Photochromic Coordination Compound: Oxygen-Assisted Photoinduced Color Change for Triplet Oxygen Detection.

Detection of oxygen though color change is highly desirable for rapid qualitative analysis like the case of pH test papers. This work demonstrates 3O2-assisted photoinduced color change of a new photochromic coordination compound [Zn(4-aminopyridine)2Cl2] (ZnaPyCl), which represents the first photochromic compound with a selective 3O2 detection ability. The compound underwent photoinduced intraligand charge separation and formed a stable diradical-like triplet species in the solid state or in frozen solution, accompanied by conversion of triplet oxygen to singlet oxygen.

A novel Pd3O9@α-Al2O3 catalyst under a hydroxylated effect: high activity in the CO oxidation reaction.

Considering the importance of palladium-based and doped metal-oxide catalysts in CO oxidation, we design a new Pd3O9@α-Al2O3 catalyst and simulate its efficiency under a hydroxylated effect. The structure, electronic structure and oxidation activity of the hydroxylated Pd3O9@α-Al2O3(0001) surface are investigated by density functional theory. Under the O-rich growth conditions, Pd preferentially replaces Al. The lowest formation energy of the Pd-doped α-Al2O3(0001) surface is 0.21 eV under conditions wherein the coverage of the Pd-doped α-Al2O3 is 0.75 on a pre-hydroxylated surface and the water coverage is 0.25, which leads to formation of a Pd3O9 cluster embedded in the Al2O3(0001) surface. The reaction mechanisms of CO oxidization have been elucidated first by CO adsorption and migration, second by O(v) formation with the first CO2 release, then by the first foreign O2 filling and CO co-adsorption, and finally by the second CO2 desorption and restoration of the hydroxylated Pd3O9@α-Al2O3(0001) surface. The rate-determining step is the formation of the first CO2 in the whole catalytic cycle. The results also indicate that the energy barrier for CO oxidization is obviously reduced compared to that of the undoped surface, which implies that the introduction of Pd can efficiently improve the oxidation reactivity of the α-Al2O3(0001) surface. Compared to the synthesized Ir1/FeO(x) (1.41 eV) and Pt1/FeO(x) (0.79 eV) catalysts, the reaction activation barrier of CO oxidation is lowered by 0.65 eV and 0.03 eV, respectively. Therefore, the Pd3O9@α-Al2O3 catalyst shows superior catalytic activity in CO oxidation. The present results enrich the understanding of the catalytic oxidation of CO by palladium-based catalysts and provide a clue for fabricating palladium-based catalysts with low cost and high activity.

Evaluation of interactions between urokinase plasminogen and inhibitors using molecular dynamic simulation and free-energy calculation.

The binding modes of urokinase-type plasminogen activator (uPA) with five inhibitors (1-(7-sulfonamidoisoquinolinyl) guanidine derivatives) were predicted based on molecular dynamic simulations. MM/PBSA free-energy calculations and MM/GBSA free-energy decomposition analyses were performed on the studied complexes. The calculated binding free energies are reasonably consistent with the experimental results. The free-energy decomposition analyses elucidate the different contributions of the energy of some favorable residues in the interactions between protein and ligand of each complex. The results indicate that the inhibitors mainly interact with the S1 pocket of uPA, wherein the hydrogen bonds and the interactions between guanidines and the corresponding residues play an important role. Moreover, hydrogen bond analyses show the water-mediated hydrogen-bond network near the S1 pocket between uPA, and the ligand probably leads to excellent selectivity of these inhibitors on uPA.

Enzymatically hydrolyzed sodium caseinate nanoparticles efficiently enhancing the solubility, stability, and antioxidant and anti-biofilm activities of hydrophobic Tanshinone IIA.

Enzymatic hydrolysis has been validated as an appropriate strategy for improving the properties of natural protein. Here, we used enzymatic hydrolysis sodium caseinate (Eh NaCas) as a nano-carrier for enhancing the solubility, stability, and antioxidant and anti-biofilm activities of hydrophobic encapsulants. Tanshinone IIA (TA) was loaded into the hydrophobic regions of Eh NaCas by self-assembly, and the encapsulation efficiency could reach 96.54 ± 0.14% under an optimized host-guest ratio. After Eh NaCas packed, the TA-loaded Eh NaCas nanoparticles (Eh NaCas@TA) showed regular spheres, uniform particle size distribution and more optimal drug release. Moreover, the solubility of TA in aqueous solution increased over 2.4 × 105 times, and the TA guest molecules displayed excellent stability under light and other harsh environments. Interestingly, the vehicle protein and TA exhibited synergistic antioxidant effects. Furthermore, Eh NaCas@TA forcefully restrained the growth and destroyed the biofilm construction of Streptococcus mutans compared to free TA, showing positive antibacterial activity. The establishment of these results demonstrated the feasibility and functionality of edible protein hydrolysates as nano-carriers for loading natural plant hydrophobic extracts.

Direct metal-metal interaction contributions to quadratic hyperpolarizability: a study on dirhenium complexes.

We present a comparative study of the metal-metal interaction effect on the static quadratic hyperpolarizabilities of two typical dinuclear rhenium clusters. The electronic structures, excitation spectra, dipolar moments, static polarizabilities, and quadratic hyperpolarizabilities of the two complexes with direct metal-metal interactions have been computed and analyzed with the use of high-level DFT/TDDFT methods. The geometries and the first intense excitations agree with the relevant reported measurements. The orbital decomposition scheme ( J. Phys. Chem. A 2006, 110, 1014-1021) has been applied to analyze the relationship between the electronic structures and nonlinear optical (NLO) properties of these two complexes. We propose an unprecedented NLO response mechanism featuring the contribution of the direct metal-metal interaction transition process in these dinuclear rhenium complexes. This contribution positively enhances the quadratic hyperpolarizability and relates to the intensity of the metal-metal interactions of the complexes. The results are helpful to the development of NLO chromophores in polynuclear metal clusters through the molecular design technique.

ß-Lactoglobulin as a Nanotransporter for Glabridin: Exploring the Binding Properties and Bioactivity Influences.

Based on the fact that ß-lactoglobulin (ß-lg) can solubilize readily in water and bind many small hydrophobic molecules, a novel nanocomplexed glabridin with ß-lg was developed by an antisolvent precipitation method. After binding to ß-lg, the solubility of glabridin in aqueous solution was enhanced 21 times. Fluorescence spectroscopy of ß-lg revealed that the interaction of glabridin with ß-lg made the environment of Trp and Tyr residues on ß-lg more hydrophilic. The morphology and crystal form of the nanocomplexed glabridin with ß-lg was characterized and the changes in ß-lg conformation was also been investigated. In combination with molecular docking modeling, the results revealed that glabridin was bound to ß-lg by hydrophobic forces and hydrogen-bond interactions. Furthermore, the nanocomplexed glabridin with ß-lg had a better 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity and 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid radical-scavenging capacity compared to free glabridin at the same concentration during in vitro tests. Thus, nanocomplexing with ß-lg, by virtue of its ability to enhance the solubility of glabridin in aqueous systems, provides a suitable opportunity as a nanocarrier molecule.

Intensifying sulforaphane formation in broccoli sprouts by using other cruciferous sprouts additions.

Sulforaphane is a significant chemopreventive compound which is the predominant glucosinolate in broccoli sprouts. However, the existence of the epithiospecifier protein could direct the hydrolysis of glucosinolates toward sulforaphane nitrile formation instead of sulforaphane. Therefore, the study aimed on improving the yielding of sulforaphane in broccoli sprouts with a new method of the united hydrolysis of cruciferous sprouts. According to the results, the addition of radish, rocket and rape sprouts to broccoli sprouts could promote the hydrolysis of the glucoraphanin to anticancer effective sulforaphane to 2.03, 2.32 and 1.95-fold, respectively, compared to single broccoli sprouts. Meanwhile, the formation of non-bioactive sulforaphane nitrile in these three groups decreased greatly. However, the addition of mustard sprouts had no positive effect. These observations could make a contribution to the potential chemoprotective effects of broccoli sprouts.

Energy-dependent photochromism at room temperature for visually detecting and distinguishing X-rays.

A radiochromic material with energy-dependent X-ray-induced photochromism was obtained by incorporating a radiosensitive glycolate ligand into an electron-transfer photochromic metalloviologen system. It is highly promising for detecting soft X-rays with energies less than 2 keV and may find application in qualitatively and visually distinguishing the energy range of X-rays.

Significant enhancement of conductance of a hybrid layered molybdate semiconductor by light or heat.

Introduction of the viologen cation, a well-known electron acceptor, into molybdate layers led to a dramatic change in the conductance of the 2D hybrid material in the process of photo-induced or thermo-induced coloration, which provides an alternative approach to manipulate the electronic properties of 2D semiconductors via external optical/thermal stimuli.

Characterization of glabridin/hydroxypropyl-ß-cyclodextrin inclusion complex with robust solubility and enhanced bioactivity.

Various biological activities of glabridin have been reported in literature, however, the bioavailability and clinical application was limited by its low water solubility. In this study, we developed a novel inclusion complex of glabridin and hydroxypropyl-ß-cyclodextrin (HP-ß-CD) that features improved solubility and bioactivity. The formation of the inclusion complex was supported by data from FT-IR, PXRD, SEM and NMR. Specifically, the NMR results indicated that the aromatic ring of glabridin was merged into and located at the narrow side the cavity of HP-ß-CD. The in vitro tests showed that the formation of the inclusion complex led to 9 times increase in the DPPH radical-scavenging capacity and 20 times increase in the tyrosinase inhibitory activity compared to the free glabridin at the same concentration. Therefore, the glabridin/HP-ß-CD inclusion complex adds a promising strategy for the clinical application of glabridin in the future.

Goblet-shaped pentanuclear lanthanide clusters assembled with a cyclen derivative ligand exhibiting slow magnetic relaxation.

Two coordination compounds with the formula Ln5(H2O)(OH)4(NO3)3(BZA)4L (Ln = Tb(3+) (1), Dy(3+) (2)) have been assembled in a one-pot synthesis from the tetrasubstituted cyclen derivative ligand N,N',N'',N'''-tetra(2-hydroxy-3-methoxy-5-methylbenzyl)-1,4,7,10-tetraazacyclododecane (H4L), Ln(NO3)3·xH2O (Ln = Tb(3+) (x = 6), Dy(3+) (x = 5)) and the auxiliary ligand benzoic acid (HBZA). Single-crystal X-ray diffraction studies reveal that both compounds feature a novel homometallic appended cubane geometry. The magnetic study on 1 suggests the presence of anti-ferromagnetic interactions, whereas 2 exhibits weak ferromagnetic coupling. Under an applied dc field, 1 shows no out-of-phase alternating current (ac) signal whereas 2 shows slow-relaxation processes that correspond to an energy gap (Ea/kB) of 4.11 K and a pre-exponential factor (τ0) of 3.45 × 10(-5) s.

A highly stable and white-light-emitting Eu(iii) MOF.

A long π-conjugated organic ligand 2-(2,4-disulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline (H3sfpip) featuring blue-green emission was used to construct Eu(iii) MOFs to obtain a target white-light-emitting LnMOF with no dopant atom in its structure. Two complexes, [Eu(H2O)2(OH)(Hsfpip)]·H2O (1) and [Eu(H2O)(oa)0.5(Hsfpip)]·2H2O (2), were successfully synthesized under similar hydrothermal reaction conditions. The absence or presence of an ancillary ligand such as oxalic acid (oa) showed direct influence on the coordination mode of the Hsfpip linker and in the final topology of the polymeric structure. Complex 1 displays an unstable 2D polymeric structure and weak red luminescence from Eu3+ due to the quenching effect of high-energy O-H oscillators around the inner coordination sphere of the metal center, whereas the introduction of an ancillary ligand such as oxalic acid results in a tight-bonding 3D polymeric structure and an intense white light emission from complex 2. Moreover, due to the skeleton rigidity and robustness of complex 2, the white light emission can be improved via a heating process.

Highly stable and sensitive LnMOF ratiometric thermometers constructed with mixed ligands.

The mixed-lanthanide metal-organic frameworks (M'LnMOFs) applied for accurate, non-invasive and self-reference temperature measurements have been only recently recognized. It is a great challenge for chemists to fulfil the requirements of a thermostable structure, intense luminescence and high temperature sensitivity on one LnMOF ratiometric thermometer for thermometric applications. By choosing 2,4-(2,2':6',2''-terpyridin-4'-yl)-benzenedisulfonic acid (H2DSTP) as the first ligand and changing the ancillary ligand to oxalic acid (OA) or 1,4-benzene dicarboxylic acid (BDC), we have successfully developed two types of highly stable and sensitive thermometers [Tb1-xEux(OA)0.5(DSTP)]·3H2O and [Tb1-xEux(BDC)0.5(DSTP)]·2H2O (x = 0.01, 0.02) that in addition exhibit brilliant luminescence over a wide temperature range, providing a new strategy to explore luminescence-based M'LnMOF thermometers.

A white-light-emitting LnMOF with color properties improved via Eu3+ doping: an alternative approach to a rational design for solid-state lighting.

The intrinsic white-light-emitting properties of a lanthanide metal-organic framework that approach requirements for solid-state lighting are easily improved by incorporating minute quantities of red-emitting Eu(3+) into the host framework by virtue of the isostructural character of the La(3+) and Eu(3+) compounds and efficient sensitization of ligands toward Eu(3+) ions.

Spontaneous asymmetric crystallization of a quartz-type framework from achiral precursors.

An enantioenriched three-dimensional quartz-type framework {[Ni(1.5)(tzdc)(H(2)O)(3)]·3H(2)O}(n) (H(3)tzdc = 4H-1,2,4-triazole-3,5-dicarboxylic acid) possessing chiral channels is obtained through spontaneous asymmetric crystallization without any enantiopure additive.

Second-order nonlinear optical properties of transition metal clusters [MoS4Cu4X2Py2] (M=Mo, W; X=Br, I).

We present in this paper the second-order nonlinear optical properties of a series of penta-nuclear metal clusters [MS4Cu4X2Py6] (M=Mo, W; X=Br, I) on the basis of the hyper-Rayleigh scattering experiments and the first-principle calculations (TDDFT). The measurements obtain the notably large dynamic quadratic hyperpolarizabilities at 1064 nm [beta(-2omega, omega, omega) values are around 200x10(-30) esu] and, by extrapolation, a large static values around 60x10(-30) esu. The computational results of the electronic excitation energies and quadratic hyperpolarizabilities by TDDFT method are in good agreement with the experimental values and by careful examination they are both dependent on the nature of the metals. The in-depth analysis of the mechanism for the second-order response unambiguously shows the evidence of the contribution of direct metal-metal interaction charge transfers. This provides a new tool to tune nonlinear optical properties in exploiting metal cluster materials and molecular devices.