Three-dimensional Supramolecular Architecture Research Articles

Crystal structure and Hirshfeld surface analysis of tris-(acetohydrazide-κ2 N,O)(nitrato-κO)(nitrato-κ2 O,O')terbium(III) nitrate.

In the title lanthanide(III) compound, [Tb(NO3)2(C2H6N2O)3]NO3, the asym-metric unit contains one Tb3+ ion, three acetohydrazide (C2H6N2O) ligands, two coordinated nitrate anions, and an isolated nitrate anion. The Tb3+ ion is in a ninefold coordinated distorted tricapped trigonal-prismatic geometry formed by three oxygen atoms and three nitro-gen atoms from three different acetohydrazide ligands and three oxygen atoms from two nitrate anions. In the crystal, the complex mol-ecules and the non-coordinated nitrate anions are assembled into a three-dimensional supra-molecular architecture through extensive N-H⋯O hydrogen-bonding inter-actions between the amine NH groups of the acetohydrazide ligands and the nitrate oxygen atoms. Hirshfeld surface analysis was performed to aid in the visualization of inter-mol-ecular contacts.

Thermodynamics and Catalytic Properties of Two Novel Energetic Complexes Based on 3-Amino-1,2,4-triazole-5-carboxylic Acid.

For energetic materials (EMs), the key point of the present research is to improve the energetic property and reduce sensitivity. In this work, two new energetic complexes, Mn(atzc)2(H2O)2·2H2O (1) and Zn(atzc)2(H2O) (2) (Hatzc = 3-amino-1,2,4-triazole-5-carboxylic acid), were synthesized by solvent evaporation and diffusion methods, respectively. The structural analyses illustrate that 1 and 2 exhibit zero-dimensional structural units, which are linked by hydrogen-bonding interactions to give three-dimensional supramolecular architectures. For complexes 1 and 2, the detonation velocities (D) are 10.4 and 10.2 km·s–1 and detonation pressures (P) are 48.7 and 48.6 GPa, respectively. They are higher than most of the reported EMs, which present prominent detonation characteristics. In addition, two complexes can accelerate the thermal decomposition of ammonium perchlorate and exhibit excellent catalytic activity. Therefore, the two complexes can serve as a new class of promising EMs, which have potential application in the design of new high-efficiency solid catalysts.

Synthesis, characterization, crystal structure and antibacterial activity studies of cobalt(II) and zinc(II) complexes containing halogen quinoline Schiff base ligand

This work presented the synthesis, characterization and biological activity of Co(II) and Zn(II) complexes derived from 4‑chloro-2-((quinolin-6-ylimino)methyl)phenol (HL), their structures were characterized using IR, NMR and single-crystal X-ray diffraction. The HL was crystallized in the orthorhombic crystal systems, space groups of Pccn, and two HL molecules contained its smallest asymmetric unit. The self-assembly of HL with metal (II) (M=Co, Zn) led to the formation of CoL2 (1) and ZnL2 (2) by solvothermal method in methanol-water system. The basis of spectroscopic techniques, single-crystal X-ray diffraction and powder X-ray diffraction analysis further revealed that 1 and 2 were isomorphous with similar coordination mode and similar structural features. The introduction of a chlorine atom and C=N group to the ligand facilitated the collaboration of electrostatic interaction, hydrogen bonding, π⋯π stacking interaction and the rare C—H⋯Cl interaction, which resulted in the formation of three-dimensional supramolecular architectures. The synthesized complexes exhibited significant antimicrobial activity when evaluated against six phytopathogenic fungi, 2 exhibited a wider range antimicrobial activity compared to HL and 1.

Supramolecular structure and spectroscopic characterization of new 1,3,5-triaza-2-boracyclohex-3-en derivative formed under mild conditions between 2-imino-4-thiobiuret and boric acid

Reaction of 2-imino-4-thiobiuret with boric acid (in molar ration of 1:1) in aqueous solution at the mild conditions leads to formation of a heterocyclic compound of 2,2-dihdroxy-4-amino-6-thio-1,3,5-trihydrotriaza-2-boracyclohex-3-en (1). This compound crystallizes directly from the reaction solution after a few days, giving light yellowish transparent monoclinic crystals (P21/n). X-ray single crystal analysis shows that the heteroring and the thio- and amine groups are co-planar, whereas the plane of hydroxyl groups linked to boron are almost perpendicular to plane of the ring. The 2,2-dihdroxy-4-amino-6-thio-1,3,5-trihydrotriaza-2-boracyclohex-3-en molecules are arrangement via O–H...S hydrogen bonds in the stacks along b-axis, and the stacks are interacting each other via N–H...O hydrogen bonds forming a three-dimensional supramolecular architecture. The qualitative and quantitative intermolecular interactions in the crystal were analyzed using the Hirshfeld surface and 2D-fingerprint plots. The compound was also characterised by the FT-IR and Raman spectroscopy. The IR and FT-Raman spectra were made for protiated (1) and its deuterated analogue (1d). The IR and FT-Raman spectra for molecule in the gas-phase were calculated using DFT. DFT calculations and the isotropic frequency shift are helpful in assignments of the vibration bands. The calculated HOMO and LUMO energy gap explain the charge transfer interactions taking place within the molecule.

Synthesis and crystal structure of catena-poly[[hexa-aqua{μ3-2-[bis-(carboxyl-atometh-yl)amino]-terephthalato}dicobalt(II)] penta-hydrate] containing water tapes and penta-mers.

The title coordination polymer, {[Co2(C12H7NO8)(H2O)6]·5H2O} n , was crystallized at room temperature from an aqueous solution of 2-aminodi-acetic terephthalic acid (H4adtp) and cobalt(II) nitrate. The asymmetric unit consists of one adtp4- ligand, one and two half CoII ions, six water ligands coordinated to CoII ions and five uncoordinated water mol-ecules. Two of the cobalt cations lie on centres of inversion and are coordinated in octa-hedral O2(OH2)4 environments, whereas the other adopts a slightly distorted octa-hedral NO3(OH2)2 environment. The crystal structure contains parallel stacked, one-dimensional zigzag chains, {[Co2(C12H7NO8)(H2O)6]} n , which assemble into a three-dimensional supra-molecular architecture via networks of hydrogen bonds involving the coordinated and free water mol-ecules. One-dimensional 'water tapes' are formed, containing alternating six-membered and twelve-membered rings of water mol-ecules, together with water penta-mers, in which a central uncoordinated water mol-ecule is hydrogen bonded to two coordinated and two free water mol-ecules in a tetra-hedral arrangement.

Synthesis, structural characterization and prospects for a new tris (5-methylbenzimidazole) tris (oxalato) ferrate(III) trihydrate complex as a promising antibacterial and antifungal agent

A new mononuclear complex (C8H9N2)3[Fe(C2O4)3].3H2O was synthesized via a conventional solution method and characterized by FT-IR and UV–visible spectroscopy, followed by thermal analysis and single crystal X-ray diffraction. The molecular structure of the complex reveals [Fe(C2O4)3]3− octahedral anions and 5-methylbenzimidazole (C8H9N2)+ cations, which are connected together through uncoordinated water molecules via O/NH⋯O hydrogen bonds. Face-to-face interactions (π–π stacking) between identical organic cations and O/NH⋯O hydrogen bonding lead to the formation of a three-dimensional supramolecular architecture. The optical absorbance of the complex was identified from a UV–visible study, showing an optical energy gap of 3.56 eV. The thermal property was evaluated by thermogravimetric analysis. The antibacterial effects of the synthesized iron(III)complexhave also been examinedin vitroagainst clinical bacterial strains: two Gram-positive and four Gram-negative, using the disk diffusion and macro-dilution broth methods. The obtained results show that the Fe(III)complexexhibits a marked antibacterial activity, associated with lysozyme and anti-biofilm potential. Furthermore, the results of antifungal studies by the agar well diffusion method demonstrated that our complex possesses higher activity against Candida albicans than the standards Amphotericin B and Fluconazole 25, which showed zone of inhibition diameters of about 19 and 13 mm, respectively, compared to 20 mm given by the new iron complex.

Dimethyl 3,3'-[(4-nitro-phen-yl)methyl-ene]bis-(1H-indole-2-carboxyl-ate) ethanol hemisolvate.

There are two main molecules in asymmetric unit of the title compound, C27H21N3O6·0.5C2H5OH. In both, the indole ring systems are approximately perpendicular to each other, at dihedral angles of 69.3 (5) and 82.8(4)°. In the crystal, mol-ecules are linked by N-H⋯O and O-H⋯O hydrogen bonds into a three-dimensional supra-molecular architecture. The solvent ethanol mol-ecule acts as a donor, forming an O-H⋯O hydrogen bond, reinforcing the structure.

The coordination chemistry of benzhydrazide with lanthanide(iii) ions: hydrothermal in situ ligand formation, structures, magnetic and photoluminescence sensing properties.

The influence of synthetic conditions on the solid-state structural formation of lanthanide(iii) complexes based on a hydrazide ligand have been investigated and reported. Depending on the solvents and reaction temperatures, the reactions of hydrated Ln(NO3)3 with a benzohydrazide (bzz) ligand afforded three classes of lanthanide(iii) coordination complexes viz. [Ln(bzz)(NO3)](NO3)2 (1Ln; Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5)), [Ln(bzz)(ben)3(H2O)]·H2O (2Ln; Ln = Pr (6), Nd (7), Sm (8), Eu (9), Gd (10), Tb (11), Dy (12), Er (13)), and [Ln3(ben)3] (3Ln; Ln = Eu (14), Gd (15), Tb (16), Dy (17), Er (18), Tm (19), Yb (20), Lu (21)). Complexes 1–5 in series 1Ln were isolated by slow evaporation of their isopropanol solutions at ambient temperature, and the complexes display similar discrete structures bearing distinct intermolecular N–H⋯O hydrogen bonds to generate a three-dimensional (3D) supramolecular architecture. Complexes 6–13 in series 2Ln were obtained under hydrothermal conditions at 110 °C where the in situ generated benzoate (ben) ligands participated in the formation of one-dimensional (1D) coordination polymers (CPs) with the bzz ligands. At a temperature of 145 °C the hydrothermal conditions result in the formation of the thermodynamically more stable products of 14–21 in series 3Ln, in which the bzz ligand underwent complete in situ hydrolysis to create the ben ligand. These coordination assemblies feature 1D zigzag chains that are formed by unusual low coordination numbers of the six- and seven-fold coordinated Ln3+ centers bridged by the ben ligands in μ2- and μ3-coordination modes. Notably, the chain structures of 2Ln can be transformed into the zigzag tape-like structures of 3Ln upon heating the crystalline samples to 400 °C in air. In the solid state at room temperature, the Eu- (2, 9, 14) and Tb- (4, 11, 16) containing complexes emit red and green light, respectively. The luminescence investigations show that the Eu- (9, 14) and Tb-(11, 16) based CPs could be used as fluorescent probes for acetone and Co2+ ions via an energy competition mechanism. Meanwhile, the Gd- (10, 15) and Dy- (12, 17) based CPs show typical antiferromagnetic interactions.

From Distinct Metallopeptoids to Self-Assembled Supramolecular Architectures.

The construction of synthetic protein mimics is a central goal in chemistry. A known approach for achieving this goal is the self-assembly of synthetic biomimetic sequences into supramolecular structures. Obtaining different 3D structures via a simple sequence modification, however, is still challenging. Herein we present the design and synthesis of biomimetic architectures, via the self-assembly of distinct copper-peptoid duplexes. We demonstrate that changing only one non-coordinating side-chain within the peptoids-sequence-specific N-substituted glycine oligomers-leads to different supramolecular structures. Four peptoid trimers incorporating 2,2'-bipyridine and pyridine ligands, and a non-coordinating but rather a structure-directed bulky group were synthesized, and their solutions were treated with Cu2+ in a 1:1 ratio. Single-crystal X-ray analysis of the products revealed the self-assembly of each peptoid into a metallopeptoid duplex, followed by the self-assembly of multiple duplexes and their packing into a three-dimensional supramolecular architecture via hydrogen bonding and π-π interactions. Tuning the non-coordinating side-chain enables to regulate both the final structure being either a tightly packed helical rod or a nano-channel, and the pore width of the nano-channels. Importantly, all the metallopeptoids structures are stable in aqueous solution as verified by cryo-TEM measurements and supported by UV/Vis and EPR spectroscopies and by ESI-MS analysis. Thus, we could also demonstrate the selective recognition abilities of the nano-channels towards glycerol.

Synthesis, molecular structure and BSA-binding properties of a new binuclear Cd(II) complex based on 2-(1H-tetrazol-1-methyl)-1H-imidazole-4,5-dicarboxylic acid

Abstract A new binuclear Cd(II) complex, [Cd2(H2tmidc)4(H2O)2]·6H2O (1) based on 2-(1H-tetrazol-1-methyl)-1H-imidazole-4,5-dicarboxylic acid (H3tmidc) has been synthesized and structurally characterized. The single-crystal X-ray diffraction analysis has revealed that there are two crystallographically distinct H2tmidc– anions in complex 1, one of which is coordinated to Cd(II) ion in a terminal fashion, while the other acts as a bis-connector linking two Cd(II) cations to form the dinuclear structure. The dimeric units are stabilized by intra-molecular O–H···O hydrogen bonds and π-π stacking interactions and are further connected into a three-dimensional supramolecular architecture through inter-molecular hydrogen bonds and π-π stacking interactions. The interactions of complex 1 with bovine serum albumin (BSA) were analyzed by fluorescence measurements under physiological conditions. The results have indicated that the fluorescence intensity of BSA was decreased considerably upon the addition of complex 1 through a static quenching mechanism. The synchronous fluorescence spectrum suggested that the interaction of complex 1 with BSA affects the conformations of tryptophan and tyrosine residues and thereby has an influence on the conformation of BSA.

Crystal structures and magnetic properties of two isomorphic nickel(II) and cobalt(II) coordination polymers-based nitrogen-heterocyclic tricarbolylate ligands

5-(3,4-Dicarboxylphenyl) picolinic acid (H3dppa) was applied as a new building block for the synthesis of two isomorphic coordination polymers, namely [Ni1.5dppa(H2O)3]n·nH2O (1), [Co1.5dppa(H2O)3]n·nH2O (2). Two compounds were generated by a hydrothermal self-assembly method using the corresponding metal(II) acetates and H3cppa ligand. Structure analysis reveals that compounds 1 and 2 are isomorphic both featuring a two-dimensional wave structure and are finally extended into the three-dimensional supramolecular architecture though hydrogen bonding interactions. Magnetic susceptibility measurements indicate that domain a weak ferromagnetic exchange coupling between the adjacent Ni(II) centers in 1, and a weak antiferromagnetic coupling between Co(II) ions in for 2.

A Survey of Supramolecular Aggregation Based on Main Group Element⋯Selenium Secondary Bonding Interactions—A Survey of the Crystallographic Literature

The results of a survey of the crystal structures of main group element compounds (M = tin, lead, arsenic, antimony, bismuth, and tellurium) for intermolecular M⋯Se secondary bonding interactions is presented. The identified M⋯Se interactions in 58 crystals can operate independent of conventional supramolecular synthons and can sustain zero-, one-, two, and, rarely, three-dimensional supramolecular architectures, which are shown to adopt a wide variety of topologies. The most popular architecture found in the crystals stabilized by M⋯Se interactions are one-dimensional chains, found in 50% of the structures, followed by zero-dimensional (38%). In the majority of structures, the metal center forms a single M⋯Se contact; however, examples having up to three M⋯Se contacts are evident. Up to about 25% of lead(II)-/selenium-containing crystals exhibit Pb⋯Se tetrel bonding, a percentage falling off to about 15% in bismuth analogs (that is, pnictogen bonding) and 10% or lower for the other cited elements.

Dual-emitting barium based metal-organic nanosheets as a potential sensor for temperature and anthrax biomarkers

The development of novel 2D materials, due to the promising applications they have enabled through their unique properties, has attracted increasingly more research interest. In this regard, novel dual-emitting coordination polymer nanosheets were developed by doping Eu3+ and Tb3+ ions into the nanostructures of the [Ba(DPA)2(H2O)2]n (DPA = dipicolinic acid) coordination polymer (BCP). Single crystal x-ray crystallography revealed that BCP is a 1D coordination polymer and its three-dimensional supramolecular architecture is constructed with a relatively strong hydrogen bonding in the ac crystallographic plane and weak non-covalent interactions along the b axis. Using energetic ultrasound irradiations, synthesis of nanoscale BCP along with the unzipping of the weak interactions between the ac layers was accomplished. The resulting BCP nanosheets was used as the host lattice and was doped with Eu3+ and Tb3+ ions. Remarkably, the sensing ability of both Eu3+ and Tb3+ doped coordination polymer (Ln@BCP) nanosheets towards temperature and the DPA anthrax biomarker were investigate. The high relative sensitivity value of 2.42% K−1 and their reusability, makes Ln@BCP nanosheets an ideal candidate for the nanothermometry. They also exhibited high selective detection characteristics towards the DPA anthrax biomarker with a 0.03 nM detection limit. Therefore, Ln@BCP nanosheets can also be considered as an efficient multi-responsive optical sensor.

One-pot concomitant preparation of two copper(II) coordination polymers with different configurations of bridging bithiophene ligands.

By employing the conjugated bithiophene ligand 5,5'-bis(1H-imidazol-1-yl)-2,2'-bithiophene (bibp), which can exhibit trans and cis conformations, two different CuII coordination polymers, namely, poly[[μ-5,5'-bis(1H-imidazol-1-yl)-2,2'-bithiophene-κ2N:N'](μ2-4,4'-oxydibenzoato-κ2O:O')copper(II)], [Cu(C14H8O5)(C14H10N4S2)]n or [Cu(bibp)(oba)]n, (I), and catena-poly[μ-aqua-bis[μ-5,5'-bis(1H-imidazol-1-yl)-2,2'-bithiophene-κ2N:N']bis(μ3-4,4'-oxydibenzoato)-κ3O:O':O'';κ4O:O',O'':O'-dicopper(II)], [Cu2(C14H8O5)2(C14H10N4S2)(H2O)]n or [Cu2(bibp)(oba)2(H2O)]n, (II), have been prepared through one-pot concomitant crystallization and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, powder X-ray diffraction (PXRD) and thermogravimetric (TG) analysis. Single-crystal X-ray diffraction indicates that the most interesting aspect of the structure is the existence of sole trans and cis conformations of the bibp ligand in a single net of (I) and (II), respectively. Compound (I) displays a threefold interpenetrating three-dimensional framework with a 4-connected {65.8} cds topology, whereas (II) features a one-dimensional chain structure. In the crystal of (II), the polymeric chains are further extended through C-H...O hydrogen bonds and C-H...π interactions into a three-dimensional supramolecular architecture. In addition, strong intramolecular O-H...O hydrogen bonds formed between the bridging water molecules and the carboxylate O atoms improve the stability of the framework of (II). Furthermore, solid-state UV-Vis spectroscopy experiments show that compounds (I) and (II) exhibit optical band gaps which are characteristic for optical semiconductors, with values of 2.70 and 2.26 eV, respectively.

A multiple hydrogen-bonded three-dimensional supramolecular architecture composed of a unique three-fold interlocked anionic Zn(ii)-coordination architecture

A multiple hydrogen bonded 3D supramolecular architecture composed of interlocked anionic Zn(ii)-coordination architecture possesses two kinds of distinct cavities in the interlocked positions and between adjacent self-knitting layers respectively.

Synthesis, crystal structure and bovine serum albumin–binding studies of a new Cd(II) complex incorporating 2,2′-(propane-1,3-diyl)bis(1H-imidazole-4,5-dicarboxylate)

A new Cd(II) complex, [Cd(H4pbidc)(H2O)] n (1), incorporating 2,2′-(propane-1,3-diyl)bis(1H- imidazole-4,5-dicarboxylic acid) (H6pbidc) was synthesized and characterized by elemental analysis, infrared spectra and X-ray single-crystal diffraction. In complex 1, each Cd(II) ion is hepta-coordinated, showing a significantly distorted pentagonal-bipyramidal coordination environment. Adjacent Cd(II) ions are alternately joined through two carboxylate oxygen atoms and two bridging water molecules resulting in a one-dimensional chain structure. In the solid state, adjacent chains are further linked by hydrogen bonds, forming a three-dimensional supramolecular architecture. Meanwhile, the interactions of complex 1 with bovine serum albumin were analysed by fluorescence measurements under physiological conditions. The results indicated that the fluorescence intensity of bovine serum albumin was decreased considerably upon the addition of complex 1 through a static quenching mechanism with formation of one binding site. The negative values of the thermodynamic parameters including enthalpy change (Δ H), entropy change (Δ S) and Gibbs free energy change (Δ G) showed that hydrogen bonding and van der Waals forces were the main interactions in the binding of complex 1 to bovine serum albumin, and the binding process is spontaneous in thermodynamics.

A Co-MOF with a (4,4)-connected binodal two-dimensional topology: synthesis, structure and photocatalytic properties.

The Co-MOF poly[[diaqua{μ4-1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene-κ4N:N':N'':N'''}cobalt(II)] benzene-1,4-dicarboxylic acid benzene-1,4-dicarboxylate], {[Co(C34H24N12)(H2O)2](C8H4O4)·C8H6O4}n or {[Co(ttpe)(H2O)2](bdc)·(1,4-H2bdc)}n, (I), was synthesized by the hydrothermal method using 1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene (ttpe), benzene-1,4-dicarboxylic acid (1,4-H2bdc) and Co(NO3)2·6H2O, and characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD), luminescence, optical band gap and valence band X-ray photoelectron spectroscopy (VB XPS). Co-MOF (I) shows a (4,4)-connected binodal two-dimensional topology with a point symbol of {44·62}{44·62}. The two-dimensional networks capture free neutral 1,4-H2bdc molecules and bdc2- anions, and construct a three-dimensional supramolecular architecture via hydrogen-bond interactions. MOF (I) is a good photocatalyst for the degradation of methylene blue and rhodamine B under visible-light irradiation and can be reused at least five times.

Crystal structure and DFT study of a zinc xanthate complex.

In the title compound, bis-(2-meth-oxy-ethyl xanthato-κS)(N,N,N',N'-tetra-methyl-ethylenedi-amine-κ2 N,N')zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N',N'-tetra-methyl-ethylenedi-amine ligand and two S atoms from two 2-meth-oxy-ethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The mol-ecular structure features two C-H⋯O and two C-H⋯S intra-molecular inter-actions. In the crystal, mol-ecules are linked by weak C-H⋯O and C-H⋯S hydrogen bonds, forming a three-dimensional supra-molecular architecture. The mol-ecular structure was optimized using density functional theory (DFT) at the B3LYP/6-311 G(d,p) level. The smallest HOMO-LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The mol-ecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the mol-ecules. Half a mol-ecule of disordered acetone was removed with the solvent-mask procedure in OLEX2 [Dolomanov et al. (2009 ▸). J. Appl. Cryst. 42, 339-341] and this contribition is included in the formula.

Synthesis, Structural Characterization and Ligand-Enhanced Photo-Induced Color-Changing Behavior of Two Hydrogen-Bonded Ho(III)-Squarate Supramolecular Compounds.

Two coordination polymers (CPs) with chemical formulas, [Ho2(C4O4)2(C2O4)(H2O)8]·4H2O (1) and [Ho(C4O4)1.5(H2O)3] (2), (C4O42− = dianion of squaric acid, C2O42− = oxalate), have been synthesized and their structures were determined by single-crystal X-ray diffractometer (XRD). In compound 1, the coordination environment of Ho(III) ion is eight-coordinate bonded to eight oxygen atoms from two squarate, one oxalate ligands and four water molecules. The squarates and oxalates both act as bridging ligands with μ1,2-bis-monodentate and bis-chelating coordination modes, respectively, connecting the Ho(III) ions to form a one-dimensional (1D) ladder-like framework. Adjacent ladders are interlinked via O–H⋅⋅⋅O hydrogen bonding interaction to form a hydrogen-bonded two-dimensional (2D) layered framework and then arranged orderly in an AAA manner to construct its three-dimensional (3D) supramolecular architecture. In compound 2, the coordination geometry of Ho(III) is square-antiprismatic eight coordinate bonded to eight oxygen atoms from five squarate ligands and three water molecules. The squarates act as bridging ligands with two coordination modes, μ1,2,3-trismonodentate and μ1,2-bis-monodentate, connecting the Ho(III) ions to form a 2D bi-layered framework. Adjacent 2D frameworks are then parallel stacked in an AAA manner to construct its 3D supramolecular architecture. Hydrogen bonding interactions between the squarate ligands and coordinated water molecules in 1 and 2 both play important roles on the construction of their 3D supramolecular assembly. Compounds 1 and 2 both show remarkable ligand-enhanced photo-induced color-changing behavior, with their pink crystals immediately turning to yellow crystals under UV light illumination.

A One-Dimensional Double-Chain Co(II) Metal–Organic Framework Based on Mixed Flexible N-donor Carboxylate and Bipyridine Ligands: Synthesis, Structure, Thermal Stability and Magnetic Property

A new metal–organic framework (MOF), [Co(L)2(4,4′-bipy)]n (1) [HL = 4-{[(1-phenyl-1H-tetrazol-5-yl)sulfanyl]methyl}benzoic acid, 4,4′-bipy = 4,4′-bipyridine], has been solvothermally synthesized and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. As revealed by the single crystal X-ray diffraction, there exist two kinds of the L− ligands that are “Z”-shaped and “U”-shaped L− ligands in complex 1. Two “U”-shaped L− ligands bridge two symmetry-related Co(II) cations to form a dinuclear [Co2(COO)2] secondary building unit (SBU). The adjacent dinuclear SBUs are connected by bipillared 4,4′-bipy ligands to generate an interesting one-dimensional double chain, which is further consolidated by the intrachain π–π interactions between neighbouring pyridyl rings of 4,4′-bipy ligands. These one-dimensional double chains are further linked by multiple interchain C–H···N, C–H···π and π–π weak interactions to form a three-dimensional supramolecular architecture. Thermogravimetric analysis and variable-temperature powder X-ray diffraction studies indicate that complex 1 shows good thermal stability. In addition, the magnetic investigation reveals that complex 1 exhibits an antiferromagnetic interaction between two Co(II) ions in the dinuclear [Co2(COO)2] SBU. A one-dimensional double-chain Co(II) (MOF), [Co(L)2(4,4′-bipy)]n (1) [HL = 4-{[(1-phenyl-1H-tetrazol-5-yl)sulfanyl]methyl}benzoic acid, 4,4′-bipy = 4,4′-bipyridine], has been solvothermally synthesized and characterized. The thermal stability and magnetic property of 1 have been investigated.