Radical cations of end-capped tetrathienoacenes and their π-dimerization controlled by the nature of α-substituents and counterion concentration

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Diarylamine‐substituted osmanaphthalyne complexes that feature two redox centers linked by the rigid skeleton of the metallacycle (C^C+), specifically, [OsCl2(PPh3)2{(C^C+)NAr2}][BF4−] (Ar=Ph (1 a), p‐MeOPh (1 b)) and their open‐ring precursors [OsHCl2(PPh3)2{(≡C−C(PPh3+)=CHPh)NR2}][BF4−] (Ar=Ph (2 a), p‐MeOPh (2 b)), were successfully synthesized and characterized by 1H, 13C, and 31P NMR spectroscopy, ESI‐MS, and elemental analysis. The solid‐state molecular structures of complexes 1 a and 2 a were ascertained by single‐crystal X‐ray diffraction. The Os≡C bond length in both complexes 1 a and 2 a fell within the range reported for similar osmanaphthalynes and osmium carbyne complexes, respectively. The structural parameters determined for complex 1 a, which were successfully reproduced by theoretical calculations, point to a π‐delocalized metallacycle structure. The purple color of compounds 1 a and b was explained by the diarylamine→Os(metallacycle) charge‐transfer absorption in the visible region. The neutral, one‐electron‐oxidized and one‐electron‐reduced states of compounds 1 a, b, and a reference complex that lacked the diarylamine substituent, [OsCl2(PPh3)2{(C^C+)}][BF4−] (1′), were investigated by cyclic and square‐wave voltammetry, UV/Vis/NIR spectroelectrochemistry, and DFT calculations. The spin density in singly oxidized complexes [1 a]+ and [1 b]+ predominantly resided on the aminyl segment, with osmium involvement controlled by the diphenylamine substitution. Spin density in stable, singly‐reduced [1′]− was distributed mainly over the osmanaphthalyne metallacycle.

Section: Methodsmentioning

confidence: 99%

“…Thianthrenium hexafluorophosphate (TAPF 6 ), which was used for the chemical oxidation of 1b,w as prepared by ap ublished procedure. [37] Chem. Eur.J.…”

Section: Generalm Aterialsmentioning

confidence: 99%

Diphenylamine‐Substituted Osmanaphthalyne Complexes: Structural, Bonding, and Redox Properties of Unusual Donor–Bridge–Acceptor Systems

Zhang

Jin

et al. 2018

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“…40 Despite the large number of studies available on the π dimerization of oligothiophene radical cations, only a few examples are devoted to the study of the supramolecular arrangement of oligothienoacene radical cations. For instance, some of us recently demonstrated the formation of π‐dimer dications in oxidized tetrathienoacenes,41 pentathienoacenes,42 and heptathienoacenes 43. When compared to α‐linked oligothiophenes, the high propensity towards π dimerization of oligothienoacene radical cations can be attributed to the rigid and planar structure that can maximize the intermolecular orbital overlap upon oxidation.…”

Section: Introductionmentioning

confidence: 99%

Multistep π Dimerization of Tetrakis(n‐decyl)heptathienoacene Radical Cations: A Combined Experimental and Theoretical Study

Ferrón

Capdevila‐Cortada

Balster

et al. 2014

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Radical cations of a heptathienoacene α,β-substituted with four n-decyl side groups (D4T7(.) (+) ) form exceptionally stable π-dimer dications already at ambient temperature (Chem. Comm. 2011, 47, 12622). This extraordinary π-dimerization process is investigated here with a focus on the ultimate [D4T7(.) (+) ]2 π-dimer dication and yet-unreported transitory species formed during and after the oxidation. To this end, we use a joint experimental and theoretical approach that combines cyclic voltammetry, in situ spectrochemistry and spectroelectrochemistry, EPR spectroscopy, and DFT calculations. The impact of temperature, thienoacene concentration, and the nature and concentration of counteranions on the π-dimerization process is also investigated in detail. Two different transitory species were detected in the course of the one-electron oxidation: 1) a different transient conformation of the ultimate [D4T7(.) (+) ]2 π-dimer dications, the stability of which is strongly affected by the applied experimental conditions, and 2) intermediate [D4T7]2 (.) (+) π-dimer radical cations formed prior to the fully oxidized [D4T7]2 (.) (+) π-dimer dications. Thus, this comprehensive work demonstrates the formation of peculiar supramolecular species of heptathienoacene radical cations, the stability, nature, and structure of which have been successfully analyzed. We therefore believe that this study leads to a deeper fundamental understanding of the mechanism of dimer formation between conjugated aromatic systems.

“…The electronic and CD spectra of (R p ,R p )-1 2 + + calculated at the TD-UM05-2X/B3LYP/6-31G(d,p)//UM05-2X/6-31G(d,p) level of theory for the mosts table geometry (D 2 )q ualitatively reproduced the observed spectra (Figure 6a). [23] The analysis of the transition states showed that the CD spectrum consists mainly of two pairs of excitonc ouples associated with the electronic transitions D 2 (S 1 -S 2 )a nd D 1 (S 9 -S 14 ) ( Figure 6b). These exciton couples were attributed to the Davydovs plitting derived from the p-dimeric polaronic oligothiophenes.…”

Section: Dedicatedtoprof Drm Asahiko Iyoda On the Occasion Of His 7mentioning

confidence: 99%

Macrocyclic Oligothiophene with Stereogenic [2.2]Paracyclophane Scaffolds: Chiroptical Properties from π‐Transannular Interactions

Hasegawa

Kobayakawa

Matsuzawa

et al. 2017

The enantiomers of a new cyclic oligothiophene, bridged by two pseudo-ortho[2.2]paracyclophanes, were synthesized as a new class of the chiral π-conjugated system. Single-crystal X-ray diffraction analysis revealed a twisted structure for these oligothiophenes induced by a torsion of the cyclophane moieties. The embedding oligothiophenes into the inherent planar chirality provided a significant enhancement in circular dichroism (CD) spectra thanks to the large magnetic/electric transition dipole moments. In the dicationic state, an intramolecular π dimer was formed due to the strong interactions of the oligothiophenes. We further recorded unprecedented wide ranges of CD spectra in 250-1800 nm region. The transitions are reasonably described by the exciton coupling of the oligothiophenes.