Enthalpically and Entropically Favorable Self‐Assembly: Synthesis of C_4h‐Symmetric Tetraazatetrathia[8]circulenes by Regioselective Introduction of Pyridine Rings

Abstract

Self‐assembly of π‐conjugated molecules in solution generally occurs owing to either an enthalpic or an entropic gain; however, designing π‐conjugated systems that simultaneously exhibit enthalpically and entropically favorable self‐assembly behavior is challenging. Herein, the self‐assembly behavior of tetraazatetrathia[8]circulenes is disclosed, which is driven by both enthalpy and entropy. Single‐crystal X‐ray diffraction analysis demonstrated that molecules of these tetraazatetrathia[8]circulenes form face‐to‐face stacked dimers with a 1D columnar structure owing to the circularly arranged dipole moments. Importantly, concentration‐ and temperature‐dependent 1H NMR spectra revealed that the formation of self‐assemblies of tetraazatetrathia[8]circulenes in chloroform and methanol is favored by both enthalpic and entropic factors. The unique association behavior is due to the presence of sp2‐hybridized nitrogen atoms, which weakly coordinate to the hydrogen atoms of these solvents and reduce the π‐electron density of the circulene cores.

Protonation‐Induced Antiaromaticity in Octaaza[8]circulenes: Cyclooctatetraene Scaffolds Constrained with Four Amidine Moieties

“…Cyclic voltammograms and differential pulse voltammograms were obtained under the following conditions; solvent: THF, electrolyte: 0.1 M Bu 4 NPF 6 , working electrode: glassy carbon, counter electrode: Pt, reference electrode: Ag/AgNO 3 , scan rate: 0.1 V/s. Tetraazatetrathia[8]circulene 2 and 1‐butyl‐7‐azaindole were prepared according to the literature [37] …”

“…Tetraazatetrathia [8]circulene 2 and 1butyl-7-azaindole were prepared according to the literature. [37] Synthesis of 3. In a 20 mL Schlenk flask were placed 2 (19.6 mg, 30 μmol), m-chloroperoxybenzoic acid (mCPBA) (118 mg, 16 equiv, containing ca.…”

“…[34,51] We envisaged synthesizing octaaza [8]circulene via an S N Ar reaction of C 4h -symmetric tetraazatetrathia [8]circulenes (Scheme 1). [37] Oxidation of 2 with m-chloroperoxybenzoic acid (mCPBA) provided the corresponding tetraazatetrathia [8]circulene octaoxides (3) in 92% yield. The S N Ar reaction of 3 with p-toluidine in the presence of an excess of potassium bis(trimethylsilyl)amide (KHMDS) afforded octaaza [8]circulene 1 a in 29% yield.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…Alternatively, the tetraiodide was coupled with primary amides to give the tetraamides 249.5a – e , which were then subjected to the Vilsmeier–Haack conditions to give the tetraazatetrathia[8]circulenes 249.6a – e . 468 Besides, the silicon- ( 249.8a ) 466 and germanium-containing ( 249.8b ) 469 hetera[8]circulenes could be obtained in two steps from the tetraiodide 249.2 by employing palladium and rhodium catalysis. The X-ray structures of 249.4a , 6a , 8a , b showed that these polycyclic frameworks were essentially planar.…”

“… Reagents and conditions: (a) 466 NIS, CuI, DMF, 80 °C, 3 h; (b) 467 Pd(PPh 3 ) 2 Cl 2 , CuI, Et 3 N, 60 °C, 3 h; (c) DBU, NMP, reflux, 12 h; (d) 468 CuSO 4 ·5H 2 O, K 2 CO 3 , N , N′ -dimethylethylenediamine, toluene, 80 °C, 20 h; (e) POCl 3 , toluene, 120 °C, 2 h; (f) 466 R 2 SiH 2 , Pd( t -Bu 3 P) 2 , Et 3 N, THF, rt, 48 h; (g) 469 Et 2 GeH 2 , Pd( t -Bu 3 P) 2 , i -Pr 2 NEt, THF, rt, 18 h; (h) 466 [RhCl(cod)] 2 , dppf, toluene, 140 °C, 24 h; (i) 469 [RhCl(cod)] 2 , (C 6 F 5 ) 2 PCH 2 CH 2 P(C 6 F 5 ) 2 , toluene, 140 °C, 20 h. …”