Elucidation of Intramolecular Through‐Space Electronic Communication in a Propeller‐Shaped Molecule

Abstract

An ovel p-extended trinaphtho [3.3.3]propellane (TNP) derivative was prepared and through-space electronic communication in its radical cation species was characterized by electrochemicala nd spectroscopicm ethods. Cyclic voltammetry and UV/Vis-NIR titrations suggested weak electronic communication among the three aromatic rings.V ariable-temperature ESR measurements of the radical cation showed ad rastic change in the spectrai nt he range of 230-180K,i ndicating hoppingtype spin delocalization that would originate from migration of ac ounter anion.Through-space interactions betweenc ofacially aligned p-electron systems have played an important role in organic semiconductors such as organic field-effect transistors and photovoltaic devices. Compared with typical p-electron systemsw ith ap lanar scaffold, in propeller-shaped p-electrons ystems such as triptycene [1,2] and trinaphtho [3.3.3]propellane (TNP), [3] in which three aromatic rings are cofacially arranged at an angle of about 1208,t he three aromatic rings are able to interact with each other by spatial overlap of their molecular orbitals. In addition, chemical modification such as p-fusion or the introduction of substituents on triptycene or TNP induces as trong p-stacking interaction that leads to two-dimensional (2D) molecular assemblies, [4][5][6][7][8] and therefore, propeller-shaped p-electron systems are considered as strong candidates of molecular components for novel 2D electronic materials. Previously we reported af acile methodf or the synthesis of TNPa nd its p-extension.[8] It is notable that mixingo ft he p-extended TNPs (that is, trifluorantheno [3.3.3]propellanes) with organic acceptors gave 2D molecular assemblies with ah oneycomb lattice of charge-transfer complexes.A lthough we werec urious to characterizet he electronic communication among three the fluoranthene moieties of the charged species experimentally,t he poor solubility of the radical cation speciesi no rganic solvents hampered spectroscopic analyses.T oo vercome the solubility problem, we decided to introduce ethoxy groups on the fluoranthene moieties. Here, we report the synthesis of ah exaethoxy derivative( 3)o ft rifluorantheno[3.3.3]propellane and the investigationo fs pin delocalization in its radical cation species (3 · + )b yelectrochemical and spectroscopicmethods. The starting material, TNP, [8] was prepared by am odified procedure in which hot tolueneasawashing solvent in apurification stepw as replacedb ya cetone. Bromination of TNP followed by Suzuki-Miyaura coupling and as ubsequenti ntramolecular Heck-type reactionw ith the aid of microwave irradiation afforded the target compound 3,a ss hown in Scheme 1. In the final step, ah igh reaction temperature (180 8C) and the use of distilledD BU were essential for the high yield of the product.The structure of 3 was determined by single-crystal X-ray diffraction study ( Figure S6, Supporting Information).[9] The SQUEEZE subroutine of PLATON [10] was used because the refinementf or the structure of solvent molecule wa...

Synthesis and Electronic Properties of Triperyleno[3.3.3]Propellanes: Towards Two‐Dimensional Electronic Structures

“…It is notable that the mixing of π‐extended TNPs (that is, trifluorantheno‐[3.3.3]propellanes, TFAPs, Scheme ) with organic acceptors gave 2D molecular assemblies with a honeycomb lattice of charge transfer complexes. The electronic interaction between fluoranthene moieties in a radical cation species of TFAP was investigated by using an ethoxy derivative of TFAP (EtO‐TFAP), which showed hopping‐type spin delocalization …”

“…Preparation of 4 a and 4 b was carried out by multi‐step synthesis from 1 (Scheme ). Tribromo compound 2 , which was prepared from 1 , was converted to 3 by Suzuki‐Miyaura coupling with 8‐chloro‐1‐naphthylboronic acid in a good yield.…”

“…The deference in the splitting is related to the degree of spatial overlap of MOs (see Figures S1 and S2, Supporting Information). Therefore, the spin in 4 b .+ is fully delocalized over three perylene moieties, whereas that in EtO‐TFAP .+ is localized on one fluoranthene moiety …”

Homoconjugation enhances the photophysical and electrochemical properties of a new 3D intramolecular charge transfer iptycene displaying deep blue emission

“…This is indicative of electronic communication between the fins, in-line with literature precedent. 7,8 The extinction coefficients for 1 are notably larger than for 2. Specifically, we note that the ICT band is ca.…”

“…5,6 The three fused benzene "fins" of triptycene are able to communicate through the spatial overlap of their molecular orbitals, termed homoconjugation. 7,8 These properties have been broadly exploited in the development of molecular motors, [9][10][11] metal organic frameworks (MOFs) 12,13 , porous organic crystals, [14][15][16] non-fullerene acceptors for OPVs [17][18][19][20] and catalysts. [21][22][23] The ICT methodology has been applied to some triptycene derived compounds which are shown in Figure 1.…”