Effect Of Central Metal Research Articles

Benzimidazolium‐Decorated Metalloporphyrin Molecule and Polymer: a Reliable Preparation Method and Application in Catalyzing the Cycloaddition Reaction of CO2and Epoxides

AbstractDue to the synergistic effect of central metal and halide anion, cationic metalloporphyrins and derivatives exhibit outstanding catalytic activities for the cycloaddition reaction of epoxides and carbon dioxide. Herein, a generic strategy was developed to synthesize the benzimidazolium‐containing metalloporphyrin molecule and polymer. To demonstrate the method feasibility, we firstly synthesized the molecule1H, in which the benzimidazole groups were in‐site constructed by the cyclization of 5,10,15,20‐(4‐carboxyphenyl)‐porphyrin (H2TCPP) witho‐diaminobenzene (PEA). After post‐synthetic ionization and metallization, I−and Zn2+were introduced as the nucleophile and Lewis acid, respectively. The structure of1ZnILwas confirmed by single crystal X‐ray diffraction analysis. By using the similar conditions of model reaction,H2TCPPwas copolymerized with 1,2,4,5‐tetraaminobenzene (BTA) to prepare the polymerP‐1ZnIL. The prepared cationic molecule1ZnILand polymerP‐1ZnILshowed comparable activities in catalyzing the cycloaddition of carbon dioxide with epoxides to cyclic carbonates compared to the reported bifunctional catalysts based on metalloporphyrins.

Group 6 (Cr, Mo, W) and Group 7 (Mn, Re) bipyridyl tetracarbonyl complex for electrochemical CO2 conversion: DFT and DLPNO-CCSD(T) study for effects of the central metal on redox potential, thermodynamics, and kinetics

To reveal the effects of central metal on the catalytic efficiency, we estimated the thermodynamics and kinetics of CO2 reduction by Group 6 and Group 7 metal bpy tetracarbonyl complexes using DLPNO-CCSD(T) method. The applied potential V1 required for the formation of the two-electron reduced species of the metal bpy tetracarbonyl complex is greater than the applied potential V2 required for the formation of the two-electron reduced species of the metal bpy tricarbonyl complex, and for each applied potential, the effect of the central metal on the reaction process was investigated. At applied potential V1, CO2 binding to metal center was the rate-limiting step in CO2 reduction by the Group 6 complex, while the second proton transfer was the rate-limiting step for CO2 reduction by the Group 7 complex. At applied potential V2, the rate-limiting step was the dissociation of the CO ligand from the central metal, except for Cr.

Beta-Substituent and Metal Effect on Their Structures and Electrochemical Properties

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. In particular, twisted π-conjugated systems have been focused on for potential applications to solution processible organic materials. To date, numerous twisted organic molecules such as twistacenes have been synthesized. Under these situations, we found that oxidation of beta-amino substituted porphyrins provided highly twisted porphyrin dimers in excellent yield. Sequential use of amination and oxidation of 5,10,15,20-tetramesitylporphyrins afforded highly twisted porphyrin oligomers. The structures of the dimers proved dependent on substituents at porphyrin periphery. This time, we succeeded in the synthesis of beta-substituted porphyrin oligomers by using the oxidative dimerization protocol. Introduction of more bulky substituents at meso-positions on oxidation process provided the corresponding twisted porphyrin dimers with larger twisted angles. As a result, beta-substituents induced more distortion of porphyrin oligomers. In addition, electrochemical analysis revealed the distortion caused reduction of electronic communications between each porphyrin unit. We also found beta-methyl substituted porphyrin oligomer exhibited solvent-dependent and temperature dependent optical property. Theoretical calculations as well as electrochemical measurements suggested that conformational change by solvent and temperature caused change of absorption spectrum of the tetramer. Such conformational change dependent on solvent is quite rare for porphyrin oligomers and that should lead to novel stimuli-responsive porphyrin oligomers.Secondly, we also investigated the central metal effect on the electrochemical properties and structures of the dimers. The central Ni(II) metal can be readily removed by treatment of concentrated sulfonic acid. Insertion of Zn(II) and Cu(II) metals induced planarization of porphyrin planes, resulting in smaller twisting angle of the corresponding dimers. In the case of the Cu(II) complex, the presence of magnetic interactions between two porphyrin units were revealed by temperature dependent magnetic susceptibility measurements. In this presentation, we will disclose the structural characterizations of these dimers and would like to show the relationship between electrochemical properties and the conformations of porphyrin dimers. Figure 1

Detonation nanodiamonds-phthalocyanine photosensitizers with enhanced photophysicochemical properties and effective photoantibacterial activity.

The nanophotosensitizers based on acetophenoxy tetrasubstituted metallophthalocyanines (MPc) and detonation nanodiamonds (DNDs) were successfully formed and their photophysicochemical properties were determined. The zinc(II)Pc and indium(III)Pc complexes along with their nanoconjugates were found to have high singlet oxygen quantum yields (0.72 - 0.84) associated with the heavy central metal effect. The ability of the functional groups present on the DNDs to bind to the bacteria cell and the improved solubility of the nanoconjugates due to DNDs resulted in effective photodynamic antimicrobial therapy (PACT) activity against S. aureus planktonic cells, with the highest log reduction of 9.72 ± 0.02 for the conjugate of InPc conjugate with DNDs after 30 min irradiation. PACT studies were investigated at a dose of 10 μg/mL for each sample. The results suggest that the readily synthesized nanoconjugates can be used as appropriate PACT agents.

The effect of central metal in phthalocyanine for photocatalytic hydrogen evolution via artificial photosynthesis

Abstract Phthalocyanines (Pcs) are promising sensitizers in photocatalytic hydrogen evolution reaction from water splitting owing to the unique absorption properties and familiar sensitizers for light phase of photosynthesis. In this paper, two phthalocyanines (Pcs) bearing tetra carboxylic acid at the peripheral position with Zn and Co atoms as a central metal have been prepared in order to investigate the effect of the central metal atoms on the performance of photocatalytic hydrogen evolution from water splitting for mimicking photosynthesis. The photoelectrochemical and photocatalytic hydrogen evolution experiments have been carried out by using Pcs sensitized TiO2 (TiO2, ZnPc/TiO2 and CoPc/TiO2) and Pt co-catalyst in the presence of triethanolamine (TEOA) as a sacrificial electron donor under visible light. The hydrogen production rate of ZnPc/TiO2 and CoPc/TiO2 have been determined as the 1146 and 1051 μmolg−1h−1, respectively. The hydrogen evolution rates of ZnPc/TiO2 and CoPc/TiO2 have been enhanced by in situ photodeposited Pt, which are reached by 3448 and 3328 μmolg−1h−1 for the ZnPc/TiO2/Pt and CoPc/TiO2/Pt, respectively. These results have been established that ZnPc sensitized TiO2 shows more photocatalytic activity than CoPc sensitized TiO2 in the both absence and presence of Pt. These obtained results can be attributed to the spectral response of Pc sensitizers.

Theoretical study of first row transitional metals effects on stabilization of verdoheme analogues

Heme catabolism is an important physiological process that converts heme to biliverdin in the presence of heme oxygenase which has an essential role in destroying unwanted heme. Verdohemes, the green iron (II) complexes of the 5-oxaporphyrin macrocycle are produced by oxidative destruction of heme. The main goal of this study is clarification of the central metal effect on stabilization of metal 5-oxaporphyrin molecules. To investigate the role of central metal on geometric and electronic properties of five coordinated verdoheme analogues, the first row transitional metals, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, as the central metal of five-coordinated metal 5-oxaporphyrins were systematically calculated without any symmetry constraint by using the B3LYP as DFT method and the 6-31G basis set in gas and solvent phases. According to the results, the stabilization energy of metal 5-oxaporphyrins increases with atomic mass in the solvent phase more than in the gas phase. By reviewing the properties such as the computed frontier orbital energy, HOMO and LUMO gap energy [Formula: see text], hardness [Formula: see text], chemical potential [Formula: see text], softness (s) and electrophilicity [Formula: see text], the pharmaceutical use of this compound can be discussed.

Fluorinated Metal Phthalocyanines: Interplay between Fluorination Degree, Films Orientation, and Ammonia Sensing Properties.

In this work, the sensor response of MPcFx (M = Cu, Co, Zn; x = 0, 4, 16) films toward gaseous NH3 (10–50 ppm) was studied by a chemiresistive method and compared to that of unsubstituted MPc films to reveal the effects of central metals and F-substituents on the sensing properties. A combination of atomic force microscopy and X-ray diffraction techniques have been used to elucidate the structural features of thin MPcFx films deposited by organic molecular beam deposition. It has been shown that the sensor response of MPcF4 films to ammonia is noticeably higher than that of MPc films, which is in good correlation with the values of binding energy between the metal phthalocyanine and NH3 molecules, as calculated by the density functional theory (DFT) method. At the same time, in contrast to the DFT calculations, MPcF16 demonstrated the lesser sensor response compared with MPcF4, which appeared to be connected with the different structure and morphology of their films. The ZnPcF4 films were shown to exhibit a sensitivity to ammonia up to concentrations as low as 0.1 ppm, and can be used for the selective detection of ammonia in the presence of some reducing gases and volatile organic compounds. Moreover, the ZnPcF4 films can be used for the detection of NH3 in the gas mixture simulating exhaled air (N2 76%, O2 16%, H2O 5%, and CO2 3%).

Effects of Ligand, Metal, and Solvation on the Structure and Stability of Contact Ion Pairs Relevant to Olefin Polymerization Catalyzed by Rare-Earth-Metal Complexes: A DFT Study

A full account of theoretical analyses at the DFT level has been reported, focusing on the formation and reactivity of a family of cationic [R-(CH2)n-Py-Sc(CH2SiMe3)]+ catalysts and the effects of counterion and solvation. Two sets of model systems have been considered: (a) structures having identical bridging unit (n = 1) but having varying cyclopentadienyl groups (R = Cp′ (1), R = Ind (2), and R = Flu (3)) and (b) systems with the identical cyclopentadienyl moiety (Flu) but with varying bridging groups (n = 1 (3), n = 0 (4), and n = 2 (5)). For complex 3, various metal ions (Sc, Y, La, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, and Lu) were considered to investigate the effect of central metals on the contact ion pairs (CIP). The formation and separation of CIP were found to be influenced by the steric hindrance of the ligand, the electron-donating ability of the cyclopentadienyl group, and the rare-earth-metal ion radius. The separation enthalpy of the CIPs decreases with increasing dielectronic constant of the s...

Effect of central metals and peripheral substituents on the third-order nonlinear optical properties of tetra-benzimidazole and benzothiazole substituted phthalocyanines

A series of tetra substituted phthalocyanines bearing 2-mercaptobenzimidazole or 2-mercaptobenzothiazole units with different central metals (Zn and In) were synthesized. Their photophysical properties including the parameters of fluorescence and triplet state were studied. The benzothiazole substituted phthalocyanines exhibit stronger third-order nonlinear optical properties (NLO) absorption effects, higher triplet quantum yield (ΦT) and faster intersystem crossing rate compared to the benzimidazole substituted phthalocyanines. With the same central metals, benzothiazole substituted phthalocyanine complexes have the lower fluorescence quantum yield (ΦF), the higher triplet quantum yield (ΦT) and the larger third-order NLO properties as a result of larger conjugated structure and spin-orbit coupling induced by sulphur atoms. The influences of the central metal atoms and the peripheral substituents on the third-order NLO properties are discussed using photophysical parameters.

Central-metal effect on intramolecular vibrational energy transfer of M(CO)5Br (M = Mn, Re) probed by two-dimensional infrared spectroscopy.

Vibrational energy transfer in transition metal complexes with flexible structures in condensed phases is of central importance to catalytical chemistry processes. In this work, two molecules with different metal atoms, M(CO)5Br (where M = Mn, Re), were used as model systems, and their axial and radial carbonyl stretching modes as infrared probes. The central-metal effect on intramolecular vibrational energy redistribution (IVR) in M(CO)5Br was investigated in polar and nonpolar solvents. The linear infrared (IR) peak splitting between carbonyl vibrations increases as the metal atom changes from Mn to Re. The waiting-time dependent two-dimensional infrared diagonal- and off-diagonal peak amplitudes reveal a faster IVR process in Re(CO)5Br than in Mn(CO)5Br. With the aid of density functional theory (DFT) calculations, the central-metal effect on IVR time linearly correlates with the vibrational coupling strength between the two involved modes. In addition, the polar solvent is found to accelerate the IVR process by affecting the anharmonic vibrational potentials of a solute vibration mode.

Low frequency vibrational spectra and the nature of metal-oxygen bond of alkaline earth metal acetylacetonates

Theoretical quantum chemistry calculations were used to assign the observed vibrational band frequencies of Be, Mg, Ca, Sr, and Ba acetylacetonates complexes. Density functional theory (DFT) calculations have been carried out at the B3LYP level, using LanL2DZ, def2SVP, and mixed, GenECP, (def2SVP for metal ions and 6-311++G** for all other atoms) basis sets. The B3LYP level, with mixed basis sets, was utilized for calculations of vibrational frequencies, IR intensity, and Raman activity. Analysis of the vibrational spectra indicates that there are several bands which could almost be assigned mainly to the metal-oxygen vibrations. The strongest Raman band in this region could be used as a measure of the stability of the complex.The effects of central metal on the bond orders and charge distributions in alkaline earth metal acetylacetonates were studied by the Natural Bond Orbital (NBO) method for fully optimized compounds. Optimization were performed at the B3LYP/6-311++G** level for the lighter alkaline earth metal complexes (Be, Mg, and Ca acetylacetonates) while the B3LYP level, using LanL2DZ (extrabasis, d and f on oxygen and metal atoms), def2SVP and mixed (def2SVP on metal ions and 6-311++G** for all other atoms) basis sets for all understudy complexes. Calculations indicate that the covalence nature of metal-oxygen bonds considerably decreases from Be to Ba complexes. The nature of metal-oxygen bond was further studied by using Atoms In Molecules (AIM) analysis. The topological parameters, Wiberg bond orders, natural charges of O and metal ions, and also some vibrational band frequencies were correlated with the stability constants of understudy complexes.

The investigation of the central metal effects on the porphyrin-based DSSCs performance; molecular approach

In this work, we have investigated the insertion of the different metal atoms, -Ca, -Mg and -Zn, into the porphyrin-based dyes for access to more efficient photovoltaic processes in the dye-sensitized solar cells. The photovoltaic processes have been described through the electronic properties of the dyes in the ground and excited states and quantum chemistry descriptors of them. The structural, electronic and spectroscopic properties of the dyes have been obtained by using the natural bond orbital, density functional theory (DFT) and time-dependent-DFT calculations. The preference of applying the metalloporphyrins, especially the Ca-porphyrin complex, in the solar cell is correlated with more proper photovoltaic properties than the free-base porphyrin. Proper photovoltaic properties of the metalloporphyrins are originated from the acceptable electronic chemical potential, electrophilicity indices and electron injection force from the dye to TiO2.

Substitution of PPh3+ as a lipophilic cation on new water-soluble Co(II) and Zn(II) Schiff base complexes: Effect of central metal and substitutional group of ligand on DNA-complex interaction

Abstract New series of water soluble Schiff base complexes by conjugating the lipophilic triphenylphosphonium cation to aromatic moiety of Schiff base ligand, aiming to increase the water solubility and passing through cell membrane were synthesized and characterized. Four new complexes; [N,N′-bis{5-[(triphenylphosphoniumchloride)-methyl]salicylidine}-phenylenediamine] with the formula [Zn(5-CH2PPh3-4-H-1,2-salphen)] (ClO4)2 (1), [Zn(5-CH2PPh3-4-CH3-1,2-salphen)](ClO4)2 (2), [Zn(5-CH2PPh3-4-Cl-1,2-salphen)](ClO4)2 (3), [Co(5-CH2PPh3-4-CH3-1,2-salphen)](ClO4)2 (4) were characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, 31P NMR and UV–vis spectroscopy. Cobalt(II) complex also characterized by thermal gravimetry analysis (TG). DNA interaction studies were investigated by UV–vis absorption spectroscopy, viscosity measurements, circular dichroism (CD) spectroscopy and fluorescence spectroscopy. The DNA binding affinity (Kb) obtained from absorption spectroscopy had this order: 2 > 3 > 4 > 1 > ligand(L) which revealed that metal complexes had more propensities to interact with DNA. In comparing the metal complexes; Zn(II) complexes revealed DNA binding stronger than the corresponding Co(II) analogue. All the complexes displayed cytotoxicity against Raji, Jurkat and A549 cell lines with potency more than that of cisplatin and thus they are good candidate to act as promising anticancer drug. Finally, docking studies were performed to further investigate the DNA binding interactions.

The effects of central metals on ammonia sensing of metallophthalocyanines covalently bonded to graphene oxide hybrids

Stably dispersed aPcM–GO hybrids were prepared by a facile amidation reaction with excellent NH3 sensing properties at room temperature, which rely to the aPcM functionalization on GO.

Effect of Central Metal on Nonlinear Optical Properties of Porphyrins and Their Graphene Composites

The nonlinear optical properties of a series of newly synthesized porphyrins with different central metals and their covalently linked graphene composites are theoretically studied by numerically solving the rate equations and field intensity equation. Calculated results show that all the studied compounds are promising candidates for optical limiters, and graphene–porphyrin composites are expected to be preferable optical limiters because of their excellent nonlinear absorption abilities. In addition, the central metal in the porphyrin is found to be crucial to the optical power limiting and two-photon absorption performances of the compounds. Our results reproduce the experimental measurements. Additionally, special emphasis is placed on the factors that can affect the nonlinear optical properties of the compounds, indicating that one can create favorable nonlinear optical properties of the compounds by changing either the parameters of the absorber, including the concentration and thickness, or the pul...

First investigation on the photophysical and photochemical properties of azo-bridged phthalocyanine photosensitizers

Novel azo-bridged indium(III) acetate phthalocyanine was synthesized by cyclotetramerization reaction of (E)-4-((2,5-dimethoxyphenyl)diazenyl)phthalonitrile. This phthalocyanine was fully characterized by FT-IR, 1H-NMR, UV–vis and MALDI-TOF mass spectroscopic techniques and elemental analyses as well. Additionally, the photophysical and photochemical properties of this phthalocyanine was investigated for the first time. The obtained results were compared with azo-bridged zinc(II) and metal-free phthalocyanine counterparts for determination of central metal effect on these properties. These results were also compared with unsubstituted zinc(II) and indium(III)acetate phthalocyanines for determination of substitution effect on the photophysical and photochemical properties.

Vibrational and Structural Dynamics of Mn(CO)5Br and Re(CO)5Br Examined Using Nonlinear Infrared Spectroscopy

Vibrational and structural dynamics of two transition metal carbonyl complexes, Mn(CO)5Br and Re(CO)5Br were examined in DMSO, using ultrafast infrared pump-probe spectroscopy, steady-state linear infrared spectroscopy and quantum chemistry computations. Two carbonyl stretching vibrational modes (a low-frequency A1 mode and two high-frequency degenerate E modes) were used as vibrational probes. Central metal effect on the CO bond order and force constant was responsible for a larger E-A1 frequency separation and a generally more red-shifted E and A1 peaks in the Re complex than in the Mn complex. A generally broader spectral width for the A1 mode than the E mode is believed to be partially due to vibrational lifetime effect. Vibrational mode-dependent diagonal anharmonicity was observed in transient infrared spectra, with a generally smaller anharmonicity found for the E mode in both the Mn and Re complexes.

Effects of central metal on electronic structure, magnetic properties, infrared and Raman spectra of double-decker phthalocyanine

The effects of the central metal in double-decker metal phthalocyanine on the electronic structure, magnetic properties, and infrared and Raman spectra of the complex were investigated. Electron density distributions were delocalized on the phthalocyanine rings. The narrow energy gap and infrared peaks observed in the ultra-violet–visible–near infrared spectra of the systems were attributed to phthalocyanine ring–ring interactions the between overlapping π-orbitals on each ring. The chemical shift behavior of the phthalocyanine rings was separated by the deformation of their structure owing to nuclear magnetic interaction of the nuclear quadrupole interaction as determined by the electronic field gradient and asymmetric parameters. The magnetic parameters of principle g-tensors were dependent on the perturbation of the crystal field by the hybridization of the d-spin in the central metal conjugated with nitrogen ligands. In the case of the vanadyl system, the IR vibration modes were shifted by the soft vibration mode for resolving the symmetrical structure. Inactive Raman vibration modes arose from no-polarization on the phthalocyanine rings. Double-decker metal phthalocyanines have great advantages for the control of the magnetic mechanism for quantum spin entanglement in the relaxation process.

The effect of central metal on the photodynamic properties of silylated tetraphenylporphyrin derivative

Abstract We have introduced central metal to 5,10,15,20-tetrakis(3′-trimethylsilyl-5′-carboxyphenyl)porphyrin tetrasodium ( 1 ), which shows high photodynamic activity. As central metals, Zn and Pd have been studied, and Zn and Pd improved the quantum yield of intersystem crossing by the heavy atom effect. Pd improved the quantum yield of singlet oxygen sensitization, but Zn decreased the quantum yield. The difference in the quantum yield has been discussed. Cytotoxicity has been evaluated by using a HeLa cell line, and cytotoxicity of metal complexes of 1 were sufficiently low. Pd also improved concentration of photosensitizers in cells, and thus Pd enhanced photodynamic activity. The difference of the photodynamic activity induced by the complexation could be explained by the quantity of singlet oxygen produced in cells, which was evaluated by using the quantum yield of singlet oxygen sensitization, a concentration of photosensitizers in cells, and absorption spectrum of photosensitizers.

Solvent-induced Keggin-based Cd(II)/Ni(II) complexes constructed from pyridyl-tetrazole: Assembly, structures and properties

Three Keggin-based CdII/NiII transition metal complexes, namely, [Cd(3-Hptz)4(CH3O)2](H3PMo12O40)·2H2O (1), [Cd(4-Hptz)4(CH3O)2](H3PMo12O40)·2H2O (2) and {[Ni3(4-ptz)2(4-Hptz)2(μ3-O)(H2O)2](HPMo12O40)}·5H2O (3) [3-ptzH=5-(3-pyridyl)-1H-tetrazole, 4-ptzH=5-(4-pyridyl)-1H-tetrazole], have been synthesized under solvothermal conditions and characterized by IR spectroscopy and single-crystal X-ray diffraction. The mixture of methanol and water was used as the solvent, which play an important role in the formation of compounds 1–3. Compounds 1 and 2 are isostructural. In 1, four 3-Hptz ligands and two methanol molecules coordinate with one CdII ion to form a [Cd(3-Hptz)4(CH3O)2] metal–organic unit, which links the adjacent discrete PMo12O403− (PMo12) anions through hydrogen bonding interactions to construct a 2D supramolecular layer. In compound 3, the tetrazole groups from one 4-Hptz and two 4-ptz ligands coordinate with three Ni ions to form a flat trinuclear subunit, which is further covered by another 4-Hptz vertically, resulting in a {[Ni3(4-ptz)2(4-Hptz)2(μ3-O)(H2O)2]2+ cluster. Adjacent trinuclear clusters connect with each other through pyridyl group of 4-ptz ligands to form a 1D chain. The PMo12 anions hang on both sides of the 1D chain, and methanol molecules may act as structure-directing agent in 3. The effect of central metals on the structures of the title compounds was discussed. In addition, the photocatalytic activities of the title complexes for the degradation of methylene blue under UV and sunlight irradiation have been investigated in detail.