Mois : juillet 2020

Degeneracy of the Antithrombin Binding Sequence in Heparin: 2‐O‐Sulfated Iduronic Acid Can Replace the Critical Glucuronic Acid

Degeneracy of the Antithrombin Binding Sequence in Heparin: 2‐O‐Sulfated Iduronic Acid Can Replace the Critical Glucuronic Acid

An alternative fit : Octasaccharide (OCTA) in unbound form (figure top) and in complex with antithrombin (bottom, top and side views) is presented. OCTA includes the active GlcNS,6S‐IdoA2S ‐GlcNS,3S,6S‐IdoA2S‐GlcNS,6S sequence as an alternative to the canonical GlcNAc/NS,6S‐GlcA ‐GlcNS,3S,6S‐IdoA2S‐GlcNS,6S AT‐binding pentasaccharide. ‘Induced fit’ conformational change of the glycosidic backbone and the two IdoA2S moieties surrounding the central 3‐O‐sulfo‐glucosamine are detected.

Abstract

Heparin binds to and activates antithrombin (AT) through a specific pentasaccharide sequence, in which a trisaccharide subsite, containing glucuronic acid (GlcA), has been considered as the initiator in the recognition of the polysaccharide by the protein. Recently it was suggested that sulfated iduronic acid (IdoA2S) could replace this “canonical” GlcA. Indeed, a heparin octasaccharidic sequence obtained by chemoenzymatic synthesis, in which GlcA is replaced with IdoA2S, has been found to similarly bind to and activate antithrombin. By using saturation‐transfer‐difference (STD) NMR, NOEs, transferred NOEs (tr‐NOEs) NMR and molecular dynamics, we show that, upon binding to AT, this IdoA2S unit develops comparable interactions with AT as GlcA. Interestingly, two IdoA2S units, both present in a 1C42S0 equilibrium in the unbound saccharide, shift to full 2S0 and full 1C4 upon binding to antithrombin, providing the best illustration of the critical role of iduronic acid conformational flexibility in biological systems.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Stefano Elli, Eduardo Stancanelli, Zhangjie Wang, Maurice Petitou, Jian Liu, Marco Guerrini
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001346

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Synthesis and Characterization of Anionic Poly(cyclopentadienylene vinylene) and Its Use in Conductive Hydrogels

Synthesis and Characterization of Anionic Poly(cyclopentadienylene vinylene) and Its Use in Conductive Hydrogels

Conductive and water soluble : A new π‐conjugated polyelectrolyte is synthesized from an insulating hydrophobic precursor made via ring‐opening metathesis polymerization. Anionic poly(cyclopentadienylene vinylene) can be made with a variety of side chains, is conductive and non‐toxic, and can easily be formulated into conductive hydrogels due to its high water‐solubility.

Abstract

The use of π‐conjugated polymers (CPs) in conductive hydrogels remains challenging due to the water‐insoluble nature of most CPs. Conjugated polyelectrolytes (CPEs) are promising alternatives because they have tunable electronic properties and high water‐solubility, but they are often difficult to synthesize and thus have not been widely adopted. Herein, we report the synthesis of an anionic poly(cyclopentadienylene vinylene) (aPCPV) from an insulating precursor under mild conditions and in high yield. Functionalized aPCPV is a highly water‐soluble CPE that exhibits low cytotoxicity, and we found that doping hydrogels with aPCPV imparts conductivity. We also anticipate that this synthetic strategy, due to its ease and high efficiency, will be widely used to create families of not‐yet‐explored π‐conjugated vinylene polymers.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Daniel C. Lee, Drew L. Sellers, Fan Liu, Andrew J. Boydston, Suzie H. Pun
doi.org/10.1002/anie.202004098

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Copper–Oxygen Dynamics in the Tyrosinase Mechanism

Copper–Oxygen Dynamics in the Tyrosinase Mechanism

Let’s Cu move : The dinuclear copper enzyme, tyrosinase, activates O2 and hydroxylates phenols to catechols. Substrate binding is shown to induce a rearrangement of the copper–oxygen species for hydroxylation of aromatic C−H bond. A copper center migrates (CuA1→CuA2) activating the bound substrate as well as the dioxygen molecule that is between the copper centers.

Abstract

The dinuclear copper enzyme, tyrosinase, activates O2 to form a (μ‐η22‐p eroxido)dicopper(II) species, which hydroxylates phenols to catechols. However, the exact mechanism of phenolase reaction in the catalytic site of tyrosinase is still under debate. We herein report the near atomic resolution X‐ray crystal structures of the active tyrosinases with substrate l ‐tyrosine. At their catalytic sites, CuA moved toward l ‐tyrosine (CuA1 → CuA2), whose phenol oxygen directly coordinates to CuA2, involving the movement of CuB (CuB1 → CuB2). The crystal structures and spectroscopic analyses of the dioxygen‐bound tyrosinases demonstrated that the peroxide ligand rotated, spontaneously weakening its O−O bond. Thus, the copper migration induced by the substrate‐binding is accompanied by rearrangement of the bound peroxide species so as to provide one of the peroxide oxygen atoms with access to the phenol substrate’s ϵ  carbon atom.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Nobutaka Fujieda, Kyohei Umakoshi, Yuta Ochi, Yosuke Nishikawa, Sachiko Yanagisawa, Minoru Kubo, Genji Kurisu, Shinobu Itoh
doi.org/10.1002/anie.202004733

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On‐Surface Synthesis of Cumulene‐Containing Polymers via Two‐Step Dehalogenative Homocoupling of Dibromomethylene‐Functionalized Tribenzoazulene

On‐Surface Synthesis of Cumulene‐Containing Polymers via Two‐Step Dehalogenative Homocoupling of Dibromomethylene‐Functionalized Tribenzoazulene

Superficial interactions : On‐surface investigations of tribenzoazulene molecules functionalized with two dibromomethylene groups at the pentagon and heptagon ends reveal, after sequential annealing steps, the unambiguous formation of polymers linked by cumulene‐like bonds via selective C−C coupling induced by the sequential activation of the precursor molecules on a Au(111) surface.

Abstract

Cumulene compounds are notoriously difficult to prepare and study because their reactivity increases dramatically with the increasing number of consecutive double bonds. In this respect, the emerging field of on‐surface synthesis provides exceptional opportunities because it relies on reactions on clean metal substrates under well‐controlled ultrahigh‐vacuum conditions. Here we report the on‐surface synthesis of a polymer linked by cumulene‐like bonds on a Au(111) surface via sequential thermally activated dehalogenative C−C coupling of a tribenzoazulene precursor equipped with two dibromomethylene groups. The structure and electronic properties of the resulting polymer with cumulene‐like pentagon–pentagon and heptagon–heptagon connections have been investigated by means of scanning probe microscopy and spectroscopy methods and X‐ray photoelectron spectroscopy, complemented by density functional theory calculations. Our results provide perspectives for the on‐surface synthesis of cumulene‐containing compounds, as well as protocols relevant to the stepwise fabrication of carbon–carbon bonds on surfaces.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: José I. Urgel, Marco Di Giovannantonio, Kristjan Eimre, Thorsten G. Lohr, Junzhi Liu, Shantanu Mishra, Qiang Sun, Amogh Kinikar, Roland Widmer, Samuel Stolz, Max Bommert, Reinhard Berger, Pascal Ruffieux, Carlo A. Pignedoli, Klaus Müllen, Xinliang Feng, Roman Fasel
doi.org/10.1002/anie.202001939

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N2 Electroreduction to NH3 by Selenium Vacancy‐Rich ReSe2 Catalysis at an Abrupt Interface

N2 Electroreduction to NH3 by Selenium Vacancy‐Rich ReSe2 Catalysis at an Abrupt Interface

The selenium vacancy in crystalline ReSe2 enhances its electroactivity for both nitrogen reduction and hydrogen evolution. To restrict HER, selenium vacancy‐rich ReSe2@carbonized bacterial cellulose (Vr‐ReSe2@CBC) nanofibers are buried between two CBC layers, leading to boosted Faradaic efficiency and ammonia yield on an abrupt interface.

Abstract

Vacancy engineering has been proved repeatedly as an adoptable strategy to boost electrocatalysis, while its poor selectivity restricts the usage in nitrogen reduction reaction (NRR) as overwhelming competition from hydrogen evolution reaction (HER). Revealed by density functional theory calculations, the selenium vacancy in ReSe2 crystal can enhance its electroactivity for both NRR and HER by shifting the d‐band from −4.42 to −4.19 eV. To restrict the HER, we report a novel method by burying selenium vacancy‐rich ReSe2@carbonized bacterial cellulose (Vr‐ReSe2@CBC) nanofibers between two CBC layers, leading to boosted Faradaic efficiency of 42.5 % and ammonia yield of 28.3 μg h−1 cm−2 at a potential of −0.25 V on an abrupt interface. As demonstrated by the nitrogen bubble adhesive force, superhydrophilic measurements, and COMSOL Multiphysics simulations, the hydrophobic and porous CBC layers can keep the internal Vr‐ReSe2@CBC nanofibers away from water coverage, leaving more unoccupied active sites for the N2 reduction (especially for the potential determining step of proton‐electron coupling and transferring processes as *NN → *NNH).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Feili Lai, Wei Zong, Guanjie He, Yang Xu, Haowei Huang, Bo Weng, Dewei Rao, Johan A. Martens, Johan Hofkens, Ivan P. Parkin, Tianxi Liu
doi.org/10.1002/anie.202003129

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Total Syntheses of (−)‐Strictosidine and Related Indole Alkaloid Glycosides

Total Syntheses of (−)‐Strictosidine and Related Indole Alkaloid Glycosides

A collective synthesis of glycosylated monoterpenoid indole alkaloids is reported. A highly diastereoselective Pictet–Spengler reaction with α‐cyanotryptamine and secologanin tetraacetate, followed by a reductive decyanation reaction, was developed for the synthesis of strictosidine. Subsequent bioinspired transformations resulted in the concise total syntheses of strictosamide, neonaucleoside A, cymoside, and 3α‐dihydrocadambine.

Abstract

A collective synthesis of glycosylated monoterpenoid indole alkaloids is reported. A highly diastereoselective Pictet–Spengler reaction with α‐cyanotryptamine and secologanin tetraacetate as substrates, followed by a reductive decyanation reaction, was developed for the synthesis of (−)‐strictosidine, which is an important intermediate in biosynthesis. This two‐step chemical method was established as an alternative to the biosynthetically employed strictosidine synthase. Furthermore, after carrying out chemical and computational studies, a transition state for induction of diastereoselectivity in our newly discovered Pictet–Spengler reaction is proposed. Having achieved the first enantioselective total synthesis of (−)‐strictosidine in just 10 steps, subsequent bioinspired transformations resulted in the concise total syntheses of (−)‐strictosamide, (−)‐neonaucleoside A, (−)‐cymoside, and (−)‐3α‐dihydrocadambine.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jukiya Sakamoto, Yuhei Umeda, Kenta Rakumitsu, Michinori Sumimoto, Hayato Ishikawa
doi.org/10.1002/anie.202005748

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Electrocatalytically Active Fe‐(O‐C2)4 Single‐Atom Sites for Efficient Reduction of Nitrogen to Ammonia

Electrocatalytically Active Fe‐(O‐C2)4 Single‐Atom Sites for Efficient Reduction of Nitrogen to Ammonia

Effects of distribution on performance : A single‐atom Fe electrocatalyst supported on nitrogen‐free lignocellulose‐derived graphitic carbon with Fe‐(O‐C2)4 active sites was synthesized and exceptional catalytic activity for N2 reduction to NH3 was demonstrated. The results indicate that the performance of a given catalyst is strongly influenced by factors other than its intrinsic electrocatalytic activity.

Abstract

Single‐atom catalysts have demonstrated their superiority over other types of catalysts for various reactions. However, the reported nitrogen reduction reaction single‐atom electrocatalysts for the nitrogen reduction reaction exclusively utilize metal–nitrogen or metal–carbon coordination configurations as catalytic active sites. Here, we report a Fe single‐atom electrocatalyst supported on low‐cost, nitrogen‐free lignocellulose‐derived carbon. The extended X‐ray absorption fine structure spectra confirm that Fe atoms are anchored to the support via the Fe‐(O‐C2)4 coordination configuration. Density functional theory calculations identify Fe‐(O‐C2)4 as the active site for the nitrogen reduction reaction. An electrode consisting of the electrocatalyst loaded on carbon cloth can afford a NH3 yield rate and faradaic efficiency of 32.1 μg h−1 mgcat.−1 (5350 μg h−1 mgFe−1) and 29.3 %, respectively. An exceptional NH3 yield rate of 307.7 μg h−1 mgcat.−1 (51 283 μg h−1 mgFe−1) with a near record faradaic efficiency of 51.0 % can be achieved with the electrocatalyst immobilized on a glassy carbon electrode.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Shengbo Zhang, Meng Jin, Tongfei Shi, Miaomiao Han, Qiao Sun, Yue Lin, Zhenhua Ding, Li Rong Zheng, Guozhong Wang, Yunxia Zhang, Haimin Zhang, Huijun Zhao
doi.org/10.1002/anie.202005930

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Atypical Spirotetronate Polyketides Identified in the Underexplored Genus Streptacidiphilus

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Somayah S. Elsayed*†‡, Gre´gory Genta-Jouve§?, Vi´ctor J. Carrio´n†‡, Peter H. Nibbering?, Maxime A. Siegler#, Wietse de Boer??, Thomas Hankemeier?, and Gilles P. van Wezel*†‡
feedproxy.google.com/~r/acs/joceah/~3/DpWcJxbfkDA/acs.joc.0c01210

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[Cu32(PET)24H8Cl2](PPh4)2: A Copper Hydride Nanocluster with a Bisquare Antiprismatic Core

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Sanghwa Lee†‡?, Megalamane S. Bootharaju†‡?, Guocheng Deng§?, Sami Malola?, Woonhyuk Baek†‡, Hannu Ha¨kkinen*?, Nanfeng Zheng*§, and Taeghwan Hyeon*†‡
feedproxy.google.com/~r/acs/jacsat/~3/f0dI61kINLQ/jacs.0c06577

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Magnetic Anisotropy Drives Magnetochiral Dichroism in a Chiral Molecular Helix Probed with Visible Light

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Matteo Atzori*†, Fabio Santanni‡, Ivan Breslavetz†, Ke´vin Paillot†, Andrea Caneschi§, Geert L. J. A. Rikken†, Roberta Sessoli*‡, and Cyrille Train*†
feedproxy.google.com/~r/acs/jacsat/~3/m6SE4kfJpEU/jacs.0c06166

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Virtual Screening for Ligand Discovery at the s1 Receptor

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ACS Medicinal Chemistry Letters

ACS Medicinal Chemistry Letters: Latest Articles (ACS Publications)
Authors: Daniel A. Greenfield†?, Hayden R. Schmidt†??, Meredith A. Skiba†, Michael D. Mandler‡, Jacob R. Anderson†, Piotr Sliz*†§, and Andrew C. Kruse*†
feedproxy.google.com/~r/acs/amclct/~3/yG0Irh1Lsno/acsmedchemlett.9b00314

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Using the Competing Enantioselective Conversion Method to Assign the Absolute Configuration of Cyclic Amines with Bode’s Acylation Reagents

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Charles J. Dooley, III†, Alexander Burtea†, Christina Mitilian†, Wendy T. Dao#, Bo Qu?, Nicholas T. Salzameda#, and Scott D. Rychnovsky*†
feedproxy.google.com/~r/acs/joceah/~3/4njf_YfR7n8/acs.joc.0c01275

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Visible-Light-Driven Difluoromethylation of Isocyanides with S-(Difluoromethyl)diarylsulfonium Salt: Access to a Wide Variety of Difluoromethylated Phenanthridines and Isoquinolines

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Wen-Bing Qin†, Wei Xiong†, Xin Li†, Jia-Yi Chen†, Li-Ting Lin†, Henry N. C. Wong‡, and Guo-Kai Liu*†
feedproxy.google.com/~r/acs/joceah/~3/GjzKtf8gMbo/acs.joc.0c00816

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Spectroscopic and theoretical optical properties of indoleninyl‐substituted dibenzotetraaza[14]annulenes

Spectroscopic and theoretical optical properties of indoleninyl‐substituted dibenzotetraaza[14]annulenes

Abstract

Two new macrocyclic dibenzotetraaza[14]annulene (DBTAA) compounds with indolenine (5 ) and pyridoindolenine (6 ) moieties were synthesized and characterized by spectroscopy. Both DBTAAs exhibit strong UV‐Vis absorption properties in the Soret band region. The theoretical second‐order nonlinear optical property, electric dipole moment (μ ), dispersion‐free dipole polarizability (α ) and first hyper‐polarizability values were calculated by density functional theory and time dependent density functional theory. The ab‐initio quantum mechanical calculation by time‐dependent Hartree‐Fock method was utilized to investigate the dynamic dipole polarizabilities, dynamic second‐order, static, and dynamic third‐order (γ ) hyper‐polarizabilities of the DBTAAs. The configuration interaction technique of all doubly occupied molecular orbitals possesses theoretically defined single‐photon absorption (OPA) specifications for the examined structures. The computed maximum OPA wavelengths on both macrocyclic compounds coincide with the preceding measurement outcomes.

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DABCO mediated one pot synthesis of 2‐(3‐benzyl‐2, 6‐dioxo‐3, 6‐dihydropyrimidin‐1[2H]‐yl)‐N‐(4‐(1, 3‐dioxo‐1H‐benzo [de]isoquinolin‐2[3H]‐yl) aryl) acetamides as antimicrobial agents

DABCO mediated one pot synthesis of 2‐(3‐benzyl‐2, 6‐dioxo‐3, 6‐dihydropyrimidin‐1[2H]‐yl)‐N‐(4‐(1, 3‐dioxo‐1H‐benzo [de]isoquinolin‐2[3H]‐yl) aryl) acetamides as antimicrobial agents

Abstract

We report herein DABCO mediated one pot synthesis of 2‐(3‐benzyl‐2 , 6‐dioxo‐3 ,6‐dihydropyrimidin‐1[2H]‐yl)‐N‐(4‐(1 ,3‐dioxo‐1H‐benzo[de]isoquinolin‐2[3H]‐yl) aryl) acetamides (4a‐j ) . The silent features of this new one pot synthesis include the shorter reaction time, high yields, simple workup, and simultaneous formation of N ‐Amide and N ‐benzyl bonds in the one pot. The newly synthesized compounds (4a‐j ) were characterized by different spectral techniques such as IR, 1H‐NMR, 13C‐NMR, HRMS. All the synthesized compounds were evaluated for their anti‐bacterial and anti‐fungal activities. The anti‐bacterial activities results reveal that the compounds 4a , 4g , 4i , and 4j are most active against S. aureus . In the case of B. subtilis the compounds 4a , 4i , and 4j are found to be most active. The compounds 4c , 4e , 4i , and 4j are most active against E. coli . In the case of P. aeruginosa
4a , 4i & 4j are found to be more active. On the other hand, the anti‐fungal activity result shows that the compounds 4d , 4f , 4i , and 4j are more active against A. niger . The compounds 4a , 4d , 4i , and 4j are found to be more active against C. albicans .

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Synthesis of 1,2,4‐triazolopyridazines, isoxazolofuropyridazines, and tetrazolopyridazines as antimicrobial agents

Synthesis of 1,2,4‐triazolopyridazines, isoxazolofuropyridazines, and tetrazolopyridazines as antimicrobial agents

Abstract

Through current and previous researches, it was found that the derivatives of pyridazine, isoxazole, tetrazole, quinazoline, hydrazinyl, and 1,2,4‐triazole have many pharmacological activities. Thus, a series of novel furopyridazinones (7 ), isoxazolopyridazine (8 ), sub‐benzylidene‐furopyridazinones (9a‐c ), isoxazolofuropyridazines (10a‐c ), 3‐chloro‐(pyridin‐4‐ylmethylene)‐dihydropyridazines (11 ), tetrazolopyridazines (12 ), pyridazinoquinazolinones (13 ), piperazinyl/morpholino‐pyridazines (14a,b ), hydrazinyl‐pyridazines (15 ), and 1,2,4‐triazolo‐pyridazines (16a,b ) in good yields (72%‐90%) were synthesized from substituted ethyl 4‐oxo‐4‐phenylbutanoate (2 ), 6‐phenyl‐4,5‐dihydropyridazinone (3 ), and 6‐phenyl‐4‐(pyridin‐4‐ylmethylene)‐4,5‐dihydropyridazinone (4 ) as beginning materials. All the chemical structures of the new compounds have been demonstrated by different spectroscopy analyses such as infrared, NMR, mass spectrum, and elemental analysis. Also, the activities of the newly prepared compounds were tested against many types of bacteria and fungi in vitro . Hence, 1,2,4‐triazolopyridazines (16a,b ), isoxazolofuropyridazines (10a‐c ), tetrazolopyridazines (12 ), Piperazinyl/morpholinyl‐pyridazines (14a,b ) displayed the most efficient antimicrobial activities compared with the cefotaxime sodium and nystatin as standard drugs.

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Guest‐Dependent Pressure‐Induced Spin Crossover in FeII4[MIV(CN)8]2 (M=Mo, W) Cluster‐Based Material Showing Persistent Solvent‐Driven Structural Transformations

Guest‐Dependent Pressure‐Induced Spin Crossover in FeII4[MIV(CN)8]2 (M=Mo, W) Cluster‐Based Material Showing Persistent Solvent‐Driven Structural Transformations

Spin cycle : Crystalline molecular materials based on octahedral cyanido‐bridged Fe4Mo2 and Fe4W2 clusters capped with 2‐(1‐pyrazolyl)pyridine ligands undergo a pressure‐induced thermal FeII spin crossover effect. This spin transition is strongly dependent on the presence of solvent molecules of water and methanol which can be reversibly removed and inserted into the cluster‐based framework within a single‐crystal‐to‐single‐crystal phase transformation.

Abstract

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido‐bridged coordination clusters {[FeII(2‐pyrpy)2]4[MIV(CN)8]2}4 MeOH6 H2O (M=Mo (1 solv ), M=W (2 solv ) and 2‐pyrpy=2‐(1‐pyrazolyl)pyridine are presented, which show persistent solvent driven single‐crystal‐to‐single‐crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation–resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe4M2 molecules constitute a unique example where the presence of the guests directly affects the pressure‐induced thermal spin crossover (SCO) phenomenon occurring at the FeII centres. The hydrated phases show a partial SCO with approximately two out‐of‐four FeII centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure‐induced SCO effect is almost quenched with only 15 % of the FeII centres undergoing high‐spin to low‐spin transition at 1 GPa.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Robert Jankowski, Mateusz Reczyński, Szymon Chorazy, Mikołaj Zychowicz, Mirosław Arczyński, Marcin Kozieł, Karolina Ogorzały, Wacław Makowski, Dawid Pinkowicz, Barbara Sieklucka
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202000146

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