We have synthesized a novel class of imidazole-based excited-state intramolecular proton-transfer (ESIPT) materials, i.e., hydroxy-substituted tetraphenylimidazole (HPI) and its derivative HPI-Ac, which formed large single crystals exhibiting intense blue fluorescence and amplified spontaneous emission (ASE). Transparent, clear, and well-defined fluorescent single crystals of HPI-Ac as large as 20 mm x 25 mm x 5 mm were easily grown from its dilute solution. From the X-ray crystallographic analysis and semiempirical molecular orbital calculation, it was deduced that the four phenyl groups substituted into the imidazole ring of HPI and HPI-Ac allowed the crystals free from concentration quenching of fluorescence by limiting the excessive tight-stacking responsible for intermolecular vibrational coupling and relevant nonradiative relaxation. Fluorescence spectral narrowing and efficient ASE were observed in the HPI-Ac single crystal even at low excitation levels attributed to the intrinsic four-level ESIPT photocycle.

ProDOT-Me 2 [25], , and BEDOT-B(OC 12 ) 2 [27] were obtained as described previously. 4 cm 4 cm sized 3M transparency film substrates (PP 2500, contact angle = 9.5) were used without any pre-cleaning. 5 wt.-% DEG or 5 wt.-% NMP mixed with 95 wt.-% PEDOT±PSS (Agfa) were stirred in a flask for 1 h at room temperature. This dispersion was then spincoated onto the plastic substrates at 1000 rpm. The resulting films were placed in an oven at 120 C for 5 min. Films were then dried in a vacuum oven overnight and stored in a dessicator until use. The surface resistance of the resulting films was measured using a standard two-probe method. Conductivity results were obtained using a four-probe method. Electrochromic polymer films were electrosynthesized on PEDOT±PSS electrodes from 10 mM solutions of monomer in 0.1 M tetrabutylammonium perchlorate/acetonitrile (TBAP/ACN) at the oxidation potential of the monomer (vs. silver wire). The composition of the gel electrolyte used in the ECDs was TBAPF 6 /PMMA/PC/ACN in a ratio of 3:7:20:70 by weight. The gel electrolyte was allowed to evaporate at the edges to seal the device. The ECDs were switched on the bench using an EG&G model PAR273 A potentiostat/galvanostat. Optical characterization of the ECDs was carried out using a Cary 500 UV-vis-NIR spectrophotometer. Fluorescence imaging in polymer films is of growing interest owing to its potential application to optical recording. To date, various organic fluorophores dispersed in or attached to polymer matrices have been used to achieve luminescence activation or deactivation by selective photochemical reaction.[1±4] Representative methodologies include photoacid-catalyzed chemical amplification [1±2] and photoacid-induced protonation by one-photon [3] and two-photon processes.[4]Though a number of examples on photoacid-induced definition of fluorescent areas have been reported, none of them have discussed the stability of the patterned image. Reactivity to photoacid is an important factor to be considered with regard to image stability because probe light for fluorescence readout inevitably generates a small but significant amount of photoacid that is capable of reducing the image contrast by inducing the accidental recording in unrecorded area. This undesirable reaction, i.e., image volatility, is particularly problematic for protonation-type imaging because photoacid is used in large amounts as a reagent rather than as a catalyst. Accordingly, for the long-term stability of a patterned image, appropriate control of recording reactivity, i.e., a limited basicity of the fluorophore is necessary to achieve photochemically gated protonation such that protonation occurs only under the selective recording light (the photoacid-abundant condition).Based on this consideration, we have designed a novel quinoline-based fluorophore with controlled basicity (HPQ). As shown in Scheme 1, the structure of HPQ is characterized by intramolecular hydrogen (H-) bonding that is introduced to reduce basicity to extrinsic acid by intrinsic blocki...

No abstract