Synthesis, Optical Properties, and Electronic Structures of Nucleobase-Containing π-Conjugated Oligomers

Abstract

The molecular recognition properties of the nucleobases instruct the formation of complex three-dimensional architectures in natural and synthetic systems; relatively unexplored is their use as building blocks for π-conjugated materials where they might mutually tune electronic and supramolecular structures. Toward this goal, an introductory set (1a-d and 2a-d) of six purine-terminated and two pyrimidine-terminated π-conjugated oligomers has been synthesized and used to develop experimental electronic and photophysical structure-property trends. Unlike 2,2':5',2″-terthiophene (TTT) derivatives 2a-d, intramolecular charge transfer dominates oligomers 1a-d bearing a 4,7-bisthienylbenzothiadiazole (TBT) spacer due to the strong electron-accepting ability of its benzothiadiazole (BTD) ring. The resulting donor-acceptor-donor systems feature lower HOMO-LUMO gaps than the terthiophene-linked nucleobases (ΔE(g) ∼ 1.8 eV vs 2.4 eV based on electrochemical measurements), and the lowest so far for π-conjugated molecules that include nucleobases within the π-framework. Experiments reveal a dependence of photophysical and electronic structure on the nature of the nucleobase and are in good agreement with theoretical calculations performed at the B3LYP/6-31+G** level. Overall, the results show how nucleobase heterocycles can be installed within π-systems to tune optical and electronic properties. Future work will evaluate the consequences of these information-rich components on supramolecular π-conjugated structure.

Guanine–oligothiophene conjugates: liquid-crystalline properties, photoconductivities and ion-responsive emission of their nanoscale assemblies

“…Five molecules consisting of N -9 alkylated guanine conjugated with phenylthiophene ( 1 ), phenylbithiophene ( 2a and 2b ) or phenylterthiophene ( 3a and 3b ) at the C-8 position of guanine were synthesised ( Scheme 3 ) based on previously reported palladium-catalysed coupling reactions 57 (ESI, Section 1 † ). The stereochemistry of N -9 alkylated 2-amino-6-benzyloxy-9-octylpurine ( 9 ), a precursor for the guanine–oligothiophene conjugates, was identified by a gHMBC 2D NMR experiment (ESI, Fig.…”

Synthesis of 5‐/8‐Halogenated or Ethynylated Lipophilic Nucleobases as Potential Synthetic Intermediates for Supramolec­ular Chemistry

“…[6] For these reasons, the development of efficient and reliable synthetic routes to modified nucleobases as versatile building blocks in selfassembly can be of great importance and utility to the supramolecular chemist. [7], [8] Here, we describe the synthesis of a series of chemicallymodified lipophilic natural and non-natural nucleobase derivatives ( Figure 1) that are equipped with either an halogen atom or an ethynyl group at the 5-position (for the pyrimidines) or at the 8-position (in the case of the purines). Pyrimidine nucleobases comprise cytosine (C), uridine (U), and isocytosine (iC), whereas the purines prepared in this work are guanine (G), 2,6-diaminopurine or 2-aminoadenine (DAP; hereafter abbreviated as A), and isoguanine (iG).…”

C–N cross coupling approach synthesis and electronic properties of donor–acceptor oligomer

“…Electronic properties of a molecule can be predictably tuned by the introduction of suitable electron‐donating or electron‐accepting units . Over the last decade, extensive research efforts on the development of conjugated donor–acceptor materials prove that triarylamines are well known donor building blocks for the rational design of high performance optoelectronic materials .…”