Formation Of One-dimensional Coordination Polymer Research Articles

Synthesis, spectral, in silico/molecular docking and pharmacological studies of biologically potent triorganotin(IV) carboxylates

A series of compounds containing a glutaric anhydride-based carboxylate ligand (LH) and three triorganotin derivatives R3SnL for R = Me (1), nBu (2), and pH (3) are described in this article. The synthesis of the compounds was confirmed by microelemental CHN analysis, FT-IR, NMR and in the case of LH, 1 and 2 by single crystal X-ray crystallography, revealing the formation of one-dimensional coordination polymers for 1 and 2 with trans-C3O2 trigonal-bipyramidal geometries for the tin(IV) atoms. The anti-microbial activity was explored with the MIC values of 2 (≤ 0.25 µg/mL against the bacterium S. aureus and fungal strains C. albicans and C. neoformans) being less than observed for the anti-bacterial drug vancomycin-HCl (1 μg/mL) and anti-fungal drug fluconazole (≤ 0.25 and 8 μg/mL, respectively). The maximum cytotoxicity was observed for 2, against the human embryonic kidney (HEC239) cell line, with CC50 ≤ 25 μg/mL. An evaluation of the compound-DNA interactions was performed through UV–Visible spectroscopic and viscometric experiments, with the observation of hypochromic along with slight bathochromic shifts and an increase in viscosity, respectively, revealing an intercalative mode of interaction. In comparison with the standard anti-oxidant ascorbic acid, the greatest scavenging of DPPH was recorded for 3 followed by 2, 1 and LH. The human malignant glioma cell line (MG-U87) was used to explore the anti-cancer potential of the synthesised compounds. Compounds 3 and 2 (IC50 = 5 and 21 µM, respectively) showed encouraging results when compared to cisplatin (IC50 = 133 µM). The anti-leishmanial data shows that at a 1000 µg/mL dose, the greatest percentage inhibition was observed for 2 (87.15 ± 0.01 %) which is almost equivalent to that for amphotericin B (90.67 ± 0.15 %). The docking results with SS-DNA revealed the compounds undergo an intercalative mode of interaction with the nitrogenous bases adenine, guanine and cytosine, with docking score order: 3 (-8.11) > 2 (-8.02) > 1 (-6.99) > LH (-6.38). Similarly, the docking results against the Brest cancer receptor BRCA2, indicate the highest binding score was observed for 3. The anti-leishmanial docking data indicates 2 as having maximum docking score (-7.79). The in silico study, performed to reveal the drug-likeness behaviour of the news compounds, suggest that they possess the properties of orally active drugs.

Synthesis, crystal structures, luminescent and magnetic properties of rare earth dinuclear complexes and one-dimensional coordination polymers supported by two derivatives of cinnamic acid

A series of lanthanide dinuclear complexes and chains incorporating two derivatives of cinnamic acid (2-methoxycinnamic acid and 3-methoxycinnamic acid) have been synthesized and characterized by elemental analyses, Infra-Red Spectroscopy, X-ray diffraction, photoluminescence and magnetic measurements. The use of the 2-methoxycinnamic ligand enables the synthesis of two dinuclear complexes (Eu3+ (1), Tb3+ (2)), while the presence of 3-methoxycinnamic acid induces the formation of one-dimensional coordination polymers (Eu3+ (3), Gd3+ (4)). Investigations of the magnetic properties reveals a field-induced slow relaxation of the magnetization for the gadolinium analogue 4, whereas the characteristic Eu3+ luminescence is observed for the europium-based materials 1 and 3.

Impact of Isomeric Dicarboxylate Ligands on the Formation of One-Dimensional Coordination Polymers and Metallocycles: A Novel cis→trans Isomerization.

A series of Co(II), Ni(II) and Cu(II) coordination polymers and dinuclear metallocycles containing 4-aminopyridine (4-ampy) and benzenedicarboxylate ligands, {[M(4-ampy)2(1,4-BDC)]·H2O·CH3CH2OH}n (M = Ni, 1a; Co, 1b, 1,4-H2BDC = benzene-1,4-dicarboxylic acid), {[Ni2(4-ampy)4(1,3-BDC)2]·H2O·CH3CH2OH}n (1,3-H2BDC = benzene-1,3-dicarboxylic acid), 2, [M2(4-ampy)4(1,2-BDC)2] (M = Ni, 3a; Co, 3b, 1,2-H2BDC = benzene-1,2-dicarboxylic acid), [Co(4-ampy)2(1,3-BDC)]n, 4, {[Cu(4-ampy)2(1,4-BDC)] CH3CH2OH}n, 5a, and {[Cu(4-ampy)2(1,4-BDC)]·H2O}n, 5b·H2O, are reported, which were hydrothermally prepared and structurally characterized by using single crystal X-ray diffraction. Complexes 1a and 1b are isomorphous 1D zigzag chains, while 2 displays a concave–convex chain and 3a and 3b are dinuclear metallocycles that differ in the boding modes of the 1,2-BDC2− ligands, forming a 3D and a 2D supramolecular structures with the pcu and sql topologies, respectively. Complex 4 exhibit a 1D helical chain and complexes 5a and 5b·H2O are 1D linear and zigzag chains, in which the Cu2-1,4-BDC2− units adopt the cis and trans configurations, respectively. A novel irreversible structural transformation due to cis→trans isomerization of the Cu2-1,4-BDC2− units was observed in 5b⋅H2O and 5a upon water adsorption of the desolvated product of 5b·H2O.

In-situ formation of one-dimensional coordination polymers in molecular junctions

We demonstrate the bottom-up in-situ formation of organometallic oligomer chains at the single-molecule level. The chains are formed using the mechanically controllable break junction technique operated in a liquid environment, and consist of alternating isocyano-terminated benzene monomers coordinated to gold atoms. We show that the chaining process is critically determined by the surface density of molecules. In particular, we demonstrate that by reducing the local supply of molecules within the junction, either by lowering the molecular concentration or by adding side groups, the oligomerization process can be suppressed. Our experimental results are supported by ab-initio simulations, confirming that the isocyano terminating groups display a high tendency to form molecular chains, as a result of their high affinity for gold. Our findings open the road for the controlled formation of one-dimensional, single coordination-polymer chains as promising model systems of organometallic frameworks.

CoIIComplexes with a Tripyridine Ligand, Containing a 2,6-Di-tert-butylphenolic Fragment: Synthesis, Structure, and Formation of Stable Radicals

Interaction of a tripyridine ligand bearing a 2,6-di-tert-butylphenolic fragment (L, 2,6-di-tert-butyl-4-(3,5-bis(4-pyridyl)pyridyl)phenol) with CoII pivalate or chloride led to the formation of one-dimensional coordination polymers [Co(L)Cl2]n·nEtOH (1) and [Co3(L)2(OH)(Piv)5]n (2) or a trinuclear complex Co3(H2O)4(L)2Cl6 (3) (Piv– = pivalate). Chemical oxidation of L and 1–3 by PbO2 or K3[Fe(CN)6], as well as exposure of L (in solution or solid state) and 2 (in solid state) to UV irradiation, led to the formation of free radicals with g = 2.0024, which probably originated because of oxidation of 2,6-di-tert-butylphenolic groups. These radicals were stable for several days in solutions and more than 1 month in solid samples. Irradiation and oxidation of the solid samples probably caused formation of the phenoxyl radical only on their surface. It was shown by density functional theory calculations that exchange coupling between the unpaired electron of the phenoxyl radical and CoII ions was negligibly weak and could not affect the electron paramagnetic resonance signal of the radical, as well as exchange coupling of CoII ions could not be transmitted by L. The latter conclusion was confirmed by the analysis of magnetic properties of 1: temperature dependency of magnetic susceptibility (χM) of 1 could be simulated by a simple model for isolated CoII ions.

Lanthanide Coordination Polymers and MOFs based on the Dicyanodihydridoborate Anion.

New lanthanide cyanoborates were synthesized from anhydrous lanthanide chlorides and the acid H[BH2 (CN)2 ] in either acetonitrile or pyridine. Reactions in acetonitrile lead to three-dimensional, anionic metal-organic frameworks (MOFs) 3 ∞ [Ln2 {BH2 (CN)2 }9 ]⋅[Ln(CH3 CN)9 ] (Ln=Ce, Eu, Tb) which incorporate complex cations [Ln(CH3 CN)9 ]3+ in the pores of the framework for charge compensation. In contrast, the reactions in pyridine result in the formation of one-dimensional coordination polymers 1 ∞ [H(py)2 ][LnCl2 {BH2 (CN)2 }2 (py)2 ]⋅0.5 py (Ln=Ce, Pr, py=pyridine) with [H(py)2 ]+ as counter ions for the anionic strand structure. The products show intense photoluminescence, for Ce3+ based on 5d-4f transitions in the blue spectral region, whereas the Eu3+ and Tb3+ compounds exhibit characteristic photoluminescence based on 4f-4f transitions of the respective lanthanide ions. The observed photoluminescence is mainly attributed to a direct excitation of the lanthanide ions and sensitization of the lanthanide ions by the [BH2 (CN)2 ]- anions. These results mark the utilized borate anions as versatile building block for new coordination compounds.

Methyl-substituted cucurbit[6]uril-based microporous supramolecular frameworks for highly selective Et2O/CH3OH adsorption

The interaction and supramolecular assemblies of two alkaline earth metal ions, Ca2+ and Ba2+, with methyl-substituted cucurbit[6]uril derived from 3α-methyl-glycoluril (HMeQ[6]) in aqueous HCl solution have been investigated. X-ray diffraction analysis revealed that coordination of HMeQ[6] with these metal ions resulted in the formation of one-dimensional coordination polymers in the presence of polychloride transition metal anions, such as [CdCl4]2−, as structure-directing agents. The supramolecular frameworks exhibit excellent thermal stability as well as permanent porosity. The activated desolvated materials show high Et2O and CH3OH adsorption capacity and selectivity compared with other porous organic materials assembled solely through hydrogen bonding under ambient conditions.

Heat-induced formation of one-dimensional coordination polymers on Au(111): an STM study.

The formation of one-dimensional coordination polymers of cyano-substituted porphyrin derivatives on Au(111) induced by thermal annealing is demonstrated by means of scanning tunnelling microscopy. The polymer is stabilised by an unusual threefold coordination motif mediated between an Au atom and the cyano groups of the porphyrin derivatives.

Coordination of alkaline-earth metal ions to hexanohydroxyhexanomethylcucurbit[6]uril and formation of tubular coordination polymers

The interaction of alkaline-earth cations (AE2+) with hexanohydroxyhexanomethylcucurbit[6]uril (HHQ[6]) in the presence of CdCl2 in aqueous HCl solution was investigated. Single crystal X-ray diffraction analysis revealed that the interaction results in the formation of one-dimensional coordination polymers of HHQ[6] with AE2+ (Ca, Sr or Ba). In addition, compounds containing Ca and Sr are isomorphous. Moreover, the compound obtained from the HHQ[6]–MgCl2–CdCl2–HCl system contained only a metal-free HHQ[6]-based supramolecular assembly. ITC experiments showed that the interaction between HHQ[6] and Mg2+ could not be effectively measured, and that the interaction of Ca2+ or Sr2+ with HHQ[6] are driven by ΔH and ΔS, whereas the interaction between Ba2+ and HHQ[6] is driven by ΔH.

Synthesis and structural studies of diorganotin(IV)-based coordination polymers bearing silaalkylphosphonate ligands and their transformation into colloidal domains.

The contribution of silaalkylphosphonic acids Me3SiCH2P(O)(OH)2 (1) and Me3SiC(CH3)2P(O)(OH)2 (2) as ligands was demonstrated for the first time by the isolation of new diorganotin(IV) phosphonates Et2Sn{OP(O)(OH)CH2SiMe3}(OSO2Me) (3), (Et2Sn)6{O3PC(CH3)2SiMe3}4(OSO2Me)4 (4), and Et2Sn(O3PCH2SiMe3) (5). X-ray crystallographic studies of 1-4 are presented. The structures of 1 and 2 adopt extended motifs by virtue of P-OH···O═P-type hydrogen bonding interactions. The molecular structure of 3 is composed of a dimer formed by bridging hydrogen phosphonate groups, while the sulfonate group appended on each tin atom acts in a μ2-bridging mode to afford the formation of one-dimensional coordination polymer featuring alternate eight-membered [-Sn-O-P-O-]2 and [-Sn-O-S-O-]2 rings. The asymmetric unit of 4 is composed of two crystallographically unique trinuclear tin phosphonate clusters with a Sn3(μ3-PO3)2 core linked together by coordinative association of a μ2-sulfonate group, while the remaining sulfonates are involved in the construction of a two-dimensional self-assembly. The identity of 1-5 in solution was established by IR and multinuclear ((1)H, (13)C, (31)P, (119)Sn) NMR spectroscopy. The presence of silaalkyl group in 5 imparts unusual solubility in hydrocarbon, aromatic, and ether solvents. As a consequence, the formation of colloidal particles of 5 featuring rodlike morphology was achieved by ultrasonication of a solution in ethanol-chloroform mixture.

Effect of increasing ligand length on the structure of silver complexes

A new series of ligands in which nicotinic acid was linked to different monomethyloligoethers and their corresponding silver complexes were prepared. The crystal structures of the silver compounds were investigated to determine the effect of increasing flexibility of the ligands on coordination to the metal ion and crystal packing. We observed the formation of one-dimensional coordination polymers for the shortest ligand derived from monoethylene glycol, the formation of stacks for the diethylene-glycol-based ligand with silver triflate, and even a helical structure for the triethylene-glycol-derived ligand complex. The three ligands, ([C9H11O3N] (L1), [C11H15O4N] (L2), and [C13H19O5N] (L3)), and the four new complexes, [Ag(L1)2(NO3)] (1), [Ag(L1)2(SO3CF3)] (2), [(Ag(L2)2(SO3CF3)] (3), and [Ag(L3)2]PF6 (4)), are presented in this paper along with an analysis of their structural features.

The reactions of dialkylgallium hydrides with tert-butylethynylbenzenes—a systematic investigation into the course of hydrogallation reactions

The reactions of bis- and tris(tert-butylethynyl)benzenes with dialkylgallium hydrides afforded two different types of products. 1,4-Di(tert-butylethynyl)benzene and dialkylgallium hydrides R(2)GaH bearing relatively small substituents (R = Et, nPr) gave the expected addition products with each C triple bond C triple bond inserted into a Ga-H bond. The intact GaR(2) groups are attached to those carbon atoms which are in alpha-position to the benzene rings, and intermolecular Ga-C interactions led to the formation of one-dimensional coordination polymers. In contrast secondary reactions with the release of the corresponding trialkylgallium derivatives GaR(3) (R = Et, nPr, iPr, CH(2)tBu, tBu) were observed for all hydrogallation reactions involving the trisalkyne 1,3,5-tris(tert-butylethynyl)benzene. A similar reaction was observed upon treatment of the 1,4-bisalkyne with a dialkylgallium hydride bearing a relatively bulky substituent (R = neopentyl). Cyclophane type molecules are formed in all these cases with two or three gallium atoms in the bridging positions between both benzene rings.

Synthesis, characterization and single crystal structures of one-dimensional coordination polymers formed with [Ni(L)]·2ClO4 and polycarboxylate ligands

Two new one-dimensional coordination polymers {[Ni(L)(maleate)] · H2O}n(1) and {[Ni(L)(H2btc)] · 2DMF}n (L = cyclam, btc = 1,2,4,5-benzenetetracarboxylate, DMF = N,N-dimethylformamide) (2) have been synthesized and structurally characterized by single crystal X-ray diffraction. In the structures (1) and (2), the carboxylate groups of bridging ligands are coordinated to nickel(II) cyclams resulting in the formation of one-dimensional coordination polymers. In addition to the Ni–O bonds, it is observed that the hydrogen bonding interactions between the pre-organized N–H groups of the cyclams and bridging anions support the formation of coordination polymers in both complexes.

Anion-directed assembly of supramolecular zinc(ii) halides with N,N′-bis-4-methyl-pyridyl oxalamide

We report here the supramolecular structures and solid state luminescence of zinc(II) halides with N,N′-bis-4-methyl-pyridyl oxalamide (L), where the supramolecular assembly formed is dependent on the halide, and led to the formation of one-dimensional coordination polymers for Cl ([ZnCl2(L)]n) and Br ([ZnBr2(L)]n) or a discrete macrocycle for I ([ZnI2(L)]2), respectively. The rectangular structure of iodo compounds with pyridyl amide L shows an interesting nanotube framework built from π⋯π interactions in combination with hydrogen bonding. To our knowledge, these are rare examples of the anion-directed assembly of supramolecular structures. The low energy emission at ca. 500 nm for [ZnI2(L)]2 is assigned to a ligand-to-metal charge-transfer (LMCT) transition.