged CPPs with four units. [11] The absorption properties of [5]C-diBu-F appear very similar to those of its shorter analogue with two main bands: a thin and intense band at 355 nm and a large and weak one above 400 nm (Figure 4, Middle). TD-DFT analyses indicate that these bands involve the same transitions (and orbitals) as [4]C-diBu-F.…”

“…Since the first reported synthesis of nanorings (some cyclopara-phenylenes, CPPs, Chart 1, Top) in 2008, [5] such ringshaped π-conjugated macrocycles have been subject to intense research worldwide. [6][7][8][9][10] Cyclofluorenes (Chart 1, Bottom) belong to the family of bridged CPPs [1][2][3][11][12][13][14] and the first examples were reported in 2015 and 2016 by the groups of Yamago [1] and Huang. [2] In these examples, three or four fluorene units were connected together at their C2 and C7 positions to form highly strained structures.…”