Synthesis,Crystal Structures,and Properties of Copper(II), Zinc(II), and Cadmium(II) Coordination Polymers Based on 5‐Nitro‐isophthalate and 1,2‐(2‐Pyridyl)‐1,2,4‐triazole

Three coordination polymers, namely {[Cu(5‐nipa)(L²²)](H₂O)₂}_n ( 1 ), [Zn(5‐nipa)(L²²)(H₂O)]_n ( 2 ), and {[Cd₂(5‐nipa)₂(L²²)(H₂O)₃](H₂O)_3.6}_n ( 3 ), were prepared under similar synthetic method based on 1,2‐(2‐pyridyl)‐1,2,4‐triazole (L²²) and ancillary ligand 5‐nitro‐isophthalic acid (5‐H₂nipa) with Cu^II, Zn^II, and Cd^II perchlorate, respectively. All the complexes were characterized by IR spectroscopy, elemental analysis, and powder X‐ray diffraction (PXRD) patterns. Single‐crystal X‐ray diffraction indicates that complexes 1 and 2 show similar 1D chain structures, whereas complex 3 exhibits the 2D coordination network with hcb topology. The central metal atoms show distinct coordination arrangements ranging from distorted square‐pyramid for Cu^II in 1 , octahedron for Zn^II in 2 , to pentagonal‐bipyramid for Cd^II in 3 . The L²² ligand adopts the same (η³,μ₂) coordination fashion in complexes 1 – 3 , while the carboxyl groups of co‐ligand 5‐nipa^2– adopt monodentate fashion in 1 and 2 and bidentate chelating mode in 3 . These results indicate that the choice of metal ions exerts a significant influence on governing the target complexes. Furthermore, thermal stabilities of complexes 1 – 3 and photoluminescent properties of 2 and 3 were also studied in the solid state.     

Synthesis,Crystal Structure and Photoluminescence Property of Zinc(II), Cadmium(II), and Lead(II) Complexes with Bidentate Ligand: 1‐(1‐Imidazolyl)‐4‐(imidazol‐1‐ylmethyl)benzene (IIMB)

Assembly of bidentate ligand 1‐(1‐imidazolyl)‐4‐(imidazol‐1‐ylmethyl)benzene (IIMB) with varied metal salts of Zn^II, Cd^II and Pb^II provide three new complexes, [Zn(IIMB)₂](ClO₄)₂·2H₂O ( 1 ), [Cd(IIMB)₂(SCN)₂] ( 2 ) and [Pb(IIMB)₂(SCN)](SCN) ( 3 ). Single crystal X‐ray diffraction studies revealed that complexes 1 and 2 display a similar one‐dimensional double stranded chain structure, while complex 3 is a slight distorted rhombohedral grid network with (4,4) topology. The results indicate that the coordination geometry of the metal ion and the counter anion have great impact on the structure of the complexes. In addition, the photoluminescence properties of ligand IIMB and complexes 1 – 3 were studied in the solid state at room temperature.     

Three Polymorphic CdII Coordination Polymers Obtained from the Solution and Mechanochemical Reactions of 3‐Cyanopentane‐2,4‐dione with CdII Acetate

We previously reported that monomeric and polymeric metal complexes are obtained from solution and mechanochemical reactions of 3‐cyano‐pentane‐2,4‐dione (CNacacH) with 3d metal acetates (M=Mn^II, Fe^II, Co^II, Ni^II, Cu^II, and Zn^II). A common feature found in all complexes was that their structural base is trans‐[M(CNacac)₂]. Here, we report that the reactions of CNacacH with Cd^II acetate in the solution and solid states afford different coordination polymers composed of trans‐[Cd(CNacac)₂] and cis‐[Cd(CNacac)₂] units, respectively. From a methanol solution containing CNacacH (L) and Cd(OAc)₂ ? 2 H₂O (M), a coordination polymer ( Cd‐1 ) in which trans‐[Cd(CNacac)₂] units are three‐dimensionally linked was obtained. In contrast, two different coordination polymers, Cd‐2 and Cd‐3 , were obtained from mechanochemical reactions of CNacacH with Cd(OAc)₂ ? 2 H₂O at M/L ratios of 1:1 and 1:2, respectively. In Cd‐2 , cis‐[Cd(CNacac)₂] units are two‐dimensionally linked, whereas the units are linked three‐dimensionally in Cd‐3 . Furthermore, Cd‐1 and Cd‐2 converted to Cd‐3 by applying an annealing treatment and grinding with a small amount of liquid, respectively, in spite of the polymeric structures. These phenomena, 1) different structures are formed from solution and mechanochemical reactions, 2) two polymorphs are formed depending on the M/L ratio, and 3) structural transformation of resulting polymeric structures, indicate the usability of mechanochemical method in the syntheses of coordination polymers as well as the peculiar structural flexibility of cadmium‐CNacac polymers.     

Syntheses,Structures, and Properties of Copper(II), Cobalt(II), and Cadmium(II) Complexes with Flexible Multicarboxylate Ligand

Three new coordination polymers, namely, [CuL_0.5] ( 1 ), [Co(H₂L)(H₂O)₂][H₂O] ( 2 ), and [(CdCl)_0.5Cd_0.25(H₂L)_0.5] ( 3 ) were synthesized under hydrothermal conditions from the corresponding Cu^II, Co^II, and Cd^II salts with a multidentate ligand of 2,2′,2′′,2′′′‐[2,3,5,6‐tetramethyl‐1,4‐phenylenebis(methylenenitrilo)]tetraacetic acid (H₄L). The complexes were characterized by single‐crystal X‐ray diffraction, IR, thermogravimetric, and elemental analyses. Complex 1 crystallizes in the orthorhombic space group Pbca and has a three‐dimensional architecture with infinite two‐dimensional networks linked together by weak Cu–O interactions. Complex 2 crystallizes in the monoclinic space group P2(1) and displays a 2D network. Complex 3 crystallizes in the tetragonal space group P4(2)/ncm and exhibits an infinite 3D architecture that has unusual [Cd₂(CO₂)₄Cl₂] dinuclear paddle‐wheel units and [Cd(CO₂)₄] dodecahedron units. The results showed that the coordination arrangement of central metal atoms and the conformation and coordination mode of organic ligands play an important role in determining the structure of the complexes. The luminescence property of complex 3 was studied in the solid state at room temperature.     

Synthesis,Spectral, Thermal Studies of Co(II), Ni(II), Cu(II) and Zn(II)‐arginato Complexes. Crystal Structure of Monoaquabis(arginato‐κO,κN)copper(II). [Cu(arg)2(H2O)].NaNO3

Transition metal complexes of arginine (using Co(II), Ni(II), Cu(II) and Zn(II) cations separately) were synthesized and characterized by FTIR, TG/DTA‐DrTG, UV‐Vis spectroscopy and elemental analysis methods. Cu(II)‐Arg complex crystals was found suitable for x‐ray diffraction studies. It was contained, one mole Cu^II and Na⁺ ions, two arginate ligands, one coordinated aqua ligand and one solvent NO₃^? group in the asymmetric unit. The principle coordination sites of metal atom have been occupied by two N atoms of arginate ligands, two carboxylate O atoms, while the apical site was occupied by one O atom for Cu^II cation and two O atoms for Co^II, Ni^II, Zn^II atoms of aqua ligands. Although Cu^II ion adopts a square pyramidal geometry of the structure. Co^II, Ni^II, Zn^II cations have octahedral due to coordination number of these metals. Neighbouring chains were linked together to form a three‐dimensional network via hydrogen‐bonding between coordinated water molecule, amino atoms and O atoms of the bridging carboxylate groups. Cu^II complex was crystallized in the monoclinic space group P2₁, a = 8.4407(5) Å, b = 12.0976(5) Å, c = 10.2448(6) Å, V = 1041.03(10) ų, Z = 2. Structures of the other metal complexes were similar to CuII complex, because of their spectroscopic studies have in agreement with each other. Copper complex has shown DNA like helix chain structure. Lastly, anti‐bacterial, anti‐microbial and anti‐fungal biological activities of complexes were investigated.     

Synthesis,crystal structures and luminescence properties of seven mononuclear zinc(II), cadmium(II), cobalt(II) and nickel(II) complexes with 5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole

Due to their versatile coordination modes and metal‐binding conformations, triazolyl ligands can provide a wide range of possibilities for the construction of supramolecular structures. Seven mononuclear transition metal complexes with different structural forms, namely aquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]zinc(II), [Zn(C₁₄H₁₁N₄)₂(H₂O)], (I), bis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]bis(nitrato‐κO )zinc(II), [Zn(NO₃)₂(C₁₄H₁₂N₄)₂], (II), bis(methanol‐κO )bis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]zinc(II), [Zn(C₁₄H₁₁N₄)₂(CH₄O)₂], (III), diiodidobis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]cadmium(II), [CdI₂(C₁₄H₁₂N₄)₂], (IV), bis[5‐(4‐methylphenyl)‐3‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole‐κ²N ³,N ⁴]bis(nitrato‐κO )cadmium(II), [Cd(NO₃)₂(C₁₄H₁₂N₄)₂], (V), aquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]cobalt(II), [Co(C₁₄H₁₁N₄)₂(H₂O)], (VI), and diaquabis[3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazolato‐κ²N ¹,N ⁵]nickel(II), [Ni(C₁₄H₁₁N₄)₂(H₂O)₂], (VII), have been prepared by the reaction of transition metal salts (Zn^II, Cd^II, Co^II and Ni^II) with 3‐(4‐methylphenyl)‐5‐(pyridin‐2‐yl)‐1H‐1,2,4‐triazole (pymphtzH) under either ambient or hydrothermal conditions. These compounds have been characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. All the complexes form three‐dimensional supramolecular structures through hydrogen bonds or through π–π stacking interactions between the centroids of the pyridyl or arene rings. The pymphtzH and pymphtz⁻ entities act as bidentate coordinating ligands in each structure. Moreover, all the pyridyl N atoms are coordinated to metal atoms (Zn, Cd, Co or Ni). The N atom in the 4‐position of the triazole group is coordinated to the Zn and Cd atoms in the crystal structures of (II), (IV) and (V), while the N atom in the 1‐position of the triazolate group is coordinated to the Zn, Co and Ni atoms in (I), (III), (VI) and (VII).     

Synthesis,Structures and Spectroscopic Properties of Platinum(II), Palladium(II) and Copper(I) Halide Complexes with Pyrimidine‐phosphine Ligand

The reactions of pyrimidine‐phosphine ligand N‐[(diphenylphosphino)methyl]‐2‐pyrimidinamine ( L ) with various metal salts of Pt^II, Pd^II and Cu^I provide three new halide metal complexes, Pt₂Cl₄(μ‐L)₂·2CH₂Cl₂ ( 1 ), Pd₂Cl₄(μ‐L)₂ ( 2 ), and [Cu₂(μ‐I)₂L₂]_n ( 3 ). Single crystal X‐ray diffraction studies show that complexes 1 and 2 display a similar bimetallic twelve‐membered ring structure, while complex 3 consists of one‐dimensional polymeric chains, which are further connected into a 2‐D supramolecular framework through hydrogen bonds. In the binuclear complexes 1 and 2 , the ligand L serves as a bridge with the N and P as coordination atoms, but in the polymeric complex 3 , both bridging and chelating modes are adopted by the ligand. The spectroscopic properties of complexes 1 ‐ 3 as well as L have been investigated, in which complex 3 exhibits intense photoluminescence originating from intraligand charge transfer (ILCT) π→π* and metal‐to‐ligand charge‐transfer (MLCT) excited states both in acetonitrile solution and solid state, respectively.     

Nickel(II), Cadmium(II), and Copper(II) Complexes Based on Ditopic Terpyridine Derivative Ligand: Syntheses,Crystal Structures,and Luminescent Properties

Three complexes with the ditopic ligand 4′‐[4‐(quinolin‐8‐yloxymethyl)phenyl]‐2,2′:6′,2′′‐terpyridine (abbreviated as L ), [Ni(L)₂](CH₃COO)₂ ( 1 ), [Cd(L)₂](ClO₄)₂ ( 2 ), and [Cu₂(L)₂](ClO₄)₄ · 4DMF ( 3 ), were synthesized and characterized by elemental analysis, IR spectroscopy, and structurally analyzed by X‐ray single‐crystal diffraction. Interestingly, in complexes 1 and 2 , two ligands adopt a tridentate chelating pattern where the oxaquinoline group is non‐coordinated and coordinate with one M^II ion (M = Ni for 1 , M = Cd for 2 ) to form a mononuclear unit. In complex 3 , two ligands bridge two Cu^II ions by pyridyl N atoms, ethereal O atoms, and quinolyl N atoms in a head‐to‐tail mode to generate a dinuclear [Cu₂L₂] unit. Moreover, extended 1D and 2D supramolecular architectures are further constructed in 1 – 3 by multiple secondary interactions such as aromatic stacking and hydrogen bonding. Notably, the structural diversity of complexes 1 – 3 can be properly assigned to the central metal ions that have distinct coordination preferences. In addition, luminescent properties of the ligand and complex 2 were also investigated.     

Formation and Dynamic Behavior of Mono‐ and Bimetallic Cadmium(II) Porphyrin Complexes: Allosteric Control of Coupled Intraligand Metal Migrations

The complexation behavior of a bis‐strapped porphyrin ligand ( 1 ) towards Cd^II has been investigated by ¹H and ¹¹³Cd NMR spectroscopy with the help of X‐ray diffraction structures. The presence of an overhanging carboxylic acid group on each side of the macrocycle is responsible for the instantaneous insertion of the metal ion(s) at room temperature, and allows the formation of bimetallic species with unusual coordination modes at the origin of unique dynamic behaviors. In the absence of base, a C₂‐symmetric bimetallic complex ( 1Cd₂ ) is readily formed, in which the porphyrin acts as a bridging ligand. Both Cd^II ions are bound to the N core and to a COO^? group of a strap. In contrast, the presence of a base induces a two‐step binding process with the successive formation of mono and bimetallic species ( 1^Cd and 1_Cd?CdOAc ). Formally, a Cd^II ion is first inserted into the N core and experiences a strong out‐of‐plane (OOP) displacement due to the binding of an overhanging carbonyl group in an apical position. A second Cd^II ion then binds exclusively to the strap on the opposite side, in a so‐called hanging‐atop (HAT) coordination mode. These two complexes display a fluxional behavior that relies on intraligand migration processes of the metal ion(s). In 1^Cd , the Cd^II ion exchanges between the two equivalent overhanging apical ligands by funneling through the porphyrin ring. In 1_Cd?CdOAc , the two Cd^II ions exchange their coordination mode (HAT?OOP) in a concerted way while staying on their respective side of the macrocycle, in a so‐called Newton’s cradle‐like motion. The intramolecular pathway was notably evidenced by variable temperature ¹¹³Cd heteronuclear NMR experiments. This coupled motion of the Cd^II cations is under allosteric control; the addition of an acetate anion (the allosteric effector) to the “resting” C₂‐symmetric complex 1Cd₂ affords the dissymmetric complex 1_Cd?CdOAc and triggers equilibrium between its two degenerate states. The rate of the swinging motion further depends on the concentration of AcO^?, with a higher concentration leading to a slower motion. As compared with the related Pb^II and Bi^III bimetallic complexes, the Newton’s cradle‐like motion proceeds faster with the smaller Cd^II ion. These results open the way to novel multistable devices and switches.     

Synthesis and Structural Characterization of Metal Complexes of 2‐Formylpyrrole‐4N‐ethylthiosemicarbazone (4 EL1) and 2‐Acetylpyrrole‐4N‐ethylthiosemicarbazone (4 EL2)

The reactions of ⁴N‐ethyl‐2‐[1‐(pyrrol‐2‐yl)methylidene(hydrazine carbothioamide ( 4 EL₁ ) and ⁴N‐ethyl‐2[1‐(pyrrol‐2‐yl)ethylidene(hydrazine carbothioamide ( 4 EL₂ ) with Group 12 metal halides afforded complexes of types [M(L)₂X₂] (M = Zn, Cd; L = 4 EL₁, 4 EL₂; X = Cl, Br, I; 1 – 6 , 14 – 19 ) and [M(L)X₂] (M = Hg; L = 4 EL₁, 4 EL₂; X = Cl, Br, I; 7 – 9 , 20 – 22 ). In addition, reaction of 4 EL₁ with salts of Cu^II, Ni^II, Pd^II and Pt^II afforded compounds of type [M(4 EL₁–H)₂] ( 10 – 13 ). The new compounds were characterized by elemental analysis, FAB mass spectrometry, IR and electronic spectroscopy and, for sufficiently soluble compounds, ¹H, ¹³C and, when appropriate, ¹¹³Cd or ¹⁹⁹Hg NMR spectrometry. The spectral data suggest that in their complexes with Group 12 metal cations, both thiosemicarbazones are neutral and S‐monodentate; and for [Zn(4 EL₁)₂I₂] ( 3 ), [Cd(4 EL₁)₂Br₂] ( 5 ) and [Hg(4 EL₁)Cl₂]₂ ( 7 ) this was confirmed by X‐ray diffractometry. By contrast, in its complexes with Cu^II and Group 10 metal cations, 4 EL₁ is monodeprotonated and S,N‐bidentate, as was confirmed by X‐ray diffractometry for [Ni(4 EL₁–H)₂] ( 11 ) and [Pd(4 EL₁–H)₂] ( 12 ).     

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.     

Syntheses,Crystal Structures,and Properties of Lead(II), ­Zinc(II), and Manganese(II) Complexes Constructed from 2, 3, 5, 6‐Tetraiodo‐1, 4‐benzenedicarboxylic Acid

Three new coordination compounds, [Pb(HBDC‐I₄)₂(DMF)₄]( 1 ) and [M(BDC‐I₄)(MeOH)₂(DMF)₂]_n (M = Zn^II for 2 and Mn^II for ( 3 ) (H₂BDC‐I₄ = 2, 3, 5, 6‐tetraiodo‐1, 4‐benzenedicarboxylic acid), were synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and X‐ray single crystal structure analysis. Single‐crystal X‐ray diffraction reveals that 1 crystallizes in the monoclinic space group C2/c and has a discrete mononuclear structure, which is further assembled to form a two‐dimensional (2D) layer through intermolecular O–H ··· O and C–H ··· O hydrogen bonding interactions. The isostructural compounds 2 and 3 crystallize in the space group P2₁/c and have similar one‐dimensional (1D) chain structures that are extended into three‐dimensional (3D) supramolecular networks by interchain C–H ··· π interactions. The Pb^II and Zn^II complexes 1 and 2 display similar emissions at 472 nm in the solid state, which essentially are intraligand transitions.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Complexes of N‐Thiophosphorylthiourea tBuNHC(S)NHP(S)(OiPr)2 with Zinc(II), Cadmium(II), Nickel(II), and Cobalt(II) Cations

Reaction of the potassium salt of N‐thiophosphorylthiourea tBuNHC(S)NHP(S)(OiPr)₂ ( HL ) with Zn^II, Cd^II, Ni^II and Co^II in aqueous EtOH leads to complexes of common formula M(L‐S,S′)₂ ( ML₂ ). Complexes were investigated by IR, UV‐Vis, ¹H and ³¹P{¹H} NMR spectroscopy and microanalysis The structure of complex NiL₂ was investigated by single crystal X‐ray diffraction analysis. The nickel(II) ion has a squre‐planar environment, S₄, with two anionic ligands involving 1,5‐S,S′‐coordination mode. The ligands are bound in a trans configuration.     

Ein Beitrag zu Rhenium(II)‐, Osmium(II)‐ und Technetium(II)‐Thionitrosylkomplexen vom Typ [M(NS)Cl4py]—: Darstellung,Strukturen und EPR‐Spektren

A Contribution to Rhenium(II)‐, Osmium(II)‐, and Technetium(II)‐Thionitrosyl‐Complexes: Preparation, Structures, and EPR‐Spectra The reaction of [Re^VINCl₄]^— and [Os^VINCl₄]^— with S₂Cl₂ leads to the formation of the thionitrosyl complexes [M^II(NS)Cl₄]^— (M = Re, Os) which could not be isolated as pure compounds. Addition of pyridine to the reaction mixture results in the formation of the stable compounds trans‐(Ph₄P)[Os^II(NS)Cl₄py], trans‐(Hpy)[Os^II(NS)Cl₄py], trans‐(Ph₄P)[Re^II(NS)Cl₄py], and cis‐(Ph₄P)[Re^II(NS)Cl₄py]. The crystal structure analyses show for trans‐(Ph₄P)[Os^II(NS)Cl₄py] (monoclinic, P2₁/n, a = 12.430(3)Å, b = 18.320(4)Å, c = 15.000(3)Å, β = 114.20(3)°, Z = 4), trans‐(Hpy)[Os^II(NS)Cl₄py] (monoclinic, P2₁/n, a = 7.689(1)Å, b = 10.202(2)Å, c = 20.485(5)Å, β = 92.878(4)°, Z = 4), trans‐(Ph₄P)[Re^II(NS)Cl₄py] (triclinic, P1¯, a = 9.331(5)Å, b = 12.068(5)Å, c = 15.411(5)Å, α = 105.25(1)°, β = 90.23(1)°, γ = 91.62(1)°, Z = 2), and cis‐(Ph₄P)[Re^II(NS)Cl₄py] (monoclinic, P2₁/c, a = 10.361(1)Å, b = 16.091(2)Å, c = 17.835(2)Å, β = 90.524(2)°, Z = 4) M‐N‐S angles in the range 168‐175°. This indicates a nearly linear coordination of the NS ligand. The metal atom is octahedrally coordinated in all cases. The rhenium(II) thionitrosyl complexes (5d⁵ “low‐spin” configuration, S = 1/2) are studied by EPR in the temperature range 295 > T > 130 K. In addition to the detection of the complexes formed during the reaction of [Re^VINCl₄]^— with S₂Cl₂ EPR investigations on diamagnetically diluted powders and single crystals of the system (Ph₄P)[Re^II/Os^II(NS)Cl₄py] are reported. The ^{185, 187}Re hyperfine parameters are used to get information about the spin‐density distribution of the unpaired electron in the complexes under study. [Tc^VINCl₄]^— reacts with S₂Cl₂ under formation of [Tc^II(NS)Cl₄]^— which is not stable and decomposes under S₈ elimination and rebuilding of [Tc^VINCl₄]^— as found by EPR monitoring of the reaction.     

3‐(Arylhydrazono)pentane‐2, 4‐diones and their Complexes with Copper(II) and Nickel(II) — Synthesis and Crystal Structures

A series of new 3‐(arylhydrazono)pentane‐2, 4‐diones ( 1 ‐ 6 ) synthesized from pentane‐2, 4‐dione and diazonium salts of respective anilines using the procedure of Japp‐Klingemann are described. Complexes with Cu^II and Ni^II salts are prepared ( 7 ‐ 10 , respectively). Spectroscopic properties of these compounds have been studied and X‐ray crystal structures of selected hydrazones ( 3 , 4 , 6 ) and of the hydrazone complexes ( 7 ‐ 10 ) are reported. The structures of the uncomplexed hydrazones feature an intramolecular N‐H···O interaction to yield a six‐membered H‐bond ring reflecting preference of the hydrazone tautomeric structure. All the complexes are mononuclear 2:1 (L:M) structures of six‐membered chelate type involving N₂O₂ binding sites that are quadratic arranged but differ in the entire coordination environment dependent on the metal and the ligand substitution including distorted octahedral and quadratic pyramidal coordination geometries in the Cu^II complexes 7 and 8 or nearly regular square planar coordination geometry in the Ni^II complexes 9 and 10 , respectively. In the crystal packings, strong and weak H‐bond interactions cause supramolecular network structures.     

(Croconato‐κ2O,O′)bis­(1,10‐phenanthroline‐κ2N,N′)cobalt(II), and the nickel(II) and copper(II) analogues

The title complexes, [M(C₅O₅)(C₁₂H₈N₂)₂], with M = Co^II, Ni^II and Cu^II, all lie across twofold rotation axes, around which two 1,10‐phenanthroline ligands are arranged in a chiral propeller manner. The Co^II and Ni^II complexes are isostructural, with octa­hedral coordination geometry, while the local geometry of the Cu^II complex is severely distorted from octa­hedral.     

Reversible Phase Transformation and Luminescence of Cadmium(II)–Dipyridylamide‐Based Coordination Frameworks

We have synthesized a series of 1D double‐zigzag ({[Cd(paps)₂(H₂O)₂](ClO₄)₂}_n ( 1 ), {[Cd(papo)₂(H₂O)₂](ClO₄)₂}_n ( 3 ), and {[Cd(papc)₂(H₂O)₂](ClO₄)₂}_n ( 5 )) and 2D polyrotaxane frameworks ([Cd(papc)₂(ClO₄)₂]_n ( 6 )) by the reaction of Cd(ClO₄)₂ with dipyridylamide ligands N,N′‐bis(pyridylcarbonyl)‐4,4′‐diaminodiphenyl thioether (paps), N,N′‐bis(pyridylcarbonyl)‐4,4′‐diaminodiphenyl ether (papo), and N,N′‐(methylenedi‐p‐phenylene)bispyridine‐4‐carboxamide (papc), respectively, where their molecular structures have been determined by X‐ray diffraction studies. Based on the powder X‐ray data (PXRD) of compound 3 and its Zn^II analogue, heating the double‐zigzag framework of compound 3 can give the polyrotaxane framework of [Cd(papo)₂(ClO₄)₂]_n ( 4 ) and grinding this powder sample in the presence of moisture resulted in its complete conversion back into the pure double‐zigzag framework. In addition, heating the double‐zigzag frameworks of compounds 1 and 5 can induce structural transformation into their respective polyrotaxanes, whereas grinding these solid samples in the presence of moisture did not lead to the formation of the double zigzags. Herein, we investigated the effect of the metal (from Zn^II to Cd^II) on the assembly process and luminescence properties, as well as on the particularly intriguing structural transformation of a series of papx‐based frameworks. In fact, the assembly behavior and luminescence properties of the Cd^II? papx and Zn^II? papx frameworks were really similar. However, both Zn^II? papx (x=s, o) frameworks can perform reversible structural transformation, but only the Cd^II? papo framework can do it. Therefore, a delicate metal effect on such a new structural transformation can be observed.     

Coordination Centres of Purine Nucleotides: Adenosine‐5′‐diphosphate and Adenosine‐5′‐triphosphate in their Reactions with Nickel(II), Cobalt(II) and Tetramines

Interactions between the nucleotides: adenosine‐5′‐diphosphate (ADP) and adenosine‐5′‐triphosphate (ATP) with Ni^II and Co^II ions, as well as with spermine (Spm) and 1,11‐diamine‐4,8‐diazaundecane (3,3,3‐tet) are the subject of this study. Composition and stability constants of mixed complexes thus formed have been determined on the basis of the potentiometric measurements, whereas interaction centres in ligands have been identified by VIS and NMR spectral parameter analysis. Mixed tetraprotonated complexes with Ni^II, i.e. Ni(ADP)H₄(Spm), Ni(ATP)H₄(Spm), Ni(ADP)H₄(3,3,3‐tet) and Ni(ATP)H₄(333‐tet), are identified as ML·······L′ type adducts, in which the main coordination centre is the nucleotide nitrogen N(1) or N(7) donor atom, and the fully protonated polyamine is engaged in noncovalent interactions with nucleotide phosphate group oxygen atoms. Ni(ADP)H₂(Spm), Ni(ATP)H₂(Spm), Ni(ADP)H₂(3,3,3‐tet) and Ni(ATP)H₂(3,3,3‐tet) complexes represent the {N3} coordination type In diprotonated mixed complexes of Ni^II with spermine are weak noncovalent interligand interactions, providing an additional stabilising effect. Formation of ML·······L′ type molecular complexes has been observed in systems with Co^II: Co(ADP)H₄(Spm), Co(ATP)H₄(Spm), Co(ADP)H₄(3,3,3‐tet) and Co(ATP)H₄(3,3,3‐tet), in which the N(7) atom and oxygen atoms of the phosphate group are involved in coordination and the fully protonated polyamine is engaged in noncovalent interactions with the nucleotide N(1).     

Interaction of manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) with acetylhydrazine, formed in situ; first crystal structure of tris(acetylhydrazine) nickel(II) perchlorate

A series of transition metal complexes of the type [M(ah)₃](ClO₄)₂ (1–6) [M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II and Zn^II, ah = acetylhydrazine] have been prepared by the reaction of M(ClO₄)₂ · 6H₂O with acetylhydrazine formed in situ by the reaction of hydrazine hydrate and acetylsalicylic acid methyl ester. The chelating behaviour of acetylhydrazine and overall geometry of these complexes have been spectroscopically investigated by means of FT-IR, ¹H-n.m.r. and electronic spectral techniques, as well as by elemental analysis data, molar conductance values and magnetic susceptibility measurements. Single X-ray structure determination of complex (4) revealed three acetylhydrazine ligands coordinated to nickel ion in a bidentate manner maintaining an octahedral environment. In all other complexes too, an octahedral geometry has been proposed on the basis of results obtained by various physico-chemical studies.