Energy redistribution dynamics in triarylamine-triarylborane containing hexaarylbenzenes.

Two hexaarylbenzenes (HAB) 1 and 2 each decorated by three triarylamines (TAA) as electron donors and three triarylboranes (TAB) as electron acceptors in a symmetric (1) and asymmetric (2) fashion as well as one model compound (3) with only one donor-acceptor pair were investigated by ultrafast transient absorption and fluorescence upconversion spectroscopy. Fluorescence anisotropy measurements revealed energy redistribution between localised, partly relaxed CT-states of the HABs 1 and 2 induced by dipole-dipole interaction with energy transfer time constants of ca. 3 ps.

On the relation of energy and electron transfer in multidimensional chromophores based on polychlorinated triphenylmethyl radicals and triarylamines.

A star-like compound consisting of a polychlorinated triphenylmethyl radical (PCTM) core linked to three triarylamines (TAA) and a symmetric and an asymmetric hexaarylbenzene (HAB) both substituted with three PCTMs and three TAAs were synthesised. In the star-like compound a strong communication between the redox centres was observed by electron paramagnetic resonance spectroscopy and UV/Vis/NIR absorption measurements, whereas in the HABs only a weak interaction could be detected. The temporal evolution of the excited states was monitored by ultrafast transient absorption measurements.

Charge-transfer interactions in tris-donor-tris-acceptor hexaarylbenzene redox chromophores.

Symmetric- and asymmetric hexaarylbenzenes (HABs), each substituted with three electron-donor triarylamine redox centers and three electron-acceptor triarylborane redox centers, were synthesized by cobalt-catalyzed cyclotrimerization, thereby forming compounds with six- and four donor-acceptor interactions, respectively. The electrochemical- and photophysical properties of these systems were investigated by cyclovoltammetry (CV), as well as by absorption- and fluorescence spectroscopy, and compared to a HAB that only contained one neighboring donor-acceptor pair. CV measurements of the asymmetric HAB show three oxidation peaks and three reduction peaks, whose peak-separation is greatly influenced by the conducting salt, owing to ion-pairing and shielding effects.

Charge-transfer interactions in a multichromophoric hexaarylbenzene containing pyrene and triarylamines.

Two different hexaarylbenzenes with three pyrene and three triarylamine substituents in different positions (trigonal symmetric and asymmetric arrangement) were synthesized, and their charge-transfer states were investigated by optical spectroscopy. In these multichromophoric systems triarylamine acts as the electron donor and pyrene as the electron acceptor. A reference chromophore with only one donor-acceptor pair was also investigated.

Mixed-valence interactions in triarylamine-gold-nanoparticle conjugates.

Optical and electrochemical investigations of triarylamine redox centres attached to gold nanoparticles via a pi-conjugated bridge show intervalence charge-transfer bands which prove to be surprisingly strong interchromophore interactions.