This work reports the effect of stiffness and conformation of chain-like polymers on wrapping behaviors around single-walled carbon nanotubes (SWNT). As a model of chain-like polymers, three kinds of poly(dialkylsilane) (PSi)s with random-coiled, flexible, and semiflexible main chains were employed. Complexes of PSi and SWNT were prepared using mechanochemical high-speed vibration milling (HSVM). Stiffness-dependent polymer wrapping behaviors were investigated using combinational analyses with a differential scanning calorimeter, transmission electron microscopy, and atomic force microscopy. Furthermore, the conformational behaviors of the PSi's wrapped onto SWNTs were characterized spectroscopically with ordinary UV spectroscopy. Random-coiled and flexible PSi's were successfully wrapped onto small bundles of SWNTs, in which their conformations were changed to fit the surface curvatures of the SWNTs. However, semiflexible PSi could not form a complex with SWNTs, and its conformation remained unchanged even after the same HSVM process. Knowledge gained from this study may lead to a new approach to molecular design of chain-like polymers for efficient wrapping materials for SWNTs.

The reaction of 3,3′-dilithiobithiophenes with tetrachlorogermane afforded 4,4-dichlorodithienogermoles, which readily underwent substitution on the central germanium atom. Reactions of a dichlorodithienogermole with LiAlH 4 , MeLi, Me 2 NC 6 H 4 Li, and C 6 F 5 MgBr gave the corresponding Ge-substituted products. Dihydrodithienogermole obtained from the reaction with LiAlH 4 was further treated with LDA to give a dimer whose structure was verified by a single-crystal X-ray diffraction (XRD) study. Hydrolysis of dichlorodithienogermoles provided cyclotetragermoxanes. Their optical properties were examined with respect to the UV absorption and fluorescence spectra. It was found that one of the cyclotetragermoxanes responded to a nitorobenzene vapor in the solid state, decreasing the PL intensity.

We demonstrate that multi‐fluorinated boron‐fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor‐acceptor (D‐A) type π‐conjugated polymers. Position‐dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near‐infrared (NIR) emission (λPL=758–847 nm) with high absolute photoluminescence quantum yield (ΦPL=7–23%) originating from low‐lying LUMO energy levels of the BAz moieties (−3.94 to −4.25 eV). Owing to inherent solid‐state emissive properties of the BAz units, deeper NIR emission (λPL=852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D‐A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron‐accepting unit through fine‐tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials.

The considerably conjugated π systems of the group 14 dithienometallole-linked ethynylene-conjugated porphyrin dimers (1Ms) were described based on comprehensive experimental and theoretical studies. The electronic absorption spectra of 1M displayed a large splitting in the Soret band and a red-shifted Q-band, indicating that the dithienometallole spacer was effective in facilitating the porphyrin-porphyrin electronic coupling. Torsional planarization behaviors of 1M were observed in the time-resolved fluorescence spectra. Density functional theory (DFT) calculations revealed that the dithienometallole spacer is an ideal partner for the ethynylene-conjugated porphyrin to produce fully delocalized highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels due to their similar HOMO and LUMO levels. Finally, 1M exhibited a strong propensity for the quinoidal-cummulenic conjugation in the dithienometallole spacer when in a photoexcited state.

We describe herein a robust π-conjugated molecules with solid-state emission in the near-infrared (NIR) region (ΦF = 0.03–0.06).

Most organic luminescent dyes usually show poor emission in solid due to aggregation‐caused quenching due to nonspecific intermolecular interaction, such as π–π stacking. Furthermore, since commodity molecules having near‐infrared (NIR) emission properties tend to have extended π‐conjugated systems, development of luminescent organic materials with solid‐state NIR emission has been still challenging. Herein, the series of the azobenzene complexes with the perpendicularly‐protruded aryl derivative at the boron atom toward π‐conjugated system is synthesized. From the optical measurements, it is shown that these complexes can show crystallization‐induced emission enhancement behaviors. The donor–acceptor type π‐conjugated polymers composed of the azobenzene complexes are also synthesized. Highly‐efficient NIR emission from the phenyl‐substituted polymers both in solution (λPL = 742 nm, ΦPL = 15%) and film states (λPL = 793 nm, ΦPL = 9%) is obtained. Furthermore, emission wavelengths can be tuned by changing the substituent at the boron atom to the modified aryl groups. From mechanistic studies including theoretical calculations, it is shown that electronic interaction is allowable between the aryl substituent to the π‐conjugated system through the tetradentate boron.

Antimony-and bismuth-bridged bipyridyls (dipyridinostibole and dipyridinobismole; DPySb and DPyBi) were prepared by the reactions of dilithiobipyridyl with dibromophenylstibine and diiodophenylbismuthine. Xray diffraction studies of the crystal structures revealed a high planarity of the heterole ring. Cyclic voltammograms obtained in acetonitrile indicated enhanced electron affinity in comparison to a bridge-free bipyridyl. These compounds showed weak fluorescence at room temperature and visible phosphorescence at 77 K with emission maxima and lifetimes of λ max = 453 nm and τ = 1.03 ms for DPySb and λ max = 454 nm and τ = 0.26 ms for DPyBi, respectively. Solid-state phosphorescence was also observed from these dipyridinoheteroles at 77 K. Their copper complexes were prepared by interaction with Cu 2 I 2 (PPh 3 ) 3 , which produced red phosphorescence in the solid state at room temperature.

The development of solid-state near-infrared (NIR)-emissive π-conjugated polymers (CPs) has been still difficult due to lack of valid guidelines for avoiding aggregation-caused quenching. To obtain solid-state emission, we designed new strong electron acceptors by employing boron-fused azobenzene complexes with vertically projected bulky substituents at boron, which can prevent the π-surface from intermolecular interactions. Herein, we demonstrate donor–acceptor-type CPs with NIR emission properties. In summary, the CP with a bithiophene donor bearing the bulkiest substituent exhibited excellent solid-state NIR emission (λFL = 806 nm, ΦFL = 7.5%). In addition, the longest emission maximum was obtained from the CP containing cyclopentadithiophene (λFL = 923 nm, ΦFL = 0.9%). The concept for the introduction of vertically projected bulky substituents at boron opens a new research field on solid-state NIR-emissive materials.