Construction of a series of 0D, 2D and 3D inorganic-organic hybrid coordination polymers based on octamolybdate and 2-(2-pyridyl)imidazole and its derivative

Four octamolybdate-based compounds, that is, Cu^II₂(L¹)₄(Mo₈O₂₆) (1), Cu^II₂(HL²)₄(Mo₈O₂₆)₂ (2), [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (3) and [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (4) (L¹ = 2-(2-pyridyl)imidazole, L² = 2-(1-(pyridine-3-ylmethyl)-1H-imidazol-2-yl)pyridine), have been hydrothermally synthesized via changing the reaction conditions and structurally characterized by single-crystal X-ray diffraction. With L¹ ligand, we obtained compound 1, which is a 0D molecule and extends to a 3D supramolecular structure via hydrogen-bonding interactions. By using L² instead of L¹ ligand, compound 2 comes into being which is as well a discrete molecule and further extended to a 3D supramolecular structure by hydrogen bonds. Intriguingly, compounds 3 and 4 are supramolecular isomers: the former is a 2D 4-connected network and the latter is a 3D (3,4)-connected framework. The measurements of diffuse reflectance for compounds 1-4 indicate that they are potential wide gap semiconductors.     

Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes

New complexes of formulae [Cu(HL²)(H₂O)(NO₃)](NO₃) (1), [{Cu(L¹)(tfa)}₂] (2), [{Cu(L¹)}₂(pz)](ClO₄)₂ (3) and {[{Cu(L¹)}₂(dca)](ClO₄)}_n (4), where HL¹ = pyridine-2-carbaldehyde thiosemicarbazone, HL² = pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, Htfa = trifluoroacetic acid (CF₃COOH), pz = pyrazine (C₄H₄N₂) and dca = dicyanamide [N(CN)₂]⁻, have been synthesized and characterized. The crystal structures of these compounds are built up of monomers (1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand (2 and 3) and 1D chains of dimers (4). In all the cases, square-pyramidal copper(II) ions are present, except for the square-planar ones in 3. Magnetic measurements show antiferromagnetic couplings in 2, 3 and 4. The susceptibility data were fitted by the Bleaney-Bowers’ equation for copper(II) dimers derived from H = -2JS₁S₂ being the obtained J/k values −4.8, −4.3 and −5.1 K for compounds 2-4, respectively. The magnetic susceptibility of the already known [{Cu(HL¹)(tfa)}₂](tfa)₂ compound has been also measured for the first time. The J/k value is -0.3 K, lower than that in 2. The nuclease activity of 3 and 4 has been analyzed.     

Synthesis and crystal structure of a salicylatooxovanadium(V) complex of an aminebis(phenolate) ligand: Kinetic studies on its formation from corresponding alkoxo complexes

Synthesis and single crystal X-ray structures of H₂L¹ and VO(L¹)(HL) [H₂L¹ = N,N-bis(2-hydroxy-3,5-ditertiarybutyl)-N′,N′-dimethylethylendiamine) or simply aminebis(phenol) and H₂L = salicylic acid) are reported here. The complex [VO(L¹)(HL)] is in distorted octahedral geometry under O₄N₂ donor environment where the basal core is defined by O(1), O(3), O(2) and N(5) atoms and two axial coordinates are occupied by O(4), an alkoxo-group and N(1), an imino-nitrogen atom. The electron spray mass spectrometric study on [VO(L¹)(HL)] in MeCN clearly points out the existence of single species in solution. Again, the ⁵¹V NMR of the bulk polycrystalline sample reveals that the complex [VO(L¹)(HL)] mainly exists in three out of four possible isomers. The formation of [VO(L¹)(HL)] from both [VO(L¹)(OMe)] and [VO(L¹)(OEt)] was followed kinetically by reacting with salicylic acid in MeCN. The presence of isosbestic point indicates a clean conversion of the reactants to product.     

Synthesis, structure, and properties of monomeric Fe(II), Co(II), and Ni(II) complexes of neutral N-(aryl)-2-pyridinecarboxamides

We have prepared and structurally characterized six-coordinate Fe(II), Co(II), and Ni(II) complexes of types [M^II(HL¹)₂(H₂O)₂][ClO₄]₂ (M = Fe, 1; Co, 3; and Ni, 5) and [M^II(HL²)₃][ClO₄]₂ · MeCN (M = Fe, 2 and Co, 4) of bidentate pyridine amide ligands, N-(phenyl)-2-pyridinecarboxamide (HL¹) and N-(4-methylphenyl)-2-pyridinecarboxamide (HL²). The metal centers in bis(ligand)-diaqua complexes 1, 3 and 5 are coordinated by two pyridyl N and two amide O atoms from two HL¹ ligands and six-coordination is completed by coordination of two water molecules. The complexes are isomorphous and possess trans-octahedral geometry. The metal centers in isomorphous tris(ligand) complexes 2 and 4 are coordinated by three pyridyl N and three amide O atoms from three HL² ligands. The relative dispositions of the pyridine N and amide O atoms reveal that the pseudo-octahedral geometry have the meridional stereochemistry. To the best of our knowledge, this work provides the first examples of structurally characterized six-coordinate iron(II) complexes in which the coordination is solely by neutral pyridine amide ligands providing pyridine N and amide O donor atoms, with or without water coordination. Careful analyses of structural parameters of 1-5 along with that reported in the literature [M^II(HL¹)₂(H₂O)₂][ClO₄]₂ (M = Cu and Zn) and [Co^III(L²)₃] have allowed us to arrive at a number of structural correlations/generalizations. The complexes are uniformly high-spin. Spectroscopic (IR and UV/Vis) and redox properties of the complexes have also been investigated.     

Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL)] (HL = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL¹), 3,5-bis(2-pyridyl)pyrazole (HL²), 3-methyl-5-(2-pyridyl)pyrazole (HL³) and 3-methyl-5-phenylpyrazole (HL⁴) with [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) or [PdCl₂(cod)] gives complexes with stoichiometry [PdCl₂(HL)₂] (HL = HL¹, HL², HL³), [Pt(L)₂] (L = L¹, L², L³) and [MCl₂(HL⁴)₂] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and ¹H NMR spectroscopies. The crystal and molecular structure of [PdCl₂(HL¹)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl₂(HL¹)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL¹ is not completely planar.     

Mononuclear iron(III) complexes supported by tripodal N3O ligands: Synthesis, structure and reactivity towards DNA cleavage

A new synthetic route to the known tripodal tetradentate N₃O ligand L¹ (HL¹ = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLⁿ (n = 2, 3) were prepared by a similar procedure. Treatment of HLⁿ (n = 1-3) with FeCl₃·6H₂O in hot methanol led to the mononuclear iron(III) complexes [Fe(Lⁿ)Cl₂] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L¹)Cl₂] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.     

Rhenium(III) and technetium(III) complexes with 2-mercapto-1,3-azole ligands and X-ray crystal structures

Reactions of labile [MCl₃(PPh₃)₂(NCMe)] (M = Tc, Re) precursors with 1H-benzoimidazole-2-thiol (H₂L¹), 5-methyl-1H-benzoimidazole-2-thiol (H₂L²) and 1H-imidazole-2-thiol (H₂L³), in the presence of PPh₃ and [AsPh₄]Cl gave a new series of trigonal bipyramidal M(III) complexes [AsPh₄]{[M(PPh₃)Cl(H₂L^1-3)₃]Cl₃} (M = Re, 1-3; M = Tc, 4-6). The molecular structures of 1 and 3 were determined by X-ray diffraction. When the reactions were carried out with benzothiazole-2-thiol (HL⁴) and benzoxazole-2-thiol (HL⁵), neutral paramagnetic monosubstituted M(III) complexes [M(PPh₃)₂Cl₂(L^4,5)] (M = Re, 8, 9; M = Tc, 10, 11) were obtained. In these compounds, the central metal ions adopt an octahedral coordination geometry as authenticated by single crystal X-ray diffraction analysis of 8 and 11. Rhenium and technetium complexes 1, 4 and rhenium chelate compounds 8, 9 have been also synthesized by reduction of [MO₄]⁻ with PPh₃ and HCl in the presence of the appropriate ligand. All the complexes were characterized by elemental analyses, FTIR and NMR spectroscopy.     

First microwave-assisted synthesis of an electron-rich phosphane and its coordination chemistry with platinum(II) and palladium(II)

The P-O ligand 3-(di(2-methoxyphenyl)phosphanyl)propionic acid (HL) was synthesized by a microwave-assisted reaction of a secondary phosphane. The coordination of HL to Pt^II yielded the neutral mononuclear complex trans-[PtCl(κ²-P,O-L)(κ-P-HL)] (1), while the reaction of PdClMe(η⁴-COD) (COD = 1,4-cyclooctadiene) with HL in the presence of NEt₃ gave the anionic Pd^II compound of the formula (HNEt₃)[PdClMe(κ²-P,O-L)] (2). Upon crystallization of the latter compound the neutral chloride-bridged dimetallic compound cis-[Pd(μ-Cl)Me(HL)]₂ (3) was obtained. HL, 1 and 3·CH₂Cl₂ have been characterized by single crystal X-ray structure analyses.     

Synthesis, crystal structures and characterization of three novel complexes with N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide as ligand

Reaction of the N-tosyl-ethylenediamine and salicylaldehyde forms a new sulfonamide Schiff base N-[2-(2-hydroxybenzylideneamino)ethyl]-4-methyl-benzene-sulfonamide (H₂L). Three novel complexes constructed from H₂L, namely, [M(HL)₂] · xH₂O (M = Cu, x = 0 for 1, M = Ni, x = 0 for 2 and M = Zn, x = 1 for 3) have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, X-ray powder diffraction (XRPD), FT-IR, UV-Vis, TGA and photoluminescence measurements. Complex hydrogen bonds, C-H···π and π-π stacking interactions lead 1-3 to present 1-D, 2-D and 3-D supramolecular architectures, respectively.     

Mononuclear manganese(III) catechol compounds as substrate adduct complexes for manganese-substituted intradiol cleaving catechol dioxygenases

The complexes [Mn(L₁)(tcc)] (1), [Mn(L₂)(tcc)] · H₂O · 0.5CH₃OH (2), [Mn(L₃)(tcc)] · CH₂Cl₂ (3), [Mn(L₄)(tcc)] · 1.5CH₂Cl₂ (4), [Mn(L₅)(tcc)] (5), and (HN(C₂H₅)₃)[Mn(L₆)(tcc)] · CH₂Cl₂ (6) have been synthesized using the ligands HL₁ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]phenol), HL₂ (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl] phenol), HL₃ (2-[[((6-methylpyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino]methyl]-4-nitrophenol), HL₄ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-4-bromophenol), HL₅ (2-[(bis(pyridin-2-ylmethyl)amino)methyl]-6-methoxyphenol) and H₂L₆ ([(bis(2-hydroxy-5-nitrobenzyl))(pyridin-2-ylmethyl)]amine) and characterized by X-ray crystallography, mass spectrometry, IR, UV-Vis spectroscopy, cyclic voltammetry, and elemental analysis. Compounds 1 and 6 crystallize in the monoclinic space groups P2₁/n and P2₁/c, respectively, whereas the crystal structures of complexes 2, 3, and 4 were solved in the triclinic space group . Complex 5 crystallizes in the orthorhombic space group P2₁2₁2₁. Complexes 1-6 are structural related to the proposed active site of intradiol cleaving catechol dioxygenase exhibiting a distorted octahedral N₃O₃ (1-5) and N₂O₄ (6) donor set, respectively. Complexes 1-6 can be regarded as structural manganese analogous for substituted forms of iron-containing intradiol cleaving catechol dioxygenases, where the substrate tetrachlorocatechol (tcc) is asymmetrically bound to the metal center.     

Functional model for catecholase-like activity: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted-salicylaldimine ligands

Four new mononuclear iron(III) complexes with the substituted-salicylaldimine ligands, [Fe(L¹)(TCC)] (1), [Fe(L²)(TBC)] (2), [Fe(L³)(TBC)] (3) and [Fe(L⁴)(TCC)](CH₃CN) (4) (HL¹ = N′-(5-OH-salicylaldimine)-diethylenetriamine, HL² = (N′-(5-Cl-salicylaldimine)-diethylenetriamine, HL³ N′-(5-Br-salicyl-aldimine)-dipropylenetriamine, HL⁴ = (N′-3,5-Br-salicylaldimine)-dipropylenetriamine, H₂TCC = tetrachlorocatechol, and H₂TBC = tetrabromocatechol), were prepared and characterized by XRD, EPR, and Mössbauer spectroscopy. The coordination sphere of the Fe(III) in complexes 1-4 is a distorted octahedral with N₃O₃ donors set which constructed by the Schiff-base ligands and the catecholate substrates of TBC or TCC. The in situ prepared Fe(III) complexes [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)(Cl₂)], and [Fe(L⁴)Cl₂] in absence of TBC or TCC show a high catecholase-like activity for the oxidation of 3,5-DTBC to the corresponding quinone 3,5-DTBQ.     

Effect of metal coordination and intra-molecular H-bond on the acidity of phenolic proton in a set of structurally characterized octahedral Ni(II) complexes of l-histidine derivative

Four different mononuclear octahedral Ni(II) complexes with protonated and deprotonated form of the same ligand have been synthesized by controlling reaction conditions and structurally characterized. The complexes are [Ni(HL^l-his)(benzoate)(MeOH)] (1), [Ni(HL^l-his)(SCN)(MeOH)] (2), [Ni(HL^l-his)₂] (3) and [Ni(L^l-his)(imidazole)₂] (4) where H₂L^l-his is (S)-2-(2-hydroxybenzylamino)-3-(1H-imidazol-4-yl)-propionic acid. The ligand behaves as a monobasic tetradentate ligand in 1 and 2, monobasic tridentate ligand in 3 and dibasic tetradentate ligand in 4. Ni(II) coordinated phenolic proton of the ligand in the complexes 1-2 shows strong intra-molecular H-bonding with benzoate in 1 and lattice water in 2, whereas 3 shows intermolecular H-bonding between uncoordinated phenols with neighbouring carboxylate. The pH titration of the complexes revealed that metal coordination and H-bond in complexes 1 and 2 considerably lowers the acidity of ligand phenol (pK_a 6.8 and 7.0 respectively) compared to phenol (pK_a 10). The complex 4 does not show any proton loss due to the absence of phenolic proton. All the complexes show extensive H-bonded network in the crystals including narrow (7.8 × 5.2 Å) water filled one dimensional channel in 2.     

Substituted pyridylmethylamide ligands and their zinc complexes

Mononuclear zinc complexes of a family of pyridylmethylamide ligands abbreviated as HL, HL^Ph, HL^Me3, HL^Ph3, and MeL^SMe [HL = N-(2-pyridylmethyl)acetamide; HL^Ph = 2-phenyl-N-(2-pyridylmethyl)acetamide; HL^Me3 = 2,2-dimethyl-N-(2-pyridylmethyl)propionamide; HL^Ph3 = 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide; MeL^SMe = N-methyl-2-methylsulfanyl-N-pyridin-2-ylmethyl-acetamide] were synthesized and characterized spectroscopically and by single crystal X-ray structural analysis. The reaction of zinc(II) salts with the HL ligands yielded complexes [Zn(HL)₂(OTf)₂] (1), [Zn(HL)₂(H₂O)](ClO₄)₂ (2), [Zn(HL^Ph3)₂(H₂O)](ClO₄)₂ (3), [Zn(HL^Ph)Cl₂] (4), [Zn(HL^Me3)Cl₂] (5), and [Zn(MeL^SMe)Cl₂] (6). The complexes are either four-, five- or six-coordinate, encompassing a variety of geometries including tetrahedral, square-pyramidal, trigonal-bipyramidal, and octahedral.     

Synthesis and structural characterization of dinuclear complexes of trivalent aluminum, gallium, indium and chromium derived from pyrazole-2-ethanol

The reaction of 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL) with anhydrous metal(III) halides (M = Al, Ga, In and Cr) results in the isolation of four novel dinuclear complexes [Al(μ-L)Cl₂]₂ (1), [Ga(μ-L)Cl₂]₂ (2), [In(μ-L)Br₂(H₂O)]₂·2thf (3) and [Cr(μ-L)Cl₂(H₂O)]₂·1.5thf (4) in good yields. The new complexes have been characterized with the aid of analytical and spectroscopic studies. A single crystal X-ray structure determination in each case confirms the dimeric structure for all the complexes in the solid-state. The pyrazole ethanol ligand binds to the metal through both pyrazole nitrogen and bridging alkoxide oxygen terminals with the formation of a central M₂O₂ core involving the ethoxide anion. The metal(III) center is pentacoordinated in compounds 1 and 2, while it is hexacoordinated in compounds 3 and 4.     

3D non porous and thermally labile nickel(II) and manganese(II) complexes with hetero donor ligands: Synthesis, X-ray single crystal structure, thermal and luminescent study

Three coordination complexes of formula [Ni(L₁)₂(H₂O)₄].4H₂O (1), [Mn(L₂)₂(H₂O)₄] (2) and [Mn(L₂)₂(H₂O)₂]_n (3) [L₁H = 6-methylpyridine-3-carboxylic acid, L₂H = 3-(3-pyridyl)acrylic acid] have been synthesized and structurally characterized by X-ray single crystal analysis. A 3D network is achieved through H-bonding in 1 and 2, while crystal packing of complex 3 shows a 3D supramolecular coordination polymer. Thermal properties have been investigated by thermogravimetric analysis. Luminescence study features the presence of LMCT and metal purterbed ligand centered emission bands.     

Functional model for intradiol-cleaving catechol 1,2-dioxygenase: Synthesis, structure, spectra, and catalytic activity of iron(III) complexes with substituted salicylaldimine ligands

A series of mononuclear iron(III) complexes with containing phenolate donor of substituted-salicylaldimine based ligands [Fe(L¹)(TCC)] · CH₃OH (1), [Fe(L²)(TCC)] · CH₃OH (2), [Fe(L³)(TCC)] (3), and [Fe(L⁴)(TCC)] (4) have been prepared and studied as functional models for catechol dioxygenases (H₂TCC = tetrachlorocatechol, or HL¹ = N′-(salicylaldimine)-N,N-diethyldiethylenetriamine, HL² = N′-(5-Br-salicylaldimine)-N,N-diethyldiethylenetriamine, HL³ = N′-(4,6-dimethoxy-salycyl-aldimine)-N,N-diethyl-diethylenetriamine, HL⁴ = N′-(4-methoxy-salicylaldimine)-N,N-diethyl-diethylenetriamine). They are structural models for inhibitors of enzyme-substrate adducts from the reactions of catechol 1,2-dioxygenases. Complexes 1-4 were characterized by spectroscopic methods and X-ray crystal structural analysis. The coordination sphere of Fe(III) atom of 1-4 is distorted octahedral with N₃O₃ donor set from the ligand and the substrate TCC occupying cis position, and Fe(III) is in high-spin (S = 5/2) electronic ground state. The in situ prepared iron(III) complexes without TCC, [Fe(L¹)Cl₂], [Fe(L²)Cl₂], [Fe(L³)Cl₂], and [Fe(L⁴)Cl₂] are reactive towards intradiol cleavage of the 3,5-di-tert-butylcatechol (H₂DBC) in the presence of O₂ or air. The reaction rate of catechol 1,2-dioxygenase depends on the redox potential and acidity of iron(III) ions in complexes as well as the substituent effect of the ligands. We have identified the reaction products and proposed the mechanism of the reactions of these iron(III) complexes with H₂DBC with O₂.     

Molecular structures and redox properties of oxorhenium(V) ‘3+1’ mixed ligand complexes with heterocyclic thiolates containing nitrogen

Reactions of chloro(3-thiapentane-1,5-dithiolato)oxorhenium(V) [ReO(SSS)Cl] with N-methyl-1H-imidazole-2-thiol (HL¹) and 2-pyrimidinethiol (HL²) have been studied to form ‘3+1’ oxorhenium(V) complexes. In the absence of triethylamine, [Re(SSS)(HL¹)]Cl (1a) was formed, while in the presence of triethylamine [Re(SSS)L¹] (1b) and [Re(SSS)L²] (2) were produced. Molecular structures of complexes 1a and 2 were determined to be distorted square pyramidal by single crystal X-ray analytical method. From cyclic voltammetric studies, furthermore, it was proposed that complexes 1b and 2 are irreversibly oxidized to Re(VI) at around 0.84 and 1.01 V versus Ag/AgNO₃, respectively, and are reduced to Re(IV) at −1.55 and −1.51 V with the dissociation of L¹ or L², followed by the quasi-reversible reductions to Re(III) at around −1.69 V, respectively.     

Copper(II) complexes with monocarboxylate ligands bearing different substituent groups: Synthesis and spectroscopic studies

In our continuing efforts to explore the effects of substituent groups of ligands in the formation of supramolecular coordination structures, seven new Cu^II complexes formulated as [Cu₂(L¹)₄(DMF)₂] (1), {[Cu₂(L¹)₄(Hmta)](H₂O)_0.75}_∞ (2), [Cu₂(L²)₄(2,2′-bipy)₂] (3), [Cu₂(L³)₄(H₂O)₂] (4), [Cu₂(L³)₄(Hmta)]_∞ (5), [Cu₂(L³)₄(Dabco)]_∞ (6) and [Cu₂(L³)₄(Pz)]_∞ (7) with three monocarboxylate ligands bearing different substituent groups HL¹-HL³ (HL¹ = phenanthrene-9-carboxylic acid, HL² = 2-phenylquinoline-4-carboxylic acid, HL³ = adamantane-1-carboxylic acid, Hmta = hexamethylenetetramine, 2,2′-bipy = 2,2′-bipyridine, Dabco = 1,4-diazabicyclo[2.2.2] octane and Pz = pyrazine), have been prepared and characterized by X-ray diffraction. In 1, 2 and 4-7, each Cu^II ion is octahedrally coordinated, and carboxylate acid acts as a syn-syn bridging bidentate ligand. While each Cu^II ion in 3 is penta-coordinated in a distorted square-pyramidal geometry. 1 and 4 both show a dinuclear paddle-wheel block, while 2, 5, 6 and 7 all exhibit an alternated 1D chain structure between dinuclear paddle-wheel units of the tetracarboxylate type Cu₂-(RCO₂)₄ and the bridging auxiliary ligands Hmta, Dabco and Pz. Furthermore, 3 has a carboxylic unidentate and μ_1,1-oxo bridging dinuclear structure with the chelating auxiliary ligand 2,2′-bipy. Moreover, complexes 1-6 were characterized by electron paramagnetic resonance (EPR) spectroscopy.     

Supramolecular architectures based on di-, tri- and tetrameric complexes with N,N′-diacylhydrazide ligands

Five new complexes, [Co₃(HL₁)₂(Py)₈]·4CH₃OH (1), [Ni₃(HL₁)₂(Py)₄]₂·2DMF (2), [Co₃(H₂L₂)₂(Py)₈]·2NO₃ (3), [Ni₂(HL₂)(Py)₆] (4) and [Cu₄(HL₂)₂(Py)₄]·4DMF (5) (H₄L₁ = N-propionyl-4-hydroxysalicylhydrazide, H₄4-hopshz; H₅L₂ = N-(3-carboxy-cis-2-propenoyl)-4-hydroxysalicylhydrazide, H₅4-hocpshz) have been obtained from two N,N′-diacylhydrazide ligands and characterized by elemental analysis, FT-IR, X-ray diffraction and antimicrobial activities. These di-, tri-, and tetrameric complexes are connected into three-dimensional supramolecular architectures with interesting topologies through O-H?O, C-H?O and C-H?π interactions. 1-3 are linear trimeric complexes with the ligands triply-deprotonated. Topological analysis indicates that they exhibit 2D (4,4), 3D (6,8)-connected (3³4⁹5²6)(3⁴4¹²5⁷6⁴7) and 8-connected (4²⁵6³) net, respectively. 4 and 5 possess dimeric and tetrameric structures, which are extended into 7-connected (3³4¹³5³6) and 4-connected (4,4) net, respectively.     

Coordination chemistry of heterocycle-functionalized diazamesocycles: tuning the productive Ni complexes through altering the pendants of ligands

In order to further understand the coordination chemistry of diazamesocyclic systems, a series of mononuclear Ni^II complexes with 1,4-diazacycloheptane (DACH) functionalized by additional imidazole or pyridine donor pendants, including [NiL¹](ClO₄)₂ · H₂O (1), [NiL¹Cl](ClO₄) (2), [NiL²Cl](ClO₄) · CH₃OH (3), [NiL²Cl][NiL²](ClO₄)₃ (4) and [NiL³](ClO₄)₂ (5), where L¹ = 1,4-bis(N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane, L² = 1,4-bis(pyridyl-2-yl-methyl)-1,4-diazacycloheptane, and L³ = 1,4-bis-(imidazol-4-yl-methyl)-1,4-diazacycloheptane, have been prepared and characterized. A detailed study on the solid structures and solution spectra of these complexes indicates that tetradentate ligands L¹, L² and L³ would lead to new Ni^II complexes with different coordination environments in the solid states and solution. The N-methyl substituted imidazole functionalized ligand L¹ forms green compound 2 and yellow product 1; while the pyridine functionalized ligand L² affords red product 4 and green complex 3; the ligand L³ results in only one stable mononuclear Ni^II product 5. The solution behaviors of these interesting compounds were also investigated by UV-Vis technique.