Control of electronic and exchange coupling by bridge substituents in donor acceptor triads with triptycene bridges.

A series of triads, consisting of a triarylamine electron donor and a perylene diimide electron acceptor which were attached to two different wings of a triptycene bridging unit, was investigated concerning the dynamics of photoinduced charge separation and charge recombination processes with a particular focus on the involved spin-chemical aspects. Attaching electron-donating or electron-withdrawing substituents to the third wing of the triptycene bridge allowed tuning the electron transfer processes. These processes were investigated fs-transient absorption spectroscopy and ns-transient absorption spectroscopy in an external magnetic field.

Optically induced charge-transfer in donor-acceptor-substituted p- and m- CBH carboranes.

Icosahedral carboranes, CBH, have long been considered to be aromatic but the extent of conjugation between these clusters and their substituents is still being debated. m- and p-Carboranes are compared with m- and p-phenylenes as conjugated bridges in optical functional chromophores with a donor and an acceptor as substituents here. The absorption and fluorescence data for both carboranes from experimental techniques (including femtosecond transient absorption, time-resolved fluorescence and broadband fluorescence upconversion) show that the absorption and emission processes involve strong intramolecular charge transfer between the donor and acceptor substituents via the carborane cluster.

Structure and Photophysics of N-Tolanyl-phenochalcogenazines and their Radical Cations.

The study focuses on the structural and photophysical characteristics of neutral and oxidized forms of N-tolanyl-phenochalcogenazines PZX-tolan with X=O, S, Se, and Te. X-ray crystal structure analyses show a pseudo-equatorial (pe) structure of the tolan substituent in the O, S, and Se dyads, while the Te dyad possesses a pseudo-axial (pa) structure. DFT calculations suggest the pe structure for O and S, and the pa structure for Se and Te as stable forms.

The influence of hindered rotation on electron transfer and exchange interaction in triarylamine-triptycene-perylene diimide triads.

Stretched electron-donor-bridge-acceptor triads that exhibit intramolecular twisting degrees of freedom are capable of modulating exchange interaction () as well as electronic couplings through variable π-overlap at the linear bond links, affecting the rate constants of photoinduced charge separation and recombination. Here we present an in-depth investigation of such effects induced by methyl substituents leading to controlled steric hindrance of intramolecular twisting around biaryl axes. Starting from the parent structure, consisting of a triphenyl amine donor, a triptycene (TTC) bridge and a phenylene-perylene diimide acceptor (Me0), one of the two phenylene linkers attached to the TTC was -substituted by two methyl groups (Me2, Me3), or both such phenylene linkers by two pairs of methyl groups (Me23).

Push-pull [7]helicene diimide: excited-state charge transfer and solvatochromic circularly polarised luminescence.

In this communication we describe a helically chiral push-pull molecule named 9,10-dimethoxy-[7]helicene diimide, displaying fluorescence (FL) and circularly polarised luminescence (CPL) over nearly the entire visible spectrum dependent on solvent polarity. The synthesised molecule exhibits an unusual solvent polarity dependence of FL quantum yield and nonradiative rate constant, as well as remarkable and values along with high configurational stability.