Novel family of bis-pyrazole coordination complexes as potent antibacterial and antifungal agents

A new pyrazole ligand, N,N-bis(2(1′,5,5′-trimethyl-1H,1′H-[3,3′-bipyrazol]-1-yl)ethyl)propan-1-amine (L) was synthesized and characterized by ¹H-NMR, ¹³C-NMR, FT-IR and HRMS. The coordination ability of the ligand has been employed for the construction of a new family of coordination complexes, namely: [Cu₂LCl₄] (1), [ML(CH₃OH)(H₂O)](ClO₄)₂ (M^II = Ni (2), Co (3)) and [FeL(NCS)₂] (4). The series of complexes were characterized using single-crystal X-ray diffraction, HRMS, FT-IR and UV-visible spectroscopy. Moreover, the iron(ii) analogue was investigated by ⁵⁷Fe Mössbauer spectroscopy and SQUID magnetometry. Single-crystal X-ray structures of the prepared complexes are debated within the framework of the cooperative effect of the hydrogen bonding network and counter anions on the supramolecular formations observed. Furthermore, within the context of biological activity surveys, these compounds were reviewed against different types of bacteria to validate their efficiency, including both Gram-positive as well as Gram-negative bacteria. Enhanced behaviour towards Fusarium oxysporum f. sp. albedinis fungi, were detected for 1 and 4.

A new pyrazole ligand L and four coordination complexes were synthesized and characterized by different spectroscopic methods. These were found to be promising antibacterial and antifungal agents.

Bis(pyridyl)-disulfonamides: structural comparison with their carboxamidic analogues and the effect of molecular geometry and supramolecular assembly on their photophysical properties

Presence of Sulphur or Carbon atom in amidic group is reciprocated in their solid state structures. AIE or ACQ of disulphonamides is explained on the basis of their crystal packing.

Solid-State Structural Transformation and Photoluminescence Properties of Supramolecular Coordination Compounds

The combination of strong coordination bonds and hydrogen bonding interactions were used to generate a series of supramolecular coordination materials (SCMs), which was achieved by reacting a bis-pyridyl amide ligand, namely N-(4-pyridyl)nicotinamide (4PNA) with copper(II), zinc(II), and cadmium(II) benzoates. The SCMs were structurally characterized using X-ray diffraction and the key intermolecular interactions were identified via Hirshfeld surface analysis. The role of solvent molecules on the supramolecular architecture was analyzed by synthesizing the SCMs in different solvents/solvent mixtures. A solvent-mediated solid-state structural transformation was observed in copper(II) SCMs and we were able to isolate the intermediate form of the crystal-to-crystal transformation process. The luminescence experiments revealed that complexation enhanced the fluorescence properties of 4PNA in the zinc(II) and cadmium(II) SCMs, but a reverse phenomenon was observed in the copper(II) SCMs. This work demonstrated the tuning of supramolecular assembly in coordination compounds as a function of solvents for generating SCMs with diverse properties.

Effect of pyridyl donors from organic ligands versus metalloligands on material design

This review illustrates designs and structures of various coordination frameworks constructed using assorted organic ligands and metalloligands offering pyridyl donors to evaluate the impact of flexibility versus rigidity on material design.

Tuning of crystallization method and ligand conformation to give a mononuclear compound or two-dimensional SCO coordination polymer based on a new semi-rigid V-shaped bis-pyridyl bis-amide ligand

With the new semi-rigid V-shaped bidentate pyridyl amide compound 5-methyl-N,N'-bis(pyridin-4-yl)benzene-1,3-dicarboxamide (L) as an auxiliary ligand and the Fe^II ion as the metal centre, one mononuclear complex, bis(methanol-κO)bis[5-methyl-N,N'-bis(pyridin-4-yl)benzene-1,3-dicarboxamide-κN]bis(thiocyanato-κN)iron(II), [Fe(SCN)₂(C₁₉H₁₆N₄O₂)₂(CH₃OH)₂] (1), and one two-dimensional coordination polymer, catena-poly[[[bis(thiocyanato-κN)iron(II)]-bis[μ-5-methyl-N,N'-bis(pyridin-4-yl)benzene-1,3-dicarboxamide-κ²N:N']] methanol disolvate dihydrate], {[Fe(SCN)₂(C₁₉H₁₆N₄O₂)₂]·2CH₃OH·2H₂O}_n (2), were prepared by slow evaporation and H-tube diffusion methods, respectively, indicating the effect of the method of crystallization on the structure type of the target product. Both complexes have been structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. The single-crystal X-ray diffraction analysis shows that L functions as a monodentate ligand in mononuclear 1, while it coordinates in a bidentate manner to two independent Fe(SCN)₂ units in complex 2, with a different conformation from that in 1 and the ligands point in two almost orthogonal directions, therefore leading to a two-dimensional grid-like network. Investigation of the magnetic properties reveals the always high-spin state of the Fe^II centre over the whole temperature range in 1 and a gradual thermally-induced incomplete spin crossover (SCO) behaviour below 150 K in 2, demonstrating the influence of the different coordination fields on the spin properties of the metal ions. The current results provide useful information for the rational design of functional complexes with different structure dimensionalities by employing different conformations of the ligand and different crystallization methods.

A thermal- and light-induced switchable one-dimensional rare loop-like spin crossover coordination polymer

Rare loop-like isostructural one-dimensional coordination polymer (1D-CP) systems formulated as {Fe(DPIP)₂(NCSe)₂}_n·4DMF (1) and {Fe(DPIP)₂(NCSe)₂}_n·4DMF (2) were obtained by self-assembling Fe^II and pseudohalide NCX^-(X = S, Se) ions in presence of the V-shaped bidentate bridging ligand, namely, N,N'-dipyridin-4-ylisophthalamide (DPIP), and were characterized by elemental analysis, IR spectroscopy, TGA, single crystal X-ray diffraction and powder X-ray diffraction. The magnetic studies show that complex 2 undergoes a complete thermally induced spin crossover (SCO) behavior centered at T_1/2 = 120 K with ca. 5 K thermal hysteresis loop and light-induced excited spin state trapping effect (LIESST) with T_LIESST = 65 K. However, either the homologous X = S (1) or the desolvated form of complex 2 is high spin at all temperatures, proving further the concerted synergy for the SCO of 2 between the intrinsic ligand field and that indirectly induced via hydrogen bond interaction. The current results provide valuable information for the design of new 1D SCO systems via the rational control of the cooperated effects derived from the intramolecular coordination bond and the intermolecular supramolecular interactions.

Sonochemical synthesis of a nano-structured zinc(II) amidic pillar metal-organic framework

A facile and environmentally friendly nano-scale synthesis of a Zn(II) metal-organic framework (MOF), {[Zn4(BDC)4(bpta)4]·5DMF·3H2O}n (1) (bpta=N,N'-bis(4-pyridinyl)-1,4-benzenedicarboxamide, BDC=1,4-dicarboxylate, DMF=N,N-dimethylformamide), with nanorods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure has been explored. This MOF has been characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and IR spectroscopy. Some parameters such as concentration of initial reagents, power ultrasound irradiation and time effects on size and morphology of nano-structured compound 1 have been studied.

A two-dimensional ZnII coordination polymer constructed from benzene-1,2,3-tricarboxylic acid and N,N'-bis[(pyridin-4-yl)methylidene]hydrazine

The hydrothermal synthesis of the novel complex poly[aqua(μ4-benzene-1,2,3-tricarboxylato)[μ2-4,4'-(hydrazine-1,2-diylidenedimethanylylidene)dipyridine](μ3-hydroxido)dizinc(II)], [Zn(C9H3O6)(OH)(C12H10N4)(H2O)]n, is described. The benzene-1,2,3-tricarboxylate ligand connects neighbouring Zn4(OH)2 secondary building units (SBUs) producing an infinite one-dimensional chain. Adjacent one-dimensional chains are connected by the N,N'-bis[(pyridin-4-yl)methylidene]hydrazine ligand, forming a two-dimensional layered structure. Adjacent layers are stacked to generate a three-dimensional supramolecular architecture via O-H...O hydrogen-bond interactions. The thermal stability of this complex is described and the complex also appears to have potential for application as a luminescent material.

Amide-containing zinc(ii) metal–organic layered networks: a structure–CO2 capture relationship

An intimate interrelationship between the structural characteristics and their CO₂ adsorption behavior has been demonstrated in this study.

Coordination polymers derived from pyridyl carboxylate ligands having an amide backbone: an attempt towards the selective separation of CuII cation following in situ crystallization under competitive conditions

Selective separation of Cu^II following in situ crystallization of coordination polymers derived from a pyridyl amide carboxylate ligand was achieved.

1D, 2D and 3D coordination polymers of 1,3-phenylene diisonicotinate with Cu(i)/Cu(ii): Cu2I2 building block, anion influence and guest inclusions

The reactions of a flexible bidentate ligand 1,3-phenylene diisonicotinate (L) with Cu(i/ii) salts afforded coordination polymers with varied dimensionalities and guest inclusion capabilities.

Aromatic Polycarboxylate-Tuned Assembly of Three New 2D Copper(II) Complexes Derived from a Flexible Bis(pyridylamide) Ligand

Three new 2D copper(ii) complexes [Cu(NIPH)(L)] (1), [Cu(BDC)(L)(H2O)] (2), and [Cu(HBTC)(L)]·2H2O (3) were hydrothermally synthesized by self-assembly of aromatic polycarboxylates (H2NIPH = 5-nitroisophthalic acid, H2BDC = 1,3-benzenedicarboxylic acid, H3BTC = 1,3,5-benzenetricarboxylic acid) and the flexible bis(pyridylamide) ligand L (L = N,N′-di(3-pyridyl)succinamide), and structurally characterized by single crystal X-ray diffraction, and elemental, IR, and thermogravimetric analyses. Compound 1 is a 2D coordination polymer based on tri-flexural helix chains (left-, right-handed [Cu-L]n helix chains, and left-handed Cu-NIPH helix chain). Compound 2 exhibits a 2D wavelike polymeric layer structure constructed from a 1D [Cu-L]n sinusoidal chain and a 1D [Cu-BDC]n V-like chain. Compound 3 possesses a 2D double-layer network formed from 1D [Cu-L]n zigzag chains and 1D [Cu-HBTC]2n double chains. The fluorescent properties of the three compounds and the electrochemical behaviour of compound 2-bulk-modified carbon paste electrode were also studied.

A case for molecular recognition in nuclear separations: sulfate separation from nuclear wastes

In this paper, we present the case for molecular-recognition approaches for sulfate removal from radioactive wastes via the use of anion-sequestering systems selective for sulfate, using either liquid-liquid extraction or crystallization. Potential benefits of removing sulfate from the waste include improved vitrification of the waste, reduced waste-form volume, and higher waste-form performance, all of which lead to potential cleanup schedule acceleration and cost savings. The need for sulfate removal from radioactive waste, especially legacy tank wastes stored at the Hanford site, is reviewed in detail and primarily relates to the low solubility of sulfate in borosilicate glass. Traditional methods applicable to the separation of sulfate from radioactive wastes are also reviewed, with the finding that currently no technology has been identified and successfully demonstrated to meet this need. Fundamental research in the authors' laboratories targeting sulfate as an important representative of the class of oxoanions is based on the hypothesis that designed receptors may provide the needed ability to recognize sulfate under highly competitive conditions, in particular where the nitrate anion concentration is high. Receptors that have been shown to have promising affinity for sulfate, either in extraction or in crystallization experiments, include hexaurea tripods, tetraamide macrocycles, cyclo[8]pyrroles, calixpyrroles, and self-assembled urea-lined cages. Good sulfate selectivity observed in the laboratory provides experimental support for the proposed molecular-recognition approach.

Anticancer Activity of Self-Assembled Molecular Rectangles via Arene-Ruthenium Acceptors and a New Unsymmetrical Amide Ligand

Two new and large molecular rectangles 4 and 5 were synthesized from two different arene-ruthenium [Ru(2)(μ-η(4)-C(2)O(4))(MeOH)(2)(η(6)-p-Pr(i)C(6)H(4)Me)(2)][O(3)SCF(3)](2) (2), and [Ru(2) (p-cymene)(2) (donq) (OH(2))(2)] [O(3)SCF(3)](2) (donq = 5,8-dioxydo-1,4-naphthaquinonato) (3) acceptors and a new unsymmetrical N-(4-(pyridin-4-ylethynyl)phenyl) isonicotinamide (1) donor ligand. X-ray crystallography of 4 confirmed a molecular rectangle. The (1)H NMR spectra of both rectangles 4 and 5 showed a mixture of two structural, head-to-tail (HTL) and head-to-head (HTH) type, isomers in a 1:1 ratio. The cytotoxicities of both rectangles have been established against Colo320 (colorectal cancer), A549 (lung cancer), MCF-7(breast cancer) and H1299 (lung cancer) human cancer cell lines. The cytotoxicity of rectangle 5 was found to be considerably stronger against all cancer cell lines than that of the reference drug cisplatin.

Recognition and separation of sulfate anions

This tutorial review focuses on some recent aspects in the development of synthetic receptors for selective sulfate anion recognition and separation, with a special emphasis to: (i) receptors for selective recognition of sulfate in organic and aqueous media and (ii) receptors for separation of sulfate from water via liquid-liquid extraction and crystallization.

Self-assembled metallo-macrocycle based coordination polymers with unsymmetrical amide ligands

A series of metallo-macrocyclic based coordination polymers has been prepared from flexible amide ligands N-6-[(3-pyridylmethylamino)carbonyl]-pyridine-2-carboxylic acid (L1-CH(3)) and N-6-[(4-pyridylmethylamino)carbonyl]-pyridine-2-carboxylic acid (L2-CH(3)). In all but one case, self-assembled dinuclear metallo-macrocyclic units form the basis of the polymeric structures, whereby discrete metal centres, and dinuclear or trinuclear clusters, are linked by the self-assembled macrocycles to give 1D and 2D coordination polymers. In one instance, a 1D coordination polymer is formed in a reaction carried out under ambient conditions; when the same reaction is conducted under solvothermal conditions a 2D structure is formed. In all but two of these structures, the polymeric chains and nets are close-packed within the crystals. In the case of a 6,3-connected 2D coordination polymer {[Cd(3)(L2-CH(3))(3)(NO(3))(L2)(CH(3)OH)](NO(3))(2)·12½H(2)O}(n) (9), small oval channels percolate down the a-axis of the unit cell.

Unusual recognition of (n-Bu4N)2SO4 by a cyanuric acid based host via contact ion-pair interactions

A tripodal neutral receptor selectively binds tetrabutylammonium sulfate where anion is encapsulated in the cavity and cations are in close contact with the anion via C-H...O interactions. This organic cation capped sulfate-bowl exists both in solid and solution states and the sulfate assisted cap can be opened and closed reversibly with a temperature key.

Selectivity principles in anion separation by crystallization of hydrogen-bonding capsules

The fundamental factors controlling anion selectivity in the crystallization of hydrogen-bonding capsules [Mg(H2O)6][X [symbol: see text] L2] (X = SO4(2-), 1a; SeO4(2-), 1b; SO3(2-), 1c; CO3(2-), 1d; L = tris[2-(3-pyridylurea)ethyl]-amine) from water have been investigated by solution and solid-state thermodynamic measurements, anion competition experiments, and X-ray structural analysis. The crystal structures of 1a-d are isomorphous, thereby simplifying the interpretation of the observed selectivities based on differences in anion coordination geometries. The solubilities of 1a-d in water follow the order: 1a < 1b < 1c < 1d, which is consistent with the selectivity for the tetrahedral sulfate and selenate anions observed in competitive crystallization experiments. Crystallization of the capsules is highly exothermic, with the most favorable DeltaH(cryst)(o) of -99.1 and -108.5 kJ/mol corresponding to SO4(2-) and SeO4(2-), respectively, in agreement with the X-ray structural data showing shape complementarity between these tetrahedral anions and the urea-lined cavities of the capsules. Sulfite, on the other hand, has a significantly less negative DeltaH(cryst)(o) of -64.6 kJ/mol, which may be attributed to its poor fit inside the capsules, involving repulsive interactions. The more favorable entropy of crystallization for this anion, however, partly offsets the enthalpic disadvantage, resulting in a solubility product very similar to that of the selenate complex. Because of their very similar shape and size, SO4(2-) and SeO4(2-) have a propensity to form solid solutions, which limits the selectivity between these two anions in competitive crystallizations. In the end, a comprehensive picture of contributing factors to anion selectivity in crystalline hydrogen-bonding capsules emerges.