Optical properties of porphyrin derivatives were used to fabricate an artificial light-harvesting system. The introduction of a N-H···O= hydrogen-bonding alkylamide chain (-CONHCnH2n+1) into a functional π-system is among the useful approaches to design multifunctional supramolecular assemblies. The tetraphenylporphyrin derivative bearing four -CONHC14H29 chains (1) shows the successive and reversible phase transition behavior of S1-S2 at 338 K, S2-Colr at 444 K, and Colr-I (isotropic liquid) at 564 K, where a fluidic discotic rectangular columnar (Colr) liquid crystal phase was observed in a wide temperature range of 444-564 K before melting. The one-dimensional columnar molecular assembly of (1)∞ was constructed using a simultaneous operation of N-H···O= hydrogen-bonding and π-stacking interactions. Temperature (T)- and frequency (f)-dependent dielectric constants of 1 indicated characteristic dielectric enhancement at higher-T and lower-f conditions above 500 K because of the thermally activated motional freedom of the polar N-H···O= hydrogen-bonding unit in the Colr phase. The polarization-electric field (P-E) curves at f = 0.1 Hz clearly indicated ferroelectric hysteresis behavior with a remanent polarization (Pr) of 1 μC cm-2 and a coercive electric field (Ec) of 2 V μm-1 at 503 K. The stable operation of the high-T ferroelectrics at approximately 500 K facilitates the potential application of a memory device in a high-T environment.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films