Long-Lived Hole Stabilized at a Triphenylamine Core and Shielded by Rigid Phenylazomethine Dendrons: A Pulse Radiolysis Study

Abstract

The optical properties and reactivity of one-electron oxidized states (radical cations) of dendrimers are investigated in benzonitrile solutions by nanosecond pulse radiolysis. The hole stabilized at the triphenylamine (TPA) core is effectively shielded by a rigid dendritic phenylazomethine (DPA) shell of four generations, leading to an extension of its lifetime by nearly 2 orders of magnitude in comparison with a core radical cation without dendrons. A continuous red shift of the peak in the photoabsorption spectrum in the visible region and a decrease in the extinction coefficients (oscillator strengths) are found with increasing dendrimer generation number. These experimental observations are compared to the results of time-dependent density functional theory. It is suggested that bulky, rigid, insulating DPA dendrons shield against outer reactants and stabilize hole at the TPA core. Correlating the dendrimer generation number with the optical properties and reactivities of the radical cations could shed light on fundamental aspects of structurally defined nanoenvironments having hyperbranched entities.

π‐Electron‐System‐Layered Polymer: Through‐Space Conjugation and Properties as a Single Molecular Wire

“…On the basis of extinction coefficient calculated from the spectrum fitting and calculated oscillator strength, [33,34] the triplet yields of 10 and 12 in polystyrene matrices generated upon exposure to a 355 nm nanosecond laser were estimated to be 6.1 10 À3 and 8.7 10 À3 , respectively. [33] This suggests that the photo charge carrier generation yields (f) of 10 and 12 are on the same order and much smaller than triplet yield.…”

Assembly of carbon nanotubes and alkylated fullerenes: nanocarbon hybrid towards photovoltaic applications

“…As shown in Fig. 7a, the fluorescence decay of 1 in CHCl 3 (red) can be represented by a single-exponential function with a lifetime of To identify the transient intermediates involved in 1-SWCNT, transient absorption spectral studies were performed using a 355 nm laser, 48 which corresponds to a wavelength of predominant C 60 absorption ($75%, see Fig. S14 †) and, therefore, mainly excited the C 60 moiety and formed a C 60 triplet excited state ( 3 C 60 *) via intersystem crossing from the singlet.…”

Charge Carrier Mobilities in Amorphous Triphenylamine–Fluorene Copolymers: Role of Triphenylamine Unit in Intra- and Intermolecular Charge Transport

“…Among the large class of semiconducting organic conjugated polymers, triphenylamine (TPA) and fluorene (FL)-based copolymers occupy a unique place in OLEDs [1][2][3][4] and organic photovoltaic cells (OPVcs), 5,6) because the TPA is an efficient hole transporting unit (i.e., it acts as a donor). Thanks to this, analogous molecules, for instance, N,N 0 -diphenyl-N,N 0bis(3-methylphenyl)-(1,1 0 -biphenyl)-4,4 0 -diamine (TPD), [6][7][8] N,N 0 -bis(1-naphthyl)-N,N 0 -diphenylbenzidine (-NPD), 9,10) and TPA dendrimers 11,12) have been utilized as a hole transport layer in OLEDs.…”