Dual receptor NIR-II organic nanoparticles for multimodal imaging guided tumor photothermal therapy.

The second near-infrared (NIR-II) fluorescence imaging has attracted continuous attention due to its excellent penetration depth and high spatial resolution. Compared with other fluorophores, NIR-II fluorophores, especially NIR-II organic small molecule fluorophores, are favored because of their controllable structure and good biocompatibility. In this study, we designed and synthesized an S-D-A-D-S type small molecule FEA. However, a new molecule was accidentally obtained in the process of synthesis, which was proved to be a double receptor (A-A) type small molecule, namely S-D-A-A-D-S type organic small molecule FEAA. Compared with FEA molecules, FEAA exhibits superior fluorescence performance and can effectively prevent fluorescence quenching. The fluorescence emission of its nanoparticles (NPs) reaches 1109 nm, extends to about 1400 nm, and has a Stokes shift of up to 472 nm. Subsequently, we realized fluorescence/photoacoustic dual-mode imaging (FI/PAI) of nude mouse liver, and finally effectively ablated 4T1 tumor by photothermal therapy (PTT). In general, FEAA NPs exhibit good fluorescence, photoacoustic, and photothermal effects, and are an excellent multifunctional NIR-II organic small molecule fluorophore. As far as we know, there are few reports on A-A type organic small molecules, most of which are cyanines or D-A-D type structures. Therefore, this study has good exploratory significance and reference value for the discovery of NIR-II fluorophores.

The molecular behavior of pyridinium/imidazolium based ionic liquids and toluene binary systems.

Imidazolium and pyridinium-based ionic liquids (ILs) have attracted increasing attention in the extraction of aromatic VOCs. However, fundamental studies on the mechanism of capturing aromatic VOCs have been less reported. In this work, the interactions between two ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) and N-butylpyridinium bis(trifluoromethylsulfonyl)imide (BpyTFSI), and toluene (C6H5CH3), were investigated by using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), excess infrared spectroscopy, hydrogen nuclear magnetic resonance (1H NMR) spectroscopy and quantum chemical calculations. Some conclusions were obtained as follows: (1) H atoms on EMIMTFSI/BpyTFSI were located above or below the benzene ring and were mainly formed as C2-Hπ bonds and C2,6-Hπ bonds with C6H5CH3, respectively. C-Hπ bonds played a significant role in capturing aromatic compounds. (2) Upon adding C6H5CH3, the two IL-C6H5CH3 system's interaction strength was as follows: EMIMTFSI-C6H5CH3 > BpyTFSI-C6H5CH3. (3) Since C6H5CH3 was unable to disrupt the interactions between cations and anions of ion pairs in the two studied IL-C6H5CH3 systems, only ion cluster-C6H5CH3 and ion pair-C6H5CH3 complexes were observed. This work may provide theoretical insights into the separation mechanism for capturing VOCs.

The effect of introducing an ether group into an imidazolium-based ionic liquid in binary mixtures with DMSO.

Ether-functionalized ionic liquids (ILs) have successfully been employed in diverse applications, but their interactions with other solvents are not understood well. In this work, mixtures of 1-methoxyethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EOMIMFSI) and dimethylsulfoxide (DMSO) are studied in terms of their solution structure and hydrogen bonding interactions. The corresponding alkyl-substituted IL 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIMFSI) is analyzed for comparison. A combination of FTIR spectroscopy, excess spectroscopy, and quantum chemical calculations is employed for this purpose. The datasets allow drawing a number of conclusions as follows: (1) the ether group forms intramolecular hydrogen bonds that compete with anions and DMSO; hence, introducing ether groups into the imidazolium-based IL leads to the weakening of hydrogen bonds in the mixtures. (2) With the help of excess spectra and quantum chemical calculations, some complexes such as ion clusters, ion pairs, and individual ions were identified and assigned in the two systems. The solution structures at different concentrations were examined by analyzing the excess spectra of ν(C2-H) and ν(C-D) in the two IL-DMSO-d6 systems. (3) The introduced ether groups result in changes of the main interaction sites, which were found to be concentration-dependent. In the EOMIMFSI-DMSO system, when isolated ions are the main existing form, the C2-Hs are still the main sites interacting with DMSO. However, when ion pairs or larger ion clusters are the main existing species, the C4-Hs are the main sites interacting with DMSO.

Adsorption behavior of dyes from an aqueous solution onto composite magnetic lignin adsorbent.

Magnetic lignosulfonate functional materials that were known to remove several types of dye from water effectively were prepared. The surface of an iron (II,III) oxide (Fe3O4) sample was coated with a layer of organic carbon, and magnetic lignosulfonate (FCS) was synthesised by a crosslinking agent. The morphology, structure, stability and magnetic properties of the materials were characterised by various testing methods. Under experimental conditions, the solution's acidity, alkalinity, contact time, temperature, desorption and dye concentration were measured. The experimental results show that the material reached the highest adsorption capacity at pH = 7. In addition, the adsorption data was similar to that of a single layer, Langmuir adsorption model. The maximum adsorption capacities were 198.24 mg g-1 (Congo Red) and 192.51 mg g-1 (Titan Yellow), respectively. Based on its desorption performance, the material had good recyclability. Therefore, these studies could be used in wastewater treatment. Hopefully, the proposed magnetic composites will inspire more scholars to investigate solutions to the problem of contaminated water resources.

Recognition of the Enzymatically Active and Inhibitive Oxygenous Groups on WO3-x Quantum Dots by Chemical Deactivation and Density Functional Theory Calculations.

The design and construction of efficient nanozymes are vital for bio/chemo-sensing applications, while the systematic catalytic mechanism study is the prerequisite. Tungsten oxide (WO3-x) quantum dots (QDs), an alternative to conventional heavy metal-containing semiconductor QDs, possess peroxidase-like activity but limited catalytic efficiency. Therefore, the functions of the typical oxygenous groups in determining the enzymatic activity of the WO3-x QDs by target-specifically shielding the carboxyl (-COOH), hydroxyl (-OH), or carbonyl (-C═O) groups, respectively, using a chemical titration method. The results show that the -C═O groups could accelerate the nanozymatic catalysis kinetically, while the -OH ones were the catalytically inhibitive sites, which were further corroborated by the density functional theory (DFT) computations. The application potential of the WO3-x derivatives with an enhanced catalytic ability was verified via the colorimetric cholesterol sensing. The proposed method based on the benzoic anhydride (BA)-modified WO3-x QDs with deactivated -OH groups showed a wider linear range and higher sensitivity than those based on the unmodified ones.

Co-synthesis of atomically precise nickel nanoclusters and the pseudo-optical gap of Ni4(SR)8.

Three sizes of atomically precise tiara-like structural Nin(SR)2n (n = 4, 5 and 6) are co-synthesized by a one-pot method and isolated using thin layer chromatography. The molecular formulas of Ni5(SR)10 and Ni6(SR)12 are determined using matrix-assisted laser desorption ionization mass spectrometry, and the tiara-like structures of Ni4(SR)8 and Ni6(SR)12 are proved using single-crystal X-ray crystallography. Nuclear magnetic resonance shows that Ni5(SR)10 has a similar tiara-like structure too. The electrochemical gap enlarges with the increase of the cluster size, which agrees with the calculated HOMO-LUMO gap and optical gap by TD-DFT, but the experimental optical gap is GO(Ni4(SR)8) > GO(Ni6(SR)12) > GO(Ni5(SR)10) due to Ni4(SR)8 owning a pseudo-optical gap at 2.0 eV.

Solvent-regulated preparation of well-intercalated Ti3C2Tx MXene nanosheets and application for highly effective electromagnetic wave absorption.

MXene-derived nanostructures provide the possibility of meeting the requirements of strong absorption, thin thickness and flexible layer for electromagnetic (EM) wave absorption. However, exploration of pure and well-intercalated MXene nanosheets for efficient EM wave absorption is still in the nascent stages. Herein, Ti3C2Tx nanosheets with solvent-manipulated properties were achieved via ultrasonication-solvothermal treatment of bulk Ti3C2Tx in different solvents including dimethylformamide (DMF), ethanol, and dimethyl sulfoxide (DMSO), respectively, because of their combined influences of molecular size, oxidation capability, and boiling point. Especially, it was found that a larger layer space and less oxidation effects on the Ti3C2Tx nanosheets were observed upon solvothermal treatment in DMF than those in ethanol or DMSO treatment. As a result, the DMF-treated Ti3C2Tx nanosheets can be used as highly effective dielectric materials for EM wave absorption. The reflection loss value reached -41.9 dB (more than 99.99%) at 13.4 GHz with the sample thickness of only 1.1 mm. Characterization techniques including scanning electron microscopy, transmission electron microscopy, atomic force microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and density functional theory calculation were used to elaborate the possible mechanisms.

Binuclear Cyclopentadienylmetal Methylene Sulfur Dioxide Complexes of Rhodium and Iridium Related to a Photochromic Metal Dithionite Complex.

The photochromic dithionite complex Cp*2Rh2(µ-CH2)2(µ-O2SSO2) (Cp* = η5-Me5C5) is of interest because it undergoes an unusual fully reversible unimolecular photochemical rearrangement to the isodithionite complex Cp*2Rh2(µ-CH2)2(µ-O2SOSO). In order to obtain more insight into these systems, a comprehensive density functional theory study has been carried out on isomeric Cp2M2(CH2)2(SO2)2 (M = Rh, Ir) derivatives. The experimentally observed rhodium complexes with coupled sulfur dioxide (SO2) units to give dithionite or isodithionite ligands are surprisingly high-energy kinetic isomers in our analysis, reflecting the need for dithionite rather than SO2 for their synthesis. Many isomeric structures containing two separate SO2 ligands are found to lie at lower energies than these dithionite and isodithionite complexes. In the lowest-energy Cp2M2(CH2)2(SO2)2 isomers, the two methylene groups couple to form an ethylene ligand that can be either terminal or bridging. In slightly higher energy structures, a formal hydrogen shift is predicted to occur within the ethylene ligand to give a methylcarbene CH3CH ligand. Isomers with a bridging methylcarbene ligand are energetically preferred over isomers with a terminal methylcarbene ligand. Generation of the lower-energy Cp2Rh2(CH2)2(SO2)2 isomers containing separate SO2 ligands should be achievable through reactions of SO2 with more highly reduced cyclopentadienylrhodium methylene complexes such as Cp*2Rh2(µ-CH2)2.

Phosphomolybdic acid functionalized graphene loading copper nanoparticles modified electrodes for non-enzymatic electrochemical sensing of glucose.

A sensitive non-enzymatic glucose electrochemical biosensor (Cu/PMo12-GR/GCE) was developed based on the combination of copper nanoparticles (CuNPs) and phosphomolybdic acid functionalized graphene (PMo12-GR). PMo12-GR films were modified on the surface of glassy carbon electrode (GCE) through electrostatic self-assembly with the aid of poly diallyl dimethyl ammonium chloride (PDDA). Then CuNPs were successfully decorated onto the PMo12-GR modified GCE through electrodeposition. The morphology of Cu/PMo12-GR/GCE was characterized by scanning electron microscope (SEM). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the electrochemical performances of the biosensor. The results indicated that the modified electrode displayed a synergistic effect of PMo12-GR sheets and CuNPs towards the electro-oxidation of glucose in the alkaline solution. At the optimal detection potential of 0.50 V, the response towards glucose presented a linear response ranging from 0.10 µM to 1.0 mM with a detection limit of 3.0 × 10(-2) µM (S/N = 3). In addition, Cu/PMo12-GR/GCE possessed a high selectivity, good reproducibility, excellent stability and acceptable recovery, which indicating the potential application in clinical field.

A novel class of compounds--superalkalides: M⁺(en)3M'3O⁻ (M, M' = Li, Na, and K; en = ethylenediamine)-with excellent nonlinear optical properties and high stabilities.

With the aid of ab initio calculations at the MP2 level of theory, we designed a novel class of inorganic salts, M(+)(en)3M3'O(-) (M, M' = Li, Na, and K), by using the M3'O superalkalis. These compounds are the first examples of inorganic salts wherein the superalkali occupies the anionic site, and termed superalkalides. The electronic structural features of the M(+)(en)3M3'O(-) superalkalides are very similar to those of the corresponding M(+)(en)3M'(-) alkalides which have been reported by Zurek (J. Am. Chem. Soc., 2011, 133, 4829). In this study, the calculated NLO properties of M(+)(en)3M3'O(-) and M(+)(en)3M'(-) (M, M' = Li, Na, and K) show that both superalkalides and alkalides have significantly large first hyperpolarizabilities (ß0) with the values in the range of 7.80 × 10(3) to 9.16 × 10(4) a.u. and 7.95 × 10(3) to 1.84 × 10(5) a.u., respectively. Computations on the stabilities of M(+)(en)3M3'O(-) and M(+)(en)3M'(-) demonstrate that the M(+)(en)3M3'O(-) superalkalides are preferably stable than the corresponding M(+)(en)3M'(-) alkalides because of the presence of hydrogen bonds in M(+)(en)3M3'O(-). Therefore, the designed superalkalides, M(+)(en)3M3'O(-) (M, M' = Li, Na, and K), with excellent nonlinear optical properties and high stabilities are greatly promising candidates for NLO materials. We hope that this article could attract more research interest in superatom chemistry and for further experimental research.

Mono- and Dinuclear Heteroleptic Cobalt Complexes with α-Diimine and Polyarene Ligands.

Reactions of the dimeric cobalt complex [(L(-) Co)2 ] (1, L=[(2,6-iPr2 C6 H3 )NC(Me)]2 ) with polyarenes afforded a series of mononuclear and dinuclear complexes: [LCo(η(4) -anthracene)] (2), [LCo(µ-η(4) :η(4) -naphthalene)CoL] (3), and [LCo(µ-η(4) :η(4) -phenanthrene)CoL] (4). The pyrene complexes [{Na2 (Et2 O)2 }{LCo(µ-η(3) :η(3) -pyrene)CoL}] (5) and [{Na2 (Et2 O)3 }{LCo(η(3) -pyrene)}] (6) were obtained by treating precursor 1 with pyrene followed by reduction with Na metal. These complexes contain three potential redox active centers: the cobalt metal and both α-diimine and polyarene ligands. Through a combination of X-ray crystallography, EPR spectroscopy, magnetic susceptibility measurement, and DFT computations, the electronic configurations of these complexes were studied. It was determined that complexes 2-4 have a high-spin Co(I) center coupled with a radical α-diimine ligand and a neutral polyarene ligand. Whereas, the ligand L in complexes 5 and 6 has been further reduced to the dianion, the cobalt remains in a formal (I) oxidation state, and the pyrene molecule is either neutral or monoanionic.

α-Diimine nickel complexes of ethylene and related alkenes.

A series of nickel mono(alkene) complexes, [LNi(alkene)], which consist of nickel(0) and neutral α-diimine ligand L (L = [(2,6-iPr2C6H3)NC(Me)]2), have been synthesized. The bonding and structures of the complexes were studied by X-ray diffraction, spectroscopic methods, and DFT computations.

Triple decker sandwiches and related compounds of the first row transition metals with cyclopentadienyl and hexafluorobenzene rings: remarkable effects of fluorine substitution.

The complete series of Cp2M2(µ-C6F6) (M = Ti, V, Cr, Mn, Fe, Co, Ni) structures have been examined theoretically for comparison with their unsubstituted Cp2M2(µ-C6H6) analogues. The singlet triple decker sandwich titanium complex Cp2Ti2(η(6),η(6)-C6F6) with a closed shell electronic structure and a non-planar C6F6 ring is preferred energetically by a wide margin (>20 kcal mol(-1)) over other isomers and spin states. This is in contrast to the hydrogen analogue for which related triplet spin state structures are clearly preferred. A similar low-energy triple-decker sandwich Cp2V2(η(6),η(6)-C6F6) structure is found for vanadium but with a quintet spin state. The later transition metals from Cr to Ni energetically prefer the so-called "rice-ball" cis-Cp2M2(µ-C6F6) structures with varying hapticities of metal-ring bonding, a range of formal orders of metal-metal bonding, and varying spin states depending on the metal atom. Thus the lowest energy Cp2Cr2(µ-C6F6) structures are triplet and quintet structures with pentahapto-trihapto η(5),η(3)-µ-C6F6 rings and formal Cr=Cr double bonds. This contrasts with the structure of Cp2Cr2(µ-C6H6) having a bis(tetrahapto) η(4),η(4)-C6H6 ring and a formal Cr-Cr quadruple bond. The lowest energy Cp2Mn2(µ-C6F6) structures are trans and cis quintet spin state structures. This contrasts with Cp2Mn2(µ-C6H6) for which a closed-shell singlet triple decker sandwich structure is preferred. The lowest energy Cp2Fe2(µ-C6F6) structure is a triplet cis structure with a tetrahapto-dihapto η(4),η(2)-µ-C6F6 ring and a formal Fe-Fe single bond. The lowest energy Cp2Co2(µ-C6F6) structures are singlet spin state structures with formal M-M single bonds and either bridging bis(trihapto) η(3),η(3)-C6F6 or tetrahapto-dihapto η(4),η(2)-C6F6 rings. For Cp2Ni2(µ-C6F6) low energy singlet cis and trans structures are both found. The singlet cis-Cp2Ni2(µ-C6F6) structure has a Ni-Ni single bond of length ∼2.5 Å and a bridging bis(dihapto) η(2),η(2)-C6F6 ligand with an uncomplexed C=C double bond. The singlet trans-Cp2Ni2(µ-C6F6) structure has a bis(trihapto) η(3),η(3)-C6F6 ligand.

Theoretical study of mechanism and dynamics on reaction of (CH3)2NH with CH3.

The mechanism and dynamics for the bimolecular reaction of (CH3)2NH with CH3 have been investigated based on the G3//MP2/6-311G(d,p) level of theory. Our calculations show that when the two reactants approach each other, three prereaction complexes, RC1, RC2, and RC3, can be formed through van der Waals force or hydrogen bonding. From RC1, RC2, and RC3, six routes have been established. Among the six routes, the two routes (R1 and R2) from van der Waals prereaction complex RC1 are the main routes for the title reaction. R1 and R2 are hydrogen abstractions routes associated with HN and HCα atoms in DMA, respectively. The calculated energy barriers for R1 and R2 are 12.3 and 13.7 kcal/mol, respectively. Both the potential energy surfaces of R1 and R2 locate a "reactant-like" transition state, as well as van der Waals complexes before and after the transition state. The slight preference of R1 over R2 might be related to the higher similarity between the structures of RC1 and the transition state for R1 (TS1), namely, the structure of TS1 is more "reactant-like". The rate constants of the two favorable H abstraction reaction routes, R1 and R2, are evaluated over a wide temperature range of 200-3000 K by the variational transition state theory (VTST) methods, which can be expressed as kR1 = 5.30 × 10(-13)(T/1000)(3.0) exp(-2883/T) cm(3) molecule(-1) s(-1) and kR2 = 8.34 × 10(-13)(T/1000)(4.5) exp(-3100/T) cm(3) molecule(-1) s(-1), respectively. The predicted rate constant of the HN abstraction (route R1) is in good agreement with the available experimental data.

Homoleptic tetranuclear rhodium carbonyls: comparison with their iridium analogues.

Density functional theory confirms the experimentally known triply bridged Rh4(CO)9(µ-CO)3 structure to be the lowest-energy structure. The lowest-energy structures of the unsaturated systems Rh4(CO)n (n = 11, 10, 9, 8) are also triply bridged structures with central Rh4 tetrahedra that can be derived from this Rh4(CO)9(µ-CO)3 structure by removal of terminal CO groups in various ways. The M-M distances in these central M4 tetrahedra change very little as CO groups are lost, suggesting reluctance to form metal-metal multiple bonds in these unsaturated systems. The natural bond orbital (NBO) Wiberg bond indices provide depth to this analysis. All of these unsaturated systems are predicted to be highly fluxional, as two to three isomeric structures lie within ∼4 kcal/mol of the global minima. The Rh4(CO)8(µ-CO)2(µ4-CO) structure analogous to the lowest-energy Co4(CO)11 structure with all four atoms of a central Co4 butterfly bridged by a µ-CO group is predicted to lie ∼6 kcal/mol in energy above the lowest-energy Rh4(CO)11 structure. Comparisons of the relative energies of analogous Rh4(CO)n and Ir4(CO)n structures indicate that more highly bridged M4(CO)n structures are energetically much more favorable for rhodium than for iridium. Dissociation energies (for loss of CO) and disproportionation energies are reported.

Distinct stepwise reduction of a nickel-nickel-bonded compound containing an α-diimine ligand: from perpendicular to coaxial structures.

A nickel-nickel-bonded complex, [{Ni(µ-L(.-))}2] (1; L=[(2,6-iPr2C6H3)NC(Me)]2), was synthesized from reduction of the LNiBr2 precursor by sodium metal. Further controllable reduction of 1 with 1.0, 2.0 and 3.0 equiv of Na, respectively, afforded the singly, doubly, and triply reduced compounds [Na(DME)3]·[{Ni(µ-L(.-))}2] (2; DME=1,2-dimethoxyethane), [Na(Et2O)]Na[(L(.-))Ni-NiL(2-)] (3), and [Na(Et2O)]2Na[L(2-)Ni-NiL(2-)] (4). Here L represents the neutral ligand, L(.-) denotes its radical monoanion, and L(2-) is the dianion. All of the four compounds feature a short Ni-Ni bond from 2.2957(6) to 2.4649(8) Å. Interestingly, they display two different structures: the perpendicular (1 and 2) and the coaxial (3 and 4) structure, in which the metal-metal bond axis is perpendicular to or collinear with the axes of the α-diimine ligands, respectively. The electronic structures, Ni-Ni bonding nature, and energetic comparisons of the two structure types were investigated by DFT computations.