Mechanochemical Synthesis, Photophysical Properties, and X‐ray Structures of N‐Heteroacenes

Abstract

Abstract:The described mechanochemical methodology is an example of a proof-of-concept in which solution-based tedious, poor yielding, and difficult syntheses of pyrazaacenes are achieved under solvent-free ball-milling conditions; the method is easy, high yielding, time-efficient, and environmentally benign. The synthesized compounds also include pyrazaacenes (N-heteroacenes) that are octacene analogues containing pyrene building blocks. The compounds were sparingly soluble in

Synthesis, Photophysical and Electronic Properties of New Red‐to‐NIR Emitting Donor–Acceptor Pyrene Derivatives

“…The large CT nature of the excited state becomes more evident when comparing the emission of 8 with previously reported analogues that only possess a donor or acceptor moiety. Derivative VIII emits in the blue region with λ max (em)=471 nm and compound IV (unfortunately, there is no report of an emission of compound III ) emits in the green region with λ max (em)=520 nm (both in CH 2 Cl 2 ) while we observe a λ max (em)=700 nm for 8 in CH 2 Cl 2 . Nevertheless, the non‐radiative decay rates are significantly increased in CH 2 Cl 2 ( k nr =11×10 7 s −1 ), which is fully in line with the energy gap law as the reorganization energy is enhanced in polar solvents .…”

“…Derivative VIII emits in the blue region with l max (em) = 471 nm and compound IV (unfortunately, there is no report of an emission of compound III) emits in the green region with l max (em) = 520 nm (both in CH 2 Cl 2 ) while we observe a l max (em) = 700 nm for 8 in CH 2 Cl 2 . [32,46] Nevertheless, the non-radiative decay rates are significantly increased in CH 2 Cl 2 (k nr = 11 10 7 s À1 ), which is fully in line with the energy gap law as the reorganization energy is enhanced in polar solvents. [61] Therefore, the quantum yield is strongly decreased in the polar solvent.…”

“…Hence, the electronic coupling V between the localized mixed valence states yields V = 1279 cm À1 for 7 + and I [15] 475 (hexane) 511 (hexane) -À0.18 (CH 2 Cl 2 ) + 0.26 (CH 2 Cl 2 ) 481 (THF) 525 (THF) II [15] 450 (hexane) 464 (hexane) À2.51 (THF) + 0.29 (THF) 462 (THF) 497 (THF) III [32] ---+ 0.14 (CH 2 Cl 2 ) + 0.38 (CH 2 Cl 2 ) IV [28] 453 (toluene) 482 (toluene) ---V [41] 630 (CHCl 3 ) -À0.67 (CHCl 3 ) + 0.39 (CHCl 3 ) -VI [40] 575 (CHCl 3 ) -À1.04 (CHCl 3 ) + 0.33 (CHCl 3 ) -VII [45] 455 (CH 2 Cl 2 ) 538 (CH 2 Cl 2 ) À1.43 (THF) --VIII [46] 435 (CH 2 Cl 2 ) 471 (CH 2 Cl 2 ) --- 2 , which shows that these compounds are class-II compounds, but lie close to the borderline between localized class-II and delocalized class-III compounds, as V is quite large. This result is also in line with the observed broad and asymmetric band shape.…”

Organic Synthesis without Conventional Solvents

“…It was found that many reactions occur much faster as in solution, they can be performed under milder conditions, and the product is isolated in higher yields, compared to the corresponding reaction in solution. [17] Similar process improvements under mechanochemical conditions were achieved for a variety of reactions, for example the amidation of aldehydes, [18] the fluorination of 1,3-diketones, [19] the Michael addition, [20,21] the Knoevenagel condensation, [22] and the Morita-Baylis-Hillman reaction. The reactions were over in 4 h, yielding the products in very good to excellent yield (76-95 %).…”

A Facile, Catalyst‐Free Mechano‐Synthesis of Quinoxalines and their In‐Vitro Antibacterial Activity Study

“…A couple of mechanochemical methods for the construction of quinoxaline ring are available in literature . Sahoo et al reported a method for the synthesis of quinoxaline based heteroacences using a ball‐mill . On the other hand, a hand‐grinding method by Li et al is also available in which basic Al 2 O 3 was used as reaction media and products were purified by column chromatography.…”