Synthesis and Optical Properties of Triphenylene-Based Dendritic Donor Perylene Diimide Acceptor Systems

Abstract

A donor-acceptor charge transfer system based on two discotic mesogens has been synthesized. The donor is either a triphenylene (POG0) or a triphenylene-based conjugated dendron (POG1), while the acceptor is a perylene diimide (PDI) core. The donors are covalently linked to the bay positions of the PDI core through an ether linkage. In chloroform, due to the short donor-acceptor distance and the matching frontier orbital levels, photoinduced charge transfer from either the donor excitation or the acceptor excitation are both thermodynamically and kinetically favored, resulting in efficient quenching of both donor and acceptor fluorescence. In a less polar solvent, hexane, while charge transfer is still the dominant mechanism for decay of the excited electronic state of POG1, photoinduced charge transfer is no longer energetically favorable for POG0 when the acceptor PDI core is excited, making the PDI core of POG0 weakly fluorescent in chloroform but strongly so in hexane. In solid film, POG0 is highly aggregated through both PDI-PDI and triphenylene-triphenylene homotopic stacking. POG1, on the other hand, aggregates through triphenylene dendrons with limited PDI-PDI core stacking, presumably due to the steric hindrance caused by bulky triphenylene moieties which block the access to the PDI core. The efficient photoinduced charge transfer, coupled with the homotopic stacking that forms separated electron-transporting PDI-stacked columns and hole transporting triphenylene-stacked columns, suggests that the reported donor-acceptor systems based on dual-discotic mesogens are potentially new efficient photovoltaic materials.

Discotic liquid crystals of transition metal complexes 52: Synthesis and homeotropic alignment of liquid crystalline phthalocyanine-fullerene dyad bridged by vanillin

“…We have previously reported that a novel type of flying-seed-like liquid crystals show mesomorphism despite absence of long chains [36][37][38][39][40][41]. For example, (m-CH 3 OPhO) 8 PcCu (8) in Fig. 8[A] shows mesomorphism.…”

“…1[C]). Furthermore, the (C n S) 6 PcCu-C m -C 60 dyads (2a-c) exhibit homeotropic alignment at rt for (n, m) = (14,8), (14,10), (14,12). Hence, the donor part of hexakistetradecyllthio-substituted PcCu, (C 14 S) 6 PcCu-, may be favourable to induce a room temperature liquid crystalline phase.…”

Discotic liquid crystals of transition metal complexes 49: establishment of helical structure of fullerene moieties in columnar mesophase of phthalocyanine-fullerene dyads

“…Further studies are needed using a new homologue substituted by chiral alky chains. Nevertheless, to our best knowledge, this is the first established example of the helical structure of fullerenes in columnar liquid crystalline donor-acceptor dyads [13][14][15][16][17][18][19][20][21][22][23][24][25].…”

Discotic liquid crystals of transition metal complexes 48: Synthesis of novel phthalocyanine-fullerene dyads and effect of a methoxy group on their clearing points

“…They can greatly reduce their costs to manufacture the solar cells. Liquid crystalline D-A systems are braodly classified into three groups: smectic liquid crystals [1][2][3][4], liquid crystalline copolymers [5][6][7][8][9][10][11][12] and discotic columnar liquid crystals [13][14][15][16][17][18][19][20][21][22][23][24][25]. In 2004 Kim et al reported that an organic photovoltaic cell was fabricated by using liquid crystalline N,N'-diheptyl-3,4,9,10-perylenetetracarboxylicdiimide (PTCDI-C7) as the electron acceptor and zinc phthalocyanine (ZnPc) as the electron donor [1].…”

“…On the contrary, it is unfavourable to form both defects and polydomains in the homeotropic alignment [29]. Up to date, there have been some donor-acceptor dyads showing columnar liquid crystalline mesophases [13][14][15][16][17][18][19][20][21][22][23][24][25]. For example, Bushby et al reported in 2005 that a triphenylene derivative connected with fullerene showed columnar mesomorphism [13].…”