Formation,Expansion, and Interconversion of Metallarings in a Sulfur‐Bridged AuICoIII Coordination System

A novel Au^ICo^III coordination system that is derived from the newly prepared [Co(D ‐nmp)₂]^? ( 1 ^?; D ‐nmp=N‐methyl‐D ‐penicillaminate) and a gold(I) precursor Au^I is reported. Complex 1 ^? acts as a sulfur‐donating metallaligand and reacts with the gold(I) precursor to give [Au₂Co₂(D ‐nmp)₄] ( 2 ), which has an eight‐membered Au^I₂Co^III₂ metallaring. Treatment of 2 with [Au₂(dppe)₂]²⁺ (dppe=1,2‐bis(diphenylphosphino)ethane) leads to the formation of [Au₄Co₂(dppe)₂(D ‐nmp)₄]²⁺ ( 3 ²⁺), which consists of an 18‐membered Au^I₄Co^III₂ metallaring that accommodates a tetrahedral anion (BF₄^?, ClO₄^?, ReO₄^?). In solution, the metallaring structure of 3 ²⁺ is readily interconvertible with the nine‐membered Au^I₂Co^III metallaring structure of [Au₂Co(dppe)(D ‐nmp)₂]⁺ ( 4 ⁺); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au? S and Au? P bonds, which is essential for metallaring expansion and contraction.     

Formation,Expansion, and Interconversion of Metallarings in a Sulfur‐Bridged AuICoIII Coordination System

A novel Au^ICo^III coordination system that is derived from the newly prepared [Co(D ‐nmp)₂]⁻ ( 1 ⁻; D ‐nmp=N‐methyl‐D ‐penicillaminate) and a gold(I) precursor Au^I is reported. Complex 1 ⁻ acts as a sulfur‐donating metallaligand and reacts with the gold(I) precursor to give [Au₂Co₂(D ‐nmp)₄] ( 2 ), which has an eight‐membered Au^I₂Co^III₂ metallaring. Treatment of 2 with [Au₂(dppe)₂]²⁺ (dppe=1,2‐bis(diphenylphosphino)ethane) leads to the formation of [Au₄Co₂(dppe)₂(D ‐nmp)₄]²⁺ ( 3 ²⁺), which consists of an 18‐membered Au^I₄Co^III₂ metallaring that accommodates a tetrahedral anion (BF₄⁻, ClO₄⁻, ReO₄⁻). In solution, the metallaring structure of 3 ²⁺ is readily interconvertible with the nine‐membered Au^I₂Co^III metallaring structure of [Au₂Co(dppe)(D ‐nmp)₂]⁺ ( 4 ⁺); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au S and Au P bonds, which is essential for metallaring expansion and contraction.     

[AuII([12]anS4)]2+ – X‐ und Q‐Band‐EPR‐spektroskopischer Nachweis einer neuen monomeren Gold(II)‐Verbindung

[Au^II([12]anS₄)]²⁺ – X‐ and Q‐Band EPR Evidence of a New Monomeric Gold(II) Compound The reaction of [Au^IIICl₄]^– with the thiacrown ether [12]aneS₄ leads to an instable [Au^II([12]anS₄)]²⁺ complex (5d⁹, S = 1/2) which was characterized by X‐ and Q‐ band EPR. The spin Hamiltonian parameters g , A ^Au and P ^Au were derived using a program package allowing an exact diagonalisation of the spin‐Hamiltonian‐Matrix. The EPR parameters suggest the coordination of only one thiacrown ether ligand in the new Au^II complex.     

Ring‐to‐Cage Structural Conversion via Template Effect in a Gold(I) Metallosupramolecular System

A unique example of a ring‐to‐cage structural conversion in a multinuclear gold(I) coordination system with d ‐penicillamine (d ‐H₂pen) is reported. The reaction of [Au₂Cl₂(dppe)] (dppe=1,2‐bis(diphenylphosphino)ethane) with d ‐H₂pen in a 1:1 ratio gave [Au₄(dppe)₂(d ‐pen)₂] ([ 1 ]), in which two [Au₂(dppe)]²⁺ units are linked by two d ‐pen S atoms in a cyclic form so as to have two bidentate‐N,O coordination arms. The subsequent reaction of [ 1 ] with Cu(OTf)₂ afforded [Au₄Cu(dppe)₂(d ‐pen)₂]²⁺ ([ 2 ]²⁺), in which a Cu^II ion is chelated by the two coordination arms in [ 1 ] to form an Au^I₄Cu^II bicyclic metallocage. A similar reaction using Cu(NO₃)₂ was accompanied by the ring expansion of [ 1 ] to [Au₈(dppe)₄(d ‐pen)₄], leading to the production of [Au₈Cu₂(dppe)₄(d ‐pen)₄]⁴⁺ ([ 3 ]⁴⁺). In [ 3 ]⁴⁺, two Cu^II ions are each chelated by the two coordination arms to form an Au^I₈Cu^II₂ tricyclic metallocage, accommodating a nitrate ion. The use of Ni(NO₃)₂ or Ni(OAc)₂ instead of Cu(NO₃)₂ commonly gave a tricyclic metallocage of [Au₈Ni₂(dppe)₄(d ‐pen)₄]⁴⁺ ([ 4 ]⁴⁺), but a water molecule was accommodated inside the Au^I₈Ni^II₂ metallocage.     

EPR‐spektroskopische Charakterisierung (X‐, Q‐Band) monomerer AgII‐ und AuII‐Komplexe der Thiakronenether [12]anS4, [16]anS4, [18]anS6 und [27]anS9

EPR Spectroscopic Characterization (X‐, Q‐Band) of Monomeric Ag^II‐ and Au^II‐Complexes of the Thiacrownethers [12]aneS₄, [16]aneS₄, [18]aneS₆ and [27]aneS₉ The reaction of the prepared Ag^I complexes of the thiacrownethers [12]aneS₄, [16]aneS₄, [18]aneS₆ and [27]aneS₉ with c. H₂SO₄ as well as the reaction of [Au^IIICl₄]^‐ with [18]aneS₆ and [27]aneS₉ leads to labile Ag^II‐ (4d⁹, ^{107, 109}Ag: I=1/2) and Au^II‐ (5d⁹, ¹⁹⁷Au: I=3/2) thiacrownether complexes, respectively, which were characterized by X‐ and Q‐band EPR. The EPR spectra of [Ag^II([12]anS₄)]²⁺ and [Ag^II([18]anS₆)]²⁺ were reinvestigated. According to an analysis of the spin‐density distribution only 20 ‐ 25 % is located on the Ag or Au atoms. Most of the spin‐density was found to be on the S donor atoms of the thiacrownethers. The high delocalization of the spin‐density leads certainly to a noticeable reduction of the Ag^I/Ag^II redox potential and is considered as being mainly responsible for the easy accessibility of the Ag^II compounds.     

Ruthenium(II/III)‐Based Compounds with Encouraging Antiproliferative Activity against Non‐small‐Cell Lung Cancer

Hereby we present the synthesis of several ruthenium(II) and ruthenium(III) dithiocarbamato complexes. Proceeding from the Na[trans‐Ru^III(dmso)₂Cl₄] ( 2 ) and cis‐[Ru^II(dmso)₄Cl₂] ( 3 ) precursors, the diamagnetic, mixed‐ligand [Ru^IIL₂(dmso)₂] complexes 4 and 5 , the paramagnetic, neutral [Ru^IIIL₃] monomers 6 and 7 , the antiferromagnetically coupled ionic α‐[Ru^III₂L₅]Cl complexes 8 and 9 as well as the β‐[Ru^III₂L₅]Cl dinuclear species 10 and 11 (L=dimethyl‐ (DMDT) and pyrrolidinedithiocarbamate (PDT)) were obtained. All the compounds were fully characterised by elemental analysis as well as ¹H NMR and FTIR spectroscopy. Moreover, for the first time the crystal structures of the dinuclear β‐[Ru^III₂(dmdt)₅]BF₄ ? CHCl₃ ? CH₃CN and of the novel [Ru^IIL₂(dmso)₂] complexes were also determined and discussed. For both the mono‐ and dinuclear Ru^II and Ru^III complexes the central metal atoms assume a distorted octahedral geometry. Furthermore, in vitro cytotoxicity of the complexes has been evaluated on non‐small‐cell lung cancer (NSCLC) NCI‐H1975 cells. All the mono‐ and dinuclear Ru^III dithiocarbamato compounds (i.e., complexes 6 – 10 ) show interesting cytotoxic activity, up to one order of magnitude higher with respect to cisplatin. Otherwise, no significant antiproliferative effect for either the precursors 2 and 3 or the Ru^II complexes 4 and 5 has been observed.     

(n‐Bu4N)2[Au(mnt)2]: Synthese,Struktur‐ und EPR‐Untersuchungen eines stabilen,mononuklearen AuII‐Komplexes

The reaction of [Au^III(mnt)₂]^? with (n‐Bu₄N)[BH₄] in acetone leads to the formation of [Au^II(mnt)₂]^2?, which is the second stable mononuclear Au^II complex characterized by X‐ray structure analysis. (n‐Bu₄N)₂[Au^II(mnt)₂] crystallizes triclinic, P (a = 904.24(5), b = 989.55(5), c = 1627.35(10) pm, α = 92.040(7), β = 94.937(7), γ = 107.220(6)°, Z = 1) with two molecules acetone per unit cell. The anion is planar. From EPR investigations using single crystals of (n‐Bu₄N)₂[Au^II(mnt)₂] the g tensor components were derived. Information about magnetic exchange interactions were obtained from line width analyses.     

Entrapment of a Pseudo‐Tetrahedral CoII Center by Thioether Sulfur Bound {Co2(μ‐L)} Fragments: Synthesis,Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity

Simultaneous incorporation of both Co^II and Co^III ions within a new thioether S‐bearing phenol‐based ligand system, H₃L (2,6‐bis‐[{2‐(2‐hydroxyethylthio)ethylimino}methyl]‐4‐methylphenol) formed [Co₅] aggregates [Co^IICo^III₄L₂(μ‐OH)₂(μ_1,3‐O₂CCH₃)₂](ClO₄)₄?H₂O ( 1 ) and [Co^IICo^III₄L₂(μ‐OH)₂(μ_1,3‐O₂CC₂H₅)₂](ClO₄)₄?H₂O ( 2 ). The magnetic studies revealed axial zero‐field splitting (ZFS) parameter, D/hc=?23.6 and ?24.3 cm^?1, and E/D=0.03 and 0.00, respectively for 1 and 2 . Dynamic magnetic data confirmed the complexes as SIMs with U_eff/k_B=30 K ( 1 ) and 33 K ( 2 ), and τ₀=9.1×10^?8 s ( 1 ), and 4.3×10^?8 s ( 2 ). The larger atomic radius of S compared to N gave rise to less variation in the distortion of tetrahedral geometry around central Co^II centers, thus affecting the D and U_eff/k_B values. Theoretical studies also support the experimental findings and reveal the origin of the anisotropy parameters. In solutions, both 1 and 2 which produce {Co^III₂(μ‐L)} units, display solvent‐dependent catechol oxidation behavior toward 3,5‐di‐tert‐butylcatechol in air. The presence of an adjacent Co^III ion tends to assist the electron transfer from the substrate to the metal ion center, enhancing the catalytic oxidation rate.     

An Extremely Porous Hydrogen‐Bonded Framework Composed of d‐Penicillaminato CoIII2AuI3 Complex Anions and Aqua Cobalt(II) Cations: Formation and Stepwise Structural Transformation

A unique example of a hydrogen‐bonded ionic solid with a porosity of 80 %, [Co(H₂O)₆]₃[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 1 ; d ‐H₂pen=d ‐penicillamine), composed of [Co(H₂O)₆]²⁺ cations and [Co₂Au₃(d ‐pen‐N,S)₆]^3? anions, is reported. Solid 1 was kinetically produced and was then transformed stepwise into two more thermodynamically stable solids with lower porosities, [Co(H₂O)₄][Co(H₂O)₆]₂[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 2 ) and [Co(H₂O)₄]₃[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 3 ), through the coordination of the free carboxylate groups in [Co₂Au₃(d ‐pen‐N,S)₆]^3? to Co^II centers. Solids 1 – 3 were structurally characterized, and the selective adsorption of small molecules into their pores was investigated.     

A charge-separation-type ionic solid composed of hexanuclear complexes with a macrocyclic tetragold(I) metalloligand

The reaction of Na[Co^III(d -ebp)] (d -H₄ebp = N,N′-ethylenebis[d -penicillamine]) with [(Au^ICl)₂(dppe)] (dppe = 1,2-bis[diphenylphosphino]ethane) gave a cationic Au^I₄Co^III₂ hexanuclear complex, [Co^III₂(L^Au4)]²⁺ ([ 1 ]²⁺), where [L^Au4]⁴⁻ is a cyclic tetragold(I) metalloligand with a 32-membered ring, [Au^I₄(dppe)₂(d -ebp)₂]⁴⁻. Complex [ 1 ]²⁺ crystallized with NO₃⁻ to produce a charge-separation (CS)-type ionic solid of [ 1 ](NO₃)₂. In [ 1 ](NO₃)₂, the complex cations are assembled to form cationic supramolecular hexamers of {[ 1 ]²⁺}₆, which are closely packed in a face-centered cubic (fcc) lattice structure. The nitrate anions of [ 1 ](NO₃)₂ were accommodated in hydrophilic and hydrophobic tetrahedral interstices of the fcc structure to form tetrameric and hexameric nitrate clusters of {NO₃⁻}₄ and {NO₃⁻}₆, respectively. An analogous CS-type ionic solid formulated as [Ni^IICo^III(L^Au4)](NO₃) ([ 2 ](NO₃)) was obtained when a 1:1 mixture of Na[Co^III(d -ebp)] and [Ni^II(d -H₂ebp)] was reacted with [(Au^ICl)₂(dppe)], accompanied by the conversion of the diamagnetic, square-planar [Ni^II(d -H₂ebp)] to the paramagnetic, octahedral [Ni^II(d -ebp)]²⁻. While the overall fcc structure in [ 2 ](NO₃) was similar to that of [ 1 ](NO₃)₂, none of the nitrate anions were accommodated in any hydrophobic tetrahedral interstice, reflecting the difference in the complex charges between [ 1 ]²⁺ and [ 2 ]⁺.     

Luminescent Di‐ and Polynuclear Organometallic Gold(I)–Metal (Au2, {Au2Ag}n and {Au2Cu}n) Compounds Containing Bidentate Phosphanes as Active Antimicrobial Agents

The reaction of new dinuclear gold(I) organometallic complexes containing mesityl ligands and bridging bidentate phosphanes [Au₂(mes)₂(μ‐LL)] (LL=dppe: 1,2‐bis(diphenylphosphano)ethane 1 a , and water‐soluble dppy: 1,2‐bis(di‐3‐pyridylphosphano)ethane 1 b ) with Ag⁺ and Cu⁺ lead to the formation of a family of heterometallic clusters with mesityl bridging ligands of the general formula [Au₂M(μ‐mes)₂(μ‐LL)][A] (M=Ag, A=ClO₄^?, LL=dppe 2 a , dppy 2 b ; M=Ag, A=SO₃CF₃^?, LL=dppe 3 a , dppy 3 b ; M=Cu, A=PF₆^?, LL=dppe 4 a , dppy 4 b ). The new compounds were characterized by different spectroscopic techniques and mass spectrometry The crystal structures of [Au₂(mes)₂(μ‐dppy)] ( 1 b ) and [Au₂Ag(μ‐mes)₂(μ‐dppe)][SO₃CF₃] ( 3 a ) were determined by a single‐crystal X‐ray diffraction study. 3 a in solid state is not a cyclic trinuclear Au₂Ag derivative but it gives an open polymeric structure instead, with the {Au₂(μ‐dppe)} fragments “linked” by {Ag(μ‐mes)₂} units. The very short distances of 2.7559(6) Å (Au? Ag) and 2.9229(8) Å (Au? Au) are indicative of gold–silver (metallophilic) and aurophilic interactions. A systematic study of their luminescence properties revealed that all compounds are brightly luminescent in solid state, at room temperature (RT) and at 77 K, or in frozen DMSO solutions with lifetimes in the microsecond range and probably due to the self‐aggregation of [Au₂M(μ‐mes)₂(μ‐LL)]⁺ units (M=Ag or Cu; LL=dppe or dppy) into an extended chain structure, through Au? Au and/or Au? M metallophilic interactions, as that observed for 3 a . In solid state the heterometallic Au₂M complexes with dppe ( 2 a – 4 a ) show a shift of emission maxima (from ca. 430 to the range of 520‐540 nm) as compared to the parent dinuclear organometallic product 1 a while the complexes with dppy ( 2 b–4 b ) display a more moderate shift (505 for 1 b to a max of 563 nm for 4 b ). More importantly, compound [Au₂Ag(μ‐mes)₂(μ‐dppy)]ClO₄ ( 2 b ) resulted luminescent in diluted DMSO solution at room temperature. Previously reported compound [Au₂Cl₂(μ‐LL)] (LL dppy 5 b ) was also studied for comparative purposes. The antimicrobial activity of 1–5 and Ag[A] (A=ClO₄^?, SO₃CF₃^?) against Gram‐positive and Gram‐negative bacteria and yeast was evaluated. Most tested compounds displayed moderate to high antibacterial activity while heteronuclear Au₂M derivatives with dppe ( 2 a – 4 a ) were the more active (minimum inhibitory concentration 10 to 1 μg mL^?1). Compounds containing silver were ten times more active to Gram‐negative bacteria than the parent dinuclear compound 1 a or silver salts. Au₂Ag compounds with dppy ( 2 b , 3 b ) were also potent against fungi.     

Influence of Central Metalloligand Geometry on Electronic Communication between Metals: Syntheses,Crystal Structures,MMCT Properties of Isomeric Cyanido‐Bridged Fe2Ru Complexes,and TDDFT Calculations

To investigate how the central metalloligand geometry influences distant or vicinal metal‐to‐metal charge‐transfer (MMCT) properties of polynuclear complexes, cis‐ and trans‐isomeric heterotrimetallic complexes, and their one‐ and two‐electron oxidation products, cis/trans‐ [Cp(dppe)Fe^IINCRu^II(phen)₂CN‐Fe^II(dppe)Cp][PF₆]₂ (cis/trans‐ 1 [PF₆]₂), cis/trans‐[Cp(dppe)Fe^IINCRu^II(phen)₂CNFe^III‐(dppe)Cp][PF₆]₃ (cis/trans‐ 1 [PF₆]₃) and cis/trans‐[Cp(dppe)Fe^IIINCRu^II(phen)₂CN‐Fe^III(dppe)Cp][PF₆]₄ (cis/trans‐ 1 [PF₆]₄) have been synthesized and characterized. Electrochemical measurements show the presence of electronic interactions between the two external Fe^II atoms of the cis‐ and trans‐isomeric complexes cis/trans‐ 1 [PF₆]₂. The electronic properties of all these complexes were studied and compared by spectroscopic techniques and TDDFT//DFT calculations. As expected, both mixed valence complexes cis/trans‐ 1 [PF₆]₃ exhibited different strong absorption signals in the NIR region, which should mainly be attributed to a transition from an MO that is delocalized over the Ru^II‐CN‐Fe^II subunit to a Fe^III d orbital with some contributions from the co‐ligands. Moreover, the NIR transition energy in trans‐ 1 [PF₆]₃ is lower than that in cis‐ 1 [PF₆]₃, which is related to the symmetry of their molecular orbitals on the basis of the molecular orbital analysis. Also, the electronic spectra of the two‐electron oxidized complexes show that trans‐ 1 [PF₆]₄ possesses lower vicinal Ru^II→Fe^III MMCT transition energy than cis‐ 1 [PF₆]₄. Moreover, the assignment of MMCT transition of the oxidized products and the differences of the electronic properties between the cis and trans complexes can be well rationalized using TDDFT//DFT calculations.     

Spontaneous Reduction of Mononuclear High‐Spin Iron(III) Complexes to Mononuclear Low‐Spin Iron(II) Complexes in Aqueous Media and Nuclease Activity via Self‐Activation

Mononuclear high‐spin [Fe^III(Pyimpy)Cl₃]?2 CH₂Cl₂ ( 1 ?2 CH₂Cl₂) and [Fe^III(Me‐Pyimpy)Cl₃] ( 2 ), as well as low‐spin Fe^II(Pyimpy)₂](ClO₄)₂ ( 3 ) and [Fe^II(Me‐Pyimpy)₂](ClO₄)₂ ( 4 ) complexes of tridentate ligands Pyimpy and Me‐Pyimpy have been synthesized and characterized by analytical techniques, spectral, and X‐ray structural analyses. We observed an important type of conversion and associated spontaneous reduction of mono‐chelated high‐spin Fe^III ( 1 ?2 CH₂Cl₂ and 2 ) complexes to low‐spin bis‐chelated Fe^II complexes 3 and 4 , respectively. This process has been explored in detail by UV/Vis, fluorescence, and ¹H NMR spectroscopic measurements. The high positive potentials observed in electrochemical studies suggested a better stabilization of Fe^II centers in 3 and 4 . Theoretical studies by density functional theory (DFT) calculations supported an increased stabilization for 3 in polar solvents. Self‐activated nuclease activity of complexes 1 ?2CH₂Cl₂ and 2 during their spontaneous reduction was examined for the first time and the mechanism of nuclease activity was investigated.     

An Unusually Delocalized Mixed‐Valence State of a Cyanidometal‐Bridged Compound Induced by Thermal Electron Transfer

The heterometallic complexes trans ‐[Cp(dppe)FeNCRu(o ‐bpy)CNFe(dppe)Cp][PF₆]_n ( 1 [PF₆]_n , n =2, 3, 4; o ‐bpy=1,2‐bis(2,2′‐bipyridyl‐6‐yl)ethane, dppe=1,2‐bis(diphenylphosphino)ethane, Cp=1,3‐cyclopentadiene) in three distinct states have been synthesized and fully characterized. 1 ³⁺[PF₆]₃ and 1 ⁴⁺[PF₆]₄ are the one‐ and two‐electron oxidation products of 1 ²⁺[PF₆]₂, respectively. The investigated results suggest that 1 [PF₆]₃ is a Class II mixed valence compound. 1 [PF₆]₄ after a thermal treatment at 400 K shows an unusually delocalized mixed valence state of [Fe^III‐NC‐Ru^III‐CN‐Fe^II], which is induced by electron transfer from the central Ru^II to the terminal Fe^III in 1 [PF₆]₄, which was confirmed by IR spectroscopy, magnetic data, and EPR and Mössbauer spectroscopy.     

Heterotrimetallic Mixed‐Valent Molecular Precursors Containing Periodic Table Neighbors: Assignment of Metal Positions and Oxidation States

A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [Co^II(hfac)₃?Na?Co^III(acac)₃] ( 1 ). This was used as a template structure to develop heterotrimetallic molecules [Co^II(hfac)₃?Na?Fe^III(acac)₃] ( 2 ) and [Ni^II(hfac)₃?Na?Co^III(acac)₃] ( 3 ) via isovalent site‐specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple‐wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di‐ and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O₄ functional oxide materials.     

Three‐Dimensional Antiferromagnetic Order of Single‐Chain Magnets: A New Approach to Design Molecule‐Based Magnets

Two one‐dimensional compounds composed of a 1:1 ratio of Mn^III salen‐type complex and Ni^II oximato moiety with different counter anions, PF₆^? and BPh₄^?, were synthesized: [Mn(3,5‐Cl₂saltmen)Ni(pao)₂(phen)]PF₆ ( 1 ) and [Mn(5‐Clsaltmen)Ni(pao)₂(phen)]BPh₄ ( 2 ), where 3,5‐Cl₂saltmen^2?=N,N′‐(1,1,2,2‐tetramethylethylene)bis(3,5‐dichlorosalicylideneiminate); 5‐Clsaltmen^2?=N,N′‐(1,1,2,2‐tetramethylethylene)bis(5‐chlorosalicylideneiminate); pao^?=pyridine‐2‐aldoximate; and phen=1,10‐phenanthroline. Single‐crystal X‐ray diffraction study was carried out for both compounds. In 1 and 2 , the chain topology is very similar forming an alternating linear chain with a [‐Mn^III‐ON‐Ni^II‐NO‐] repeating motif (where ‐ON‐ is the oximate bridge). The use of a bulky counteranion, such as BPh₄^?, located between the chains in 2 rather than PF₆^? in 1 , successfully led to the magnetic isolation of the chains in 2 . This minimization of the interchain interactions allows the study of the intrinsic magnetic properties of the chains present in 1 and 2 . While 1 and 2 possess, as expected, very similar paramagnetic properties above 15 K, their ground state is antiferromagnetic below 9.4 K and paramagnetic down to 1.8 K, respectively. Nevertheless, both compounds exhibit a magnet‐type behavior at temperatures below 6 K. While for 2 , the observed magnetism is well explained by a Single‐Chain Magnet (SCM) behavior, the magnet properties for 1 are induced by the presence in the material of SCM building units that order antiferromagnetically. By controlling both intra‐ and interchain magnetic interactions in this new [Mn^IIINi^II] SCM system, a remarkable AF phase with a magnet‐type behavior has been stabilized in relation with the intrinsic SCM properties of the chains present in 1 . This result suggests that the simultaneous enhancement of both intrachain (J) and interchain (J′) magnetic interactions (with keeping J ? J′), independently of the presence of AF phase might be an efficient route to design high temperature SCM‐based magnets.     

Near‐IR Absorbing Ruthenium Complexes of Non‐Innocent 6,12‐Di(pyridin‐2‐yl)indolo[3,2‐b]carbazole: Variation as a Function of Co‐Ligands

This article deals with the hitherto unexplored metal complexes of deprotonated 6,12‐di(pyridin‐2‐yl)‐5,11‐dihydroindolo[3,2‐b]carbazole (H₂L). The synthesis and structural, optical, electrochemical characterization of dimeric [{Ru^III(acac)₂}₂(μ‐L^.?)]ClO₄ ([ 1 ]ClO₄, S=1/2), [{Ru^II(bpy)₂}₂(μ‐L^.?)](ClO₄)₃ ([ 2 ](ClO₄)₃, S=1/2), [{Ru^II(pap)₂}₂(μ‐L^2?)](ClO₄)₂ ([ 4 ](ClO₄)₂, S=0), and monomeric [(bpy)₂Ru^II(HL^?)]ClO₄ ([ 3 ]ClO₄, S=0), [(pap)₂Ru^II(HL^?)]ClO₄ ([ 5 ]ClO₄, S=0) (acac=σ‐donating acetylacetonate, bpy=moderately π‐accepting 2,2’‐bipyridine, pap=strongly π‐accepting 2‐phenylazopyridine) are reported. The radical and dianionic states of deprotonated L in isolated dimeric 1 ⁺/ 2 ³⁺ and 4 ²⁺, respectively, could be attributed to the varying electronic features of the ancillary (acac, bpy, and pap) ligands, as was reflected in their redox potentials. Perturbation of the energy level of the deprotonated L or HL upon coordination with {Ru(acac)₂}, {Ru(bpy)₂}, or {Ru(pap)₂} led to the smaller energy gap in the frontier molecular orbitals (FMO), resulting in bathochromically shifted NIR absorption bands (800–2000 nm) in the accessible redox states of the complexes, which varied to some extent as a function of the ancillary ligands. Spectroelectrochemical (UV/Vis/NIR, EPR) studies along with DFT/TD‐DFT calculations revealed (i) involvement of deprotonated L or HL in the oxidation processes owing to its redox non‐innocent potential and (ii) metal (Ru^III/Ru^II) or bpy/pap dominated reduction processes in 1 ⁺ or 2 ²⁺/ 3 ⁺/ 4 ²⁺/ 5 ⁺, respectively.     

pH‐Controlled Multiple Chiral Inversion That Induces Molecular Dimerization in a Gold(I)–Cobalt(III) Coordination System with L‐Cysteinate

Herein, a unique coordination system that exhibits multiple chiral inversions and molecular dimerization in response to a subtle pH change is reported. Treatment of (Δ)₂‐H₃[Au₃Co₂(L ‐cys)₆] (H₃[ 1 a ]) with [Co₃(aet)₆](NO₃)₃ (aet=2‐aminoethanethiolate) in water at pH 7 gave a 1:1 complex salt of [Co₃(aet)₆]³⁺ and [ 1 a ]^3?, retaining the Au^I₃Co^III₂ structure and chiral configurations of [ 1 a ]^3?. Similar treatment at pH 9 led to not only the inversion of all of the chiral Co^III and S centers but also the dimerization of [ 1 a ]^3?, giving a 2:1 complex salt of [Co₃(aet)₆]³⁺ and (Λ)₄(R)₁₂‐[Au₆Co₄(L ‐cys)₁₂]^6? ([ 2 ]^6?). When dissociated from [Co₃(aet)₆]³⁺ in solution, [ 2 ]^6? was converted to (Λ)₂(R)₆‐[Au₃Co₂(L ‐cys)₆]^3? ([ 1 b ]^3?) with retention of the chiral configurations.     

Cobalt(II)‐Terephthalate Frameworks Containing Bis(benz­imidazole) Derivative Co‐ligands: Syntheses,Crystal Structures,Catalytic and Fluorescence Properties

Two metal‐organic coordination polymers of Co^II with the molecular formulae [Co(L₁)(tp)(H₂O)₂]_n ( 1 ) and [Co(L₂)(tp) · H₂O]_n ( 2 ) [L₁ = 1, 4‐bis(benzimidazole‐1‐ylmethyl)‐ benzene; L₂ = 1, 1‐(1, 4‐butanediyl)bis(5, 6‐dimethylbenzimidazole); tp = terephthalate] were synthesized and characterized by single‐crystal X‐ray diffraction studies, infrared spectroscopy (IR), thermogravimetric analysis (TGA), X‐ray powder diffraction (XRPD), and elemental analysis. The structure determination of complex 1 reveals a 2D layer with (4, 4) topology, with Co^II ions at the nodes connected through tp and L₁ co‐ligands. Complex 2 is the first example of a four‐connected SrAl₂ structure type ( sra , 4²6³8 topology) with threefold interpenetration in Co^II coordination frameworks, forming by bridging L₂ and tp co‐ligands. In addition, the fluorescence and catalytic performances of the complexes for the degradation of methyl orange were investigated.     

Cobalt Complexes with Pyrazole Ligands as Catalyst Precursors for the Peroxidative Oxidation of Cyclohexane: X‐ray Absorption Spectroscopy Studies and Biological Applications

[CoCl(μ‐Cl)(Hpz^Ph)₃]₂ ( 1 ) and [CoCl₂(Hpz^Ph)₄] ( 2 ) were obtained by reaction of CoCl₂ with HC(pz^Ph)₃ and Hpz^Ph, respectively (Hpz^Ph=3‐phenylpyrazole). The compounds were isolated as air‐stable solids and fully characterized by IR and far‐IR spectroscopy, MS(ESI+/?), elemental analysis, cyclic voltammetry (CV), controlled potential electrolysis, and single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 and 2 undergo single‐electron irreversible Co^II→Co^III oxidations and Co^II→Co^I reductions at potentials measured by CV, which also allowed, in the case of dinuclear complex 1 , the detection of electronic communication between the Co centers through the chloride bridging ligands. The electrochemical behavior of models of 1 and 2 were also investigated by density functional theory (DFT) methods, which indicated that the vertical oxidation of 1 and 2 (that before structural relaxation) affects mostly the chloride and pyrazolyl ligands, whereas adiabatic oxidation (that after the geometry relaxation) and reduction are mostly metal centered. Compounds 1 and 2 and, for comparative purposes, other related scorpionate and pyrazole cobalt complexes, exhibit catalytic activity for the peroxidative oxidation of cyclohexane to cyclohexanol and cyclohexanone under mild conditions (room temperature, aqueous H₂O₂). In situ X‐ray absorption spectroscopy studies indicated that the species derived from complexes 1 and 2 during the oxidation of cyclohexane (i.e., Ox‐ 1 and Ox‐ 2 , respectively) are analogous and contain a Co^III site. Complex 2 showed low in vitro cytotoxicity toward the HCT116 colorectal carcinoma and MCF7 breast adenocarcinoma cell lines.