Structure–charge transfer property relationship in self-assembled discotic liquid-crystalline donor–acceptor dyad and triad thin films

Abstract

The photophysical properties of donor-acceptor (D-A) and donor-acceptor-donor (D-A-D) liquid crystalline dyads and triads based on two different discotic mesogens are examined in thin films by steady-state optical spectroscopy and subpicosecond transient absorption measurements. In these systems, triphenylene and perylene bisimide units are covalently linked by flexible decyloxy chain(s) and act as an electron donor (D) and acceptor (A), respectively. These discotic liquid-crystalline systems form well-separated D and A p-stacked columnar structures in thin films. The absorption spectra of the films indicate an aggregation of the perylene bisimide and triphenylene moieties along the columns. Steadystate photoluminescence measurements show a strong fluorescence quenching that is mainly attributed to a photo-induced charge transfer process taking place between the triphenylene and perylene bisimide units. Subpicosecond transient absorption measurements show that the photoinduced charge transfer (CT) states in the dyad and triad films are formed within 0.3 ps and recombine on a 150-360 ps time scale. In addition, a correlation between the dynamics of the charge recombination process and the spacing distances between D and A units can be established in the dyad and triad films. This study provides important information on the relationship between molecular packing and the charge transfer properties in such self-organized D and A columnar nanostructures.

Charge-transfer dynamics and nonlocal dielectric permittivity tuned with metamaterial structures as solvent analogues

“…Transient absorption spectroscopy. The femtosecond transient absorption measurements carried out in transmittance mode were performed according to previous works, 54 while identical dynamics were confirmed in reflectance mode. Both modes used pump and probe pulses generated by a Ti:Sapphire regenerative amplifier (Spitfire Pro XP, Spectra-Physics) working with an 800 nm output.…”

“…Connected by a decyloxy flexible bridge, the TriPh (D) and PerDi (A) units are prone to self-assemble in a solid state multisegregated D-A columnar structure at the local range. 53,54 Grazing Incidence X-ray Scattering (GIXS) of the dyad films on Al 2 O 3 surfaces revealed a spontaneous planar orientation of columnar hexagonal structures (Col h ) consisting of domains of lying columns as illustrated in Figure 1 |b2 and SI- Figure 1|. The annealing step in the fluid state of the mesophase only develops the long-range order enhancing the regularity of structure and the planar orientation.…”

Halogen Bonding: A Halogen-Centered Noncovalent Interaction Yet to Be Understood

“…Finally, the wave function should be designed in such a manner as not to neglect the instantaneous correlation between the electrons' movements in response to their mutual electrostatic repulsions." Although this is the argument advanced in that study [27], Ivanov et al [66] demonstrated that the frontier orbitals are game makers in that the extent of orbital overlap greatly assists in the rationalization of the role played by polaron localization and delocalization, a topic of significant interest in the rational design of novel charge-transfer materials [67][68][69][70].…”

Mesogenic complementary absorbing dyads based on porphyrin and perylene units

“…Since the so-called p-n heterojunction exists at the molecular level, these D-A DLCs possess fast intramolecular photoinduced electron transfer and form charge separated states [29][30][31][32][33]. Some D-A DLCs yield dual pathways along molecular columns to transfer electrons and holes [34,35].…”