Linear Extension of Anthracene via B←N Lewis Pair Formation: Effects on Optoelectronic Properties and Singlet O₂Sensitization

Abstract

The functionalization of polycyclic aromatic hydrocarbons (PAHs) via B ! NL ewis pair formation offers an opportunity to judiciously fine-tune the structural features and optoelectronic properties,tosuit the demands of applications in organic electronic devices,b ioimaging,a nd as sensitizers for singlet oxygen generation. We demonstrate that the N-directed electrophilic borylation of 2,6-di(pyrid-2-yl)anthracene offers access to linearly extended acene derivatives Py-BR (R = Et, Ph, C 6 F 5 ). In comparison to indeno-fused 9,10-diphenylanthracene,t he formal "BN for CC" replacement in Py-BR selectively lowers the LUMO,r esulting in am uchr educed HOMO-LUMO gap.A ne ven more extended conjugated system with seven six-membered rings in ar ow (Qu-BEt)i s obtained by borylation of 2,6-di(quinolin-8-yl)anthracene. Fluorinated Py-BPf shows particularly advantageous properties,i ncluding relatively lower-lying HOMO and LUMO levels,s trong yellow-green fluorescence,a nd effective singlet oxygen sensitization, while resisting self-sensitized conversion to its endoperoxide.

Tetrazole‐Functionalized Organoboranes Exhibiting Dynamic Intramolecular N→B‐Coordination and Cyanide‐Selective Anion Binding

“…Recently, the introduction of main group elements is being investigated intensively in materials science and organic electronics to access new structural scaffolds and to exploit unusual electronic effects. [8] Introduction of boron [9][10][11][12][13][14][15][16] has attracted particular interest in this regard as it can be incorporated in either the tri- [10,[17][18][19] and tetracoordinate [20][21][22][23][24][25][26][27][28][29] form, which gives rise to different electronic and chemical properties.…”

“…Compounds featuring intramolecular N,C 2 -chelated tetracoordinate boron, [29,[38][39][40][41][42][43][44][45] also exhibit increased electron affinity, and have therefore been considered as electron-transporting (n-type) materials. [20][21][22][23][24][25][26][27][28][29] Recently, they have attracted growing interest, due to promising results in organic light emitting devices, [46] n-channel organic field effect transistors, [47] and organic photovoltaic cells. [20][21][22][23][24][25][26][27] and have been used to generate compounds with helical topology, [48][49][50] A key limitation in the exploration of organoboranes is the limited choice of methods for their preparation.…”

“…Tricoordinate boron centers in pendant groups [19,30–33] or embedded within π‐systems [34–37] lead to a lowering of the Lowest Unoccupied Molecular Orbital (LUMO) and hence increased electron affinity, due to conjugation with their p z ‐orbital. Compounds featuring intramolecular N,C 2 ‐chelated tetracoordinate boron, [29,38–45] also exhibit increased electron affinity, and have therefore been considered as electron‐transporting (n‐type) materials [20–29] . Recently, they have attracted growing interest, due to promising results in organic light emitting devices, [46] n‐channel organic field effect transistors, [47] and organic photovoltaic cells [20–27] .…”