Synthesis, crystal structures and luminescent properties of manganese and zinc complexes with in situ ligand formation of 3-amino-4-(5-tetrazolyl)-1H-pyrazole

Three metal-organic frameworks, [Mn(HL)(N₃)] (1), [Mn(HL)Cl(H₂O)] (2) and [Zn₂(L)₂(H₂O)] (3) where H₂L = 3-amino-4-(5-tetrazolyl)-1H-pyrazole, have been yielded through in situ hydrothermal reactions of manganese(II) or zinc(II) salts, NaN₃ and 3-amino-4-cyano-1H-pyrazole (HACP). The crystal structure analysis reveals that 1-3 have different dense 3D frameworks with Schläfli symbols of {3·4²·5²·6}{3²·4³·5⁴·6⁶} for 1 which is an unprecedented (4,6)-connected framework, {4·12²}2{4²·12⁴} for 2 which is a typical sqc519 structure, and {4²·6}2{4⁴·6²·8⁸·10} for 3 which is a typical ant/anatase structure, respectively. The ligand takes three different coordination modes in 1-3 as 3- or 4-connector. In addition, the photoluminescence of complex 3 was studied in solid state at room temperature, together with its thermal analysis.     

Synthesis, structures and luminescent behaviour of tridentate salicylaldiminato-type borate complexes

Treatment of the ligands 3,5-tBu₂-2-(OH)C₆H₂CHNR [R = 2-(CO₂H)C₆H₄ (1a) and 2-(CO₂H)C₁₀H₆ (1b)] with trimethylborate, B(OMe)₃, in toluene yields, after work-up, the yellow crystalline complexes {[3,5-tBu₂-2-(O)C₆H₂CHNR]B(OMe)} [R = 2-(CO₂)C₆H₄ (2a) and 2-(CO₂)C₁₀H₆ (2b)], respectively. Further treatment of these complexes with trifluoromethanesulfonic (triflic) acid, CF₃SO₃H, followed by recrystallisation from tetrahydrofuran (thf) afforded the triflate salts [{3,5-tBu₂-2-(O)C₆H₂CHNR}B(thf)][CF₃SO₃] [R = 2-(CO₂)C₆H₄ (3a) and 2-(CO₂)C₁₀H₆ (3b)]. An electroluminescent device was constructed using 2a, which produced orange-green light with broad emission spectra (maximum brightness of 5 cd/m² being observed at 13 V). Compounds 1a and 2b·2MeCN have been characterised by single crystal X-ray structure determinations.     

Photophysical properties, electronic and crystal structures of luminescent diphosphine digold(I)-pyridine-2-thiolate complexes

Treatment of diphosphine digold(I) complexes, PP(AuCl)₂ [PP=bis(diphenylphosphino)methane, dppm; 1,6-bis(diphenylphosphino)hexane, dpph], with two equivalents of pyridine-2-thiol (HNS) in the presence of NaOCH₃ affords two luminescent diphosphine digold(I)-pyridine-2-thiolate complexes, dppm(AuSN)₂ (1) and dpph(AuSN)₂ (2), respectively. Both crystal structures have been determined by crystallographic studies. The intramolecular aurophilic contact of 3.0478(3) Å is observed in the crystal structure of 1, whereas there is not any aurophilic interaction present in the crystal lattices of 2. At room temperature, 1 shows a low-energy emission at ca. 660 nm as well as a very weak high-energy emission at ca. 496 nm in the solid state, but 2 shows only a strong high-energy one at ca. 482 nm. Thus, the emission energy strongly dependent on the Au(I)?Au(I) interaction can be demonstrated in the diphosphine digold(I) thiolates studied herein.     

Crystal structures and magnetic properties of two complexes synthesized from manganese and halogenophenyl-substituted nitronyl nitroxide

One-dimensional complex (1), [Mn(hfac)₂(NITPhF)]₂ and one binuclear radical complex (2), [Mn(hfac)₂(NITPhBr)]_∞ have been synthesized. Here hfac stands for hexafluoroacetylacetonate, NITPhF for 2-(4′-fluorophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and NITPhBr for 2-(4′-bromophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). All the two precursors were prepared and characterized by single-crystal X-ray diffraction analysis, IR, and magnetic analysis. In complex 1, the NITPhF radical acts as a bridge ligand linking two Mn(II) ions through the oxygen atom of the N-O group to form cyclic dimer. The dimers further connect two oxygen atoms of uncoordinated nitroxides of two adjacent radicals and yield one-dimensional chain sections. Instead in complex 2, the Mn(II) ions are bridged by the NITPhBr radicals through their N-O groups giving infinite one-dimensional chains. Magnetic susceptibility measurements indicate that both complex 1 and 2 behave ferrimagnetically. The Mn(II) ions interact antiferromagnetically with the direct bonding nitroxide group of the radicals although the structures of two complexes are different. The magnetic behaviors can be satisfactorily explained on the basis of the structural data.     

Synthesis, crystal structure and electroluminescent properties of a Schiff base zinc complex

A new complex of zinc with a Schiff base, zinc(N,N′-bis(salicylidene)-3, 6-dioxa-1, 8-diaminooctane monohydrate) (ZnBSO · H₂O), was synthesized and characterized by means of elemental analyses, IR spectra and DTA-TG. Its structure was determined by X-ray single crystal analysis. It was demonstrated that the zinc atom is coordinated by the two oxygen atoms in phenolate and two nitrogen atoms in imine of the ligand in a slightly distorted tetrahedral geometry, while the two oxygen atoms from the oxa-alkyl chain are not coordinated to Zn(II) atom. The energy levels of the HOMO, LUMO and the electrochemical band gap were determined by cyclic voltammeter. The electroluminescent devices with the complex as the emitter showed bright blue emission with a peak at 450 nm, which is same as the fluorescence of the complex in both solution and solid states.     

Three zinc-organic frameworks based on 1,4-benzenebis(thioacetic acid): Syntheses, crystal structures, and luminescent properties

A new flexible aromatic multithiocarboxylate ligand: 1,4-benzenebis(thioacetic acid) (H₂L), was synthesized and introduced to construct three interesting metal-organic frameworks (MOFs) with the photoluminescent properties. Three MOFs were characterized by the elemental analysis, infrared (IR) spectrum, and single crystal X-ray diffraction. [Zn₃L₃(2,2′-bipy)₂]_n (1) is a two-dimensional (2D) layered architecture that consists of the linear trinuclear units of Zn atoms. [ZnL(2,2′-bipy)(H₂O)]_n·0.7nH₂O (2) is a one-dimensional (1D) helical chain, which further forms a 2D structure with 30-membered ring with a size of 7.64 × 15.53 Å via O−H···O hydrogen bonds. [ZnL(phen)(H₂O)]_n·0.35nH₂O (3) presents a 2D supramolecular network through the O−H···O interactions. Their thermal and photoluminescent properties in solid state were given.     

Synthesis, structures and luminescent properties of new heterobimetallic Zn-4f Schiff base complexes

A series of new 3d-4f heterobimetallic Schiff base complexes of the general formula [Zn(μ-L²)Ln(NO₃)₃(H₂O)_n] (Ln = La 1, Nd 2, Gd 3, Er 4 and Yb 5; n = 1 or 2; H₂L² = N,N′-bis(3-methoxy-5-p-tolylsalicylidene)ethylene-1,2-diamine) are synthesized and characterized. Complexes 1, 2, 4 and 5 are structurally characterized by X-ray crystallography. The photophysical properties of these complexes are also investigated. At room temperature, complexes 1-5 exhibit similar solution absorption and emission spectra in the UV-Vis region. Furthermore, compounds 2, 4 and 5 exhibit solution emission corresponding to the lanthanide(III) ion in the near-infrared region at room temperature. The triplet state emission of the 3d-4f bimetallic complexes without energy transfer is also determined through the photophysical study of complex 3.     

Synthesis, crystal structures and biological evaluation of water-soluble zinc complexes of zwitterionic carboxylates

Three water-soluble zinc complexes, [Zn(Cbp)₂Br₂] (1) (Cbp = N-(4-carboxybenzyl)pyridinium), {[Zn(BCbpy)₂(H₂O)₄]₃Br₆·2(BCbpy)·2(4,4′-bipy)} (2) (BCbpy = 1-(4-carboxybenzyl)-4,4′-bipyridinium) and {[Zn₄(Bpybc)₆(H₂O)₁₂](OH)₈·9H₂O}_2n (3) (Bpybc = 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridinium), were synthesized and characterized by IR, elemental analysis and single-crystal X-ray crystallography. In complex 1, the central Zn atom adopts a distorted tetrahedral coordination geometry that is formed from two unidentate Cbp ligands and two Br atoms. For complex 2, the Zn atom in [Zn(BCbpy)₂(H₂O)₄]²⁺ is strongly coordinated by four water molecules and two N atoms from two BCbpy ligands, hence forming an octahedral geometry. In complex 3, each Bpybc ligand bridges two [Zn(H₂O)₃]²⁺ units through two terminal carboxylate groups in a monodentate coordination mode, thus forming a flowerlike two-dimensional network. Agarose gel electrophoresis (GE) and ethidium bromide (EB) displacement experiments indicated that complex 3 was capable of converting pBR322 DNA into open circular (OC) and linear forms, and exhibited high binding affinity toward calf-thymus DNA. MTT assay showed that complex 3 displayed inhibitory activities toward the proliferation of lung adenocarcinoma A549 and mouse sarcoma S-180 cells, with the IC₅₀ values being 27.3 and 48.8 μM, respectively.     

Synthesis, crystal structures, antimicrobial properties and enzyme inhibition studies of zinc(II) complexes of thiones

Zinc(II) complexes of thiones having the general formula [ZnL₂Cl₂] where L = N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu), tetramethylthiourea (Tmtu), N,N′-diethylthiourea (Detu), and diazinane-2-thione (Diaz), were prepared by reacting ZnCl₂ with the corresponding thiones. They were characterized by elemental analysis, IR and NMR spectroscopy and two of them {[(Tmtu)₂ZnCl₂] (1) and [(Diaz)₂ZnCl₂] (2)} using X-ray crystallography. The spectral data suggests that the coordination of thiones to zinc(II) occurs through the sulfur atom as indicated by an up field shift in the CS resonance of thiones in ¹³C NMR and downfield shift in N-H resonance in ¹H NMR. The crystal structures of the complexes show a tetrahedral coordination environment around the zinc atoms with the bond angles ranging from 99.33(5)° to 116.81(7)°. Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentration and the results showed that the complexes exhibited significant activities against gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and yeasts (Candida albicans, Saccharomyces cerevisiae). However, moderate activity was observed against molds (Aspergillus niger, Penicillium citrinum). The complexes were also tested for inhibition activity against an enzyme, Alkaline Phosphatase EC 3.1.3.1 and were found to be active inhibitors.     

Syntheses, structures and magnetic properties of two new metal complexes based on a pyridyl-diphosphonate ligand

Two new first-raw transition metal diphosphonate complexes, namely, {[Ni₃([hpyedpH)₂(H₂O)₄]·(H₂O)₂}_n (1) and [Mn[hpyedpH₂](H₂O)]_n (2), based on a multidentate ligand 1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid (hpyedpH₄) have been synthesized under hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and element analyses. The data reveals that complex 1 is a 2D layer structure, whereas the complex 2 possesses a 1D motif. The powder X-ray diffraction (PXRD) patterns for complexes 1 and 2 were collected as well, which match well with the ones calculated from their single-crystal structure data. Magnetic measurements show that complex 1 is a ferrimagnet with T_c = 5.0 K. Magnetic studies of complex 2 indicate antiferromagnetic behavior.     

Three zinc(II) complexes constructed from aromatic dicarboxylate and 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene: Syntheses, crystal structures and luminescent properties

To investigate the effect of organic anions on the coordination frameworks, we synthesized three new complexes, namely, Zn(DPA)(bpimb)_0.5(H₂O) (1), Zn(BDC)(bpimb)_0.5 (2) and Zn₂(SDBA)₂(bpimb)·H₂O (3) (H₂DPA = diphenic acid; H₂BDC = isophthalic acid; H₂SDBA = 4,4′-dicarboxybiphenylsulfone), which were obtained by the reactions of 1,4-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene (bpimb) as main ligand, and several aromatic polycarboxylate as organic anions with Zn(NO₃)₂·6H₂O. Single-crystal structure analysis shows that complex 1 is a one-dimensional chain structure, which is further interlinked into a higher-dimensional supramolecular framework by hydrogen-bonding interactions. In 2, BDC bridge Zn(II) atoms to give dimeric units, which are further linked by bpimb ligands to form sql nets. In 3, SDBA ligands and bpimb ligands connect Zn(II) ions into catenane-like two-dimensional layers. These catenane-like two-dimensional layers stack in an ABAB fashion to form a 3D supramolecular network. The distinct structures indicate three kinds of carboxylic ligands with different lengths and angles play fundamental roles in the formation of the final products. In addition, the luminescence measurements reveal that three complexes exhibit strong fluorescent emissions in the solid state at room temperature.     

Synthesis, crystal structures and magnetic properties of transition metal–azide complexes coordinated with pyridyl nitronyl nitroxides

Two novel complexes Co(N₃)₂(PNN)₄ (I) and Mn(N₃)₂(PNN)₂(CH₃OH)(C₂H₅OH) (II) (PNN=2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3–oxide) were synthesized and characterized by infrared spectra, elemental analyses and UV–Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. Complex I is a neutral five-spin system and adopts a centrosymmetric tetragonally compressed octahedral coordination geometry in which Co(II) ion is coordinated to four radicals through the nitrogen atoms of the pyridine rings and two azide anions occupying the axial positions. Complex II is a neutral three-spin system in which Mn(II) ion is bound to two azide anions, two alcohol molecules and two radicals through the nitrogen atom of pyridine rings, and shows one-dimensional chain structure via hydrogen bonds (d_ON=2.78 Å). The magnetic properties for complexes I and II have been investigated in the temperature range 2–300 K. A theoretical model has been developed for complex I and the magnetic behaviors for both complexes have been discussed in detail.     

Syntheses, crystal structures, and luminescence properties of lanthanide complexes with 5-carboxy-1-carboxymethyl-2-oxidopyridinium

Five new lanthanide complexes Ln(HL)₃(H₂O)₅ · 3H₂O (H₂L = 5-carboxy-1-carboxymethyl-2-oxidopyridinium, Ln = La (1), Sm (2), Eu (3),Tb (4), Dy (5)) have been synthesized and characterized by elemental analyses, FT-IR spectra and X-ray single crystal diffraction. All crystals are isostructural and crystallize in the triclinic space group . The metal center is nine-coordinated completely by two phenol O atoms, two chelating carboxylic O atoms from three HL ligands and five water molecules with a distorted tri-capped trigonal prismatic geometry. Photoluminescence studies revealed that complexes 2-4 exhibit strong fluorescent emission bands in the solid state at room temperature. The transition intensity varies in the order of Tb³⁺ > Dy³⁺ > Eu³⁺ > Sm³⁺.     

Synthesis and luminescent properties of the first series of lanthanide complexes based on sebacate and 2,5-pyridinedicarboxylate

By using 2,5-pyridinedicarboxylate and sebacate as rigid and flexible mixed carboxylate linkers, five new 3D lanthanide complexes, [Ln(seb)_0.5(2,5-pydc)(H₂O)] (Ln = Eu (1), Nd (2), Sm (3), Pr (4) and Tb (5), H₂pydc = 2,5-pyridinedicarboxylic acid, H₂seb = sebacate acid) with macroporous structures, have been synthesized. Complexes 1-5 were characterized by elemental analysis, ICP spectrometer and IR spectroscopy. In particular, the structures of 1-3 were further determined by single-crystal X-ray diffraction. Structural analyses reveal that complexes 1-3 have intricate 3D frameworks, which are constructed by 2,5-pyridinedicarboxylate and sebacate ligands. In addition, the thermogravimetric analysis of 1-3 and photoluminescent properties of 1 and 5 are also discussed in detail.     

In situ hydrothermal syntheses, crystal structures and luminescent properties of two novel zinc(II) coordination polymers based on tetrapyridyl ligand

Two novel Zn(II) coordination polymers, [Zn(2-pytpy)(fum)]_n·nH₂O (1) and [Zn₆(4-pytpy)₃(mal)₄]_n·5n(H₂O) (2), (2-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine, 4-pytpy = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H₂fum = fumaric acid and H₂mal = malic acid) have been hydrothermally synthesized and structurally characterized. Notably, in situ ligand reactions occur in the formation of complexes 1 and 2, in which maleic acid is converted into fumaric acid and malic acid, respectively. Complex 1 is a 1D infinite chain structure, which is extended into a supramolecular layer by intermolecular π…π stacking interactions. Complex 2 is a 3D network structure, in which the bidentate-bridging 4-pytpy ligands link the layers based on the tetranuclear Zn(II) subunits to form the (4,10)-connected network. The luminescent properties of 1 and 2 have been investigated with emission spectra and UV-Vis diffuse reflectance spectra in the solid state. Additionally, these two complexes possess great thermal stabilities.     

Synthesis, structure and magnetic properties of a two-dimensional manganese(II) complex with a maximum denticity of ethylenediaminetetraacetic ligand

A new Mn(II) complex, [Mn₂(edta)(H₂O)]_n·nH₂O (1) (H₄edta = ethylenediaminetetraacetic acid) has been synthesized by the reaction of MnCl₂·4H₂O and H₄edta under hydrothermal conditions, and was characterized by single-crystal X-ray diffraction study, variable temperature (1.8-300 K) magnetic measurement, and thermal gravity analysis. The result of X-ray crystallographic analysis reveals that complex 1 is the first two-dimensional (2D) Mn-edta coordination polymer with a grid-like (4,4)-topology, which is built from Mn-carboxylate chains and entirely deprotonated edta⁴⁻ ligands with a maximum denticity. The variable temperature magnetic data indicate that complex 1 exhibits strong antiferromagnetic couplings.     

Zinc(II) complexes with 1,8-naphthyridine-based ligand: Crystal structures and luminescent properties

The reactions of 2,4-dimethyl-7-(2-pyridylamino)-1,8-naphthyridine (L1) with Zn(ClO₄)₂ · 6H₂O, and bis(5,7-dimethyl-1,8-naphthyrid-2-yl)amine ligand (L2) with Zn(OAc)₂ · 2H₂O, ZnCl₂ or Zn(ClO₄)₂ · 6H₂O afforded four blue luminescent zinc(II) complexes, [Zn(L1)₂](ClO₄)₂ · 2CH₂Cl₂ (1), [Zn(L2)(OAc)₂] · CH₂Cl₂ (2), [Zn(L2)₂][ZnCl₄] · 3.5CH₂Cl₂ (3) and [Zn(L2)₂](ClO₄)₂ (4), respectively. Crystal structures of complexes 1-3 have been determined by X-ray structural analyses as mononuclear complexes with pseudo-tetrahedral geometry. The crystal packing of 1 reveals the coordination cation which is self-assembled to stair chains through aromatic π-π interactions. The intermolecular N-H?O hydrogen bond in 2 generates a centrosymmetric H-bonded dimer. However, the crystal lattice of 3 shows that the molecules are linked by extensive intermolecular hydrogen bonds between the amino groups and the anions, resulting in a one-dimensional zigzag chain. Furthermore, these molecular pairs or chains were self-assembled to two-dimensional sheets or three-dimensional networks through aromatic π-π interactions. All the zinc(II) complexes display intense intraligand ¹(π-π^∗) fluorescence with λ_max at 380 and 393 nm for 1, 385 and 404 nm for 2-4 in methanol at room temperature, respectively. Emission quantum yields of these complexes are in the range from 0.41 to 0.57. The broad emission bands in their solid-state emission spectra are attributed to intraligand ¹(π-π^∗) transition and aromatic π-π interactions as well.     

Synthesis, characterization, and crystal structures of hydrotris(2-mercapto-1-imidazolyl)borate-based zinc(II) and copper(I) complexes

The reaction of the tripod ligand hydrotris(2-mercapto-1-imidazolyl)borate Tm^xylyl with zinc(II) perchlorate in methanol afforded the mononuclear complex of the type [Tm^xylyl-Zn(mim^xylyl)]ClO₄ (1). Whereas under the same conditions, the reaction with copper(II) perchlorate gives rise to the simultaneous formation of the dinuclear copper(I) complex [Tm^xylylCu]₂ (2). The chemical formulae of the complexes have been characterized by elemental chemical analysis, IR-NMR spectroscopies, and single crystal X-ray methods. In complex 1, the zinc(II) atom displays a distorted tetrahedral environment. While in complex 2, the Tm^xylyl ligand bridges the two copper(I) atoms in an asymmetric manner with trigonal geometry. The inverted conformation of the ligand Tm^xylyl at the boron center, allows the B-H units to be directed towards the copper centers. The greater reactivity of the borohydride groups towards metal centers enhances the reduction of Cu(II) to Cu(I). The obtained kinetic results for the methylation reactions of 1 and 2 indicate that these bound thione complexes are less suitable to electrophilic attack than the thiolate ligand.     

Synthesis, anticancer activities, interaction with DNA and mitochondria of manganese complexes

Two new complexes [(Etdpa)MnCl₂] and [(Adpa)Mn(Cl)(H₂O)] (Etdpa = ethyl bis(2-pyridylmethyl)amino-2-propionate; Adpa = bis(2-pyridylmethyl)amino-2-propionic acid) were synthesized and characterized by spectral methods. The crystal structure of [(Etdpa)MnCl₂] shows that the Mn(II) atom is coordinated by three N atoms (N1, N2, N3), one oxygen atom (O1) of the ligand (Etdpa) and two chloride atoms (Cl1, Cl2), forming a distorted octahedral geometry. The binding interaction between ct-DNA and the synthesized complexes was relatively weak, but they can inhibit the induced swelling of Ca²⁺-loaded mitochondria in a dose-dependent manner. The [(Adpa)Mn(Cl)(H₂O)] can cause the obvious decrease of mitochondria membrane potential. The MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenpyltetra-zolium bromide) assay shows that the two Mn(II) complexes are more active against cancer cells. Especially [(Adpa)Mn(Cl)(H₂O)] can inhibit the proliferation of glioma cells with IC₅₀ 9.5 μM. Experimental results indicate that the [(Adpa)Mn(Cl)(H₂O)] could be a new potential antitumor complex to target the mitochondria.