16858-01-8Relevant academic research and scientific papers
A series of organic-inorganic hybrid materials consisting of flexible organic amine modified polyoxomolybdates: synthesis, structures and properties
Gong, Chunhua,Zeng, Xianghua,Zhu, Chengfeng,Shu, Jiahui,Xiao, Pingxiu,Xu, Hao,Liu, Lichun,Zhang, Junyong,Zeng, Qingdao,Xie, Jingli
, p. 106248 - 106259 (2016)
A series of organic-inorganic hybrid complexes based on different types of polyoxomolybdates and transition metal complexes, namely, [Zn2(TPMA)2(H2P2Mo5O23)]·11H2O (1), [Zn2(TPMA)2(Mo8O26)] (2), [Co2(TPMA)2(Mo8O26)] (3), [Ni2(TPMA)2(Mo8O26)(H2O)2] (4), [Ni2(TPMA)2(2-PA)(H2O)](PMo12O40) (5) [Cu2(TPMA)2(Mo8O26)] (6), 2[Cu(TPMA)(CrMo6(OH)6O18)]·H[Cu2(TPMA)2(CrMo6(OH)6O18)]·4H2O (7) (TPMA = Tris[(2-pyridyl)methyl]amine, 2-PA = 2-picolinic acid), have been successfully synthesized under hydrothermal conditions. All complexes were characterized by single-crystal X-ray structural analysis, powder X-ray diffraction, IR spectroscopy and TG analysis. All the complexes showed polyoxomolybdate-based zero-dimensional (0D) structures, and could be further extended into three-dimensional (3D) supramolecular frameworks through hydrogen bonding interactions. In addition, the electrochemical properties of complexes 1-7 have been investigated. Interestingly, some complexes have efficient photocatalytic activities to degradate pararosaniline hydrochloride dye molecules.
Comparative Study of the Catalytic Oxidation of Catechols by Copper(II) Complexes of Tripodal Ligands
Malachowski, Mitchell R.,Huynh, Hong B.,Tomlinson, Laura J.,Kelly, Richard S.,Furbee, James W.
, p. 31 - 36 (1995)
Copper(II) complexes of the ligands tris(2-pyridylmethyl)amine (tpyma), tris(2-pyridylethyl)amine (tpyea), tris(3,5-dimethylpyrazol-1-ylmethyl)amine (tpzma) and tris(3,5-dimethylpyrazol-1-ylethyl)amine (tpzea) were prepared.The complexes, Cl or 2, were characterized by a combination of absorption and EPR spectroscopies and chemical analysis.The ability of the complexes to oxidize 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone has been studied and the results show that the rate of reaction is dependent on the nature of the heterocyclic donor, its basicity, steric considerations, the chelate ring size and the type of exogenous donor present.Large variations in the rate were observed with the most effective catalysts being those with pyridine donors which formed six-membered chelate rings; the complex 2 was the most active while 2 and Cl were inactive.Electrochemical data for the series of compounds show that there is a non-linear relationship between their ability to oxidize catechols and their reduction potentials.The most effective catalysts were those complexes which exhibited reduction potentials close to 0.00 V, while those that deviated from that potential by 200-300 mV in either direction were largely inactive.Within the range of complexes which were active, a steric match between the substrate and the complex also largely defined their reactivity.Comparisons to the biological system tyrosinase are drawn.
Polypyridyl Co complex-based water reduction catalysts: why replace a pyridine group with isoquinoline rather than quinoline?
Guo, Xusheng,Li, Chao,Wang, Weibo,Hou, Yuanjun,Zhang, Baowen,Wang, Xuesong,Zhou, Qianxiong
, p. 2042 - 2049 (2021)
The electronic effect of the substituent has been fully leveraged to improve the activity of molecular water reduction catalysts (WRCs). However, the steric effect of the substituents has received less attention. In this work, a steric hindrance effect was observed in a quinoline-involved polypyridyl Co complex-based water reduction catalyst (WRC), which impedes the formation of Co(iii)-H from Co(i), two pivotal intermediates for H2evolution, leading to significantly impaired electrocatalytic and photocatalytic activity with respect to its parent complex, [Co(TPA)Cl]Cl (TPA = tris(2-pyridinylmethyl)-amine). In sharp contrast, two isoquinoline-involved polypyridyl Co complexes exhibited significantly improved H2evolution efficiencies compared to [Co(TPA)Cl]Cl, benefitting mainly from the more basic and conjugated features of isoquinoline over pyridine. The dramatically different influences caused by the replacement of a pyridine group in the TPA ligand by quinoline and isoquinoline fully demonstrates the important roles of both the electronic and steric effects of a substituent. Our results may provide novel insights for designing more efficient WRCs.
Tuning the charge distribution and photoswitchable properties of cobalt-dioxolene complexes by using molecular techniques
Beni, Alessandra,Dei, Andrea,Laschi, Serena,Rizzitano, Mario,Sorace, Lorenzo
, p. 1804 - 1813 (2008)
A series of cobalt complexes [Co(Mentpa)(diox)]PF 6·sol (diox = 3,5-di-tert-butyl-1,2-dioxolene; sol=ethanol, toluene; tpa = tris(2-pyridylmethyl)amine) were prepared by using tripod-like Mentpa (n = 0, 1, 2, 3), derived from tpa by successive introduction of methyl groups into the 6-position of the pyridine moieties, as an ancillary ligand. The steric hindrance induced by this substitution modulates the redox properties of the metal acceptor, thus determining the charge distribution of the metal-dioxolene moiety at room temperature. All of these complexes were characterised by using diffractometric studies, electronic spectroscopic analysis, and magnetic susceptibility measurements. In the solid state, the [Co(Mentpa)(diox)]+ ions (n = 0, 1) can be described as diamagnetic cobalt(III)-catecholato derivatives, whereas a cobalt(II)-semiquinonato description seems appropriate for the paramagnetic [Co(Me3tpa)(diox)]+ complex. The complex [Co(Me 2tpa)-(diox)]PF6·C2H5OH undergoes entropy-driven valence tautomeric interconversion at room temperature. Optically induced valence tautomerism was observed by irradiation of [Co(Mentpa)(diox)]PF6 complexes (n = 0, 1, 2) at cryogenic temperatures. The different relaxation kinetics of the photoinduced metastable phases are related to the respective free-energy changes of the interconversion, as estimated by cyclic voltammetric experiments at room temperature, and to the different lattice interactions, as supported by structural data. These results show the importance of molecular techniques for controlling the relaxation properties of photoinduced metastable species. At the same time, this behaviour strongly suggests that this paradigm exhibits intrinsic limits because of the less controllable factors that affect the process.
Tris(8-methoxy-2-quinolylmethyl)amine (8-MeOTQA) as a highly fluorescent Zn2+ probe prepared by convenient C3-symmetric tripodal amine synthesis
Mikata, Yuji,Nodomi, Yuki,Ohnishi, Risa,Kizu, Asako,Konno, Hideo
, p. 8021 - 8030 (2015)
A convenient synthesis of C3-symmetric tribenzylamine (TBA) derivatives has been investigated. The reaction of benzyl chlorides with acetaldehyde ammonia trimer (1) in the presence of base afforded tribenzylamines in high yields. This efficient method allows the diverse synthesis of TPA (tris(2-pyridylmethyl)amine) and TQA (tris(2-quinolylmethyl)amine) derivatives. Among the TQA compounds prepared, tris(8-methoxy-2-quinolylmethyl)amine (8-MeOTQA, 4) exhibited superior properties as a fluorescent zinc probe with high quantum yield (Zn = 0.51) and high sensitivity (limit of detection (LOD) = 3.4 nM). The X-ray crystallographic analysis of [Zn(8-MeOTQA)]2+ revealed that the steric and electronic effect of 8-methoxy substituents kicks out the solvent and counterion molecules from the metal coordination sphere, resulting in short Zn-Nquinoline coordination distances (2.04-2.07 ?). The pseudo hexacoordinate complex of 6-methoxy derivative, [Zn(6-MeOTQA)(DMF)(ClO4)]+, exhibited longer Zn-Nquinoline distances (2.07-2.19 ?) and much smaller fluorescence intensity (Zn = 0.027). The replacement of one of the three 8-methoxyquinolines with pyridine also afforded much less fluorescent zinc complex (Zn = 0.095) due to the solvent coordination (Zn-Nquinoline = 2.05-2.18 ? for [Zn(8-MeOBQPA)(CH3OH)]2+).
Star-like oligo-arginyl-maltotriosyl derivatives as novel cell-penetrating enhancers for the intracellular delivery of colloidal therapeutic systems
Bersani, Sara,Salmaso, Stefano,Mastrotto, Francesca,Ravazzolo, Elena,Semenzato, Alessandra,Caliceti, Paolo
, p. 1415 - 1425 (2012)
A novel nonpeptide, multiarmed oligo-arginyl derivative was engineered as a cell-penetration enhancer for the delivery of bioactive macromolecules and colloidal drug systems. Hepta-arginyl-maltotriosylamido-N-acetyl-dodecanoyl acid (Arg7-Malt-NAcC12 acid) was synthesized through a carefully designed multistep chemical protocol, as follows: (1) maltotriose derivatization with 12-amino-dodecanoic acid and acetylation of the free amino group; (2) esterification of the maltotriosyl hydroxyl groups with 2-bromo-isobutyryl bromide; and (3) synthesis of star-like oligomer bearing multiple copies of arginine moieties under atom transfer radical polymerization (ATRP) conditions. The intermediates and final product were characterized by 1H NMR, IR, mass spectrometry, colorimetric assays, and elemental analysis. Cytotoxicity studies on the final polymeric material showed that this novel cell-penetrating enhancer does not have significant toxic effects on MCF-7 and MC3T3-E1 cell lines. The IC50 was greater than 100 μM with both cell lines, while the polyethylenimine with similar average molecular mass (Mn) that was used as a reference showed an IC50 of 30 and 40 μM, for MCF-7 and MC3T3-E1, respectively. The biological properties of the novel bioconjugate were investigated using a fluorescein-labeled bovine serum albumin (FITC-BSA) as a hydrophilic cargo model. MCF-7 and MC3T3-E1 cells were incubated for 60 min with the Arg7-Malt-NAcC12- conjugated FITC-BSA [(Arg7-Malt-NAcC12) 2-FITC-BSA] or FITC-BSA, and the intracellular fluorescence level was analyzed by spectrofluorimetric analysis of cell lysate, cytofluorimetry, and confocal microscopy. The fluorescence of the lysate of MCF-7 and MC3T3-E1 cells that were incubated with (Arg7-Malt-NAcC12) 2-FITC-BSA at 37 °C was approximately 4.5 times higher than the fluorescence obtained with cells incubated with FITC-BSA. At 4 °C, the cell uptake of (Arg7-Malt-NAcC12)2-FITC-BSA was only 2 times higher than that of FITC-BSA. Cytofluorimetric studies showed that, after (Arg7-Malt-NAcC12)2-FITC-BSA treatment, over 80% of MCF-7 cells and over 95% of MC3T3-E1 cells displayed enhanced fluorescence. Confocal investigations showed punctuated fluorescence within the cytosol in both cell lines, indicating that (Arg7-Malt-NAcC 12)2-FITC-BSA was confined to endosomes, with no fluorescence observed in the nucleus.
Photocatalytic hydrogen evolution by Cu(II) complexes
Wang, Junfei,Li, Chao,Zhou, Qianxiong,Wang, Weibo,Hou, Yuanjun,Zhang, Baowen,Wang, Xuesong
, p. 5439 - 5443 (2016)
[Cu(TMPA)Cl]Cl (1) and [Cu(Cl-TMPA)Cl2] (2) exhibited efficient photocatalytic H2 evolution with a TON of 6108 and 10014 (6 h), respectively, in CH3CN/H2O solution (9:1, v/v) containing an Ir complex as the photosensitizer and triethylamine as the sacrificial reductant, representing the first example of photocatalytic Cu complex-based water reduction catalysts.
Photo-induced water oxidation based on a mononuclear cobalt(II) complex
Wang, Hongyan,Lu, Yongbin,Mijangos, Edgar,Thapper, Anders
, p. 467 - 473 (2014)
Photo-induced water oxidation based on first row transition metal complexes has drawn much attention recently as a part of the efforts to design systems for solar fuel production. Here, the classic tetradentate ligand TPA (tris(2-pyridylmethyl)amine) is used together with cobalt(II) in CH 3CN to form a mononuclear cobalt complex [Co(TPA)Cl]Cl. Single crystal X-ray diffraction shows that [Co(TPA)Cl]Cl is composed of discrete cationic units with a penta-coordinate cobalt center, along with chloride counter ions. In borate buffer, the Co complex acts as a water oxidation catalyst, as shown by the presence of a catalytic wave in electrochemistry. Under visible light irradiation, in the presence of photosensitizer and electron acceptor, the Co complex catalyzes O2 evolution with a turnover frequency (TOF) of 1.0 mol(O2)·mol(Co) -1·s-1 and a turnover number (TON) of 55 mol(O 2)·mol(Co)-1 in pH 8 borate buffer. Copyright
Fast Oxygen Reduction Catalyzed by a Copper(II) Tris(2-pyridylmethyl)amine Complex through a Stepwise Mechanism
Langerman, Michiel,Hetterscheid, Dennis G. H.
, p. 12974 - 12978 (2019)
Catalytic pathways for the reduction of dioxygen can either lead to the formation of water or peroxide as the reaction product. We demonstrate that the electrocatalytic reduction of O2 by the pyridylalkylamine copper complex [Cu(tmpa)(L)]2+ in a neutral aqueous solution follows a stepwise 4 e?/4 H+ pathway, in which H2O2 is formed as a detectable intermediate and subsequently reduced to H2O in two separate catalytic reactions. These homogeneous catalytic reactions are shown to be first order in catalyst. Coordination of O2 to CuI was found to be the rate-determining step in the formation of the peroxide intermediate. Furthermore, electrochemical studies of the reaction kinetics revealed a high turnover frequency of 1.5×105 s?1, the highest reported for any molecular copper catalyst.
Quantitative Estimation of Ising-Type Magnetic Anisotropy in a Family of C3-Symmetric CoII Complexes
Mondal, Amit Kumar,Jover, Jesús,Ruiz, Eliseo,Konar, Sanjit
, p. 12550 - 12558 (2017)
In this paper, the influence of the structural and chemical effects on the Ising-type magnetic anisotropy of pentacoordinate CoII complexes has been investigated by using a combined experimental and theoretical approach. For this, a deliberate design and synthesis of four pentacoordinate CoII complexes [Co(tpa)Cl]?ClO4 (1), [Co(tpa)Br]?ClO4 (2), [Co(tbta)Cl]?(ClO4)?(MeCN)2?(H2O) (3) and [Co(tbta)Br]?ClO4 (4) by using the tripodal ligands tris(2-methylpyridyl)amine (tpa) and tris[(1-benzyl-1 H-1,2,3-triazole-4-yl)methyl]amine) (tbta) have been carried out. Detailed dc and ac measurements show the existence of field-induced slow magnetic relaxation behavior of CoII centers with Ising-type magnetic anisotropy. A quantitative estimation of the zero-field splitting (ZFS) parameters has been effectively achieved by using detailed ab initio theory calculations. Computational studies reveal that the wavefunction of all the studied complexes has a very strong multiconfigurational character that stabilizes the largest ms=±3/2 components of the quartet state and hence produce a large negative contribution to the ZFS parameters. The difference in the magnitudes of the Ising-type anisotropy can be explained through ligand field theory considerations, that is, D is larger and negative in the case of weak equatorial σ-donating and strong apical π-donating ligands. To elucidate the role of intermolecular interactions in the magnetic relaxation behavior between adjacent CoII centers, a diamagnetic isostructural ZnII analog (5) was synthesized and the magnetic dilution experiment was performed.
