FlɛX: a computer vision program to evaluate strain in flexible crystals.

The program FlɛX (flexural ɛ for xtals) has been developed for a quick, easy and accurate evaluation of the maximum deformation reached in flexible crystals from a simple optical microscope picture. The program takes advantage of computer vision libraries to find the contours of a bent crystal and fit these to semicircles. It can then calculate the theoretical maximum deformation along its long axis using equations from the Euler-Bernoulli beam theory.

Synchronization of Nanoparticle Sensitization and Radiosensitizing Chemotherapy through Cell Cycle Arrest Achieving Ultralow X-ray Dose Delivery to Pancreatic Tumors.

Pancreatic cancer is among the leading causes of cancer-related death and remains a formidable therapeutic challenge. To date, surgical resection and chemotherapy have been the standards of care. Methotrexate (MTX), which is recognized as a refractory drug for pancreatic cells, was conjugated to the surface of LiYF4:Ce3+ nanoparticles (NP-MTX) through a photocleavable linker molecule. When LiYF4:Ce3+ NPs are stimulated by X-rays, they emit light, which induces the photocleavage of the photolabile linker molecule to release MTX. MTX can target pancreatic tumors, which overexpress folic acid (FA) receptors and are internalized into the cell through receptor-mediated endocytosis. The synergistic effect of the NP-MTX treatment initiated by X-ray irradiation occurs due to the combination of nanoparticle sensitization and the radiosensitizing chemotherapy of the photocleaved MTX molecule. This dual sensitization effect mediated by NP-MTX enabled 40% dose enhancement, which corresponded with an increase in the generation of cytotoxic cellular reactive oxygen species (ROS) and enhanced S phase arrest within the cell cycle. The delivery of an ultralow radiation dose of 0.1 Gy resulted in the photocleavage of MTX from NP-MTX, and this strategy demonstrated in vivo efficacy against AsPC-1 and PANC-1 xenografted pancreatic tumors.

Low Dose of X-Ray-Excited Long-Lasting Luminescent Concave Nanocubes in Highly Passive Targeting Deep-Seated Hepatic Tumors.

Chromium-doped zinc gallate, ZnGa2 O4 :Cr3+ (ZGC), is viewed as a long-lasting luminescence (LLL) phosphor that can avoid tissue autofluorescence interference for in vivo imaging detection. ZGC is a cubic spinel structure, a typical agglomerative or clustered morphology lacking a defined cubic shape, but a sphere-like feature is commonly obtained for the nanometric ZGC. The substantial challenge remains achieving a well-defined cubic feature in nanoscale. The process by which dispersed and well-defined concave cubic ZGC is obtained is described, exhibiting much stronger LLL in UV and X-ray excitation for the dispersed cubic ZGC compared with the agglomerative form that cannot be excited using X-rays with a low dose of 0.5 Gy. The cubic ZGC reveals a specific accumulation in liver and 0.5 Gy used at the end of X-ray excitation is sufficient for imaging of deep-seated hepatic tumors. The ZGC nanocubes show highly passive targeting of orthotopic hepatic tumors.

Efficient Solar-Driven Hydrogen Transfer by Bismuth-Based Photocatalyst with Engineered Basic Sites.

Photocatalytic organic conversions involving a hydrogen transfer (HT) step have attracted much attention, but the efficiency and selectivity under visible light irradiation still needs to be significantly enhanced. Here we have developed a noble metal-free, basic-site engineered bismuth oxybromide [Bi24O31Br10(OH)δ] that can accelerate the photocatalytic HT step in both reduction and oxidation reactions, i.e., nitrobenzene to azo/azoxybenzene, quinones to quinols, thiones to thiols, and alcohols to ketones under visible light irradiation and ambient conditions. Remarkably, quantum efficiencies of 42% and 32% for the nitrobenzene reduction can be reached under 410 and 450 nm irradiation, respectively. The Bi24O31Br10(OH)δ photocatalyst also exhibits excellent performance in up-scaling and stability under visible light and even solar irradiation, revealing economic potential for industrial applications.

Effect of the Functional Groups of Racemic Rodlike Schiff Base Mesogens on the Stabilization of Blue Phase in Binary Mixture Systems.

Four series of rodlike racemic Schiff base mesogens possessing different alkyl chains and two types of linkages, ester and alkynyl linkages, were synthesized and applied to induce cubic blue phases (BPs) in simple binary mixture systems. The mesophases of these Schiff base mesogens were confirmed by variable-temperature X-ray diffraction and the characteristic texture from polarized optical microscopy (POM). In general, when chiral additive S-(+)-2-octyl 4-(4-hexyloxybenzoyloxy)benzoate (S811; 20-40 wt %) is added into the rodlike racemic salicylaldimine-based mesogens, the cubic BPs could be observed and its temperature range is larger than 20 K. The widest temperature range of the cubic BP (35 K) can be observed in the blending mixture composed of rodlike racemic salicylaldimine-based mesogen OH-TIn possessing alkynyl linkage and 35-40 wt % S811. However, Schiff base mesogens possessing alkynyl linkage show a direct isotropic to chiral nematic transition when equal amount of chiral dopant is added. Notably, the termination temperature of BPs is very close to room temperature (ca. 35 °C) after 40.0 wt % S811 is added into the salicylaldimine-based mesogens possessing terminal alkyl chains and ester linkage. Interestingly, wide BPs (>30 K) can also be induced by adding chiral additive 1,4:3,6-dianhydro-2,5-bis[4-(n-hexyl-1-oxy)benzoic acid]sorbitol (ISO(6OBA)2) with a high helical twisting power into the racemic Schiff base mesogen possessing ester linkage. Cubic BPI and BPII can be confirmed by reflectance spectra and POM. The results of reflectance spectra indicate that the binary mixture composed of salicylaldimine-based mesogens and S811 easily exhibits a supercooling effect and induces BPI. However, only BPII can be observed in all binary mixtures containing Schiff base mesogens. On the basis of our experimental results and molecular modeling, we suppose that the values of biaxiality, polarizability, and the dipole moment of molecular geometry are the main factors that affect BP stabilization.

Triboluminescence and Metal Phosphor for Organic Light-Emitting Diodes: Functional Pt(II) Complexes with Both 2-Pyridylimidazol-2-ylidene and Bipyrazolate Chelates.

We report the utilization of both pyrid-2-yl-imidazolylidene and dianionic bipz chelates as constituents in syntheses of a new series of charge-neutral Pt(II) complexes 1-4, among which complex 4 revealed remarkable triboluminescence, i.e., generation of photoemission upon grinding or cracking of the solid sample. The triboluminescence is found to be sensitive to the subtle changes of the associated substituents of pyrid-2-yl-imidazolylidene chelate, as verified by the disappearance of the triboluminescence for complexes 1-3. Alternatively, the well-ordered solid packing of 3, as indicated by the grazing incidence X-ray scattering experiment, serves as an ideal emitter for the fabrication of highly efficient OLEDs, rendering high external quantum efficienciy (25.9%) and luminesce efficiency (90 cd A-1) at the practical brightness of 100 cd m-2. The rather low roll-off in efficiency (24.4%, 85 cd A-1 at high brightness of 1000 cd m-2) is attributed to the short excited-state lifetime of 3 (∼800 ns) in the solid state, which in turn is associated with the MMLCT transition character.

A heteropentanuclear metal string complex [Mo2NiMo2(tpda)4(NCS)2] with two linearly aligned quadruply bonded Mo2 units connected by a Ni ion and a meso configuration of the complex.

A dimeric molybdenum precursor and nickel ions are used to synthesize a symmetric heteropentanuclear complex, [Mo2NiMo2(tpda)4(NCS)2]. This complex possesses unique structural features, as the four ligands are coordinated to the metal framework in a meso configuration. Furthermore, the central Ni2+ ion is in a high spin state.

X-Ray Diffraction and Mössbauer Spectroscopy Studies of Pressure-Induced Phase Transitions in a Mixed-Valence Trinuclear Iron Complex.

The mixed-valence complex Fe3 O(cyanoacetate)6 (H2 O)3 (1) has been studied by single-crystal X-ray diffraction analysis at pressures up to 5.3(1) GPa and by (synchrotron) Mössbauer spectroscopy at pressures up to 8(1) GPa. Crystal structure refinements were possible up to 4.0(1) GPa. In this pressure range, 1 undergoes two pressure-induced phase transitions. The first phase transition at around 3 GPa is isosymmetric and involves a 60° rotation of 50 % of the cyanoacetate ligands. The second phase transition at around 4 GPa reduces the symmetry from rhombohedral to triclinic. Mössbauer spectra show that the complex becomes partially valence-trapped after the second phase transition. This sluggish pressure-induced valence-trapping is in contrast to the very abrupt valence-trapping observed when compound 1 is cooled from 130 to 120 K at ambient pressure.

Broad temperature range of cubic blue phase present in simple binary mixture systems containing rodlike Schiff base mesogens with tolane moiety.

Four simple rodlike Schiff base mesogens with tolane moiety were synthesized and applied to stabilize cubic blue phases (BPs) in simple binary mixture systems for the first time. When the chiral additive or was added into a chiral salicylaldimine-based compound, the temperature range of the cubic BP could be extended by more than 20 °C. However, when the chiral Schiff base mesogen was blended with chiral dopant possessing opposite handedness, , BPs could not be observed. Interestingly, the widest temperature range of the cubic BPs (∼35 °C) could be induced by adding the rodlike chiral dopant or into the rodlike racemic Schiff base mesogen with hydroxyl group. On the basis of our experimental results and molecular modeling, the appearance and temperature range of the BPs are affected by the dipole moment and the biaxiality of the molecular geometry. Accordingly, we demonstrated that the hydroxyl group and the methyl branch in this type of Schiff base mesogen play an important role in the stabilization of BPs.

High pressure induced charge transfer in 3d-4f bimetallic photomagnetic materials.

Pressure-induced crystal color change of photo-magnetic materials [Ln(DMF)4(H2O)3(µ-CN)M(CN)5]·H2O, Ln = Y, M = Fe (1), Ln = Y, M = Co (2), Ln = Nd, M = Fe (3) (DMF = N,N-dimethyl formamide) are investigated using variable pressure X-ray Absorption Near-Edge Structure (XANES) spectroscopy and X-ray diffraction. For 1 the effect is caused by ligand-to-metal charge transfer (LMCT) on the iron site.

Chemical bonding in a linear chromium metal string complex.

A combined experimental and theoretical electron density study of the shortest trichromium metal wire, Cr3(dpa)4Cl2·(C2H5OC2H5)(x)(CH2Cl2)(1-x) (1, dpa = bis(2-pyridyl)amido), is reported. High resolution X-ray diffraction data has been collected both at 100 K using a conventional X-ray source (DS1) and at 15 K using a synchrotron X-ray source (DS2). The linear chromium string is terminated by Cl(-) ions at both ends, and each Cr atom is also coordinated by four N atoms from bridging dpa ligands. The two Cr-Cr bond distances are unequal at 100 K (with d(Cr1-Cr2) being 0.029 Å shorter than d(Cr2-Cr3)) but at 15 K they are almost equal (0.002 Å difference). Analysis of the slightly elongated thermal ellipsoids of the Cr2 atom suggests that it is not due to disorder, but the presence of a shallow potential energy surface. Laplacian maps clearly show local valence shell charge concentration (VSCC) in the electron density along the bisector of the equatorial Cr-N bonds. Integration over the atomic basins indicates that Cr2 has smaller atomic charge and volume than Cr1 and Cr3. The topological characterization of the Cr-Cr bonds indicates partly covalent characters with electron density at the bond critical point of ∼0.3 e Å(-3) and negative total energy density. The delocalization index of Cr-Cr is 0.8 for Cr1-Cr2 and 0.08 for Cr1-Cr3. Second-order perturbation analysis shows high stabilization energy of the Cr-Cr bonds (E(2) ∼ 190 kcal mol(-1)). Delocalization indices and source function and natural bond orbital analyses are all indicative of localized Cr-Cr bonding interactions.

Chemical bond characterization of a mixed-valence tri-cobalt complex, Co3(µ-admtrz)4(µ-OH)2(CN)6·2H2O.

Charge density study of a mixed-valence tri-cobalt compound, Co3(µ-admtrz)4(µ-OH)2(CN)6·2H2O (1) (admtrz = 3,5-dimethyl-4-amino-1,2,4-triazole), is investigated based on high resolution X-ray diffraction data and density functional theory (DFT) calculations. The molecular structure of this compound contains three cobalt atoms in a linear fashion, where two terminal ones are Co(III) at a low-spin (LS) state and a central one is Co(II) at a high-spin (HS) state with a total spin quantum number, S(total), of 3/2. It is centrosymmetric with the center of inversion located at the central Co atom (Co2). The Co2 ion is linked with each terminal cobalt (Co1) ion through two µ-admtrz ligands and a µ-OH ligand in a CoN4O2 coordination, where the Co1 is bonded additionally to three CN ligands with CoN2OC3 coordination. The combined experimental and theoretical charge density study identifies the different characters of two types of cobalt ions; more pronounced charge concentration and depletion features in the valence shell charge concentration (VSCC) are found in the Co(III) ion than in the Co(II) ion, and d-orbital populations also show the difference. According to topological properties associated with the bond critical point (BCP), the Co1-C(N) bond is the strongest among all the Co-ligand bonds in this compound; the Co-O is stronger than Co-N bond. Again Co1-O is stronger than Co2-O, so as the Co1-N being stronger than Co2-N bond. The electronic configuration of each type of Co atom is further characterized through magnetic measurement, Co-specific X-ray absorption near edge spectroscopy (XANES), and X-ray emission spectra (XES).

A "pillar-free", highly porous metalloporphyrinic framework exhibiting eclipsed porphyrin arrays.

A "pillar-free", highly porous metalloporphyrinic framework (UNLPF-1) exhibiting eclipsed porphyrin arrays has been constructed from an octacarboxylate ligand connected with paddlewheel secondary building units. UNLPF-1 possesses two types of open metal sites and exhibits an efficient selectivity toward capture of CO2 over N2.

Bond characterization on a Cr-Cr quintuple bond: a combined experimental and theoretical study.

A combined experimental and theoretical charge density study on a quintuply bonded dichromium complex, Cr(2)(dipp)(2) (dipp = (Ar)NC(H)N(Ar) and Ar = 2,6-i-Pr(2)-C(6)H(3)), is performed. Two dipp ligands are bridged between two Cr ions; each Cr atom is coordinated to two N atoms of the ligands in a linear fashion. The Cr atom is in a low oxidation state, Cr(I), and in low coordination number condition, which stabilizes a metal-metal multiple bond, in this case, a quintuple bond. Indeed, it gives an ultrashort Cr-Cr bond distance of 1.7492(1) Å in the complex. The bond characterization of such a quintuple bond is undertaken both experimentally by high-resolution single-crystal X-ray diffraction and theoretically by density functional calculation (DFT). Electron densities are depicted via deformation density and Laplacian distributions. Bond characterizations of the complex are presented in terms of topological properties, Fermi hole function, source function (SF), and natural bonding orbital (NBO) analysis. The electron density at the Cr-Cr bond critical point (BCP) is 1.70 e/Å(3), quite a high value for metal-metal bonding and mainly contributed from the metal ion itself. The quintuple bond is confirmed with one σ, two π, and two δ interactions by NBO analysis and Fermi hole function. The molecular orbitals (MOs) illustrate that five bonding orbitals are predominantly contributed from the 3d orbitals of the Cr(I) ion. The effective bond order from NBO analysis is 4.60. The detail comparison between experiment and theory will be given. Additionally, three closely related complexes are calculated for systematic comparison.

Diaza-18-crown-6 appended dual 7-hydroxyquinolines; mercury ion recognition in aqueous solution.

8,8'-(1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane-7,16-diyl)bis(methylene)diquinolin-7-ol (TDBQ) was synthesized and proved to recognize Hg2+ via reducing Hg2+ to Hg+, forming a unique Hg(2)2+ - complex.

Topological analyses and bond characterization of 1,3,5,7-tetra-tert-butyl-s-indacene: a weak Csp3-H...H-Csp2-type dihydrogen interaction.

Topological analyses of experimental and theoretical calculated electron densities of 1,3,5,7-tetra-tert-butyl-s-indacene provide bond characterizations of the chemical bond and of the pi-delocalization. A weak C(sp(3))-H...H-C(sp(2))-type intramolecular dihydrogen interaction (DHI) is identified through this analysis.