Polyoxometalates as a Novel Class of Artificial Proteases: Selective Hydrolysis of Lysozyme under Physiological pH and Temperature Promoted by a Cerium(IV) Keggin‐Type Polyoxometalate

Hen‐egg‐white lysozyme (HEWL) is specifically cleaved at the Trp28–Val29 and Asn44–Arg45 peptide bonds in the presence of a Keggin‐type [Ce(α‐PW₁₁O₃₉)₂]^10? polyoxometalate (POM; 1 ) at pH 7.4 and 37 °C. The reactivity of 1 towards a range of dipeptides was also examined and the calculated reaction rates were comparable to those observed for the hydrolysis of HEWL. Experiments with α‐lactalbumin (α‐LA), a protein that is structurally highly homologous to HEWL but has a different surface potential, showed no evidence of hydrolysis, which indicates the importance of electrostatic interactions between 1 and the protein surface for the hydrolytic reaction to occur. A combination of spectroscopic techniques was used to reveal the molecular interactions between HEWL and 1 that lead to hydrolysis. NMR spectroscopy titration experiments showed that on protein addition the intensity of the ³¹P NMR signal of 1 gradually decreased due to the formation of a large protein/polyoxometalate complex and completely disappeared when the HEWL/ 1 ratio reached 1:2. Circular dichroism (CD) measurements of HEWL indicate that addition of 1 results in a clear decrease in the signal at λ=208 nm, which is attributed to changes in the α‐helical content of the protein. ¹⁵N–¹H heteronuclear single quantum coherence (HSQC) NMR measurements of HEWL in the presence of 1 reveal that the interaction is mainly observed for residues that are located in close proximity to the first site in the α‐helical part of the structure (Trp28–Val29). The less pronounced NMR spectroscopic shifts around the second cleavage site (Asn44–Arg45), which is found in the β‐strand region of the protein, might be caused by weaker metal‐directed binding, compared with strong POM‐directed binding at the first site.     

Syntheses and Characterization of Mixed‐Anions Lead(II) Complexes, [Pb(phen)2(CH3COO)]X (X=NCS—, NO3— and ClO4—), Crystal Structure of [Pb(phen)2(CH3COO)](ClO4)

The 1:2 adduct lead(II) complexes with 1, 10‐phenanthroline (phen) containing three different anions, [Pb(phen)₂(CH₃COO)X] (X=NCS^—, NO₃^— and ClO₄^—), have been synthesized and characterized by CHN elemental analysis, IR‐, ¹H‐ and ¹³C NMR spectroscopy. The structure of [Pb(phen)₂(CH₃COO)(ClO₄)] was determined by single crystal X‐ray analysis. The Pb atom of the monomeric complex is coordinated by four nitrogen atoms of two 1, 10‐phenanthroline ligands and two oxygen atoms of the acetate ligand to form an irregular octahedron. The arrangement of the 1, 10‐phenanthroline and acetate ligands, exhibits a coordination gap around the Pb^II ion, possibly occupied by a stereochemical electron active lone pair on lead(II), which results in a hemidirected lead compound. The π‐π stacking interaction between the parallel aromatic rings may help to increase the coordination ‘gap’ around the Pb^II ion.     

A liquid crystal derived from ­ruthenium(II,III) and a long‐chain carboxylate

The title compound, catena‐poly[[tetrakis(μ‐decanoato‐κ²O:O′)diruthenium(II,III)(Ru—Ru)]‐μ‐octanesulfonato‐κ²O:O′], [Ru₂(C₁₀H₁₉O₂)₄(C₈H₁₇O₃S)], is an octane­sulfonate derivative of the mixed‐valence complex diruthenium tetradecanoate. The equatorial carboxyl­ate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octane­sulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxyl­ate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non‐polar alkyl groups, without interdigitation of the alkyl chains.     

Tetra(3‐methoxypropionato)diruthenium(II,III) Units: Supramolecular Organization in the Complex [Ru2(μ‐O2CCH2CH2OMe)4(H2O)2]BF4

The synthesis and characterization of Ru₂Cl(μ‐O₂CCH₂CH₂OMe)₄ ( 1 ), [Ru₂(μ‐O₂CCH₂CH₂OMe)₄(H₂O)₂]BF₄ ( 2 ), PPh₄[Ru₂Cl₂(μ‐O₂CCH₂CH₂OMe)₄] ( 3 ), (PPh₄)₂[Ru₂Br₂(μ‐O₂CCH₂CH₂OMe)₄]NO₃ ( 4 ), and (PPh₄)₂[Ru₂I₂(μ‐O₂CCH₂CH₂OMe)₄]I_0.5(NO₃)_0.5 ( 5 ), are described. The structure of complexes 2 – 5 was established by single crystal X‐ray diffraction. All complexes show a diruthenium(II, III) unit bridged by four 3‐methoxypropionate ligands. The cationic complex 2 have two axially coordinated water molecules, with a Ru–Ru bond distance of 2.2681(12) Å. This complex shows a supramolecular two‐dimensional organization across hydrogen bonded between the axial water molecules and two methoxy groups of adjacent diruthenium units. The metal‐metal bond lengths, in the anionic complexes 3 , 4 , and 5 , are 2.3039(5), 2.3077(6), and 2.3115(8) Å, respectively. These distances are longer than the observed in compound 2 . In the anionic complexes, the axial positions of the diruthenium units are occupied by two halide ligands. Complexes 3 – 5 have PPh₄⁺ cations as counterion, although 4 and 5 are double salts with PPh₄NO₃ and PPh₄I_0.5(NO₃)_0.5, respectively. All compounds have been also characterized by elemental analysis, magnetic measurements, and spectroscopic techniques.     

Electrochemical studies on three polar diruthenium(II,III) complexes

Electrochemical studies on a new class of diruthenium(II,III) compounds were done. The complexes having a polar arrangement of ligands across the diruthenium unit in Ru₂Cl(hp)₄(Hhp), Ru₂Cl(chp)₄ and Ru₂Cl(PhNpy)₄ where Hhp, Hchp and PhNHpy are 2-hydroxypyridine, 6-chloro-2-hydroxypyridine, and 2-anilinopyridine, respectively, undergo two or more oxidations and reductions. The metal centered reductions in the range of +0.1 to ?0.75 V and oxidations in the range +0.5 to +1.2 V are discussed and compared with diruthenium carboxylato and amidato complexes.     

A new polymorphic form of bis(acetato‐κO)bis[2‐(pyridin‐2‐yl)ethanol‐κ2N,O]nickel(II)

A new polymorph of a mononuclear nickel(II) acetate complex with 2‐(pyridin‐2‐yl)ethanol ligands, [Ni(CH₃COO)₂(C₇H₉NO)₂], has been prepared and structurally characterized. Its molecular structure resembles the structures of two previously reported polymorphs in that the Ni^II atom is located on an inversion centre and is coordinated by pairs of acetate and 2‐(pyridin‐2‐yl)ethanol ligands. The acetate anions are coordinated in a monodentate manner, while the 2‐(pyridin‐2‐yl)ethanol ligands are coordinated in a bidentate chelating mode involving the endocyclic N atom and the hydroxy O atom of the ligand side chain. A strong bifurcated intramolecular hydrogen‐bond interaction was observed involving the hydroxy O atom as donor and both acetate O atoms as acceptors. No classical intermolecular hydrogen‐bond contacts were observed. However, the crystal packing is effected through π–π and C—H...π interactions, giving rise to a different packing arrangement. A brief comparison of the three polymorphic forms is presented.     

New Dinuclear Ru2(CO)4 Sawhorse‐Type Complexes Containing Bridging Carboxylato Ligands

The thermal reaction of Ru₃(CO)₁₂ with ethacrynic acid, 4‐[bis(2‐chlorethyl)amino]benzenebutanoic acid (chlorambucil), or 4‐phenylbutyric acid in refluxing solvents, followed by addition of two‐electron donor ligands (L), gives the diruthenium complexes Ru₂(CO)₄(O₂CR)₂L₂ ( 1 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = C₅H₅N; 2 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = PPh₃; 3 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = C₅H₅N; 4 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = PPh₃; 5 : R = C₃H₆‐C₆H₅, L = C₅H₅N; 6 : R = C₃H₆‐C₆H₅, L = PPh₃). The single‐crystal structure analyses of 2 , 3 , 5 and 6 reveal a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two L ligands occupy the axial positions of the diruthenium unit.     

Poly[bis{μ2‐4‐[3,5‐bis(pyridin‐4‐yl)phenyl]pyridine}nona‐μ2‐oxido‐tetraoxidocopper(II)tetramolybdenum(VI)]

The title compound, [CuMo₄O₁₃(C₂₁H₁₅N₃)₂]_n, was synthesized by the reaction of ammonium molybdate, copper acetate and 4‐[3,5‐bis(pyridin‐4‐yl)phenyl]pyridine (DPPP) in an aqueous medium under hydrothermal conditions. The two unique molybdenum centers and the copper center adopt MoO₄ tetrahedral, MoO₅N octahedral and CuO₄N₂ octahedral geometries, respectively. These polyhedra are connected to each other through corner‐sharing to form a two‐dimensional Cu–Mo–O layer, which is further linked by the DPPP ligands to form the three‐dimensional inorganic–organic hybrid framework.     

Metal–Ligand Cooperation on a Diruthenium Platform: Selective Imine Formation through Acceptorless Dehydrogenative Coupling of Alcohols with Amines

Metal?metal singly‐bonded diruthenium complexes, bridged by naphthyridine‐functionalized N‐heterocyclic carbene (NHC) ligands featuring a hydroxy appendage on the naphthyridine unit, are obtained in a single‐pot reaction of [Ru₂(CH₃COO)₂(CO)₄] with 1‐benzyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (BIN ? HBr) or 1‐isopropyl‐3‐(5,7‐dimethyl‐1,8‐naphthyrid‐2‐yl)imidazolium bromide (PIN ? HBr), TlBF₄, and substituted benzaldehyde containing an electron‐withdrawing group. The modified NHC‐naphthyridine‐hydroxy ligand spans the diruthenium unit in which the NHC carbon and hydroxy oxygen occupy the axial sites. All the synthesized compounds catalyze acceptorless dehydrogenation of alcohols to the corresponding aldehydes in the presence of a catalytic amount of weak base 1,4‐diazabicyclo[2.2.2]octane (DABCO). Further, acceptorless dehydrogenative coupling (ADHC) of the alcohol with amines affords the corresponding imine as the sole product. The substrate scope is examined with 1 (BIN, p‐nitrobenzaldehyde). A similar complex [Ru₂(CO)₄(CH₃COO)(3‐PhBIN)][Br], that is devoid of a hydroxy arm, is significantly less effective for the same reaction. Neutral complex 1 a , obtained by deprotonation of the hydroxy arm in 1 , is found to be active for the ADHC of alcohols and amines under base‐free conditions. A combination of control experiments, deuterium labeling, kinetic Hammett studies, and DFT calculations support metal–hydroxyl/hydroxide and metal–metal cooperation for alcohol activation and dehydrogenation. The bridging acetate plays a crucial role in allowing β‐hydride elimination to occur. The ligand architecture on the diruthenium core causes rapid aldehyde extrusion from the metal coordination sphere, which is responsible for exclusive imine formation.     

Tetra‐μ‐acetato‐κ8O:O′‐bis[(N1,N2‐di‐p‐anisylformamidine‐κN2)ruthenium(II)](Ru—Ru): an example of an axial bis‐adduct of {Ru2}4+ tetracarboxyl­ate with N‐donor ligands

The title compound, [Ru₂(C₂H₃O₂)₄(C₁₅H₁₆N₂O₂)₂], lies on a crystallographic inversion center and exhibits an Ru—Ru bond length of 2.2847 (8) Å. There are weak intramolecular hydrogen‐bonding interactions between the N¹,N²‐di‐p‐anisylformamidine (HDAniF) ligands and the bridging acetate ligands. The molecule is one of the few examples of a crystallographically characterized axial bis‐adduct of a {Ru₂}⁴⁺ complex with two N‐donor ligands.     

A novel octanuclear nickel(II)–molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand

Salicylhydroxamic acid (H₃shi) is known for its strong coordination ability and multiple coordination modes, and can easily coordinate to metal cations to form compounds with five‐ or six‐membered rings, as well as mono‐, di‐ and multinuclear compounds with interesting structures having potential applications in organic chemistry, coordination chemistry, and the materials and biological sciences. A novel octanuclear nickel(II)–molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand, namely di‐μ₃‐acetato‐di‐μ₂‐acetato‐di‐μ₃‐hydroxido‐di‐μ₃‐oxido‐tetraoxidooctakis(pyridine‐κN)bis(μ₅‐salicylhydroxamato)hexanickel(II)dimolybdenum(VI) monohydrate, [Mo₂Ni₆(C₇H₄NO₃)₂(C₂H₃O₂)₄O₅(OH)₂(C₅H₅N)₈]·H₂O, (I), was synthesized by the reaction of sodium molybdate, nickel acetate and salicylhydroxamic acid in a dimethylformamide/pyridine/methanol solution at room temperature. The salicylhydroxamate(3−) (shi³⁻), acetate and oxide ligands adopt complicated coordination modes and link six Ni^II and two Mo^VI cations into the octanuclear heterometallic cluster. All of the metal cations exhibit octahedral coordination geometries and are connected to each other through the sharing of corners, edges or planes. The heterometallic clusters are further connected to form two‐dimensional supramolecular layers through weak C—H…O hydrogen bonds. Studies of the magnetic properties of the title compound reveal antiferromagnetic interactions between the Ni^II cations.     

[Hg2(μ‐bpe)(μ‐OAc)2(μ‐SCN)2]n,a New Two‐Dimensional Coordination Polymer Involving Three Simultaneously Bridging Ligands: 1,2‐Bis(4‐pyridyle)ethene,Acetate, and Thiocyanate

A new mercury(II) complex of 1,2‐bis(4‐pyridyle)ethene (bpe) with anionic acetate and thiocyanate ligands has been synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. The single crystal X‐ray analysis shows that the complex is a two‐dimensional polymer with simultaneously bridging 1,2‐bis(4‐pyridyle)ethane, acetate and thiocyanate ligands and basic repeating dimeric [Hg₂(μ‐bpe)(μ‐OAc)₂(μ‐SCN)₂] units. The two‐dimensional system forms a three‐dimensional network by packing via π‐π stacking interactions.     

[Ba6(C2H3O2)12(H2O)3.5], a new hydrate of barium acetate

A new barium acetate phase, di‐μ₅‐acetato‐tri‐μ₄‐acetato‐tri‐μ₃‐acetato‐tri‐μ₂‐acetato‐μ₂‐acetato‐triaquahemiaquahexabarium(II), of analytical formula [Ba₆(C₂H₃O₂)₁₂(H₂O)_3.5], is described. The asymmetric unit contains six independent Ba centres with coordination numbers varying from 7 to 10 arising from bonding to 12 crystallographically independent acetate ligands and four molecules of water, one of which is disordered over two sites both of occupancy 0.5. Bonding to the acetate ligands creates a completely connected three‐dimensional structure. All H atoms of the water molecules participate in hydrogen bonding.     

High‐temperature phase of trans‐tetra­aqua­bis­(tri­fluoro­acetato‐O)­manganese(II)

The title compound, [Mn(CF₃COO)₂(H₂O)₄], crystallizes in the monoclinic space group C2/c. At about 215 K, it undergoes a reversible phase transition, which leads to crystal twinning. The crystal structure of the high‐temperature phase was determined at 220 K. The Mn²⁺ ion lies on a twofold axis and is octahedrally coordinated by two monodentate tri­fluoro­acetate ligands in apical positions and by four equatorial aqua ligands, two of which lie on the twofold axis. Hydro­gen‐bonding interactions connect the complex mol­ecules, generating a three–dimensional network.     

Conformation‐Determined Through‐Bond versus Through‐Space Electronic Communication in Mixed‐Valence Systems with a Cross‐Conjugated Urea Bridge

Bis‐triarylamine 2 and cyclometalated diruthenium 6 (PF₆)₂ with a linear trans,trans‐urea bridge have been prepared, together with the bis‐triarylamine 3 and cyclometalated diruthenium 8 (PF₆)₂ with a folded cis,cis‐N,N‐dimethylurea bridge. The linear or folded conformations of these molecules are supported by single‐crystal X‐ray structures of 2 , 3 , and other related compounds. These compounds display two consecutive anodic redox waves (N ^{. +/0} or Ru^III/II processes) with a potential separation of 110–170 mV. This suggests that an efficient electronic coupling is present between two redox termini through the cross‐conjugated urea bridge. The degree of electronic coupling has been investigated by using spectroelectrochemical measurements. Distinct intervalence charge‐transfer (IVCT) transitions have been observed for mixed‐valent (MV) compounds with a linear conformation. The IVCT transitions can also be identified for the folded MV compounds, albeit with a much weaker intensity. DFT results support that the electronic communication occurs by a through‐bond and through‐space pathway for the linear and folded compounds, respectively. The IVCT transitions of the MV compounds have been reproduced by TDDFT calculations. For the purpose of comparison, a bistriarylamine and a diruthenium complex with an imidazolidin‐2‐one bridge and a urea‐containing mono‐triarylamine and monoruthenium complex have been synthesized and studied.     

Acid-Base Interactions of Pyrazine,Ethyl Acetate,Di-alcohols,and Lysine with the cyclic Alumosiloxane (Ph2SiO)8[Al(O)OH]4 in View of Mimicking Al2O3(H2O) Surface Reactions

The etherate of (Ph₂SiO)₈[Al(O)OH]₄ can be transformed into the pyrazine adduct (Ph₂SiO)₈[Al(O)OH]₄ · 3N(C₂H₂)₂N ( 1 ), the ethyl acetate adduct (Ph₂SiO)₈[Al(O)OH]₄ · 3H₃C-C(O)OC₂H₅ ( 2 ), the 1,6-hexane diol adduct (Ph₂SiO)₈[Al(O)OH]₄ · 2HO–CH₂(CH₂)₄CH₂–OH ( 3 ) and the 1,4-cyclohexane diol adduct (Ph₂SiO)₈[Al(O)OH]₄ · 4HO–CH(CH₂CH₂)₂CH–OH ( 4 ). In all compounds the OH groups of the starting material bind to the bases through O–H ··· N ( 1 ) or O–H ··· O hydrogen bonds ( 2 , 3 , 4 ) as found from single-crystal X-ray diffraction analyses. Whereas in 1 only three of the central OH groups bind to the pyrazines, in 2 two of them bind to the same carbonyl oxygen atom of the ethyl acetate resulting in an unprecedented O–H ··· O ··· H–O double hydrogen bridge. The hexane diol adduct 3 in the crystal forms a one-dimensional coordination polymer with an intramolecularly to two OH groups grafted hexane diol loop, while the second hexane diol is connecting intermolecularly. In the cyclohexane diol adduct 4 all OH groups of the central Al₄(OH)₄ ring bind to different diols, leaving one alcohol group per diol uncoordinated. These “free” OH groups form an (O-H ··· )₄ assembly creating a three-dimensional overall structure. When reacting with (Ph₂SiO)₈[Al(O)OH]₄ lysine loses water, turns into the cyclic 3-amino-2-azepanone, and transforms through chelation of one of the aluminum atoms the starting material into a new polycycle. The isolated compound has the composition (Ph₂SiO)₁₂[Al(O)OH]₄[Al₂O₃]₂ · 4 C₆H₁₂N₂O · 6(CH₂)₄O ( 5 ).     

Study of the Interaction of Bis(4‐pyridylthio)methane with Copper(II) Chloride and Bromide

The new ligand bis(4‐pyridylthio)methane (4‐bpytm) ( 1 ) and its complexes [CuX₂(4‐bpytm)] and [CuX₂(4‐bpytm)₂] (X = Cl and Br) ( 2 – 5 ) have been prepared and characterized by elemental analysis, IR‐Raman, UV/Vis spectroscopy. The structures of (4‐bpytm) ( 1 ), [CuCl₂(4‐bpytm)₂] ( 3 ) and [CuBr₂(4‐bpytm)₂] ( 4 ) were determined by single‐crystal X‐ray diffraction analysis. X‐ray analysis of the 1:2 derivatives reveals that the copper atom has a distorted (4 + 2) octahedral environment. The copper atom is coordinated by four nitrogen atoms from four bridging 4‐bpytm ligands and two halogen atoms. The axial Cu–N bonds are considerably longer than the equatorial Cu–N bonds owing to JahñTeller distortion. CuX₂ units are linked to each other through bridging 4‐bpytm ligands to form a 2D interpenetrated coordination polymer. The structural parameters of the 4‐bpytm ligand in these complexes were compared with those of the free ligand.     

Mapping the Transformation [{RuII(CO)3Cl2}2]→[RuI2(CO)4]2+: Implications in Binuclear Water–Gas Shift Chemistry

The complete sequence of reactions in the base‐promoted reduction of [{Ru^II(CO)₃Cl₂}₂] to [Ru^I₂(CO)₄]²⁺ has been unraveled. Several μ‐OH, μ:κ²‐CO₂H‐bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal‐coordinated carbonyls by hydroxides. The isolated compounds are [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐OH)(NP^F‐Am)₂][PF₆] ( 1 ; NP^F‐Am=2‐amino‐5,7‐trifluoromethyl‐1,8‐naphthyridine) and [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)(μ‐OH)(NP‐Me₂)₂][BF₄]₂ ( 2 ), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru₄(CO)₈(H₂O)₂(μ³‐OH)₂(μ:κ²‐C,O‐CO₂H)₄][CF₃SO₃]₂ ( 3 ) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a π‐donor chlorido ligand, which results in [Ru₂(CO)₄(μ:κ²‐C,O‐CO₂H)₂(μ‐Cl)(NP‐PhOMe)₂][BF₄] ( 4 ). The production of [Ru₂(CO)₄]²⁺ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl)–diruthenium(II) complex to a dihydrido–diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the Ru^I? Ru^I single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru₂(CO)₄(CH₃CN)₆]²⁺ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by Tl^I salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear Ru^I₂Ru^II complex [{Ru(NP‐Am)₂(CO)}{Ru₂(NP‐Am)₂(CO)₂(μ‐CO)₂}(μ₃:κ³‐C,O,O′‐CO₂)][BF₄]₂ ( 6 ). These unprecedented diruthenium compounds are the dinuclear congeners of the water–gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry.     

μ‐Acetato‐1:2κ2O:O′‐diacetato‐1κ2O,O′;2κO‐bis(di‐2‐pyridylamine)‐1κ2N,N′;2κ2N,N′‐isothiocyanato‐2κN‐dicopper(II)

In the title dinuclear acetate‐bridged complex, [Cu₂(C₂H₃O₂)₃(NCS)(C₁₀H₉N₃)₂], the two Cu atoms are five‐coordinated, with a basal plane consisting of two N atoms of a di‐2‐pyridylamine (dpyam) ligand and two O atoms of two different acetate ligands. The axial positions of these Cu atoms are coordinated to N and O atoms from thio­cyanate and acetate mol­ecules, respectively, leading to a distorted square‐pyramidal geometry with τ values of 0.30 and 0.22. Both Cu^II ions are linked by an acetate group in the equatorial–equatorial positions and have syn–anti bridging configurations. Hydrogen‐bond inter­actions between the amine H atom and the coordinated and uncoordinated O atoms of the acetate anions generate an infinite one‐dimensional chain.     

Synthesis,crystal structure and magnetic properties of (acetato‐κ2O,O′)bis(5,5′‐dimethyl‐2,2′‐bipyridine‐κ2N,N′)nickel(II) perchlorate monohydrate

The title hydrated ionic complex, [Ni(CH₃COO)(C₁₂H₁₂N₂)₂]ClO₄·H₂O or [Ni(ac)(5,5′‐dmbpy)₂]ClO₄·H₂O (where 5,5′‐dmbpy is 5,5′‐dimethyl‐2,2′‐bipyridine and ac is acetate), (1), was isolated as violet crystals from the aqueous ethanolic nickel acetate–5,5′‐dmbpy–KClO₄ system. Within the complex cation, the Ni^II atom is hexacoordinated by two chelating 5,5′‐dmbpy ligands and one chelating ac ligand. The mean Ni—N and Ni—O bond lengths are 2.0628 (17) and 2.1341 (15) Å, respectively. The water solvent molecule is disordered over two partially occupied positions and links two complex cations and two perchlorate anions into hydrogen‐bonded centrosymmetric dimers, which are further connected by π–π interactions. The magnetic properties of (1) at low temperatures are governed by the action of single‐ion anisotropy, D, which arises from the reduced local symmetry of the cis‐NiO₂N₄ chromophore. The fitting of the variable‐temperature magnetic data (2–300 K) gives g_iso = 2.134 and D/hc = 3.13 cm⁻¹.