Ferroelectricity of a Tetraphenylporphyrin Derivative Bearing −CONHC₁₄H₂₉ Chains at 500 K

Abstract

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 (−CONHC n H 2n+1 ) into a functional π-system is among the useful approaches to design multifunctional supramolecular assemblies. The tetraphenylporphyrin derivative bearing four −CONHC 14 H 29 chains (1) shows the successive and reversible phase transition behavior of S1−S2 at 338 K, S2−Col r at 444 K, and Col r −I (isotropic liquid) at 564 K, where a fluidic discotic rectangular columnar (Col r ) 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 Col r phase. The polarization−electric field (P−E) curves at f = 0.1 Hz clearly indicated ferroelectric hysteresis behavior with a remanent polarization (P r ) of 1 μC cm −2 and a coercive electric field (E c ) 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.

Adjacent functional group effects on the assembly of columnar liquid crystals

“…It is in this context that we have been examining the structureproperty relations of columnar liquid crystals formed from discshaped molecules ("discotic mesogens"). These phases have been targeted for applications such as solar cells, [10][11][12][13][14][15] ferroelectrics, [16][17][18] and ionic conductive materials. [19][20][21] Our primary targets are dibenzophenazines, D(X,Y), which constitute a versatile family of discotic mesogens that tend to form columnar phases with wide temperature ranges.…”

Simple molecular ferroelectrics:N,N′-dialkyl-terephthalamide derivatives in the solid phase

“…The ferroelectric alkylamide unit can be introduced into a variety of functional p-molecules. For instance, the p-expanded pyrene [44][45][46] and tetrabenzoporphyrin 47 bearing four -CONHC 14 H 29 chains formed 1D ferroelectric hydrogen-bonding columns as well as a specific optical response simultaneously. Therefore, multifunctionality has been designed for various p-molecular systems using a rational design of hydrogen-bonding alkylamide chains.…”

Ferroelectricity of Hydrogen-Bonded Azobenzene Derivatives

“…38−40 Additionally, the π-expanded tetrabenzoporphyrin core substantially enhanced the thermal stability of the ferroelectric state for applications in high-temperature memory devices. 41 Organic ferroelectrics has attracted much attention to form environmentally friendly low-cost, rare metal-free, and nontoxic element flexible memory devices instead of typical inorganic ferroelectrics. 46,47 Recent progress of physical parameters of high remanent polarization and a low coercive electric field in organic crystals is one of the research topics in material chemistry, and a new ferroelectric mechanism has been extensively examined in organic molecular assemblies.…”

“…The amide-type hydrogen bond stabilizes the one-dimensional (1D) column in the Col h liquid crystal. Among the various benzene derivatives comprising −CONHC n H 2 n +1 chains, a 1,3,5-alkylamide-benzene ( 3BC ) derivative showed ferroelectricity in the polarization–electric field ( P – E ) response in the Col h mesophase, and the polar N–H···O inversions occurred when an external electric field ( E ) was applied along the π-stacking column. − We expanded this molecular design to several π-molecular cores, such as pyrene, − tetrabenzoporphyrin, helicene, and other systems, − using alkylamide chains, and the N–H···O hydrogen bond induced a mesophase as well as a ferroelectric ground state into these systems. This molecular design enabled us to form a multifunctional molecular assembly of a pyrene derivative containing four −CONHC 14 H 29 chains, which demonstrated the ferroelectricity, monomer–excimer fluorescence, current switching behaviors, and the formation of Col h liquid crystals, organogels, and nanofibers. − Additionally, the π-expanded tetrabenzoporphyrin core substantially enhanced the thermal stability of the ferroelectric state for applications in high-temperature memory devices .…”