Auxiliary Co-ligands Research Articles

The use of C1 symmetry imidazole-carboxylate building block and auxiliary acetate co-ligand for assembly of a 2D wave-like zinc(II) coordination polymer: experimental and theoretical study

We report the synthesis and characterization of a two-dimensional Zn(II) coordination polymer employing a ligand with a biphenyl core containing imidazole and carboxylate groups in the presence of acetate moieties as bridging molecules. The obtained [ZnLAc]n was structurally characterized via X-ray, FTIR, TGA, PXRD, SEM and EDX analyses. Computer-aided calculations based on density functional theory (DFT) were employed to assess the optimal conformational geometries of both the starting ligand and the Zn(II) complex. Computational results were compared with the experimental data, disclosing a reasonable agreement. Comparisons between the single-crystal structures and the calculated optimized geometries of the molecular entities are discussed. In addition, the time-dependent DFT method (TD-DFT) was applied to assess the first excited state of the ligand and complex.

Construction of Designated Heptanuclear Metal 8-hydroxyquinolates with Different Ions and Auxiliary Coligands

The series of metal 8-hydroxyquinolates {[Ni7 (μ2-L1)6(μ3-L1)2(OAc)2(μ7-L2)(OCH3)]·CH3OH·CH3CN} (1), {[Ni7(μ2-L1)6(μ3-L1)3(SCN)2(μ7-L2)(CH3CN)]·(CH3OH)2·CH3CN} (2), [Ni5Dy2(μ2-L1)6(OAc)4(μ7-L2)2] (3), [Ni6Dy(μ2-L1)6(μ3-L1)2(OAc)3(μ7-L2)(OCH3)] (4), and [Ni6Dy(μ2-L1)6(μ3-L1)2(OAc)2(NO3)(OH)2(OCH3)2] (5) (HL1 = 8-hydroxyquinoline, H3L2 = 1,1,1-tris(hydroxymethyl)ethane) has been solvothermally prepared. Those clusters feature a heptanuclear disklike structure with 8-hydroxyquinolines as corner ligands restricting the expansion of the triangular lattice in spite of the metal ions or auxiliary coligands. The magnetic properties of those complexes vary according to metal ions and auxiliary coligands, for which slow magnetic relaxation is found in 5.

Magnetic, luminescence, topological and theoretical studies of structurally diverse supramolecular lanthanide coordination polymers with flexible glutaric acid as a linker

This contribution explores the topological, supramolecular, magnetic and luminescent properties of previously unknown CPs, which fall into category of glutarates without auxiliary coligands.

Structure and Photocatalytic Properties of a 3D Zinc(II) Triazolate Coordination Polymer Combining Hydroxyl and Formate Anions as the Auxiliary Coligands

A new 3D zinc coordination polymer, namely {[Zn4(dmtz)3(OH)3(HCOO)](NO3)}n (1, Hdmtz = 3,5- dimethyl-1,2,4-triazole), is hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single crystal X-ray diffraction analysis. The complex features a (3,4,5)- connected 3D cation framework constructed by μ3-bridging dmtz with hydroxyl and formate anions as the auxiliary ligands. Moreover, the photocatalytic properties of 1 are also investigated.

Syntheses, structures and properties of three lead(II) complexes constructed with 1,2,3,5-benzenetetracarboxylic acid

Three new lead(II) metal-organic coordination complexes constructed with tetracarboxyl tecton, namely, [Pb2(btec)] (1), [Pb3(µ4-O)(btec)(H2O)2]·H2O (2), and [Pb(btec)0.5(phen)] (3) (H4btec = 1,2,3,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline), have been prepared and characterized. A three-dimensional framework containing Pb(II) metal oxide sheet is being obtained in complex 1. Interestingly, a rather rare hexanuclear [Pb6(µ4-O2−)2]8+ octahedral core appeared in 2. The hexanuclear units are further connected by the btec4− ligands into a three-dimensional framework. When phen ligand was used as auxiliary coligand, a three-dimensional framework containing Pb2O2 dimer as building unit was observed in complex 3. Thermal stabilities and photoluminescent properties of complexes 1–3 have also been investigated.

Tuning of Thiyl/Thiolate Complex Near-Infrared Chromophores of Platinum through Geometrical Constraints

The chemistry of radical-ligand complexes of the transition metals has developed into a vibrant field of research that spans from fundamental studies on the relationship between the chemical and electronic structures to applications in catalysis and functional materials chemistry. In general, fine-tuning of the relevant properties relies on an increasingly diversifying pool of radical-proligand structures. Surprisingly, the variability of the conformational freedom and the number of distinct bonding modes supported by many radical proligands is limited. This work reports on the angular constraints and relative geometric alignment of metal and ligand orbitals as key parameters that render a series of chemically similar thiyl/thiolate complexes of platinum(II) electronically and spectroscopically distinct. The use of conformational flexible thiophenols as primary ligand scaffolds is essential to establishing a defined radical-ligand [(areneS)2PtII]•+ core whose electronic structure is modulated by a series of auxiliary coligands at platinum.

Syntheses, crystal structures, and properties of two dinuclear iron(III) complexes constructed with 1,2,3,5-benzenetetracarboxylic acid and chelating N-donor auxiliary coligands

Two dinuclear Fe(III) metal–organic complexes with tetracarboxylate and chelating N-donor ligands, [Fe(Hbtec)(phen)(H2O)]2·2H2O (1) and [Fe(Hbtec)(bpy)(H2O)]2·2H2O (2) (H4btec = 1,2,3,5-benzenetetracarboxylic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been prepared and characterized by elemental analysis, IR spectroscopic, and X-ray diffraction methods. Both complexes crystallize in the monoclinic space group P21/c with two Fe(III) ions bridged by two Hbtec3− ligands into a dinuclear unit. Hydrogen bonding connects the dinuclear units into a 3-D framework. The dinuclear units are 10-connected nodes that produce a 3-D framework with topology Schläfli symbol as (312·428·55). Thermal stabilities and luminescent properties of the two complexes have also been investigated.

Structure and photocatalytic properties of a 3D zinc(II) triazolate coordination polymer combining hydroxyl and formate anions as the auxiliary coligands

Structure and photocatalytic properties of a 3D zinc(II) triazolate coordination polymer combining hydroxyl and formate anions as the auxiliary coligands

Zn(II) and Cd(II) complexes assembled from versatile 1,2,3,5-benzenetetracarboxylic acid and chelating N-donor auxiliary coligands

Four new zinc(II) and cadmium(II) metal–organic coordination complexes with tetracarboxyl tecton and N-donor chelating ligands, namely, [Zn2(H2btec)2(bpy)2(H2O)2]·4H2O (1), [Zn4(btec)2(bpy)4(H2O)6]·2H2O (2), [Zn2(btec)(phen)H2O]·2H2O (3), and [Cd3(H2btec)2(phen)4(H2O)2]·2NO3 (4) (H4btec=1,2,3,5-benzenetetracarboxylic acid, bpy=2,2′-bipyridyl, phen=1,10-phenanthroline), have been prepared and characterized by elemental analysis, IR spectra and X-ray diffraction. Bi-nuclear and tetra-nuclear complexes are being observed in complexes 1 and 2, respectively, which attribute to the different deprotonation of H4btec ligands, further leading different coordination modes. Interestingly, both octahedral and triangular prism coordination environments display in complex 2. However, when phen substituted the bpy as auxiliary coligand, a two-dimensional sheet was observed in complex 3. Interestingly, when the transition metal ion was changed into Cd(II) in complex 4, the H4btec ligands are deprotonated into H2btec2− ligand with the help of nitrate group as counter ion, the Cd(II) atoms bridged the H2btec2− ligands into a one-dimensional chain. Thermal stabilities and photoluminescent properties of complexes 1–4 have also been investigated.

Three new luminescent Cd(II)-MOFs by regulating the tetracarboxylate and auxiliary co-ligands, displaying high sensitivity for Fe(3+) in aqueous solution.

Three new Cd(ii)-MOFs, [Cd(L1)0.5(bpp)] (), [Cd(L1)0.5(bipy)] (), and [Cd(L2)0.5(bipy)] () [H4Ln = (1,1':4',1''-terphenyl)-2',x,x'',5'-tetracarboxylic acid (n = 1, x = 3, and n = 2, x = 4), bpp = 1,3-di(4-pyridyl)propane, and bipy = 2,2'-bipyridine], have been synthesized using Cd(ii) ions and isomeric H4Ln ligands in the presence of auxiliary ligands via solvothermal reaction, and have been fully characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Complex is a three-dimensional (3D) pillar-layered network built from L1(4-) and bridging bpp co-ligands with a binodal (4,8)-connected gsp2 topology and a symbol of (4(4)·6(2))(4(16)·6(12)). was successfully synthesized using bipy instead of the bpp ligand used to assemble giving a 2D 4-connected sql net. is a 3D reticular framework with [Cd2(COO)4] SBUs based on L2(4-) ligands, displaying a (4,4)-connected lvt (4(2)·8(4)) topology. X-ray diffraction analysis revealed that the structures of the MOFs can be mediated by the steric effect of the tetracarboxylate and secondary co-ligands. The solid-state luminescence properties of the MOFs were measured carefully by ultraviolet irradiation at room temperature. In particular, exhibited a high sensitivity for Fe(3+) in aqueous solutions of mixed metal ions, which makes it a promising crystalline material to be a luminescent probe for Fe(3+). Importantly, can keep its original framework and be reused in sensing experiments. The sensing mechanism has also been studied in detail.

Strongly photoluminescent Eu(III) tetrazolate ternary complexes with phosphine oxides as powerful sensitizers

The Eu(III) cation forms electrically neutral photoluminescent complex with 5-(2-pyridyl-1-oxide)tetrazolate (PTO) anion. Although the photoluminescence properties of such tertiary Eu(III) and Tb(III) complexes were not as high (13 and 31% photoluminescence quantum yield, respectively) as reported for other diketonate lanthanide complexes probably because of high number of nitrogen atoms involved in PTO which leads to attachment of water molecules, reducing the luminescence quantum yield with vibrational and rotational quenching. Here, we report the removal of quencher molecules from the coordination sphere of tris–europium tetrazolate oxide complex by replacing them with various phosphine oxides which leads to improved photoluminescence quantum yield for the complexes by acting as auxiliary co-ligands with that of the main antenna 5-(2-pyridyl-1-oxide)tetrazolate. The coordination sphere in these complexes can be complemented by aromatic phosphine oxides to provide highly photoluminescent Eu(III) complexes. The highest quantum yield was 38% in 3 [Eu(PTO)3·DPEPO](H2O)5 containing bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as compared to tris–europium complex with 5-(2-pyridyl-1-oxide)tetrazolate.

Dy(acac)₃(dppn)]·C₂H₅OH: construction of a single-ion magnet based on the square-antiprism dysprosium(III) ion.

The present work reports a new mononuclear Dy(III) complex [Dy(acac)3(dppn)]·C2H5OH (1) (acac = acetylacetone, dppn = benzo[i]dipyrido-[3, 2-a:2',3'-c]phenazine). X-ray crystallography analysis reveals that compound 1 is a discrete molecular complex and the Dy(III) center lies in a square-antiprism coordination environment. Furthermore, complex 1 shows single-ion magnet (SIM) behavior. Compared to the reported complexes [Dy(dppz)(acac)3]·CH3OH, [Dy(dpq)(acac)3] and [Dy(phen)(acac)3], complex 1 exhibits a different energy barrier, which might be raised from the different coordination environment caused by the different auxiliary co-ligand dppn. The energy barrier variations of these Dy(III)-complexes are consistent with their square antiprism structural features.

Topological diversification of two new Cd(II) photoluminescent coordination polymers via auxiliary N-donor ligands

Two new cadmium(II) coordination polymers, [Cd2(nda)2(L1)] n (1) and [Cd(nda)(L2)0.5] n (2), were hydrothermally synthesized with 1,4-naphthalenedicarboxylic acid (H2nda) and auxiliary N-donor coligands [L1 = 1,5-bis(2-methyl-imidazol-1-yl)pentane and L2 = 4,4′-bis(2-methyl-imidazol-1-ylmethyl)biphenyl]. Single-crystal X-ray diffraction analyses showed that the topological networks are different when the N-donor ligands are changed. Compound 1 showed a (416.65) topology and 2 showed a twofold interpenetrating pcu topology.

Zinc(ΙΙ) complexes with 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydrate and different N-donors: syntheses, crystal structures, and emission properties

Two new ZnII complexes, {[Zn(L)(phen)(H2O)] · H2O}∞ (1) and {[Zn(L)(4bpy)(H2O)] · H2O}∞ (2) (L = 5,6-dihydro-1,4-dithiin-2,3-dicarboxylate, phen = 1,10-phenanthroline, and 4bpy = 4,4′-bipyridine), have been prepared by in situ reaction of Zn(ClO4)2 · 6H2O with 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydrate in the presence of lithium hydroxide, together with incorporating chelating phen or bridging 4bpy as co-ligands. Their structures were determined by single-crystal X-ray diffraction. Complex 1 takes a 1-D helical structure that is further assembled into a 2-D network by O–H ··· O, C–H ··· O hydrogen bonds, and weak S ··· S interactions, and then an overall 3-D supramolecular framework was formed by π ··· π stacking interactions. Complex 2 possesses a 2-D (4,4)-layered structure. The structural difference between 1 and 2 can be attributed to the different N-donor auxiliary co-ligands. Both 1 and 2 are photoluminescent materials whose emission properties are closely related to their intrinsic structure.

Structure and bonding analysis in dihalobismuth complexes of iron, ruthenium and osmium [(η5-C5H5)(CO)2M(BiX2)]: A theoretical study

Density functional theory (DFT) calculations have been performed to investigate the nature of the M–Bi bonds in dihalobismuth complexes of iron, ruthenium and osmium, [(η5-C5H5)(CO)2M(BiX2)] (M=Fe, Ru, Os; X=Cl, Br, I) and [(η5-C5H5)(PMe3)2Fe(BiX2)] (X=Cl, Br, I), at the BP86/TZ2P/ZORA level of theory. Pauling and Mayer bond orders of the optimized structures show that the M-Bi bonds in these complexes are nearly M–Bi single bonds. The π bonding contribution is, in all complexes, significantly smaller than the corresponding σ bonding contribution, representing only 5–14% of the total orbital interaction. Thus, in these complexes, [BiX2] behaves predominantly as σ donor. The values of the Mayer bond order of the M–Bi bonds in dihalobismuth complexes suggest a significant covalent contribution to the M–Bi bonds. These observations are supported by the greater contributions of the covalent interaction energy ΔEorb than the electrostatic interactions ΔEelstat in all the dihalobismuth complexes. The absolute values of the ΔEint, ΔEorb and ΔEelstat contributions to the M–Bi bonds decrease according to X=Cl>Br>I, while the values of these energy terms increases in all four sets of complexes in the order Fe<Ru<Os. Upon substitution of the auxiliary CO ligand with the PMe3 ligand, the ΔEint, ΔEorb and ΔEelstat contributions increase.

Copper(II) Complexes with cis-Epoxysuccinate Ligand: Syntheses, Crystal Structures, and Magnetic Properties

Three CuII complexes with cis-epoxysuccinate ligand were synthesized and structurally characterized: [Cu(ces)(phen)]2 (1), [Cu(ces)(bpy)]2 (2), and {[Cu2(ces)(pp)2(CH3OH)]}∞ (3), (ces = cis-epoxysuccinate, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, and pp = 3-(2-pyridyl)pyrazole with pyrazolyl N-donor deprotonated). Structural analysis reveals that both 1 and 2 have the very similar dinuclear units that are extended by the intermolecular supramolecular interactions, such as C–H⋯O, C–H⋯π, and aromatic π⋯π stacking interactions, to give rise to the higher-dimensional frameworks. Complex 3 has a two-dimensional (2D) layered structure that is further assembled to form a three-dimensional framework by the inter-layer C–H⋯O hydrogen-bonding and C–H⋯π interactions. A structural comparison with those of our previous work in the absence of auxiliary co-ligand suggests that the introduction of 2,2′-bipyridyl-like molecules plays an important role in constructing the final structures of 1–3. Magnetic measurements demonstrate that 1 and 2 exhibit ferromagnetic coupling with the corresponding J values of 1.8 cm–1 for 1 and 1.5 cm–1 for 2, whereas 3 shows more complicated magnetic coupling.

Organometallic Oligomer Resolved by Radial Distribution Function of X-ray Diffraction Analysis

Platinum-organic oligomers are actively studied for their large physical and functional properties such as solubility, processability, color, luminescence, and optoelectronics related to the different metal groups and auxiliary coligands around the metal coordination spheres. Previous studies on nanotechnology devices have shown that the structural organization of handled metallopolymer generates several 2D or 3D nano-objects, but only based on trans polymorph chains. Here we report the first self-assembly of powder cis-Pt-DEBP oligomers that shows great self-assembling ability to form nanoscale supramolecular architectures. As a powder is obtained that shows a poor crystalline organization of the aggregates, the energy-dispersive X-ray diffraction is the nondestructive technique of choice to obtain short-range order structural parameters of a single nano-object by radial distribution function analysis. The supramolecular architecture of 8-units-long chains reveals a self-assembling organization of 18 chains exhibiting an overall linear inverted open square structure. The ensemble of oligomer chains form a parallelepiped shape with small internal square cavities of approximately 3.2 nm diameter capable of hosting smaller molecules, which opens up to all applications where sieving and sensing is important. This structural investigation of short-range order materials has provided a substantial additional impetus to the field by opening up the area of self-assembled supramolecular materials based on metallopolymers for technological applications.

Cadmium(ii) coordination polymers based on a bulky anthracene-based dicarboxylate ligand: crystal structures and luminescent properties

In our efforts to continuously explore the influence of ligands with larger conjugated π-systems on the related structures and properties of their complexes, four CdII complexes with anthracene-9,10-dicarboxylate (L) and relevant auxiliary ligands were synthesized and characterized: {[Cd2(L)2(bipy)(H2O)2](C2H5OH)0.5(H2O)2.25}∞ (1), Cd2(L)(HL)2(phen)4 (2), {[Cd2(L)1.5(Hpypz)4](L)0.5}∞ (3), and {[Cd(L)2](H2daco)(C2H5OH)2(H2O)}∞ (4) (bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline, Hpypz = 3-(2-pyridyl)pyrazole, and daco = 1,5-diazacyclooctane). Structural analyses show that complex 1 has a three-dimensional (3D) structure with a Schlafli symbol of (6·82)2(6·85). Complexes 2 and 3 take dinuclear and two-dimensional (2D) structures, respectively, due to the introduction of different 2,2′-bipyridyl-like chelating ligands, phen for 2 and Hpypz for 3. Complex 4 possesses another three-dimensional (3D) two-fold interpenetrating diamondoid network by introducing daco as an auxiliary co-ligand. The present results indicate that the natures of the auxiliary ligands have important effects on the formation of the final structures of such complexes. Moreover, the luminescent properties of complexes 1–4 and the corresponding ligands have also been investigated in detail.

Four novel Co(II) and Mn(II) coordination polymers with triazolyl derivate: Syntheses, crystal structures and magnetic properties

Four novel coordination polymers, one-dimensional chains [M(PTE) 2(N 3) 2] n (M = Mn for 1 and Co for 2), and two-dimensional layers [M(PTE) 2(dca) 2] n (M = Mn for 3 and Co for 4) (PTE = 1-(2,4-difluorophenyl-2-(1H-1,2,4-triazol-1-yl)ethanone, dca = dicyanamide anion, N(CN) 2 −), have been synthesized under mild ambient conditions and structurally characterized by single crystal X-ray diffraction. In all four crystal structures, the metal atoms adopt octahedral coordination geometry with six nitrogen atoms from two monodentate PTE ligands and four azido (or dca) bridging ligands. The crystal structures of 1 and 2 are isostructural 1-D polymeric chains, alternatively linked by double end-on and double end-to-end azido bridges. However, the bent dca ligands as bidentate μ 2-1,5 bridging ligands interlink the octahedral metal units to lead to 2-D (4,4) grid networks in 3 and 4. Temperature-dependent magnetic measurements in 2–300 K have been performed for these four polymers, and suggest alternative ferro- and antiferromagnetic couplings for end-on and end-to-end azido bridges in 1, and the dominant ferromagnetic coupling in 2, respectively. Both polymers 3 and 4 show weak antiferromagnetic exchanges through the μ 2-1,5-dca bridges. The effects of auxiliary coligands on the structure and the nature of these magnetic exchanges are discussed in the light of the crystal structures in detail.

Three-Dimensional Heterometallic Chiral Cr−Mn Compound Constructed by Cyanide and Dicyanamide Bridges

Increasing the number of chiral centers by adjusting auxiliary coligands results in a heterometallic metamagnet with a three-dimensional homochiral framework containing both cyanide and dicyanamide bridges.