Photocatalytic Hydrogen Production Activity and Mechanism of New Nickel-Based Sulfur Complexes in Aqueous Solution.

The development of industry and the increase in population have caused energy shortages and environmental pollution problems. Developing clean and storable new energy is identified as a key way to solve the problems above. Hydrogen is viewed as the most potential energy carrier due to its high calorific value and pollution-free. To convert solar energy into hydrogen energy, three nickel-based catalysts, Ni(aps)(pys)2 (aps=2-amino-2-phenylacetic salicylaldehyde) (1), Ni(ads)(pys)2 (ads=aniline salicylaldehyde, pys=pyridine-2-thiolate) (2), Ni(acs)(pys)2 (acs=aniline 5-chlorosalicylaldehyde) (3), were synthesized and explored as photocatalysts for hydrogen production. A three-component photocatalytic system for hydrogen production was constructed using target complex as photocatalyst, triethanolamine (TEOA) as electron sacrificial agent and fluorescein (FL) as photosensitizer. Under the optimum conditions, about 1504 µmol of H2 can be obtained with 25 mg catalyst 2 after 3 hours of irradiation. Finally, the hydrogen-production mechanism was discussed by experimental and theoretical methods.

Accelerating Nickel-Based Molecular Construction via DFT Guidance for Advanced Photocatalytic Hydrogen Production.

Understanding the nickel-based molecular catalyst structure and functional relationship is crucial for catalytic hydrogen production in aqueous solutions. Density functional theory (DFT) provides mature theoretical knowledge for efficient catalyst design, significantly reducing catalyst synthesis time and energy consumption. In the present work, three molecular catalysts, Ni(qbz)(pys)2 (qbz = 2-quinoline benzimidazole) (NQP 1), Ni(qbo)(pys)2 (qbo = 2-quinoline benzothiazole) (NQP 2), and Ni(pbz)(pys)2 (pbz = 4-chloro-2,2-pyridylbenzimidazole) (NQP 3) (pys = 2-mercaptopyridine), were designed and synthesized and exhibit a high performance for H2 generation in aqueous solution with a lamp (λ ≥ 400 nm) under visible light irradiation. Under the optimal conditions, a H2 evolution rate as high as 1190 µmol h-1 can be obtained over 25 mg of NQP 1 with the best catalytic performance. DFT has been adopted in this study to unveil the relationship between the ligand qbz and catalyst NQP 1─an efficient step in the design of catalysts with an excellent catalytic performance. We show that, in addition to the presence of the triphenyl ring increasing the overall electron density, rapid electron transfer (ET) from excited fluorescein (Fl) to NQP 1 significantly improves the chance of photogenerated electrons transferring to the active site, ultimately increasing the catalytic activity for H2 production. This work on understanding the correlation between structures and properties of complexes provides a new idea for manufacturing high-performance photocatalysts.

Construction and performance of a simple and efficient g-C3N4 photocatalytic hydrogen production system.

Surface and bulk structure modification is an effective strategy to improve the photocatalytic performance of g-C3N4 (CN). In this work, dilute NaOH solution was used in situ to regulate the CN structure for enhanced photocatalytic hydrogen evolution reaction (HER). Characterization results indicate that after treatment with dilute NaOH solution, the surface of CN was hydroxylated, resulting in the change of CN structure and the increase of BET specific surface area. Furthermore, some Na+ ions can be intercalated into the framework of CN, and form the Na-N bond. These modifications boost the HER activity of CN. The test carried out in 7.5 mM NaOH solution shows the highest activity and it is almost 3.7 times higher than that performed in water. Control tests indicate that hydroxides of other alkali and alkali earth metals such as LiOH, KOH, Ca(OH)2, and Ba(OH)2 have similar promotion effects. This work demonstrates a valid and simple way to enhance the HER activity of CN through performing the reaction in a weakly alkaline solution.

Ru(II) Complexes Bearing O, O-Chelated Ligands Induced Apoptosis in A549 Cells through the Mitochondrial Apoptotic Pathway.

Two new Ru(II) complexes containing O, O-chelated ligands, Ru(dip)2(SA) (Ru-1) and Ru(dmp)2(SA) (Ru-2) (dip = 4,7-diphenyl-1,10-phenanthroline; dmp = 2,9-dimethyl-1,10-phenanthroline; SA = salicylate) were synthesized to evaluate their cytotoxicity in vitro. These complexes were found to exhibit moderate antitumor activity to different types of human cancers, including A549 (human lung carcinoma), MCF-7 (breast cancer), HeLa (human cervical cancer), and HepG2 (human hepatocellular carcinoma) cell lines, but displayed low toxicity to human normal cell lines BEAS-2B (immortalized human bronchial epithelial cells) when compared with that of cisplatin. Further studies revealed that these complexes could induce apoptosis in A549 cells, including activating caspase family proteins and poly (ADP-ribose) polymerase (PARP), reducing Bcl-2/Bax and Bcl-xl/Bad ratio, enhancing cellular reactive oxygen species (ROS) accumulation, triggering DNA damage, decreasing mitochondrial membrane potential (MMP), and leading cytochrome c release from mitochondria. Notably, complex Ru-1 showed low toxicity to developing zebrafish embryos. The obtained results suggest that these new synthetic complexes have the potential to be developed as low-toxicity agents for lung cancer treatment.

Probing DNA-Cleavage Efficiencies of Copper(II) Complexes: A Computational Perspective.

Theoretical studies on DNA-cleavage efficiencies of Cu(II) complexes 1-3 were carried out using density functional theory (DFT). The optimized Cu(II) complexes were allowed to bind to glutathiones (GSH) and ascorbic acids (VC) by the docking program so that corresponding docking structures can be obtained. To predict DNA-cleavage efficiencies, the docking structures of Cu(II) complexes with GSH and VC were further optimized by DFT. The activation energies of electrons from GSH to complexes, the redox potentials of these complexes, and binding energies of these complexes with GSH and VC were calculated. The efficiencies of complexes cleaving DNA were predicted and found to be in agreement with the experimental results. Finally, three occupied molecular orbitals of docking structures (GSH-complexes) were analyzed, and the DNA-cleavage abilities of complexes were also explained by the electron distribution on the three occupied orbitals. This work has important implications understanding the DNA-cleavage mechanism of Cu(II) complexes, which might be helpful for designing novel anticancer Cu(II) complexes for the future.

Three New Supramolecular Coordination Polymers Based on 1H-pyrazolo[3-b]pyridin-3-amine and 1,3-benzenedicarboxylate Derivatives.

Three new supramolecular coordination polymers, namely [Zn(1,3-BDC)(HL)]n (Polymer 1), [Zn3(1,3,5-BTC)2(HL)2(H2O)2]n (Polymer 2), and [Zn9(5-SO3-1,3-BDC)2(L)8(OH)4]n (Polymer 3), were synthesized under solvothermal conditions, based on 1H-pyrazolo[3,4-b]pyridin-3-amine (HL) along with 1,3-benzenedicarboxylate (1,3-BDC) and its derivatives, such as 1,3,5-benzenetricarboxylate (1,3,5-BTC) and 5-sulfo-1,3-benzenedicarboxylate (5-SO3-1,3-BDC). Polymers 1-3 were characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), and single crystal X-ray diffraction analysis. Polymer 1 exhibited a two-dimensional (2D) 4-connected sql net. The neighboring 2D nets were further linked into a 3D supramolecular network by hydrogen-bonding interactions. Polymer 2 displayed a 3D (4, 4, 4)-connected network, which was further stabilized by R 2 2 (14) and S(9) hydrogen-bonding rings along with π-π interactions. The 2D sheet structure of Polymer 3 was constructed by novel quasi-linear nonanuclear Zn(II) units, which further extended into a 3D supramolecular structure by hydrogen-bonding interactions. The solid-state photoluminescence properties of Polymers 1-3 were also investigated.

Theoretical study on the DNA interaction properties of copper(II) complexes.

Theoretical studies on DNA-cleavage and DNA-binding properties of a series of Cu(II) complexes [Cu(bimda)(diimine)] 1-5 have been carried out by density functional theory (DFT). The optimized structures of Cu(II) complexes were docked into parallel, antiparallel and mixed G-quadruplexes, with which the binding energies of complexes 1-5 were obtained. The cytotoxicities of these complexes can be predicted preliminarily by the binding energies. To explore the energy changes of Cu(II) complexes in duplex DNA, the optimized structures of these complexes were docked into the duplex DNA, and the obtained docking models were further optimized using QM/MM method. The DNA-cleavage abilities of complexes 1-5 can be predicted accurately and explained reasonably by the computed intra-molecular reorganization energies of these complexes. This work reported here has implications for the understanding of the interaction Cu(II) complexes with the DNA, which might be helpful for the future directing the design of novel anticancer Cu(II) complexes.

Theoretical Studies on DNA-Cleavage Mechanism of Copper(II) Complexes: Probing Generation of Reactive Oxygen Species.

Theoretical studies on DNA-cleavage properties of [Cu(bba)(diimine)] 1-4 have been carried out using density functional theory (DFT) and docking methods. The optimized structures of Cu(II) complexes were docked into DNA, glutathiones (GSH), and ascorbic acids (VC) so that the corresponding docking models were obtained. To explore DNA-cleavage properties of Cu(II) complexes, the docking models of complexes with GSH and VC were further optimized using DFT method, while the docking models of complexes with DNA were optimized using QM/MM method because DNA is a supramolecular system. The rate constants ket between complexes and DNA, GSH, and VC, oxidation-reduction potentials of complexes, and binding energies of complexes with GSH and VC were computed. The DNA-cleavage abilities of Cu(II) complexes in the presence VC, GSH, and H2O2 were explored and the experimental results could be reasonably explained. Finally, the DNA-cleavage mechanism of Cu(II) complexes was described in detail, which would contribute to future design of novel anticancer Cu(II) complexes.

Eu3+ functionalized Sc-MOFs: Turn-on fluorescent switch for ppb-level biomarker of plastic pollutant polystyrene in serum and urine and on-site detection by smartphone.

The harm of plastic pollutants for human and environment is being paid more and more attention. Polystyrene (PS) and styrene are toxic compounds used in large quantities in the production of fiberglass reinforced polyesters. In this work, a simple method was designed for independent detecting polystyrene and styrene biomarker (phenylglyoxylic acid, PGA) in serum and urine. We prepared Eu3+ functionalized Sc-based metal-organic frameworks as turn-on fluorescent switch for PGA. The distinct enhanced luminescence is observed from the Eu@MOFs with addition of PGA. The fabricated fluorescent switch has several appealing features including high sensitivity (LOD = 4.16 ppb), quick response time (less than 5s) and broad linear range (0.02mg/mL to 0.5mg/mL). Furthermore, Eu@MOFs exhibits excellent selectivity that it is not affected by congeneric biomarkers. More interestingly, a paper-based probe has been devised. The paper-based fluorescence probe would perform an obvious fluorescence change from navy to red with the variety of PGA content. The practicability of the on-site detection platform for quantitative analysis using a colour scanning APP in smartphone has been also demonstrated by coupled with our proposed paper based fluorescence probe. This work first provides a fast, accurate and sensitive method for independent monitoring PS biomarker PGA, and the paper-based probe exhibit a new idea for design portable and easy to operate sensing devices combine with smartphone.

Novel pyridinium inner salt dye and its complexes: synthesis, crystal structures and photophysical properties.

Two novel metal complexes, namely [Tb2(L)6(H2O)4]·(NO3)6·L2·(H2O)18 (1) and [Hg(L)Cl2]n (2), were obtained by the reaction of D-π-A (D = donor, π = conjugated spacer, A = acceptor) type pyridinium inner salt dye, trans-4-[(p-N,N-dimethylamino)styryl]-N-(2-propanoic-acid) pyridinium (L) with corresponding metal salts. Single crystal X-ray diffraction analyses reveal that compound 1 possesses dinuclear motif in which two Tb(III) ions are linked by four carboxylate groups while complex 2 exhibits 1D chain structure based on Hg(II) ions bridged by carboxylate groups. The linear and non-linear optical properties of complexes 1 and 2 have been studied. Both 1 and 2 exhibit intense single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) in the red range. Results show that the replacement of central ions from Hg(2+) to Tb(3+) influence the two-photon absorption cross-section significantly through increasing the density of the chromophore. However, the peak positions of two-photon excited fluorescence are only slightly affected. Compared with L molecule, complex 1 shows enhanced two-photon absorption cross-section and decreased fluorescent lifetime.

Theoretical studies on DNA-photocleavage efficiency and mechanism of functionalized Ru(II) polypyridyl complexes.

Theoretical studies on the DNA-photocleavage mechanism and efficiency of some Ru(II) polypyridyl complexes as novel reagents have been carried out using the density functional theory (DFT) method. Stable DNA-docking models of Ru(II) polypyridyl complexes were obtained using the docking and DFT methods. The excited-state reduction potentials, electron-transfer (ET) activation energies, and intramolecular reorganization energies were theoretically calculated, and the corresponding frontier molecular orbitals of complexes were also presented. Based on these properties of excited states, the essential component of two different DNA-photocleavage mechanisms, i.e., the photoinduced oxidation-reduction mechanism and the singlet oxygen photosensitization mechanism, has been revealed, and the DNA-photocleavage efficiencies were reasonably explained, and hereby a complex with excellent DNA-photocleavage ability was also designed. This work offers valuable theoretical insight into the property of excited-states and the DNA-photocleavage mechanism of Ru(II) polypyridyl complexes as novel reagents.

Design of Lewis acid-base complex: enhancing the stability and first hyperpolarizability of large excess electron compound.

In the present paper, a new type of Lewis acid-base complex BX3...Li@Calix[4]pyrrole (X = H and F) was designed and assembled based on electride molecule Li@calix[4]pyrrole (as a Lewis base) and the electron deficient molecule BX3 (as a Lewis acid) by employing quantum mechanical calculation. The new Lewis acid-base complex offers an interesting push-excess electron-pull (P-e-P) framework to enhance the stability and nonlinear optical (NLO) response. To measure the nonlinear optical response, static first hyperpolarizabilities (ß 0) are exhibited. Significantly, point-face assembled Lewis acid-base complex BF3...Li@Calix[4]pyrrole (II) has considerable first hyperpolarizabilities (ß 0) value (1.4 × 106 a.u.), which is about 117 times larger than reported 11,721 a.u. of electride Li@Calix[4]pyrrole. Further investigations show that, in BX3...Li@Calix[4]pyrrole with P-e-P framework, a strong charge-transfer transition from the ground state to the excited state contributes to the enhancement of first hyperpolarizability. Theory calculation of enthalpies of reaction (ΔrH0) at 298 K demonstrates that it is feasible to synthetize the complexes BX3...Li@Calix[4]pyrrole. In addition, compared with Li@Calix[4]pyrrole, the vertical ionization potential (VIP) and HOMO-LUMO gap of BX3...Li@Calix[4]pyrrole have obviously increased, due to the introduction of the Lewis acid molecule BX3. The novel Lewis acid-base NLO complex possesses not only a large nonlinear optical response but also higher stability.

Theoretical studies on DNA-photocleavage efficiencies of Ru(II) polypyridyl complexes.

Theoretical studies on the DNA-photocleavage efficiencies of Ru(II) polypyridyl complexes 1-4 have been carried out using density functional theory (DFT). First, an evaluation of the computational accuracy of the redox potentials for [Ru(bpy)(3)](2+) in the ground state and the excited state was tested by different computational methods. Secondly, the redox potentials of complexes 1-4 in the excited state were accurately computed. Finally, the trend in the DNA-photocleavage efficiencies (φ) of complexes 1-4, i.e., φ(4) > φ(3) > φ(2) > φ(1), were reasonably explained by the excited-state reduction potentials and the electron-transfer activation energies. In particular, the DNA-photocleavage efficiencies of two new Ru(II) complexes 3 and 4 were predicted.

Theoretical studies on DNA-photocleavage efficiencies and mechanisms of Ru(II) polypyridyl complexes.

Theoretical studies on the DNA-photocleavage efficiencies and mechanisms of Ru(II) complexes [Ru(bpy)(2)(L)](2+) (bpy = 2,2'-bipyridine; L: dppz = dipyrido[3,2-a:2',3'-c]phenazine; mitatp = 5-methoxy-isatino[1,2-b]-1,4,8,9-tetraazatriphenylene; nitatp = 5-nitro-isatino [1,2-b]-1,4,8,9-tetraazatriphenylene) 1-3 were carried out using density functional theory (DFT). First, the accuracies of redox potentials computed for [Ru(bpy)(3)](2+) in the ground state and the excited state by different computational methods were tested, and then the redox potentials of complexes 1-3 in their excited states were computed accurately. Secondly, the trend in the DNA-photocleavage efficiencies (ϕ) of complexes 1-3 [i.e., ϕ(2) > ϕ(3) > ϕ(1)] was reasonably well explained by their excited-state reduction potentials and their electron-transfer activation energies. Finally, the photoinduced oxidation-reduction mechanism utilized by these complexes was explored, and the DNA-photocleavage process was explained rationally.

Theoretical studies on the related properties of Co(III) polypyridyl complexes interacting with DNA.

Theoretical studies on the related properties of Co(III) polypyridyl complexes [Co(phen)(2)L](3+) (L: dppz = dipyrido[3,2-a:2',3'-c]phenazine; phen = 1,10-phenanthroline; dione = 1,10-phenanthroline-5,6-diketone) 1-3 interacting with DNA, including the DNA-binding, DNA-photocleavage and spectral properties, have been carried out. First, the full geometry-optimizations of these three complexes in their ground states were carried out in aqueous solution. The optimized structures of these three complexes were docked into DNA-base-pairs using the Dock6.0 program. Secondly, the binding modes of complexes 1-3 were revealed in detail and the trend in DNA-binding affinities was reasonably explained. Thirdly, the electronic absorption and emission spectra of docking model of the optimal complex 1 were calculated and simulated. The experimental intense absorption and emission bands of Co(Ш) complex 1 in the presence of DNA were explained in detail, in particular, the reason why the emission spectra of complex 1 in the presence of DNA are greatly stronger than those in the absence of DNA was theoretically elucidated. Finally, the DNA-photocleavage essential of complexes was explored and the DNA photocleavage efficiencies (φ), i.e., φ(1)>φ(2)>φ(3), was also reasonably explained.

Electronic structures, DNA-binding and spectral properties of Co(III) complexes [Co(bpy)2(L)]3+ (L=pip, odhip, hnoip).

Studies on the electronic structures and trend in DNA-binding affinities of a series of Co(III) complexes have been carried out, using the density functional theory (DFT) at the B3LYP/LanL2DZ level. The optimized geometric structures of these Co(III) complexes in aqueous solution are more close to experimental data than those in vacuo. The electronic structures of these Co(III) complexes were analyzed on the basis of their geometric structures optimized in aqueous solution, and the trend in the DNA-binding constants (K(b)) was reasonably explained. In addition, the electronic absorption spectra of these complexes were calculated and simulated in aqueous solution using the time dependent DFT (TDDFT) at the B3LYP/LanL2DZ level. The calculated absorption spectra of these Co(III) complexes in aqueous solution are in satisfying agreement with experimental results, and the properties of experimental absorption bands have been theoretically explained in detail. Meanwhile, in order to explore the solvent effect on the absorption spectra of these Co(III) complexes, their absorption spectra in vacuo were also calculated, and the results show that the calculated absorption spectra of Co(III) complexes are greatly influenced by the solvent effect.