828922-44-7Relevant academic research and scientific papers
X-Shaped Oligomeric Pyromellitimide Polyradicals
Wu, Yilei,Han, Ji-Min,Hong, Michael,Krzyaniak, Matthew D.,Blackburn, Anthea K.,Fernando, Isurika R.,Cao, Dennis D.,Wasielewski, Michael R.,Stoddart, J. Fraser
, p. 515 - 523 (2018)
The synthesis of stable organic polyradicals is important for the development of magnetic materials. Herein we report the synthesis, isolation, and characterization of a series of X-shaped pyromellitimide (PI) oligomers (Xn-R, n = 2-4, R = Hex or Ph) linked together by single C-C bonds between their benzenoid cores. We hypothesize that these oligomers might form high-spin states in their reduced forms because of the nearly orthogonal conformations adopted by their PI units. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies confirmed the isolation of the dimeric, trimeric, and tetrameric homologues. X-ray crystallography shows that X2-Ph crystallizes into a densely packed superstructure, despite the criss-crossed conformations adopted by the molecules. Electrochemical experiments, carried out on the oligomers Xn-Hex, reveal that the reductions of the PI units occur at multiple distinct potentials, highlighting the weak electronic coupling between the adjacent redox centers. Finally, the chemically generated radical anion and polyanion states, Xn-Hex?- and Xn-Hexn(?-), respectively, were probed extensively by UV-vis-NIR absorption, EPR, and electron nuclear double resonance (ENDOR) spectroscopies. The ENDOR spectra of the radical monoanions Xn-Hex?- reveal that the unpaired electron is largely localized on a single PI unit. Further reductions of Xn-Hex?- yield EPR signals (in frozen solutions) that can be assigned to spin-spin interactions in X2-Hex2(?-), X3-Hex3(?-), and X4-Hex4(?-). Taken together, these findings demonstrate that directly linking the benzene rings of PIs with a single C-C bond is a viable method for generating stabilized high-spin organic anionic polyradicals.
Synthesis of bromo- and iodo-substituted pyromellitic diimide-based [2+2]- and [3+3]macrocycles, and their absorption spectra and electrochemical and inclusion properties
Ershad Halim, Md.,Bandyopadhyay, Arkasish,Sun, Liansheng,Tao, Keisuke,Sangvikar, Yogesh Shashikant,Miyazaki, Takaaki,Watanabe, Motonori,Ideta, Keiko,Matsumoto, Taisuke,Goto, Kenta,Shinmyozu, Teruo
supporting information, p. 6970 - 6974 (2015/11/27)
New pyromellitic diimide-based tetrabromo[2+2]macrocycle ([2+2]MC) 2, tribromo- and hexabromo[3+3]MCs 3a and 3b, as well as triiodo[3+3]MC 3c were synthesized as structural units of covalently bound nanotubes, and their absorption spectra and redox properties, as well as inclusion phenomena of the [2+2]MC 2 were reported. Tetrabromo[2+2]MC 2 forms a 1:1 inclusion complex with toluene, whose structure was revealed by X-ray structural analysis.
Crystal structure of 1,1′-biphenyl-2,2′,3,3′- tetracarboxylic and 1,1′-biphenyl-2,2′,3,3′,5,5′,6, 6′-octacarboxylic acids: Solid-state chiralization and dissociation
Holy, Petr,Sehnal, Petr,Tichy, Milos,Zavada, Jiri,Cisarova, Ivana
, p. 3805 - 3810 (2007/10/03)
X-ray diffraction analysis revealed unexpected stereochemical features accompanying crystal self-assembly of the two title oligocarboxylic acids.
