Heteroleptic pyrimidine-2-olate and 4,4[prime or minute]-bipyridine copper(II) layered metal-organic frameworks with swelling properties

One-pot reaction of CuX2 salts (X = NO3, Cl, ClO4, AcO, SO(4)/2), 2-Hydroxypyrimidine hydrochloride (2-Hpymo.HCl) and 4,4'-bipyridine (4,4'-bpy), in H2O : ethanol : ammonia (20 : 10 : 5) solution, leads to isomorphous extended layered materials of type [Cu3(mu-OH)2(mu-Cl)2(mu-2-pymo)(mu-4,4'-bpy)3]nXn.mH2O (X = NO3 (1a), Cl (1b), ClO4 (1c), AcO (1d), SO(4)/2 (1e)). The single crystal X-ray crystallographic analysis performed on species exemplifies that it is built by 2D [Cu3(mu-OH)2(mu-Cl)2(mu-2-pymo)(mu-4,4'-bpy)3]n(n+) cationic sheets, which pack in a staggered fashion, with non coordinated NO3- anions and crystallisation water molecules included in the interlayer voids. XRPD studies performed on the species show a swelling response along the crystallographic a axis concomitant to aliphatic alcohol inclusion. Additionally, we have also studied the magnetic properties of , which show that its magnetic behaviour is dominated by the strong antiferromagnetic interactions taking place in the Cu3(mu-OH)2(mu-Cl)2 trinuclear cores.     

Construction of a Set of Cadmium（Ⅱ） Coordination Polymers with Atza and 2,2′-Bipy or 1,10-Phen Ligands （Atza=5-Aminotetrazole-1-acetato Anion）

Reactions of CdX2(X=NO3-, ClO4-) with Hatza (atza=5-aminotetrazole-1-acetato anion) and 2,2′-bipyridine (2,2′-bipy) or 1,10-phenanthroline (1,10-phen) in a methanol/aqueous solution produced a set of new Cd(Ⅱ) coordination polymers, {[Cd(atza)(H2O)(2,2′-bipy)]ClO4}n (1), {[Cd(atza)(H2O)(1,10-phen)]ClO4 }n (2), {[Cd(atza)(H2O)(2,2′-bipy)]NO3}n (3) and {[Cd(atza)2 (1,10-phen)]·0.5H2O}n (4). Single-crystal X-ray diffraction analysis reveals that each Cd(Ⅱ) ion has a distorted octahedral coordination geometry in 1-4, and the Cd(Ⅱ) ion centers are connected through the tridentate atza bridging ligands to form a 2D layer (1-3) or ID chain (4) structure. The fluorescent properties of 2 and 4 are also discussed.     

Synthesis, crystal structures and magnetic properties of dinuclear copper(II) compounds with NNO tridentate Schiff base ligands and bridging aliphatic diamine and aromatic diimine linkers

The synthesis and the characterization of new dinuclear copper(II) compounds of general formula [(L(a-d))(2)Cu(2)(μ-N-N)](ClO(4))(2) (1-6) with either neutral aliphatic diamine (N-N = piperazine, pip) or aromatic diimine (N-N = 4,4'-bipyridine, 4,4'-bipy) linker are reported. The copper ligands L(-) (L(a-) = (E)-2-((2-aminoethylimino)methyl)phenolate, L(b-) = (E)-2-((2-aminopropylimino)methyl)-phenolate, L(c-) = (E)-2-((2-aminoethylimino)methyl)4-nitrophenolate, L(d-) = (E)-2-((2-aminoethylimino)methyl)4-methoxyphenolate) are NNO tridentate Schiff bases derived from the monocondensation of a substituted salicylaldehyde 5-G-salH (G = NO(2), H, OMe) with ethylenediamine, en, or 1,3-propylenediamine, tn. The crystal structures of compounds [(L(a))(2)Cu(2)(MeOH)(2)(μ-4,4'-bipy)](ClO(4))(2) (1·2MeOH), [(L(b))(2)Cu(2)(MeOH)(2)(μ-4,4'-bipy)](ClO(4))(2) (2·2MeOH), [(L(d))(2)Cu(2)(μ-4,4'-bipy)](ClO(4))(2) (4), [(L(a))(2)Cu(2)(μ-pip)](ClO(4))(2) (5) and [(L(b))(2)Cu(2)(μ-pip)](ClO(4))(2) (6) have been determined, revealing the preferred (e-e)-chair conformation of the bridging piperazine in compounds 5 and 6. The presence of hydrogen-bond-mediated intermolecular interactions, that involve the methanol molecules, yields dimers of dinuclear units for 1·2MeOH, and infinite zig-zag chains for 2·2MeOH. The temperature dependences of the magnetic susceptibilities χ(M)(T) for all compounds were measured, indicating the presence of antiferromagnetic Cu-Cu exchange. For the compounds 2-4 with 4,4'-bipy, the coupling constants J are around -1 cm(-1), while in compound 1 no interaction could be detected. The compounds 5 and 6 with piperazine display higher Cu-Cu magnetic interactions through the σ-bonding backbone of the bridging molecule, with J around -8 cm(-1), and the coupling is favoured by the (e-e)-chair conformation of the diamine ring. The non-aromatic, but shorter, linker piperazine gives rise to stronger Cu-Cu antiferromagnetic couplings than the aromatic, but longer, 4,4'-bipyridine. In the latter case, the rotation along the C-C bond between the two pyridyl rings and the consequent non co-planarity of the two copper coordination planes play an important role in determining the magnetic communication. EPR studies reveal that the dinuclear species are not stable in solution, yielding the solvated [(L)Cu(MeOH)](+) and the mononuclear [(L)Cu(N-N)](+) species; it appears that the limited solubility of the dinuclear compounds is responsible for their isolation in the solid state.     

Influence of the synthetic conditions on the structural diversity of extended manganese-oxalato-1,2-bis(4-pyridyl)ethylene systems

We report herein the synthesis and physicochemical characterization of eight new manganese-oxalato compounds with 1,2-bis(4-pyridyl)ethylene (bpe): {(Hbpe)(2)[Mn(2)(μ-ox)(3)]·～0.8(C(2)H(5)OH)·～0.4(H(2)O)}(n) (1), {[Mn(μ-ox)(μ-bpe)]·xH(2)O}(n) (2), [Mn(2)(μ-ox)(2)(μ-bpe)(bpe)(2)](n) (3), [Mn(μ-ox)(μ-bpe)](n) (4a and 4b), and {[Mn(4)(μ-ox)(3)(μ-bpe)(4)(H(2)O)(4)]·(X)(2)·mY}(n) with X = NO(3)(-) (5a), Br(-) (5b), and ClO(4)(-) (5c) and Y = solvation molecules. The appropriate selection of the synthetic conditions allowed us to control the crystal structure and to design extended 2D and 3D frameworks. Compound 1 is obtained at acid pH values and its crystal structure consists of stacked [Mn(2)(μ-ox)(3)](2-) layers with cationic Hbpe(+) molecules intercalated among them. Compound 2 was obtained at basic pH values with a manganese/bpe ratio of 1:1, and the resulting 3D structure consists of an interpenetrating framework in which metal-oxalato chains are bridged by bpe ligands, leading to a microporous network that hosts a variable number of water molecules (between 0 and 1) depending on the synthetic conditions. Compound 3, synthesized with a manganese/bpe ratio of 1:3, shows a 2D framework in which linear metal-oxalato chains are joined by bis-monodentate 1,2-bis(4-pyridyl)ethylene ligands. The thermal treatment of compound 3 permits the release of one of the bpe molecules, giving rise to two new 2D crystalline phases of formula [Mn(μ-ox)(μ-bpe)](n) (4a and 4b) depending on the heating rate. The open structures of 5a-5c were synthesized in a medium with a high concentration of nitrate, perchlorate, or bromide salts (potassium or sodium as cations). These anions behave as templating agents directing the crystal growing toward a cationic porous network, in which the anions placed in the voids and channels of the structure present high mobility, as inferred from the ionic exchange experiments. Variable-temperature magnetic susceptibility measurements show an overall antiferromagnetic behavior for all compounds, which are discussed in detail.     

A series of manganese-carboxylate coordination polymers exhibiting diverse magnetic properties

The hydrothermal reactions of an asymmetrical 4-(4-carboxyphenylamino)-3,5-dinitrobenzoic acid (H2cpdba), MnCl2.4H2O, or together with 2,2'-bipyridine (2,2'-bpy) or 4,4'-bipyridine (4,4'-bpy) afford three novel molecule-based magnetic coordination polymers [Mn(cpdba)]n (1), ([Mn2(cpdba)2(2,2'-bpy)2(H2O)2].H2O)n (2) and ([Mn2(cpdba)2(4,4'-bpy)].2H2O)n (3). Compound 1 has a 3D acentric coordination network containing carboxylate-bridged 1D ladder-like manganese chains with spin-canted antiferromagnetism (J = -3.51 cm(-1) for the coupling along the ladder legs, and zJ' = 0.22 cm(-1) for coupling along the ladder rungs), whereas compounds 2 and 3 crystallize in the centrosymmetric space groups P1 and C2/c, respectively. 2 exhibits a 1D chain structure, which is extended into a 3D supramolecular network by pi-pi stacking interactions, while 3 features a quite complex 3D network built up from the cpdba(2-) and 4,4'-bpy spacers as well as the carboxylate-bridged Mn(II) chains. Both 2 and 3 show weak antiferromagnetic coupling interactions (J = -0.55 cm(-1) for 2), and a field-induced spin-flop magnetic transition can also be observed in 2 at ca. 3.2 T at 2 K.     

Halogen versus Hydrogen Bonding in Binary Cocrystals: Novel Conformation a Coformer with [2+2] Photoreactivity of Criss-Crossed C=C Bonds

A series of cocrystals involving the hydrogen- and halogen-bond donor coformers catechol ( cat ) and 1,2-diiodotetrafluorobenzene ( 1,2-di-I-tFb ), respectively, is reported. Each coformer forms a cocrystal with each of the three symmetric bipyridines trans-1,2-bis(n-pyridyl)ethylene ( n , n′ -bpe , where: n=n′=2, 3, 4). Four novel cocrystals ( cat ) ⋅ ( 3,3′-bpe ), 2( 1,2-di-I-tFb ) ⋅ ( 2,2′-bpe ), 2( 1,2-di-I-tFb ) ⋅ ( 3,3′-bpe ), and ( 1,2-di-I-tFb ) ⋅ ( 4,4′-bpe ) comprise components that assemble by either O−H⋅⋅⋅N hydrogen bonds ( cat ) or N⋅⋅⋅I halogen bonds ( 1,2-di-I-tFb ). In ( cat ) ⋅ ( 3,3′-bpe ), cat acts as a template to support an intermolecular [2+2] photocycloaddition of 3,3′-bpe . The reactivity occurs via a one-dimensional (1D) hydrogen-bonded tape with stacked and criss-crossed olefins that react stereoselectively and quantitatively to form rctt-tetrakis(3-pyridyl)cyclobutane ( 3,3′-tpcb ). The reactivity of the criss-crossed olefins is facilitated by a hitherto not reported cis-gauche conformation adopted by cat . The stereochemistry of 3,3′-tpcb is confirmed in the cocrystal 2( cat ) ⋅ ( 3,3′-tpcb ).     

Spectroscopic approach in the characterization of the copper(II) complexes of isatin-3,2'-quinolyl-hydrazones and their adducts

Copper(II) complexes of isatin-3,2'-quinolyl-hydrazones of the type [Cu(L)X] (where X=Cl(-), Br(-), NO(3)(-), CH(3)COO(-) and ClO(4)(-)] and their adducts Cu(L)X.2Y [where Y=pyridine or dioxane and X=Cl(-), Br(-), NO(3)(-) and ClO(4)(-)] have been synthesized under controlled experimental conditions and characterized by using the modern spectroscopic and physicochemical techniques viz. IR, electronic, EPR, elemental analysis, magnetic moment susceptibility measurements and molar conductance, etc. On the basis of spectral studies a four coordinated square planer geometry is assigned for Cu(L)X type complexes whereas the adducts (Cu(L)X.2Y were found to have a six coordinated octahedral geometry.     

Reversible Structural Transformations of Metal–Organic Frameworks as Artificial Switchable Catalysts for Dynamic Control of Selectively Cyanation Reaction

The synthesis of molecular-level artificial switchable catalysts, of which activity in different chemical processes can be switched by controlling different stimuli, has provided a new paradigm to perform mechanical tasks and measurable work. In this work, to obtain highly effective and regioselective artificial switchable catalysts, a hierarchical anion-pillared framework {(H₃O)[Cu(CPCDC)(4,4′-bpy)]}_n ( 1 ; H₃CPCDC=9-(4-carboxyphenyl)-9H-carbazole-3,6-dicarboxylic acid, 4,4′-bpy=4,4′-bipyridine), including free [H₃O]⁺ ions as guest molecules, was constructed. Upon dissolve–exchange–crystallization behavior, fascinating reversible structural transformations proceeded between anion framework 1 and neutral 2D stair-stepping framework {[Cu(CPCDC)(4,4′-bpe)]}_n ( 2 ; 4,4′-bpe=4,4′-vinylenedipyridine). Moreover, frameworks 1 and 2 can act as heterogeneous artificial switchable catalysts to selectively promote the direct cyanation reaction of terminal alkynes and azobisisobutyronitrile. The results indicated that 1 and 2 exhibited excellent selectivity to generate vinyl isobutyronitrile skeletons or propiolonitrile frameworks, respectively, as unique products. Furthermore, indicating paper, GC-MS, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analysis demonstrated that the reversible structural transformations endowed 1 and 2 with well-defined platforms to stabilize the isobutyronitrile and CN sources through the different catalytic pathways.     

Spectroscopic and physicochemical studies on nickel(II) complexes of isatin-3,2'-quinolyl-hydrazones and their adducts

Nickel(II) complexes of isatin-3,2'-quinolyl-hydrazones of the type [Ni(L)X] (where X=Cl-, Br-, NO3-, CH3COO- and ClO4-] and their adducts Ni(L)X.2Y [where Y=pyridine or dioxane and X=Cl-, Br-, NO3- and ClO4-] have been synthesized under controlled experimental conditions and characterized by using the modern spectroscopic and physicochemical techniques viz. mass, 1H NMR, IR, electronic, elemental analysis, magnetic moment susceptibility measurements and molar conductance, etc. On the basis of spectral studies a four coordinated tetrahedral geometry is assigned for Ni(L)X type complexes whereas the adducts (Ni(L)X.2Y) were found to have a six coordinated distorted octahedral geometry.     

Molybdenum carbonyl complexes of binucleating pyridine-based ligands

Reaction of [Mo(CO)₄(diene)] with 4,4′-bipyridine (44′B), trans-1,2-bis(2-pyridyl)ethene (2-bpe) and trans-1,2-bis(4-pyridyl)-ethene (4-bpe) gives polymeric [Mo(CO)₄(44′B)]_n, mononuclear cis-[Mo(CO)₄(2-bpe)₂] and binuclear [Mo(CO)₄(4-bpe)]₂ respectively. Reaction of the same ligands with [Mo(CO)₄(bpy)] (bpy is 2,2′-bipyridine) produces the bridged binuclear complexes [{Mo(CO)₃(bpy)}₂(44′B)] and [{Mo(CO)₃(bpy)}₂(4-bpe)]. Products are characterised by microanalysis and spectroscopy (IR, ¹H NMR, UV/vis). Reduction of [{Mo(CO)₃(bpy)}₂(44′B)] produces an anion in which the unpaired electron is localised on the chelating bpy ligand.     

Zipped-up chain-type coordination polymers: unsymmetrical amide-containing ligands inducing beta-sheet or helical structures. kazu-u@yamaguchi-u.ac.jp

The crystal structures of thirteen AgI coordination polymers involving py-CONH-(CH2)n-py (py=pyridine; n=0, 1) derivatives were determined by means of single-crystal X-ray analyses. All of the compounds form one-dimensional chains composed of AgI atoms and bridging ligands with formulas [[Ag(py-CONH-(CH2)n-py)][X]]n (X=PF6 -, ClO4 -, BF4 -, and NO3 - with solvent molecules). The unsymmetrical coordination environments around AgI atoms induce direction in the chains, that is, -[NH-(CH2)n-py-Ag-py-CO]-, which resembles the alignment of amino acid chains in proteins. In compounds [[Ag(4-pia)][X]]n (1 supersetX; 4-pia=N-(4-pyridyl)isonicotinamide; X=PF6 -, ClO4 -, BF4 -, and NO3 -), [[Ag(4-pmia)][X]]n (2 supersetX; 4-pmia=N-(pyridin-4-ylmethyl)isonicotinamide; X=PF6 -, ClO4 -H2O, and NO3 -H2O), and [[Ag(3-pmia)][X]]n (3 supersetX; 3-pmia=N-(pyridin-3-ylmethyl)isonicotinamide; X=PF6 -, ClO4 -, BF4 -, and NO3 -H2O), each chain is aligned parallel to neighboring chains, but adjacent chains run in the opposite direction. Particularly in [[Ag(3-pmia)][PF6]]n (3 supersetPF6 -), [[Ag(3-pmia)][ClO4]]n (3 supersetClO4 -), and [[Ag(3-pmia)][BF4]]n (3 supersetBF4 -), amide moieties of 3-pmia ligands are complementarily hydrogen bonded to amide moieties in neighboring chains, as in the beta-sheet motif in proteins. On the other hand, in [[Ag(4-pmna)][PF6]MeOH]n (4-pmna=N-(pyridin-4-ylmethyl)nicotinamide), all chains in the crystal form left-handed (4 a supersetPF6 -MeOH) and right-handed (4 b supersetPF6 -MeOH) helical structures with a helical pitch of 28 A. Heterogeneous anion exchanges proceed reversibly in 2, but not in 3, which provides information about the thermal stabilities of the crystals.     

Spectral studies on copper(II) complexes of biologically active glutathione

Copper(II) complexes of reduced glutathione (GSH) of general composition Na[Cu(L)(X)]*nH2O (where LH2=GSH; X=Cl-, NO3-, NCS-, CH3CO2-, HCO2-, ClO4- and n=0-4) have been prepared and characterized by elemental analysis, magnetic susceptibility measurements, IR spectroscopy, EPR spectroscopy and ligand-field spectroscopy. The EPR and ligand field spectra in the solid state suggest planar geometry for all the complexes.     

Synthesis,characterization and magnetic analysis of binuclear nickel(II) terephthalato complexes

Six new binuclear nickel (II) complexes have been synth-esized and characterized, namely: [Ni2(4X-TP-HA)(L)4](ClO4)2 [L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen) or 2,2-bipyridyl (bipy)], where 4X-TPHA is the tetrabromoterephthalate dianion (X = Br) or the tetraiodoterephthalate dianion (X = I). Based on i.r. spectra, elemental analyses and conductivity measurements, these complexes are proposed to have terephthalato-bridged structures containing two NiII ions, each in a distorted octahedral environment. The temperature dependences of the magnetic susceptibility for [Ni2(4Br-TPHA)(phen)4]- (ClO4)2·H2O (1) and [Ni2(4I-TPHA)(phen)4]-(ClO4)2·- 2H2O (4) were measured over the 4–300K range and the observed data indicate weak antiferromagnetic spin exchange interaction between the metal ions.     

Crystal structures and solution behaviors of dinuclear d(10)-metal complexes containing anions of N,N'-bis(pyrimidine-2-yl)formamidine

The salts of Zn(II), Cd(ii) and Hg(II) react instantaneously with Kpmf (pmf(-) = anion of N,N'-bis(pyrimidine-2-yl)formamidine, Hpmf) in THF, producing bimetallic complexes of the types [M(2)(pmf)(3)](X) (M = Zn(II), X = I(3)(-), ; M = Zn(II), X = NO(3)(-), ; M = Zn(II), X = ClO(4)(-), ; M = Cd(II), X = NO(3)(-), ; M = Cd(II), X = ClO(4)(-), ) and Hg(2)(pmf)(2)X(2) (X = Cl, ; Br, ; I, ). New tridentate and tetradentate coordination modes were observed for the pmf(-) ligands and their fluxional behaviors investigated by measuring variable-temperature (1)H NMR spectra. Complexes and , which possess only tetradentate coordination modes for the pmf(-) ligands in the solid state show larger free energy of activation (DeltaG(c)( not equal)) for the exchange than complexes and with tetradentate and/or tridentate coordination modes. Complexes and are the first dinuclear Zn(II) and Hg(II) complexes containing formamidinate ligands. Moreover, the separation between the two Hg(II) atoms are 3.4689(9), 3.4933(13) and 3.5320(10) A for complexes , respectively, similar to the sum of van der Waals radii of two Hg(II) atoms which is 3.50(7) A. All the complexes exhibit emissions and the nature of the anions hardly change the emission wavelengths of the complexes with the same metal centers. The emission bands may be tentatively assigned as intraligand (IL) pi-->pi* transitions.     

多重氢键自组装联萘酚和含氮化合物

作为相互识别的结果,(±)-2,2′-二羟基-1,1′-联萘酚可与4,4′,6,6′-四甲基-2,2′-联嘧啶、1,2-双(4-吡啶)乙烷、反式-1,2-双(4-吡啶)乙烯、4,4′-联吡啶-N,N′-双氧化物及双-2-吡啶基甲酮等多种含氮化合物分别形成外形良好的共晶化合物1,2,3,4及5.本文对5个共晶化合物的晶体...     

Quantitative analysis of intermolecular forces for hydrogen bond driven self-assembly of resorcinol and bis(pyridine) substituted ethylene cocrystals, before and after [2 + 2] dimerization

The long-range and dispersion corrected density functional theory (DFT + Disp), and Møller–Plesset second-order perturbation theory (MP2) were used for describing the intermolecular interactions between hydrogen bond driven self-assembly of 2(5-CN-res) … 2(4,4′-bpe) and 2(4,6-diCl-res) … 2(4,4′-bpe) cocrystals [where 5-CN-res = 5-cyanoresorcinol, 4,6-diCl-res = 4,6-dichlororesorcinol, and 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene], before and after [2 + 2] dimerization to 2(5-CN-res) … (4,4′-tpcb) and 2(4,6-diCl-res) … (4,4′-tpcb), respectively [where 4,4′-tpcb = 1,2,3,4-tetra(4-pyridyl)cyclobutane]. The nature and strength of intermolecular forces were studied using the absolutely localized molecular orbitals energy decomposition analysis, and the plot of reduced density gradient versus the electron density multiplied by the sign of the second Hessian eigenvalue [sign(λ₂)ρ]. The results show that the interaction of 2(4,4′-bpe) is basically dispersive nature, while all of the electrostatic, dispersion, polarization and charge-transfer interactions are largely contributed to the interaction energy of 2(4,4′-bpe) with 5-CN-res and 4,6-diCl-res molecules. The total interaction energy of complexes before dimerization is greater than that after dimerization. Since the contribution of polarization and charge-transfer interactions after dimerization are nearly unchanged, the main difference in the interaction energy of complexes is due to the weaker contribution of van der Waals and electrostatic forces in the products.     

Porous anionic, cationic, and neutral metal-carboxylate frameworks constructed from flexible tetrapodal ligands: syntheses, structures, ion-exchanges, and magnetic properties

A series of coordination polymers with anionic, cationic, and neutral metal-carboxylate frameworks have been synthesized by using a flexible tetrapodal ligand tetrakis[4-(carboxyphenyl)oxamethyl] methane acid (H(4)X). The reactions between divalent transition-metal ions and H(4)X ligands gave [M(3)X(2)]·[NH(2)(CH(3))(2)](2)·8DMA (M = Co (1), Mn (2), Cd(3)) which have anionic metal-carboxylate frameworks with NH(2)(CH(3))(2)(+) cations filled in channels. The reactions of trivalent metal ions Y(III), Dy(III), and In(III) with H(4)X ligands afforded cationic metal-carboxylate frameworks [M(3)X(2)·(NO(3))·(DMA)(2)·(H(2)O)]·5DMA·2H(2)O (M = Y(4), Dy(5)) and [In(2)X·(OH)(2)]·3DMA·6H(2)O (6) with the NO(3)(-) and OH(-) serving as counterions, respectively. Moreover, a neutral metal-carboxylate framework [Pb(2)X·(DMA)(2)]·2DMA (7) can also be isolated from reaction of Pb(II) and H(4)X ligands. The charged metal-carboxylate frameworks 1-5 have selectivity for specific counterions in the reaction system, and compounds 1 and 2 display ion-exchange behavior. Moreover, magnetic property measurements on compounds 1, 2, and 5 indicate that there exists weak antiferromagnetic interactions between magnetic centers in the three compounds.     

Spectral and magnetic studies on manganese(II), cobalt(II) and nickel(II) complexes with Schiff bases

Mn(II), Co(II) and Ni(II) complexes of 2-methylcyclohexanone thiosemicarbazone(MCHTSC L(1)) and 2-methylcyclohexanone-(4)N-methyl-3-thiosemicarbazone (MCHMTSC L(2)), general composition [M(L)(2)X(2)] (where M = Mn(II), Co(II), Ni(II), L = L(1) or L(2) and X = Cl(-), NO(3)(-), and [(1/2)SO(4)(2-)) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, UV-vis, IR, EPR, and mass spectral studies. Various physico-chemical techniques suggest an octahedral geometry for all the complexes.     

Subtle role of polyatomic anions in molecular construction: structures and properties of AgX bearing 2,4'-thiobis(pyridine) (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-))

Studies on the subtle effects and roles of polyatomic anions in the self-assembly of a series of AgX complexes with 2,4'-Py(2)S (X(-) = NO(3)(-), BF(4)(-), ClO(4)(-), PF(6)(-), CF(3)CO(2)(-), and CF(3)SO(3)(-); 2,4'-Py(2)S = 2,4'-thiobis(pyridine)) have been carried out. The formation of products appears to be primarily associated with a suitable combination of the skewed conformers of 2,4'-Py(2)S and a variety of coordination geometries of Ag(I) ions. The molecular construction via self-assembly is delicately dependent upon the nature of the anions. Coordinating anions afford the 1:1 adducts [Ag(2,4'-Py(2)S)X] (X(-) = NO(3)(-) and CF(3)CO(2)(-)), whereas noncoordinating anions form the 3:4 adducts [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Each structure seems to be constructed by competition between pi-pi interactions of 2,4'-Py(2)S spacers vs Ag.X interactions. For ClO(4)(-) and PF(6)(-), an anion-free network consisting of linear Ag(I) and trigonal Ag(I) in a 1:2 ratio has been obtained whereas, for the coordinating anions NO(3)(-) and CF(3)CO(2)(-), an anion-bridged helix sheet and an anion-bridged cyclic dimer chain, respectively, have been assembled. For a moderately coordinating anion, CF(3)SO(3)(-), the 3:4 adduct [Ag(3)(2,4'-Py(2)S)(4)](CF(3)SO(3))(3) has been obtained similarly to the noncoordinating anions, but its structure is a double strand via both face-to-face (pi-pi) stackings and Ag.Ag interactions, in contrast to the noncoordinating anions. The anion exchanges of [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = BF(4)(-), ClO(4)(-), and PF(6)(-)) with BF(4)(-), ClO(4)(-), and PF(6)(-) in aqueous media indicate that a [BF(4)(-)] analogue is isostructural with [Ag(3)(2,4'-Py(2)S)(4)]X(3) (X(-) = ClO(4)(-) and PF(6)(-)). Furthermore, the anion exchangeability for the noncoordinating anion compounds and the X-ray data for the coordinating anion compounds establish the coordinating order to be NO(3)(-) > CF(3)CO(2)(-) > CF(3)SO(3)(-) > PF(6)(-) > ClO(4)(-) > BF(4)(-).     

Isolation of a pentadentate ligand and stepwise synthesis, structures, and magnetic properties of a new family of homo- and heterotrinuclear complexes

A neutral pentadentate ligand, di(pyrazolecarbimido)amine (Hdcadpz), and its adduct with HClO4, [H2dcadpz]+[ClO4]-, were for the first time isolated from our previously reported [Cu3(dcadpz)2(Hpz)2(ClO4)2](ClO4)2.H2O by the use of (NH4)2S to remove the CuII ions and characterized by IR, EA, UV, NMR, MS, and X-ray crystallography. Reactions of copper(II) or nickel(II) nitrate with Hdcadpz in a 1:2 molar ratio generated two mononuclear precursors of [Cu(dcadpz)2] (1) and [Ni(dcadpz)2].2/3DMF (2). Furthermore, three new linear homo- and heterotrinuclear complexes of the same motif [M{M'(dcadpz)2}M] (M=CoII, NiII, M'=CuII, NiII), [{Co(pdm)}2{Cu(dcadpz)2}](NO3)4 (3), [{Ni(pdm)}2{Cu(dcadpz)2}](NO3)4 (4), and [{Ni(MeOH)(H2O)2}2{Ni(dcadpz)2}](NO3)4 (5), were synthesized from these two precursors (pdm=2,6-pyridinedimethanol) and characterized by X-ray crystallography. Magnetic studies show that the central Cu(dcadpz)2 motif is antiferromagnetically coupled with both the terminal Co(II) atoms via the dcadpz- ligand in 3 with a J value of -5.27 cm(-1) and ferromagnetically coupled with both the terminal Ni(II) atoms in 4 with a J value of 2.50 cm(-1), while 5 behaves only as a Curie paramagnet between 2 and 300 K due to the diamagnetic character of the central square-planar Ni(II) atom.