Mixed-ligand Coordination Research Articles

Self-assembly of three novel mixed-ligand coordination polymers: Formation of 2-D grids, 1-D chains and ladders and crystal band structure

Hydrothermal reaction of the carboxylate-based ligands with metal salts (or oxide) and 4,4′-bipyridine as a second linker, afforded three new coordination polymers, namely, [Co(PCPA) 2(4,4′-bpy)] n ( 1) with 2-D rectangle grids, Cu(PCPA) 2(4,4′-bpy)] n ( 2) with a linear chain, [Ag(PCPA)(PCPAH)(4,4′-bpy) · H 2O] n ( 3) with 1-D molecular ladder (4,4′-bpy = 4,4′-bipyridine; PCPA = p-chlorophenoxyacetate; PCPAH = p-chlorophenoxyacetic acid). It is noticeable that compound 3 is also a supramolecular framework built by coordination bonds, weak interactions between Ag ions, π–π stacking interactions and hydrogen-bonded interactions. The three compounds with different structure motifs have been characterized by elemental analyses, IR spectra, ultraviolet–visible diffuse reflection integral spectra, fluorescent spectra and single crystal X-ray diffraction analysis. Furthermore, the bonding properties of compound 3 were investigated in terms of the absorption spectrum, as well as the calculated band structures and density of states.

Mixed-Ligand Coordination Species: A Promising Approach for “Second-Generation” Drug Development

A series of crystalline mixed-ligand copper(II)−aspirinate coordination complexes have been synthesized, structurally characterized, and shown to exhibit a diverse range of pharmacologically relevant properties, such as bulk solubility, solubility ratio (Swo/Sow), and partition coefficient.

Synthesis and crystal and molecular structure of the mixed-ligand coordination compound ZnPhen(n-C4H9OCS2)2

A mixed-ligand complex ZnPhen(n-BuOCS2)2 has been synthesized. The structure of the compound was solved by X-ray diffractometry (X8 APEX diffractometer, MoK α radiation, 4254 F hkl , R = 0.0448). Triclinic crystals with the parameters a = 9.4464(3) A, b = 11.0279(4) A, c = 13.6528(6) A;α = 106.940(1)°, β = 98.382(1)°, γ = 106.347(1)°; V = 1264.72(8) A3; Z = 2, space group 1. P1¯. The structure consists of discrete mononuclear molecules. The polyhedron of the Zn atom is a trigonal bipyramid N2S3 formed by coordination of the N atoms of the bidentate Phen molecules and the sulfur atoms of the monodentate and cyclic bidentate xanthate ligands. Dimer assemblies are formed in the structure due to π-π interactions of Phen molecules.

Tetraphenylarsonium diiododiisothiocyanatocobaltate(II)

The use of mixed-ligand (iodide and thio­cyanate) coordination with cobalt has led to the crystallization of the title compound, (C24H20As)2[CoI2(NCS)2]. The structure comprises tetra­hedral (C6H5)4As+ cations and tetra­hedral [CoI2(NCS)2]2− anions, the latter lying on crystallographic twofold axes.

Crystal and molecular structures of ZnPhen(C2H5OCS2)2 and Zn(2,2′-Bipy)(n-C4H9OCS2)2 mixed-ligand coordination compounds

ZnPhen(EtOCS2)2 (I) and Zn(2,2′-Bipy)(n-BuOCS2)2 (II) mixed-ligand complexes have been synthesized. The structures were solved from X-ray diffraction data (CAD-4 and X8-APEX diffractometers, MoKα radiation, 1879 and 3637 Fhkl, R = 0.0374 and 0.0315). Crystals I are monoclinic with parameters a = 11.678(3) A, b = 19.215(3) A, c = 9.655(1) A; β = 101.23(1)°; V = 2125.0(7) A3; Z = 4, space group P21/c; crystals II are triclinic with parameters a = 8.7875(3) A, b = 11.833(1) A, c = 13.3454(6) A; α = 112.154(2)°, β = 108.503(1)°, γ = 92.787(2)°; V = 1196.2(1) A3; Z = 2, space group 1 \(P\bar 1\). The structures are composed of discrete mononuclear molecules. The polyhedra of the Zn atoms are distorted trigonal bipyramids N2S3 formed by coordination of the N atoms of Phen or 2,2′-Bipy molecules and sulfur atoms of the monodentate and cyclic bidentate xanthogenate ligand. In structures I and II, dimer assemblies are formed by π-π interactions of Phen or 2,2′-Bipy molecules.

Tetraphenylarsonium diisothiocyanatodibromonickelate(II)

Use of mixed-ligand (bromide and thiocyanate ions) coordination with nickel has led to the crystallization of the title compound, (C24H20As)2[Ni(NCS)2Br2]. X-ray crystal structure analysis reveals that the asymmetric unit contains one (C6H5)4As+ cation and one half [Ni(NCS)2Br2]2− anion, the latter lying on a crystallographic twofold axis.

Design and syntheses of 1D and 2D coordination polymers resulting from flexible building blocks

Two new mixed-ligand coordination polymers, [Cd(bpp)(cpg) 2 (H 2O) 2] ( 1), [Zn(bpp)(cpg)]·H 2O ( 2), have been synthesized. The central cadmium and zinc ions are hexa-coordinate and tetra-coordinate, respectively. X-ray analyses show that different coordination propensity of cadmium and zinc ions leads to different structures, 1D bilayer ladder ( 1) and 2D rectangle grid network ( 2), in which cpg and bpp ligand exist as their stable conformation, respectively (TT-form and TG-form).

Dimeric ensembles in the crystal structures of mixed-ligand coordination compounds ML(i-Bu2PS2)2 (M = Zn, Cd, Mn, Co, Ni; L = Phen, 2,2′-Bipy)

Single crystals of a mononuclear mixed-ligand complex [Mn(Phen)(i-Bu2PS2)2] were grown and used for X-ray diffraction structural study of the material (diffractometer CAD-4, MoK α -radiation, 1205 F hkl , R = 0.0351). The crystals are monoclinic: a = 15.602(2) A, b = 20.914(3) A, c = 11.419(2) A; β = 111.36(1)°, V = 3470.1(9) A3, Z = 4, ρ(calc) = 1.251 g/cm3, space group P21/c. Coordination polyhedron of Mn is a distorted octahedron N2S4. Molecular and crystal structures of mixed-ligand coordination compounds ML(i-Bu2PS2)2 (M= Zn, Cd, Mn, Co, Ni; L = Phen, 2,2′-Bipy) are considered on the basis of XRD data (automated diffractometers CAD-4 and X8-APEX). The analysis of intermolecular distances in the structures of ten mixed-ligand coordination compounds revealed in nine of them the presence of short contacts made by carbon atoms of the N-heterocycles. These contacts correspond to π-π interactions of Phen or 2,2′-Bipy molecules of two neighboring complexes giving rise to dimeric molecular ensembles.

Microporous Pillared Paddle-Wheel Frameworks Based on Mixed-Ligand Coordination of Zinc Ions

The reaction of Zn(NO3)2 x 6H2O, various dicarboxylic acids, and either 4,4'-bipyridine or N,N'-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas.

Terminal ligand influence on the electronic structure and intrinsic redox properties of the [Fe4S4]2+ cubane clusters.

We used photoelectron spectroscopy (PES) to study how the terminal ligands influence the electronic structure and redox properties of the [4Fe-4S] cubane in several series of ligand-substituted analogue complexes: [Fe(4)S(4)Cl(4-x)(CN)(x)](2-), [Fe(4)S(4)Cl(4-x)(SCN)(x)](2-), [Fe(4)S(4)Cl(4-x)(OAc)(x)](2-), [Fe(4)S(4)(SC(2)H(5))(4-x)(OPr)(x)](2-), and [Fe(4)S(4)(SC(2)H(5))(4-x)Cl(x)](2-) (x = 0-4). All the ligand-substituted complexes gave similar PES spectral features as the parents, suggesting that the mixed-ligand coordination does not perturb the electronic structure of the cubane core significantly. The terminal ligands, however, have profound effects on the electron binding energies of the cubane and induce significant shifts of the PES spectra, increasing in the order SC(2)H(5)(-) --> Cl(-) --> OAc(-)/OPr(-) --> CN(-) --> SCN(-). A linear relationship between the electron binding energies and the substitution number x was observed for each series, indicating that each ligand contributes independently and additively to the total binding energy. The electron binding energies of the gaseous complexes represent their intrinsic oxidation energies; the observed linear dependence on x is consistent with similar observations on the redox potentials of mixed-ligand cubane complexes in solution. The current study reveals the electrostatic nature of the interaction between the [4Fe-4S] cubane core and its coordination environment and provides further evidence for the electronic and structural stability of the cubane core and its robustness as a structural and functional unit in Fe-S proteins.

New types of the flexible self-assembled metal–organic coordination polymers constructed by aliphatic dicarboxylates and rigid bidentate nitrogen ligands

The reaction of metal ions, flexible aliphatic dicarboxylates and rigid bidentate linear ligands under mild conditions in water afford four novel metal-organic coordination polymers, [Cd(mu-mal)(mu-pyz)(0.5)(H(2)O)](n) 1 (mal = malonate dianion, pyz = pyrazine), [Cd(2)(mu-suc)(2)(mu-pyz)(H(2)O)(2)](n) 2 (suc = succinate dianion), and ([M(mu-bipy)(H(2)O)4][suc].4H(2)O)(n)(M = Co, 3, M = Zn, 4, bipy = 4,4'-bipyridine). The molecular structures of 1-4 have been established by single-crystal X-ray crystallography. 1 is a 3D network being composed of layers of octahedrally coordinated Cd atoms bridged by malonate anions in syn-anti configurations within the layers and pyz molecules between layers. Unlike that in 1, each Cd atom in 2 displays uncommon pentagonal-bipyramidal geometry to form 2D infinite grid sheets with square grid dimensions of ca. 7.936 x 7.936 [Angstrom]. Both 3 and 4 exhibit 1D linear -M-bipy-M-bipy- chain polymers, and these chains were packed as ...ABCABC... layered structures. The bridging succinate ligands in 2 adopt the syn-anti mode with a torsion angle of 60.8(7) degrees, while the solvated succinate ligands in 3 and 4 adopt the anti-anti mode with a torsion angle of 180.0 degrees. To our knowledge, compound 2 represents the first example of flexible self-assembled succinate-pyrazine mixed bridging ligand coordination network. 3 and 4 are the first two cases of succinate-bipy polymers with non-coordinated succinate. The magnetic behavior for 3 was studied in the temperature range of 5-300 K. The result indicates the occurrence of a weak antiferromagnetic coupling between the cobalt(II) ions.

In-air structural transformation observed from the synthesis of a new mixed-ligand coordination polymer

A new mixed-ligand coordination polymer, {[Cu(BDC)(Phen)(H 2O)] · (H 2O)(DMF)} n 1 (BDC = 1,4-benzenedicarboxylate; Phen = 1,10-phenanthroline) has been synthesized and characterized. It was found that the complex 1, crystallized in orthorhombic crystal system, was transformed into a more stable compound due to the evaporation of inclusion solvents in air, {[Cu(BDC)(Phen)(H 2O)] 2, and the complex 2 was characterized in triclinic crystal system. Complex 1: space group Pnma with unit cell dimensions a=23.378(2), b=12.830(1) and c=6.984(1) Å, Z=4. Complex 2: space group P 1 ̄ with unit cell dimensions a=9.004(1), b=10.527(1) and c=10.577(1) Å, α=114.779(1), β=92.246(1), γ=114.746(1), Z=2.

Synthesis and characterization of the mixed ligand coordination polymer CPO-5

The synthesis and crystal structures of a novel coordination polymer and its high-temperature variant are described. The as-synthesized material (CPO-5-as), of composition Zn(4,4′-bipyridine)(4,4′-biphenyldicarboxylate)·3H 2O, crystallizes in the triclinic space group P-1 (No. 2) with a=11.0197(2), b=14.2975(3), c=7.6586(1) Å, α=95.9760(9)°, β=108.026(1)°, γ=91.373(1)° and V=1139.16(4) Å 3. CPO-5-as is composed of tetrahedral zinc centers that are connected by the organic linkers to give five independent, interpenetrating diamond networks. In the structure, there is additional space for channels that are filled with three water molecules. These water molecules can be removed, leading to an anhydrous variant at 130 oC. CPO-5-130, of composition Zn(4,4′-bipyridine)(4,4′-biphenyldicarboxylate), crystallizes in the triclinic space group P-1 (No. 2) with a=11.1844(6), b=14.0497(7), c=7.7198(3) Å, α=96.917(2)°, β=109.527(2)°, γ=89.115(3)° and V=1134.6(1) Å 3. The structure of the five interpenetrating networks is virtually unchanged after the dehydration resulting in CPO-5-130 being a porous structure with an estimated free volume of 19.8%.

A mixed-ligand coordination polymer from the in situ, Cu(I)-mediated isomerization of bis(4-pyridyl)ethylene.

Reaction of [Cu(PPh(3))(2)(MeCN)(2)]PF(6) and trans-1,2-bis(4-pyridyl)ethylene (bpe) results in the trans-cis isomerization of the bpe and subsequent formation of a mixed-isomer linear coordination polymer over the course of several days or weeks depending on solvent. The one unique copper atom in the structure is coordinated to two bridging cis-bpe ligands, one bridging trans-bpe ligand, and one terminal triphenylphoshine ligand to create [Cu(trans-bpe)(0.5)(cis-bpe)(PPh(3))](+)( infinity ) zigzag chains. The reaction requires both visible light and Cu(I), and the crystallization of this particular coordination polymer is insensitive to the ratio of trans:cis isomers in solution, occurring both from trans-rich and cis-rich solutions.

Spin distribution in copper(i) phosphine complexes of verdazyl radicals

Copper(I) forms mixed ligand coordination compounds with the stable, paramagnetic bipyridine analogue, 1,5-dimethyl-3-(2-pyridyl)-6-oxoverdazyl (pyvd) and a variety of monodentate and bidentate phosphine ligands. These compounds were characterized in solution by titration, UV-vis spectra, ESR spectra and electrospray mass spectrometry. Coordination of the phosphine gives a metal–ligand charge transfer transition in the UV-vis that is red shifted by more electron donating phosphines. ESR indicates that spin density on copper increases, both with strongly electron donating phosphines and with weakly basic phosphite ligands. This can be explained by the presence of two different orbital interactions: with more donating phosphines the interaction is predominantly through the filled copper(I) d-orbitals, but with weakly donating phosphite ligands the interaction is through an empty copper(I) p-orbital. The differing spin transfer mechanisms may have implications in the design of molecular magnetic systems.

Mixed-Ligand Coordination Compounds CdL{(i-C4H9)2PS2}2(L = Phen, 2,2"-Bipy, and 4,4"-Bipy): Synthesis, Structure, and Thermal Properties. Polymeric Structure of [Cd(4,4"-Bipy){(i-C4H9)2PS2}2

Volatile mixed-ligand compounds of Cd(i-Bu2PS2)2with Phen, 2,2"-Bipy, and 4,4"-Bipy were synthesized. Their single crystals were grown. X-ray diffraction data (a CAD4 diffractometer, MoK αradiation, 2140 F hkl, R=0.0251) were used to determine the structure of [Cd(4,4"-Bipy)(i-Bu2PS2)2]. The crystals are mono-clinic: a= 14.678(3) A, b= 11.866(2) A, c= 19.655(4) A, β = 102.17(3)°, V= 3346(1) A3, Z= 4, ρcalcd= 1.364 g/cm3, space group C2/c. The structure is built from linear polymeric chains arranged along the [010] direction. The coordination polyhedron of the Cd atom is a distorted octahedron (4S + 2N). The thermal properties of these compounds, studied both in air and in vacuo, allow one to use them for preparing CdS films by chemical precipitation from the gas phase.

Crystal chemistry of mixed-ligand coordination compounds with stable nitroxide radicals

This review discusses crystal chemical structure of mixed-ligand coordination compounds with stable nitroxide radicals obtained from β-diketonates, carboxylates, and metal halides. We analyze the coordination environment of metal atoms and the geometric characteristics of nitroxide radicals. The review covers publications up to January 1993.

Synthesis and study of mixed ligand monomer Cu(I) compounds with CuAs bonds. Crystal and molecular structure of bis(triphenylarsine)-(2-thioxohexamethyleneimine)copper(I) bromide

A new series of mixed ligand coordination compounds with CuAs bonds is synthesized by the reaction of Cu(AsPh 3) 3X, where XCl, Br, or [Cu(AsPh 3)I] 4 with 2-thioxohexamethyleneimine (ω-thiocaprolactam, tclH) in acetone or by the addition of triphenylarsine to Cu(tclH) 2X in methanol/chloroform. The products of both reactions are formulated as Cu(tclH)(AsPh 3) 2X, on the basis of their elemental analyses, IR, 1H NMR and UV-Vis spectral data. The crystal structure of the bromo compound is reported and discussed with respect to that of Cu(tclH) 2(AsPh 3)Br. The compound crystallizes in the monoclinic space group C2/ c, with a=41.981(8), b=9.961(2), c=19.087(2) Å, β=101.09(1)°, 8 discrete molecules being present in the unit cell. The copper environment is a distorted tetrahedron, with two inequal CuAs bonds, which are 2.411(2) and 2.372(2) Å, respectively. The CuBr and CuS bond lengths are equal to 2.456(3) and 2.313(4) Å, respectively, while the bond angles around copper vary from 104.4(0)° for As1CuS to 116.1(1)° for As1CuAs2.

Spectral and thermal characterization of mixed-ligand coordination complexes of Fe(II) and Fe(III) with 2-furan thiocarboxyhydrazide as primary and picolinic/dipicolinic acid as co-ligand

Spectral and thermal characterization of mixed-ligand coordination complexes of Fe(II) and Fe(III) with 2-furan thiocarboxyhydrazide as primary and picolinic/dipicolinic acid as co-ligand

Structural and thermal studies on mixed ligand co-ordination compounds of Pd(II), Rh(III) and Pt(II) with 3-(dimethyl-aminomethyl)indole and salicylaldoxime

N-(ethyl, m-tolyl)dithiocarbomato complexes of Rh(III), Pd(II) and Pt(II) have been prepared and characterized [1]. A thermogravimetric study of these compounds under nitrogen has also been carried out. Teotia et al. [2] studied the reaction of Pd(II) and Pt(II) with picolinic acid hydrazide, o-hydroxyacetophenone picolinoylhydrazone and o-hydroxy- acetophenone isonicotinoylhydrazone but the thermal behaviour of the isolated compounds has not been studied. A perusal of the literature reveals that no work seems to have been done on the co-ordination compounds of Pd(II), Rh(III) and Pt(II) with 3-(dimethyl-aminomethyl) indole and salicylaldoxime. In the present note, we report on the preparation of these compounds, determine their structure, and investigate their thermal behaviour.