Linear Bidentate Ligand Research Articles

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl2 Complexes with Rare Eight-Membered Chelate Rings.

NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Me ndpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6'-positions ( n = 2) or 3,3',5,5'-positions ( n = 4) of the pyridyl rings. The N(SO2R)3,3',5,5'-Me4dpa ligands are coordinated in a bidentate fashion in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO2R)6,6'-Me2dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [ trans-Pt(DMSO)Cl2]2( N(SO2R)6,6'-Me2dpa). The monodentate instead of bidentate N(SO2R)6,6'-Me2dpa coordination is attributed to 6,6'-Me steric bulk. These binuclear complexes are indefinitely stable in DMF- d7, but in DMSO- d6 the N(SO2R)6,6'-Me2dpa ligands dissociate completely. In DMSO- d6, the bidentate ligands in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes also dissociate, but incompletely; these complexes provide rare examples of association-dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl2 complexes, the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes undergo monosolvolysis in DMSO- d6 to form the [Pt( N(SO2R)3,3',5,5'-Me4dpa)(DMSO- d6)Cl]+ cations. However, unlike typical cis-PtLCl2 complexes, the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes are well positioned to form strong Pt-N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes arise from steric consequences imposed by the -CH2-N(SO2R)-CH2- chain in the eight-membered chelate ring.

Copper inorganic-organic hybrid coordination compound as a novel L-cysteine electrochemical sensor: Synthesis, characterization, spectroscopy and crystal structure

Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2] ⋅2H2O, where pydc = pyridine-2,6-dicarboxylic acid (dipicolinic acid) and pz = pyrazine has been synthesized and characterized by elemental analysis, spectra (IR, UV-Vis), thermal (TG/DTG) analysis, magnetic measurements and single crystal X-ray diffraction. In the dimeric structure, the planar tridentate pyridine-2,6-dicarboxylic acid dianion coordinates to a Cu(II) ion in a meridional fashion and defines the basal plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. The axial positions of each Cu(II) complex are occupied by one water molecule to form a distorted square pyramidal geometry. The complicated hydrogen bonding network accompanied with C–O ⋯π and C–H ⋯π stacking interactions assemble the crystal structure of 1 into a fascinating supramolecular architecture. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] (Cu-PDAP) on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) is described. Oxidation of cysteine on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the Cu-PDAP/CNTs film displays excellent electrochemical catalytic activities towards L-cysteine oxidation. Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2].2H2O, has been synthesized and characterized by elemental analysis, spectral (IR, UV-Vis), thermal (TG/DTG) analysis as well as single crystal X-ray diffraction. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) was described and oxidation of cysteine on the surface of modified electrode was investigated.

Enhancing the photovoltaic performance of quinoxalino[2,3-b′]porphyrinatozinc-based donor–acceptor copolymers by using 4,4′-bipyridine as a linear bidentate ligand additive

A strategy using Bipy as a linear bidentate ligand additive to significantly improve the photovoltaic performance of metalloporphyrin-based polymers is demonstrated.

Synthesis, structure, solution and DFT studies of a pyrazine-bridged binuclear Cu(II) complex: On the importance of noncovalent interactions in the formation of crystalline network

A pyrazine-bridged binuclear Cu(II) complexes with formulae of [Cu2(chel)2(pyz)(H2O)4], (1, pyz=pyrazine, H2chel=chelidamic acid), has been synthesized and characterized by elemental analyses, IR spectroscopy and solution studies. The crystal structure of the binuclear Cu(II) complex has been determined by X-ray single-crystal diffraction technique. Both copper(II) metal centers are bridged by pyrazine. The coordination environment around each copper(II) atom can be described as a distorted octahedral geometry. The axial positions of each Cu(II) complex are occupied by two water molecules and equatorial positions are occupied by a tridentate chelidamic acid dianion and a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. Hydrogen bonding and CO⋯π interactions link the binuclear Cu(II) complex generating the 3D infinite network. These assemblies are described and analyzed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. The protonation constants of pyrazine and chelidamic acid as the building blocks of the proton transfer systems (H2chel-pyz) and their corresponding stability constants were determined by potentiometric studies. The stoichiometry and stability constants of H2chel-pyz complex with Cu2+ was investigated by potentiometric technique in aqueous solution. The results from solution studies were compared with the solid state data, in details.

Two Unprecedented Entangled Metal–Olsalazine Complexes with Coexistence of 2D → 3D Polycatenation and meso‐Helix

AbstractRational self‐assembly of the anti‐inflammatory drug olsalazine (H4osa) with a cobalt salt in the presence of linear bidentate ligands yields two novel metal–drug complexes[Co(H2osa)(bpp)] (1) and [Co2(osa)(bpy)2(H2O)4] (2) [bpp = 1,3‐bis(4‐pyridyl)propane, bpy = 4,4′‐bipyridine]. Their structures were determined by single‐crystal X‐ray diffraction and further characterized by elemental analysis, IR spectroscopy, X‐ray powder diffraction, and thermogravimetric analysis (TGA). Compound 1 displays a new 2D → 3D parallel polycatenation of undulating (4,4) layers, whereas 2 exhibits an unusual 2D → 3D inclined polycatenation of (6,3) layers. To the best of our knowledge, they represent the first examples of metal–drug complexes that have both polycatenane and meso‐helix characteristics. The magnetic properties of 1 and 2 have been studied by measuring their magnetic susceptibility in the temperature range of 2–300 K.

Catena-Poly[[dichloridocopper(II)]-μ-4,4′-bis(benzimidazol-1-yl)biphenyl

In the title compound, [CuCl2(C26H18N4)]n, the Cu(II) ion is four-coordinated by two N atoms from two 4,4′-bis­(benzo­imidazol-1-yl)biphenyl ligands and two chloride anions, in a slightly distorted tetra­hedral environment. The biphenyl ligand acts as a linear bidentate ligand, connecting the metal atoms into an infinite chain parallel to [101]. In the biphenyl ligand, the two benzene rings make a dihedral angle of 33.19 (7)°.

Preparation, crystal structure and magnetic properties of Ni 2(dpa) 2(pyz)(H 2O) 4

A Ni(II)-based dimer structure, Ni 2(dpa) 2(pyz)(H 2O) 4 (dpa = 2,6-pyridine dicarboxylic acid dianion, pyz: pyrazine), has been prepared using hydrothermal synthesis and the solid-state magnetic properties have been evaluated. In the dimeric structure, the planar tridentate 2,6-pyridine dicarboxylic acid dianion coordinates to a Ni(II) ion in a meridional fashion and defines the equatorial plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Ni(II) complexes to form a dimer. The axial positions of each Ni(II) complex are occupied by two water molecules to form a distorted octahedral geometry. Susceptibility and magnetization measurements show that both intra-dimer and inter-dimer exchange interactions are weakly antiferromagnetic. The fitting of the magnetic data also indicates the existence of a large axial zero-field splitting term that contributes to the small magnetization even under high fields.

A 4-connected 3D porous coordination polymer with a binodal 6284 net built on tetrahedral quadridentate and bidentate linkers

An unprecedented 4-connected metal–organic framework [Zn2(tpom)(bdc)2]·2H2O (tpom = tetrakis(4-pyridyloxymethylene)methane, bdc = benzene-1,4-dicarboxylic acid) with a binodal 6284 net has been solvothermally synthesized from the assembly of a semirigid tetrahedral ligand (tpom) and a rigid linear bidentate ligand (bdc). The network of 1 is constructed by tetrahedrally connected tpom ligands and metal sites, in which 1D chains [Zn(bdc)]n interweave 2D diamondlike sheets [Zn2(tpom)]n into a 3D porous framework with a binodal 6284 net. 1 has a relatively high thermal stability and exhibits permanent porosity.

A 3D Metal-Organic Framework with CdSO4-type Topology Through Assembly of Mixed Ligands

Rational self-assembly of a long 3,3′,4,4′-benzophenonetetracarboxylate (bptc) ligand and metal salt in the presence of linear bidentate ligand yields a novel polymer with CdSO4-type topology. An interesting feature of the complex is that the bridged water molecule weakly coordinates to the Ni cation, forming an infinite metal–aqua chain as the fundamental unit. Furthermore, the metal–aqua chains are pillared by 1,2-bis(4-pyridy)ethene (bpe) ligands to extend a 3D rhombic framework.

A novel self-penetrating metal–organic open framework containing unusual triple-stranded molecular braid and septuple helices

Self-assembly of a long V-shaped 4,4′-oxydiphthalate (odpa) ligand and copper salt in the presence of a linear bidentate ligand affords a unique self-penetrating metal–organic open framework [Cu 2(odpa)(bpy) 2] ( 1) (bpy = 4,4′-bipyridine), exhibiting an unprecedented binodal four-connected (6 4.8 2) 2(6 2.8 4) topology. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by elemental analyses, IR spectrum, X-ray powder diffraction, and TG analysis. Compound 1 is a novel three-dimensional (3D) guest-free porous framework containing molecular braids and septuple helices, which are particularly rare in metal–organic coordination polymers.

Exceptional Self-Penetrating Networks Containing Unprecedented Quintuple-Stranded Molecular Braid, 9-Fold Meso Helices, and 17-Fold Interwoven Helices

Self-assembly of long V-shaped ligands and d10 metal salts in the presence of a linear bidentate ligand affords two unprecedented self-penetrating coordination networks {[Zn4(bptc)2(bpy)4].(C5H3N).4H2O}n (1) and {[Cd2(sdba)2(bpy)(H2O)2].2H2O}n (2) (bptc = 3,3',4,4'-benzophenonetetracarboxylate, sdba = 4,4'-sulfonyldibenzoate, bpy = 4,4'-bipyridine). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, X-ray powder diffraction, and TG analyses. 1 adopts a novel 3D framework containing three types of molecular braids, among which the quintuple-stranded molecular braid represents the highest-stranded molecular braid presently known for entangled systems. 2 is an uncommon self-penetrating 2D network containing pseudo-Borromean links and double-stranded helices. More interestingly, when the strong hydrogen bonds between layers are taken into account, the resulting net of 2 becomes an eight-connected 3D self-penetrating network with an unprecedented (421.67) topology, which represents the highest connected topology presently known in self-penetrating systems. Furthermore, the photoluminescent properties of 1 and 2 were studied.

A Bridge between Pillared‐Layer and Helical Structures: A Series of Three‐Dimensional Pillared Coordination Polymers with Multiform Helical Chains

Rational self-assembly of a long V-shaped 3,3',4,4'-benzophenonetetracarboxylate (bptc) ligand and metal salts in the presence of linear bidentate ligand yield a series of novel pillared helical-layer complexes, namely, [Cu2(bptc)(bpy)2] (1), [M3(Hbptc)2(bpy)3(H2O)4].2 H2O (M = Fe(2) and Ni(3)), [Co2(bptc)(bpy)(H2O)].0.5 bpy (4), [Cd2(bptc)(bpy)(H2O)2].H2O (5), [Mn2(bptc)(bpy)1.5(H2O)3] (6) and [M2(bptc)(bpy)0.5(H2O)5].0.5 bpy (M = Mn(7), Mg(8) and Co(9), bpy=4,4'-bipyridine). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric (TG) analyses. The structure of 1 consists of two types of chiral layers, one left-handed and the other right-handed, which are connected by bpy pillars to generate a novel 3D open framework featuring four distinct helical chains. Compounds 2 and 3 are isostructural and feature 3D structures formed from the interconnection of arm-shaped helical layers with bpy pillars. Compound 4 is a pillared helical double-layer complex containing four different types of helices, among which the nine-fold interwoven helices constructed from triple-stranded helical motifs are unprecedented. Compound 5 exhibits a novel 3D covalent framework which features nanosized tubular channels. These channels are built from helical layers pillared by bptc ligands. The structure of 6 is constructed from {Mn(bptc)(H2O)}n2n- layers, which consist of left- and right-handed helical chains, pillared by [Mn2(bpy)3(H2O)4]4+ complexes into a 3D framework. To the best of our knowledge, compounds 1-6 are the first examples of pillared helical-layer coordination polymers. Compounds 7-9 are isostructural and exhibit interesting 2D helical double-layer structures, which are constructed from {M(bptc)(H2O)2}n2n- ribbons cross-linked by [M2(bpy)(H2O)6]4+ complexes. Furthermore, the 3D supramolecular structures of 7-9 are similar to the 3D structure of 6, and the 2D structure of 7 can be transformed into the 3D structure of 6 at higher reaction temperature. By inspection of the structures of 1-9, it is believed that the V-shaped bptc ligand and V-shaped phthalic group of the bptc ligand are important for the formation of the helical structures. The magnetic behavior of compounds 1, 2, 4, 6, and 9 was studied and indicated the existence of antiferromagnetic interactions. Moreover, compound 5 shows intense photoluminescence at room temperature.

Cooperative Self-Assembly of Double-Strand Conjugated Porphyrin Ladders

A series of conjugated zinc porphyrin oligomers, from the dimer through to the hexamer, form stable ladder complexes with linear bidentate ligands such as 1,4-diazabicyclo[2.2.2]octane (DABCO) and 4,4‘-bipyridyl (Bipy). The 1H NMR spectra of these ladders confirm their structures and show how they fray and dissociate in the presence of excess ligand. The thermodynamics of these equilibria were elucidated by spectrophotometric titration, using multivariate global factor analysis, in two different solvents (chloroform and toluene). Ladder formation and dissociation exhibit many indications of positive cooperativity, including all-or-nothing two-state assembly, sigmoidal isotherms, large Hill coefficients, and narcissistic self-sorting. Ladder formation increases the planarity and conjugation, resulting in a reduction in the gap between the highest occupied and lowest unoccupied molecular orbitals.

An improved preparation of 4-ethynylpyridine and its application to the synthesis of linear bipyridyl ligands

A convenient synthesis of 4-ethynylpyridine, 5, starting from 4-vinylpyridine has been developed. Compound 5 reacts readily with pyridyl- and aryl-iodides to give the linear bidentate ligands 7, 9, and 11 in excellent yields.

Interwoven two- and three-dimensional coordination polymers through self-assembly of Cu I cations with linear bidentate ligands

The synthesis and single crystal X-ray structures are reported of two interwoven cationic frameworks that are based upon tetrahedral and trigonal CuI ions; the resulting architectures are diamondoid, [CuI(bipy)2(PF6)]∞(bipy = 4,4′-bipyridyl)1, and honeycomb, [CuI)2(pz)3(SiF6)]∞(pz = pyrazine)2, respectively.

Linear Chain Compounds of Molybdenum(II) Acetate Dimer Linked by Linear-bidentate Ligands, Pyrazine, 4,4′-Bipyridine, and 1,4-Diazabicyclo[2.2.2]octane

Abstract Linear chain compounds, [Mo2(O2CCH3)4·L]n (L = pyrazine, 4,4′-bipyridine, 1,4-diazabicyclo[2.2.2]octane) have been prepared and characterized. The linear chain structure of alternating MO2(O2CCH3)4 units and bridging ligands L was confirmed by an X-ray structural analysis of the bpy complex.