Auxiliary N-donor Ligands Research Articles

Constructing stable uranyl-copper(II) bimetallic organic frameworks using rigid thiophenedicarboxylic acid

By introducing Cu(II) ions as additional connecting nodes to construct stable heterometallic uranyl-organic frameworks (UOFs) with thiophene-2,5-dicarboxylic acid (H2TDC) and N-donor auxiliary ligands, three new uranyl complexes, namely, [Cu(phen)(UO2)(TDC)2] (1), [Cu(phen-NO2)2(UO2)(TDC)2]·3H2O (2), and [Cu(phen-NH2)(H2O)2(UO2)(TDC)2]·4H2O (3) (phen = 1,10-phenanthroline) have been successfully synthesized by hydrothermal reaction. Complex 1 exhibits a rare three-dimensional (3D) network structure of cds topology connected by UO2, Cu(phen), and TDC units. Both complexes 2 and 3 feature similar one-dimensional chain structures based on UO2, TDC, Cu(Phen-NO2)2 and UO2, TDC, Cu(phen-NH2)(H2O)2 respectively. The N-donor auxiliary ligands play a key role in determining their structural dimensionalities and bandgaps formation. Among the three uranyl complexes, phen with a smaller size than its derivatives, phen-NO2 and phen-NH2, was found to be favorable for constructing 3D UOFs. Moreover, complexes with both phen-NO2 and phen-NH2 showed varying degrees of redshift on optical spectra. The UV–Visible diffuse-reflectance spectra, analyzed with Tauc’s fitting in considering Urbach tailing, revealed an indirect bandgap of 2.94 eV, an indirect bandgap of 2.67 eV, and a direct bandgap of 2.45 eV for 1, 2 and 3, respectively. Moreover, thermogravimetric analyses indicate that 3D anhydrous uranyl complex 1 possessed a robust structure and excellent thermal stability above 250 ℃.

Nanoarchitectonics of Four Zn(II)-coordination Polymers Based on 2,5-thiophenedicarboxylic Acid with N-donor Auxiliary Ligands for Detecting of Acetylacetone and Fe3+/Al3+ ions

Nanoarchitectonics of Four Zn(II)-coordination Polymers Based on 2,5-thiophenedicarboxylic Acid with N-donor Auxiliary Ligands for Detecting of Acetylacetone and Fe3+/Al3+ ions

An amine decorated MOF for direct capture of CO2 from ambient air.

A Zn(II)-based metal-organic framework (MOF) was synthesized by the self-assembly of the dicarboxylate ligand terephthalic acid (TPA), 2-aminoterephthalic acid (NH2-TPA) and N-donor auxiliary ligand 1,4-bis(4-pyridinylmethyl)piperazine (bpmp) using Zn(NO3)2·6H2O under hydrothermal conditions. {[Zn(TPA)0.5(NH2TPA)0.5(bpmp)]·DMF·7H2O}n (framework 1) has an sra topology with a BET surface area of 756 m2 g-1. The microporous nature of the framework is apparent from the significant CO2 adsorption capacities observed at various temperatures: 57 cc g-1 at 283 K, 46 cc g-1 at 293 K, 37 cc g-1 at 303 K, and 30 cc g-1 at 313 K. The considerable CO2 adsorption may be caused by the existence of free carboxylate and amine substituents that interact with the gas molecules and micropores. At room temperature, the activated MOF readily converts CO2 into cyclic carbonates when a suspension of the MOF is bubbled with ambient air and different epoxides under solvent-free conditions. The amine groups located within the pores of the MOF interact with CO2 molecules, enhancing their sorption and conversion to cyclic carbonates. However, due to interpenetration within framework 1, only smaller size epoxides can be accommodated and converted to cyclic carbonates in good yields. Additionally, the effectiveness of the catalyst is further confirmed by the positive outcomes obtained from the hot filtration control test. Grand canonical Monte Carlo (GCMC) molecular simulations were utilized to gain a better understanding of molecular interactions. GCMC results are in line with the experiments. The substantial adsorption of CO2 can be ascribed to the strong intermolecular interactions that occur between the amine groups within the framework and the CO2 molecules.

Impact of N-donor auxiliary ligands on three new Co(ii)-based coordination polymers with symmetrical tetracarboxylate ligands: a magnetism study

Three new Co(ii) coordination polymers (1–3) have been successfully synthesized. 1 and 3 display a 3D framework with (4,6)-connected CrB-type topology, 2 displays a 1D chain. 1–3 all have antiferromagnetic interactions in the Co(ii) unit.

New Cu(II)-based three dimensional supramolecular coordination polymer as photocatalyst for the degradation of methylene blue

A new Cu(II)-based coordination polymer [Cu2(HL)2(bib)2] (1) has been synthesized by reacting two flexible linkers viz. 5-(4ˊ-carboxylphenoxy)isophthalic acid (H3L) and 1,1′-(1,4-butanediyl)bis(imidazole) (bib) a N-donor auxiliary ligand with CuSO4 under solvothermal condition. The single crystal X-ray analysis indicates that 1 possess 2D layered network, which further extends into 3D supramolecular framework through hydrogen bonding interactions. The coordination polymer 1 has been used as photocatalyst for the sustainable degradation of model aromatic dyes viz. methylene blue (MB), Rhodamine B (Rh B) and methylene orange (MO). The experiments demonstrate that 1 exhibits recyclable and better photocatalytic activity for photodegradation of MB (62.96%) than Rhodamine B (Rh B) and methylene orange (MO) in time span of 100 min. Furthermore, trapping experiments using scavengers indicate that hydroxyl radicals are the main species responsible for photocatalytic degradation of MB. Apart from this computational investigation has been executed to propose the plausible mechanism of photocatalysis.

On the importance of π-stacking interactions in the complexes of copper and zinc bearing pyridine-2,6-dicarboxylic acid N-oxide and N-donor auxiliary ligands

Using N- and O-donor ligands in a mixed-ligand system, three new coordination complexes have been X-ray characterized, exhibiting strong π–π stacking interactions.

Impact of N-donor auxiliary ligands on two new Co(ii)-based MOFs with N-heterocyclic ligands and a magnetism study

These current results show that the use of Co(ii)-MOF chemistry, especially in the presence of various auxiliary linkers, is an efficient method to prepare multifunctional MOFs combining new outstanding structures and excellent properties.

3D Uranyl Organic Frameworks Supported by Rigid Octadentate Carboxylate Ligand: Synthesis, Structure Diversity, and Luminescence Properties.

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH4 ][(UO2 )3 (HTTDS)(H2 O)] (1), [(UO2 )4 (HTTDS)2 ](HIM)6 (2, IM=imidazole), [(UO2 )4 (TTDS)(H2 O)2 (Phen)2 ] (3, Phen=1,10-phenanthroline), [Zn(H2 O)4 ]0.5 [(UO2 )3 (HTTDS)(H2 O)4 ] (4), and {(UO2 )2 [Zn(H2 O)3 ]2 (TTDS)} (5), {Zn(UO2 )2 (H2 O)(Dib)0.5 (HDib)(HTTDS)} (6, Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO2 )4 [Cu3 (u3 -OH)(H2 O)7 ](TTDS)2 } (7) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H8 TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO7 pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO2 ]2+ units as co-ligands. The second metal centers were introduced in the syntheses of 4-7, and in all cases, they are part of the final structures, either as a counterion (4) or as a component of framework (5-7). Interesting, in 7, a rare polyoxometalate [Cu3 (μ3 -OH)O7 (O2 CR)4 ] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO2 )2 (O2 CR)4 ] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail.

A family of coordination polymers derived from a flexible dicarboxylic acid and auxiliary N-donor ligands: solvothermal synthesis, crystal structure and dye adsorption properties

Four novel coordination polymers [Cd2(oba)2(phen)2]n (1), [Mn3(oba)3(phen)2]n (2), [Zn(oba)(phen)]n (3) and [Mn(oba)(dmphen)]n (4) (H2oba = 4,4′-oxybis (benzoic acid), phen = 1,10-phenanthroline, dmphen = 2,9-dimethyl-1,10-phenanthroline) have been synthesized by the solvothermal method and then characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectrum, UV–Vis spectroscopy and thermogravimetric analysis. Structural analysis suggests that complex 1 displays a 1D ribbon-like structure, which extends into a 2D supramolecular layer by intermolecular π⋯π stacking. For complex 2, the trinuclear building unit of [Mn3(oba)3(phen)2] bridged by the oba2− ligands leads to the formation of a 3D supramolecular network. Complex 3 adopts a mononuclear and 1D zigzag chain structure and also extends into a 2D supramolecular network by intermolecular π⋯π stacking. Complex 4 shows 1D infinite double-chain structures which are shaped by intermolecular π⋯π stackings. Photoluminescent properties of complexes 1 and 3 in solid state were also studied. In addition, complex 2 exhibits high performance in the selective adsorption of Congo red (CR) with an adsorption capacity of 64.4 mg g−1.

Seven new metal-organic frameworks assembled from semi-rigid polycarboxylate and auxiliary N-donor ligands: syntheses, structures and properties.

Seven new metal-organic frameworks (MOFs), namely, [Zn2(L1)(H2O)3]n (1), [Zn2(L1)(dib)(H2O)2]n (2), {[Zn2(L1)(4,4'-bipy)(H2O)2]·H2O}n (3), [Cd2(L1)(1,10-phen)]n (4), [Ni2(HL1)(4,4'-bipy)(μ3-OH)(μ2-H2O)]n (5), {[Co4(L1)(4,4'-bibp)3]·(4,4'-bibp)3}n (6), and [Co2(L2)(4,4'-bibp)2(H2O)]n (7), where H4L1 and H4L2 are semi-rigid 3-(3,5-dicarboxylphenoxy)phthalic acid and 4-(3,5-dicarboxylphenoxy)phthalic acid, respectively, and 4,4'-bipyis 4,4'-bipyridine, dibis 1,4-bis(1H-imidazol-1-yl)benzene, 1,10-phenis 1,10-phenanthroline and 4,4'-bipbis 1,4-bis(pyridin-4-yl)benzene, have been prepared under solvothermal conditions with ZnII, CdII, CoII and NiII ions in the presence of auxiliary N-donor ligands. The crystal structures and photoluminescence and magnetic properties of these compounds have been investigated. Compound 1 displays a 3,4,6-connected two-dimensional (2D) topology with a Schläfli symbol of (42.5)2(43.52.7)(45.56.63)2, and the 2D structure was further assembled to form a three-dimensional (3D) framework by intermolecular O-H...O hydrogen bonds. Compound 2 features a novel 3,3,4-connected structure and the point symbol is (4.102)(4.6.84)(62.8). Compound 3 exhibits a 3,4,6-connected 3-nodal net having a 3,4,6 T53 type topology, with the point symbol (4.62)2(42.64)2(42.68.82.103). Compound 4 shows a 2D→3D supramolecular structure formed by π-π stacking interactions. Compound 5 possesses a 3D framework with a tfz-d net topology. Compounds 6 and 7 are constructed from the same auxiliary ligand and metal salt at the same temperature, but with different main ligands and exhibiting different topologies. Compound 6 presents a 3D 4,6-connected topological network with a Schläfli symbol of (3.44.6)(32.44.56.63), while compound 7 has a 3D topological network with a Schläfli symbol of (412.616). Magnetic analyses indicate that compounds 5 and 7 show weak antiferromagnetic interactions.

3D semiconducting Co-MOFs based on 5-(hydroxymethyl)isophthalic acid and imidazole derivatives: syntheses and crystal structures.

Two three-dimensional cobalt-based metal-organic frameworks with 5-(hydroxymethyl)isophthalic acid (H2HIPA), namely poly[[μ2-1,4-bis(2-methyl-1H-imidazol-1-yl)benzene-κ2N3:N3'][μ2-5-(hydroxymethyl)isophthalato-κ2O1:O3]cobalt(II)], [Co(C9H6O5)(C14H14N4)]n (1), and poly[tris[μ2-1,4-bis(1H-imidazol-1-yl)benzene-κ2N3:N3']bis[μ3-5-(hydroxymethyl)isophthalato-κ2O1:O3:O5]dicobalt(II)], [Co2(C9H6O5)2(C12H10N4)3]n (2), were synthesized under similar hydrothermal conditions. Single-crystal X-ray diffraction analyses revealed that 5-(hydroxymethyl)isophthalate (HIPA2-) and 1,4-bis(2-methyl-1H-imidazol-1-yl)benzene (1,4-BMIB) are simple linkers connecting cobalt centres to build a fourfold interpenetration dia framework in complex 1. However, complex 2 is a pillared-layer framework with a (3,6)-connected network constructed by 1,4-bis(1H-imidazol-1-yl)benzene (1,4-DIB) linkers, 3-connected HIPA2- ligands and 6-connected CoII centres. The above significant structural differences can be ascribed to the introduction of the different auxiliary N-donor ligands. Moreover, UV-Vis spectroscopy and Mott-Schottky measurements confirmed that complexes 1 and 2 are typical n-type semiconductors.

Dynamic porous coordination polymers built-up from flexible 4,4'-dithiodibenzoate and rigid N-based ligands.

Herein we report the design, synthesis, structural characterisation and functional testing of a series of Cu(ii) coordination polymers containing flexible 4,4'-dithiodibenzoate ligand (4,4'-DTBA), with or without auxiliary N-donor ligands. Reaction of Cu(ii) with 4,4'-DTBA yielded a 1D coordination polymer (1) based on Cu(ii) paddlewheel units connected by 4,4'-DTBA, to form cyclic loop chains with intramolecular voids that exhibit reversible structural transformations upon subsequent solvent exchange in methanol to afford a new, crystalline, permanently-porous structure (1'). However, when the same reaction was run with pyridine, it formed a porous 2D coordination polymer (2). We have attributed the difference in dimensionality seen in the two products to the coordination of pyridine on the axial site of the Cu(ii) paddle-wheel, which forces flexible 4,4'-DTBA to adopt a different conformation. Reactions in the presence of 4,4'-bipyridine (4,4'-bpy) afforded two new, flexible, 2D coordination polymers (3 & 4). Lower concentrations of 4,4'-bpy afforded a structure (3) built from 1D chains analogous to those in 1 and connected through 4,4'-bpy linkers coordinated to the axial positions. Interestingly, 3 showed reversible structural transformations triggered by either solvent exchange or thermal treatment, each of which yielded a new crystalline and permanently porous phase (3'). Finally, use of higher concentrations of 4,4'-bpy led to a coordination polymer (4) based on a distorted CuO3N2 trigonal bipyramid, rather than on the Cu(ii) paddlewheel. The connection of these motifs by 4,4'-DTBA resulted in a zig-zag 1D chain connected through 4,4'-bpy ligands to form a porous 2D network. Interestingly, 4 also underwent reversible thermal transformation to yield a microporous coordination polymer (4').

Two cobalt(II) coordination polymers based on 5-i-butoxyisophthalate and dipyridyl: Syntheses, structures and efficient oxygen evolution reaction

Two new cobalt(II) clusters based 3D metal-organic frameworks (MOFs) [Co2(iBuOip)2(bpa)2(H2O)] (1) and [Co5(iBuOip)4(μ3-O)(bpp)2(DMF)(H2O)3]·2H2O (2) (iBuOip = 5-i-butoxyisophthalate, bpp = 1,3-bis(4-pyridyl)propane and bpa = 1, 2-bi(4-pyridyl)ethane), were synthesized with 5-i-butoxyisophthalate and bpp/bpa mixture ligands. Compound 1 shows a 3D network constructed from both a dinuclear cluster and mononuclear Co(II) nodes. The mixture of triangular trinuclear and rhombus tetranuclear cluster nodes linked by 5-i-butoxyisophthalate and bpp give rise to a 3D pillared-layer structure of 2. The structural and topological differences of the two complexes demonstrate that the characteristics of the N-donor auxiliary ligands play significant roles in constructing the novel architectures of coordination polymers. Electrochemical measurements reveal that 2 modified electrode is catalytically active to oxygen evolution reaction with a lower overpotential of only 340 mV at 10 mA cm-2 in neutral solution.

Four novel Co(II) metal-organic frameworks based on semi-rigid ligand and their secondary building units transformation

Four novel 3D Co(II)-containing metal–organic frameworks (MOFs), namely [Co(ADDA)] (1), [Co(ADDA)(bipy)]·1.5H2O (2), [Co0.5(HADDA)(bipy)0.5] (3) and [Co(ADDA)(bipy)0.5] (4) (H2ADDA = 3,3'-(anthracene-9,10-diyl)diacrylic acid, bipy = 4,4′-bipyridine), have been successfully obtained based on reasonable synthetic strategies. N-donor auxiliary ligand, reaction medium and reaction temperature jointly induce interesting transformation of secondary building unit (SBU), resulting in structure diversities and topology variations. Notably, by increasing the reaction temperature in the mother liquid, 4 with {Co2(COO)4} paddle-wheel SBU can be generated by the single-crystal to single-crystal transformation of 3 with mononuclear {CoO4} SBU. Furthermore, the magnetic properties and electrocatalytic activities of these four Co-MOFs are also investigated in detail.

Three coordination polymers based on 3-(3′,5′-dicarboxylphenoxy)phthalic acid and auxiliary N-donor ligands: syntheses, structures, and highly selective sensing for nitro explosives and Fe3+ ions

Three coordination polymers have been synthesized and compound 1 shows highly selective sensing for 2,4-dinitrophenol and Fe3+ ions.

Comparative Study on Temperature-Dependent CO2 Sorption Behaviors of Two Isostructural N-Oxide-Functionalized 3D Dynamic Microporous MOFs.

By functionalization of the achiral carboxylate-based pyridine-N ligand 2,2'-bipyridine-3,3'-dicarboxylate (H2bpda) with N-oxide groups, the axially chiral ligand 2,2'-bipyridine-3,3'-dicarboxylate 1,1'-dioxide (H2bpdado) has been obtained. On the basis of H2bpdado and auxiliary N-donor ligands, two isostructural 3D dynamic porous Cu(II) metal-organic frameworks (MOFs), {[Cu0.5(bpdado)0.5(L)0.5]·3H2O}n (L = 1,2-bis(4-pyridyl)ethane (bpa), trans-1,2-bis(4-pyridyl)ethene (bpe) for 1 and 2, respectively), have been synthesized, which contain N-oxide "open donor sites" (ODSs) and carboxyl sites on the pore surfaces. The modification of pyridine-N into the N-oxide group not only transforms the nonporous structure into a porous framework but also endows the N-oxide group with unique charge-separated plus electron-rich character, which may provide an enhanced affinity toward CO2 molecules. Interestingly, both 1 and 2 present reversible structural transformation upon dehydration and rehydration. The adsorption properties of 1 and 2 have been investigated by N2, H2, CH4, and CO2 gases, and they reveal evident adsorption for CO2 and CH4. Both MOFs have high CO2 uptake, CO2 sorption affinity, and sorption selectivities of CO2 over CH4 and N2. Remarkably, 1' and 2' exhibit intriguingly comparable temperature-dependent CO2 sorption behaviors that can probably be attributed to the difference in bpa and bpe. First, at 195 K, 1' and 2' exhibit stepwise adsorption and hysteretic desorption behavior for CO2, but in the second step, the isotherms of 2' display a starting pressure greater than that of 1'. Then, at 298 K, their CO2 isotherms all show nonclassical type I adsorption, while peculiarly, at 273 K, the CO2 isotherm of 1' still exhibits uncommon stepwise adsorption but that of 2' does not. Thus, these temperature-dependent CO2 sorption behaviors indicate that there exist different threshold temperatures and pressures of channel expansion for 1' and 2'.

Construction of structurally diverse luminescent lead(ii) fluorinated coordination polymers based on auxiliary ligands

Four novel Pb(ii) fluorinated coordination polymers were obtained by hydrothermal reaction of lead nitrate with 2,4,5,6-tetrafluoroisophthalic acid (H2TFIPA) in the presence of corresponding N-donor auxiliary ligands and photoluminescent properties of the all complexes have also been investigated.

Homochiral Metal–Organic Frameworks Embedding Helicity Based on a Semirigid Alanine Derivative

Five novel homochiral metal–organic frameworks (HMOFs) have been synthesized using a semirigid alanine-derived ligand and varied auxiliary N-donor ligands, namely, [Cu2(TMAla)2(bipy)2]·10H2O (1) and [Cu(TMAla)(bpea)0.5(H2O)]·H2O (2), Ln(TMAla)(HTMAla)(phen) (Ln = Eu, 3; Tb, 4; Gd, 5), where H2TMAla = terephthaloyl-mono(l-alanine), bipy = 4,4′-bipyridine, bpea = 1,2-bis(4-pyridyl)ethane, phen = 1,10-phenanthroline. Crystallographic analysis indicates that all the complexes contain homochiral left- and/or right-handed helical chains, which are constructed by TMAla fragments and metal ions. Meanwhile, the introduction of auxiliary N-donor ligands gives rise to the formation of HMOFs with different structural topologies. Complex 1 shows a three-dimensional (3D) quartz-dual net with a 4-connected (75·9) topology in the presence of bipy. Complex 2 possesses a novel 3D pillared-layer framework with a (3,4,4)-connected (6·104·12)(63)2(64·102) topology by using bpea instead of bipy. Complexes 3–5 are isomorphous a...

Three zinc coordination polymers constructed from 5-(4-carboxybenzyloxy)isophthalic acid: Synthesis, structures, and luminescence sensing

By altering auxiliary N-donor ligands, three ZnII compounds, [Zn(HL)(biz)] (1), [Zn2(μ3-OH)(L)(bpy)]·2H2O (2) and [Zn2(HL)2(bimb)2]·H2O (3) (H3L=5-(4-carboxybenzyloxy)isophthalic acid, biz=benzimidazole, bpy=2,2′-bipyridine, bimb=1,4-bis((1H–imidazol-1-yl)methyl)benzene), were obtained under hydrothermal conditions. Compound 1 and 3 are 2D layer 4-connected net. Compound 2 is a 2D sheet structure and (3,6)-connected net with (43)(46·66·83) topology. In addition, compound 3 demonstrates high sensitivity in the detection of nitroaromatic explosives as a fluorescent sensor.

A series of transition metal coordination polymers with mixed ligands: Specific sensing and removal of metal ions

Starting from the transition metal salts and mixed organic ligands of 4,4′-{[1,2-phenylenebis-(methylene)]bis(oxy)}dibenzoic acid (H2L) and different N-containing linkers, six new coordination polymers, [Cd(L)(2,2′-bipy)]n (1); [Cu(L)(2,2′-bipy)]n (2); {[Zn(L)(4,4′-bipy)][Zn(L)(H2O)]}n (3); [Cu(L)(4,4′-bipy)0.5 (H2O)]n (4), [Zn2(L)2(bpp)]n (5) and [Cd3(L)2(OAc)2(Him)2]n (6) (2,2′-bipy=2,2′-bipyridine, 4,4′-bpy=4,4′-bipyridine and bpp=1,3-bis(4-pyridyl)propane), were synthesized and characterized. The structural differences of 1–6 indicate the effect of the auxiliary N-donor ligands and nature of metal centers could modulate the resulting architectures. The photoluminescent sensing behaviours of 1 and 5 toward Cu2+ cation and nitro explosives have been investigated in detail. Interestingly, the immobilized Cu2+ cation can be easily separated by ethylenediaminetetraacetic acid (EDTA).