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Inorganics, Volume 8, Issue 8 (August 2020) – 2 articles

Cover Story (view full-size image): Two 4-styrylpyridines with a NO2 (L1) or NMe2 (L2) group were axially coordinated to A4 ZnII porphyrins displaying in 5,10,15,20 meso position aryl moieties with remarkable electron withdrawing properties or with moderate to strong electron donor properties. The second order NLO properties of the resulting complexes were measured in solution using the electric-field-induced second harmonic generation technique, and the quadratic hyperpolarizabilities βλ were compared to the DFT-calculated scalar quantities β||. Our investigation shows that different interactions are involved in the NLO response of L1- and L2-substituted A4 ZnII porphyrins, suggesting a role of backdonation-type mechanisms in determination of the negative sign of EFISH βλ, and a not negligible third order contribution f
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Article
Second Order Nonlinear Optical Properties of 4-Styrylpyridines Axially Coordinated to A4 ZnII Porphyrins: A Comparative Experimental and Theoretical Investigation
Inorganics 2020, 8(8), 45; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics8080045 - 14 Aug 2020
Cited by 1 | Viewed by 806
Abstract
In this research, two 4-styrylpyridines carrying an acceptor –NO2 (L1) or a donor –NMe2 group (L2) were axially coordinated to A4 ZnII porphyrins displaying in 5,10,15,20 meso position aryl moieties with remarkable electron withdrawing properties [...] Read more.
In this research, two 4-styrylpyridines carrying an acceptor –NO2 (L1) or a donor –NMe2 group (L2) were axially coordinated to A4 ZnII porphyrins displaying in 5,10,15,20 meso position aryl moieties with remarkable electron withdrawing properties (pentafluorophenyl (TFP)), and with moderate to strong electron donor properties (phenyl (TPP) < 3,5-di-tert-butylphenyl (TBP) < bis(4-tert-butylphenyl)aniline) (TNP)). The second order nonlinear optical (NLO) properties of the resulting complexes were measured in CHCl3 solution by the Electric-Field-Induced Second Harmonic generation technique, and the quadratic hyperpolarizabilities βλ were compared to the Density Functional Theory (DFT)-calculated scalar quantities β||. Our combined experimental and theoretical approach shows that different interactions are involved in the NLO response of L1- and L2-substituted A4 ZnII porphyrins, suggesting a role of backdonation-type mechanisms in the determination of the negative sign of Electric-Field-Induced Second Harmonic generation (EFISH) βλ, and a not negligible third order contribution for L1-carrying complexes. Full article
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Review
Tungstoenzymes: Occurrence, Catalytic Diversity and Cofactor Synthesis
Inorganics 2020, 8(8), 44; https://0-doi-org.brum.beds.ac.uk/10.3390/inorganics8080044 - 31 Jul 2020
Cited by 5 | Viewed by 1301
Abstract
Tungsten is the heaviest element used in biological systems. It occurs in the active sites of several bacterial or archaeal enzymes and is ligated to an organic cofactor (metallopterin or metal binding pterin; MPT) which is referred to as tungsten cofactor (Wco). Wco-containing [...] Read more.
Tungsten is the heaviest element used in biological systems. It occurs in the active sites of several bacterial or archaeal enzymes and is ligated to an organic cofactor (metallopterin or metal binding pterin; MPT) which is referred to as tungsten cofactor (Wco). Wco-containing enzymes are found in the dimethyl sulfoxide reductase (DMSOR) and the aldehyde:ferredoxin oxidoreductase (AOR) families of MPT-containing enzymes. Some depend on Wco, such as aldehyde oxidoreductases (AORs), class II benzoyl-CoA reductases (BCRs) and acetylene hydratases (AHs), whereas others may incorporate either Wco or molybdenum cofactor (Moco), such as formate dehydrogenases, formylmethanofuran dehydrogenases or nitrate reductases. The obligately tungsten-dependent enzymes catalyze rather unusual reactions such as ones with extremely low-potential electron transfers (AOR, BCR) or an unusual hydration reaction (AH). In recent years, insights into the structure and function of many tungstoenzymes have been obtained. Though specific and unspecific ABC transporter uptake systems have been described for tungstate and molybdate, only little is known about further discriminative steps in Moco and Wco biosynthesis. In bacteria producing Moco- and Wco-containing enzymes simultaneously, paralogous isoforms of the metal insertase MoeA may be specifically involved in the molybdenum- and tungsten-insertion into MPT, and in targeting Moco or Wco to their respective apo-enzymes. Wco-containing enzymes are of emerging biotechnological interest for a number of applications such as the biocatalytic reduction of CO2, carboxylic acids and aromatic compounds, or the conversion of acetylene to acetaldehyde. Full article
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