Isolation and Crystal Structures of Two Singlet Bis(Triarylamine) Dications with Nonquinoidal Geometries

Abstract

We report the first structural data for bis(diarylamine) "bipolarons": we have isolated and crystallographically characterized salts of the dications obtained by two-electron oxidation of E-4,4'-bis[di(p-anisyl)amino]stilbene and E,E-2,5-bis{4-[di(p-anisyl)amino]styryl}-3,4-di(n-butoxy)thiophene, [1](2+) and [2](2+) respectively. ESR, NMR, and magnetometry suggest both species have singlet ground states. X-ray structures, together with (1)H NMR coupling constants for [2](2+), indicate geometries in which the bond lengths are shifted toward a quinoidal pattern relative to that in the neutral species, but not to a fully quinoidal extent. In particular, the bond-length alternations across the vinylene bridging groups approach zero. DFT calculations with closed-shell singlet configurations reproduce the observed structures well. Our results indicate that singlet species for which one might expect quinoidal geometries (with differences of ca. 0.1 A between formally single and double bonds) on the basis of a limiting valence-bond representation of the structure can, in fact, show structures with significantly different patterns of bond lengths.

Wurster‐Type Nanographenes as Stable Diradical Dications

“…Their interesting properties have fueled their development for potential applications in optoelectronics, [1,2] nonlinearo ptics, [3,4] spintronics [5] and organic photovoltaics. [9][10][11][12][13][14][15][16] Aminiumi ons are isoelectronic to carbon and the highere lectronegativity of the nitrogen atom contributes to their high stability in the biradicalf orm. [9][10][11][12][13][14][15][16] Aminiumi ons are isoelectronic to carbon and the highere lectronegativity of the nitrogen atom contributes to their high stability in the biradicalf orm.…”

“…[9][10][11][12][13][14][15][16] Aminiumi ons are isoelectronic to carbon and the highere lectronegativity of the nitrogen atom contributes to their high stability in the biradicalf orm. [12,15] Their low oxidation potential, easy synthesis and open-shell diradical character has drivent he efforts towards their synthesis. [12,15] Their low oxidation potential, easy synthesis and open-shell diradical character has drivent he efforts towards their synthesis.…”

Bis(aminoaryl) Carbon‐Bridged Oligo(phenylenevinylene)s Expand the Limits of Electronic Couplings

“…[20] Open unbridged MV radical cation homologues,D A-(OPV3) and DA(OPV4), do not even show an IV-CT band (vanishing coupling). [21] Thea ttenuation factor, b,i nF igure 2f or DA(COPVn)C + gives av alue of 0.092 À1 ,t hus characterizing the superexchange behavior for charge self-exchange in their ground electronic state.F or the (donor)-COPVn-(acceptor) Zn-COPVn-C 60 compounds with n = 1-4 (Scheme 1), as mall b = 0.056 À1 for excited state charge separation (CS) and b = 0.078 À1 for charge recombination (CR) are reported. [8] These radical cations have also been studied by EPR ( Figure 1d;s ee Figures S39-S41).…”

Electron Transfer Dynamics in Dye‐Sensitized Solar Cells Utilizing Oligothienylvinylene Derivates as Organic Sensitizers

“…Phosphonate 1 was prepared in 69 % yield by quantitative reduction of 4-(diphenylamino)benzaldehyde with NaBH 4 followed by reaction of the alcohol with triethylphosphite and one equivalent of iodine in a one-pot process. [19] Wadsworth-Emmons reaction of phosphonate 1 with one equivalent of bisformyl-oligothienylenevinylene tetramer (OHC-4TV-CHO) [20,21] bearing alkyl chains to give solubility and avoid aggregation of the oligomer afford aldehyde 2 in 60 % yield. Finally, the target molecule FL-7 was obtained in 80 % yield by Knoevenagel condensation of 2 with cyanoacetic acid in the presence of pyperidine.…”