Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity

Protein design is a useful strategy to interrogate the protein structure‐function relationship. We demonstrate using a highly modular 3‐stranded coiled coil (TRI‐peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H₂O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75‐fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three‐coordinate Cu^I in a site, which tends toward two‐coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal‐center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.     

Protonation state of the Cu4S2 CuZ site in nitrous oxide reductase: redox dependence and insight into reactivity

Spectroscopic and computational methods have been used to determine the protonation state of the edge sulfur ligand in the Cu₄S₂ Cu_Z form of the active site of nitrous oxide reductase (N₂OR) in its 3Cu^ICu^II (1-hole) and 2Cu^I2Cu^II (2-hole) redox states. The EPR, absorption, and MCD spectra of 1-hole Cu_Z indicate that the unpaired spin in this site is evenly delocalized over Cu_I, Cu_II, and Cu_IV. 1-hole Cu_Z is shown to have a μ₂-thiolate edge ligand from the observation of S–H bending modes in the resonance Raman spectrum at 450 and 492 cm^–1 that have significant deuterium isotope shifts (–137 cm^–1) and are not perturbed up to pH 10. 2-hole Cu_Z is characterized with absorption and resonance Raman spectroscopies as having two Cu–S stretching vibrations that profile differently. DFT models of the 1-hole and 2-hole Cu_Z sites are correlated to these spectroscopic features to determine that 2-hole Cu_Z has a μ₂-sulfide edge ligand at neutral pH. The slow two electron (+1 proton) reduction of N₂O by 1-hole Cu_Z is discussed and the possibility of a reaction between 2-hole Cu_Z and O₂ is considered.     

Reactions of Fe2(μ‐odt)(CO)6 (odt = 1, 3‐oxadithiolate) with small bite‐angle diphosphines to afford the monodentate,chelate, and bridge diiron complexes: Selective substitution,structures, protonation,and electrocatalytic proton reduction

Selective substitutions of Fe₂(μ‐odt)(CO)₆ (odt = 1,3‐oxadithiolate, A ) and small bite‐angle diphosphines (Ph₂P)₂X [X = CH₂ (dppm) or N (CH₂CHMe₂) (dppa)] have been well investigated in this study. With Me₃NO·2H₂O in MeCN at room temperature, the reaction of A and dppm produced the monodentate complex [Fe₂(μ‐odt)(CO)₅(κ¹‐dppm)] ( 1 ), whereas the similar reaction with dppa afforded the chelate complex [Fe₂(μ‐odt)(CO)₄(κ²‐dppa)] ( 2 ). Using UV irradiation in toluene emitting at 365 nm, the treatment of A and dppm rarely resulted in the formation of the bridge complex [Fe₂(μ‐odt)(CO)₄(μ‐dppm)] ( 3 ), whereas the similar treatment with dppa formed the chelate complex 2 . Under thermolysis condition, refluxing solution of A with dppm or dppa gave the bridge complex 3 and [Fe₂(μ‐odt)(CO)₄(μ‐dppa)] ( 4 ), respectively, in which the former was formed in toluene (110 °C) but the latter was produced in xylene (138 °C). All the new complexes 1 – 4 obtained above were characterized by element analysis, FT‐IR, NMR (¹H, ³¹P) spectroscopies, and particularly for 1 – 3 by X‐ray crystallography. Furthermore, the in situ protonations of 2 with a weak acid HOAc (acetic acid) and a strong acid TFA (trifluoroacetic acid) are explored by means of FT‐IR and NMR (¹H, ³¹P) spectra. In addition, the electrochemical behaviors of 2 – 4 are studied and compared through cyclic voltammetry (CV) in the absence and presence of a strong acid (TFA) as a proton source, indicating that they all are active for electrocatalytic proton reduction to hydrogen (H₂).     

The new three‐dimensional supramolecule bis{μ‐2‐[(4‐hydroxybenzoyl)hydrazonomethyl]phenolato}bis[aquacopper(II)] dinitrate

In the title centrosymmetric binuclear complex, [Cu₂(C₁₄H₁₁N₂O₃)₂(H₂O)₂](NO₃)₂, the two metal centres are bridged by the phenolate O atoms of the ligand, forming a Cu₂O₂ quadrangle. Each Cu atom has a distorted square‐pyramidal geometry, with the basal donor atoms coming from the O,N,O′‐tridentate ligand and a symmetry‐related phenolate O atom. The more weakly bound apical donor O atom is supplied by a coordinated water molecule. When a further weak Cu...O interaction with the 4‐hydroxy O atom of a neighbouring cation is considered, the extended coordination sphere of the Cu atom can be described as distorted octahedral. This interaction leads to two‐dimensional layers, which extend parallel to the (100) direction. The two‐dimensional polymeric structure contrasts with other reported structures involving salicylaldehyde benzoylhydrazone ligands, which are usually discrete mono‐ or dinuclear Cu complexes. The nitrate anions are involved in a three‐dimensional hydrogen‐bonding network, featuring intermolecular N—H...O and O—H...O hydrogen bonds.     

The chiral helical structure of a copper(II) complex with a tridentate Schiff base ligand

In the title salt, catena‐poly[[[aquacopper(II)]‐μ‐3‐(2‐pyridylmethyleneamino)propanoato‐κ⁴N,N′,O:O′] perchlorate], {[Cu(C₉H₉N₂O₂)(H₂O)]ClO₄}_n, the monomeric unit contains a square‐based pyramidal Cu^II centre. The four basal positions are occupied by a tridentate anionic Schiff base ligand which furnishes an NNO‐donor set, with the fourth basal position being occupied by an O‐donor atom from the carboxylate group of an adjacent Schiff base ligand. The coordination sphere is completed by a water molecule at the apical position. Interestingly, each carboxylate group in the ligand forms a syn–anti‐configured bridge between two Cu^II centres, leading to left‐handed chiral helicity. The framework also exhibits O—H...O hydrogen bonds involving the water molecules and an O atom of the perchlorate anion.     

N2O…HOCl复合物结构和性质的理论研究

分别在DFT-B3LYP和MP2/6-311++G**水平上求得HOCl + N2O复合物势能面上的六种(S1, S2, S3, S4, S5和S6)和四种(S1, S2, S4和S5)构型. 频率分析表明,其中的S1和S3为过渡态,其它为稳定构型. 在复合物S3, S5 和S6中,HOCl 单体的σ*(5O-6H)作为质子供体,与N2O单体中作为质子受体的3O原子相互作用,形成氢键结构,而在氢键复合物S2中, 质子受体为N2O单体中的端1N原子;复合物S1中,HOCl分子的σ*(5O-4Cl)作为质子供体与N2O分子中的端1N原子(质子受体)相互作用,形成卤键结构,而复合物S4中的卤键结构的质子受体为N2O分子中的端3O原子. 经B3LYP/6-311++G**水平上的计算,考虑了基组重叠误差(BSSE)校正的单体间相互作用能在-1.56 ~ -8.73 kJ·mol-1之间. 采用自然键轨道理论(NBO)对两种单体间相互作用的本质进行了考查,并通过分子中原子理论(AIM)分析了复合物中氢键和卤键键鞍点处的电子密度拓扑性质.     

Origin of Nitric Oxide Reduction Activity in Flavo–Diiron NO Reductase: Key Roles of the Second Coordination Sphere

The second coordination sphere constitutes a distinguishing factor in the active site to modulate enzymatic reactivity. To unravel the origin of NO‐to‐N₂O reduction activity of non‐heme diiron enzymes, herein we report a strong second‐coordination‐sphere interaction between a conserved Tyr₁₉₇ and the key iron–nitrosyl intermediate of Tm FDP (flavo–diiron protein), which leads to decreased reaction barriers towards N–N formation and N–O cleavage in NO reduction. This finding supports the direct coupling of diiron dinitrosyl as the N–N formation mode in our QM/MM modeling, and reconciles the mechanistic controversy of external reduction between FDPs and synthetic biomimetics of the iron–nitrosyls. This work highlights the application of QM/MM ⁵⁷Fe Mössbauer modeling in elucidating the structural features of not only first, but also second coordination spheres of the key transient species involved in NO/O₂ activation by non‐heme diiron enzymes.     

Impact of Intramolecular Hydrogen Bonding on the Reactivity of Cupric Superoxide Complexes with O−H and C−H Substrates

The dioxygen reactivity of a series of TMPA‐based copper(I) complexes (TMPA=tris(2‐pyridylmethyl)amine), with and without secondary‐coordination‐sphere hydrogen‐bonding moieties, was studied at ?135 °C in 2‐methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H‐bonded [( TMPA)Cu^II(O₂^.?)]⁺ cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)Cu^II(N₃^?)]⁺ azido analogues were compared, and the O₂^.? reactivity of ligand–Cu^I complexes when an H‐bonding moiety is replaced by a methyl group was contrasted. A drastic enhancement in the reactivity of the cupric superoxide towards phenolic substrates as well as oxidation of substrates possessing moderate C?H bond‐dissociation energies is observed, correlating with the number and strength of the H‐bonding groups.     

Probing the electronic and mechanistic roles of the μ4-sulfur atom in a synthetic CuZ model system

Nitrous oxide (N₂O) contributes significantly to ozone layer depletion and is a potent greenhouse agent, motivating interest in the chemical details of biological N₂O fixation by nitrous oxide reductase (N₂OR) during bacterial denitrification. In this study, we report a combined experimental/computational study of a synthetic [4Cu:1S] cluster supported by N-donor ligands that can be considered the closest structural and functional mimic of the Cu_Z catalytic site in N₂OR reported to date. Quantitative N₂ measurements during synthetic N₂O reduction were used to determine reaction stoichiometry, which in turn was used as the basis for density functional theory (DFT) modeling of hypothetical reaction intermediates. The mechanism for N₂O reduction emerging from this computational modeling involves cooperative activation of N₂O across a Cu/S cluster edge. Direct interaction of the μ₄-S ligand with the N₂O substrate during coordination and N–O bond cleavage represents an unconventional mechanistic paradigm to be considered for the chemistry of Cu_Z and related metal–sulfur clusters. Consistent with hypothetical participation of the μ₄-S unit in two-electron reduction of N₂O, Cu K-edge and S K-edge X-ray absorption spectroscopy (XAS) reveal a high degree of participation by the μ₄-S in redox changes, with approximately 21% S 3p contribution to the redox-active molecular orbital in the highly covalent [4Cu:1S] core, compared to approximately 14% Cu 3d contribution per copper. The XAS data included in this study represent the first spectroscopic interrogation of multiple redox levels of a [4Cu:1S] cluster and show high fidelity to the biological Cu_Z site.

Experimental data and computational modeling indicates an active role for the bridging sulfide ligand in a synthetic Cu_Z model.     

Mechanistic Studies on the Oxidation of Nitrite by a μ‐Oxodiiron(III,III) Complex in Aqueous Acidic Media

Examined in this study is the kinetics of a net 2e⁻ transfer between [Fe₂(μ‐O)(phen)₄(H₂O)₂]⁴⁺ ( 1 ) and its hydrolytic derivatives [Fe₂(μ‐O)(phen)₄(H₂O)(OH)]³⁺ ( 2 ) and [Fe₂(μ‐O)(phen)₄(OH)₂]²⁺ ( 3 ) with in aqueous media and in presence of excess 1,10‐phenanthroline (phen). The reaction is quantitative with a 1 : 1 stoichiometry between the oxidant and reductant to produce ferroin ([Fe(phen)₃]²⁺) and . The order of reactivity of the oxidant species is 1 > 2 > 3 , in agreement with the progressive cationic charge reduction. The reactions appear to be inner‐sphere where the initial one‐electron proton‐coupled redox (1e⁻, 1H⁺; electroprotic) seems to be rate‐determining.     

Ligand‐forced dimerization of copper(I)–olefin complexes bearing a 1,3,4‐thiadiazole core

As an important class of heterocyclic compounds, 1,3,4‐thiadiazoles have a broad range of potential applications in medicine, agriculture and materials chemistry, and were found to be excellent precursors for the crystal engineering of organometallic materials. The coordinating behaviour of allyl derivatives of 1,3,4‐thiadiazoles with respect to transition metal ions has been little studied. Five new crystalline copper(I) π‐complexes have been obtained by means of an alternating current electrochemical technique and have been characterized by single‐crystal X‐ray diffraction and IR spectroscopy. The compounds are bis[μ‐5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine]bis[nitratocopper(I)], [Cu₂(NO₃)₂(C₆H₉N₃S)₂], (1), bis[μ‐5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine]bis[(tetrafluoroborato)copper(I)], [Cu₂(BF₄)₂(C₆H₉N₃S)₂], (2), μ‐aqua‐bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}bis[nitratocopper(I)], [Cu₂(NO₃)₂(C₅H₇N₃S₂)₂(H₂O)], (3), μ‐aqua‐(hexafluorosilicato)bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}dicopper(I)–acetonitrile–water (2/1/4), [Cu₂(SiF₆)(C₅H₇N₃S₂)₂(H₂O)]·0.5CH₃CN·2H₂O, (4), and μ‐benzenesulfonato‐bis{μ‐5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine}dicopper(I) benzenesulfonate–methanol–water (1/1/1), [Cu₂(C₆H₅O₃S)(C₅H₇N₃S₂)₂](C₆H₅O₃S)·CH₃OH·H₂O, (5). The structure of the ligand 5‐methyl‐N‐(prop‐2‐en‐1‐yl)‐1,3,4‐thiadiazol‐2‐amine (Mepeta ), C₆H₉N₃S, was also structurally characterized. Both Mepeta and 5‐[(prop‐2‐en‐1‐yl)sulfanyl]‐1,3,4‐thiadiazol‐2‐amine (Pesta ) (denoted L ) reveal a strong tendency to form dimeric {Cu₂L ₂}²⁺ fragments, being attached to the metal atom in a chelating–bridging mode via two thiadiazole N atoms and an allylic C=C bond. Flexibility of the {Cu₂(Pesta )₂}²⁺ unit allows the Cu^I atom site to be split into two positions with different metal‐coordination environments, thus enabling the competitive participation of different molecules in bonding to the metal centre. The Pesta ligand in (4) allows the Cu^I atom to vary between water O‐atom and hexafluorosilicate F‐atom coordination, resulting in the rare case of a direct Cu^I…FSiF₅²⁻ interaction. Extensive three‐dimensional hydrogen‐bonding patterns are formed in the reported crystal structures. Complex (5) should be considered as the first known example of a Cu^I(C₆H₅SO₃) coordination compound. To determine the hydrogen‐bond interactions in the structures of (1) and (2), a Hirshfeld surface analysis has been performed.     

Preparation and characterization of two new CuII supramolecular coordination polymers incorporating sulfobenzoate and flexible heterocyclic ligands

The assembly of Cu^II with the multifunctional ligand 2‐amino‐4‐sulfobenzoic acid (H₂asba) in the presence of the auxiliary flexible ligands 1,4‐bis(triazol‐1‐ylmethyl)benzene (bbtz) and 1,4‐bis(imidazol‐1‐ylmethyl)benzene (bix) under ambient conditions resulted in two new supramolecular coordination polymers, namely poly[[(3‐amino‐4‐carboxybenzenesulfonato‐κO )aquabis[μ₂‐1,4‐bis(triazol‐1‐ylmethyl)benzene‐κ²N ⁴:N ^4′]copper(II)] 3‐amino‐4‐carboxybenzenesulfonate tetrahydrate], {[Cu(C₇H₆NO₅S)(C₁₂H₁₂N₆)₂(H₂O)](C₇H₆NO₅S)·4H₂O}_n , ( 1 ), and poly[[bis(μ₂‐2‐amino‐4‐sulfonatobenzoato‐κ³O ¹:N ,O ^1′)tetraaqua[μ₂‐1,4‐bis(triazol‐1‐ylmethyl)benzene‐κ²N ⁴:N ^4′]dicopper(II)] tetrahydrate], {[Cu₂(C₇H₅NO₅S)₂(C₁₄H₁₄N₄)(H₂O)₄]·4H₂O}_n , ( 2 ). Single‐crystal X‐ray structure diffraction analysis of ( 1 ) reveals that the bbtz ligand acts as a bridge, linking adjacent Cu^II ions into a two‐dimensional cationic (4,4) topological network, in which the coordinated 3‐amino‐4‐carboxybenzenesulfonate (Hasba⁻) anion uses its sulfonate group to bind with the Cu^II ion in a monodentate fashion and the carboxylate group remains protonated. The lattice Hasba⁻ anion resides in the two‐dimensional layer and balances the charge. The carboxylate group of the 2‐amino‐4‐sulfonatobenzoate (asba²⁻) ligand in ( 2 ) is involved in bidentate coordination, connecting adjacent Cu^II ions into carboxylate‐bridged chains which are further bridged by the auxiliary flexible bix ligand in a trans –gauche (TG) mode, resulting in the formation of a two‐dimensional network architecture. The amino group of the asba²⁻ ligand in ( 2 ) also takes part in the coordination with the central Cu^II ion. The six‐coordinated Cu^II centres in ( 1 ) and ( 2 ) exhibit distorted octahedral coordination geometries. Extensive hydrogen bonding exists in both ( 1 ) and ( 2 ). The interlayer hydrogen bonds in both compounds further extend adjacent two‐dimensional layers into three‐dimensional supramolecular network architectures. Furthermore, a detailed analysis of the solid‐state UV–Vis–NIR (NIR is near IR) diffuse reflectance data indicates that ( 1 ) and ( 2 ) may have potential as wide band gap indirect semiconductor materials. Compounds ( 1 ) and ( 2 ) show reversible and irreversible dehydration–rehydration behaviours, respectively.     

Structure and Magnetic Properties of Mononuclear Copper(II) Complexes with 2,2‐Bipyrimidine, 2,3‐Bis(2‐pyridyl)pyrazine,and 4‐Terpyridone Based Ligands

Four new complexes of [Cu(bpm)(ox)(H₂O)] ( 1 ), [Cu(tpd)(dca)(H₂O)] ( 2 ), [Cu(bppz)(N₃)₂] ( 3 ), and [Cu(bpm)₂(μ_1,3‐N₃)(N₃)] ( 4 ) (bpm = 2,2′‐bipyrimidine, bppz = 2,3‐bis(2‐pyridyl)pyrazine, tpd = 4‐terpyridone, dca = dicyanamide, ox = oxalate) have been prepared and characterized by X‐ray single‐crystal analysis and variable‐temperature magnetic measurements. Compounds 1–4 are essentially mononuclear Cu(II) complexes. However, in complex 1 , Cu(II) it was found that intermolecular hydrogen bonding through between H₂O and ox formed 1‐D chain structure. In complex 2 it was found that the hydrogen bonding between H₂O and tpd of the next molecule led to for a binuclear Cu(II) complex. In complex 3 , two nitrogen atoms, one of the pyridyl group of bppz and one of N₃^? ligands, are weakly coordinated to neighbor Cu(II) ion thus leading to formation of a 1‐D chain structure. In complex 4 , one nitrogen atom of terminated N₃^? is weakly coordinated to the neighbor Cu(II) site to form a 1‐D polymeric structure. The magnetic susceptibility measurements indicate that complex 1 and 4 exhibit a weak antiferromagnetic interaction whereas a ferromagnetic coupling has been established for complexes 2 and 3 .     

(1,3‐Dimethylimidazolidine‐2‐selone‐κSe)bis(1,10‐phenanthroline‐κ2N,N′)copper(II) bis(perchlorate) and bis(2,2′‐bipyridyl‐κ2N,N′)(imidazolidine‐2‐thione‐κS)copper(II) bis(perchlorate)

In the first title salt, [Cu(C₁₂H₈N₂)₂(C₅H₁₀N₂Se)](ClO₄)₂, the Cu^II centre occupies a distorted trigonal–bipyramidal environment defined by four N donors from two 1,10‐phenanthroline (phen) ligands and by the Se donor of a 1,3‐dimethylimidazolidine‐2‐selone ligand, with the equatorial plane defined by the Se and by two N donors from different phen ligands and the axial sites occupied by the two remaining N donors, one from each phen ligand. The Cu—N distances span the range 1.980 (10)–2.114 (11) Å and the Cu—Se distance is 2.491 (3) Å. Intermolecular π–π contacts between imidazolidine rings and the central rings of phen ligands generate chains of cations. In the second salt, [Cu(C₁₀H₈N₂)₂(C₃H₆N₂S)](ClO₄)₂, the Cu^II centre occupies a similar distorted trigonal–bipyramidal environment comprising four N donors from two 2,2′‐bipyridyl (bipy) ligands and an S donor from an imidazolidine‐2‐thione ligand. The equatorial plane is defined by the S donor and two N donors from different bipy ligands. The Cu—N distances span the range 1.984 (6)–2.069 (7) Å and the Cu—S distance is 2.366 (3) Å. Intermolecular π–π contacts between imidazolidine and pyridyl rings form chains of cations. A major difference between the two structures is due to the presence in the second complex of two N—H...O hydrogen bonds linking the imidazolidine N—H hydrogen‐bond donors to perchlorate O‐atom acceptors.     

Crystallographic characterization of the first reported crystalline form of the potent hallucinogen (R)‐2‐amino‐1‐(8‐bromobenzo[1,2‐b;5,4‐b′]difuran‐4‐yl)propane or `bromodragonfly': the 1:1 anhydrous proton‐transfer compound with 3,5‐dinitrosalicylic acid

The 1:1 proton‐transfer compound of the potent substituted amphetamine hallucinogen (R)‐2‐amino‐1‐(8‐bromobenzo[1,2‐b;5,4‐b′]difuran‐4‐yl)propane (common trivial name `bromodragonfly') with 3,5‐dinitrosalicylic acid, namely 1‐(8‐bromobenzo[1,2‐b;5,4‐b′]difuran‐4‐yl)propan‐2‐aminium 2‐carboxy‐4,6‐dinitrophenolate, C₁₃H₁₃BrNO₂⁺·C₇H₃N₂O₇⁻, forms hydrogen‐bonded cation–anion chain substructures comprising undulating head‐to‐tail anion chains formed through C(8) carboxyl–nitro O—H...O associations and incorporating the aminium groups of the cations. The intrachain cation–anion hydrogen‐bonding associations feature proximal cyclic R₃³(8) interactions involving both an N⁺—H...O_phenolate and the carboxyl–nitro O—H...O associations and aromatic π–π ring interactions [minimum ring centroid separation = 3.566 (2) Å]. A lateral hydrogen‐bonding interaction between the third aminium H atom and a carboxyl O‐atom acceptor links the chain substructures, giving a two‐dimensional sheet structure. This determination represents the first of any form of this compound and is in the (R) absolute configuration. The atypical crystal stability is attributed both to the hydrogen‐bonded chain substructures provided by the anions, which accommodate the aminium proton‐donor groups of the cations and give crosslinking, and to the presence of the cation–anion aromatic ring π–π interactions.     

A new copper(II) supramolecular coordination polymer and a dinuclear compound with multifunctional 2‐amino‐5‐sulfobenzoic acid and flexible N‐donor ligands: synthesis,structure and characterization

Multifunctional 2‐amino‐5‐sulfobenzoic acid (H₂afsb) can exhibit a variety of roles during the construction of supramolecular coordination polymers. The pendant carboxylic acid, sulfonic acid and amino groups could not only play a role in directing bonding but could also have the potential to act as hydrogen‐bond donors and acceptors, resulting in extended high‐dimensional supramolecular networks. Two new Cu^II coordination compounds, namely catena‐poly[[[diaquacopper(II)]‐μ‐1,6‐bis(1H‐1,2,4‐triazol‐1‐yl)hexane‐κ²N⁴:N^4′] bis(3‐amino‐4‐carboxybenzenesulfonate) dihydrate], {[Cu(C₁₀H₁₆N₆)₂(H₂O)₂](C₇H₆NO₅S)₂·2H₂O}_n or {[Cu(bth)₂(H₂O)₂](Hafsb)₂·2H₂O}_n, (1), and bis(μ‐2‐amino‐5‐sulfonatobenzoato‐κ²O¹:O^1′)bis{μ‐1,2‐bis[(1H‐imidazol‐1‐yl)methyl]benzene‐κ²N³:N^3′}bis[aquacopper(II)] trihydrate, [Cu₂(C₇H₅NO₅S)₂(C₁₄H₁₄N₄)₂(H₂O)₂]·3H₂O or [Cu₂(afsb)₂(obix)₂(H₂O)₂]·3H₂O, (2), have been obtained through the assembly between H₂afsb and the Cu^II ion in the presence of the flexible N‐donor ligands 1,6‐bis(1H‐1,2,4‐triazol‐1‐yl)hexane (bth) and 1,2‐bis[(1H‐1,2,4‐triazol‐1‐yl)methyl]benzene (obix), respectively. Compound (1) consists of a cationic coordination polymeric chain and 3‐amino‐4‐carboxybenzenesulfonate (Hafsb⁻) anions. Compound (2) exhibits an asymmetric dinuclear structure. There are hydrogen‐bonded networks within the lattices of (1) and (2). Interestingly, both (1) and (2) exhibit reversible dehydration–rehydration behaviour.     

Synthesis and Structural Characterization of two Novel Copper(I) Complexes with Oxygen Donor

Two novel copper(I) complexes with Cu‐O bonds, [Cu₂L₂(PPh₃)₂](BF₄)₂ ( 1 ) and [Cu(L)(dppeo)](BF₄) ( 2 ) ( L = 6‐(4‐diethylmethylphosphonatephenyl)‐2,2′‐bipyridine, dppeo = bis(diphenylphosphino)ethane monoxide), have been prepared and their structures characterized. In the binuclear complex 1 , the ligand L serves as tridentate donor with the N, N′ and O as coordination atoms, and the two Cu^I atoms are bridged through both P = O donor atoms in different ligand L with a triphenylphosphine molecule as auxiliary ligand. While in mononuclear complex 2 , both ligands L and dppeo behave as bidentate with N^∧N from L and P^∧O from dppeo chelating to Cu^I atom.     

Stable Four‐Coordinate Guanidinatosilicon(IV) Complexes with SiN3El Skeletons (El=S,Se, Te) and SiEl Double Bonds

To get information about the reactivity profile of the donor‐stabilized guanidinatosilicon(II) complexes 2 and 3 , a series of oxidative addition reactions was studied. Treatment of 2 and 3 with S₈, Se, or Te afforded the respective four‐coordinate silicon(IV ) complexes 8 – 10 and 12 – 14 , which contain an SiN₃El skeleton (El=S, Se, Te) with an Si?El double bond. Treatment of 2 with N₂O yielded the dinuclear four‐coordinate silicon(IV) complex 11 with an SiN₃O skeleton and a central four‐membered Si₂O₂ ring. Compounds 8 – 14 exist both in the solid state and in solution. They were characterized by elemental analyses, NMR spectroscopic studies in the solid state and in solution, and crystal structure analyses. The reactivity profile of 2 was compared with that of the structurally related bis[N,N′‐diisopropylbenzamidinato(?)]silicon(II) ( 1 ), which is three‐coordinate in the solid state and four‐coordinate in solution ( 1′ ). In contrast, as shown by state‐of‐the‐art relativistic DFT analyses and experimental studies, silylene 2 is three‐coordinate both in the solid state and solution. The three‐coordinate species 2 is 9.3 kcal mol^?1 more stable in benzene than the four‐coordinate isomer 2′ . The reason for this was studied by bonding analyses of 2 and 2′ , which were compared with those of 1 and 1′ . The gas‐phase proton affinities of the relevant species in solution ( 1 ′ and 2 ) amount to 288.8 and 273.8 kcal mol^?1, respectively.     

Three oxo complexes with a tetra­nuclear [Cu4(μ2‐Cl)6(μ4‐O)] unit

The three title compounds, namely 4‐phenyl‐1H‐imidazolium hexa‐μ₂‐chloro‐chloro‐μ₄‐oxo‐tris­(4‐phenyl‐1H‐imidazole‐κN¹)­tetra­copper(II) monohydrate, (C₉H₉N₂)[Cu₄Cl₇O(C₉H₈N₂)₃]·H₂O, hexa‐μ₂‐chloro‐μ₄‐oxo‐tetra­kis­(pyridine N‐oxide‐κO)tetra­copper(II), [Cu₄Cl₆O(C₅H₅NO)₄], and hexa‐μ₂‐chloro‐tetra­kis(2‐methyl‐1H‐imidazole‐κN¹)‐μ₄‐oxo‐tetra­copper(II) methanol trisolvate, [Cu₄Cl₆O(C₄H₆N₂)₄]·3CH₄O, exhibit the same Cu₄OCl₆ framework, where the O atom at the centre of an almost regular tetra­hedron bridges four copper cations at the corners. This group is in turn surrounded by a Cl₆ octa­hedron, leading to a rather globular species. This special arrangement of the Cu^II cations results in a diversity of magnetic behaviours.     

Synthesis,Structures and Magnetic Properties of Two Binuclear Cobalt(II) Complexes Bridged by Bis(p‐nitrophenyl) Phosphate or Diphenylphosphinate Ion

Two new binuclear cobalt(II) complexes, [Co₂ L¹ (μ₂‐DPP)]²⁺ ( 1 ) (H L¹ = N, N, N′, N′‐ tetrakis (2‐benzimidazolylmethyl)‐2‐hydroxyl ‐1,3‐diaminopropane; DPP = diphenylphosphinate) and [Co₂ L² (μ₂‐BNPP)₂]⁺ ( 2 ) (H L² = 2,6‐bis‐[N,N‐di(2‐ pyridylmethyl)aminomethyl]‐4‐methylphenol, BNPP = bis(4‐nitrophenyl)phosphate) have been synthesized and their crystal structures and magnetic properties are shown. In 1 , each Co^II atom has a distorted trigonal bipyramidal coordination sphere with a N₃O₂ donor set and the central two Co^II atoms are bridged by one alkoxo‐O atom and one μ₂‐DPP ion with the Co1‐Co2 separation of 3.542Å. In 2 , each Co^II atom has a pseudo octahedral environment with a N₃O₃ donor set and the central two Co^II atoms are bridged by a phenolic oxygen atom of L² and two μ₂‐BNPP ions with the Co1‐Co2 separation of 3.667Å. Susceptibility data of 1 and 2 indicate intramolecular antiferromagnetic coupling of the high‐spin Co^II atoms.