Heptamethine Cyanine Dye-Doped Single-Walled Carbon Nanotube Electrodes for Improving Performance of HTL-Free Perovskite Solar Cells.

Perovskite solar cell (PSC) technology holds great promise with continuously improving power conversion efficiency; however, the use of metal electrodes hinders its commercialization and the development of tandem designs. Although single-walled carbon nanotubes (SWCNTs), as one-dimensional materials, have the potential to replace metal electrodes in PSCs, their poor conductivity still limits their application. In this study, the near-infrared (NIR)-absorbing anionic heptamethine cyanine dye-doped SWCNTs functioned in a dual role as an efficient charge-selective layer and electrode in PSCs.

A Rapid and Dual Optical CO -responsive Polydimethylsiloxane Elastomer with a Fluorinated Cyanine Dye.

We found that our optically CO -responsive polydimethylsiloxane (PDMS) elastomer rapidly and reversibly underwent both visible and fluorescent color changes in the presence of CO gas. Unlike conventional optically CO -responsive polymeric materials, it functions in totally dry gaseous conditions. The visible color and fluorescence of the elastomer sheet change after only 1 min of exposure to CO , and the sheet exhibits excellent repeatability in terms of color switching that persists for at least 20 times.

Diverse Synthesis of 2H-Isoindole-Based Polycyclic Aromatic Compounds.

1,3-Disubstituted N-aryl-2H-isoindoles have been synthesized by a cascade reaction of divinyl ethers, which are derived from easily available 4-bromoisocoumarins, with substituted anilines in HFIP. This cascade reaction consists of a ring-opening step through addition-elimination mechanism and the following 5-exo-tet type ring-closing step via the intramolecular nucleophilic substitution reaction. Thus obtained 2H-isoindoles have been derivatized to high-order nitrogen-containing polycycles including less accessible benzo[a]ullazines.

Synthesis of Near-Infrared-Absorbing Anionic Heptamethine Cyanine Dyes with Trifluoromethyl Groups.

A novel anionic heptamethine cyanine (HMC) dye with two trifluoromethyl groups that selectively absorb near-infrared light is synthesized. When contrasted with previously studied anionic HMC dyes with substituents such as methyl, phenyl, and pentafluorophenyl groups, the trifluoromethylated dye displays a red-shifted maximum absorption wavelength (for instance, 948 nm in CHCl) along with enhanced photostability. Furthermore, HMC dyes with broad absorption in the near-infrared region are synthesized by combining a trifluoromethylated anionic HMC dye with a cationic HMC dye as a counterion.

Aromatic fluorine atom-induced highly amine-sensitive trimethine cyanine dye showing colorimetric and ratiometric fluorescence change.

Herein, introducing multiple fluorine atoms into aromatic rings of trimethine cyanine dyes is proposed as a powerful method for dramatically increasing sensitivity to amines. The highly sensitive ratiometric fluorescence properties previously available only by intramolecular addition can be exploited in reactions with intermolecular amines or other nucleophiles.

Design, Regioselective Synthesis, and Photophysical Properties of Perfluoronaphthalene-Based Donor-Acceptor-Donor Fluorescent Dyes.

A one-step route to a series of perfluoronaphthalene-based donor (D)-acceptor (A)-D fluorescent dyes with various electron-donating groups was developed. The perfluoronaphthalene moiety in the D-A-D dyes served as a good electron-accepting aromatic ring with excellent intramolecular charge transfer properties, as determined by density functional theory calculations and measurements of the fluorescence properties in solution, in poly(methyl methacrylate) (PMMA) films, and in crystal form. Notably, replacing the naphthalene ring with perfluoronaphthalene in the D-A-D dyes carrying the phenothiazine moiety not only stabilized the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels but also reduced the energy band gap to change the emission color from blue to yellow.

Highly diastereo- and enantioselective organocatalytic synthesis of trifluoromethylated erythritols based on the generation of unstable trifluoroacetaldehyde.

Thus far, only a few methods for the asymmetric synthesis of erythritols bearing a trifluoromethyl group have been developed, and these methods present serious disadvantages such as the requirement of multiple steps for the preparation of their starting materials, low stereoselectivity, and the use of highly toxic reagents. Herein, we have developed a highly diastereo- and enantioselective organocatalytic method to synthesise erythritols bearing a trifluoromethyl group using (1) a commercially available organocatalyst to produce unstable trifluoroacetaldehyde in situ from its corresponding hemiacetal, followed by the simultaneous asymmetric carbon-carbon bond-forming reaction of the organocatalyst with an in situ-generated chiral enamine derived from 2,2-dimethyl-1,3-dioxane-5-one to obtain the corresponding aldol product in good yield (65-80%) with high diastereoselectivity (up to 94% de) and excellent enantioselectivity (up to >98% ee), (2) the highly diastereoselective reduction of the ketone moiety in the aldol product (up to 98% de), and (3) the deprotection of the acetal moiety.

Synthesis of Small Fluorescent Molecules and Evaluation of Photophysical Properties.

A series of aniline-based fluorophores were newly synthesized. To increase their fluorescence quantum yields, it was particularly important to substitute 3,3,3-trifluoroprop-1-enyl (TFPE) groups next to the amino group to benefit from an extended π-electron delocalization. Among these, 5-CN-2-TFPE-aniline was found to behave as an excellent fluorophore with a reasonable fluorescence quantum yield of 0.

Aromatic Fluorine-Induced One-Pot Synthesis of Ring-Perfluorinated Trimethine Cyanine Dye and Its Remarkable Fluorescence Properties.

We have developed a novel aromatic fluorine-induced one-pot synthesis of ring-perfluorinated trimethine cyanine dye without the use of a pyridine by reacting hexafluorobenzoindolenine with 5 equiv of methyl trifluoromethanesulfonate in mixed solvents of dimethylformamide and toluene. The thus-obtained ring-perfluorinated trimethine cyanine dye shows much better fluorescence properties, including intensity, quantum yield, and lifetime, than the nonfluorinated dye, not only in CHCl solution and the poly(methyl methacrylate) film but also in the powder state. Furthermore, ring-perfluorinated trimethine cyanine dye 2a shows better photostability toward white light-emitting diode irradiation than nonfluorinated dye trimethine cyanine dye 2b.

Wide-Range Near-Infrared Sensitizing 1 H-Benzo[ c, d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells.

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm) compared to the nonbenzene fused derivative SQ1 (4.

Convenient, functional group-tolerant, transition metal-free synthesis of aryl and heteroaryl trifluoromethyl ketones with the use of methyl trifluoroacetate.

A new convenient, functional group-tolerant, transition metal-free route to aryl trifluoromethyl ketones under mild conditions is described. The reaction of not only aryl Grignard reagents carrying reducible electrophilic functional groups, such as ester and cyano groups, but also electron-deficient nitrogen-containing heteroaryl Grignard reagents with methyl trifluoroacetate gives the corresponding aryl or heteroaryl trifluoromethyl ketones in good yields. Biological assays revealed that new heteroaryl trifluoromethyl ketones carrying 2,4-dimethoxypyrimidine and 3,5-dimethylisoxazole rings show good anti-tumor activities.

Rational Molecular Design and Synthesis of Highly Thermo- and Photostable Near-Infrared-Absorbing Heptamethine Cyanine Dyes with the Use of Fluorine Atoms.

Highly thermo- and photostable, near-infrared-absorbing heptamethine cyanine dyes were achieved with the use of fluorine-containing components. In particular, one prepared heptamethine cyanine dye, bearing a tetrakis(pentafluorophenyl)borate as a counter anion and an N-ethyl-2,2,2-trifluoroacetamido group at the meso position, showed not only a high decomposition temperature (Tdt ), but also very high photostability toward white LED irradiation.

Synthesis and Fluorescence Properties of Pyrimidine-Based Diboron Complexes with Donor-π-Acceptor Structures.

Pyrimidine-based diboron complexes bearing β-iminoenolate ligands and phenyl groups as bulky substituents on the boron atoms were synthesized as novel fluorescent dyes, and their fluorescence properties were investigated in solution and in the solid state. The diboron complexes with donor-π-acceptor structures showed positive solvatochromism in the fluorescence spectra. The cyano derivative exhibited the most dramatic redshift of the fluorescence maximum Fmax with increasing solvent polarity (from 551 nm in n-hexane to 710 nm in acetonitrile).

A Direct, Concise, and Enantioselective Synthesis of 2-Substituted 4,4,4-Trifluorobutane-1,3-diols Based on the Organocatalytic In Situ Generation of Unstable Trifluoroacetaldehyde.

A direct, concise, and enantioselective synthesis of 2-substituted 4,4,4-trifluorobutane-1,3-diols based on the organocatalytic asymmetric direct aldol reaction of an ethyl hemiacetal of trifluoroacetaldehyde with various aldehydes was examined. A catalytic amount (30 mol %) of commercially available and inexpensive l-prolinamide is quite effective as an organocatalyst for the catalytic in situ generation of gaseous and unstable trifluoroacetaldehyde from its hemiacetal, and a successive asymmetric direct aldol reaction with various aldehydes in dichloromethane at 0 °C, followed by reduction with sodium borohydride, gives 2-substituted 4,4,4-trifluorobutane-1,3-diols in moderate to good yields (31-84%) with low diastereoselectivities and good to excellent enantioselectivities (64-97% ee).

Synthesis, Absorption, and Electrochemical Properties of Quinoid-Type Bisboron Complexes with Highly Symmetrical Structures.

Novel bisboron complexes of bidentate ligands consisting of 1,4-benzoquinone and two pyrrole rings were synthesized by using a simple two-step reaction. In solution, the bisboron complexes showed absorption maxima at ∼620 and 800 nm, which were attributed to the allowed S0 → S2 and forbidden S0 → S1 transitions, respectively. The bisboron complexes did not show any fluorescence, probably because of their highly symmetrical structure which forbids the S0 → S1 transition.

Strategy to enhance solid-state fluorescence and aggregation-induced emission enhancement effect in pyrimidine boron complexes.

The synthesis and the solution/solid-state fluorescence properties of pyrimidine-based monoboron complexes differing in terms of the substituents [either two fluorine atoms (BF2 complex) or two phenyl groups (BPh2 complex)] on the boron atom are reported herein. Unrestricted C-Ar intramolecular rotation in the non-, trifluoromethyl-, and cyano-substituted derivatives resulted in negligible fluorescence in solution. On the other hand, methoxy- and dimethylamino-substituted analogues caused the restriction of the C-Ar intramolecular rotation and consequently resulted in relatively strong fluorescence in solution.

Solvatochromic fluorescence properties of pyrazine-boron complex bearing a β-iminoenolate ligand.

Pyrazine-based monoboron complexes bearing two fluorine atoms (BF2 complex) or two phenyl groups (BPh2 complex) on the boron atom were synthesized, and the fluorescence properties were investigated. The BPh2 complexes exhibited red-shifted maximum absorption and maximum fluorescence wavelengths and lower molar absorption coefficients than the corresponding BF2 complexes in n-hexane. The fluorescence quantum yields of the BPh2 complexes were higher than or comparable to the corresponding BF2 complexes owing to the relatively low nonradiative rate constants.

Synthesis and fluorescence properties of pyrimidine mono- and bisboron complexes.

Novel fluorescent mono- and bisboron complexes based on pyrimidine bearing β-iminoenolate ligands were synthesized, and their fluorescence properties were investigated. The nonsubstituted and trifluoromethyl-substituted monoboron complexes showed higher fluorescence quantum yield in solid state than in solution. The dimethylamino derivative of the monoboron complex exhibited positive solvatochromism in the fluorescence spectra.

Synthesis and fluorescence properties of thiazole-boron complexes bearing a β-ketoiminate ligand.

Novel fluorescent dyes, thiazole-boron complexes bearing β-ketoiminate ligands, have been synthesized, and their fluorescence properties were investigated. The BF(2) complexes showed a pronounced aggregation-induced emission enhancement effect because of the restriction of C-Ph intramolecular rotation. The BPh(2) complexes showed higher fluorescence quantum yields than the corresponding BF(2) complexes, both in solution and in the solid state.

Design of NIR-absorbing simple asymmetric squaraine dyes carrying indoline moieties for use in dye-sensitized solar cells with Pt-free electrodes.

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.

Synthesis and fluorescence properties of novel pyrazine-boron complexes bearing a β-iminoketone ligand.

A novel fluorescence dye based on pyrazine-boron complexes bearing a β-iminoketone ligand has been synthesized by using a simple two-step reaction. Synthesized complexes exhibited fluorescence in solution (F(max): 472-604 nm) and in the solid state (F(max): 496-624 nm). These complexes showed a larger Stokes shift (3690-4900 cm(-1)) than well-known boron dipyrromethene dyes (400-600 cm(-1), in most cases).

Organocatalytic asymmetric direct aldol reactions of trifluoroacetaldehyde ethyl hemiacetal with aromatic methyl ketones.

The organocatalytic asymmetric direct aldol reaction of trifluoroacetaldehyde ethyl hemiacetal with aromatic methyl ketones in the presence of a catalytic amount of (S)-5-(pyrrolidin-2-yl)-1H-tetrazole in dichloroethane at 40 °C proceeds smoothly to produce (R)-4,4,4-trifluoro-1-aryl-3-hydroxy-1-butanones in high yields with up to 90% ee.

Reversal of diastereoselectivity in reactions of the trifluoroacetaldehyde ethyl hemiacetal with enamines and imines: metal-free, complementary anti- and syn-selective synthesis of 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones.

A complete reversal of diastereoselectivity was observed for reactions of the trifluoroacetaldehyde ethyl hemiacetal with enamines and imines, derived from propiophenones, that produce 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones. This process serves as the first reliable, metal-free, complementary anti- and syn-selective method to prepare 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones.

Synthesis and fluorescence properties of a pyridomethene-BF2 complex.

A fluorescent dye, the pyridomethene-BF(2) complex, has been synthesized. Although pyridomethenes did not exhibit fluorescence, pyridomethene-BF(2) complexes exhibited fluorescence both in solution and in the solid state. The trifluoromethyl-substituted BF(2) complex formed a J-aggregate and showed the highest fluorescence quantum yield in the solid state among all pyridomethene-BF(2) complexes.

Effect of anchoring groups on electrochemical self-assembly of ZnO/xanthene dye hybrid thin films.

Three xanthene dyes with different anchoring groups, eosin Y (EY), dicarboxy-eosin Y (CEY) and sulfonated eosin Y (SEY) were employed to electrodeposit ZnO/dye hybrid thin films to study the effect of anchoring groups on the electrochemical self-assembly (ESA) of hybrid thin films. The adsorption stabilities of the dyes in oxidized form were in the order, CEY >> EY > SEY, as evaluated by Langmuir isothermal adsorption experiments. The reduction potential of dyes, the dependence on Zn(2+) concentration that reflects stabilities of complexes between reduced dyes and Zn(2+) ion, and the diffusion coefficients of dyes were determined by electrochemical measurements.