scholarly journals Effects of Chemically-Modified Polypyridyl Ligands on the Structural and Redox Properties of Tricarbonylmanganese(I) Complexes

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5921
Author(s):  
Takatoshi Kanno ◽  
Tsugiko Takase ◽  
Dai Oyama
Keyword(s):  
Methyl Viologen ◽  
Structural Parameters ◽  
Electrochemical Analysis ◽  
Redox Properties ◽  
Molecular Structures ◽  
Central Metal ◽  
Carbonyl Complexes ◽  
Polypyridyl Ligands ◽  
Chemically Modified ◽  
Redox Active

Carbonyl complexes with manganese(I) as the central metal are very attractive catalysts. The introduction of redox-active ligands, such as quinones and methyl viologen analogs into these catalysts, would be expected to lead to superior catalyst performances, since they can function as excellent electron carriers. In this study, we synthesized four tricarbonylmanganese(I) complexes containing typical bidentate polypyridyl ligands, including 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) frameworks bound to redox-active ortho-quinone/catechol or methyl viologen-like units. The molecular structures of the resulting complexes were determined by X-ray crystallography to clarify their steric features. As expected from the infrared (IR) data, three CO ligands for each complex were coordinated in the facial configuration around the central manganese(I) atom. Additionally, the structural parameters were found to differ significantly between the quinone/catechol units. Electrochemical analysis revealed some differences between them and their reference complexes, namely [MnBr(CO)3(phen)] and [MnBr(CO)3(bpy)]. Notably, interconversions induced by two-electron/two-proton transfers between the quinone and catechol units were observed in the phenanthroline-based complexes. This work indicated that the structural and redox properties in tricarbonylmanganese(I) complexes were significantly affected by chemically modified polypyridyl ligands. A better understanding of structures and redox behaviors of the present compounds would facilitate the design of new manganese complexes with enhanced properties.

Ring size matters: supramolecular isomerism in self-assembled redox-active tetra- and hexaruthenium macrocycles

2020 ◽  
Vol 56 (7) ◽  
pp. 1062-1065 ◽  
Author(s):  
Daniel Fink ◽  
Nicole Orth ◽  
Michael Linseis ◽  
Ivana Ivanović-Burmazović ◽  
Rainer F. Winter
Keyword(s):  
Redox Properties ◽  
Molecular Structures ◽  
Ring Size ◽  
Supramolecular Isomerism ◽  
Redox Active ◽  
Self Assembled ◽  
Selective Formation

The selective formation of a kinetically stable metallamacrocyclic hexaruthenium complex and its clean conversion into a thermodynamically more stable tetraruthenium isomer as well their molecular structures and redox properties are reported.

scholarly journals Coordination Chemistry of Ru(II) Complexes of an Asymmetric Bipyridine Analogue: Synergistic Effects of Supporting Ligand and Coordination Geometry on Reactivities

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 27
Author(s):  
Komi Akatsuka ◽  
Ryosuke Abe ◽  
Tsugiko Takase ◽  
Dai Oyama
Keyword(s):  
Coordination Compounds ◽  
Synergistic Effects ◽  
Electrochemical Analysis ◽  
Molecular Structures ◽  
Coordination Geometry ◽  
Polypyridyl Ligands ◽  
X Ray ◽  
Thermal Reactions ◽  
X Ray Crystallography ◽  
Steric Configuration

The reactivities of transition metal coordination compounds are often controlled by the environment around the coordination sphere. For ruthenium(II) complexes, differences in polypyridyl supporting ligands affect some types of reactivity despite identical coordination geometries. To evaluate the synergistic effects of (i) the supporting ligands, and (ii) the coordination geometry, a series of dicarbonyl–ruthenium(II) complexes that contain both asymmetric and symmetric bidentate polypyridyl ligands were synthesized. Molecular structures of the complexes were determined by X-ray crystallography to distinguish their steric configuration. Structural, computational, and electrochemical analysis revealed some differences between the isomers. Photo- and thermal reactions indicated that the reactivities of the complexes were significantly affected by both their structures and the ligands involved.

scholarly journals Insight to Microbial Fe(III) Reduction Mediated by Redox-Active Humic Acids with Varied Redox Potentials

2021 ◽  
Vol 18 (13) ◽  
pp. 6807
Author(s):  
Jingtao Duan ◽  
Zhiyuan Xu ◽  
Zhen Yang ◽  
Jie Jiang
Keyword(s):  
Molecular Weight ◽  
Electron Transfer ◽  
Humic Acids ◽  
Weight Fraction ◽  
Electrochemical Analysis ◽  
Microbial Reduction ◽  
Redox Potentials ◽  
Groundwater Environment ◽  
Redox Active ◽  
Different Molecular Weight

Redox-active humic acids (HA) are ubiquitous in terrestrial and aquatic systems and are involved in numerous electron transfer reactions affecting biogeochemical processes and fates of pollutants in soil environments. Redox-active contaminants are trapped in soil micropores (<2 nm) that have limited access to microbes and HA. Therefore, the contaminants whose molecular structure and properties are not damaged accumulate in the soil micropores and become potential pollution sources. Electron transfer capacities (ETC) of HA reflecting redox activities of low molecular weight fraction (LMWF, <2.5) HA can be detected by an electrochemical method, which is related to redox potentials (Eh) in soil and aquatic environments. Nevertheless, electron accepting capacities (EAC) and electron donating capacities (EDC) of these LMWF HA at different Eh are still unknown. EDC and EAC of different molecular weight HA at different Eh were analyzed using electrochemical methods. EAC of LMWF at −0.59 V was 12 times higher than that at −0.49 V, while EAC increased to 2.6 times when the Eh decreased from −0.59 V to −0.69 V. Afterward, LMWF can act as a shuttle to stimulate microbial Fe(III) reduction processes in microbial reduction experiments. Additionally, EAC by electrochemical analysis at a range of −0.49–−0.59 V was comparable to total calculated ETC of different molecular weight fractions of HA by microbial reduction. Therefore, it is indicated that redox-active functional groups that can be reduced at Eh range of −0.49–−0.59 are available to microbial reduction. This finding contributes to a novel perspective in the protection and remediation of the groundwater environment in the biogeochemistry process.

Synthesis and redox properties of a diphosphene carrying a redox-active sterically protecting group

1999 ◽  
Vol 40 (16) ◽  
pp. 3203-3206 ◽  
Author(s):  
Kyoko Tsuji ◽  
Shigeru Sasaki ◽  
Masaaki Yoshifuji
Keyword(s):  
Redox Properties ◽  
Protecting Group ◽  
Redox Active

On Comparing Experimental and Calculated Structural Parameters

1998 ◽  
Author(s):  
Lothar Schäfer ◽  
John D. Ewbank
Keyword(s):  
Electron Diffraction ◽  
Potential Energy ◽  
Ab Initio ◽  
Structural Parameters ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Torsional Angle ◽  
Internuclear Distances ◽  
Molecular Potential Energy ◽  
The One

The tacit assumption underlying all science is that, of two competing theories, the one in closer agreement with experiment is the better one. In structural chemistry the same principle applies but, when calculated and experimental structures are compared, closer is not necessarily better. Structures from ab initio calculations, specifically, must not be the same as the experimental counterparts the way they are observed. This is so because ab initio geometries refer to nonexistent, vibrationless states at the minimum of potential energy, whereas structural observables represent specifically defined averages over distributions of vibrational states. In general, if one wants to make meaningful comparisons between calculated and experimental molecular structures, one must take recourse of statistical formalisms to describe the effects of vibration on the observed parameters. Among the parameters of interest to structural chemists, internuclear distances are especially important because other variables, such as bond angles, dihedral angles, and even crystal spacings, can be readily derived from them. However, how a rigid torsional angle derived from an ab initio calculation compares with the corresponding experimental value in a molecule subject to vibrational anharmonicity, is not so easy to determine. The same holds for the lattice parameters of a molecule in a dynamical crystal, and their temperature dependence as a function of the molecular potential energy surface. In contrast, vibrational effects are readily defined and best described for internuclear distances, bonded and non-bonded ones. In general, all observed internuclear distances are vibrationally averaged parameters. Due to anharmonicity, the average values will change from one vibrational state to the next and, in a molecular ensemble distributed over several states, they are temperature dependent. All these aspects dictate the need to make statistical definitions of various conceivable, different averages, or structure types. In addition, since the two main tools for quantitative structure determination in the vapor phase—gas electron diffraction and microwave spectroscopy—interact with molecular ensembles in different ways, certain operational definitions are also needed for a precise understanding of experimental structures. To illustrate how the operations of an experimental technique affect the nature of its observables, gas electron diffraction shall be used as an example.

scholarly journals Water-Soluble Bismuth(III) Polynuclear Tyrosinehydroximate Metallamacrocyclic Complex: Structural Parallels to Lanthanide Metallacrowns

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4379
Author(s):  
Marina A. Katkova ◽  
Grigory Y. Zhigulin ◽  
Roman V. Rumyantcev ◽  
Galina S. Zabrodina ◽  
Vladimir R. Shayapov ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Structural Parameters ◽  
Molecular Structures ◽  
Water Soluble ◽  
Thermochromic Properties ◽  
Donor Acceptor ◽  
Coordination Ability ◽  
Synthetic Routes ◽  
Complex Structural

Recently there has been a great deal of interest and associated research into aspects of the coordination chemistry of lanthanides and bismuth—elements that show intriguing common features. This work focuses on the synthesis and characterization of a novel bismuth(III) polynuclear metallamacrocyclic complex derived from aminohydroxamic acid, in order to compare the coordination ability of Bi3+ with the similarly sized La3+ ions. A polynuclear tyrosinehydroximate Bi(OH)[15-MCCu(II)Tyrha-5](NO3)2 (1) was obtained according to the synthetic routes previously described for water-soluble Ln(III)-Cu(II) 15-MC-5 metallacrowns. Correlations between structural parameters of Bi(III) and Ln(III) complexes were analyzed. DFT calculations confirmed the similarity between molecular structures of the model bismuth(III) and lanthanum(III) tyrosinehydroximate 15-metallacrowns-5. Analysis of the electronic structures revealed, however, stronger donor-acceptor interactions between the central ion and the metallamacrocycle in the case of the lanthanum analogue. Thermochromic properties of 1 were studied.

Cis and Gauche Propanal: Microwave Spectra and Molecular Structures

1988 ◽  
Vol 43 (3) ◽  
pp. 271-276
Author(s):  
Jeremy Randell ◽  
A. Peter Cox ◽  
Kurt W. ii Hillig ◽  
Misako Imachi ◽  
Marabeth S. LaBarge ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Molecular Structures ◽  
Bond Lengths ◽  
Microwave Spectra ◽  
Isotopic Species

The microwave spectra of twelve isotopic species of cis propanal (CH3CH2CHO) and six isotopic forms of the less stable gauche rotamer have been studied to determine accurate structural parameters for both conformers. The following bond lengths (Å) and angles (°) were derived:

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