SwePub - search: WFRF:(Gupta Arvind Kumar)

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1.	2019 Journal article (peer-reviewed)
2.	Boniolo, Manuel, et al. (author) Electronic and geometric structure effects on one-electron oxidation of first-row transition metals in the same ligand framework 2021 In: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:2, s. 660-674 Journal article (peer-reviewed)abstract Developing new transition metal catalysts requires understanding of how both metal and ligand properties determine reactivity. Since metal complexes bearing ligands of the Py5 family (2,6-bis-[(2-pyridyl)methyl] pyridine) have been employed in many fields in the past 20 years, we set out here to understand their redox properties by studying a series of base metal ions (M = Mn, Fe, Co, and Ni) within the Py5OH (pyridine-2,6-diylbis[di-(pyridin-2-yl)methanol]) variant. Both reduced (M-II) and the one-electron oxidized (M-III) species were carefully characterized using a combination of X-ray crystallography, X-ray absorption spectroscopy, cyclic voltammetry, and density-functional theory calculations. The observed metal-ligand interactions and electrochemical properties do not always follow consistent trends along the periodic table. We demonstrate that this observation cannot be explained by only considering orbital and geometric relaxation, and that spin multiplicity changes needed to be included into the DFT calculations to reproduce and understand these trends. In addition, exchange reactions of the sixth ligand coordinated to the metal, were analysed. Finally, by including published data of the extensively characterised Py5OMe (pyridine-2,6-diylbis[di-(pyridin-2-yl)methoxymethane])complexes, the special characteristics of the less common Py5OH ligand were extracted. This comparison highlights the non-innocent effect of the distal OH functionalization on the geometry, and consequently on the electronic structure of the metal complexes. Together, this gives a complete analysis of metal and ligand degrees of freedom for these base metal complexes, while also providing general insights into how to control electrochemical processes of transition metal complexes.
3.	Chatterjee, Tulika, et al. (author) Type 1 diabetes, COVID-19 vaccines and short-term safety : Subgroup analysis from the global COVAD study 2024 In: Journal of Diabetes Investigation. - : John Wiley & Sons. - 2040-1116 .- 2040-1124. ; 15:1, s. 131-138 Journal article (peer-reviewed)abstract AIMS/INTRODUCTION: Coronavirus disease 2019 (COVID-19) vaccinations have been proven to be generally safe in healthy populations. However, the data on vaccine safety in patients with type 1 diabetes are scarce. This study aimed to evaluate the frequency and severity of short-term (<7-day) adverse vaccination events (AEs) and their risk factors among type 1 diabetes patients. MATERIALS AND METHODS: This study analyzed data from the COVID-19 vaccination in Autoimmune Diseases (COVAD) survey database (May to December 2021; 110 collaborators, 94 countries), comparing <7-day COVID-19 vaccine AE among type 1 diabetes patients and healthy controls (HCs). Descriptive statistics; propensity score matching (1:4) using the variables age, sex and ethnicity; and multivariate analyses were carried out.RESULTS: This study analyzed 5,480 completed survey responses. Of all responses, 5,408 were HCs, 72 were type 1 diabetes patients (43 females, 48.0% white European ancestry) and Pfizer was the most administered vaccine (39%). A total of 4,052 (73.9%) respondents had received two vaccine doses. Patients with type 1 diabetes had a comparable risk of injection site pain, minor and major vaccine AEs, as well as associated hospitalizations to HCs. However, type 1 diabetes patients had a higher risk of severe rashes (3% vs 0.4%, OR 8.0, 95% confidence interval 1.7-36), P = 0.007), although reassuringly, these were rare (n = 2 among type 1 diabetes patients).CONCLUSIONS: COVID-19 vaccination was safe and well tolerated in patients with type 1 diabetes with similar AE profiles compared with HCs, although severe rashes were more common in type 1 diabetes patients.
4.	D'Imperio, Nicolas, et al. (author) Highly Conjugated Bis(benzo[b]phosphole)-P-oxides : Synthesis and Electrochemical, Optical, and Computational Studies 2023 In: European Journal of Organic Chemistry. - : John Wiley & Sons. - 1434-193X .- 1099-0690. ; 26:4 Journal article (peer-reviewed)abstract The first examples of a pi-conjugated benzo[b]phosphole P-oxide in which two phosphole P-oxide units are connected by a carbon-carbon double bond are described. The molecules are synthesized as E isomers with respect to the carbon-carbon double bond and exist as stable cis and trans isomers (chiral and meso one respectively) relatively to the two stereogenic P atoms. The optical and electrochemical properties of both isomers have been investigated by experiment and computations.
5.	Green, Joshua P., et al. (author) Effect of Arsenic Coordination State on the Structure, Aromaticity, and Optical Properties of Dithieno[3,2-b:2 ',3 '-d]arsoles 2019 In: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :11-12, s. 1539-1543 Journal article (peer-reviewed)abstract A silylated derivative of 4-phenyl-dithieno[3,2-b:2 ',3 '-d]arsole (DTAs) was synthesized, and the effect of coordinating of DTAs compounds to Pd on their structural and optical properties was investigated. Coordination of the As to Pd was found to increase the structural aromaticity of the ring system as measured by the harmonic oscillator measure of heterocyclic electron delocalization (HOMHED), and the pyramidalization of the As atoms was also found to show a good correlation with the HOMHED values. However, coordination had a more subtle impact on the optical properties than seen for phosphorus-containing analogues as the metal-ligand interactions were weaker.
6.	Green, Joshua P., et al. (author) Golden Age of Fluorenylidene Phosphaalkenes-Synthesis, Structures, and Optical Properties of Heteroaromatic Derivatives and Their Gold Complexes 2020 In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 85:22, s. 14619-14626 Journal article (peer-reviewed)abstract The substitution of 2,7-dibromo-9-fluorenyl phosphaalkenes with heteroaromatic substituents (bithiophene, benzothiophene, pyridine) offers access to interesting push-pull dye molecules. Steric shielding due to the bulky P-substituent gives marked different reactivities at the 2- and 7-positions, allowing the synthesis of mixed/asymmetric derivatives. Further functionalization via gold(I) coordination was demonstrated and increased the acceptor character, concomitant with a red-shifted absorption.
7.	Gupta, Arvind Kumar, et al. (author) Alkynyl Coinage Metal Clusters and Complexes-Syntheses, Structures, and Strategies 2018 In: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 24:30, s. 7536- Journal article (peer-reviewed)abstract In this Concept we discuss how the chemistry of coinage metal complexes based on alkynyl ligands has developed over the past decades. The rich coordination of alkynyl, that exhibit both (1) (end-on) and (2) (side on) modes, includes non-bridged systems, as well as bridging of up to four (or six) metal centres. Resulting metal clusters often exhibit highly regular structures and typical coordination motifs forming fascinating assemblies exploiting this versatile coordination. Metallophilic interactions are often an important driving force for the formation of large clusters. In addition, the use of co-ligands as well the possibility to encapsulate counter ions greatly increases the chemical and structural diversity. Herein we attempt to summarize and highlight design principles towards multinuclear homo and hetero-bi-metallic coinage metal clusters of alkynyl ligands.
8.	Gupta, Arvind Kumar, et al. (author) Facile synthesis of silver alkynide cluster and coordination polymers using picolinic acid as a co-ligand 2019 In: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 48:44, s. 16518-16524 Journal article (peer-reviewed)abstract We describe five 1D-coordination polymers and two discrete silver clusters consisting of alkynides and picolinic carboxylates as co-ligands. In some cases, DMSO or EtOH further solvated the structural motifs. Utilising the sterically demanding tri-isopropylsilyl acetylene afforded a tridecanuclear cluster that possessed an unprecedented core with a silver center surrounded by six octahedrally arranged silver atoms.
9.	Gupta, Arvind Kumar, et al. (author) Rearrangement and redistribution reaction of Ph2PCH2TMS with PhAsCl2 or AsCl3 2019 In: Phosphorus Sulfur and Silicon and the Related Elements. - : TAYLOR & FRANCIS LTD. - 1042-6507 .- 1563-5325. ; 194:10, s. 967-971 Journal article (peer-reviewed)abstract The attempted synthesis of bis(diphenylphosphinomethyl) phenylarsane and tris(diphenylphosphinomethyl) arsane through condensation of chloro arsanes and diphenyl (trimethylsilylmethyl) phosphane yielded a number of side products originating from migratory and redox-reactions in addition to the targeted ligands. An unexpected, 1,3,4-phosphadiarssolan-1-ium salt was obtained and crystallographically characterized as an A-shaped chlorido adduct. [GRAPHICS] .
10.	Gupta, Arvind Kumar, et al. (author) Rich Coordination Chemistry of pi-Acceptor Dibenzoarsole Ligands 2017 In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:8, s. 4504-4511 Journal article (peer-reviewed)abstract A series of dibenzoarsole (also known as 9-arsafluorene) derivatives have been prepared, and their coordination chemistry has been investigated. The different ligand topology and the arsenic substituents govern the reactivity of the ligands. We report various crystal structures of palladium and platinum complexes derived from this family of ligands. The biphenyl backbone of the bridged bidentate ligands allows very flexible coordination. We have also studied the application of an allylic Pd complex in nucleophilic substitution reactions, revealing that the benzoarsole substituent is susceptible to metal insertion.
11.	Gupta, Arvind Kumar, et al. (author) Serendipitous and Targeted Synthesis of High Nuclearity Clusters : Carbonate and Oxalate Encapsulating Silver Alkynides 2020 In: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 20:7, s. 4232-4237 Journal article (peer-reviewed)abstract Silver coordination compounds of the [Ag3L2] (where L = Bu-t-C=C) family having perchlorate counterions exhibit template-driven self-assembly of the common square pyramidal building block. This behavior is similar to previously described observations; however, important differences arise from counterion-silver interactions. Penta- and hexameric clusters encapsulating chloride and oxalate, respectively, were crystallographically characterized. A high nuclearity cluster [(CO3)(3)(H2O)subset of Ag38L20](12+) was formed upon extended exposure to an ambient atmosphere by trapping three carbonates and one water molecule.
12.	Gupta, Arvind Kumar, et al. (author) Solvent and Counter-Ion Induced Coordination Environment Changes Towards Ag-I Coordination Polymers 2019 In: European Journal of Inorganic Chemistry. - : WILEY-V C H VERLAG GMBH. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2019:33, s. 3740-3744 Journal article (peer-reviewed)abstract A series of silver coordination polymers based on the 9,9 '-bis(4,5-diazafluorene) (BDF-H-2) ligand is presented. The choice of counterions and reaction conditions dictate the observed topology on the final systems by influencing the silver coordination environment. Coordination modes, flexibility of the ligand and extended pi-pi stacking interactions have allowed the preparation and crystallographic characterisation of one 1D- and three 2D-coordination polymers: 1D-[Ag(BDF-H-2)(DMSO)](n)(X)(n) (where X = OTf- and ClO4-); 1D-[Ag-2(BDF-H-2) m(1)-(TfO)(2),m(2)-(TfO)(2)](n)(TfO)(n), and 2D-[Ag-2(BDF-H-2)(3)](n)(PF6)(2n).
13.	Gupta, Arvind Kumar, et al. (author) The Self-Assembly of [{Ag-3(C (CBu)-Bu-t)(2)}(n)](n+) Building Units into a Template-Free Cuboctahedron and Anion-Encapsulating Silver Cages 2019 In: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 58:23, s. 16236-16240 Journal article (peer-reviewed)abstract We describe the controlled synthesis of silver acetylide clusters based on a simple polymeric [Ag3L2](+) (L = -C (CBu)-Bu-t) building block. A linear one-dimensional polymeric structure shows alternating pyramidal motifs and is the basic repeating unit forming discrete molecular cages (pentamers [X subset of Ag15L10](4+) and hexamers [PF6 subset of Ag18L12](5+)) obtained by incorporating suitable templates. These motifs and a rare template-free cuboctahedral [Ag12L8](4+) cluster (tetramer) were crystallographically characterized.
14.	Johnson, Catherine, et al. (author) Ferrous and ferric complexes with cyclometalating N-heterocyclic carbene ligands : a case of dual emission revisited 2023 In: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 14:37, s. 10129-10139 Journal article (peer-reviewed)abstract Iron N-heterocyclic carbene (FeNHC) complexes with long-lived charge transfer states are emerging as a promising class of photoactive materials. We have synthesized [Fe-II(ImP)(2)] (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)) that combines carbene ligands with cyclometalation for additionally improved ligand field strength. The 9 ps lifetime of its (MLCT)-M-3 (metal-to-ligand charge transfer) state however reveals no benefit from cyclometalation compared to Fe(II) complexes with NHC/pyridine or pure NHC ligand sets. In acetonitrile solution, the Fe(II) complex forms a photoproduct that features emission characteristics (450 nm, 5.1 ns) that were previously attributed to a higher ((MLCT)-M-2) state of its Fe(III) analogue [Fe-III(ImP)(2)](+), which led to a claim of dual (MLCT and LMCT) emission. Revisiting the photophysics of [Fe-III(ImP)(2)](+), we confirmed however that higher ((MLCT)-M-2) states of [Fe-III(ImP)(2)](+) are short-lived (<10 ps) and therefore, in contrast to the previous interpretation, cannot give rise to emission on the nanosecond timescale. Accordingly, pristine [Fe-III(ImP)(2)](+) prepared by us only shows red emission from its lower (LMCT)-L-2 state (740 nm, 240 ps). The long-lived, higher energy emission previously reported for [Fe-III(ImP)(2)](+) is instead attributed to an impurity, most probably a photoproduct of the Fe(II) precursor. The previously reported emission quenching on the nanosecond time scale hence does not support any excited state reactivity of [Fe-III(ImP)(2)](+) itself.
15.	Kisner, Alexandre, et al. (author) Electrophysiological properties and projections of lateral hypothalamic parvalbumin positive neurons 2018 In: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 13:6 Journal article (peer-reviewed)abstract Cracking the cytoarchitectural organization, activity patterns, and neurotransmitter nature of genetically-distinct cell types in the lateral hypothalamus (LH) is fundamental to develop a mechanistic understanding of how activity dynamics within this brain region are generated and operate together through synaptic connections to regulate circuit function. However, the precise mechanisms through which LH circuits orchestrate such dynamics have remained elusive due to the heterogeneity of the intermingled and functionally distinct cell types in this brain region. Here we reveal that a cell type in the mouse LH identified by the expression of the calcium-binding protein parvalbumin (PVALB; LHPV) is fast-spiking, releases the excitatory neurotransmitter glutamate, and sends long range projections throughout the brain. Thus, our findings challenge long-standing concepts that define neurons with a fast-spiking phenotype as exclusively GABAergic. Furthermore, we provide for the first time a detailed characterization of the electrophysiological properties of these neurons. Our work identifies LHPV neurons as a novel functional component within the LH glutamatergic circuitry.
16.	Lindh, Linnea, et al. (author) Dye-sensitized solar cells based on Fe N-heterocyclic carbene photosensitizers with improved rod-like push-pull functionality 2021 In: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 12:48, s. 16035-16053 Journal article (peer-reviewed)abstract A new generation of octahedral iron(ii)-N-heterocyclic carbene (NHC) complexes, employing different tridentate C^N^C ligands, has been designed and synthesized as earth-abundant photosensitizers for dye sensitized solar cells (DSSCs) and related solar energy conversion applications. This work introduces a linearly aligned push-pull design principle that reaches from the ligand having nitrogen-based electron donors, over the Fe(ii) centre, to the ligand having an electron withdrawing carboxylic acid anchor group. A combination of spectroscopy, electrochemistry, and quantum chemical calculations demonstrate the improved molecular excited state properties in terms of a broader absorption spectrum compared to the reference complex, as well as directional charge-transfer displacement of the lowest excited state towards the semiconductor substrate in accordance with the push-pull design. Prototype DSSCs based on one of the new Fe NHC photosensitizers demonstrate a power conversion efficiency exceeding 1% already for a basic DSSC set-up using only the I−/I3−redox mediator and standard operating conditions, outcompeting the corresponding DSSC based on the homoleptic reference complex. Transient photovoltage measurements confirmed that adding the co-sensitizer chenodeoxycholic acid helped in improving the efficiency by increasing the electron lifetime in TiO2. Time-resolved spectroscopy revealed spectral signatures for successful ultrafast (<100 fs) interfacial electron injection from the heteroleptic dyes to TiO2. However, an ultrafast recombination process results in undesirable fast charge recombination from TiO2back to the oxidized dye, leaving only 5-10% of the initially excited dyes available to contribute to a current in the DSSC. On slower timescales, time-resolved spectroscopy also found that the recombination dynamics (longer than 40 μs) were significantly slower than the regeneration of the oxidized dye by the redox mediator (6-8 μs). Therefore it is the ultrafast recombination down to fs-timescales, between the oxidized dye and the injected electron, that remains as one of the main bottlenecks to be targeted for achieving further improved solar energy conversion efficiencies in future work.
17.	Maeda, Gasper, et al. (author) Oxygenated Cyclohexene Derivatives and Other Constituents from the Roots of Monanthotaxis trichocarpa. 2020 In: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 83:2, s. 210-215 Journal article (peer-reviewed)abstract Three new oxygenated cyclohexene derivatives, trichocarpeols A (1), B (2), and C (3), along with nine known secondary metabolites, were isolated from the methanolic root extract of Monanthotaxis trichocarpa. They were identified by NMR spectroscopic and mass spectrometric analyses, and the structure of trichocarpeol A (1) was confirmed by single-crystal X-ray diffraction. Out of the 12 isolated natural products, uvaretin (4) showed activity against the Gram-positive bacterium Bacillus subtilis with a MIC value of 18 μM. None of the isolated metabolites was active against the Gram-negative Escherichia coli at a ∼5 mM (2000 μg/mL) concentration. Whereas 4 showed cytotoxicity at EC50 10.2 μM against the MCF-7 human breast cancer cell line, the other compounds were inactive or not tested.
18.	Maeda, Gasper, et al. (author) Oxygenated Cyclohexene Derivatives from the Stem and Root Barks of Uvaria pandensis 2021 In: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 84:12, s. 3080-3089 Journal article (peer-reviewed)abstract Five new cyclohexene derivatives, dipandensin A and B (1 and 2) and pandensenols A-C (3-5), and 16 known secondary metabolites (6-21) were isolated from the methanol-soluble extracts of the stem and root barks of Uvaria pandensis. The structures were characterized by NMR spectroscopic and mass spectrometric analyses, and that of 6-methoxyzeylenol (6) was further confirmed by single-crystal X-ray crystallography, which also established its absolute configuration. The isolated metabolites were evaluated for antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus epidermidis and the Gram-negative bacteria Enterococcus raffinosus, Escherichia coli, Paraburkholderia caledonica, Pectobacterium carotovorum, and Pseudomonas putida, as well as for cytotoxicity against the MCF-7 human breast cancer cell line. A mixture of uvaretin (20) and isouvaretin (21) exhibited significant antibacterial activity against B. subtilis (EC50 8.7 μM) and S. epidermidis (IC50 7.9 μM). (8'α,9'β-Dihydroxy)-3-farnesylindole (12) showed strong inhibitory activity (EC50 9.8 μM) against B. subtilis, comparable to the clinical reference ampicillin (EC50 17.9 μM). None of the compounds showed relevant cytotoxicity against the MCF-7 human breast cancer cell line.
19.	Mai, Juri, et al. (author) Reductive coupling of two aldehydes to unsymmetrical E-alkenes via phosphaalkene and phosphinate intermediates 2018 In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 54:52, s. 7163-7166 Journal article (peer-reviewed)abstract Stilbenes with push-pull electronics are directly accessible from an electron-rich and an electron-deficient benzaldehyde in a novel reductive aldehyde cross-coupling reaction. The one-pot procedure is enabled by the oxidation of a transient phosphinite to the corresponding phosphinate which exhibits sufficient reactivity towards deactivated aldehydes.
20.	Morales Salazar, Daniel, et al. (author) Reactivity studies of an imine-functionalised phosphaalkene; unusual electrostatic and supramolecular stabilisation of a σ2λ3-phosphorus motif via hydrogen bonding 2018 In: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 47, s. 10404-10409 Journal article (peer-reviewed)abstract A PC heavy-alkene analogue that is unreactive towards the addition of strong acids on its double-bond is presented; instead, a strategically located imine nitrogen on the periphery forms protonated adducts displaying hydrogen bonding interactions. These materials are significantly more stable than the parent species, demonstrating an unprecedented approach towards the stabilisation of a multiple-bonded heavy main group fragment, in this case, a phosphaalkene. An HCl adduct self-assembles with H2O into a dimeric network displaying a discrete quadrilateral hydrogen-bonded arrangement.
21.	Prakash, Om, et al. (author) How Rigidity and Conjugation of Bidentate Ligands Affect the Geometry and Photophysics of Iron N-Heterocyclic Complexes : A Comparative Study 2024 In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 63:10, s. 4461-4473 Journal article (peer-reviewed)abstract Two iron complexes featuring the bidentate, nonconjugated N-heterocyclic carbene (NHC) 1,1′-methylenebis(3-methylimidazol-2-ylidene) (mbmi) ligand, where the two NHC moieties are separated by a methylene bridge, have been synthesized to exploit the combined influence of geometric and electronic effects on the ground- and excited-state properties of homoleptic FeIII-hexa-NHC [Fe(mbmi)3](PF6)3 and heteroleptic FeII-tetra-NHC [Fe(mbmi)2(bpy)](PF6)2 (bpy = 2,2′-bipyridine) complexes. They are compared to the reported FeIII-hexa-NHC [Fe(btz)3](PF6)3 and FeII-tetra-NHC [Fe(btz)2(bpy)](PF6)2 complexes containing the conjugated, bidentate mesoionic NHC ligand 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene) (btz). The observed geometries of [Fe(mbmi)3](PF6)3 and [Fe(mbmi)2(bpy)](PF6)2 are evaluated through L-Fe-L bond angles and ligand planarity and compared to those of [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The FeII/FeIII redox couples of [Fe(mbmi)3](PF6)3 (−0.38 V) and [Fe(mbmi)2(bpy)](PF6)2 (−0.057 V, both vs Fc+/0) are less reducing than [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The two complexes show intense absorption bands in the visible region: [Fe(mbmi)3](PF6)3 at 502 nm (ligand-to-metal charge transfer, 2LMCT) and [Fe(mbmi)2(bpy)](PF6)2 at 410 and 616 nm (metal-to-ligand charge transfer, 3MLCT). Lifetimes of 57.3 ps (2LMCT) for [Fe(mbmi)3](PF6)3 and 7.6 ps (3MLCT) for [Fe(mbmi)2(bpy)](PF6)2 were probed and are somewhat shorter than those for [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. [Fe(mbmi)3](PF6)3 exhibits photoluminescence at 686 nm (2LMCT) in acetonitrile at room temperature with a quantum yield of (1.2 ± 0.1) × 10-4, compared to (3 ± 0.5)
22.	Prakash, Om, et al. (author) Photophysical Integrity of the Iron(III) Scorpionate Framework in Iron(III)-NHC Complexes with Long-Lived 2LMCT Excited States 2022 In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:44, s. 17515-17526 Journal article (peer-reviewed)abstract Fe(III) complexes with N-heterocyclic carbene (NHC) ligands belong to the rare examples of Earth-abundant transition metal complexes with long-lived luminescent charge-transfer excited states that enable applications as photosensitizers for charge separation reactions. We report three new hexa-NHC complexes of this class: [Fe(brphtmeimb)2]PF6 (brphtmeimb = [(4-bromophenyl)tris(3-methylimidazol-2-ylidene)borate]–, [Fe(meophtmeimb)2]PF6 (meophtmeimb = [(4-methoxyphenyl)tris(3-methylimidazol-2-ylidene)borate]–, and [Fe(coohphtmeimb)2]PF6 (coohphtmeimb = [(4-carboxyphenyl)tris(3-methylimidazol-2-ylidene)borate]–. These were derived from the parent complex [Fe(phtmeimb)2]PF6 (phtmeimb = [phenyltris(3-methylimidazol-2-ylidene)borate]– by modification with electron-withdrawing and electron-donating substituents, respectively, at the 4-phenyl position of the ligand framework. All three Fe(III) hexa-NHC complexes were characterized by NMR spectroscopy, high-resolution mass spectroscopy, elemental analysis, single crystal X-ray diffraction analysis, electrochemistry, Mößbauer spectroscopy, electronic spectroscopy, magnetic susceptibility measurements, and quantum chemical calculations. Their ligand-to-metal charge-transfer (2LMCT) excited states feature nanosecond lifetimes (1.6–1.7 ns) and sizable emission quantum yields (1.7–1.9%) through spin-allowed transition to the doublet ground state (2GS), completely in line with the parent complex [Fe(phtmeimb)2]PF6 (2.0 ns and 2.1%). The integrity of the favorable excited state characteristics upon substitution of the ligand framework demonstrates the robustness of the scorpionate motif that tolerates modifications in the 4-phenyl position for applications such as the attachment in molecular or hybrid assemblies.
23.	Prakash, Om, et al. (author) Tailoring the Photophysical Properties of a Homoleptic Iron(II) Tetra N-Heterocyclic Carbene Complex by Attaching an Imidazolium Group to the (C∧N∧C) Pincer Ligand─A Comparative Study 2024 In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 63:6, s. 2909-2918 Journal article (peer-reviewed)abstract We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)2](PF6)4 (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)2](PF6)2 (pbmi = (pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) as well as a stronger MLCT absorption band extending more toward the red spectral region. However, compared to the carboxylic acid derivative [Fe(cpbmi)2](PF6)2 (cpbmi = 1,1′-(4-carboxypyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)), the excited-state lifetime of [Fe(miHpbmi)2](PF6)4 is the same, but both the extinction and the red shift are more pronounced for the former. Hence, this makes [Fe(miHpbmi)2](PF6)4 a promising pH-insensitive analogue of [Fe(cpbmi)2](PF6)2. Finally, the excited-state dynamics of the title compound [Fe(miHpbmi)2](PF6)4 was investigated in solvents with different viscosities, however, showing very little dependency of the depopulation of the excited states on the properties of the solvent used.
24.	Queyriaux, Nicolas, et al. (author) Electrochemical, Spectroscopic, and Computational Investigation of a Series of Polypyridyl Ruthenium(II) Complexes : Characterization of Reduced States 2021 In: European Journal of Inorganic Chemistry. - : John Wiley & Sons. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2021:13, s. 1263-1270 Journal article (peer-reviewed)abstract A series of polypyridyl ruthenium(II) complexes has been synthesized and characterized by H-1-NMR, electronic absorption and voltammetric techniques. Among this series, hexafluorophosphate salts of eight ruthenium(II) complexes were newly prepared. Due to the well-known ability of this class of compounds to assist electro- and photocatalytic reductive processes (such as the reduction of CO2, H+ and NAD(P)(+) models), particular attention has been paid to investigate the nature of their one- and two-electron reduced species through computational and spectroscopic techniques.
25.	Reiersolmoen, A. C., et al. (author) Catalytic Activity of trans-Bis(pyridine)gold Complexes 2020 In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:13, s. 6439-6446 Journal article (peer-reviewed)abstract Gold catalysis has become one of the fastest growing fields in chemistry, providing new organic transformations and offering excellent chemoselectivities under mild reaction conditions. Methodological developments have been driven by wide applicability in the synthesis of complex structures, whereas the mechanistic understanding of Au(III)-mediated processes remains scanty and have become the Achilles' heel of methodology development. Herein, the systematic investigation of the reactivity of bis(pyridine)-ligated Au(III) complexes is presented, based on NMR spectroscopic, X-ray crystallographic, and DFT data. The electron density of pyridines modulates the catalytic activity of Au(III) complexes in propargyl ester cyclopropanation of styrene. To avoid strain induced by a ligand with a nonoptimal nitrogen-nitrogen distance, bidentate bis(pyridine)-Au(III) complexes convert into dimers. For the first time, bis(pyridine)Au(I) complexes are shown to be catalytically active, with their reactivity being modulated by strain.
26.	Reiersolmoen, Ann Christin, et al. (author) Symmetry of three-center, four-electron bonds 2020 In: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 11:30, s. 7979-7990 Journal article (peer-reviewed)abstract Three-center, four-electron bonds provide unusually strong interactions; however, their nature remains ununderstood. Investigations of the strength, symmetry and the covalentversuselectrostatic character of three-center hydrogen bonds have vastly contributed to the understanding of chemical bonding, whereas the assessments of the analogous three-center halogen, chalcogen, tetrel and metallic & xe111;-type long bonding are still lagging behind. Herein, we disclose the X-ray crystallographic, NMR spectroscopic and computational investigation of three-center, four-electron [D-X-D](+)bonding for a variety of cations (X+= H+, Li+, Na+, F+, Cl+, Br+, I+, Ag(+)and Au+) using a benchmark bidentate model system. Formation of a three-center bond, [D-X-D](+)is accompanied by an at least 30% shortening of the D-X bonds. We introduce a numerical index that correlates symmetry to the ionic size and the electron affinity of the central cation, X+. Providing an improved understanding of the fundamental factors determining bond symmetry on a comprehensive level is expected to facilitate future developments and applications of secondary bonding and hypervalent chemistry.
27.	Roy, Souvik, et al. (author) Electrocatalytic Hydrogen Evolution from a Cobaloxime-Based Metal-Organic Framework Thin Film 2019 In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 141:40, s. 15942-15950 Journal article (peer-reviewed)abstract Molecular hydrogen evolution catalysts (HECs) are synthetically tunable and often exhibit high activity, but they are also hampered by stability concerns and practical limitations associated with their use in the homogeneous phase. Their incorporation as integral linker units in metal-organic frameworks (MOFs) can remedy these shortcomings. Moreover, the extended three-dimensional structure of MOFs gives rise to high catalyst loadings per geometric surface area. Herein, we report a new MOF that exclusively consists of cobaloximes, a widely studied HEC, that act as metallo-linkers between hexanuclear zirconium clusters. When grown on conducting substrates and under applied reductive potential, the cobaloxime linkers promote electron transport through the film as well as function as molecular HECs. The obtained turnover numbers are orders of magnitude higher than those of any other comparable cobaloxime system, and the molecular integrity of the cobaloxime catalysts is maintained for at least 18 h of electrocatalysis. Being one of the very few hydrogen evolving electrocatalytic MOFs based on a redox-active metallo-linker, this work explores uncharted terrain for greater catalyst pathways.
28.	Shameem, Muhammad Anwar, et al. (author) 1-Phospha-Butadienes and 1H-Phospholes via Alkynylation of Acetylenic Phosphaalkenes 2023 In: ChemPlusChem. - : Wiley-Blackwell. - 2192-6506. ; 88:4 Journal article (peer-reviewed)abstract Carbon-rich motifs are important building blocks for the fabrication of functional and opto-electronic materials. Electronic tuning can be achieved by alteration of bonding topologies but also via incorporation of heteroelements, for example phosphorus. Herein we present the palladium/copper mediated formation of branched 1-phospha-butadiene derivatives through an unusual alkynylation of a phospha-enyne fragment. Structural and NMR studies provide mechanistic insights into this alkynylation. Furthermore, we disclose a complex cyclisation of the thus obtained 3-yne-1-phosphabutadiene motifs to give highly substituted phosphole derivatives identified by 2D NMR and SC-XRD analysis.
29.	Shameem, Muhammad Anwar, et al. (author) One, Two Three : Phosphaalkene Decoration Tailoring Solubility and Electronic Properties of Truxene-Based Electron Acceptors 2023 In: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765. ; 29:32 Journal article (peer-reviewed)abstract We report the functionalization and deplanarization of truxenes using pnictaalkene fragments. Selective introduction of one, two, or three Mes-Pn fragments provides up to three fully reversible reductions based on the Pn=C fragments. The incorporation of the unsaturated heteroelement fragment as well as the contortion of the truxene core result in significantly red-shifted absorption spectra and interesting opto-electronic properties which are studied by electrochemistry and spectro-electrochemistry. Incorporation of arsaalkene (As=C) motifs gives significantly milder reduction potentials and red-shifted absorption, while phosphaalkene decorated truxene P3 can be functionalized using Au(I)Cl coordination. Furthermore, solubility is markedly increased upon incorporation of the Pn-Mes fragments which renders these materials suitable for solution processing.
30.	Umereweneza, Daniel, et al. (author) Antibacterial and cytotoxic prenylated dihydrochalcones from Eriosema montanum 2021 In: Fitoterapia (Milano). - : Elsevier BV. - 0367-326X .- 1873-6971. ; 149 Journal article (peer-reviewed)abstract Two new prenylated dihydrochalcones (1,2) and eighteen known secondary metabolites (3−20) were isolated from the CH2Cl2-MeOH (1:1) extracts of the roots, the stem bark and the leaves of Eriosema montanum Baker f. (Leguminosae). The structures of the isolated compounds were characterized by NMR, IR, and UV spectroscopic and mass spectrometric analyses. The structures of compounds 5, 10, 11 and 13 were confirmed by single crystal X-ray diffraction. The antibacterial activity of the crude extracts and the isolated constituents were established against Gram-positive and Gram-negative bacteria. Among the tested compounds, 1–4 and 10 showed strong activity against the Gram-positive bacterium Bacillus subtilis with minimum inhibitory concentration (MIC) ranging from 3.1 to 8.9 μM, as did the leaf crude extract with an MIC of 3.0 μg/mL. None of the crude extracts nor the isolated compounds were active against Escherichia coli. Compounds 1, 3 and 4 showed higher cytotoxicity, evaluated against the human breast cancer cell line MCF-7, with EC50 of 7.0, 18.0 and 18.0 μM, respectively. These findings contribute to the phytochemical understanding of the genus Eriosema, and highlight the pharmaceutical potential of prenylated dihydrochalcones.
31.	Vanderkooy, Alan, et al. (author) Halogen Bonding Helicates Encompassing Iodonium Cations 2019 In: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 58:27, s. 9012-9016 Journal article (peer-reviewed)abstract The first halonium-ion-based helices were designed and synthesized using oligo-aryl/pyridylene-ethynylene backbones that fold around reactive iodonium ions. Halogen bonding interactions stabilize the iodonium ions within the helices. Remarkably, the distance between two iodonium ions within a helix is shorter than the sum of their van der Waals radii. The helical conformations were characterized by X-ray crystallography in the solid state, by NMR spectroscopy in solution and corroborated by DFT calculations. The helical complexes possess potential synthetic utility, as demonstrated by their ability to induce iodocyclization of 4-penten-1-ol.
32.	Wells, Jordann A. L., et al. (author) Core and double bond functionalisation of cyclopentadithiophene-phosphaalkenes 2020 In: Inorganic Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1545 .- 2052-1553. ; 7:21, s. 4052-4061 Journal article (peer-reviewed)abstract The heterofulvenoid cyclopentadithiophene-phosphaalkene is a versatile building block for opto-electronic tuning with donor and acceptor moieties. Both the annulated thienyl rings and the phosphaalkene bond can be functionalised using a variety of chemical transformations, e.g. forming C-C, C-E (E=Si, Br) bonds, or oxidation and metal coordination, respectively. Solid-state structures, optical and electronic properties are probed theoretically and experimentally, illustrating the opto-electronic tailoring opportunities at this motif.

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