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Disiloxane-linked decathiophene and dodecathiophene polymers were prepared and their optical properties were examined. Compared with the monosilane-linked congeners reported previously, these polymers showed slightly redshifted absorption and PL bands in solution. Interestingly, the PL bands were redshifted when the spectra were measured in film, and the redshifts became pronounced as the silicon linkers were elongated from monosilane to disiloxane. This is likely due to the enhanced aggregation of the oligothiophene units, reflecting the improved flexibility of the silicon linkers.

The introduction of unconventional elements into π-conjugated systems has been studied to manipulate the electronic states and properties of compounds. Herein, boron- and germanium-containing hybrid macrocycles, as a new class of element-hybrid conjugated systems, have been synthesized. The palladium-catalyzed Stille cross coupling of bis(bromothienyl)borane and bis(trimethylstannylthienyl)- or bis(trimethylstannylphenyl)-substituted dithienogermoles as the boron- and germanium-containing building blocks, respectively, produced a mixture of several macrocyclic compounds. Single-crystal X-ray analysis of the 2:2 coupling product revealed a planar structure with a cavity inside the macrocycle. The optical properties of the macrocyclic products indicated rather small electronic interactions between the building units. However, intramolecular photoenergy transfer from the dithienogermole unit to the boron unit was clearly observed with respect to the fluorescence spectra.

Among conjugated materials, p–π* conjugated polymers have attracted much attention due to their unique electronic structures derived from the orbital interaction between the empty p-orbital on boron and the π*-orbitals of the adjacent π-systems. On the other hand, borepin, an isoelectronic ring system of tropylium ions, has been investigated as an aromatic system containing heteroatoms. In this work, the first examples of p–π* conjugated polymers consisting of tetracyclic borepin structures with different conjugation pathways were prepared. Optical investigations revealed that the borepin polymers have more extended conjugations than conventional p–π* conjugated polymers. Furthermore, the two borepin polymers exhibited drastically different optical responses when cyanide was added to the solution. Photophysical measurements and DFT calculations disclosed the characteristic electronic effects of the borepin structures and the influence of different conjugation pathways.

Spiro-condensed dithienogermoles with electron-donating aromatic substituents were prepared by Pd-catalyzed Stille coupling reactions of spirobi(dibromodithienogermole) and the corresponding trimethylstannylarene derivatives. Their optical and electrochemical properties were examined in comparison with those of related model compounds without the germole ring systems and the spiro-condensed unit, indicating that the spiro-condensed dithiengermole systems play roles in the enhancement of the conjugation. Perovskite solar cells (PSCs) were fabricated using triphenylamine-containing spirobi(dithienogermole) (sDTG-tpa) as the hole-transporting material (HTM). The PSCs showed the maximal photo-current conversion efficiency of 14.67%, which was higher than that of a similar device with spiro-OMeTAD as the HTM (9.53%), indicating the superior performance of sDTG-tpa as HTM compared with spiro-OMeTAD, a typical HTM for PSCs.

The incorporation of tricoordinate boron into conjugated systems is of current interest in the field of organic electronics. In this study, a tricoordinate boron-embedded thiophene-based bistricyclic aromatic ene (BAE) was synthesized as a new boron-containing conjugated system. The combination of tricoordinate boron and fused thiophene rings imposed the twisted conformation in the BAE structure, resulting in the narrow energy absorption with the low-lying LUMO. Preliminary studies on the application of the highly electron-deficient boron-embedded BAE to organic field-effect transistors (OFETs) were also performed, revealing its moderately high electron mobility.

Copolymerization of bis[3-(triethoxysilyl)propyl]amine (BTESPA) and

Platinum-catalyzed reactions of layered polysilane (Si6H6)n with arylacetylenes provided arylethenyl-substituted polysilanes. The polymers exhibited σ-π conjugation between the arylethenyl units an...

An addition of two equivalents of Lewis acid with Lewis basic 9,10-dicyanoanthracene enabled tuning of the spatial and electronic properties of the parent molecule. An investigation on optical prop...

The optical properties of triphenylamine- and quinoline-containing silicon nanosheets prepared by treatment of layered polysilane (Si6H6)n with p-(aminomethyl)triphenylamine and 4-(aminomethyl)quin...

Pyridinothienogermoles (PyTGs) were prepared by the reaction of dilithiopyridylthiophene with dichlorodi(n-octyl)germane and dichlorodiphenylgermane, and their electronic states were investigated by optical measurements and density functional theory (DFT) calculations. Bromination of trimethylsilyl-substituted PyTG with N-bromosuccinimide gave PyTG bromide, and palladium-catalyzed Stille coupling reactions of bromide with diphenyl[(trimethylstannyl)phenyl]amine and N-[(trimethylstannyl)phenyl]carbazole provided donor–acceptor compounds with pyridine as the acceptor and triphenylamine or phenylcarbazole as the donor. These compounds showed clear solvatochromic properties in the photoluminescence (PL) spectra. Bi(pyridinothienogermole) was prepared by the Stille coupling of DPyG bromide and trimethylstannyl-substituted DPyG. The Lewis basicity of the pyridine ring made it possible to use these DPyG derivatives as ligands for complex formation. Protonation and complex formation of the PyTG pyridine unit with...

Antimony- and bismuth-bridged bipyridyls (dipyridinostibole and dipyridinobismole; DPySb and DPyBi) were prepared by the reactions of dilithiobipyridyl with dibromophenylstibine and diiodophenylbis...

The reaction of 4,4-dichloro-2,6-di(n-butyl)dithienogermole (DTGCl) with lithium naphthalenide yielded a dark blue solution, which was treated with methyl iodide to provide a 4,4-dimethylated product in 67% isolated yield, indicating the formation of 4,4-dilithio-2,6-di(n-butyl)dithienogermole (DTGLi). Similar treatment of the dark blue solution containing DTGLi with trimethylsilyl fluoride and water gave the corresponding 4,4-disubstituted products. When trimethylsilyl chloride was used, however, no silylated products were obtained, likely due to steric hindrance. The reaction of DTGLi with DTGCl gave poly[2,6-di(n-butyl)dithienogermole-4,4-diyl], whose UV–vis absorption spectra revealed a more extended conjugation than that of a previously prepared product from the Wurtz-type coupling of DTGCl with sodium. Reinvestigation of the electronic states of poly(dithienogermole-4,4-diyl) derivatives on the basis of crystal orbital calculations was also accomplished.

Dithienosilole (DTS) and dithienogermole (DTG) are useful building units of π-conjugated organic materials. In the present work, donor-π-acceptor (D-π-A) dyes with bis(dihexyloxyphenyl)aminophenyl, DTS or DTG, and pyridine or cyanoacrylic acid as the donor (D), the π-conjugated linker (π), and the acceptor (A) units, respectively, were prepared and their optical properties were investigated. The D-π-A dyes exhibited strong absorption in the visible region, indicating efficient intramolecular donor-acceptor interaction. The addition of trifluoroacetic acid to solutions of pyridine-containing dyes led to red-shifts of the absorption bands as a result of pyridinium salt formation. Similar red-shifts were observed for cyanoacrylic acid dyes, which were due to the enhanced formation of neutral dyes relative to the separated ion pairs. The D-π-A dyes, however, showed similar absorption spectra when attached to the TiO2 surface, indicating that the dye-TiO2 electronic interaction was rather weak. In contrast to the finding that these dyes exhibited similar optical properties regardless of the π-linker (i.e., DTS or DTG), dye-sensitized solar cells (DSSCs) based on DTG-containing dyes exhibited superior performance compared to those based on DTS-containing dyes. Electrochemical impedance spectroscopy measurements supported the higher performance of the DSSCs with DTG-containing dyes.

The coordination chemistry of our recently isolated bis(diphenylphosphinyl)-functionalized dipyrido-annulated NHC (N-heterocyclic carbene), dpaP2-NHC, towards copper(I) and silver(I) has been studied. Based on dpaP2-NHC, two dinuclear silver and copper complexes [2, (Ag2L2) and 3, (Cu2L2)], two tetranuclear copper complexes {4, [Cu4L2(NCMe)2] and 6, (Cu4LBr4)} and a pentanuclear copper complex [5, (Cu5L2Br3)] exhibiting strong intramolecular metal–metal interactions were achieved and characterized. All the complexes exhibited dynamic behavior in solution, in which the NMR coalescence of 2 was well resolved at low temperature (below 208 K) and dissociation for 2 was observed according to the calculated Eyring plot. Ag2L2 (2) shows a similar coordination sphere to that of our previously reported gold complex Au2L2; Cu2L2 (3) features a rare μ2-bridging carbene and a terminal carbene; Cu4LBr4 (6) is neutral and monomeric, in which four copper atoms were rigidly fixed by the tridentate dpaP2-NHC ligand and bromide anions. All the complexes (2–6) were luminescent at room temperature, in which 4–6 provided phosphorescence at 77 K. Based on the comparison of the emission bands with dpaP2-NHC, we conclude that the electronic transitions of 2–6 can be attributed to the ligand-centered (LC) transitions.

Dithienogermole derivatives S- and R-1 possessing phenylisoxazoles and chiral side chains were synthesized. The helical assembly of 1 in methylcyclohexane exhibited circularly polarized luminescence (CPL). The CPL signals of the assembly in the elongation regime were inverted with respect to those in the nucleation regime.

Applications of highly electron-deficient organoborenium ions in conjugated materials remain scarce due to their low stability toward air and moisture. We report here the preparation of benzo[d]dithieno[b,f]borepinium ions as air-stable π-conjugated heterocycles and their conversion into the first dimeric borenium cations, which exhibit very low lying LUMOs and enhanced fluorescence as a result of extended conjugation.

Surface modification of inorganic oxide with organic modifiers is an important process in areas of surface and interface engineering. In this paper, we report the hydrophobic modification of SiO2 s...

New aminosilanes with hydrolysable Si-N bond(s) were prepared by the amination of chlorosilanes and used as hydrophobic modifiers of SiO2 surface. The aminosilanes are rather stable towards hydrolysis in air compared to their chlorosilane analogs. The modified SiO2 was applied as a gate insulator of an organic thin-film transistor with a vapor-deposited film of pentacene as the active material. The transistor with the aminosilane-modified SiO2 showed two- to threefold higher hole mobility than the device with bare SiO2.

Borepin is a seven-membered unsaturated ring system containing a tricoordinate boron. Although many borepin compounds annulated with aromatic systems have been reported to date, only one [b,d,f]-annulated tetracyclic borepins has been synthesized. In the present study, we synthesized benzo[d]dithieno[b,f]borepins as a new class of building blocks for functional materials motivated by the following structural features: (1) the high chemical stability of dithieno[b,f]borepin species; (2) the highly conjugated tetracyclic system with a borepin ring; and (3) electronic structures that are easily tuned by the introduction of functional groups on the annulated benzene ring. The prepared borepins were stable in air both in solution and as solids, and the electronic states could be finely tuned by changing the substituents on the benzene ring. Interestingly, DFT calculations revealed that the LUMO and LUMO+1 energy levels were strongly affected by the benzo[d]-annulation, depending on the boron-bridged positions ...

Conjugated polymers composed of tricoordinate boron and π-conjugated units possess extended conjugation with relatively low-lying LUMOs arising from pB–π interactions. However, donor–acceptor (D–A) polymers that feature triorganoboranes alternating with highly electron-rich donors remain scarce. We present here a new class of hybrid D–A polymers that combine electron-rich dithienosiloles or dithienogermoles with highly robust tricoordinate borane acceptors. Polymers of modest to high molecular weight are readily prepared by Pd-catalyzed Stille coupling reaction of bis(halothienyl)boranes and distannyldithienosiloles or -germoles. The polymers are obtained as dark red solids that are stable in air and soluble in common organic solvents. Long wavelength UV-vis absorptions at ca. 500–550 nm indicate effective π-conjugation and pronounced D–A interactions along the backbone. The emission maxima occur at wavelengths longer than 600 nm in solution and experience further shifts to lower energy with increasing solvent polarity, indicative of strong intramolecular charge transfer (ICT) character of the excited state. The powerful acceptor character of the borane comonomer units in the polymer structures is also evident from cyclic voltammetry (CV) analyses that reveal relatively low-lying LUMO levels of the polymers, enhancing the D–A interaction. Density functional theory (DFT) calculations on model oligomers further support these experimental observations.

We report the discovery of a novel series of 1,5-bisphenylpyrazoles as potent MALT1 inhibitors. Structure–activity relationship exploration of a hit compound led to a potent MALT1 inhibitor. Compound 33 showed strong activity against MALT1 (IC50: 0.49 μM), potent cellular activity (NF-κB inhibition and inhibition of IL2 production), and high selectivity against caspase-3, -8, and -9. The results of a kinetics study suggest that compound 33 is a non-competitive inhibitor of MALT1 protein.

Alternating copolymers composed of dithienogermole and thiophene, bithiophene, and dithienosilole ( pDTG2-T , pDTG2-2T , and pDTG2-DTS2 ) were prepared by the Stille coupling reactions of dibromodithienogermole and the respective distannylthiophene derivatives. Examination of their electronic states with respect to their UV–vis absorption spectra and cyclic voltammograms (CVs) revealed enhanced conjugation in the order of pDTG2-T . However, the interchain π–π interaction of the polythiophenes in the film state was enhanced in the opposite order. The highest organic thin film transistor (OTFT) mobility was obtained for pDTG2-2T , indicating that the intermolecular π–π interaction affected the OTFT activity of the films more significantly than the intramolecular π-conjugation in these polythiophenes.

Polysilsesquioxane films prepared by the copolymerization of dithienogermole dichloride (DTG-Cl) and bis(triethoxysilyl)ethane (BTESE) exhibited sensing properties towards nitroaromatic compounds. These films also responded to aniline, a potential interfering matrix. However, selective sensing of nitrobenzene was possible and the film containing 2,6-dithienyldithienogermole as the sensing fluorophore underwent photoluminescence quenching only with nitrobenzene, but not with aniline.

When the caged germasesquioxanes hexakis(cyclohexylgermasesquioxane) and hexakis(n-octylgermasesquioxane) (GT6Cy and GT6Oc) were irradiated with γ-rays in 2-methyltetrahydrofuran (2-MTHF) glass matrices at 77 K, anisotropic ESR signals ascribed to their radical anions were observed. DFT calculations of a model radical anion, [hexakis(methylgermasilsesquioxane)]− (GT6Me–), indicated unsymmetrical distribution of the SOMO (singly occupied molecular orbital), in agreement with the anisotropy of the ESR signals. To better understand the electronic states of the caged germasesquioxanes, hexakis(dimethylaminophenylgermasesquioxane) (GT6An) was prepared and its photoluminescence (PL) properties were investigated. Interestingly, the PL efficiency of GT6An was much lower than that of dimethylaniline itself, likely because of the electron transfer from the photoexcited dimethylaniline unit to the germasesquioxane cage.

(D)2–π–A type boron dipyrromethene (BODIPY) dyes OMK-PY and OMK-CA bearing a pyridyl group or cyanoacrylic acid group, respectively, at the end of 8-positions on the BODIPY core, as an electron-withdrawing anchoring group to adsorb onto the TiO2 electrode and two diphenylamine–thienylcarbazole moieties as an electron-donating unit at the 3- and 5-positions on the BODIPY core, were designed and developed as a photosensitizer for dye-sensitized solar cells (DSSCs). It was found that the two BODIPY dyes adsorbed on a TiO2 film show a strong and broad absorption band in the range of 600 to 850 nm, and the onset of the absorption band reached 900 nm, that is, OMK-PY and OMK-CA possess the near-infrared (NIR) adsorption ability as well as the panchromatic adsorption ability, and good adsorption ability onto the TiO2 electrode. Moreover, cyclic voltammetry demonstrated that the two BODIPY dyes show two reversible oxidation waves, thus indicating that the redox processes of OMK-PY and OMK-CA are very stable. On the basis of the experimental results and density functional theory calculation, we propose that the (D)2–π–A BODIPY structure with two diphenylamine–thienylcarbazole moieties as strong electron-donating units at the 3- and 5-positions on the BODIPY core is an effective strategy to lead a high light-harvesting efficiency (LHE) in the range of visible light to NIR light, although the DSSCs based on (D)2–π–A type BODIPY dyes that have been developed in this current stage showed low photovoltaic performances.

Two-dimensional starlike molecule 7 consisting of benzothiadiazole-thiophenylphenyltriazine groups and pentamethyldisilanyl substituted thienylene units that extend to three directions was synthesized by the reactions of 2,4,6-tris[4-(4-hexyl-5-(7-(3-hexyl-5-iodothiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)-thiophen-2-yl)phenyl]-1,3,5-triazine ( 5 ) with the pentamethyldisilanylthienyl substituted stannyl derivative ( 6 ). UV-visible absorption and fluorescence properties of starlike molecules 4 and 7 have been investigated in dioxane and in the solid state. The application of TiO 2 -electrode coated on the surface with the use of 7 to dye-sensitized solar cells has been discussed.

Phosphine-functionalized N-heterocyclic carbene (NHC) ligands are known to complex group 11 metal centers to form multinuclear complexes with photoluminescence properties. This study reports a structurally rigid ortho-substituted dipyrido-annulated NHC with T-shape coordination geometry and its di- and tetranuclear gold(I) complexes. The free ligand as well as all metal complexes are found luminescent at room temperature and phosphorescent at 77 K. Although metal d10–d10 interactions are evident based on their solid-state structures, their effect on the photoemission is limited, most likely due to the weak coordination of the ligand to the metal centers in solution.

Biaryls, such as bithiophene and bipyridyl, are intramolecularly bridged by group 14 heavy elements, silicon, germanium, and tin, to produce element blocks having condensed tricyclic systems with silole, germole, and stannole as the center ring. These bridged biaryls exhibit interesting properties arising from the characteristics of both the biaryl units and the bridging elements. In this chapter, recent development in functional organic materials containing the bridged biaryl systems as the core structure is described. The electronic states and properties of the bridged biaryls are discussed on the basis of the results of optical and electrochemical measurements and quantum chemical calculations, to explore how the element bridges contribute to the improvement of desired properties, such as photoluminescent, carrier transport, photovoltaic, and chromic properties.