Search

The search for deep-blue dyes with high luminescence efficiency in the aggregate state and high brightness is particularly important in optoelectronic application. Herein, based on a typical aggregation-induced emission (AIE) unit of tetraphenylpyrazine (TPP), four dyes were prepared by connecting it with chiral binaphthyl units via an acetylenic bond. The use of the TPP unit is critical to aggregation-enhanced emission (AEE) and deep-blue emission, whereas the merging of the binaphthyl unit is beneficial for molecular conjugation to remarkably improve absorption, photoluminescence (PL) quantum efficiency and brightness. Besides, the binaphthyl unit can serve as an axially chiral source to endow the deep-blue dyes with chirality. It was revealed that attaching a longer alkoxy chain to the dyes facilitates the formation of helical self-assemblies determined by chiral transfer but leads to an aggregation-caused emission (ACQ) effect. Moreover, using these deep-blue dyes as energy donors for energy delivery, other emissions and pure white light emission can be generated effectively via an energy transfer process based on a rational mixture of donors and acceptors in PMMA films. The device fabricated by coating this film onto a blue LED also emitted distinct and stable white light. This work provides a flexible way to design high-performance blue materials for potential applications. [ABSTRACT FROM AUTHOR]

The discovery of new reaction modes mediated by easily available substrates is an important research topic in organic synthesis. Allyl ketones and related compounds have been demonstrated to undergo γ- or α-selective additions to different electrophiles. We disclose here the Brønsted base-catalyzed reaction of allyl ketones and alkynyl 1,2-diketones, which undergo a unique α-selective addition/intramolecular aldol-type annulation/C–C bond cleavage process, and a series of 2-acyloxycyclopent-3-enones can be obtained under very mild conditions. [ABSTRACT FROM AUTHOR]

Four asymmetrical self-assembled monolayers (SAMs) consisting of two subunits with different Rh2 building blocks present a pronounced rectifying behavior. The rectification ratio (RR) increases on increasing the redox potential difference between the two Rh2 subunits, and the rectifying direction can be reversed by reordering the subunits in the assembly. [ABSTRACT FROM AUTHOR]

Three novel asymmetrical dimolybdenum dimers, [Mo2(DAniF)3]2(μ-OOCCOS) (DAniF = N,N′-di(p-anisyl)formamidinate) ([OO–OS]), [Mo2(DAniF)3]2(μ-S2CCO2) ([SS–OO]), and [Mo2(DAniF)3]2(μ-SSCCOS) ([SS–OS]), have been synthesized and characterized by either single-crystal X-ray crystallography or 1H NMR spectroscopy. The structural asymmetry for these compounds gives rise to a redox asymmetry, which enlarges the potential separation (ΔE1/2) between the two [Mo2] units. The mixed-valance (MV) species [OO–OS]+, [SS–OO]+ and [SS–OS]+, prepared by one-electron chemical oxidation of the neutral precursors, exhibit an intense and symmetrical intervalence charge transfer (IVCT) absorption band in the near-IR region, along with the high energy metal (δ) to ligand (π*) (ML) and ligand (π) to metal (δ) charge transfer (LMCT) absorptions. The LMCT band, which is absent in the neutral precursors, is reflective of the cationic [Mo2]+ unit in the MV species; therefore, it is evidenced that in the MV complexes optical electron transfer from the electron donor to acceptor occurs, while the thermal process is energetically unfavorable. The C(1)–C(2) bonds (1.44–1.48 Å) that connect the two [Mo2] units are significantly shorter than a C–C single bond, showing that the two Mo2 centers are strongly coupled. For the series, TD-DFT calculations show that the molecular orbitals have an unsymmetrical charge density distribution over the two dimolybdenum sites. For each of the complex systems, the calculated orbital energy gaps, SOMO(δ−δ)–LUMO(bridging ligand π*), HOMO−8(bridging ligand π)–SOMO(δ−δ) and SOMO(δ−δ)–HOMO−1(δ + δ), are in good agreement with the observed MLCT, LMCT and IVCT absorption band energies, respectively. The consistency in energy between the IVCT band and the SOMO(δ−δ)–HOMO−1(δ + δ) gap permits assignment of the MV complexes to Class III in the Robin–Day scheme. [ABSTRACT FROM AUTHOR]

Four thienylene (C4H2S) bridged Mo2 dimers, [Mo2(DAniF)3]2(μ-OOCC4H2SCOO) (DAniF = N,N′-di(p-anisyl)formamidinate), [Mo2(DAniF)3]2(μ-N(H)SCC4H2SCN(H)S), [Mo2(DAniF)3]2(μ-OSCC4H2SCSO) and [Mo2(DAniF)3]2(μ-SSCC4H2SCSS), have been synthesized and studied in terms of electronic coupling. The subtle structural differences between these compounds vary largely the extent of electron delocalization; consequently, a systematic transition from Class II to Class III via Class II–III is achieved, which is probed using spectral parameters of intervalence charge transfer (IVCT) absorption (band energy, intensity and shape) for the mixed-valence complexes. Significantly, the species in Class II–III displays a low energy, half cut-off and solvent-dependent IVCT band, while a high energy, less asymmetrical IVCT band is observed for the complex in Class III. These results give fresh and detailed understanding of the system transition. [ABSTRACT FROM AUTHOR]

Photoinduced electron transfer (ET) in Mo2 dimers, [Mo2(DAniF)3]2(μ-E2C(ph)CE2) (DAniF = N,N′-di(p-anisyl)formamidinate, E = O or S), has been studied by femtosecond transient spectral techniques. Using a 355 nm laser pulse, the δ electrons on the Mo–Mo quadruple bonds are selectively excited and subsequent charge separation yields diradicals [Mo2]Ṗ−–ph–[Mo2]Ṗ+ and [Mo2]–phṖ−–[Mo2]Ṗ+. The charge separation (CS) and recombination (CR) rates are derived by fitting the decay kinetic data of the excited states. Surprisingly, it is found that the CR rate constants (kCR-1, ∼1012 s−1) for [Mo2]Ṗ−–ph–[Mo2]Ṗ+ are larger than the data (kCR-2) for [Mo2]–phṖ−–[Mo2]Ṗ+ by about one order of magnitude, although in the first case, the ET distance is doubled and the electronic coupling between the donor and acceptor is weaker. Optical analyses reveal that the free energy changes (ΔG°) for the two CR processes correspond to the δ→δ* and the metal (δ) to bridging ligand (π*) transition energies, respectively, and thus, the ET kinetics is dominated likely by the driving force (−ΔG°). [ABSTRACT FROM AUTHOR]

Four asymmetrical self-assembled monolayers (SAMs) consisting of two subunits with different Rh2 building blocks present a pronounced rectifying behavior. The rectification ratio (RR) increases on increasing the redox potential difference between the two Rh2 subunits, and the rectifying direction can be reversed by reordering the subunits in the assembly.

Three novel asymmetrical dimolybdenum dimers, [Mo 2 (DAniF) 3 ] 2 (μ-OOCCOS) (DAniF = N,N'-di(p-anisyl)formamidinate) ([OO-OS]), [Mo 2 (DAniF) 3 ] 2 (μ-S 2 CCO 2 ) ([SS-OO]), and [Mo 2 (DAniF) 3 ] 2 (μ-SSCCOS) ([SS-OS]), have been synthesized and characterized by either single-crystal X-ray crystallography or 1 H NMR spectroscopy. The structural asymmetry for these compounds gives rise to a redox asymmetry, which enlarges the potential separation (ΔE 1/2 ) between the two [Mo 2 ] units. The mixed-valance (MV) species [OO-OS] + , [SS-OO] + and [SS-OS] + , prepared by one-electron chemical oxidation of the neutral precursors, exhibit an intense and symmetrical intervalence charge transfer (IVCT) absorption band in the near-IR region, along with the high energy metal (δ) to ligand (π*) (ML) and ligand (π) to metal (δ) charge transfer (LMCT) absorptions. The LMCT band, which is absent in the neutral precursors, is reflective of the cationic [Mo 2 ] + unit in the MV species; therefore, it is evidenced that in the MV complexes optical electron transfer from the electron donor to acceptor occurs, while the thermal process is energetically unfavorable. The C(1)-C(2) bonds (1.44-1.48 Å) that connect the two [Mo 2 ] units are significantly shorter than a C-C single bond, showing that the two Mo 2 centers are strongly coupled. For the series, TD-DFT calculations show that the molecular orbitals have an unsymmetrical charge density distribution over the two dimolybdenum sites. For each of the complex systems, the calculated orbital energy gaps, SOMO(δ - δ)-LUMO(bridging ligand π*), HOMO-8(bridging ligand π)-SOMO(δ - δ) and SOMO(δ - δ)-HOMO-1(δ + δ), are in good agreement with the observed MLCT, LMCT and IVCT absorption band energies, respectively. The consistency in energy between the IVCT band and the SOMO(δ - δ)-HOMO-1(δ + δ) gap permits assignment of the MV complexes to Class III in the Robin-Day scheme.

Four thienylene (C 4 H 2 S) bridged Mo 2 dimers, [Mo 2 (DAniF) 3 ] 2 (μ-OOCC 4 H 2 SCOO) (DAniF = N,N'-di(p-anisyl)formamidinate), [Mo 2 (DAniF) 3 ] 2 (μ-N(H)SCC 4 H 2 SCN(H)S), [Mo 2 (DAniF) 3 ] 2 (μ-OSCC 4 H 2 SCSO) and [Mo 2 (DAniF) 3 ] 2 (μ-SSCC 4 H 2 SCSS), have been synthesized and studied in terms of electronic coupling. The subtle structural differences between these compounds vary largely the extent of electron delocalization; consequently, a systematic transition from Class II to Class III via Class II-III is achieved, which is probed using spectral parameters of intervalence charge transfer (IVCT) absorption (band energy, intensity and shape) for the mixed-valence complexes. Significantly, the species in Class II-III displays a low energy, half cut-off and solvent-dependent IVCT band, while a high energy, less asymmetrical IVCT band is observed for the complex in Class III. These results give fresh and detailed understanding of the system transition.

Photoinduced electron transfer (ET) in Mo 2 dimers, [Mo 2 (DAniF) 3 ] 2 (μ-E 2 C(ph)CE 2 ) (DAniF = N,N'-di(p-anisyl)formamidinate, E = O or S), has been studied by femtosecond transient spectral techniques. Using a 355 nm laser pulse, the δ electrons on the Mo-Mo quadruple bonds are selectively excited and subsequent charge separation yields diradicals [Mo 2 ]˙ - -ph-[Mo 2 ]˙ + and [Mo 2 ]-ph˙ - -[Mo 2 ]˙ + . The charge separation (CS) and recombination (CR) rates are derived by fitting the decay kinetic data of the excited states. Surprisingly, it is found that the CR rate constants (k CR-1 , ∼10 12 s -1 ) for [Mo 2 ]˙ - -ph-[Mo 2 ]˙ + are larger than the data (k CR-2 ) for [Mo 2 ]-ph˙ - -[Mo 2 ]˙ + by about one order of magnitude, although in the first case, the ET distance is doubled and the electronic coupling between the donor and acceptor is weaker. Optical analyses reveal that the free energy changes (ΔG°) for the two CR processes correspond to the δ → δ* and the metal (δ) to bridging ligand (π*) transition energies, respectively, and thus, the ET kinetics is dominated likely by the driving force (-ΔG°).

Three novel [Mo2]-bridge-[Mo2] complexes were synthesized by a convergent assembling reaction of the dimetal precursor Mo2(DAniF)3(O2CCH3) (DAniF = N,N'-di(p-anisyl)formamidinate) with the bridging ligands terephthalamidine, terephthalamide and dithioterephthalamide. The structures of these compounds, [Mo2(DAniF)3]2[μ-1,4-{C(E)NH}2-C6H4] (E = NH (), O () or S ()), were determined, either by X-ray crystallography or (1)H NMR spectroscopy, to be the analogues of the terephthalate bridged dimolybdenum dimer. These compounds are structurally and electronically closely related by having the same structural skeleton and similar bonding parameters, which allowed us to analyze the differences between N, O and S atoms on the bridging ligand in promoting electronic interaction between the two [Mo2] units. In the electronic spectra, the metal to ligand charge transfer absorption bands, attributed to the HOMO (dδ) → LUMO (pπ*) transition, was red shifted as the variable atoms change from N to O to S. The mixed-valence species (+), (+) and (+), generated by one-electron oxidation of the neutral precursors and measured in situ, exhibited characteristic intervalence absorption bands, for which the energy and half-height bandwidth decreased from (+) to (+). Therefore, in comparison to O atoms, S atoms are capable of enhancing the electronic coupling between the two [Mo2] units, and the incorporation of N atoms to the bridging ligands slightly diminished the metal-metal interaction. The molecular structures and spectroscopic properties of these compounds were simulated by theoretical calculations at DFT level on the simplified models, which gave results consistent with the experimental observations.

A μ(4)-Cl bridged anionic sodalite-type porous metal-organic framework (Et(2)NH(2))(3)[(Cu(4)Cl)(3)(TTCA)(8)]·26DEF was synthesized, in which Et(2)NH(2)(+) can be exchanged by Li(+) cations. The results of gas measurements indicate that Et(2)NH(2)(+) and Li(+) are beneficial for methane and hydrogen storage, respectively.

Two supramolecular assemblies were developed by the dimmolybdenum paddlewheel complex trans-Mo(2)(DAniF)(2)(O(2)CC(6)F(5))(2) (1) (ancillary ligand DAniF = N,N'-di-(p-anisyl)formamidinate) through intermolecular offset face to face C(6)F(5)···C(6)F(5) interactions. The two networks are different because of the presence and absence of tetrahydrofuran (THF) axial coordination to the Mo(2) units, but feature commonly short interplanar distances between the two paired perfluorophenyl groups, that is, 3.30 Å and 3.23 Å, respectively, which are similar to the shortest intermolecular C···F contacts between two atoms in meta and ortho positions. Consistently, as indicated by the Mulliken population analysis, the dipole moments for the meta and ortho C-F bonds are considerably enlarged because the pentafluorobenzoate groups are bonded to the dimetal unit. In comparison, X-ray structural and theoretical analyses were also made for the parent molecule pentafluorobenzoic acid. The resultant data show that charge distribution on the perfluorophenyl group has a major influence on the C(6)F(5)···C(6)F(5) binding mode. Therefore, it is evidenced that the dimetal unit plays a role in further polarizing the highly polarized C-F bonds and the intermolecular perfluorophenyl-perfluorophenyl interactions are dominated by the C···F dipole-dipole interaction, rather than aromatic-aromatic π-π stacking., (This journal is © The Royal Society of Chemistry 2011)

An unprecedented organic-inorganic hybrid material with 3D inorganic and 3D organic connectivity has been constructed based on Cd(II) and tetrazolate-5-carboxylate, which shows a highly connected trinodal (4,8,16-c) topological net and SHG activity.