Full Color Tunable Aggregation-Induced Emission Luminogen for Bioimaging Based on an Indolizine Molecular Framework.

By taking advantage of a unique mechanism of aggregation-induced emission (AIE) phenomena, AIE luminogens (AIEgens) have been provided as a solution to overcome the limitations of conventional fluorophores bearing the feature of aggregation-caused quenching (ACQ) phenomena. Especially, AIEgens paved the way to develop fluorogenic probes ideal for fluorescent imaging in live cell conditions. Despite the high demand for discovery of new AIEgens, it is still challenging to find a versatile molecular platform to generate diverse AIEgens. Herein, we report a new colorful molecular framework, Kaleidolizine (KIz), as a molecular platform for AIEgen generation. The KIz system allows systematic tuning of the emission wavelength from 455 to 564 nm via perturbation of the electron density of substituents on the indolizine core. Increasing the water fraction of the KIz solution in the THF/water mixture induces the fluorescence intensity increase up to 120-fold. Crystal structure analysis, computational calculations, and solvatochromism studies suggest that a synergistic effect between the intramolecular charge transfer and restriction of intramolecular rotation acts as the AIE mechanism in the KIz system. Conjugation of the triphenylphosphonium moiety to KIz allows successful development of triphenylphosphonium (TPP)-KIz for real-time bioimaging of innate mitochondria in live cells, thereby revealing the potential of KIz as a versatile molecular platform to generate fluorogenic probes based on AIE phenomena. We do believe the KIz system could serve as a new, reliable, and generally applicable molecular platform to develop various AIEgens having desired photophysical properties along with an excellent signal-to-noise ratio and with experimental convenience especially for fluorogenic live cell imaging.

Molecular Viscosity Sensors with Two Rotators for Optimizing the Fluorescence Intensity-Contrast Trade-Off.

A series of fluorescent molecular rotors obtained by introducing two rotational groups ("rotators"), which exhibit different rotational and electron-donating abilities, are discussed. Whereas the control molecular rotor, PH, includes a single rotator (the widely used phenyl group), the PO molecular rotors consist of two rotators (a phenyl group and an alkoxy group), which exhibit simultaneous strongly electron-donating and easy rotational abilities. Compared with the control rotor PH, PO molecular rotors exhibited one order of magnitude higher quantum yield (fluorescence intensity) and simultaneously exhibited significantly higher fluorescence contrast. These properties are directly related to the strong electron-donating ability and low energy barrier of rotation of the alkoxy group, as confirmed by dynamic fluorescence experiments and quantum chemical calculations. The PO molecular rotors exhibited two fluorescence relaxation pathways, whereas the PH molecular rotor exhibited a single fluorescence relaxation pathway. Cellular fluorescence imaging with PO molecular rotors for mapping cellular viscosity was successfully demonstrated.

Crystal Structure Analysis of the First Discovered Stability-Enhanced Solid State of Tenofovir Disoproxil Free Base Using Single Crystal X-ray Diffraction.

Tenofovir disoproxil (TD), an anti-virus drug, is currently marketed under its most stable form, Form-I of Tenofovir disoproxil fumarate (TDF). However, studies regarding the properties of TD free base crystal as a promising drug as well as its crystal structure have not yet been reported. This assumption was made because TD free base is not directly produced in a solid form during the manufacturing process. TD free base is first obtained in an oil form, and is then synthesized into TDF crystal. In this regard, the present study was conducted to investigate both the potentiality of TD free base to be an active pharmaceutical ingredient (API) and its crystal structure. Here, TD free base solid was produced by means of drowning-out crystallization. Next, single crystal X-ray diffraction (SXD) was employed to determine the crystal structure. Powder X-ray diffraction (PXRD) and a differential scanning calorimetry (DSC) analysis were performed to evaluate the crystal's properties. Furthermore, experiments were carried out at 15%, 35%, 55%, 75%, and 95% relative humidity (RH) for 12 h using a hygroscopic tester to determine and to compare the hygroscopicity and stability of TD free base with TDF crystal. Additionally, experiments were conducted under accelerated (40 °C, RH 75%) and stress storage (60 °C, RH 75%) conditions for 30 days to investigate the changes in purity and the formation of dimer. In this work, we report that TD free base possesses lower hygroscopicity, and thus does not generate dimer impurity from hydrolysis. Primarily, this is attributed to the fact that TD free base is not an easily ionized salt but comprises neutral hydrophobic molecules. According to the structural properties, the improved hygroscopic property of the TD free base crystal was due to the decrease of crystal polarity owing to the intermolecular H-bonds present in TD free base rings. In addition, the solubility investigation study carried out in aqueous solution and at gastrointestinal pH revealed a similarity in TDF and TD free base solubility under the mentioned conditions. Accordingly, we could confirm the potentiality of TD free base as an active pharmaceutical ingredient.

The mixed-metal tris-(di-sulfide) thio-phosphate, KNb1.77Ta0.23PS10.

The title compound catena-poly[potassium [tri-µ-disulfido-µ-tetra-thiophos-pha-to-di[niobate(IV)/tantalate(IV)(0.885/0.115)]]], has been obtained through the reaction of the elements with KCl. The title compound is isostructural with KNb2PS10, with the Nb sites occupied by statistically disordered Nb (88.5%) and Ta (11.5%) atoms. The structure is composed of anionic ∞ (1)[M 2PS10](-) chains along [100] (M = Nb/Ta) and K(+) ions. This chain is built up from distorted bicapped trigonal prisms [MS8] and [PS4] tetra-hedra. There are no inter-chain bonding inter-actions, except for electrostatic and van der Waals forces. The S2 (2-) and S(2-) anionic species and the M (4+)-M (4+) pair [M-M = 2.8939 (3) Å] are observed. The classical charge balance is represented by [K(+)][M (4+)]2[PS4 (3-)][S2 (2-)]3.

Reinvestigation of trilithium divanadium(III) tris-(orthophosphate), Li(3)V(2)(PO(4))(3), based on single-crystal X-ray data.

The structure of Li(3)V(2)(PO(4))(3) has been reinvestigated from single-crystal X-ray data. Although the results of the previous studies (all based on powder diffraction data) are comparable with our redetermination, all atoms were refined with anisotropic displacement parameters in the current study, and the resulting bond lengths are more accurate than those determined from powder diffraction data. The title compound adopts the Li(3)Fe(2)(PO(4))(3) structure type. The structure is composed of VO(6) octa-hedra and PO(4) tetra-hedra by sharing O atoms to form the three-dimensional anionic framework (∞) (3)[V(2)(PO(4))(3)](3-). The positions of the Li(+) ions in the empty channels can vary depending on the synthetic conditions. Bond-valence-sum calculations showed structures that are similar to the results of the present study seem to be more stable compared with others. The classical charge balance of the title compound can be represented as [Li(+)](3)[V(3+)](2)[P(5+)](3)[O(2-)](12).

The monoclinic form of trilithium dichromium(III) tris-(orthophosphate).

The monoclinic form of trilithium dichromium(III) tris-(ortho-phosphate), Li3Cr2(PO4)3, was prepared by the reactive halide flux method. The structure of the title compound is composed of a three-dimensional anionic framework with composition ∞ (3)[Cr2(PO4)3](3-) and Li(+) ions situated in the empty channels. The rigid framework built up from CrO6 octa-hedra and PO4 tetra-hedra is the same as that found in other monoclinic Li3 M 2(PO4)3 (M = Fe, Sc, V) phases. The three Li(+) cations of Li3Cr2(PO4)3 are unequally disordered over six crystallographically different sites. The classical charge balance of the title compound can be represented as [Li(+)]3[Cr(3+)]2[P(5+)]3[O(2-)]12. Solid-state UV/Vis spectra indicate that the crystal filed splitting (Δ0) of the Cr(3+) ion is around 2.22 eV.

Design of High-Performance Organic Nonlinear Optical and Terahertz Crystals by Controlling the van der Waals Volume.

In the development of new organic crystals for nonlinear optical and terahertz (THz) applications, it is very challenging to achieve the essentially required non-centrosymmetric molecular arrangement. Moreover, the resulting crystal structure is mostly unpredictable due to highly dipolar molecular components with complex functional substituents. In this work, new organic salt crystals with top-level macroscopic optical nonlinearity by controlling the van der Waals volume (VvdW ), rather than by trial and error, are logically designed. When the VvdW of molecular ionic components varies, the corresponding crystal symmetry shows an observable trend: change from centrosymmetric to non-centrosymmetric and back to centrosymmetric. All non-centrosymmetric crystals exhibit an isomorphic P1 crystal structure with an excellent macroscopic second-order nonlinear optical response. Apart from the top-level macroscopic optical nonlinearity, new organic crystals introducing highly electronegative fluorinated substituents with strong secondary bonding ability show excellent performance in efficient and broadband THz wave generation, high crystal density, high thermal stability, and good bulk crystal growth ability.

N-heterocyclic carbene catalyzed domino cyclization of propargylic alcohols and benzoyl isocyanates.

N-Hetereocyclic carbenes (NHCs) were found to be efficient catalysts for the cyclization of propargylic alcohols and isocyanates. Domino cyclization reactions were carried out using isopropyl-substituted imidazolium salt as a precatalyst, and a wide range of substituted oxazolidinones were obtained in high yields.

Ti insertion in the MTe(5) (M = Zr, Hf) structure type: Hf(0.78)Ti(0.22)Te(5).

The group 5 mixed-metal telluride, Hf(0.78)Ti(0.22)Te(5) (hafnium titanium penta-telluride), is isostructural with the binary phases HfTe(5) and ZrTe(5) and forms a layered structure extending parallel to (010). The layers are made up from chains of bicapped metal-centered trigonal prisms and zigzag Te chains. The metal site (site symmetry m2m) is occupied by statistically disordered Hf [78.1 (5)%] and Ti [21.9 (5)%]. In addition to the regular Te-Te pair [2.7448 (13) Å] forming the short base of the equilateral triangle of the trigonal prism, an inter-mediate Te⋯Te separation [2.9129 (9) Å] is also found. The classical charge balance of the compound can be described as [M(4+)][Te(2-)][Te(2) (2-)][Te(2) (0)] (M = Hf, Ti). The individual metal content can vary in different crystals, apparently forming a random substitutional solid solution (Hf(1-x)Ti(x))Te(5), with 0.15 ≤ x ≤ 0.22.

TiGeS(3).

The new ternary titanium(II) thio-germanate(IV), TiGeS(3), was synthesized using the reactive halide flux method. The title compound shows features of a ribbon-type structure formed from double chains composed of edge-sharing octa-hedral TiS(6) and pyramidal GeS(3) units, with all atoms in the asymmmetric unit positioned on mirror planes. While the TiS(6) octa-hedron is regular, the coordination around the Ge atom is rather irregular, which can be described as [3 + 3]. Three S atoms build up a triangle that is bound to the Ge atom, the coordination of which is augmented by three additional S atoms at considerably longer distances. The charge balance can formally be described as [Ti(4+)][Ge(2+)][S(2-)](3).

Copper-catalysed asymmetric reductive cross-coupling of prochiral alkenes.

Asymmetric construction of C(sp3)-C(sp3) bond with good stereocontrol of the two connecting carbon centres retaining all carbon or hydrogen substituents is a challenging target in transition metal catalysis. Transition metal-catalysed reductive coupling of unsaturated π-substrates is considered as a potent tool to expediently develop the molecular complexity with high atom efficiency. However, such an asymmetric and intermolecular process has yet to be developed fully. Herein, we report an efficient strategy to reductively couple two prochiral conjugate alkenes using a copper-catalysed tandem protocol in the presence of diboron. Notably, this transformation incorporates a wide range of terminal and internal enynes as coupling partners and facilitates highly diastereo- and enantioselective synthesis of organoboron derivatives with multiple adjacent stereocentres in a single operation.

Phonon-Suppressing Intermolecular Adhesives: Catechol-Based Broadband Organic THz Generators.

Solid-state molecular phonons play a crucial role in the performance of diverse photonic and optoelectronic devices. In this work, new organic terahertz (THz) generators based on a catechol group that acts as a phonon suppressing intermolecular adhesive are developed. The catechol group is widely used in mussel-inspired mechanical adhesive chemistry. Newly designed organic electro-optic crystals consist of catechol-based nonlinear optical 4-(3,4-dihydroxystyryl)-1-methylpyridinium (DHP) cations and 4-(trifluoromethyl)benzenesulfonate anions (TFS), which both have multiple interionic interaction capability. Interestingly, compared to benchmark organic crystals for THz generators, DHP-TFS crystals concomitantly achieve top level values of the lowest void volume and the highest crystal density, resulting in an exceptionally small amplitude of solid-state molecular phonons. Simultaneously achieving small molecular phonon amplitude, large optical nonlinearity and good phase matching at infrared optical pump wavelengths, DHP-TFS crystals are capable of generating broadband THz waves of up to 16 THz with high optical-to-THz conversion efficiency; one order of magnitude higher than commercial inorganic THz generators.

KNb(1.75)V(0.25)PS(10).

The title compound, potassium diniobium vanadium phospho-rus deca-sulfide, KNb(1.75)V(0.25)PS(10), was obtained by reaction of the elements with a eutectic mixture of KCl/LiCl. It is isostructural with the quaternary KNb(2)PS(10), but the Nb sites are occupied by statistically disordered Nb (87.5%) and V (12.5%) atoms. The structure is composed of anionic (∞) (1)[M(2)PS(10)](-) chains (M = Nb/V) separated from each other by K(+) ions. The chain is composed of [MS(8)] distorted bicapped trigonal prisms and [PS(4)] tetra-hedra. There are no inter-chain bonding inter-actions. The crystal used for the X-ray analysis was a racemic twin.

A new mixed group 5 metal selenide, Nb(1.41)V(0.59)Se(9).

The new mixed-metallic phase, niobium vanadium nona-selenide, (Nb(2-x)V(x))Se(9) (0.18≤ x ≤ 0.59) is isostructural with monoclinic V(2)Se(9). The structure is composed of chains of bicapped trigonal-prismatic [MSe(8)] units. The metal (M) site is occupied by statistically disordered Nb [0.706 (5)] and V [0.294 (5)] atoms. Two trigonal prisms are linked by sharing a recta-ngular face composed of two Se(2) (2-) pairs. Through three edging and capping Se atoms, the chains are extended along [101]. The chain shows alternating short [2.8847 (7) Å] and long [3.7159 (7) Å] M-M distances. The structure shows a wide range of Se-Se inter-actions. In addition to the Se(2) (2-) pairs of the recta-ngular face, an inter-mediate Se⋯Se separation [2.6584 (5) Å] is found. The amount of each metal can vary, [(Nb(2-x)V(x))Se(9), 0.18 ≤ x ≤m 0.59] and they seem to form a random substitutional solid solution. The M-M distances increase gradually by increasing the amount of Nb atoms. The classical charge-balance of the compound can be described as [M(4+)](2)[Se(2) (2-)](2)[Se(5) (4-)].

Reinvestigation of the low-temperature form of Ag(2)Se (naumannite) based on single-crystal data.

The crystal structure of the low-temperature form of synthetic naumannite [disilver(I) selenide], Ag(2)Se, has been reinvestigated based on single-crystal data. In comparison with previous powder diffraction studies, anisotropic displacement parameters are additionally reported. The structure is composed of Se layers and two crystallographically independent Ag atoms. One Ag atom lies close to the Se layer and is surrounded by four Se atoms in a distorted tetra-hedral coordination, while the second Ag atom lies between the Se layers and exhibits a [3 + 1] coordination defined by three close Se atoms, forming a trigonal plane, and one remote Se atom.

The mixed-valent titanium phosphate, Li(2)Ti(2)(PO(4))(3), dilithium dititanium(III/IV) tris-(orthophosphate).

The mixed-valent titanium phosphate, Li(2)Ti(2)(PO(4))(3), has been prepared by the reactive halide flux method. The title compound is isostructural with Li(2)TiM(PO(4))(3) (M = Fe, Cr) and Li(2)FeZr(PO(4))(3) and has the same (3) (∞)[Ti(2)(PO(4))(3)](2-) framework as the previously reported Li(3-) (x)M(2)(PO(4))(3) phases. The framework is built up from corner-sharing TiO(6) octa-hedra and PO(4) tetra-hedra, one of which has 2 symmetry. The Li(+) ions are located on one crystallographic position and reside in the vacancies of the framework. They are surrounded by four O atoms in a distorted tetra-hedral coordination. The classical charge-balance of the title compound can be represented as Li(+) (2)(Ti(3+)/Ti(4+))(PO(4) (3-))(3).

A vanadium tellurate, (NH(4))(2)[VO(2)](2)[TeO(4)(OH)(2)], containing two edge-shared square-pyramidal VO(5) groups.

A new ammonium vanadium tellurate, (NH(4))(2)[VO(2)](2)[TeO(4)(OH)(2)] (1), was hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, and TG analysis. Compound 1 crystallizes in the monoclinic system, space group P2(1)/n: a = 8.9112(18) A, b = 15.151(3) A, c = 15.187(3) A, beta = 97.91(3)(o), V = 2030.9(7) A(3), Z = 8, R1 (I > 2sigma(I)) = 0.0295, wR2 (all data) = 0.0631. The structure of 1 consists of infinite anionic chains, {[VO(2)](2)[TeO(4)(OH)(2)]}(2-), of edge-sharing VO(5) square pyramids and TeO(4)(OH)(2) octahedra. Two VO(5) square pyramids are joined together by sharing their edge to form a V(2)O(8) binuclear unit. The V(2)O(8) and TeO(4)(OH)(2) units are alternatively connected to each other by sharing their edges to complete infinite zigzag anionic {[VO(2)](2)[TeO(4)(OH)(2)]}(2-) chains. The structure contains an extended network of O-H...O hydrogen bonds between the chains. The network of intermolecular hydrogen bonding results in layers parallel to the ab plane. Ammonium cations are hydrogen-bonded either to the oxygen atoms of the anionic chains or to each other in a complex arrangement.

The quinter-nary thio-phosphate Cs(0.5)Ag(0.5)Nb(2)PS(10).

The quinter-nary thio-phosphate Cs(0.5)Ag(0.5)Nb(2)PS(10), cesium silver tris-(disulfido)[tetra-thio-phosphato(V)]diniobate(IV), has been prepared from the elements using a CsCl flux. The crystal structure is made up of (∞) (1)[Nb(2)PS(10)] chains expanding along [010]. These chains are built up from bicapped trigonal-prismatic [Nb(2)S(12)] units and tetra-hedral [PS(4)] groups and are linked through a linear S-Ag-S bridge, forming a two-dimensional layer. These layers then stack on top of each other, completing the three-dimensional structure with an undulating van der Waals gap. The disordered Cs(+) ions reside on sites with half-occupation in the voids of this arrangement. Short [2.8843 (5) Å] and long [3.7316 (4) Å] Nb-Nb distances alternate along the chains, and anionic S(2) (2-) and S(2-) species are observed. The charge balance of the com-pound can be represented by the formula [Cs(+)](0.5)[Ag(+)](0.5)[Nb(4+)](2)[PS(4) (3-)][S(2) (2-)](3).

The two-dimensional thio-phosphate CsCrP(2)S(7).

The quaternary title compound, caesium chromium(III) hepta-thio-diphosphate(V), CsCrP(2)S(7), has been synthesized using the reactive halide flux method. It is isotypic with other AMP(2)S(7) (A = alkali metal; M = Cr, V or In) structures and consists of two-dimensional (∞) (2)[CrP(2)S(7)](-) layers extending parallel to (001) which are separated from each other by Cs(+) ions (symmetry 2). The layer is built up from slightly distorted octa-hedral [CrS(6)] units (symmetry 2) and bent [P(2)S(7)] units consisting of two corner-sharing [PS(4)] tetra-hedra. The [CrS(6)] octa-hedra share two edges and two corners with the [PS(4)] tetra-hedra. There are only van der Waals inter-actions present between the layers. The Cs(+) ions are located in this van der Waals gap and stabilize the structure through weak ionic inter-actions. The classical charge balance of the title compound can be expressed as [Cs(+)][Cr(3+)][P(5+)](2)[S(2-)](7.).

Cs(0.49)NbPS(6).

The quaternary thio-phosphate, Cs(0.49)NbPS(6), caesium hexa-thio-niobiophosphate(V), has been synthesized by the reactive halide flux method. The title compound is isotypic with Rb(0.46)TaPS(6) and is made up of a bicapped trigonal-biprismatic [Nb(2)S(12)] unit and a tetra-hedral [PS(4)] group. The [Nb(2)S(12)] units linked by the [PS(4)] tetra-hedra form infinite chains, yielding a three-dimensional network with rather large van der Waals gaps along the c axis in which the disordered Cs(+) ions reside. The electrons released by the Cs atoms are transferred to the pairwise niobium metal site and there are substantial inter-metallic Nb-Nb bonding inter-actions. This leads to a significant decrease of the inter-metallic distance in the title compound compared to that in TaPS(6). The classical charge balance of the title compound may be represented as [Cs(+)](0.49)[Nb(4.51+)][P(5+)][S(2-)](4)[S(2) (2-)].