Synthesis,Crystal Structure,and Spectral Properties of Two Manganese(II) and Zinc(II) Complexes with 3,4‐Dimethyl‐5‐(2‐pyridyl)‐1,2,4‐triazole

Two complexes, cis‐[MnL₂(NCS)₂] ( 1 ) and cis‐[ZnL₂(NCS)₂] ( 2 ) with asymmetrical substituted triazole ligands [L = 3,4‐dimethyl‐5‐(2‐pyridyl)‐1,2,4‐triazole], were synthesized and characterized by elemental analysis, UV/Vis and FT‐IR spectroscopy as well as thermogravimetric analyses (TGA), powder XRD, and single‐crystal X‐ray diffraction. In the complexes, each L molecule adopts a chelating bidentate mode by the nitrogen atoms of pyridyl and triazole. Both complexes have a similar distorted octahedral [MN₆] core (M = Mn²⁺ and Zn²⁺) with two NCS^– ions in the cis position.     

Spin crossover in iron(II) complexes of 3,5-di(2-pyridyl)-1,2,4-triazoles and 3,5-di(2-pyridyl)-1,2,4-triazolates

The iron coordination chemistry of 3,5-di(2-pyridyl)-1,2,4-triazoles and 3,5-di(2-pyridyl)-1,2,4-triazolates is reviewed. This includes both mononuclear and dinuclear complexes, and both iron(II) and iron(III) oxidation states. The main focus is on the synthesis, structure and magnetic properties of these complexes.     

Lanthanide(III) (Eu,Gd, Tb,Dy) Complexes Derived from 4‐(Pyridin‐2‐yl)methyleneamino‐1,2,4‐triazole: Crystal Structure,Magnetic Properties,and Photoluminescence

The reaction of lanthanide(III) nitrates with 4‐(pyridin‐2‐yl)methyleneamino‐1,2,4‐triazole (L) was studied. The compounds [Ln(NO₃)₃(H₂O)₃] ? 2 L, in which Ln=Eu ( 1 ), Gd ( 2 ), Tb ( 3 ), or Dy ( 4 ), obtained in a mixture of MeCN/EtOH have the same structure, as shown by XRD. In the crystals of these compounds, the mononuclear complex units [Ln(NO₃)₃(H₂O)₃] are linked to L molecules through intermolecular hydrogen‐bonding interactions to form a 2D polymeric supramolecular architecture. An investigation into the optical characteristics of the Eu³⁺‐, Tb³⁺‐, and Dy³⁺‐containing compounds ( 1 , 3 , and 4 ) showed that these complexes displayed metal‐centered luminescence. According to magnetic measurements, compound 4 exhibits single‐ion magnet behavior, with ΔE_eff/k_B=86 K in a field of 1500 Oe.     

Synthesis,Structures, Magnetic and Luminescent Properties of a Series of Iron(II) and Zinc(II) Coordination Frameworks with Versatile 4‐Substitued 1, 2,4‐Triazole Ligands

Three multi‐dentate 1, 2,4‐triazole derivative ligands containing different 4‐substituted groups, namely N‐1, 2,4‐triazol‐4‐yl(pyridin‐3‐yl)methylenimine (L₁), N‐1, 2,4‐triazol‐ 4‐yl(pyridin‐4‐yl)methylenimine (L₂), and 4‐(2‐pyridine)‐1, 2,4‐triazole (L₃) were used to isolate five iron(II) and zinc(II) coordination frameworks, [Zn(μ₂‐L₁)Cl₂] ( 1 ), [Zn(μ₂‐L₂)Br₂] ( 2 ), [Fe(L₁)₂(NCS)₂(H₂O)₂] ( 3 ), [Fe(L₃)₂(dca)₂(H₂O)₂] ( 4 ), and [Fe(L₃)₂(μ₂‐dca)] ( 5 ) (dca = dicyanamide anion). When different zinc(II) salts were used to react with L₁ and L₂ under solvothermal conditions, two one‐dimensional (1D) zinc(II) coordination frameworks 1 and 2 containing four‐coordinate central zinc(II) atoms were isolated. 1 is a 3D achiral supra‐molecular framework, whereas 2 is a 3D chiral supra‐molecular framework containing helical chains on a 2₁ axis. 3 is a mono‐nuclear iron(II) coordination framework containing six‐coordinate central Fe^II atoms. When L₃ was employed, mono‐nuclear iron(II) framework 4 and 1D iron(II) chain 5 could be isolated when different amounts of Nadca were introduced into the reaction system. Variable‐temperature magnetic susceptibility data of 3 – 5 were recorded in the 2–300 K temperature range indicating weak anti‐ferromagnetic interactions. The solid‐state luminescent properties of coordination polymers 1 and 2 were also investigated at room temperature.     

Synthesis,Characterization and Crystal Structures of 1,2,4‐Triazole based Schiff‐Bases and their Copper(I) Complexes

The reaction of of 4‐amino‐5‐ethyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AETT, L ) with furfural in methanol led to the corresponding Schiff‐Base ( L1 ). The reaction of L1 with [Cu(PPh₃)₂]Cl in methanol gave to the neutral compound [( L1 )Cu(PPh₃)₂Cl] ( 1 ). By recrystallization of 1 from CH₃CN the complex [( L1 )Cu(PPh₃)₂Cl]·CH₃CN ( 1a ) was obtained. All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for L1 at ?80 °C: space group with a = 788.4(1), b = 830.3(2), c = 928.8(2) pm, α = 84.53(1)°, β = 65.93(1)°, γ = 72.02(1)°, Z = 2, R₁ = 0.0323; for 1 at ?100 °C: space group with a = 1166.3(1), b = 1423.8(2), c = 1489.1(2) pm, α = 62.15(1)°, β = 72.04(1)°, γ = 88.82(1)°, Z = 2, R₁ = 0.0338 and for 1a at ?100 °C: space group P2₁/c with a = 1294.1(1), b = 1019.8(2), c = 3316.9(4) pm, β = 94.73(1)°, Z = 4, R₁ = 0.0435.     

Solvothermal Synthesis,Crystal Structures,and Magnetic Properties of Two Organically Templated Iron Sulfates with Chain Structures

Two new one‐dimensional (1D) organically templated iron(III) sulfates [C₂NH₈]₃ [Fe₃(μ₃‐O)₂(SO₄)₄] ( 1 ) and [C₂N₂H₁₀][C₂NH₇]_0.5[FeF(SO₄)₂] ( 2 ) were synthesized under solvothermal conditions and characterized by single‐crystal X‐ray diffraction, powder X‐ray diffraction (XRD), FT‐IR spectroscopy, elemental analyses, ICP analyses, and thermogravimetric analyses. Single‐crystal structure analysis reveals that both compounds show linear‐chain structures, involving FeO₆ (FeF₂O₄) octahedra and SO₄ tetrahedra. The magnetic properties of the two compounds have also been investigated.     

Three Coordination Polymers based on 3,5‐Bis(imidazole‐1‐yl)pyridine and Benzoic Acid: Synthesis,Crystal Structures and Photoluminescent Properties

Three metal coordination polymers {[Co(L)₂(H₂O)₂]²⁺ · 2NO₃^–}_n ( 1 ), {[Mn(L)₂(H₂O)₂]²⁺ · 2Cl^– · 3H₂O}_n ( 2 ), and [ZnL(ba)₂]_n ( 3 ) [L = 3,5‐bis(imidazole‐1‐yl)pyridine and Hba = benzoic acid] were synthesized and structurally characterized by IR spectroscopy, elemental analysis, X‐ray powder diffraction, and X‐ray single crystal diffraction. Complex 1 shows a one‐dimensional (1D) chain structure. Adjacent chains are connected by hydrogen bonding and nitrate groups to form a 3D network. Complex 2 features a 2D layer structure. A three‐dimensional network is constructed through the cluster consisting of two chloride ions and three water molecules. Complex 3 shows a 1D zigzag chain structure that further twists together to form a 3D network. The X‐ray powder diffraction patterns were compared with the simulated ones. Moreover, the luminescent properties of 1 – 3 were investigated in the solid state at room temperature, and the thermogravimetric analyses were carried out to study the thermal stability of the three complexes.     

Synthesis,Characterization and Crystal Structures of new 1,2,4‐Triazole based Schiff‐bases and their Copper(I) Complexes

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, 1 ) with 4‐methoxy benzaldehyde and 3‐methoxybenzaldehyde in methanol led to the iminic derivatives 4‐(4‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)thione ( 2 , L1) and 4‐(3‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione ( 3 , L2). The reaction of the latter with [(PPh₃)₂CuCl] in methanol solution gave the first Cu^I complex of 3 , [(PPh₃)₂CuCl(L2)] ( 4 ) and in chloroform solution the complex [(PPh₃)₂CuCl(L2)]·2CHCl₃ ( 5 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for 2 at ?80 °C: space group P2₁/c with a = 1351.3(3), b = 399.4(1), c = 2225.2(5) pm, β = 96.50(2)°, Z = 4, R₁ = 0.0667, for 3 at ?80 °C: space group R3c with a = b = 3020.4(2), c = 708.2(1) pm, Z = 18, R₁ = 0.0435, for 4 at ?80 °C: space group P2₁/c with a = 1427.8(1), b = 1129.0(1), c = 2622.8(2) pm, β = 97.19(1)°, Z = 4, R₁ = 0.0517 and for 5 at ?80 °C: space group with a = 1280.5(1), b = 1316.1(1), c = 1731.4(1) pm, α = 78.14(1)°, β = 86.06(1)°, γ = 64.69(1)°, Z = 2, R₁ = 0.0525.     

Allylic Peroxidations with Bis(2‐pyridylimino)isoindolato‐Cobalt and ‐Iron Complexes

Several novel substituted bis(2‐pyridylimino)isoindolato (BPI) cobalt(II) and iron(II) complexes [M(BPI)(OAc)(H₂O)] (M = Co: 1 ‐ 6, Fe: 7) have been synthesized by reaction of bis(2‐pyridylimino)isoindole derivatives with the corresponding metal(II) acetates. Reaction of 1‐6 with 1.5 ‐ 2 molar equivalents of t‐BuOOH gave the corresponding alkylperoxocobalt(III) complexes [Co(BPI)(OAc)(OOtBu)] (10 ‐ 15). Using an aqueous solution of t‐BuOOH (70 %), cyclohexene was selectively catalytically oxidized to the dialkylperoxide cyclohex‐2‐ene‐1‐t‐butylperoxide.     

Coordination Frameworks based on 3,5‐Bis(imidazole‐1‐yl)­pyridine and Aromatic Dicarboxylate Ligands: Synthesis,Crystal Structures,and Photoluminescent Properties

Three metal coordination polymers [Zn(bdc)(L)(H₂O)]_n ( 1 ), [Co(pta)(L)(H₂O)₂]_n ( 2 ), and [Cd(tda)(L)(H₂O)]_n ( 3 ) [H₂bdc = 1,2‐benzene dicarboxylate acid, H₂pta = terephthalic acid, H₂tda = 2,5‐thiophenedicarboxylic acid, L = 3,5‐bis(imidazole‐1‐yl)pyridine] were synthesized and structurally characterized by IR spectroscopy, elemental analysis, X‐ray powder diffraction, and X‐ray single crystal diffraction. Complex 1 shows a three‐dimensional (3D) structure with cco topology with the symbol 6⁵ · 8, whereas complex 2 features a 3D structure with cds topology with the symbol 6⁵ · 8. Complex 3 has a 2D network constructed by the cadmium atoms bridged through the ligands tda and L. Their X‐ray powder diffraction patterns were compared with the simulated ones. Moreover, their luminescent properties were investigated in the solid state at room temperature, and the thermogravimetric analyses were carried out to study the thermal stability of the 3D networks.     

Syntheses,Crystal Structures,and Properties of Three Copper(II) Complexes Constructed by 4‐(4,6‐Bis(1H‐pyrazol‐1‐yl)‐1,3,5‐triazin‐2‐yl)morpholine

Three copper(II) complexes of the polydentate N‐donor ligand [4‐(4,6‐bis(1H‐pyrazol‐1‐yl)‐1,3,5‐triazin‐2‐yl)morpholine] (L) with chlorides, nitrates, and perchlorates as anions, namely, [CuCl₂(L)] · 0.5(MeCN) ( 1 ), [Cu(NO₃)₂(H₂O)(L)] · (MeCN) ( 2 ), and [Cu(L)₂](ClO₄)₂ · (MeCN) ( 3 ) were synthesized and structurally characterized by IR, elemental analysis and X‐ray crystallographic analysis. In these complexes, the L ligand binds the copper(II) cation in the tridentate N₃ form. The coordination arrangement around the central copper(II) atom is distorted square‐pyramidal in 1 but it is distorted octahedral in 2 and 3 . The interesting noncovalent interactions such as hydrogen bonds, π–π stacking, and anion–π interactions present in the solid‐state structures are discussed. The crystal results reveal that the counteranions play important roles in determining the diverse structures of these complexes. Moreover, the PXRD, TG, DRS, and fluorescence properties of compounds 1 – 3 were investigated.     

Three zinc(II) and cadmium(II) complexes containing 4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole and polynitrile ligands: synthesis,molecular and supramolecular structures,and photoluminescence properties

Three photoluminescent complexes containing either Zn^II or Cd^II have been synthesized and their structures determined. Bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)zinc(II), [Zn(C₁₂H₁₀N₆)₂(C₂N₃)₂], (I), bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(dicyanamido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₂N₃)₂], (II), and bis[4‐amino‐3,5‐bis(pyridin‐2‐yl)‐1,2,4‐triazole‐κ²N ¹,N ⁵]bis(tricyanomethanido‐κN ¹)cadmium(II), [Cd(C₁₂H₁₀N₆)₂(C₄N₃)₂], (III), all crystallize in the space group P , with the metal centres lying on centres of inversion, but neither analogues (I) and (II) nor Cd^II complexes (II) and (III) are isomorphous. A combination of N—H…N and C—H…N hydrogen bonds and π–π stacking interactions generates three‐dimensional framework structures in (I) and (II), and a sheet structure in (III). The photoluminescence spectra of (I)–(III) indicate that the energies of the π–π* transitions in the coordinated triazole ligand are modified by minor changes of the ligand geometry associated with coordination to the metal centres.     

Synthesis,Structure, and Magnetic Characterization of a Series of Iron(II) Coordination Frameworks with 2, 6‐Bis(1, 2,4‐triazole‐4‐yl)pyridine

Based on the bis‐triazole ligand 2, 6‐bis(1, 2,4‐triazole‐4‐yl)pyridine (L), the triazole‐iron(II) complexes [Fe(L)₂(dca)₂(H₂O)₂] · 2H₂O ( 1 ) (Nadca = sodium dicyanamide), {[Fe(μ₂‐L)₂(H₂O)₂]Cl₂}_n ( 2 ), and {[Fe(μ₂‐L)₂(H₂O)₂](ClO₄)₂ · L · H₂O}_n ( 3 ) were isolated by solvent diffusion methods. When iron(II) salts and Nadca were used, compound 1 was isolated, which contains mononuclear Fe(L)₂(dca)₂(H₂O)₂ units. When FeCl₂ or FeClO₄ were used, one‐dimensional (1D) cation iron(II) chains ( 2 ) and two‐dimensional (2D) cation iron(II) networks ( 3 ) were isolated indicating anion directing structural diversity. Moreover, variable‐temperature magnetic susceptibility data of 1 – 3 were recorded in the temperature range 2–300 K. The magnetic curve of complex 2 was fitted by using the classical spin Heisenberg chain model indicating anti‐ferromagnetic interactions (J = –5.31 cm^–1). Obviously complexes 1 – 3 show no detectable thermal spin crossover behaviors, the lack of spin‐crossover behavior may be correlated with FeN₄O₂ coordination spheres in 1 – 3 .     

Synthesis,Structure, and Supramolecular Chemistry of Three Azide Manganese Complexes with 2, 6‐Bis(benzimidazol‐2‐yl)pyridine

Three azide complexes with the tridentate ligand 2, 6‐bis(benzimidazol‐2‐yl)pyridine (H₂BBIP) were synthesized and their complicated supramolecular interactions were investigated with single‐crystal X‐ray diffraction. Interestingly, the complexes are assembled by bifurcated hydrogen bonding, double helical π–π stacking, or anion–π stacking interactions of the benzimidazole rings by tuning the reaction conditions (temperature, ratio, solvent). Complex 1 is a mononuclear compound, namely, Mn(H₂BBIP)N₃(CH₃O) · CH₃OH. In its 3D supramolecular network, the nitrogen atom of the azide anion is acting as hydrogen bonding bifurcated acceptor. Complex 2 is a dinuclear compound, namely, Mn₂(H₂BBIP)₂(N₃)₂ · (H₂O)_0.5. The dinuclear unit is connected by intramolecular π–π stacking interactions. Furthermore, double helical π–π stacking interactions in the benzimidazole rings are observed. Complex 3 , Mn₂(H₂BBIP)₂(N₃)₂ · CH₃OH, can be formulated as a pseudopolymorph of complex 2 , which exhibits intramolecular π–π stacking interactions as well as anion–π interactions in the dinuclear unit.     

Synthesis and Crystal Structures of Bis(1‐{(E)‐2‐pyridinylmethylidene}‐semicarbazone)iron(II) and ‐copper(II) Diperchlorate Monohydrates

The pyridine‐2‐carbaldehyde semicarbazone ligand (HL) reacts with iron(II) and copper(II) perchlorates in boiling ethanol to yield red‐violet [Fe^II(HL)₂](ClO₄)₂·H₂O ( 1 ) and light‐green crystals [Cu^II(HL)₂](ClO₄)₂·H₂O ( 2 ). The crystals are triclinic with the metal ions in an octahedral environment, coordinated to two nitrogen and one oxygen‐donor atom from HL. Electronic, magnetic and electrochemical properties are presented as well.     

Syntheses,Crystal Structures,and Luminescence Properties of Four Coordination Polymers Based on 1,3,5‐Tris (imidazol‐1‐yl)benzene

Based on the tripodal 1,3,5‐tris(imidazol‐1‐yl)benzene (tib) ligand, four transition metal coordination polymers, namely, {[Ni₃(tib)₂(H₂O)₁₂] · (SO₄)₃}_n ( 1 ), {[Co_1/6(tib)_1/3] · (O)_1/3}_n ( 2 ), and [M(tib)(hip)]_n (M = Mn for 3 , and M = Co for 4 ) (hip = 5‐hydroxyisophthalic acid), were synthesized through solvothermal method. Their structures were defined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses (EA), IR spectra, powder X‐ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 displays a 2D 3‐connected (6³) hcb net. Complex 2 is a 2D (3,6)‐connected (4³)₂(4⁶.6⁶.8³) kgm net. Complex 3 and 4 present similar 2D 4‐connected (4⁴.6²) sql net. Moreover, the solid state luminescence properties of complexes 1 and 3 were investigated.     

Synthesis and Characterization of Bis(2‐iminopyrrolyl) Iron(II) Complexes by N–H Bond Activation

The reactions of 2‐iminopyrroles 1 – 3 with Fe(PMe₃)₄ afforded the N–H activated bis(2‐iminopyrrolyl) iron(II) complexes 4 – 6 . The structures of compounds 4 – 6 were determined by single‐crystal X‐ray diffraction. The formation mechanism of complexes 4 – 6 was discussed.