Charge Transfer Emission in Oligotriarylamine–Triarylborane Compounds

Abstract

Donor-acceptor compounds exhibiting charge transfer emission are of interest in a variety of different contexts, for example, for nonlinear optical processes and for sensor applications. Recently investigated triarylamine-triarylborane compounds represent an important class of donor-acceptor systems, and we explored to what extent their charge-transfer properties can be further improved by using stronger amine donors and borane acceptors than prior studies. The oligotriarylamine employed here is a much stronger donor than previously used triarylamines containing single nitrogen centers. In order to increase the acceptor strength, the electron-accepting unit was equipped with two (instead of one) dimesitylboron substituents. In our comparative study, six donor-acceptor compounds were synthesized and investigated by cyclic voltammetry and optical spectroscopy. An increase of the donor strength through replacement of an ordinary triarylamine by an oligotriarylamine unit leads to the expected energetic stabilization of charge transfer (CT) excited states, but the emission solvatochromism is not more pronounced. The attempted increase of the acceptor strength by substitution of the acceptor moiety by two (instead of one) dimesitylboron groups leads to a drastic decrease of emission quantum yields. On the basis of these results, our purely experimental study provides fundamental guidelines for the design of new triarylamine-triarylborane donor-acceptor compounds with favorable charge-transfer emission properties.

Ultrafast Investigation of Intramolecular Charge Transfer and Solvation Dynamics of Tetrahydro[5]-helicene-Based Imide Derivatives

“…All the absorption maxima displayed by THHBI derivatives in various solvent are ascribed to the charge-transfer states, which can be further proved by following quantum chemical calculations results. It is found that the absorption maximum for each dye shows nearly no noticeable shift but the emission spectra show appreciable bathochromic shift with increase in polarity of solvents, indicating nearly zero dipole moment in the ground state but large dipole moments in the excited state 24 25 26 . The peak positions of absorption and emission spectra for all dyes as a function of the solvent polarity are displayed in Fig.…”

Excited‐State Pathways of Four‐Coordinate N,C‐Chelate Organoboron Dyes

“…In this context the interesti n new organoboronc ompounds as fluorescent dye platforms is steadily growing with the aim to optimizea nd diversify photophysicala nd photochemical properties, such as light absorption, emission quantum yields, or photochemical stability. Three-coordinate organoboron dyes [1,2] contain electron-deficient boron.T his electronic feature introduces acceptorp roperties that may be integrated in sophisticated charge-transfer architectures [3][4][5][6][7] and two-photon-addressable molecules. [8,9] The Lewis acidic nature of trivalent boron can be used for the design of chemosensors forf luoride.…”

“…Three‐coordinate organoboron dyes contain electron‐deficient boron. This electronic feature introduces acceptor properties that may be integrated in sophisticated charge‐transfer architectures and two‐photon‐addressable molecules . The Lewis acidic nature of trivalent boron can be used for the design of chemosensors for fluoride .…”

Cyclometalated Platinum(II) Complexes with Donor‐Acceptor‐Containing Bidentate Ligands and Their Application Studies as Organic Resistive Memories

“…6570 � 190 cm À 1 , which is comparable to other compounds with strong charge transfer properties, as well as a good linearity of the plot (R 2 = 0.9925) further support the charge transfer nature of this class of complexes. [14] Upon photoexcitation at 436 nm in degassed acetone, the complexes generally give broad and structured emission bands at ca. 557-708 nm, with lifetimes in the microsecond regime.…”