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We report on the synthesis of new fluorescent symmetrical 2,5-diaryl-1-methylimidazoles obtained in good yields by using direct C-H arylation synthetic strategies. Spectroscopic investigations in THF solution evidenced that the 2,5-diarylimidazole bearing the strong electron-withdrawing cyanoacrylate groups achieved the best trade-off between fluorescence maximum (518 nm), Stokes shift (115 nm) and a quantum yield of 25%. Highly homogeneous dispersions of the selected fluorophore in poly(methyl methacrylate) (PMMA) thin films (25 ± 5 μm of thickness) perfectly maintained the optical features in solution, thus providing a brilliant green emission and a markedly enhanced quantum yield of 55%. Photocurrent measurements of the PMMA collectors supported the use of 2,5-diaryl-1-methylimidazoles as accessible alternatives to perylene backbones for the development of LSC with optical efficiencies close to 7%. [ABSTRACT FROM AUTHOR]

We report on the preparation of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films doped with six new diketopyrrolopyrrole (DPP) fluorophores obtained in good yields by using simple N -alkylation and direct C H arylation synthetic strategies. Spectroscopic investigations in solution and in PMMA thin films combined with photocurrent measurements revealed that the branched alkyl chains were efficient in preventing DPP segregation from the PMMA matrix thanks to their higher steric hindrance. The aromatic substituent was found to expand DPP conjugation but favoured DPP adverse aggregation, thus affecting fluorescence emission and photocurrents of PMMA films. The worthwhile combination of the appropriate alkyl chain and aromatic moieties assured to achieve optical efficiency of 6.8% that was comparable to that of PMMA LSCs of the state-of-the art (7.2%). [ABSTRACT FROM AUTHOR]

In the present work, we report the vapochromic behaviour of PMMA films doped with small amounts of 1a :Zn fluorophore, a Zn 2+ adduct of the bisthienylethynylbipyridine ligand. 1a :Zn exhibited polarity-dependent changes in the fluorescence spectral properties when dissolved in solvents with different polarity index, indicating that its fluorescence states are of intramolecular charge transfer character. When 1a :Zn was dispersed in the PMMA matrix, its emission resulted barely influenced by the polymer environment. By contrast, 1a :Zn/PMMA films showed a significant variation of its emission with a 40 nm red-shift when exposed to a saturated atmosphere of dichloromethane. This vapochromic behaviour was much less evident when progressive amounts of methanol were added to dichloromethane due to both lower vapour pressure and limited interaction of the former with PMMA. The experiments revealed also that the rate constants associated with the vapochromic behaviour were affected by solvent composition and easily determined by luminescent experiments. [ABSTRACT FROM AUTHOR]

The synthesis of three 2-arylalkynyl-4,5-diarylimidazoles endcapped with typical electron-donating (ED) and electron-withdrawing (EW) groups (push-pull system) and their evaluation as fluorescent dyes for thin-film luminescent solar concentrators (LSCs) is described. These novel Y-shaped imidazole-based fluorophores were easily assembled in good chemical yields through a three-step synthetic sequence involving a double Suzuki arylation, followed by a dehydrogenative alkynylation, and a Knoevenagel condensation. Their optical and spectroscopic properties were analyzed both in solution and in poly(methyl methacrylate) (PMMA) films. All the molecules in PMMA films showed an intense, red-shifted emission between 540 and 575 nm with large Stokes shift (>120 nm), moderate-to-good fluorescence quantum yields (QY) and good device efficiencies (η dev), especially for compound 3. • New 2-arylalkynyl-4,5-diarylimidazoles were obtained via a simple three-step synthetic pathway. • Photophysical properties studied as a function of the different electron-withdrawing groups. • Homogeneous PMMA films containing the fluorophores were realized with max QY of 0.6 • Overall good LSC efficiencies were collected. [ABSTRACT FROM AUTHOR]

This study reports the effect of the crystallinity degree and structural order of the supramolecular architectures of the perylene derivative Paliogen® Black L0086 (P-black) on the near-infrared (NIR) transparent, reflective and cooling characteristics of 75 μm thick acrylic coatings. Notably, XRD and solid-state NMR investigations revealed that on passing from the commercially available P-black C to the synthetic form P-black S, the average crystallinity passed from 20 to 48% flanked by a superior structural order that enhanced the mean crystallite width from 21.7 to 39.1 nm and maximum length from 1.5 μm to 6.5 μm, as evidenced by SEM micrographs. UV-VIS-NIR spectroscopic analyses of the coated surfaces confirmed the NIR transparent and reflective characteristics of the P-black pigment that was particularly relevant in the case of the pigment synthetic form. NIR reflectance enhancements from 25% to 50% were actually recorded on black surfaces on passing from the commercial to the synthetic form of the pigment dispersed into the acrylic coatings. This feature was reflected on the solar reflectance and the cooling effect, with values boosted from 9.9% to 18.2% and from 2.3 °C to 3.8 °C, respectively. Image 1 • Commercial and synthetic Paliogen black were utilized as cool organic pigments. • Waterborne acrylic coatings were obtained on white and black substrates. • XRD, ssNMR and SEM investigations evidenced the superior structural order of the synthetic pigment. • SR measurements allowed to determine the cooling features of the prepared coatings. [ABSTRACT FROM AUTHOR]

We report on the synthesis of new push-pull imidazole-benzothiazole and thiazole-benzothiazole fluorophores obtained in good yields by using direct C H arylation synthetic strategies. Spectroscopic investigations in CHCl 3 solution evidenced that the 1,4-phenylene-spaced imidazole-benzothiazole bearing an electron-donating dimethylamino group achieved a trade-off between fluorescence maximum (516 nm), Stokes shift (165 nm) and a quantum yield higher than 0.4. Dispersions of the selected fluorophore in poly (methyl methacrylate) (PMMA) thin films mostly maintained the optical features in solution with significant light transmittance in the visible region (90% at 440 nm), and a brilliant green emission at 500 nm. Photocurrent experiments performed on PMMA thin films coated over high purity transparent glasses promoted their use in the development of colourless luminescent solar concentrators with optical efficiencies close to 6%. [ABSTRACT FROM AUTHOR]