Uptake, Trapping, and Release of Organometallic Cations by Redox-Active Cationic Hosts

Uptake, Trapping, and Release of Organometallic Cations in Redox-Active Cationic Hosts

10.26434/chemrxiv.14778147.v1 ◽

2021 ◽

Author(s):

Iram F. Mansoor ◽

Kaitlyn Dutton ◽

Daniel A. Rothschild ◽

Richard C. Remsing ◽

Mark C. Lipke

Keyword(s):

Conformational Changes ◽

Electrostatic Interactions ◽

Dft Studies ◽

Redox Active ◽

Metal Organic ◽

Kinetic Effects ◽

Organometallic Cations ◽

Cation Complexes ◽

Uptake And Release ◽

Reduced State

The host-guest chemistry of metal-organic nanocages is typically driven by thermodynamically favorable interactions with their guests, such that uptake and release of guests can be controlled by switching affinity on/off. Herein, we achieve this effect by reducing porphyrin-walled cationic nanoprisms 1a12+ and 1b12+ to zwitterionic states that rapidly uptake organometallic cations Cp*2Co+ or Cp2Co+. Cp*2Co+ binds strongly (Ka = 1.3 x 103 M−1) in the neutral state 1a0 of host 1a12+, which has its three porphyrin walls doubly reduced and its six (bipy)Pt2+ linkers singly reduced. The less-reduced states of the host 1a3+ and 1a9+ also bind Cp*2Co+, though with lower affinities. The smaller Cp2Co+ cation binds strongly (Ka = 1.7 x 103 M-1) in the 3 e− reduced state 1b9+ of (tmeda)Pt2+ linked host 1b12+. Upon reoxidation of the hosts with Ag+, the guests become trapped to provide unprecedented metastable cation-in-cation complexes Cp*2Co+@1a12+ and Cp2Co+@1b12+ that persist for >1 month. Thus, dramatic kinetic effects reveal a way to confine the guests in thermodynamically unfavorable environments. Experimental and DFT studies indicate that PF6− anions kinetically stabilize Cp*2Co+@1a12+ through electrostatic interactions and by influencing conformational changes of the host that open and close its apertures. However, when Cp*2Co+@1a12+ was prepared using ferrocenium (Fc+) instead of Ag+ to reoxidize the host, dissociation was accelerated >200-fold even though neither Fc+ nor Fc have any competing affinity for 1a12+. This finding shows that metastable host-guest complexes can respond to subtler stimuli than are required to induce guest release from thermodynamically favorable complexes.

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Uptake, Trapping, and Release of Organometallic Cations in Redox-Active Cationic Hosts

10.26434/chemrxiv.14778147 ◽

2021 ◽

Author(s):

Iram F. Mansoor ◽

Kaitlyn Dutton ◽

Daniel A. Rothschild ◽

Richard C. Remsing ◽

Mark C. Lipke

Keyword(s):

Conformational Changes ◽

Electrostatic Interactions ◽

Dft Studies ◽

Redox Active ◽

Metal Organic ◽

Kinetic Effects ◽

Organometallic Cations ◽

Cation Complexes ◽

Uptake And Release ◽

Reduced State

The host-guest chemistry of metal-organic nanocages is typically driven by thermodynamically favorable interactions with their guests, such that uptake and release of guests can be controlled by switching affinity on/off. Herein, we achieve this effect by reducing porphyrin-walled cationic nanoprisms 1a12+ and 1b12+ to zwitterionic states that rapidly uptake organometallic cations Cp*2Co+ or Cp2Co+. Cp*2Co+ binds strongly (Ka = 1.3 x 103 M−1) in the neutral state 1a0 of host 1a12+, which has its three porphyrin walls doubly reduced and its six (bipy)Pt2+ linkers singly reduced. The less-reduced states of the host 1a3+ and 1a9+ also bind Cp*2Co+, though with lower affinities. The smaller Cp2Co+ cation binds strongly (Ka = 1.7 x 103 M-1) in the 3 e− reduced state 1b9+ of (tmeda)Pt2+ linked host 1b12+. Upon reoxidation of the hosts with Ag+, the guests become trapped to provide unprecedented metastable cation-in-cation complexes Cp*2Co+@1a12+ and Cp2Co+@1b12+ that persist for >1 month. Thus, dramatic kinetic effects reveal a way to confine the guests in thermodynamically unfavorable environments. Experimental and DFT studies indicate that PF6− anions kinetically stabilize Cp*2Co+@1a12+ through electrostatic interactions and by influencing conformational changes of the host that open and close its apertures. However, when Cp*2Co+@1a12+ was prepared using ferrocenium (Fc+) instead of Ag+ to reoxidize the host, dissociation was accelerated >200-fold even though neither Fc+ nor Fc have any competing affinity for 1a12+. This finding shows that metastable host-guest complexes can respond to subtler stimuli than are required to induce guest release from thermodynamically favorable complexes.

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Common modifications of selenocysteine in selenoproteins

Essays in Biochemistry ◽

10.1042/ebc20190051 ◽

2019 ◽

Vol 64 (1) ◽

pp. 45-53 ◽

Cited By ~ 1

Author(s):

Elias S.J. Arnér

Keyword(s):

Amino Acids ◽

Covalent Binding ◽

Physicochemical Characteristics ◽

Redox Active

Abstract Selenocysteine (Sec), the sulfur-to-selenium substituted variant of cysteine (Cys), is the defining entity of selenoproteins. These are naturally expressed in many diverse organisms and constitute a unique class of proteins. As a result of the physicochemical characteristics of selenium when compared with sulfur, Sec is typically more reactive than Cys while participating in similar reactions, and there are also some qualitative differences in the reactivities between the two amino acids. This minireview discusses the types of modifications of Sec in selenoproteins that have thus far been experimentally validated. These modifications include direct covalent binding through the Se atom of Sec to other chalcogen atoms (S, O and Se) as present in redox active molecular motifs, derivatization of Sec via the direct covalent binding to non-chalcogen elements (Ni, Mb, N, Au and C), and the loss of Se from Sec resulting in formation of dehydroalanine. To understand the nature of these Sec modifications is crucial for an understanding of selenoprotein reactivities in biological, physiological and pathophysiological contexts.

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SPECTRAL CHARACTERIZATION OF REDOX-ACTIVE PRUSSIAN BLUE ON METALLATED PLASMA POLYMER SURFACE MODIFIED CARBON ELECTRODES USING PHOTOTHERMAL DETECTION

Le Journal de Physique Colloques ◽

10.1051/jphyscol:1983645 ◽

1983 ◽

Vol 44 (C6) ◽

pp. C6-285-C6-290 ◽

Cited By ~ 3

Author(s):

J. W. Childers ◽

A. L. Crumbliss ◽

P. S. Lugg ◽

R. A. Palmer ◽

N. Morosoff ◽

...

Keyword(s):

Prussian Blue ◽

Polymer Surface ◽

Spectral Characterization ◽

Plasma Polymer ◽

Carbon Electrodes ◽

Redox Active ◽

Surface Modified

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On the Crystal Chemistry of Inorganic Nitrides: Crystal-Chemical Parameters and Opportunities in the Exploration of Their Compositional Space

10.26434/chemrxiv.11626974.v2 ◽

2020 ◽

Author(s):

Olivier Charles Gagné

Keyword(s):

Functional Properties ◽

A Priori ◽

Lone Pair ◽

Length Variation ◽

Electronic Effects ◽

Statistical Knowledge ◽

Redox Active ◽

Multiply Bonded ◽

Jahn Teller ◽

Compositional Space

The scarcity of nitrogen in Earth’s crust, combined with challenging synthesis, have made inorganic nitrides a relatively-unexplored class of compounds compared to their naturally-abundant oxide counterparts. To facilitate exploration of their compositional space via a priori modeling, and to help a posteriori structure verification not limited to inferring the oxidation state of redox-active cations, we derive a suite of bond-valence parameters and Lewis-acid strength values for 76 cations observed bonding to N3-, and further outline a baseline statistical knowledge of bond lengths for these compounds. We examine structural and electronic effects responsible for the functional properties and anomalous bonding behavior of inorganic nitrides, and identify promising venues for exploring uncharted compositional spaces beyond the reach of high-throughput computational methods. We find that many mechanisms of bond-length variation ubiquitous to oxide and oxysalt compounds (e.g., lone-pair stereoactivity, the Jahn-Teller and pseudo Jahn-Teller effects) are similarly pervasive in inorganic nitrides, and are occasionally observed to result in greater distortion magnitude than their oxide counterparts. We identify inorganic nitrides with multiply-bonded metal ions as a promising venue in heterogeneous catalysis, e.g. in the development of a post-Haber-Bosch process proceeding at milder reaction conditions, thus representing further opportunity in the thriving exploration of the functional properties of this emerging class of materials.

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Energetic Control of Redox-Active Polymers Towards Safe Organic Bioelectronic Materials

10.26434/chemrxiv.11366186.v1 ◽

2019 ◽

Author(s):

Alexander Giovannitti ◽

Reem B. Rashid ◽

Quentin Thiburce ◽

Bryan D. Paulsen ◽

Camila Cendra ◽

...

Keyword(s):

Molecular Oxygen ◽

Organic Semiconductors ◽

Side Reaction ◽

Semiconducting Polymers ◽

Side Reactions ◽

Redox Active ◽

Donor Acceptor ◽

Electrochemical Devices ◽

Biological Environment ◽

Device Operation

Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side‑products. This is particularly important for bioelectronic devices which are designed to operate in biological systems. While redox‑active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side‑reactions with molecular oxygen during device operation. We show that this electrochemical side reaction yields hydrogen peroxide (H2O2), a reactive side‑product, which may be harmful to the local biological environment and may also accelerate device degradation. We report a design strategy for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevent the formation of H2O2 during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte‑gated devices in application-relevant environments.

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Theoretical Exploration of 2,2’-Bipyridines as Electro-Active Compounds in Flow Batteries

10.26434/chemrxiv.7995935.v2 ◽

2019 ◽

Author(s):

Mariano Sánchez-Castellanos ◽

Martha M. Flores-Leonar ◽

Zaahel Mata-Pinzón ◽

Humberto G. Laguna ◽

Karl García-Ruiz ◽

...

Keyword(s):

Redox Potential ◽

Active Material ◽

Chemical Properties ◽

Small Subset ◽

Solubility In Water ◽

Protonation Reaction ◽

Redox Active ◽

Physico Chemical ◽

Pka Value ◽

Flow Batteries

Compounds from the 2,2’-bipyridine molecular family were investigated for use as redox-active materials in organic flow batteries. For 156 2,2’-bipyridine derivatives reported in the academic literature, we calculated the redox potential, the pKa for the first protonation reaction, and the solubility in aqueous solutions. Using experimental data on a small subset of derivatives, we were able to calibrate our calculations. We find that functionalization with electron-withdrawing groups leads to an increase of the redox potential and to an increase of the molecular acidity (as expressed in a reduction of the pKa value for the first protonation step). Furthermore, calculations of solubility in water indicate that some of the studied derivatives have adequate solubility for flow battery applications. Based on an analysis of the physico-chemical properties of the 156 studied compounds, we down-select five molecules with carbonyl- and nitro-based functional groups, whose parameters are especially promising for potential application as negative redox-active material inorganic flow batteries.

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Theoretical Exploration of 2,2’-Bipyridines as Electro-Active Compounds in Flow Batteries

10.26434/chemrxiv.7995935 ◽

2019 ◽

Author(s):

Mariano Sánchez-Castellanos ◽

Martha M. Flores-Leonar ◽

Zaahel Mata-Pinzón ◽

Humberto G. Laguna ◽

Karl García-Ruiz ◽

...

Keyword(s):

Redox Potential ◽

Active Material ◽

Chemical Properties ◽

Small Subset ◽

Solubility In Water ◽

Protonation Reaction ◽

Redox Active ◽

Physico Chemical ◽

Pka Value ◽

Flow Batteries

Compounds from the 2,2’-bipyridine molecular family were investigated for use as redox-active materials in organic flow batteries. For 156 2,2’-bipyridine derivatives reported in the academic literature, we calculated the redox potential, the pKa for the first protonation reaction, and the solubility in aqueous solutions. Using experimental data on a small subset of derivatives, we were able to calibrate our calculations. We find that functionalization with electron-withdrawing groups leads to an increase of the redox potential and to an increase of the molecular acidity (as expressed in a reduction of the pKa value for the first protonation step). Furthermore, calculations of solubility in water indicate that some of the studied derivatives have adequate solubility for flow battery applications. Based on an analysis of the physico-chemical properties of the 156 studied compounds, we down-select five molecules with carbonyl- and nitro-based functional groups, whose parameters are especially promising for potential application as negative redox-active material inorganic flow batteries.

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General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

10.26434/chemrxiv.7436795 ◽

2018 ◽

Author(s):

Marc Montesinos-Magraner ◽

Matteo Costantini ◽

Rodrigo Ramirez-Contreras ◽

Michael E. Muratore ◽

Magnus J. Johansson ◽

...

Keyword(s):

Total Synthesis ◽

Asymmetric Synthesis ◽

Chemical Space ◽

Synthetic Approach ◽

Asymmetric Cyclopropanation ◽

Redox Active ◽

Wide Range ◽

Leaving Group ◽

Stereoelectronic Properties ◽

Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons.

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Cambiarenes: Single-Step Synthesis and Anion Binding of a Clip- Shaped Macrocycle with a Redox-Active Core

10.26434/chemrxiv.9795005.v1 ◽

2019 ◽

Author(s):

Riley J. Petersen ◽

Brett J. Rozeboom ◽

Shalisa Oburn ◽

Nolan Blythe ◽

Tanner Rathje ◽

...

Keyword(s):

Electron Density ◽

Single Step ◽

Anion Binding ◽

Host Molecule ◽

Selective Binding ◽

The Core ◽

Redox Active ◽

Active Core ◽

Guest Binding

<div>We report the synthesis of a novel macrocyclic host molecule that forms in a single step from commercially available starting materials. The core of the macrocycle backbone possesses two quinone rings and, thus, is redox-active. Host-guest binding involving the clip-shaped cavity indicates selective binding of pyridine N-oxides based of the electron density of and steric bulk of the anionic oxygen.</div>

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