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Inorganics, Volume 8, Issue 9 (September 2020) – 7 articles

Cover Story (view full-size image): [Fe]-hydrogenase (Hmd) is the third type of hydrogenase, which catalyzes reversible hydride transfer from H2 to an organic substrate and contains the iron–guanylylpyridinol (FeGP) cofactor as the prosthetic group. In this article, Huang et al. report the crystal structures of an asymmetric homodimer of Hmd composed of two monomers with and without the FeGP cofactor, and two symmetric Hmd–homodimer structures in complex with guanosine monophosphate and guanylylpyridinol. The structure and reconstitution-kinetic analyses provided insights into the incorporation process of the FeGP cofactor into the Hmd protein in vivo. These results are important for constructing semi-synthetic Hmd using mimic complexes to develop effective H2-activation catalysts. View this paper
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Article
Enhanced Removal of Soluble and Insoluble Dyes over Hierarchical Zeolites: Effect of Synthesis Condition
Inorganics 2020, 8(9), 52; https://doi.org/10.3390/inorganics8090052 - 20 Sep 2020
Cited by 1 | Viewed by 848
Abstract
A hierarchical zeolite ZSM-5 with micro and meso-pore was prepared by optimising the most affecting parameter in sequence of desilication and dealumination. The physicochemical properties of zeolite were characterised with XRD, nitrogen adsorption–desorption, FTIR and SEM. The potential of this zeolite for decolorisation [...] Read more.
A hierarchical zeolite ZSM-5 with micro and meso-pore was prepared by optimising the most affecting parameter in sequence of desilication and dealumination. The physicochemical properties of zeolite were characterised with XRD, nitrogen adsorption–desorption, FTIR and SEM. The potential of this zeolite for decolorisation of CR, RY, MB, RhB, DB-1 and DB-14 was evaluated with adsorption isotherm, thermodynamics, kinetics, and influencing parameter for adsorption. The unique modification of ZSM-5 resulted in lower crystallinity, easier porosity control, rich terminal silanol and unbridged silanol groups which assisted in higher adsorption capacity. The adsorption capacity of the optimum ZSM-5 was 323, 435, 589, 625, 61 and 244 mg/g for CR, RY, MB, RhB, DB-1 and DB-14, respectively. The dye adsorption progressed through pseudo-first-order kinetic and close to the Langmuir model. The adsorption mechanism is proposed mainly through interaction between deprotonated silanol site and the electron-rich dye site. Full article
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Article
Study on Physicochemical and Thermal Properties of Tetrabutylammonium-Based Cation Ionic Salts Induced by Al2O3 Additive for Thermal Energy Storage Application
Inorganics 2020, 8(9), 51; https://doi.org/10.3390/inorganics8090051 - 18 Sep 2020
Cited by 1 | Viewed by 536
Abstract
The physicochemical and thermal properties of tetrabutylammonium bromide (TBA-Br) and tetrabutylammonium hexafluorophosphate (TBA-PF6), and their change with the addition of Al2O3, were investigated using infrared (IR) spectroscopy and by simultaneously conducting thermal thermogravimetric (TG) analysis and differential [...] Read more.
The physicochemical and thermal properties of tetrabutylammonium bromide (TBA-Br) and tetrabutylammonium hexafluorophosphate (TBA-PF6), and their change with the addition of Al2O3, were investigated using infrared (IR) spectroscopy and by simultaneously conducting thermal thermogravimetric (TG) analysis and differential thermal analysis (DTA) to obtain the differential scanning calorimetry (DSC) thermogram. The change in the IR data is characterized by the growth of a large peak in the range of 3500 cm−1 and the reduction of peaks below 1000 cm−1 with the additive concentration. The decomposition temperature determined from the peak in the DTG curve is nearly constant for TBA-Br, and it decreases with the addition of Al2O3 for TBA-PF6, although it does not depend on the concentration of the additives. The DTA curve of ionic salts with the addition of Al2O3 shows additional peaks, which indicates a change in the sample’s temperature at disorder or phase transitions. The variation in the melting temperature with additive concentration is similar to that of decomposition temperature. The maximum heat of fusion value was approximately 67 kJ kg−1 for the doped TBA-Br and TBA-PF6 but was achieved at a different additive concentration. This is due to the additional disorder in the system induced by the dissolution of Al2O3. Full article
(This article belongs to the Section Inorganic Solid-State Chemistry)
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Article
Crystal Structures of [Fe]-Hydrogenase from Methanolacinia paynteri Suggest a Path of the FeGP-Cofactor Incorporation Process
Inorganics 2020, 8(9), 50; https://doi.org/10.3390/inorganics8090050 - 17 Sep 2020
Cited by 1 | Viewed by 823
Abstract
[Fe]-hydrogenase (Hmd) catalyzes the reversible heterolytic cleavage of H2, and hydride transfer to methenyl-tetrahydromethanopterin (methenyl-H4MPT+). The iron-guanylylpyridinol (FeGP) cofactor, the prosthetic group of Hmd, can be extracted from the holoenzyme and inserted back into the protein. Here, [...] Read more.
[Fe]-hydrogenase (Hmd) catalyzes the reversible heterolytic cleavage of H2, and hydride transfer to methenyl-tetrahydromethanopterin (methenyl-H4MPT+). The iron-guanylylpyridinol (FeGP) cofactor, the prosthetic group of Hmd, can be extracted from the holoenzyme and inserted back into the protein. Here, we report the crystal structure of an asymmetric homodimer of Hmd from Methanolacinia paynteri (pHmd), which was composed of one monomer in the open conformation with the FeGP cofactor (holo-form) and a second monomer in the closed conformation without the cofactor (apo-form). In addition, we report the symmetric pHmd-homodimer structure in complex with guanosine monophosphate (GMP) or guanylylpyridinol (GP), in which each ligand was bound to the protein, where the GMP moiety of the FeGP-cofactor is bound in the holo-form. Binding of GMP and GP modified the local protein structure but did not induce the open conformation. The amino-group of the Lys150 appears to interact with the 2-hydroxy group of pyridinol ring in the pHmd–GP complex, which is not the case in the structure of the pHmd–FeGP complex. Lys150Ala mutation decreased the reconstitution rate of the active enzyme with the FeGP cofactor at the physiological pH. These results suggest that Lys150 might be involved in the FeGP-cofactor incorporation into the Hmd protein in vivo. Full article
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Article
The Ca2+-ATPase Inhibition Potential of Gold(I, III) Compounds
Inorganics 2020, 8(9), 49; https://doi.org/10.3390/inorganics8090049 - 30 Aug 2020
Cited by 1 | Viewed by 877
Abstract
The therapeutic applications of gold are well-known for many centuries. The most used gold compounds contain Au(I). Herein, we report, for the first time, the ability of four Au(I) and Au(III) complexes, namely dichloro (2-pyridinecarboxylate) Au(III) (abbreviated as 1), chlorotrimethylphosphine Au(I) ( [...] Read more.
The therapeutic applications of gold are well-known for many centuries. The most used gold compounds contain Au(I). Herein, we report, for the first time, the ability of four Au(I) and Au(III) complexes, namely dichloro (2-pyridinecarboxylate) Au(III) (abbreviated as 1), chlorotrimethylphosphine Au(I) (2), 1,3-bis(2,6-diisopropylphenyl) imidazole-2-ylidene Au(I) chloride (3), and chlorotriphenylphosphine Au(I) (4), to affect the sarcoplasmic reticulum (SR) Ca2+-ATPase activity. The tested gold compounds strongly inhibit the Ca2+-ATPase activity with different effects, being Au(I) compounds 2 and 4 the strongest, with half maximal inhibitory concentration (IC50) values of 0.8 and 0.9 µM, respectively. For Au(III) compound 1 and Au(I) compound 3, higher IC50 values are found (4.5 µM and 16.3 µM, respectively). The type of enzymatic inhibition is also different, with gold compounds 1 and 2 showing a non-competitive inhibition regarding the native substrate MgATP, whereas for Au compounds 3 and 4, a mixed type of inhibition is observed. Our data reveal, for the first time, Au(I) compounds with powerful inhibitory capacity towards SR Ca2+ATPase function. These results also show, unprecedently, that Au (III) and Au(I) compounds can act as P-type ATPase inhibitors, unveiling a potential application of these complexes. Full article
(This article belongs to the Special Issue Gold Complexes)
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Review
Exploring Serum Transferrin Regulation of Nonferric Metal Therapeutic Function and Toxicity
Inorganics 2020, 8(9), 48; https://doi.org/10.3390/inorganics8090048 - 29 Aug 2020
Cited by 3 | Viewed by 1391
Abstract
Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of [...] Read more.
Serum transferrin (sTf) plays a pivotal role in regulating iron biodistribution and homeostasis within the body. The molecular details of sTf Fe(III) binding blood transport, and cellular delivery through transferrin receptor-mediated endocytosis are generally well-understood. Emerging interest exists in exploring sTf complexation of nonferric metals as it facilitates the therapeutic potential and toxicity of several of them. This review explores recent X-ray structural and physiologically relevant metal speciation studies to understand how sTf partakes in the bioactivity of key non-redox active hard Lewis acidic metals. It challenges preconceived notions of sTf structure function correlations that were based exclusively on the Fe(III) model by revealing distinct coordination modalities that nonferric metal ions can adopt and different modes of binding to metal-free and Fe(III)-bound sTf that can directly influence how they enter into cells and, ultimately, how they may impact human health. This knowledge informs on biomedical strategies to engineer sTf as a delivery vehicle for metal-based diagnostic and therapeutic agents in the cancer field. It is the intention of this work to open new avenues for characterizing the functionality and medical utility of nonferric-bound sTf and to expand the significance of this protein in the context of bioinorganic chemistry. Full article
(This article belongs to the Special Issue Metal Complexes with Biological Functions)
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Article
Reactivity of Coordinated 2-Pyridyl Oximes: Synthesis, Structure, Spectroscopic Characterization and Theoretical Studies of Dichlorodi{(2-Pyridyl)Furoxan}Zinc(II) Obtained from the Reaction between Zinc(II) Nitrate and Pyridine-2-Chloroxime
Inorganics 2020, 8(9), 47; https://doi.org/10.3390/inorganics8090047 - 28 Aug 2020
Cited by 1 | Viewed by 698
Abstract
This work reports our first results in the area of the reactivity of coordinated chloroximes. The 1:2:2:2 Zn(NO3)2∙6H2O/Eu(NO3)3∙6H2O/ClpaoH/Et3N reaction mixture in MeOH, where ClpaoH is pyridine-2-chloroxime, resulted in complex [...] Read more.
This work reports our first results in the area of the reactivity of coordinated chloroximes. The 1:2:2:2 Zn(NO3)2∙6H2O/Eu(NO3)3∙6H2O/ClpaoH/Et3N reaction mixture in MeOH, where ClpaoH is pyridine-2-chloroxime, resulted in complex [ZnCl2(L)] (1); L is the di(2-pyridyl)furoxan [3,4-di(2-pyridyl)-1,2,5-oxadiazole-2-oxide] ligand. The same complex can be isolated in the absence of the lanthanoid. The direct reaction of ZnCl2 and pre-synthesized L in MeOH also provides access to 1. In the tetrahedral complex, L behaves as a Npyridyl,Npyridyl-bidentate ligand, forming an unusual seven-membered chelating ring. The Hirshfeld Surface analysis of the crystal structure reveals a multitude of intermolecular interactions, which generate an interesting 3D architecture. The complex has been characterized by FTIR and Raman spectroscopies. The structure of 1 is not retained in DMSO (dimethylsulfoxide) solution, as proven by NMR (1H, 13C, 15N) spectroscopy and its molar conductivity value. Upon excitation at 375 nm, solid 1 emits blue light with a maximum at 452 nm; the emission is of an intraligand character. The geometric and energetic profiles of possible pathways involved in the reaction of ClpaoH and Zn(NO3)2∙6H2O in MeOH in the presence of Et3N has been investigated by DFT (Density Functional Theory) computational methodologies at the PBE0/Def2-TZVP(Cr)∪6-31G(d,p)(E)/Polarizable Continuum Model (PCM) level of theory. This study reveals an unprecedented cross-coupling reaction between two coordinated 2-pyridyl nitrile oxide ligands. Full article
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Article
Synthesis and Thermochromic Luminescence of Ag(I) Complexes Based on 4,6-Bis(diphenylphosphino)-Pyrimidine
Inorganics 2020, 8(9), 46; https://doi.org/10.3390/inorganics8090046 - 26 Aug 2020
Cited by 1 | Viewed by 962
Abstract
Two Ag(I)-based metal-organic compounds have been synthesized exploiting 4,6-bis(diphenylphosphino)pyrimidine (L). The reaction of this ligand with AgNO3 and AgBF4 in acetonitrile produces dinuclear complex, [Ag2L2(MeCN)2(NO3)2] (1) and 1D coordination [...] Read more.
Two Ag(I)-based metal-organic compounds have been synthesized exploiting 4,6-bis(diphenylphosphino)pyrimidine (L). The reaction of this ligand with AgNO3 and AgBF4 in acetonitrile produces dinuclear complex, [Ag2L2(MeCN)2(NO3)2] (1) and 1D coordination polymer, [Ag2L(MeCN)3]n(BF4)2n (2), respectively. In complex 1, µ2-P,P′-bridging coordination pattern of the ligand L is observed, whereas its µ4-P,N,N′,P′-coordination mode appears in 2. Both compounds exhibit pronounced thermochromic luminescence expressed by reversible changing of the emission chromaticity from a yellow at 300 K to an orange at 77 K. At room temperature, the emission lifetimes of 1 and 2 are 15.5 and 9.4 µs, the quantum efficiency being 18 and 56%, respectively. On account of temperature-dependent experimental data, the phenomenon was tentatively ascribed to alteration of the emission nature from thermally activated delayed fluorescence at 300 K to phosphoresce at 77 K. Full article
(This article belongs to the Special Issue Functional Coordination Polymers and Metal–Organic Frameworks)
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