Diamond‐ and Graphite‐Like Octacyanometalate‐Based Polymers Induced by Metal Ions

By using cyclohexane‐1,2‐diamine (chxn), Ni(ClO₄)₂ ? 6H₂O and Na₃[Mo(CN)₈] ? 4H₂O, a 3D diamond‐like polymer {[Ni^II(chxn)₂]₂[Mo^IV(CN)₈] ? 8H₂O}_n ( 1 ) was synthesised, whereas the reaction of chxn and Cu(ClO₄)₂ ? 6H₂O with Na₃[M^V(CN)₈] ? 4H₂O (M=Mo, W) afforded two isomorphous graphite‐like complexes {[Cu^II(chxn)₂]₃[Mo^V(CN)₈]₂ ? 2H₂O}_n ( 2 ) and {[Cu^II(chxn)₂]₃[W^V(CN)₈]₂ ? 2H₂O}_n ( 3 ). When the same synthetic procedure was employed, but replacing Na₃[Mo(CN)₈] ? 4H₂O by (Bu₃NH)₃[Mo(CN)₈] ? 4H₂O (Bu₃N=tributylamine), {[Cu^II(chxn)₂Mo^IV(CN)₈][Cu^II(chxn)₂] ? 2H₂O}_n ( 4 ) was obtained. Single‐crystal X‐ray diffraction analyses showed that the framework of 4 is similar to 2 and 3 , except that a discrete [Cu(chxn)₂]²⁺ moiety in 4 possesses large channels of parallel adjacent layers. The experimental results showed that in this system, the diamond‐ or graphite‐like framework was strongly influenced by the inducement of metal ions. The magnetic properties illustrate that the diamagnetic [Mo^IV(CN)₈] bridges mediate very weak antiferromagnetic coupling between the Ni^II ions in 1 , but lead to the paramagnetic behaviour in 4 because [Mo^IV(CN)₈] weakly coordinates to the Cu^II ions. The magnetic investigations of 2 and 3 indicate the presence of ferromagnetic coupling between the Cu^II and W^V/Mo^V ions, and the more diffuse 5d orbitals lead to a stronger magnetic coupling interaction between the W^V and Cu^II ions than between the Mo^V and Cu^II ions.     

Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties

The use of the [Fe^III(AA)(CN)₄]^? complex anion as metalloligand towards the preformed [Cu^II(valpn)Ln^III]³⁺ or [Ni^II(valpn)Ln^III]³⁺ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H₂valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu^II(valpn)Ln^III(H₂O)₃(μ‐NC)₂Fe^III(phen)(CN)₂ {(μ‐NC)Fe^III(phen)(CN)₃}]NO₃ ? 7 H₂O}_n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃] ? NO₃ ? H₂O ? CH₃CN ( 4 ) were obtained with the [Cu^II(valpn)Ln^III]³⁺ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni^II(valpn)Ln^III(ONO₂)₂(H₂O)(μ‐NC)₃Fe^III(bipy)(CN)] ? 2 H₂O ? 2 CH₃CN}_n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni^II(valpn)Ln^III]³⁺ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃]⁺, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe^III(bipy)(CN)₄} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni^II(valpn)Ln^III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu^II?Ln^III ( 1 – 3 ) and Ni^II?Ln^III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe^III and either Ni^II ( 5 – 7 ) or Cu^II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τ_o) and energy barrier (E_a) through the Arrhenius equation being 2.0×10^?12 s and 29.1 cm^?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni^II–Dy^III) and single cyanide (Fe^III–Ni^II) pathways are masked by the depopulation of the Stark levels of the Dy^III ion, this feature most likely accounting for the continuous decrease of χ_M T upon cooling observed for this last compound.     

Reversible Solvatomagnetic Switching in a Spongelike Manganese(II)–Copper(II) 3D Open Framework with a Pillared Square/Octagonal Layer Architecture

The concept of “molecular magnetic sponges” was introduced for the first time in 1999 by the creative imagination of the late Olivier Kahn. It refers to the exotic spongelike behavior of certain molecule‐based materials that undergo a dramatic change of their magnetic properties upon reversible dehydration/rehydration processes. Here we report a unique example of a manganese(II)–copper(II) mixed‐metal–organic framework of formula [Na(H₂O)₄]₄[Mn₄{Cu₂(mpba)₂(H₂O)₄}₃]? 56.5 H₂O ( 1 ) (mpba=N,N′‐1,3‐phenylenebis(oxamate)). Compound 1 possesses a 3D Mn^II₄Cu^II₆ pillared layer structure with mixed square and octagonal pores of approximate dimensions 1.2×1.2 nm and 2.1×3.0 nm, respectively, hosting a large amount of crystallization H₂O molecules and hydrated Na^I countercations as guests. It reversibly switches from a crystalline hydrated phase with long‐range ferromagnetic ordering at a rather high critical temperature (T_c) of 22.5 K to an amorphous dehydrated phase with T_c as low as 2.3 K, which is accompanied by a breathing‐type dynamic effect involving a large crystal volume (ca. 45 %) and color changes after water desorption/adsorption. The combination of both the open‐framework structure and the spongelike optical, mechanical, and magnetic switching behavior in this new class of oxamato‐based porous magnets offers fascinating possibilities in designing multifunctional materials for host–guest molecular sensing.     

Synthesis,Crystal Structure,and Characterization of Two Oxamido‐bridged NiIICuIINiII Heteronuclear Complexes

Two new trinuclear complexes [Cu^II(Ni^IIX₁)₂(C₂H₅OH)₂]· (ClO₄)₂·2(CH₃OH) ( 1 ) and [Cu^II(Ni^IIX₂)₂(H₂O)]·(ClO₄)₂· 0.75(H₂O) ( 2 ) (X₁ = dianion of 5,6;13,14‐dibenzo‐7,12‐bis(ethoxycarboxyl)‐9‐methyl‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca‐7,11‐diene. X₂ = dianion of 5,6;13,14‐dibenzo‐9,10‐cyclohexano‐7,12‐bis(ethoxycarboxyl)‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca7,11‐diene.) have been synthesized and characterized by single crystal X‐ray analysis, elemental analysis, IR, UV and EPR spectroscopies. The complexes consist of Ni^IICu^IINi^II heteronuclear cationic entities. The central Cu^II atom of 1 lies in an octahedral coordination environment, while that of 2 resides in a square‐pyramidal coordination sphere. The adjacent trinuclear units of 1 are linked together through π‐π stacking interactions resulting in a 1D supramolecular chain, whereas the π‐π stacking interactions between the contiguous units of 2 lead to a 2D structure. The EPR spectra of the two complexes show a signal of an axially elongated octahedral Cu^II system in 1 and an axially elongated square‐pyramidal Cu^II system in 2 , respectively. The hyperfine splitting of the Cu^II atoms (I^Cu = 3/2) has also been observed in the EPR spectra.     

Hydrothermal synthesis and structural characterization of two new reduced phosphomolybdates based on an organoamine template and copper ion

Two new compounds, (H₂en)₃(H₂enMe)₄(H₃O){Cu^I[Mo^V ₆O₁₂(OH)₃(HPO₄)(PO₄)₃]₂}?·?6H₂O (1) and (H₂enMe)₄{Cu^ICu^II[Mo^V ₆O₁₂(OH)₃(PO₄)(HPO₄)₂(H₂PO₄)]₂}?·?3H₂O (2), were hydrothermally synthesized and characterized by elemental analysis, IR, TGA, and single-crystal X-ray diffraction analysis. Crystallographic analysis reveals that 1 is constructed from cluster anions {Cu^I[Mo^V ₆O₁₂(OH)₃(HPO₄)(PO₄)₃]₂}^15?, protonated organic amines, and water molecules. Each cluster is bridged through hydrogen bonds to form a 3-D supermolecular structure. For 2, {Cu^I[Mo^V ₆O₁₂(OH)₃(PO₄)(HPO₄)₂(H₂PO₄)]₂}^11? are connected by Cu^II cations to form an infinite chain. The formation of 1 and 2 reveals that organoamines influence the structures of the crystals.     

New Entangled Coordination Networks Based on Charge‐Tunable Keggin‐Type Polyoxometalates

Investigation into a hydrothermal reaction system with transition‐metal (TM) ions, 1,4‐bis(1,2,4‐triazol‐1‐lmethyl)benzene (BBTZ) and various charge‐tunable Keggin‐type polyoxometalates (POMs) led to the preparation of four new entangled coordination networks, [Co^II(HBBTZ)(BBTZ)_2.5][PMo₁₂O₄₀] ( 1 ), [Cu^I(BBTZ)]₅[BW₁₂O₄₀] ? H₂O ( 2 ), [Cu^II(BBTZ)]₃[AsW^V₃W^VI₉O₄₀] ? 10 H₂O ( 3 ), and [Cu^II₅(BBTZ)₇(H₂O)₆][P₂W₂₂Cu₂O₇₇(OH)₂] ? 6 H₂O ( 4 ). All compounds were characterized by using elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The mixed valence of W centers in compound 3 was further confirmed by using XPS spectroscopy and bond‐valence sum calculations. In the structural analysis, the entangled networks of 1 – 4 demonstrate zipper‐closing packing, 3D polythreading, 3D polycatenation, and 3D self‐penetration, respectively. Moreover, with the enhancement of POM negative charges and the use of different TM types, the number of nodes in the coordination networks of 1 – 4 increased and the basic metal–organic building motifs changed from a 1D zipper‐type chain (in 1 ) to a 2D pseudorotaxane layer (in 2 ) to a 3D diamond‐like framework (in 3 ) and finally to a 3D self‐penetrating framework (in 4 ). The photocatalytic properties of compounds 1 – 4 for the degradation of methylene blue under UV light were also investigated; all compounds showed good catalytic activity and the photocatalytic activity order of Keggin‐type species was initially found to be {XMo₁₂O₄₀}>{XW₁₂O₄₀}>{XW_12?nTM_nO₄₀}.     

Crystal Structure and Magnetic Properties of Trinuclear Transition Metal Complexes (MnII,CoII, NiII and CuII) with Bridging Sulfonate-Functionalized 1,2,4-Triazole Derivatives

Here we present the synthesis, structure and magnetic properties of complexes of general formula (Mn)(Me₂NH₂)₄][Mn₃(μ-L)₆(H₂O)₆] and (Me₂NH₂)₆[M₃(μ-L)₆(H₂O)₆] (M = Co^II, Ni^II and Cu^II); L⁻² = 4-(1,2,4-triazol-4-yl) ethanedisulfonate). The trinuclear polyanions were isolated as dimethylammonium salts, and their crystal structures determined by single crystal and powder X-ray diffraction data. The polyanionic part of these salts have the same molecular structure, which consists of a linear array of metal(II) ions linked by triple N1-N2-triazole bridges. In turn, the composition and crystal packing of the Mn^II salt differs from the rest of the complexes (with six dimethyl ammonia as countercations) in containing one Mn⁺² and four dimethyl ammonia as countercations. Magnetic data indicate dominant intramolecular antiferromagnetic interactions stabilizing a paramagnetic ground state. Susceptibility data have been successfully modeled with a simple isotropic Hamiltonian for a centrosymmetric linear trimer, H = −2J (S₁S₂ + S₂S₃) with super-exchange parameters J = −0.4 K for Mn^II, −7.5 K for Ni^II and −45 K for Cu^II complex. The magnetic properties of these complexes and their easy processing opens unique possibilities for their incorporation as magnetic molecular probes into such hybrid materials as magnetic/conducting multifunctional materials or as dopant for organic conducting polymers.     

Complexes of NS and NSO donor ligands. Nickel(II), copper(II) and cobalt(II) complexes of glyoxal bis(morpholineN-thiohydrazone) and diacetyl bis(morpholineN-thiohydrazone)

Summary Reactions of glyoxal bis(morpholineN-thiohydrazone), H₂gbmth, with NiCl₂·6H₂O, Ni(OAc)₂·4H₂O, Ni(acac)₂· H₂O, CuCl₂·2H₂O, Cu(OAc)₂·H₂O, Cu(acac)₂, CoCl₂· 6H₂O, Co(OAc)₂·4H₂O and Co(acac)₂·2H₂O yield complexes of the type [M(gbmth)], [M=Ni^II, Cu^II or Co^II]. Diacetyl reacts with morpholineN-thiohydrazide in the presence of nickel salts to yield [Ni^II(dbmth)], [Ni^II(dmth)(OAc)]H₂O and [Ni^II(Hdmth)(NH₃)Cl₂] involving N₂S₂ and NSO donor ligands. Copper and cobalt complexes of N₂S₂ and NSO donor ligands with compositions [Cu^II(dbmth)], [Co^II(dbmth)]·4H₂O and [Co^II(H₂dbmth)]Cl₂, have been isolated. The compounds have been characterised by elemental analyses, magnetic moments, molar conductance values and spectroscopic (electronic and infrared) data.     

Synthesis and characterization of new metal complexes of thiosemicarbazone derived from 4-phenyl-3-thiosemicarbazide and chromone-3-carboxaldehyde

Summary The reaction between chromone-3-carboxaldehyde-4-phenylthiosemicarbazone (HCPT) and some hydrated metal salts of Co^II, Ni^II and Cu^II give complexes of the type [Cu(HCPT)Cl₂],[Cu(CPT)BrH₂O],[Cu(CPT)₂]·2H₂O, [Ni(CPT)₂(H₂O)₂]·2H₂O, [Co(CPT)₂(OAc)] and [Co(CPT)₂(H₂O)₂]X·2H₂O (where X=Cl or Br). The metal complexes were characterized by elemental analyses, molar conductivities, and spectal (i.r. and visible) and magnetic studies. I.r. spectra show that the HCPT coordinates in the thione or thiol form and behaves in a bidentate manner. Also, HCPT behaves as an oxidizing agent towards Co^II forming diamagnetic Co^III complexes. An octahedral structure is proposed for both Co^III and Ni^II complexes, while a square-planar structure is proposed for Cu^II complexes on the basis of magnetic and spectral measurements.     

Preparation,Crystal Structures,and Thermal Studies of Alkaline Earth Nitrocarboxylates

The preparation, crystal structures, and thermal properties of [Ca(pyr)₂(4‐nba)₂]_n ( 1 ) (pyr = pyrazole; 4‐nba = 4‐nitrobenzoate) {[Ca(H₂O)₂(3‐npth)] · H₂O}_n ( 2 ) (3‐npth = 3‐nitrophthalate), [Mg(H₂O)₅(3‐npth)] · 2H₂O ( 3 ), and [Mg(H₂O)₄(2‐nba)₂] ( 4 ) (2‐nba = 2‐nitrobenzoate) are reported. The anhydrous Ca^II compound 1 and the diaqua Ca^II‐3‐nitrophthalate monohydrate 2 are one‐dimensional coordination polymers containing a hexacoordinate Ca^II ion located on a center of inversion in 1 and a heptacoordinated Ca^II ion in 2 . In 1 , the 4‐nitrobenzoate moiety acts as a μ₂‐bridging bidentate ligand, whereas the 3‐nitrophthalate anion exhibits a μ₃‐bridging pentadentate coordination mode in 2 . The hexacoordinate Mg^II‐containing compounds 3 and 4 do not contain a [Mg(H₂O)₆]²⁺ unit and the central Mg^II ion is coordinated to at least one monodentate carboxylate unit namely the monodentate 3‐npth molecule in 3 and two trans monodentate 2‐nba molecules in 4 . Hydrogen bonding between the lattice water molecules results in the formation of a water dimer in 3 . A comparative study of 17 alkaline earth nitrocarboxylates is described.     

New Mechanistic Insight into Stepwise Metal‐Center Exchange in a Metal–Organic Framework Based on Asymmetric Zn4 Clusters

Herein, a mechanism of stepwise metal‐center exchange for a specific metal–organic framework, namely, [Zn₄(dcpp)₂(DMF)₃(H₂O)₂]_n (H₄dcpp=4,5‐bis(4′‐carboxylphenyl)phthalic acid), is disclosed for the first time. The coordination stabilities between the central metal atoms and the ligands as well as the coordination geometry are considered to be dominant factors in this stepwise exchange mechanism. A new magnetic analytical method and a theoretical model confirmed that the exchange mechanism is reasonable. When the metathesis reaction occurs between Cu^II ions and framework Zn^II ions, the magnetic exchange interaction of each pair of Cu^II centers gradually strengthens with increasing amount of framework Cu^II ions. By analyzing the changes of coupling constants in the Cu‐exchanged products, it was deduced that Zn4 and Zn3 are initially replaced, and then Zn1 and Zn2 are replaced later. The theoretical calculation further verified that Zn4 is replaced first, Zn3 next, then Zn1 and Zn2 last, and the coordination stability dominates the Cu/Zn exchange process. For the Ni/Zn and Co/Zn exchange processes, besides the coordination stability, the preferred coordination geometry was also considered in the stepwise‐exchange behavior. As Ni^II and Co^II ions especially favor octahedral coordination geometry in oxygen‐ligand fields, Ni^II ions and Co^II ions could only selectively exchange with the octahedral Zn^II ions, as was also confirmed by the experimental results. The stepwise metal‐exchange process occurs in a single crystal‐to‐single crystal fashion.     

Synthesis and characterization of a coplanar-shaped hexa-CuII sandwiched arsenotungstate

An organic–inorganic coplanar-shaped hexa-Cu^II sandwiched hybrid, (H₂en){[Cu(en)₂]₂[Cu₂(en)₂Cu₄(H₂O)₂](B-α-AsW₉O₃₄)₂}?·?5H₂O (en?=?ethylenediamine) (1), has been synthesized via hydrothermal method and further characterized by IR spectroscopy, thermogravimetric analysis, and X-ray single-crystal diffraction. Single-crystal X-ray diffraction analysis shows that 1 contains an organic–inorganic hybrid polyoxoanion {Cu₂(en)₂Cu₄(H₂O)₂(B-α-AsW₉O₃₄)₂}^6?, which can be described as a coplanar-shaped hexa-Cu^II cluster sandwiched by two trivacant [B-α-AsW₉O₃₄]^9? fragments. Complex 1 represents a rare organic–inorganic coplanar-shaped hexa-Cu^II cluster sandwiched arsenotungstate. Magnetic susceptibility measurements indicate that 1 demonstrates ferromagnetic coupling interactions within the Cu^II centers.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Studies on 2-acetylthiophene-2-furoylhydrazone complexes of 3d-bivalent metal ions

Summary Metal(II) complexes of 2-acetylthiophene-2-furoylhydrazone (HL) of the types [VO(HL)SO₄], [Cu(HL)₂Cl₂(H₂O)], [M(HL)₂Cl₂] [M=Co^II, Ni^II, or Zn^II] and [ML₂(H₂O)₂] [M=Co^II, Ni^II, Cu^II or Zn^II] have been prepared and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility, visible, e.s.r. and i.r. spectral studies. The bonding and stereochemistry of the complexes are discussed.     

A new family of magnetic 2D coordination polymers based on [MV(CN)8]3− (M=Mo,W) and pre-programmed Cu2+ centres

The self-assembly of [M(CN)₈]³⁻ (M=Mo, W) anion and polyamine complexes of Cu^II[Cu(tetren)]²⁺ and [Cu(dien)(H₂O)₂]²⁺ (tetren=tetraethylenepentamine, dien=diethylenetriamine) in acidic aqueous solution gives (tetrenH₅)_0.8{Cu^II ₄[W^V(CN)₈]₄}·7.2H₂O 1, (tetrenH₅)_0.8{Cu^II ₄[Mo^V(CN)₈]₄}·7.2H₂O 2, (dienH₃){Cu^II ₃[W^V(CN)₈]₃}·4H₂O 3 and (dienH₃){Cu^II ₃[Mo^V(CN)₈]₃}·4H₂O 4 2D coordination polymers. All compounds are structure-related: the crystal structures of isomorphous 1–2 and 3–4, respectively, consist of double-layered cyano-bridged {Cu^II[W^V(CN)₈]⁻}_n square grid backbones and non-coordinated fully protonated polyamine countercations as well as H₂O molecules located between the sheets. The magnetic measurements reveal long range ferromagnetic ordering with sharp phase transitions at T_C in range 28–37 K and coercivity in range 30–225 Oe at liquid helium temperature, T=4.3 K.     

2-Aminoacetophenone-2-thenoylhydrazone complexes of bivalent 3d metal ions

Summary 2-Aminoacetophenone-2-thenoylhydrazone, Haath, C₄H₃SC(O)NHN=C(Me)C₆H₄NH₂-o, forms complexes with metal(II) salts of empirical compositions [VO(Haath)₂SO₄], [M(Haath)₂Cl₂] [M=Co^II, Ni^II, Cu^II or Zn^II] and [M(aath)₂] [M=V^IVO, Co^II, Ni^II, Cu^II or Zn^II] which have been characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, e.s.r., i.r. and n.m.r. (¹H and¹³C) spectral studies. X-ray and electron diffraction patterns have been obtained in order to elucidate the structure of the Cu^II complexes. Photoacoustic spectra of powder Ni^II complexes have been recorded and interpreted in the light of u.v./vis. spectra.     

Interaction of <Emphasis Type="Italic">E. coli</Emphasis> DNA with diazine-bridged late first row transition metal complexes derived from hexadentate compartmental ligands: an approach to DNA cleavage/binding studies

A series of binuclear Co^II, Ni^II, Cu^II and Zn^II complexes having μ-1,2 diazine bridging have been prepared and characterized by various physico-chemical methods. The hexadentate ligands were synthesized by condensing 3,5-dichloroformyl-1H-pyrazole with 2-hydrazinobenzothiazole (L¹H) or 4-aminoantipyrine (L²H) in 1:2 ratio. Gel electrophoresis data indicate cleavage of E. coli DNA to a minute extent by both [Co₂L²(μ-Cl)Cl₂(H₂O)₂]·H₂O and [Ni₂L²(μ-Cl)Cl₂(H₂O)₂]. Conversely, the data for the remaining complexes indicated binding but not cleavage. These results were confirmed by viscosity measurements and absorption spectral studies. An intercalative binding mode is predicted when the title complexes interact with DNA.     

Three Novel 1‐H‐Benzimidazole‐5‐Carboxylate‐Based Nickel(II)/Cobalt(II) Coordination Polymers: Synthesis,Crystal Structures,Luminescent, and Magnetic Properties

Three 1H‐benzimidazole‐5‐carboxylate (Hbic^–)‐based coordination polymers, {[Ni(H₂O)(Hbic)₂] · 2H₂O}_n ( 1 ), {[Ni(H₂O)₂(Hbic)₂] · 3H₂O}_n ( 2 ), and {[Co₂(H₂O)₄(Hbic)₄] · 4DMF · 3H₂O}_n ( 3 ) were obtained by reactions of the ligand H₂bic and Ni^II or Co^II salts in the presence of different structure directing molecules. They were structurally characterized by single‐crystal X‐ray diffraction, IR spectra, elemental analysis, thermal stability, luminescent, and magnetic measurements. Structural analysis suggests that the three polymers exhibit a 2D (4, 4) layer for 1 and 1D linear double chains for both 2 and 3 due to the variable binding modes and the specific spatial orientation of the Hbic^– ligand towards the different paramagnetic metal ions, which were further aggregated into different 3D supramolecular architectures by popular hydrogen‐bonding interactions. Weak and comparable antiferromagnetic couplings mediating by Hbic^– bridge are observed between the neighboring spin carriers for 2 and 3 , respectively. Additionally, complexes 1 – 3 also display different luminescence emissions at room temperature due to the ligand‐to‐metal charge transfer.     

Structural studies of 4-benzamido-1-o-aminoacetophenone-3-thiosemicarbazone complexes

Summary Complexes of Cu^II, Ni^II, Co^II, Zn^II, Cd^II and Hg^II with 4-benzamido-1-o-aminoacetophenone-3-thiosemicarbazone (H₂BATS) are reported and have been characterized by elemental analyses, molar conductivities, magnetic moments, spectral (visible, i.r.) and thermal (d.t.a., t.g., d.t.g.) measurements. I.r. spectra show that H₂BATS behaves as a dianionic, monoanionic or neutral tetradentate ligand or as a monoanionic tridentate ligand. [Cu₂(H₂BATS)Cl₂]·2H₂O and [Cu₂(H₂BATS)Ac₂]·2H₂O complexes are diamagnetic while [Co(HBATS)OH]·2H₂O and [Ni(HBATS)OH]·2H₂O are octahedral. All the complexes are non-electrolytes. Generally, the solid metal acetate complexes have a unique decomposition exotherm profile which can be used as a rapid and sensitive tool for the detection of acetate-containing complexes.     

Complexes of 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole with some bivalent metals ions

Summary The metal complexes of the type [M(SB)₂(H₂O)₂] and [M(SB)₂][where M = Mn^II, Co^II, Ni^II or Cu^II, M = Zn^II Cd^II, Hg^II and Pb^II and SBH = 2-(2-hydroxyacetophenone)imino-5-(p-anisyl)-1,3,4-oxadiazole] have been prepared and characterised by elemental analyses, thermal analyses, magnetic measurements, electronic and infrared spectral studies. The complexes [M(SB)₂(H₂O)₂] possess octahedral structures, whereas complexes [M(SB)₂] are tetrahedral. The crystal field parameters of the Co^II and Ni^II complexes are also calculated.