Preparation and Characterization of Intrinsic Porous Polyamides Based on Redox-Active Aromatic Diamines with Pentiptycene Scaffolds.

The electrochromic (EC) polyamides (Ether-PentiTPA1 and Ether-PentiTPA8) from the electroactive pentiptycene-derived triphenylaminediamine monomers (PentiTPA1 and PentiTPA8) were designed and prepared via polycondensation. The incorporation of rigid and contorted H-shaped pentiptycene scaffolds could restrain polymer chains from close packing and further form intrinsic microporosity in the polymer matrix which could be confirmed by the measurements of WXRD, BET, and PALS. With the existence of intrinsic microporosity, the diffusion rate of counterions between the electroactive polymer film and electrolyte can be promoted during the electrochemical procedure. Therefore, the prepared polyamide Ether-PentiTPA1 exhibits enhanced EC behaviors, such as lower driving potential (1.11 V), smaller redox potential difference ΔE (0.24 V), and shorter switching response time (3.6/5.2 s for coloring/bleaching). Consequently, the formation of intrinsic microporosity can be a useful approach for the enhancement of EC response performance.

Electrochromic Response Capability Enhancement with Pentiptycene-Incorporated Intrinsic Porous Polyamide Films.

Enhancing switching response capability of electrochromic (EC) polymers has been a topical issue. Herein, the H-shaped nonplanar pentiptycene scaffold is successfully introduced into the polyamide film derived from N,N'-bis(4-aminophenyl)-N,N'-di(methoxyphenyl)-1,4-phenylenediamine (TPPA), and the resulting copolymer shows enhanced EC behaviors, including lower oxidation potential and shorter switching response time, as compared to the corresponding TPPA-derived homopolymer.

Iptycene substitution enhances the electrochemical activity and stability of polyanilines.

The electrochemical stability of polyaniline (PANI) films is a key issue for their application as electrode materials. This work demonstrates that a low fraction (<5%) of pentiptycene incorporation of the PANI conjugated backbone could significantly enhance the capacitive performance and charge-discharge cycling stability of PANI films, attributable to the clipping effect of pentiptycene cavities that restricts motional freedom of polymer chains and promotes interchain conductivity.

Light-gated molecular brakes based on pentiptycene-incorporated azobenzenes.

Three azobenzene derivatives (2 R, 2 OR, and 2 NR) that differed in their terminal substituent (alkyl, alkyloxy, and dialkylamino, respectively) have been synthesized and investigated as molecular brakes, in which the rigid H-shaped pentiptycene group functioned as a rotor and the dinitrophenyl group as a "brake pad". The E and Z isomers of these compounds corresponded to the "brake-off" and "brake-on" states, respectively. The rotation rate of the rotor was evaluated by VT NMR spectroscopy for the brake-on state and by DFT calculations for the brake-off state. The difference between the rotation rates for the rotor in the two states was as large as eight orders of magnitude at ambient temperature. Photochemical switching of the azobenzene moieties afforded efficiencies of 55-67%. A combination of photochemical E→Z and thermal Z→E isomerization promoted the switching efficiency up to 78%. The terminal substituent affected both the photochemical and thermal switching efficiencies. Solvent polarity also played an important role in the lifetimes of the Z isomers. These azobenzene systems displayed similar braking powers but superior switching efficiencies to the stilbene analogue (1O R; ca. 60% vs 20%).

Effects of iptycene scaffolds on the photoluminescence of N,N-dimethylaminobenzonitrile and its analogues.

To understand the effect of iptycene scaffolds on the locally excited (LE) and intramolecular charge transfer (ICT) fluorescence of aminobenzonitriles, a series of triptycene and pentiptycene derivatives were synthesized and their molecular structures and photophysical properties were characterized and compared with the parent phenylene systems, 4-(N-methylamino)benzonitrile (MABN), 4-(N,N-dimethylamino)benzonitrile (DMABN), and 4-(N-phenylamino)benzonitrile (PABN). The iptycene effect does not change the nature of the fluorescing states for each amino donor system, i.e., the MA, PA, and DMA series display LE-only, ICT-only, and LE-ICT dual fluorescences, respectively. However, the iptycene scaffolds impose a significant modification of the absorption and emission spectra, fluorescence quantum efficiency and lifetimes, and the interplay of LE and ICT states. The observed iptycene effect has been discussed with three factors: (1) steric effect on increasing the amino twist angle, (2) steric shielding of solvation to the aminobenzonitrile core, and (3) hyperconjugation interactions of the aminobenzonitrile core with the peripheral phenylene groups of iptycene.

A redox-gated slow-fast-stop molecular rotor.

A pentiptycene-derived p-phenylenediamine mimics a molecular double-rotor system that displays redox-dependent rotation rates for the amino rotors about the pentiptycene-amine C-N bond. The rotation is accelerated in the radical cation state but stopped in the di(radical cation) state. Electronic interplay of the two rotors is also discussed.

Pentiptycene building blocks derived from nucleophilic aromatic substitution of pentiptycene triflates and halides.

The nucleophilic aromatic substitution (S(N)Ar) reactions of the nitro-substituted pentiptycene triflate 15 with LiBr and LiI and the resulting halides 18 and 19 with N(3)(-), CN(-), and ArS(-) in DMF provide an efficient route toward pentiptycene halides and dihalides and other new pentiptycene building blocks. The reactivity of diaminopentiptycene in Pd-catalyzed C-N coupling reactions is also demonstrated.