Ferromagnetic coupling in trinuclear, partial cubane Cu(II) complexes with a micro(3)-OH core: magnetostructural correlations

Three new trinuclear copper(II) complexes, [(CuL(1))(3)(micro(3)-OH)][ClO(4)](2).3 H(2)O (1), [(CuL(2))(3)(micro(3)-OH)][ClO(4)](2).H(2)O (2), and [(CuL(3))(3)(micro(3)-OH)][ClO(4)](2).7 H(2)O (3) have been synthesized from the three tridentate Schiff bases HL(1), HL(2), and HL(3) (HL(1)=6- aminomethyl-3-methyl-1-phenyl-4-azahex-2-en-1-one, HL(2)=6-aminoethyl-3-methyl-1-phenyl-4-azahex-2-en-1-one, and HL(3)=6-aminodimethyl-3-methyl-1-phenyl-4-azahex-2-en-1-one). They have been characterized by X-ray crystallography and IR and UV spectroscopy, and their magnetic properties have been investigated. All the compounds contain a partial cubane [Cu(3)O(4)] core consisting of the trinuclear unit [(CuL)(3)(micro(3)-OH)](2+), perchlorate ions, and water molecules. In each of the complexes, the copper atoms are five-coordinate with a distorted square-pyramidal geometry except complex 1, in which one of the Cu(II) of the trinuclear unit is weakly coordinated to one of the perchlorate ions. Magnetic measurements performed in SQUID MPMS-XL7 using polycrystalline samples at an applied field of 2 kOe indicate a global intramolecular ferromagnetic coupling. Magnetostructural correlations have been calculated on the basis of theoretical models without symmetry restriction. Continuous shape measurements are an appropriate tool for establishing the degree of distortion of the Cu(II) from square-planar geometry. Structural, theoretical, and experimental magnetic data indicate that the higher the degree of distortion, the greater the ferromagnetic coupling.     

Copper(II) complexes with singly condensed tridentate Schiff-base ligands incorporating 1-benzoylacetone

Two copper(II) complexes [CuL¹Cl]_n (1) and [CuL²Cl] (2) with singly condensed tridentate Schiff-base ligands [HL¹ = 6-amino-3-methyl-1-phenyl-4-azahex-3-en-1-one and HL² = 6-diethylamino-3-methyl-1-phenyl-4-azahex-3-en-1-one] have been synthesized and structurally characterized by X-ray crystallography. Complex 1 is a single-chloro-bridged one-dimensional polymer, whereas 2 is a monomeric square-planar complex. The H-bonding interactions of the amine hydrogen and the non-bonding interactions of phenyl groups in the Schiff base play important roles for the structural variations.     

Stabilization of a helical water chain in a metal-organic host of a trinuclear Schiff base complex

Three heterometallic trinuclear Schiff base complexes, [{CuL1(H2O)}2Ni(CN)4].4H2O (1), [{CuL2(H2O)}2Ni(CN)4] (2), and [{CuL3(H2O)}2Ni(CN)4] (3) (HL1=7-amino-4-methyl-5-azahept-3-en-2-one, HL2=7-methylamino-4-methyl-5-azahept-3-en-2-one, and HL3=7-dimethylamino-4-methyl-5-azahept-3-en-2-one), were synthesized. All three complexes were characterized by elemental analysis, IR and UV spectroscopies, and thermal analysis. Two of them (1 and 3) were also characterized by single crystal X-ray crystallography. Complex 1 forms a hydrogen-bonded one-dimensional metal-organic framework that stabilizes a helical water chain into its cavity, but when any of the amine hydrogen atoms of the Schiff base are replaced by methyl groups, as in L2 and L3, the water chain vanishes, showing explicitly the importance of the host-guest H-bonding interactions for the stabilization of a water cluster.     

Supramolecular chelate copper(II) complex with 4-[(ethoxyimino)(phenyl)methyl]-5-methyl-2-phenyl-1Hpyrazol-3(2H)-one: Synthesis, crystal structure, and properties

A supramolecular Cu(II) complex, [Cu(L)₂(H₂O)]·C₂H₅OH {HL = 4-[(ethoxyimino)(phenyl)methyl]-5-methyl-2-phenyl-1H-pyrazol-3(2H)-one]} was synthesized and characterized structurally. The structure of the Cu(II) complex consists of one Cu(II) atom, two bidentate L-units, one coordinated H₂O and one crystallization ethanol molecule. The Cu(II) atom of the complex has a slightly distorted tetragonal pyramidal geometry. Moreover, every Cu(II) complex molecule links four other molecules into an infinite 2D-layer supramolecular structure via intermolecular O-H…O, O-H…N, and C-H…O hydrogen bonds.     

Copper(II) azide complexes with mono-anionic tridentate Schiff-base ligands: monomer versus dimer

Three new copper(II) complexes [CuL¹N₃]₂ (1), [CuL²N₃] (2) and [CuL³N₃] (3) with three very similar tridentate Schiff base ligands [HL¹?=?6-diethylamino-3-methyl-1-phenyl-4-azahex-3-en-1-one, HL²?=?6-amino-3-methyl-1-phenyl-4-azahex-3-en-1-one and HL³?=?6-amino-3-methyl-1-phenyl-4-azasept-3-en-1-one] have been synthesized and structurally characterized by X-ray crystallography. In complex 1 half of the molecules are basal-apical, end-on azido bridged dimers and the remaining half are square-planar monomers whereas all the molecules in complexes 2 and 3 are monomers with square-planar geometry around Cu(II). A competition between the coordinate bond and H-bond seems to be responsible for the difference in structure of the complexes.     

Cu(I) and Pb(II) complexes containing new tris(7-naphthyridyl)methane derivatives: synthesis, structures, spectroscopy and geometric conversion

Two novel facial-capping tris-naphthyridyl compounds, 2-chloro-5-methyl-7-((2,4-dimethyl-1,8-naphthyridin-7(1H)-ylidene)(2,4-dimethyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(1)) and 2-chloro-7-((2-methyl-1,8-naphthyridin-7(1H)-ylidene)(2-methyl-1,8-naphthyridin-7-yl))methyl-1,8-naphthyridine (L(2)), as well as their Cu(i) and Pb(ii) complexes, [CuL(a)(PPh(3))]BF(4) (1) (PPh(3) = triphenylphosphine, L(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methane), [CuL(b)(PPh(3))]BF(4) (2) (L(b) = bis(2-methyl-1,8-naphthyridin-7-yl)(2-chloro-1,8-naphthyridin-7-yl)methane), [Pb(OL(a))(NO(3))(2)] (3) (OL(a) = bis(2,4-dimethyl-1,8-naphthyridin-7-yl)(2-chloro-5-methyl-1,8-naphthyridin-7-yl)methanol) and [Pb(L(b))(2)][Pb(CH(3)OH)(NO(3))(4)] (4), have been synthesized and characterized by X-ray diffraction analysis, MS, NMR and elemental analysis. The structural investigations revealed that the transfer of the H-atom at the central carbon to an adjacent naphthyridine-N atom affords L(1) and L(2) possessing large conjugated architectures, and the central carbon atoms adopt the sp(2) hybridized bonding mode. The reversible hydrogen transfer and a geometric configuration conversion from sp(2) to sp(3) of the central carbon atom were observed when Pb(II) and Cu(I) were coordinated to L(1) or L(2). The molecular energy changes accompanying the hydrogen migration and titration of H(+) to different receptor-N at L(1) were calculated by density functional theory (DFT) at the SCRF-B3LYP/6-311++G(d,p) level in a CH(2)Cl(2) solution, and the observed lowest-energy absorption and emission for L(1) and L(2) can be tentatively assigned to an intramolecular charge transfer (ICT) transition in nature.     

Two one-dimension copper(II) coordination polymers based on imine-based bidentate Schiff-base ligand: synthesis, crystal structure and luminescent properties

Two new one-dimension copper(II) coordination polymers [CuL(2)(NCS)(2)](n) (1) and [CuL(2)(NO(3))(2)](n) (2) (L=(C(5)H(4)N)C(CH(3))=N-N=(CH(3))C(C(5)H(4)N)) have been synthesized and characterized by IR, elemental analysis, TG technique and X-ray crystallography. Each Cu(II) atom has a distorted octahedral N(6) (1) or N(4)O(2) (2) environment with four pyridyl N atoms from four ligands and two N atoms from two NCS(-) anions for polymer 1 or two O atoms from two NO(3)(-) anions for polymer 2, respectively. A pair of bis-monodentate bridging ligands links two Cu(II) centers to form one dimension chain structure containing bimetallic 22-membered macrometallacyclic rings. 1D chain is held together with its neighboring ones via C-H?S hydrogen bonds for 1 and C-H?O hydrogen bonds, C-H?π interactions for 2 to form a 3D supramolecular structure, respectively. The luminescent properties of the polymers 1 and 2 were investigated in the solid state at room temperature.     

Copper(II), cobalt(II), and nickel(II) complexes with a bulky anthracene-based carboxylic ligand: syntheses, crystal structures, and magnetic properties

To systematically explore the influence of the bulky aromatic ring skeleton with a large conjugated pi-system on the structures and properties of their complexes, six CuII, CoII, and NiII complexes with the anthracene-based carboxylic ligand anthracene-9-carboxylic acid (HL1), were synthesized and characterized, sometimes incorporating different auxiliary ligands: [Cu2(L1)4(CH3OH)2](CH3OH) (1), [Cu4(L1)6(L2)4](NO3)2(H2O)2 (2), {[Cu2(L1)4(L3)](CH3OH)0.25}infinity (3), [Co2(L1)4(L4)2(micro-H2O)](CH3OH) (4), {[Co(L1)2(L5)(CH3OH)2]}infinity (5), and {[Ni(L1)2(L5)(CH3OH)2]}infinity (6) (L2 = 2,2'-bipyridine, L3 = 1,4-diazabicyclo[2.2.2]octane, L4 = 1,10-phenanthroline, and L5 = 4,4'-bipyridine). 1 has a dinuclear structure that is further assembled to form a one-dimensional (1D) chain and then a two-dimensional (2D) network by the C-H...O H-bonding and pi...pi stacking interactions jointly. 2 takes a tetranuclear structure due to the existence of the chelating L2 ligand. 3 possesses a 1D chain structure by incorporating the related auxiliary ligand L3, which is further interlinked via interchain pi...pi stacking, resulting in a three-dimensional (3D) network. 4 also has a dinuclear structure and then forms a higher-dimensional supramolecular network through intermolecular pi...pi stacking and/or C-H...pi interactions. 5 and 6 are isostructural complexes, except they involve different metal ions, showing 1D chain structures, which are also assembled into 2D networks from the different crystallographic directions by interchain pi...pi stacking and C-H...pi interactions, respectively. The results reveal that the steric bulk of the anthracene ring in HL1 plays an important role in the formation of 1-6. The magnetic properties of the complexes were investigated, and the very long intermetallic distances result in weak magnetic coupling, with the exception of 1 and 3, which adopt the typical paddle-wheel structure of copper acetate and are thus strongly coupled.     

Different supramolecular hydrogen bond structures and significant changes in magnetic properties in dinuclear mu 2-1,1-N3 copper(II) complexes with very similar tridentate Schiff base blocking ligands

Three new basal-apical, mu(2)-1,1-azide bridged complexes, [CuL(1)(N(3))](2) (1), [CuL(2)(N(3))](2) (2) and [CuL(3)(N(3))](2) (3) with very similar tridentate Schiff base blocking ligands [L(1) = N-(3-aminopropyl)salicylaldimine, L(2) = 7-amino-4-methyl-5-azahept-3-en-2-one and L(3) = 8-amino-4-methyl-5-azaoct-3-en-2-one) have been synthesised and their molecular structures determined by X-ray crystallography. In complex 1, there is no inter-dimer H-bonding. However, complexes 2 and 3 form two different supramolecular structures in which the dinuclear entities are linked by strong H-bonds giving one-dimensional systems. Variable-temperature (300-2 K) magnetic susceptibility measurements and magnetization measurements at 2 K reveal that complexes and have antiferromagnetic coupling while has ferromagnetic coupling which is also confirmed by EPR spectra at 4-300 K. Magnetostructural correlations have been made taking into consideration both the azido bridging ligands and the existence of intermolecular hydrogen bonds in complexes 2 and 3.     

Heterospin systems constructed from [Cu2Ln]3+ and [Ni(mnt)2]1-,2- Tectons: First 3p-3d-4f complexes (mnt = maleonitriledithiolato)

New heterospin complexes have been obtained by combining the binuclear complexes [{Cu(H(2)O)L(1)}Ln(O(2)NO)(3)] or [{CuL(2)}Ln(O(2)NO)(3)] (L(1) = N,N'-propylene-di(3-methoxysalicylideneiminato); L(2) = N,N'-ethylene-di(3-methoxysalicylideneiminato); Ln = Gd(3+), Sm(3+), Tb(3+)), with the mononuclear [CuL(1)(2)] and the nickel dithiolene complexes [Ni(mnt)(2)](q)- (q = 1, 2; mnt = maleonitriledithiolate), as follows: (1)infinity[{CuL(1)}(2)Ln(O(2)NO){Ni(mnt)(2)}].Solv.CH(3)CN (Ln = Gd(3+), Solv = CH(3)OH (1), Ln = Sm(3+), Solv = CH(3)CN (2)) and [{(CH(3)OH)CuL(2)}(2)Sm(O(2)NO)][Ni(mnt)(2)] (3) with [Ni(mnt)2]2-, [{(CH(3)CN)CuL(1)}(2)Ln(H(2)O)][Ni(mnt)(2)]3.2CH(3)CN (Ln = Gd(3+) (4), Sm(3+) (5), Tb(3+) (6)), and [{(CH(3)OH)CuL(2)}{CuL(2)}Gd(O(2)NO){Ni(mnt)(2)}][Ni(mnt)(2)].CH(2)Cl(2) (7) with [Ni(mnt))(2]*-. Trinuclear, almost linear, [CuLnCu] motifs are found in all the compounds. In the isostructural 1 and 2, two trans cyano groups from a [Ni(mnt)2]2- unit bridge two trimetallic nodes through axial coordination to the Cu centers, thus leading to the establishment of infinite chains. 3 is an ionic compound, containing discrete [{(CH(3)OH)CuL(2)}(2)Sm(O(2)NO)](2+) cations and [Ni(mnt)(2)](2-) anions. Within the series 4-6, layers of discrete [CuLnCu](3+) motifs alternate with stacks of interacting [Ni(mnt)(2)](*-) radical anions, for which two overlap modes, providing two different types of stacks, can be disclosed. The strength of the intermolecular interactions between the open-shell species is estimated through extended Hückel calculations. In compound 7, [Ni(mnt)(2)](*-) radical anions coordinate group one of the Cu centers of a trinuclear [Cu(2)Gd] motif through a CN, while discrete [Ni(mnt)(2)](*-) units are also present, overlapping in between, but also with the coordinated ones. Furthermore, the [Cu(2)Gd] moieties dimerize each other upon linkage by two nitrato groups, both acting as chelate toward the gadolinium ion from one unit and monodentate toward a Cu ion from the other unit. The magnetic properties of the gadolinium-containing complexes have been determined. Ferromagnetic exchange interactions within the trinuclear [Cu(2)Gd] motifs occur. In the compounds 4 and 7, the [Ni(mnt)(2)](*-) radical anions contribution to the magnetization is clearly observed in the high-temperature regime, and most of it vanishes upon temperature decrease, very likely because of the rather strong antiferromagnetic exchange interactions between the open-shell species. The extent of the exchange interaction in the compound 7, which was found to be antiferromagnetic, between the coordinated Cu center and the corresponding [Ni(mnt)(2)](*-) radical anion, bearing mostly a 3p spin type, was estimated through CASSCF/CASPT2 calculations. Compound 6 exhibits a slow relaxation of the magnetization.     

Synthesis, characterization, DNA interaction and cleavage, and in vitro cytotoxicity of copper(II) mixed-ligand complexes with 2-phenyl-3-hydroxy-4(1H)-quinolinone

A series of mixed-ligand complexes [Cu(qui)(L)]NO(3)·xH(2)O (1-6), where Hqui = 2-phenyl-3-hydroxy-4(1H)-quinolinone, L = 2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), bis(2-pyridyl)amine (ambpy) (3), 5-methyl-1,10-phenanthroline (mphen) (4), 5-nitro-1,10-phenanthroline (nphen) (5) and bathophenanthroline (bphen) (6), have been synthesized and fully characterized. The X-ray structures of [Cu(qui)(phen)]NO(3)·H(2)O (2) and [Cu(qui)(ambpy)]NO(3) (3a) show a slightly distorted square-planar geometry in the vicinity of the central copper(II) atom. An in vitro cytotoxicity study of the complexes found significant activity against human osteosarcoma (HOS) and human breast adenocarcinoma (MCF7) cell lines, with the best results for complex 6, where IC(50) equals to 2.1 ± 0.2 μM, and 2.2 ± 0.4 μM, respectively. The strong interactions of the complexes with calf thymus DNA (CT-DNA) and high ability to cleave pUC19 DNA plasmid were found. A correlation has been found between the in vitro cytotoxicity and DNA cleavage studies of the complexes.     

Copper(I) Nitro Complex with an Anionic [HB(3,5-Me(2)Pz)(3)](-) Ligand: A Synthetic Model for the Copper Nitrite Reductase Active Site

The new copper(I) nitro complex [(Ph(3)P)(2)N][Cu(HB(3,5-Me(2)Pz)(3))(NO(2))] (2), containing the anionic hydrotris(3,5-dimethylpyrazolyl)borate ligand, was synthesized, and its structural features were probed using X-ray crystallography. Complex 2 was found to cocrystallize with a water molecule, and X-ray crystallographic analysis showed that the resulting molecule had the structure [(Ph(3)P)(2)N][Cu(HB(3,5-Me(2)Pz)(3))(NO(2))]·H(2)O (3), containing a water hydrogen bonded to an oxygen of the nitrite moiety. This complex represents the first example in the solid state of an analogue of the nitrous acid intermediate (CuNO(2)H). A comparison of the nitrite reduction reactivity of the electron-rich ligand containing the CuNO(2) complex 2 with that of the known neutral ligand containing the CuNO(2) complex [Cu(HC(3,5-Me(2)Pz)(3))(NO(2))] (1) shows that reactivity is significantly influenced by the electron density around the copper and nitrite centers. The detailed mechanisms of nitrite reduction reactions of 1 and 2 with acetic acid were explored by using density functional theory calculations. Overall, the results of this effort show that synthetic models, based on neutral HC(3,5-Me(2)Pz)(3) and anionic [HB(3,5-Me(2)Pz)(3)](-) ligands, mimic the electronic influence of (His)(3) ligands in the environment of the type II copper center of copper nitrite reductases (Cu-NIRs).     

2D coordination polymers of macrocyclic oxamide with polycarboxylates: syntheses, crystal structures and magnetic properties

Five new 2D coordination polymers, [Co(nip)(CuL)(H(2)O)]·CH(3)OH (1), [Mn(ip)(NiL)]·0.63H(2)O (2), [Cu(ip)(CuL)] (3), [Mn(6)(CuL)(6)(btc)(4)(H(2)O)(4)]·7H(2)O (4), and [Cu(CuL)(Hbtc)(H(2)O)] (5)(ML, H(2)L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-diene; H(2)nip = 5-nitroisophthalic acid; H(2)ip = m-isophthalic acid; H(3)btc = 1,3,5-benzenetricarboxylic acid) have been synthesized by a solvothermal method and characterized by single-crystal X-ray diffraction. Complexes 1-5 exhibit different 2D layered structures formed by Co(2)Cu(2) (1), Mn(2)Ni(2) (2), Cu(4) (3), Mn(3)Ni(3) (4), Cu(4) (5) units, respectively, via the oxamide and diverse carboxylic acid bridges. Compounds 1, 2, 3 and 5 are uninodal 4-connected (4, 4)-grids topology, while complex 4 possesses a 2D network with (3, 4)-connected (4(2).8)(4)(4(3).6(2).8)(3) topology. The results of magnetic determination show pronounced antiferromagnetic interactions in 1-4.     

Neutral mononuclear, dinuclear, tetranuclear d7/d10 metal complexes containing bis-pyrazole/pyridine ligands supported by 2,6-bis(3-pyrazolyl)pyridine: synthesis, structure, spectra, and catalytic activity

A series of novel bis-pyrazole/pyridine complexes, [Zn(2)(HL(1))(2)(μ(2)-SO(4))](2)·EtOH·H(2)O (1), [Co(2)(HL(1))(2)(μ(2)-SO(4))](2)·2DMF·6H(2)O (2), [Zn(4)(HL(1))(4)(μ(4)-SO(4))][OH](2) (3), [Zn(2)(HL(2))(2)(μ(2)-SO(4))]·2H(2)O (4), [Zn(H(2)L(2))(H(2)O)(2)](SO(4))·0.87H(2)O (5) (H(2)L(1) = 2,6-di-(5-phenyl-1H-pyrazol-3-yl)pyridine, H(2)L(2) = 2,6-di-(5-methyl-1H-pyrazol-3-yl)pyridine), were synthesized hydrothermally from the self-assembly of Zn(II) or Co(II) with different types of bipyrazolyl/pyridine derivative ligands. All the complexes were characterized by elemental analysis, IR and UV-vis spectroscopy, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Structural analyses revealed that metal atoms (Zn and Co) in complexes 1-5 are five-coordination modes, forming slightly distorted trigonal bipyramidal geometries. In complexes 1-3, H(2)L(1) ligand connected the two metal centers via the tetradentate fashion, and the same form of connection was found in complex 4 with H(2)L(2) ligand. While in complex 5, H(2)L(2) only connected with one metal center via the tridentate fashion, which was different from those in complexes 1-4. Additionally, there are abundant hydrogen bonding interactions in complexes 1-4. Interestingly, for hydrogen bonding connecting fashions being different, the molecules for the complexes 1 and 4 are held together by the hydrogen bond to form a 1D supramolecular structure, whereas complexes 2 and 3 are a hydrogen bonded dimer. In addition, quantum chemical calculations for 1, 3, and 4, thermal behaviors and photoluminescent properties for 1 and 3-5 were performed and discussed in detail. In the mean time, we found that these complexes had potential catalytic activity for the oxidation reaction of cyclohexane.     

Structural modulation of Cu(I) and Cu(II) complexes of sterically hindered tripyridine ligands by the bridgehead alkyl groups

Structures of Cu(I) and Cu(II) complexes of sterically hindered tripyridine ligands RL = tris(6-methyl-2-pyridyl)methane (HL), 1,1,1-tris(6-methyl-2-pyridyl)ethane (MeL), and 1,1,1-tris(6-methyl-2-pyridyl)propane (EtL), [Cu(RL)(MeCN)]PF(6) (1-3), [Cu(RL)(SO(4))] (4-6), and [Cu(RL)(NO(3))(2)] (7-9), have been explored in the solid state and in solution to gain some insights into modulation of the copper coordination structures by bridgehead alkyl groups (CH, CMe, and CEt). The crystal structures of 1-9 show that RL binds a copper ion in a tridentate facial-capping mode, except for 3, where EtL chelates in a bidentate mode with two pyridyl nitrogen atoms. To avoid the steric repulsion between the bridgehead alkyl group and the 3-H(py) atoms, the pyridine rings in Cu(I) and Cu(II) complexes of MeL and EtL shift toward the Cu side as compared to those in Cu(I) and Cu(II) complexes of HL, leading to the significant differences in the nonbonding interatomic distances, H.H (between the 3-H(py) atoms), N.N (between the N(py) atoms), and C.C (between the 6-Me carbon atoms), the Cu-N(py), Cu-N(MeCN), and Cu-O bond distances, and the tilt of the pyridine rings. The copper coordination geometries in 4-6, where a SO(4) ligand chelates in a bidentate mode, are varied from a square pyramid of 4 to distorted trigonal bipyramids of 5 and 6. Such structural differences are not observed for 7-9, where two NO(3) ligands coordinate in a monodentate mode. The structures of 1-9 in solution are investigated by means of the electronic, (1)H NMR, and ESR spectroscopy. The (1)H NMR spectra show that the structures of 1-3 in the solid state are kept in solution with rapid coordination exchange of the pyridine rings. The electronic and the ESR spectra reveal the structural changes of 5 and 6 in solution. The bridgehead alkyl groups and 6-Me groups in the sterically hindered tripyridine ligand play important roles in modulating the copper coordination structures.     

Mononuclear, dinuclear, hexanuclear, and one-dimensional polymeric silver complexes having ligand-supported and unsupported argentophilic interactions stabilized by pincer-like 2,6-bis(5-pyrazolyl)pyridine ligands

The mononuclear complexes [Ag(H2L1)(Py)2](NO3) x H2O (1, H2L1 = 2,6-bis(5-methyl-1H-pyrazol-3-yl)pyridine) and [Ag(NO3)(L()] (2, L2 = 2,6-bis(5-methyl-1-isopropyl-1H-pyrazol-3-yl)pyridine), dinuclear complex [Ag2(H2L3)2(HL4)2] (3, H2L3 = 2,6-bis(5-phenyl-1H-pyrazol-3-yl)pyridine, HL4 = 6-(5-phenyl-1H-pyrazolyl-3-yl)picolinate), one-dimensional polymer {[Ag2(H2L1)2](NO3)2 x H2O}(n) (4), and hexanuclear clusters [Ag6(HL1)4](X)2 (X = NO3-, 5 ; BF4-, 6 ; ClO4-, 7) stabilized by pincer-like bispyrazolyl ligands have been prepared and characterized using (1)H NMR spectroscopy, elemental analysis, IR spectroscopy, luminescence spectroscopy and X-ray diffraction. In complex , there is a ligand unsupported Ag-Ag bond between the two silver atoms. Complex displays a one-dimensional polymer consisting of an infinite Ag-Ag chain and every two adjacent silver ions are bridged by an H2L1 ligand. Complexes and have the same Ag6 cores in which six silver atoms are held together by four HL1 and five Ag-Ag bonds, while complex was held together by six Ag-Ag bonds. The silver-silver distances in these complexes are found in the range of 2.874(1)-3.333(2) A for ligand supported, and 3.040(1) A for ligand unsupported Ag-Ag bonds, respectively. Complexes 3-7 are strongly luminescent due to either intraligand or metal-ligand charge transfer processes.     

Synthesis, structure, and magnetic behavior of a series of trinuclear Schiff base complexes of 5f (UIV, ThIV) and 3d (CuII, ZnII) ions

The reaction of [M(H(2)L(i))] (M = Cu, Zn) and U(acac)(4) in refluxing pyridine produced the trinuclear complexes [[ML(i)(py)(x)](2)U] [L(i) = N,N'-bis(3-hydroxysalicylidene)-R, R = 1,2-ethanediamine (i = 1), 2-methyl-1,2-propanediamine (i = 2), 1,2-cyclohexanediamine (i = 3), 1,2-phenylenediamine (i = 4), 4,5-dimethyl-1,2-phenylenediamine (i = 5), 1,3-propanediamine (i = 6), 2,2-dimethyl-1,3-propanediamine (i = 7), 2-amino-benzylamine (i = 8), or 1,4-butanediamine (i = 9); x = 0 or 1]. The crystal structures show that the central U(IV) ion adopts the same dodecahedral configuration in all of these compounds, while the Cu(II) ion coordination geometry and the Cu...U distance vary with the length of the diimino chain of the Schiff base ligand L(i). These geometrical parameters have a major influence on the magnetic properties of the complexes. For the smallest Cu...U distances (i = 1-5), the Cu-U coupling is antiferromagnetic and weak antiferromagnetic interactions are present between the Cu(II) ions, while for the largest Cu...U distances (i = 6-9), the Cu-U coupling is ferromagnetic and no interaction is observed between the Cu(II) ions. The magnetic behavior of the [[CuL(i)](2)Th] compounds (i = 1, 2), in which the Th(IV) ion is diamagnetic, confirms the presence of weak intramolecular antiferromagnetic coupling between the Cu(II) ions.     

Pointers toward the occurrence of C-F...F-C interaction: Experimental charge density analysis of 1-(4-fluorophenyl)-3,6,6-trimethyl-2-phenyl-1,5,6,7-tetrahydro-4H-indol-4-one and 1-(4-fluorophenyl)-6-methoxy-2-phenyl-1,2,3,4-tetrahydroisoquinoline

A charge density study of crystalline 1-(4-fluorophenyl)-3,6,6-trimethyl-2-phenyl-1,5,6,7-tetrahydro-4H-indol-4-one (A) and 1-(4-fluorophenyl)-6-methoxy-2-phenyl-1,2,3,4-tetrahydroisoquinoline (B) has been carried out using high-resolution X-ray diffraction data collected at 113(2) K. Weak intermolecular interactions of the type C-H...O, C-H...pi, and pi...pi hold the molecules together in the crystal lattice along with interactions of the type C-H...F and unusual C-F...F-C examined via charge density analysis. The topological features are evaluated in terms of Bader's theory of atoms in molecules through the first four criteria of Koch and Popelier. The C-F...F-C contact is observed to be across the center of symmetry in B and not in A, and further, this interaction appears to possess a certain correlation with the electron density properties at the critical point which suggests that such an interaction fits into the hierarchy of weak interactions.     

Cu(NO3)2.3H2O-mediated synthesis of 4'-(2-pyridyl)-2,2':6',2' '-terpyridine (L2) from N-(2-pyridylmethyl)pyridine-2-methylketimine (L1). A C-C bond-forming reaction and the structure of {[Cu(L2)(OH)(NO3)][Cu(L2)(NO3)2]}.2H2O

N-(2-Pyridylmethyl)pyridine-2-methylketimine (L1) was synthesized from equimolar quantities of (2-pyridyl)methylamine and 2-acetylpyridine. Methanolic solution of L1 reacted readily with Cu(NO3)2.3H2O in air, affording green solid of composition {[Cu(L2)(OH)(NO3)][Cu(L2)(NO3)2]}.2H2O, where L2 is 4'-(2-pyridyl)-2,2':6',2' '-terpyridine. Oxidation of the active methylene group of L1 to an imide and then condensation with 2-acetylpyridine involving a C-C bond-forming reaction, mediated by a Cu2+ ion, are the essential steps involved in the conversion of L1 to L2. L2 is isolated by extrusion of Cu2+ with EDTA(2-). The copper center in [Cu(L2)(OH)(NO3)] has a mer-N3O3 environment, and that in [Cu(L2)(NO3)2] has a distorted trigonal-bipyramidal geometry. Two H2O molecules held by C-H...O interactions are present in the predominantly hydrophobic channels of approximate cavity dimension 7.60 x 6.50 A created by aromatic rings through pi-pi interactions.     

Complexes of copper(II) with 3-(ortho-substituted phenylhydrazo)pentane-2,4-diones: syntheses, properties and catalytic activity for cyclohexane oxidation

Reactions of copper(II) with 3-phenylhydrazopentane-2,4-diones X-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) bearing a substituent in the ortho-position [X = OH (H(2)L(1)) 1, AsO(3)H(2) (H(3)L(2)) 2, Cl (HL(3)) 3, SO(3)H (H(2)L(4)) 4, COOCH(3) (HL(5)) 5, COOH (H(2)L(6)) 6, NO(2) (HL(7)) 7 or H (HL(8)) 8] lead to a variety of complexes including the monomeric [CuL(4)(H(2)O)(2)]·H(2)O 10, [CuL(4)(H(2)O)(2)] 11 and [Cu(HL(4))(2)(H(2)O)(4)] 12, the dimeric [Cu(2)(H(2)O)(2)(μ-HL(2))(2)] 9 and the polymeric [Cu(μ-L(6))](n)] 13 ones, often bearing two fused six-membered metallacycles. Complexes 10-12 can interconvert, depending on pH and temperature, whereas the Cu(II) reactions with 4 in the presence of cyanoguanidine or imidazole (im) afford the monomeric compound [Cu(H(2)O)(4){NCNC(NH(2))(2)}(2)](HL(4))(2)·6H(2)O 14 and the heteroligand polymer [Cu(μ-L(4))(im)](n)15, respectively. The compounds were characterized by single crystal X-ray diffraction (complexes), electrochemical and thermogravimetric studies, as well as elemental analysis, IR, (1)H and (13)C NMR spectroscopies (diones) and ESI-MS. The effects of the substituents in 1-8 on the HOMO-LUMO gap and the relative stability of the model compounds [Cu(OH)(L(8))(H(2)O)]·H(2)O, [Cu(L(1))(H(2)O)(2)]·H(2)O and [Cu(L(4))(H(2)O)(2)]·H(2)O are discussed on the basis of DFT calculations that show the stabilization follows the order: two fused 6-membered > two fused 6-membered/5-membered > one 6-membered metallacycles. Complexes 9, 10, 12 and 13 act as catalyst precursors for the peroxidative oxidation (with H(2)O(2)) of cyclohexane to cyclohexanol and cyclohexanone, in MeCN/H(2)O (total yields of ca. 20% with TONs up to 566), under mild conditions.