Synthesis,structural characterization and solvent effect of copper(II) complexes with a variational multidentate Salen-type ligand with bisoxime groups

Four new solvent-induced Cu(II) complexes with the chemical formulae [{Cu(HL)(CH₃OH)}₂Cu] · CH₃OH (1), [{(Cu(HL))₂(CH₃CH₂OH)₂}Cu] (2), [{CuL(H₂O)}₂Cu₂] · 2CH₃CH₂CH₂OH (3) and [{(Cu(HL))₂(CH₃CH₂CH₂CH₂OH)₂}Cu] (4), where H₄L = 6,6′-dihydroxy-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol, have been synthesized and characterized by elemental analyses, ¹H NMR, FT-IR, UV–Vis spectra, TG-DTA, molar conductances and X-ray crystallography. Complexes 1, 2 and 4 have an elongated square-pyramidal geometry with an unusually long bond from the penta-coordinated Cu(II) centres to the oxygen atoms of the apically coordinated solvent (methanol, ethanol or n-butanol) molecules for the terminal Cu(II) ions, and a square planar geometry distorted tetrahedrally for the central Cu(II) ion. In complex 3, the terminal Cu(II) ions have trigonal bipyramidal coordination geometries constituted by equatorial O₂N donor sites, with one oxygen atom from one of the coordinated water molecules and one nitrogen atom from a completely deprotonated L⁴⁻ ligand unit in the axial positions, and the central Cu(II) ions are in slightly tetrahedrally distorted square planar geometries constituted by four phenoxo oxygen donors from two completely deprotonated L⁴⁻ ligand units, and these form a tetrametal Cu–O–Cu–O–Cu–O–Cu–O eight-membered ring. These four complexes exhibit strong hydrogen bonding interactions in the solid state. Moreover, co-crystallizing n-propanol molecules link two other adjacent complex molecules into a self-assembled infinite 2D supramolecular structure via the intermolecular hydrogen bonds in complex 3.     

Syntheses,structures and luminescent properties of four d-metal coordination polymers based on the 2,4,5-tri(4-pyridyl)-imidazole ligand

Four d¹⁰-metal coordination polymers based on the 2,4,5-tri(4-pyridyl)-imidazole ligand (Htpim), {[Zn₂(Htpim)₄Cl₄] · 8H₂O}_n (1), {[Cd(tpim)₂(H₂O)₂] · 4CH₃OH}_n (2), {[Cu₂(Htpim)(PPh₃)₂I₂] · CH₃CN}_n (3) and {[Ag(Htpim)](NO₃) · CH₂Cl₂}_n (4), have been synthesized and characterized by elemental analyses, IR, thermogravimetric and X-ray structural analyses. Both complexes 1 and 2 show one dimensional ribbon-like structures. Via intermolecular hydrogen bonds, a 2D supramolecular network and 3D framework are formed for 1 and 2, respectively. Complex 3 shows a 1D zigzag chain with a CuI₂Cu rhomboid dimer. Complex 4 shows a 1D ladder-like polymer with two different metallacycles. The luminescent properties of all the complexes have been studied in the solid state.     

Syntheses and structures of Ag(I) complexes containing 1,4-bis(4,5-dihydro-2-oxazolyl)benzene

The reactions of the polydentate ligand 1,4-bis(4,5-dihydro-2-oxazolyl)benzene (L) with AgX (X = CH₃COO⁻, ClO₄⁻ and CF₃SO₃⁻) afforded the complexes [Ag₂(L)(CH₃COO)₂]_∞ (1), [Ag₂(L)₃(ClO₄)₂]_∞ (2), and [Ag(L)(CF₃SO₃)]_∞ (3), whereas the reaction of L with Ag₂SO₄ in MeOH/H₂O system afforded {[Ag₂(L)₃(H₂O)₃][SO₄] · 9H₂O}_∞ (4). The EA and IR have been recorded and all the complexes have been structurally characterized by X-ray crystallography, confirming that complexes 1–4 are two-dimensional coordination polymeric frameworks. The bidentate L ligands in complexes 3 and 4 adopt both the syn and anti conformation and those in 1 and 2 adopt the anti conformation only. The anions CH₃CO₂⁻ in complex 1 bridge the Ag(I) atoms in η¹, η², μ₃-coordination mode forming a 1-D zig-zag –[Ag(CH₃COO)]_n– chains, while the anions ClO₄⁻, CF₃SO₃⁻ and SO₄²⁻ in complexes 2–4 are not coordinated to the Ag(I) atoms, but all of them play an important roles in linking cationic 2-D frameworks into 3-D supramolecular structures.     

Subtle role of counteranions in molecular construction: Structures and properties of novel Cu(II) coordination complexes with bis-(1-benzoimidazolymethylene)-(2,5-thiadiazoly)-disulfide

The direct self-assembly of bis-(1-benzoimidazolymethylene)-(2,5-thiadiazoly)-disulfide (L) with CuSO₄, Cu(NO₃)₂ and CuCl₂ affords three novel supramolecular complexes: 1-D ladder-like chain complex {[Cu(SO₄)(L)] · (CH₃OH)}_n (1), dimer complexes {[Cu(L)(CH₃O)]₂(NO₃)₂} · 2H₂O (2) and [Cu(L)(Cl)(N₃)]₂ · 2CH₃OH (3). The nature of the anions is the underlying reason behind the differences in the structures of this series of complexes. Furthermore, utilizing the coordinatively unsaturated complexes 2 and 3 as precursor complexes, two new derivative complexes [Cu(L)(NCS)(CH₃O)]₂ · 2CH₃OH (2A) and [Cu(L)(ClO₄)(N₃)]₂ · 2CH₃OH (3A) are obtained by the addition and exchange reactions of complexes 2 and 3 with anions. X-ray crystallographic analysis shows that the two derivatives retain the skeletons of their precursor complexes, and the anions with the stronger coordination capacity only bind to the active position of precursor complexes. In addition, different from the obvious effects on the structures in the direct self-assembly of the metal and ligand, the change of counteranions has no great impact on the structures in the anion exchange reactions. We also study the catalytic activities of the complexes 2, 2A, 3, and 3A, which have similar skeletons, for the oxidative coupling polymerization of 2,6-dimethylphenol (DMP). And we find that the introductions of different coordination counterions produce significant impacts on the catalytic properties of these complexes.     

Salen-type nickel(II), palladium(II) and copper(II) complexes having chiral and racemic camphoric diamine components

Chiral and racemic Salen-type Schiff-base ligands (H₂L¹, H₂L² and H₂L³), condensed between D-(+)- and D,L-camphoric diamine (also known as (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diamine) and 2-hydroxybenzaldehyde or 3,5-dibromo-2-hydroxybenzaldehyde with a 1:2 molar ratio, have been synthesized and characterized. A series of new nickel(II), palladium(II) and copper(II) complexes of these chiral and racemic ligands exhibiting different coordination number (4, 5 and 6) have been characterized with the formulae [NiL¹]·CH₃OH (3), [NiL¹]·H₂O (4), [NiL²] (5), [PdL²] (6), [Cu₂(L²)₂(H₂O)] (7) and [NiL³(DMF)(H₂O)] (8). Different solvent molecules in 3 and 4 (methanol and water molecules) as well as different apical ligands in 7 and 8 (water and DMF molecules) are involved in different O–H···O hydrogen bonding interactions to further stabilize the structures. UV–Vis (UV–Vis), circular dichroism (CD) spectra and thermogravimetric (TG) analyses for the metal complexes have also been carried out.     

Piperazinediium,Zr(IV) and Ce(IV) pyridine-2,6-dicarboxylates: Syntheses,characterizations, crystal structures, ab initio HF,DFT calculations and solution studies

The novel title compounds, (pipzH₂)_1.5(pydcH)₃·3.7H₂O, 1, (pipzH₂)[Zr(pydc)₃]·8H₂O, 2 and (pipzH₂)[Ce(pydc)₃]·8H₂O, 3 in which pydcH₂ is pyridine-2,6-dicarboxylic acid and pipz is piperazine were obtained in aqueous solution. The compounds were characterized by IR, ¹H NMR and ¹³C NMR spectroscopy, elemental analyses, and X-ray crystallography. Compound 1 is resulted from proton transfer between pydcH₂ and pipz. However, compounds 2 and 3 are resulted from complexation of 1 and corresponding metallic salts. Both compounds 2 and 3 contain three pyridine-2,6-dicarboxylate species as tridentate ligands, one piperazinediium as counter ion, and eight-uncoordinated water molecules in the asymmetric unit. In both structures each M(IV) is coordinated in a distorted tricapped trigonal prism geometry by three nitrogen and six oxygen atoms of carboxylate groups of three (pydc)²⁻ fragments. In the crystal structures of 1, 2 and 3, extensive O–H···O, N–H···O and C–H···O hydrogen bonds as well as electrostatic forces, C–H···π, C–O···π and π–π stacking play important roles in stabilizing structures. The geometrical parameters of the [M(pydc)₃]²⁻ anionic complexes, where M = Ce(IV), Zr(IV) have been optimized with the B3LYP method of density functional theory (DFT) and ab initio Hartree–Fock (HF) methods for comparison. In addition, we have studied the structures of (pydc)²⁻ anion and its mono and doubly protonated forms, (pydcH)⁻ and pydcH₂. The electronic properties of the anionic complexes and ligands have been investigated based on the natural bond orbital (NBO) analysis at the B3LYP method which verifies that the synergistic effect has been occurred in the title complexes. In solution study of 2, the stoichiometry and stability constant of complexation of pipz, pydc, pydc–pipz proton transfer system and Zr(IV) ion in aqueous solution were investigated by potentiometric method.     

Synthesis,structure and spectroelectrochemical property of (2,2′-bipyridine)–metal (M = Pt,Pd) dichloride with 4,4′-bis(fluorous-ponytail) on bipyridine

The 4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy ligands [R_f = n-C₃F₇ (1a), HCF₂(CF₂)₃ (1b)] were prepared and then treated with [MCl₂(CH₃CN)₂] (M = Pt or Pd) to result in the corresponding metal complexes, [MCl₂(4,4′-bis(R_fCH₂OCH₂)-2,2′-bpy)] (M = Pt 2a–b; Pd 3a–b). Both ligands and metal complexes were fully characterized by multi-nuclei NMR (¹H, ¹⁹F and ¹³C), FTIR, and mass (GC/MS or HR-FAB) methods. The X-ray structures of 2a–b and 3a–b were studied. With terminal CF₃, the structures of 2a and 3a exhibit disordered polyfluorinated regions in solid state. With terminal HCF₂, the structures of 2b and 3b show a π–π stacking of the bpy planes, five-membered C–H···O hydrogen bond and an unusual intramolecular blue-shifting C–H···F–C hydrogen bond system, whereas without terminal HCF₂, the structures of 2a and 3a show the similar π–π stacking, five-membered C–H···O hydrogen bond and typical orientation of polyfluorinated ponytails, but not the C–H···F–C hydrogen bond system. The CV and UV/Vis studies were also carried out.     

Interaction of copper(II) and palladium(II) with linked 2,2′-dipyridylamine derivatives: Synthetic and structural studies

Interaction of copper(II) salts with 2,2′-dipyridylamine (1), N-cyclohexylmethyl-2,2′-dipyridylamine (2), di-2-pyridylaminomethylbenzene (3), 1,2-bis(di-2-pyridylaminomethyl)-benzene (4), 1,3-bis(di-2-pyridylaminomethyl)benzene (5), 1,4-bis(di-2-pyridylaminomethyl)benzene (6), 1,3,5-tris(di-2-pyridylaminomethyl)benzene (7) and 1,2,4,5-tetrakis(di-2-pyridylaminomethyl)benzene (8) has yielded the following complexes: [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · H₂O, [Cu₂(4)(NO₃)₄], [Cu₂(5)(NO₃)₄] · 2CH₃OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Cu₄(8)](NO₃)₄] · 4H₂O while complexation of palladium(II) with 1, 4, 5 and 6 gave [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)Cl₄], [Pd₂(4)(OAc)₄], [Pd₂(5)Cl₄], [Pd₂(6)Cl₄] and [Pd₂(6)(OAc)₄] · CH₂Cl₂, respectively. X-ray structures of [Cu(2)(μ-Cl)Cl]₂, [Cu(3)(μ-Cl)Cl]₂ · 2C₂H₅OH, [Cu₂(6)(CH₃OH)₂(NO₃)₄], [Pd(1)₂](PF₆)₂ · 2CH₃OH, [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂ are reported. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a diverse range of coordination geometries and lattice arrangements, with the structures of [Pd₂(4)(OAc)₄] · 4H₂O and [Pd₂(6)(OAc)₄] · 2CH₂Cl₂, incorporating the isomeric ligands 4 and 6, showing some common features. Liquid–liquid (H₂O/CHCl₃) extraction experiments involving copper(II) and 1–3, 5, 7and 8 show that the degree of extraction depends markedly on the number of dpa-subunits (and concomitant lipophilicity) of the ligand employed with the tetrakis-dpa derivative 8 acting as the most efficient extractant of the six ligand systems investigated.     

Syntheses, crystal structures of a series of copper(II) complexes and their catalytic activities in the green oxidative coupling of 2,6-dimethylphenol

Three mixed-ligand Cu^II complexes bearing iminodiacetato (ida) and N-heterocyclic ligands, namely, [Cu₂(ida)₂(bbbm)(H₂O)₂] · H₂O (1), [Cu₂(ida)₂(btx)(H₂O)₂] · 2H₂O (2) and [Cu₂(ida)₂(pbbm)(H₂O)₂] · H₂O · 3CH₃OH (3) (bbbm = 1,1^′-(1,4-butanediyl)bis-1H-benzimidazole, btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, pbbm = 1,1^′-(1,3-propanediyl)bis-1H-benzimidazole), in addition to three fcz-based Cu^II complexes, namely, {[Cu(fcz)₂(H₂O)₂] · 2NO₃}_n (4), {[Cu(fcz)₂(H₂O)] · SO₄ · DMF · 2CH₃OH · 2H₂O}_n (5) and {[Cu(fcz)₂Cl₂] · 2CH₃OH}_n (6) (fcz = 1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-l-yl) methyl]ethanol) have been prepared according to appropriate synthetic strategies with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that 1 and 2 possess similar binuclear structures, 3 features a 2D pleated network, and 4 exhibits a 1D polymeric double-chain structure. Complexes 1-6 are tested as catalysts in the green catalysis process of the oxidative coupling of 2,6-dimethylphenol (DMP). Under the optimized reaction conditions, these complexes are catalytically active by showing high conversion of DMP and high selectivity of PPE. The preliminary study of the catalytic-structural correlations suggests that the coordination environment of the copper center have important influences on their catalytic activities.     

New metal–organic architectures of cobalt(II), nickel(II) and zinc(II) with tripodal ligand 5-(1H-imidazol-4-ylmethyl)aminoisophthalic acid

Four new coordination polymers {[Ni(HL)(H₂O)]·H₂O}_n (1), {[Co(HL)(H₂O)]·H₂O}_n (2), {[Co(HL)]·4H₂O}_n (3) and {[Zn(HL)]·2H₂O·0.5C₂H₅OH}_n (4) [H₃L = 5-(1H-imidazol-4-ylmethyl)aminoisophthalic acid] have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction analyses. Complexes 1 and 2 display (3, 3)-connected 2D network with (4, 8²) topology. While 3 and 4 exhibit a binodal (3, 6)-connected 2D network with a Schläfli symbol (4³)₂(4⁶, 6⁶, 8³). The complexes 1–4 show remarkable thermal stability and 4 exhibits blue fluorescence with maximum emission at 413 nm upon excitation at 362 nm in the solid state at room temperature. In addition, the magnetic measurements of 3 indicate that there are antiferromagnetic interactions between the neighboring Co(II) centers.     

Syntheses, structures, and electrochemical properties of four complexes based on 4-ferrocenylbutyrate ligand

Four ferrocenyl complexes with the formulas {[Mn(η²-OOC(CH₂)₃Fc)₂(bbbm)]·CH₃OH}_n (1), {[Co(OOC(CH₂)₃Fc)(η²-OOC(CH₂)₃Fc)(bbbm)]·CH₃OH}_n (2), {[Ni(OOC(CH₂)₃Fc)₂(bbbm)(CH₃OH)₂]·2CH₃OH}_n (3) and [Pb₆(μ₂-OOC(CH₂)₃Fc)₂(μ₃-OOC(CH₂)₃Fc)₂(μ₂-η²-OOC(CH₂)₃Fc)₂(η²-OOC(CH₂)₃Fc)₂(μ₄-O)₂] (4) (Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄), bbbm = 1,1-(1,4-butanediyl)bis-1H-benzimidazole) have been synthesized and characterized by single crystal X-ray diffraction. Owing to the different conformations of the bbbm units in complexes 1 (or 2) and 3, complexes 1 and 2 possess 1D helical chain structure with 2₁ screw axes along the b-direction, while complex 3 shows a 1D linear chain structure with ferrocenylbutyrate groups hanging on the chain. Complex 4 is a hexanuclear complex and exhibits a nano-scale wheel-like framework with six Pb(II) ions as a core and eight 4-ferrocenylbutyrate ligands as branches. The cyclic voltammetric studies show that the formal potentials of the four complexes are close to the free ferrocenylbutyrate ligand, which indicates that the coordination of the metal ions to the ferrocenyl ligand does not have significant effects on the redox potential of the ferrocenylbutyrate ligand. Further investigations suggest that the redox processes of the ferrocenylbutyrate ligand and complexes 1-4 are all chemically quasi-reversible processes and controlled by diffusion.     

Structural effect of the competition of 4-picoline and water molecules to form complexes with Be,Mg and Zn phthalocyanines

The BePc(4-Mepy), MgPc(4-Mepy)₂ were recrystallised from wet 4-picoline and the aqua M((II) phthalocyaninato complexes, BePcH₂O · (4-Mepy) (Ia), (MgPcH₂O · (4-Mepy))₂ (IIa) and (MgPcH₂O · (4-Mepy)₂) · (4-Mepy) (IIb), have been obtained. Recrystallisation of ZnPc(4-Mepy) in wet 4-picoline yields the β-ZnPc in microcrystalline form. The Ia, IIa and IIb complexes were obtained in crystalline form. The composition of the Mg complexes (IIa and IIb) depends on the crystallisation temperature. The BePcH₂O · (4-Mepy) compound crystallises in the centrosymmetric space group of the triclinic system, while both Mg complexes crystallise in the P2₁/n space group of the monoclinic system. In all crystals the central M(II) atom (Be and Mg) is 4 + 1 coordinated, equatorially by four N-isoindole atoms of Pc macrocycle and axially by O atom of water molecule. Interaction of the central M atom of MgPc with axially ligated water molecule leads to the saucer-shape of the Pc ring and deviates the central M(II) atom from the N₄-isondole plane by 0.308(2), 0.482(2) and 0.537(2) Å in Ia, IIa and IIb, respectively. The molecules in the Ia and IIa crystals are linked together by a pair of O–H?N hydrogen bonds between the H atom of water molecule and the azamethine N atom of the other Pc into a dimeric structure, and the 4-picoline molecules are linked to the (MPcH₂O)₂ dimeric structure. In IIb crystal the MgPcH₂O molecule is linked by O–H?N hydrogen bonds with two 4-picoline molecules, while the third 4-picoline molecule interacts only by the van der Waals forces. The O–H?N hydrogen bonding system and the π–π interactions between the aromatic Pc macrocyles are the key for the molecular arrangement and stabilisation of the structure. The stability of the solid-state complexes was analysed by thermogravimetric measurements. Only the solid-state spectrum of IIa complex exhibits an intense near IR absorption band. The spectra of IIa and IIb in solution are identical, the Q band is blue shifted in O-donor solvents comparing with the spectrum in N-donor solvents.     

Three new mono–di–trinuclear cobalt complexes of selectively and non-selectively condensed Schiff bases with N2O and N2O2 donor sets: Syntheses,structural variations,EPR and DNA binding studies

Three new mono–di–trinuclear cobalt complexes of three different Schiff bases have been synthesised. In all the three complexes psuedohalides (NCO⁻ and N₃⁻) have been incorporated to generate structural variation. Of the three Schiff bases, HL¹ and HL² were obtained by selective condensation of two different 1,3-diamines with 2-hydroxyacetophenone and H₂L³ resulted from non-selective condensation of 1,3-diamine with 2-hydroxyacetophenone. Only one –NH₂ functionality of 1,3-diaminopropane and 1,3-diaminopentane was selectively condensed with 2-hydroxyacetophenone to generate Schiff bases HL¹ and HL², respectively. H₂L³ was obtained by condensing both the amine functionality of 1,3-diaminopropane with 2-hydroxyacetophenone. Therefore HL¹ and HL² behave as a N₂O donors, whereas H₂L³ provides a N₂O₂ donor coordination environment for the cobalt ions in the respective complexes. In [Co(L¹)₂]₂ [Co(NCO)₄] (1) the asymmetric unit comprises of five mononuclear cobalt centers, [Co₂(μ–N₃)₂(L²)₂(N₃)₂] (2) is a dinuclear and [(H₂O)₂Co(μ–N₃)₂(μ–L³)₂Co₂(N₃)_1.25(CH₃O)_0.75] · H₂O (3) is a trinuclear cobalt species. The three complexes have been characterised using IR, UV–Vis spectroscopy and cyclic voltammetry. Structural aspects of 1, 2 and 3 have been described by performing single crystal X-ray analysis. EPR analyses of 1 and 3, and DNA binding abilities of all three cobalt complexes have been studied in detail.     

Syntheses,supramolecular structures and properties of six coordination complexes based on 5-sulfosalicylic acid and bipyridyl-like chelates

Six new complexes constructed by 5-sulfosalicylic acid and bipyridyl-like ligands (2,2′-bipy and 1,10-phen), namely [Cu₄(OH)₂(ssal)₂(phen)₄ · 7H₂O] (1), [Cu₄(OH)₂(ssal)₂(bipy)₄ · 2H₂O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)₂(phen)₂] (4), [Cr(ssal)(bipy)(H₂O)₂ · 2H₂O] (5) and [Cr(ssal)(phen)₂] (6) (H₃ssal = 5-sulfosalicylic acid, H₂L = p-hydroxybenzenesulfonic acid, bipy = 2,2′-bipy, phen = 1,10-phen) were prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are both tetranuclear copper complexes with a stepped topology. In complex 3, a new coordination mode of the Hssal²⁻ group is reported in this work. During the synthetic process of complex 4, in situ decarboxylation of 5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid is involved. Two chromium 5-sulfosalicylates (5 and 6) are reported for the first time. These new complexes display different supramolecular structures by O–H?O, C–H?O hydrogen bonds as well as π?π, C–H?π and O?π interactions. The results of magnetic determination show that ferromagnetic interactions exist in complex 1, however, antiferromagnetic interactions exist in 2.     

Synthesis and characterization of water-soluble palladium(II)-functionalized diphosphine complexes

Water-soluble functionalized bis(phosphine) ligands L (a–h) of the general formula CH₂(CH₂PR₂)₂, where for a: R = (CH₂)₆OH; b–g: R = (CH₂)_nP(O)(OEt)₂, n = 2–6 and n = 8; h: R = (CH₂)₃NH₂ ( Scheme 1), have been prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H₂P(CH₂)₃PH₂. Water-soluble palladium complexes cis-[Pd(L)(OAc)₂] (1–8) were obtained by the reaction of Pd(OAc)₂ with the ligands a–h in a 1:1 mixture of dichloromethane:acetonitrile. The water-soluble phosphine ligands and their palladium complexes were characterized by IR, ¹H and ³¹P NMR. A crystallographic study of complex 1 shows that the Pd(II) ion has a square planar coordination sphere in which the acetate ligands and the diphosphine ligand deviate by less than 0.12 Å from ideal planar.     

Structural diversity in Cu(II), Cd(II) and Hg(II) coordination complexes with the rigid N,N′-bis(2/3-aryl)-1,4-benzenedicarboxamide ligand

The syntheses and structures of a series of metal complexes, namely Cu₂Cl₄(L¹)(DMSO)₂·2DMSO (L¹ = N,N′-bis(2-pyridinyl)-1,4-benzenedicarboxamide), 1; {[Cu(L²)_1.5(DMF)₂][ClO₄]₂·3DMF}_∞ (L² = N,N′-bis(3-pyridinyl)-1,4-benzenedicarboxamide), 2; {[Cd(NO₃)₂(L³)]·2DMF}_∞ (L³ = N,N′-bis-(2-pyrimidinyl)-1,4-benzenedicarboxamide), 3; {[HgBr₂(L³)]·H₂O}_∞, 4, and {[Na(L³)₂][Hg₂X₅]·2DMF}_∞ (X = Br, 5; I, 6) are reported. All the complexes have been characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Complex 1 is dinuclear and the molecules are interlinked through S?S interactions. In 2, the Cu(II) ions are linked through the L² ligands to form 1-D ladder-like chains with 60-membered metallocycles, whereas complexes 3 and 4 form 1-D zigzag chains. In complexes 5 and 6, the Na(I) ions are linked by the L³ ligands to form 2-D layer structures in which the [Hg₂X₅]⁻ anions are in the cavities. The L² ligand acts only as a bridging ligand, while L¹ and L³ show both chelating and bridging bonding modes. The L¹ ligand in 1 adopts a trans-anti conformation and the L² ligand in 2 adopts both the cis-syn and trans-anti conformations, whereas the L³ ligands in 3–6 adopt the trans conformation.     

Syntheses, structures and photoelectronic properties of a series of tri- and tetra-nuclear metal complexes based on a 36-membered tetraphenol macrocyclic ligand

In this article, tetranuclear Zn^II coordination complexes [Zn₄L(μ₂-OH)₂]·2(NO₃)·6(CH₃OH)·H₂O (1) and [Zn₄L(μ₂-OH)₂(H₂O)₂]·(p-bdc)·2(CH₃OH)·3H₂O (2), dinuclear Zn^II complex [Zn₄L(NH₂-bdc)₂]·2(CH₃OH)·3H₂O (3), and trinuclear Cd^II complexes [Cd₃L(m-bdc)]·6.5H₂O (4) and [Cd₃L(NH₂-bdc)]·5.5H₂O (5), based on a tetraphenol 36-membered macrocycle (L) having four ethylenediamine and four 2,6-diformyl-4-methylphenol functionalities, have been synthesized at room temperature (p-bdc = 1,4-benzenedicarboxylate, NH₂-bdc = 5-aminoisophthalate and m-bdc = 1,3-benzenedicarboxylate). In 1 and 2, four Zn^II centers are bridged by phenoxide and hydroxy atoms of the L ligands to form tetranuclear Zn^II complexes. The inorganic and organic anions in 1 and 2 do not coordinate to Zn^II centers, but act as counter anions. In 3, two Zn^II centers are bridged by two phenoxide O atoms to form a Zn^II cluster (Zn₂O₂N₄). Moreover, two (Zn₂O₂N₄) clusters within the ring of the L ligand are further bridged by two NH₂-bdc anions in a monodentate fashion. Compound 4 possesses the trinuclear Cd^II clusters (Cd₃N₈O₈), which has a similar structure to compound 5. The trinuclear Cd^II clusters are bridged by the dicarboxylate anions to yield an infinite coordination polymers chain. The photoelectric transfer properties of complexes 1, 2 and 4 were investigated by surface photovoltage spectroscopy (SPS) and the field-induced surface photovoltage spectra (FISPS) techniques. The results reveal that the complexes exhibit positive surface photovoltage (SPV) responses in the range of 300-600 nm, possessing the p-type semiconductor characteristics. So far, the surface photovoltage properties of the macrocycle complexes based on tetraphenol macrocyclic ligands were investigated for the first time. Moreover, elemental analyses, IR spectra, and luminescent properties of these compounds were also studied.     

Synthesis and characterization of two new coordination supramolecular structures from a versatile unsymmetric 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) ligand

Two new inorganic–organic coordination networks based on a versatile and unsymmetric building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and inorganic Co^II and Cd^II salts have been synthesized in mixed solvent media and structurally characterized by single-crystal X-ray diffraction analysis. Crystal Hpot (1) was obtained from methanol solution. Reaction of Co(NO₃)₂ · 6H₂O with Hpot afforded a neutral two-dimensional (2-D) porous coordination polymer {[Co(pot)₂] · 6H₂O}_n (2) with a (4,4) network, which shows a 3-D supramolecular network through O–H?O weak interactions. While substituting the transition metal ions used in 2 with Cd(NO₃)₂ · 6H₂O, a neutral 2-D coordination polymer [Cd₂(pot)₄]_n (3) with a (6,3) network which further extended to a 3-D supramolecular structure through versatile hydrogen bonds C–H?X (X = O, N and S) was obtained. It is remarkable that the building block “pot” anion exhibits versatile coordination modes in complexes 2 and 3. These results indicate that the versatile nature of this rigid unsymmetric ligand, together with the coordination preferences of the metal centers, plays a critical role in construction of novel coordination polymers. The properties of gas absorption, magnetism and luminescence of 2 and 3 have been investigated and discussed in detail.     

Mono and dinuclear Re(V) complexes with a hydrospirophosphorane HP∼O derived ligand: Synthesis,structural analysis and molecular dynamics

Two neutral mono and dinuclear rhenium(V) complexes, cis-ReOCl₂(P∼O)(pym) (1) and cis-[ReOCl₂(P∼O)]₂(μ–pym) (2 · (CH₃)₂CO), with the hydrospirophosphorane ligand HP∼O (HP∼O = octamethyl-2,2,3,3,7,7,8,8-tetraoxa-5λ⁵ 1,4,6,9-phosphaspiro-4,4-nonane) have been prepared. The coordination geometry of the complexes has been determined in solution by NMR and UV–Vis spectroscopy, as well as in the solid state by IR, FIR spectroscopy and single crystal X-ray diffraction. The complexes display distorted octahedral geometries. X-ray structures of 1 and 2 reveal that the ReCl₂NP fragments are equatorially disposed and the oxygens, terminal oxo and alcoholato, lie in axial positions. The pyrimidine coordinates as a monodentate or bridging ligand. Detailed temperature dependent ¹H NMR analysis for both 1 and 2 shows that in solution the diaza moiety exhibits hindered rotation about the Re–N bond. Furthermore two concomitant conformation changes, one in the metallacycle and the second in the phosphorus cycle, are also observed for dimer 2.     

Chiral supramolecular metal-organic architectures from dinuclear copper complexes

Two new chiral dinuclear Cu(II) complexes [Cu₂(μ-Cl)₂(HL¹)₂] · C₂H₅OH (1) and [Cu₂(μ-Cl)₂(HL²)₂] · CH₃OH (2), have been synthesized and structurally characterized, where the chiral ligands H₂L¹ and H₂L² are derived from the chiral amino alcohols (S)-(−)-2-amino-3-phenyl-1-propanol and (S)-(+)-2-phenylglycinol. Single-crystal X-ray crystallographic analyses revealed that in these complexes, the dominant hydrogen bonding property of metal bound chloride anion directs the self assembly of complex molecules through C–H···Cl hydrogen bonding interactions leading to the formation of intriguing hydrogen bonded metallo-supramolecular architectures in their respective crystal lattices. The supramolecular systems described here belong to the rare class of metal-organic architectures that are formed as a result of metal directed hydrogen bonding interactions among chiral complex molecules. Complexes 1 and 2 are further characterized by IR, ESR, UV–Vis and CD spectroscopy.