Metallkomplexe mit N2O2S2‐Koordinationssphäre. Synthese und Charakterisierung der Cobalt(II)‐, Nickel(II)‐ und Kupfer(II)‐Komplexe eines 15‐ und eines 16‐gliedrigen N,N′‐bis(2‐hydroxyethyl)‐funktionalisierten makrocyclischen Liganden

Metal Complexes with N₂O₂S₂ Donor Set. Synthesis and Characterization of the Cobalt(II), Nickel(II), and Copper(II) Complexes of a 15‐ and a 16‐Membered Bis(2‐hydroxyethyl) Pendant Macrocyclic Ligand The macrocyclic ligands 6, 10‐bis(2‐hydroxyethyl)‐7, 8, 9, 11, 17, 18‐hexahydro‐dibenzo‐[e, n][1, 4, 8, 12]‐dithiadiaza‐cyclopentadecine ( 1 ) (L¹) and 5, 13‐bis(2‐hydroxyethyl)‐7, 8, 9, 10, 16, 17, 18, 19, 20‐nonahydro‐dibenzo‐[g, o][1, 9, 5, 13]‐dithiadiaza‐cyclohexadecine (L⁴) have been prepared. They form the stable complexes [CoL¹(‐H)CoL¹](ClO₄)₃ ( 2 ), [NiL¹](ClO₄)₂·MeOH ( 3 ), Λ‐[CuL¹](ClO₄)₂·MeOH ( 4a ) and rac‐[CuL¹](ClO₄)₂·MeOH ( 4b ), [NiL⁴](ClO₄)₂ ( 5 ), and [CuL⁴](ClO₄)₂ ( 6 ). The compounds 1 to 6 have been characterized by standard methods and single‐crystal X‐ray diffraction. In the complexes 2 to 6 the metal atoms are octahedrally coordinated by the N₂O₂S₂ donor set of the ligands. L¹ and L⁴ are folded herein along the N···M···S‐ and the N···M···N′‐axes, respectively. This results at the metal atom in a all‐cis‐configuration for the complexes of L¹ and a trans‐N₂‐cis‐O₂‐cis‐S₂‐configuration for the complexes of L⁴. The cobalt(II) complex 2 is a dimer, bridged by a rather short hydrogen bridge of 2.402(12)Å length. The copper(II) complexes of L¹ and L⁴ differ with respect to the Jahn‐Teller‐distortion.     

Synthesis and Crystal Structure of Two Succinato‐Bridged Macrocyclic Nickel(II) Complexes

Two dinuclear succinato‐bridged nickel(II) complexes [Ni(RR‐L)]₂(μ‐SA)(ClO₄)₂ ( 1 ) and [Ni(SS‐L)]₂(μ‐SA)(ClO₄)₂ ( 2 ) (L = 5, 5, 7, 12, 12, 14‐hexamethyl‐1, 4, 8, 11‐tetraazacyclotetradecane, SA = succinic acid) were synthesized and characterized by EA, Circular dichroism (CD), as well as IR and UV/Vis spectroscopy. Single crystal X‐ray diffraction analyses revealed that the Ni^II atoms display a distorted octahedral coordination arrangement, and the succinato ligand bridges two central Ni^II atoms in a bis bidentate fashion to form dimers in 1 and 2 . The monomers of {[Ni(RR‐L)]₂(μ‐SA)}²⁺ and {[Ni(SS‐L)]₂(μ‐SA)}²⁺ are connected by O–H ··· O and N–H ··· O hydrogen bonds into a 1D right‐handed and left‐handed helical chain along the b axis, respectively. The homochiral natures of 1 and 2 are confirmed by the results of CD spectroscopy.     

Synthesis,Structures, and Magnetic Properties of Chiral One‐dimensional CrIII‐MnIII Heterobimetallic Complexes Based on [(Tp)Cr(CN)3]–

Two Cr^III‐Mn^III heterobimetallic compounds, [Mn((R,R)‐5‐MeOSalcy)Cr(Tp)(CN)₃ · 2CH₃CN]_n ( 1‐RR ) and [Mn((S,S)‐5‐MeOSalcy)Cr(Tp)(CN)₃·2CH₃CN]_n ( 1‐SS ) [Salcy = N,N′‐(1,2‐cyclohexanediylethylene)bis(salicylideneiminato) dianion], were synthesized by using the tricyanometalate building block, [(Tp)Cr(CN)₃]^– [Tp = tris(pyrazolyl) hydroborate] and chiral Mn^III Schiff base precursors. Structural analyses and circular dichroism (CD) spectra revealed that 1‐RR and 1‐SS are a pair of enantiomers containing a neutral cyano‐bridged zigzag chain with (–Cr–C≡N–Mn–N≡C–)_n as the repeating unit. Magnetic studies show that antiferromagnetic couplings between Cr^III and Mn^III ions occur by cyanide bridges. 1‐RR and 1‐SS present metamagnetic, spin‐canting, and antiferromagnetic order behaviors at low temperatures.     

Bis(μ‐cyst­amine‐κ4N,S:S′,N′)­bis­[(2‐amino­ethane­thiol­ato‐κ2N,S)­iridium(III)] tetrabromide dihydrate

In the complex cation of the title compound, [Ir₂(C₂H₆NS)₂(C₄H₁₂N₂S₂)₂]Br₄·2H₂O, which was obtained by rearrangement of [Re{Ir(aet)₃}₂]³⁺ (aet is 2‐amino­ethane­thiol­ate) in an aqueous solution, two approximately octahedral fac(S)‐[Ir(NH₂CH₂CH₂S)₃] units are linked by two coordinated di­sulfide bonds. The complex cation has a twofold axis, and the two non‐bridging thiol­ate S atoms in the complex are located on opposite sides of the two di­sulfide bonds. Considering the absolute configurations of the two octahedral units (Δ and Λ) and the four asymmetric di­sulfide S atoms (R and S), the complex consists of the Δ_RRΔ_RR and Λ_SSΛ_SS isomers, which combine to form the racemic compound.     

Chiral Recognition of Racemic Proline based on Chiral Macrocyclic Nickel(II) Complex: Synthesis and Crystal Structures

The reactions of dl‐proline with chiral macrocyclic Ni^II complex [Ni(SS‐L)](ClO₄)₂ in acetonitrile/water gave a six‐coordinate enantiomer formulated as [Ni(SS‐L)(l‐Pro)](ClO₄)₂ · H₂O ( 1 ). Another enantiomer of [Ni(RR‐L)(d‐Pro)](ClO₄)₂ · H₂O ( 2 ) was obtained when [Ni(RR‐L)](ClO₄)₂ was used (L = 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane, Pro = proline). Single‐crystal X‐ray diffraction analyses of complexes 1 and 2 revealed that the Ni^II atom has a distorted octahedral coordination arrangement, being coordinated by four nitrogen atoms of L in a folded configuration, plus two carboxylate oxygen atoms of proline in mutually cis positions. Complexes 1 and 2 are supramolecular stereoisomers, which are constructed with hydrogen bonding linking of [Ni(SS‐L)(l‐Pro)]²⁺ and [Ni(RR‐L)(d‐Pro)]²⁺ monomers to form one‐dimensional zigzag chains. The homochiral natures of complexes 1 and 2 were confirmed by solid CD spectroscopy.     

A one‐dimensional platinum mixed‐valence complex with bridging thiocyanate S atoms: [[PtII(en)2](μ‐SCN)[PtIV(en)2](μ‐SCN)](ClO4)4 (en is ethane‐1,2‐diamine)

A new one‐dimensional platinum mixed‐valence complex with nonhalogen bridging ligands, namely catena‐poly[[[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(II)]‐μ‐thiocyanato‐κ²S:S‐[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(IV)]‐μ‐thiocyanato‐κ²S:S] tetrakis(perchlorate)], {[Pt₂(SCN)₂(C₂H₈N₂)₄](ClO₄)₄}_n, has been isolated. The Pt^II and Pt^IV atoms are located on centres of inversion and are stacked alternately, linked by the S atoms of the thiocyanate ligands, forming an infinite one‐dimensional chain. The Pt^IV—S and Pt^II...S distances are 2.3933 (10) and 3.4705 (10) Å, respectively, and the Pt^IV—S...Pt^II angle is 171.97 (4)°. The introduction of nonhalogen atoms as bridging ligands in this complex extends the chemical modifications possible for controlling the amplitude of the charge‐density wave (CDW) state in one‐dimensional mixed‐valence complexes. The structure of a discrete Pt^IV thiocyanate compound, bis(ethane‐1,2‐diamine‐κ²N,N′)bis(thiocyanato‐κS)platinum(IV) bis(perchlorate) 1.5‐hydrate, [Pt(SCN)₂(C₄H₈N₂)₂](ClO₄)₂·1.5H₂O, has monoclinic (C2) symmetry. Two S‐bound thiocyanate ligands are located in trans positions, with an S—Pt—S angle of 177.56 (3)°.     

Iron(II) and Nickel(II) Complexes of N‐Alkylimidazoles and 1‐Methyl‐1H‐1, 2, 4‐Triazole: X‐ray Studies,Magnetic Characterization,and DFT Calculations

Using the ligands N‐methylimidazole ( MeIm ), N‐ethylimidazole ( EtIm ), N‐propylimidazole ( PrIm ), and 1‐methyl‐1H‐1, 2, 4‐triazole ( MeTz ) three series with a total of 13 iron(II) complexes were isolated. The series comprise of the following complexes: (a) [Fe( MeIm )₆](ClO₄)₂ ( 1 ), [Fe( EtIm )₆](ClO₄)₂ ( 2 ), [Fe( PrIm )₆](ClO₄)₂( 3 ), [Fe( MeTz )₆](ClO₄)₂ ( 4 ), [Fe( MeIm )₆](MeSO₃)₂ ( 5 ), [Fe( EtIm )₆](MeSO₃)₂ ( 6 ), and [Fe( MeTz )₆](BF₄)₂ ( 10 ); (b) [Fe( MeIm )₄(MeSO₃)₂]( 7 ), [Fe( EtIm )₄(MeSO₃)₂] ( 8 ), and [Fe( PrIm )₄(MeSO₃)₂] ( 9 ); (c) [Fe( MeIm )₄(NCS)₂] ( 15 ), [Fe( EtIm )₄(NCS)₂] ( 16 ), and [Fe( MeTz )₄(NCS)₂] ( 17 ). Single crystal X‐ray diffraction studies were performed on 7 – 10 and 15 – 17 . Temperature dependent magnetic susceptibility measurements were performed on selective examples of all series, and confirmed them to be in the HS state over the range 6–300 K. DFT calculations were performed at BP86/def‐SV(P) and TPSSh/def2‐TZVPP level on all [Fe L ₆]²⁺ complex cations and the neutral complexes 7 – 9 and 15 – 17 . Additionally the four homoleptic nickel(II) complexes [Ni L ₆](ClO₄)₂ ( 11 : L = MeIm ; 12 : L = EtIm ; 13 : L = PrIm ; 14 : L = MeTz ) were synthesized and compounds 11 – 13 structurally characterized. UV/Vis/NIR spectroscopic measurements were carried out on all homoleptic iron(II) and nickel(II) complexes. The 10Dq values were determined to be in the range of 11547–11574 and 10471–10834 cm^–1 for the iron(II) and nickel(II) complexes, respectively.     

Copper(II), Cobalt(II), and Nickel(II) Complexes of two Novel Pyridine‐derived Macrocyclic Ligands bearing o‐ and pNitrobenzyl Pendant Groups

The pendant‐armed ligands L¹ and L² were synthesized by N‐alkylation of the four secondary amine groups of the macrocyclic precursor L using o‐nitrobenzylbromide (L¹) and p‐nitrobenzylbromide (L²). Nitrates and perchlorates of Cu^II, Ni^II and Co^II were used to synthesize the metal complexes of both ligands and the complexes were characterized by microanalysis, MS‐FAB, conductivity measurements, IR and UV‐Vis spectroscopy and magnetic studies. The crystal structures of L¹, [CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN, [CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH and [NiL²](ClO₄)₂·3CH₃CN·H₂O were determined by single crystal X‐ray crystallography. These structural analysis reveal the free ligand L¹, three mononuclear endomacrocyclic complexes {[CuL¹](ClO₄)₂·CH₃CN·H₂O, [CuL²](ClO₄)₂·6CH₃CN and [NiL²](ClO₄)₂·3CH₃CN·H₂O} and one binuclear complex {[CuL²][Cu(NO₃)₄]·5CH₃CN·0.5CH₃OH} in which one of the metals is in the macrocyclic framework and the other metal is outside the ligand cavity and coordinated to four nitrate ions.     

Syntheses and structures of one CuI‐containing coordination polymer and two macrocyclic supramolecular complexes based on flexible 1,3,4‐oxadiazole‐containing ligands

Three coordination complexes with Cu^I centres have been prepared using the symmetrical flexible organic ligands 1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane (L1) and 1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane (L2). Crystallization of L1 with Cu(SO₃CF₃)₂ and of L2 with Cu(BF₄)₂ and Cu(ClO₄)₂ in a CH₂Cl₂/CH₃OH mixed‐solvent system at room temperature afforded the coordination complexes catena‐poly[[copper(I)‐μ‐1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane] methanesulfonate dichloromethane 0.6‐solvate], {[Cu(C₂₅H₁₈N₆O₂S₂)](CF₃SO₃)·0.6CH₂Cl₂}_n, (I), bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(tetrafluoridoborate)–dichloromethane–methanol (1/1.5/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](BF₄)₂·1.5CH₂Cl₂·CH₃OH, (II), and bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(perchlorate)–dichloromethane–methanol (1/2/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](ClO₄)₂·2CH₂Cl₂·CH₃OH, (III). Under the control of the dumbbell‐shaped CF₃SO₃⁻ anion, complex (I) forms a one‐dimensional chain and neighbouring chains form a spiral double chain. Under the control of the regular tetrahedron‐shaped BF₄⁻ and ClO₄⁻ anions, complexes (II) and (III) have been obtained as bimetallic rings, which further interact viaπ–π interactions to form two‐dimensional networks. The anions play a decisive role in determining the arrangement of these discrete molecular complexes in the solid state.     

Enantiomer-selective radical cyclopolymerization of rac-2,4-pentanediyl dimethacrylate using a ruthenium-mediated chiral atom transfer radical polymerization initiating system

The enantiomer-selective radical polymerization of rac-2,4-pentanediyl dimethacrylate, an equimolar mixture of (2S,4S)-2,4-pentanediyl dimethacrylate (SS- 1 ) and (2R,4R)-2,4-pentanediyl dimethacrylate (RR- 1 ), was carried out with a chiral atom transfer radical polymerization initiating system consisting of methyl 2-bromoisobutyrate ( 3 ), dichlorotris(triphenylphosphine)ruthenium [RuCl₂(PPh₃)₃], and a chiral additive in anisole at 60 °C. When (S)-1,1′-bi-2-naphthol ( a-3 ) was used as the chiral additive, the recovered monomer was enriched in SS- 1 , and the enantiomeric excess was 16.9% at a 22.6% monomer conversion. The specific rotation ([α]₄₃₅, c 0.3, CHCl₃) of the resulting polymer was +40.3° at a 22.6% monomer conversion. For the copolymerization of SS- 1 and RR- 1 with 3 /RuCl₂(PPh₃)₃/ a-3 in anisole at 60 °C, the monomer reactivity ratio for RR- 1 (r_R) was determined to be 4.94, and that for SS- 1 (r_S) was 0.27. For the homopolymerizations of SS- 1 and RR- 1 with 3 /RuCl₂(PPh₃)₃/ a-3 in anisole at 60 °C, the polymerization rate of RR- 1 was considerably faster than that of SS- 1 , and the rate constants for the homopolymerizations were determined to be k_SS = 2.0 × 10⁻³ h⁻¹ and k_RR = 8.2 × 10⁻³ h⁻¹, respectively. With the values of k_SS, k_RR, r_R, and r_S, the relative ratio k_SS/k_RR/k_SR/k_RS was determined to be 1.2:4.9:4.5:1, which indicated that both the growing end of SS- 1 and that of RR- 1 preferentially reacted with RR- 1 . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4563–4569, 2004     

2‐Amino‐5‐(2‐pyridyl)‐thiadiazole as Bidentate Ligand

The amino substituted bidentate chelating ligand 2‐amino‐5‐(2‐pyridyl)‐1,3,4‐thiadiazole (H₂ L ) was used to prepare 3:1‐type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [Fe^II(H₂ L )₃](ClO₄)₂·0.6MeOH·0.9H₂O a 1:1 mixture of mer and fac isomers is present whereas [Fe^II(H₂ L )₃](BF₄)₂·MeOH·H₂O, [Co^II(H₂ L )₃](ClO₄)₂·2H₂O and [Ni^II(H₂ L )₃](ClO₄)₂·MeOH·H₂O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [Fe^II(H₂ L )₃]²⁺ complex core to exist in the low‐spin state, whereas the [Co^II(H₂ L )₃]²⁺ complex core resides in its high‐spin state, even at very low temperatures.     

Linear Pyrazole‐bridged Tetra(N‐heterocyclic carbene) Ligands and Their Hexanuclear Silver(I) Complexes

New hybrid ligands are reported that combine two types of popular donor groups within a single linear scaffold, viz., a central pyrazolate bridge and two appended bis(N‐heterocyclic carbene) units; the ligand strands thus provide two potentially tridentate {NCC} compartments. The pyrazole/tetraimidazolium proligands, [H₅L¹](PF₆)₄ and [H₅L²](PF₆)₄ , were synthesized via multi‐step protocols, and the NH prototropy of [H₅L¹](PF₆)₄ was examined by variable temperature (VT) NMR spectroscopy, giving solvent dependent activation parameters (ΔH^? = 27.6 kJ · mol^–1, ΔS^? = –125 J · mol^–1 · K^–1 in [D₃]MeCN; ΔH^? = 40.4 kJ · mol^–1, ΔS^? = –86.9 J · mol^–1 · K^–1 in [D₆]DMSO) that are in the range typical for pyrazoles. Reaction of the proligands with Ag₂O gave hexametallic complexes [Ag₆(L¹)₂](PF₆)₄ and [Ag₆(L²)₂](PF₆)₄ that involve all six potential donor atoms of the ligands, viz. the four C^NHC and two N^pz donors, in metal coordination. X‐ray crystallography revealed a chair‐like central {Ag₆} deck in both complexes but different arrangements of the ligand strands, which goes along with significantly different Ag^I ··· Ag^I distances that indicate more pronounced argentophilic interactions in case of [Ag₆(L¹)₂]^{4 +}.     

Synthesis and Structural Characterization of Six Pentanuclear and Tetranuclear Mo/W‐Cu‐S Clusters with Bis(diphenylphosphanyl) Methane

Six heterothiometalic clusters, namely, [WS₄Cu₄(dppm)₄](ClO₄)₂ · 2DMF · MeCN ( 1 ), [MoS₄Cu₄(dppm)₄](NO₃)₂ · MeCN ( 2 ) [MoS₄Cu₃(dppm)₃](ClO₄) · 4H₂O ( 3 ), [WS₄Cu₃(dppm)₃](NO₃) · 4H₂O ( 4 ), [WS₄Cu₃(dppm)₃]SCN · CH₂Cl₂ ( 5 ), and [WS₄Cu₃(dppm)₃]I · CH₂Cl₂ ( 6 ) [dppm = bis (diphenylphosphanyl)methane] were synthesized. Compounds 1 – 4 were obtained by the reactions of (NH₄)₂MS₄ (M = Mo, W) with [Cu₂(μ₂‐dppm)₂(MeCN)₂(ClO₄)₂] {or [Cu(dppm)(NO₃)]₂} in the presence of 1,10‐phen in mixed solvent (CH₃CN/CH₂Cl₂/DMF for 1 and 2 , CH₂Cl₂/CH₃OH/DMF for 3 and 4 . Compounds 5 and 6 were obtained by one‐pot reactions of (NH₄)₂WS₄ with dppm and CuSCN (or CuI) in CH₂Cl₂/CH₃OH. These clusters were characterized by single‐crystal X‐ray diffraction as well as IR, ¹H NMR, and ³¹P NMR spectroscopy. Structure analysis showed that compounds 1 and 2 are “saddle‐shaped” pentanuclear cationic clusters, whereas compounds 3 – 6 are “flywheel‐shaped” tetranuclear cationic clusters. In 1 and 2 , the MS₄^2– unit (M = W, Mo) is coordinated by four copper atoms, which are further bridged by four dppm molecules. In compounds 3 – 6 , the MS₄^2– unit is coordinated by three copper atoms and each copper atom is bridged by three dppm ligands.     

Desulfuration and Cyclization of (Z)‐2‐[Amino(pyridine‐2‐yl)methylene]‐ hydrazonecarbothioamide in the Presence of Manganese(II)

The reaction of (Z)‐2‐[amino(pyridine‐2‐yl)methylene]hydrazonecarbothioamide (HAm4DH) with Mn(ClO₄)₂·6H₂O afforded different mononuclear or polynuclear manganese(II) complexes, the nature of which apparently depended on the solvent used. For example, in ethanol a compound of formula [Mn(HAm4DH)₂](ClO₄)₂ ( 1 ) was obtained, where HAm4DH coordinates as a common tridentate NNS donor, but the [Mn(bpy)₂(NCS)₂] complex ( 2 ) (bpy = 2,2'‐bipyridine) has also been obtained – probably due to C–N bond cleavage of the thiosemicarbazone. Nevertheless, in a basic aqueous medium [Mn(bpy)₃](ClO₄)₂·0.5bpy ( 3 ) is formed and there is structural evidence for chemical transformations of the thiosemicarbazone promoted by Mn^II. Thus, the sulfate in {[Mn(py)₄Mn(py)₂(H₂O)₂(μ‐SO₄)₂]·4H₂O}_n ( 4 ) or sulfate and cyclooctasulfur in [Mn(pta)₂(pdo)]₄(SO₄)₂·4H₂O·S₈] ( 5 ), where pta is 3‐(pyridin‐2‐yl)‐1,2,4‐triazol‐5‐amine and pdo is (2R,4R/2S,4S)‐pentane‐2,4‐diolato, arise from the desulfuration and oxidation of the thiosemicarbazone ligand. The structures of complexes 2 to 5 were established by single‐crystal X‐ray diffraction. The formation of pta is the result of the oxidative cyclization of HAm4DH. In the polynuclear complex 4 , the sulfate acts as an (O,O') bridge between alternating Mn(py)₂(H₂O)₂ and Mn(py)₄ centers. In the tetranuclear complex 5 , pta acts as a bischelating ligand through the N‐pyridine and N‐triazole, and pdo act as a bridge between two manganese atoms. It is also noteworthy that in complexes 4 and 5 hydrogen bonds give rise to different self‐assembly behaviour that leads to complicated supramolecular structures.     

Multifunctionality in Bimetallic LnIII[WV(CN)8]3− (Ln=Gd,Nd) Coordination Helices: Optical Activity,Luminescence, and Magnetic Coupling

Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), (SS/RR)‐iPr‐Pybox (2,6‐bis[4‐isopropyl‐2‐oxazolin‐2‐yl]pyridine) and (SRSR/RSRS)‐Ind‐Pybox (2,6‐bis[8H‐indeno[1,2‐d]oxazolin‐2‐yl]pyridine), have been combined with lanthanide ions (Gd³⁺, Nd³⁺) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN^?‐bridged coordination chains: {[Ln^III(SS/RR‐iPr‐Pybox)(dmf)₄]₃[W^V(CN)₈]₃}_n ? dmf ? 4 H₂O (Ln=Gd, 1 ‐SS and 1 ‐RR; Ln=Nd, 2 ‐SS and 2 ‐RR) and {[Ln^III(SRSR/RSRS‐Ind‐Pybox)(dmf)₄][W^V(CN)₈]}_n ? 5 MeCN ? 4 MeOH (Ln=Gd, 3 ‐SRSR and 3 ‐RSRS; Ln=Nd, 4 ‐SRSR and 4 ‐RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200–450 nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the Gd^III‐W^V chains show dominant ligand‐based red phosphorescence, with λ_max≈660 nm for 1 ‐(SS/RR) and 680 nm for 3 ‐(SRSR/RSRS). The Nd^III‐W^V chains, 2 ‐(SS/RR) and 4 ‐(SRSR/RSRS), exhibit near‐infrared luminescence with sharp lines at 986, 1066, and 1340 nm derived from intra‐f ⁴F_3/2→⁴I_{9/2,11/2,13/2} transitions of the Nd^III centers. This emission is realized through efficient ligand‐to‐metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [W^V(CN)₈]^3? moieties connected by cyanide bridges, 1 ‐(SS/RR) and 3 ‐(SRSR/RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between Gd^III (S_Gd=7/2) and W^V (S_W=1/2) centers with J _{1 ‐(SS)}=?0.96(1) cm^?1, J _{1 ‐(RR)}=?0.95(1) cm^?1, J _{3 ‐(SRSR)}=?0.91(1) cm^?1, and J _{3 ‐(RSRS)}=?0.94(1) cm^?1. 2 ‐(SS/RR) and 4 ‐(SRSR/RSRS) display ferromagnetic coupling within their Nd^III‐NC‐W^V linkages.     

Synthesis and crystal structures of terephthalato-bridged macrocyclic nickel(II) complexes with <Emphasis Type="Italic">cis</Emphasis> configurations

Three dinuclear terephthalato-bridged nickel(II) complexes [Ni(rac-L)]₂(μ-TPA)(ClO₄)₂ (1), [Ni(RR-L)]₂(μ-TPA)(ClO₄)₂ (2), and [Ni(SS-L)]₂(μ-TPA)(ClO₄)₂ (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, TPA = terephthalic acid) have been synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the terephthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(RR-L)]₂(μ-TPA)}²⁺ and {[Ni(SS-L)]₂(μ-TPA)}²⁺ are connected through intermolecular hydrogen bonds to generate 1D right-handed and left-handed helical chains, respectively. The racemic character of 1 and the homochiral natures of 2 and 3 are confirmed by the results of CD spectroscopy.     

Chiral one‐ and two‐dimensional silver(I)–biotin coordination polymers

Reaction of biotin {C₁₀H₁₆N₂O₃S, HL; systematic name: 5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoic acid} with silver acetate and a few drops of aqueous ammonia leads to the deprotonation of the carboxylic acid group and the formation of a neutral chiral two‐dimensional polymer network, poly[[{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)] trihydrate], {[Ag(C₁₀H₁₅N₂O₃S)]·3H₂O}_n or {[Ag(L)]·3H₂O}_n, (I). Here, the Ag^I cations are pentacoordinate, coordinated by four biotin anions via two S atoms and a ureido O atom, and by two carboxylate O atoms of the same molecule. The reaction of biotin with silver salts of potentially coordinating anions, viz. nitrate and perchlorate, leads to the formation of the chiral one‐dimensional coordination polymers catena‐poly[[bis[nitratosilver(I)]‐bis{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] monohydrate], {[Ag₂(NO₃)₂(C₁₀H₁₆N₂O₃S)₂]·H₂O}_n or {[Ag₂(NO₃)₂(HL)₂]·H₂O}_n, (II), and catena‐poly[bis[perchloratosilver(I)]‐bis{μ₃‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}], [Ag₂(ClO₄)₂(C₁₀H₁₆N₂O₃S)₂]_n or [Ag₂(ClO₄)₂(HL)₂]_n, (III), respectively. In (II), the Ag^I cations are again pentacoordinated by three biotin molecules via two S atoms and a ureido O atom, and by two O atoms of a nitrate anion. In (I), (II) and (III), the Ag^I cations are bridged by an S atom and are coordinated by the ureido O atom and the O atoms of the anions. The reaction of biotin with silver salts of noncoordinating anions, viz. hexafluoridophosphate (PF₆⁻) and hexafluoridoantimonate (SbF₆⁻), gave the chiral double‐stranded helical structures catena‐poly[[silver(I)‐bis{μ₂‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridophosphate], {[Ag(C₁₀H₁₆N₂O₃S)₂](PF₆)}_n or {[Ag(HL)₂](PF₆)}_n, (IV), and catena‐poly[[[{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)]‐μ₂‐{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridoantimonate], {[Ag(C₁₀H₁₆N₂O₃S)₂](SbF₆)}_n or {[Ag(HL)₂](SbF₆)}_n, (V), respectively. In (IV), the Ag^I cations have a tetrahedral coordination environment, coordinated by four biotin molecules via two S atoms, and by two carboxy O atoms of two different molecules. In (V), however, the Ag^I cations have a trigonal coordination environment, coordinated by three biotin molecules via two S atoms and one carboxy O atom. In (IV) and (V), neither the ureido O atom nor the F atoms of the anion are involved in coordination. Hence, the coordination environment of the Ag^I cations varies from AgS₂O trigonal to AgS₂O₂ tetrahedral to AgS₂O₃ square‐pyramidal. The conformation of the valeric acid side chain varies from extended to twisted and this, together with the various anions present, has an influence on the solid‐state structures of the resulting compounds. The various O—H...O and N—H...O hydrogen bonds present result in the formation of chiral two‐ and three‐dimensional networks, which are further stabilized by C—H...X (X = O, F, S) interactions, and by N—H...F interactions for (IV) and (V). Biotin itself has a twisted valeric acid side chain which is involved in an intramolecular C—H...S hydrogen bond. The tetrahydrothiophene ring has an envelope conformation with the S atom as the flap. It is displaced from the mean plane of the four C atoms (plane B) by 0.8789 (6) Å, towards the ureido ring (plane A). Planes A and B are inclined to one another by 58.89 (14)°. In the crystal, molecules are linked via O—H...O and N—H...O hydrogen bonds, enclosing R₂²(8) loops, forming zigzag chains propagating along [001]. These chains are linked via N—H...O hydrogen bonds, and C—H...S and C—H...O interactions forming a three‐dimensional network. The absolute configurations of biotin and complexes (I), (II), (IV) and (V) were confirmed crystallographically by resonant scattering.     

Application of a Structure/Oxidation‐State Correlation to Complexes of Bridging Azo Ligands

Based on data from more than 40 crystal structures of metal complexes with azo‐based bridging ligands (2,2′‐azobispyridine, 2,2′‐azobis(5‐chloropyrimidine), azodicarbonyl derivatives), a correlation between the N? N bond lengths (d_NN) and the oxidation state of the ligand (neutral, neutral/back‐donating, radical‐anionic, dianionic) was derived. This correlation was applied to the analysis of four ruthenium compounds of 2,2′‐azobispyridine (abpy), that is, the new asymmetrical rac‐[(acac)₂Ru1(μ‐abpy)Ru2(bpy)₂](ClO₄)₂ ([ 1 ](ClO₄)₂), [Ru(acac)₂(abpy)] ( 2 ), [Ru(bpy)₂(abpy)](ClO₄)₂ ([ 3 ](ClO₄)₂), and meso‐[(bpy)₂Ru(μ‐abpy)Ru(bpy)₂](ClO₄)₃ ([ 4 ](ClO₄)₃; acac^?=2,4‐pentanedionato, bpy=2,2′‐bipyridine). In agreement with DFT calculations, both mononuclear species 2 and 3 ²⁺ can be described as ruthenium(II) complexes of unreduced abpy⁰, with 1.295(5)<d_NN<1.320(3) Å, thereby exhibiting effects from π back‐donation. However, the abpy ligand in both the asymmetrical diamagnetic compound 1 ²⁺ (d_NN=1.374(6) Å) and the symmetrical compound 4 ³⁺ (d_NN=1.360(7), 1.368(8) Å) must be formulated as abpy^.?. Remarkably, the addition of [Ru^II(bpy)₂]²⁺ to mononuclear [Ru^II(acac)₂(abpy⁰)] induces intracomplex electron‐transfer under participation of the noninnocent abpy bridge to yield rac‐[(acac)₂Ru1^III(μ‐abpy^.?)Ru2^II(bpy)₂]²⁺ ( 1 ²⁺) with strong antiferromagnetic coupling between abpy^.? and Ru^III (DFT (B3LYP/LANL2DZ/6‐31G*)‐calculated triplet–singlet energy separation E_S=1?E_S=0=11739 cm^?1). Stepwise one‐electron transfer was studied for compound 1 ⁿ, n=1?, 0, 1+, 2+, 3+, by UV/Vis/NIR spectroelectrochemistry, EPR spectroscopy, and by DFT calculations. Whereas the first oxidation of compound 1 ²⁺ was found to mainly involve the central ligand to produce an (abpy⁰)‐bridged Class I mixed‐valent Ru1^IIIRu2^II species, the first reduction of compound 1 ²⁺ affected both the bridge and Ru1 atom to form a radical complex ( 1 ⁺), with considerable metal participation in the spin‐distribution. Further reduction moves the spin towards the {Ru2(bpy)₂} entity.     

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.     

Hexakis(prop‐2‐enamide)copper(II) bis(perchlorate) and hexakis(prop‐2‐enamide)manganese(II) bis(perchlorate)

The structures of [Cu(AA)₆](ClO₄)₂, (I), and [Mn(AA)₆](ClO₄)₂, (II) (AA is acrylamide, also known as prop‐2‐enamide; C₃H₅NO), display both intra‐ and intermolecular N—H...O hydrogen bonding. A three‐dimensional network is propagated via the perchlorate counter‐ions. There are two crystallographically independent molecules in the copper complex, with the most significant difference between them being the conformation of one symmetry‐related pair of AA ligands which are in the unusual syn conformation. The copper complex exhibits syn/anti disorder of the =CH₂ group in one pair of symmetry‐related AA ligands. The Cu^II and Mn^II centres are both situated on centres of inversion. The copper complex cation has octahedral coordination geometry with typical Jahn–Teller distortions.