The Design of Radical Stacks: Nitronyl-Nitroxide-Substituted Heteropentacenes

Evgeny Tretyakov, Ashok Keerthi, Martin Baumgarten, Sergey Veber, Matvey Fedin, Dmitry Gorbunov, Inna Shundrina, Nina Gritsan

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The first alkyl chain-anchored heteropentacene, dithieno[2,3-d;2′,3′-d′]benzo-[1,2-b;3,4-b′]dithiophene (DTmBDT), mono- or disubstituted with a nitronyl nitroxide group has been prepared through a cross-coupling synthetic procedure of the corresponding dibromo-derivative (Br2-DTmBDT) with a nitronyl nitroxide-2-ide gold(I) complex. The synthesized nitroxides possess high kinetic stability, which allowed us to investigate their structure and thermal, optical, electrochemical, and magnetic properties. Single-crystal X-ray diffraction of both mono- and diradicals revealed that the nitronyl nitroxide group lies almost in the same plane as the nearest side thiophene ring. Such arrangement favors formation of edge-to-edge dimers, which then form close π-stacks surrounded by interdigitating alkyl chains. Before melting, these nitronyl nitroxide radical substituted molecules undergo at least two different phase transitions (PTs): for the monoradical, PTs are reversible, accompanied by hysteresis, and occur near 13 and 83 °C; the diradical upon heating shows a reversible PT with hysteresis in the temperature range 2–11 °C and an irreversible PT near 135 °C. PTs of this type are absent in Br2-DTmBDT. Therefore, the step-by-step substitution of bromine atoms by nitronyl nitroxide groups changes the structural organization of DTmBDT and induces the emergence of PTs. This knowledge may facilitate crystal engineering of π-stacked paramagnets and related molecular spin devices.

Original languageEnglish
Pages (from-to)642-652
Number of pages11
JournalChemistryOpen
Volume6
Issue number5
DOIs
Publication statusPublished - 1 Oct 2017

Keywords

  • density functional and ab initio calculations
  • EPR spectroscopy
  • fused thiophene
  • nitronyl nitroxides
  • π-stacking
  • DNA-PK
  • COMPLEXES
  • EX-SITU GENERATION
  • OXIDATIVE ADDITION
  • density functional and ab into calculations
  • pi-stacking
  • CARBON-MONOXIDE
  • PALLADIUM-CATALYZED CARBONYLATION
  • ARYL HALIDES
  • ANTIPLATELET ACTIVITY
  • AMINOCARBONYLATION
  • CO SOURCE

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