3D Supramolecular Structure Research Articles

Naphthalenedisulfonate-based Cd(II) CPs as fluorescent sensors for turn-on and red-shift sensing of tryptophan

Tryptophan (Trp) is one of the essential amino acids in human body, which is important for human health. Therefore, convenient strategies for the detection of Trp are very significant. Coordination polymers (CPs) have presented great importance as fluorescent sensors in recent years. Herein, two Cd(II) CPs were synthesized as fluorescent sensors for turn-on and red-shift sensing of tryptophan, namely, {[Cd(1,4-bbix)2(1,5-NDS)]·(H2O)2}n (1) and {[Cd(bmbp)2(H2O)2]·(1,5NDS)(H2O)4}n (2), (1,5-NDS = 1,5-naphthalenedisulfonate, 1,4-bbix = 1,4-bis(benzimidazol-1-yl-methyl)benzene, bmbp = 4,4′-bis(2-methylimidazole-1-yl-methyl)biphenyl). 1 shows a three-dimensional (3D) structure with 6-connected pcu topology. 2 shows a 1D chain, which is connected by hydrogen-bonds to form the 3D supramolecular structure. Both CPs can effectively detect Trp via fluorescence enhancement and red-shift in aqueous solution with the limits of detection being 1.11 μM and 0.69 μM for 1 and 2, respectively. Two CPs also can be applied for the detection of Trp in milk with good sensitivity. The sensing mechanisms toward Trp were investigated via experimental and theoretical calculation methods. The test films were prepared for the visual detection of Trp.

3D organic-inorganic hybrid based on Strandberg-type cluster of [(PIIIO3)2Mo5O15]6−: Synthesis, crystal structure and electrochemical properties

The rational design of crystalline materials coupled with polyoxometalate as electrocatalyst is an effective strategy for the sensitive electrochemical detection of H2O2. Here, a new organic-inorganic hybrid, H2(NH4)3[Him][(PIIIO3)2Mo5O15]·4H2O (1) (im=imidazole), was isolated by a one-pot self-assembly strategy. Structural analysis indicates that compound 1 adopts a three-dimensional (3D) supramolecular structure based on the Strandberg-type [(PIIIO3)2Mo5O15]6− clusters linked with protonated [Him]+ cations via hydrogen bond interactions. Electrochemical studies reveal that compound 1 exhibits the multi-electron redox processes ascribed to MoVI centers, and has good electrocatalytic activity in the reduction of H2O2. By utilizing compound 1 as electrode material, the designed electrode showed excellent electrochemical performance towards H2O2 detection, including a wide linear range (50–450 μM), high sensitivity of 0.085 μA·μM−1 and a low detection limit of 3.52 μM, as well as good selectivity and stability.

Syntheses, structures, and characterization of two new Zn(ii)/Cd(ii) complexes with phenanthroline derivative

Abstract Under hydrothermal conditions, two novel Zn(ii)/Cd(ii) complexes [Cd2(L)4(Cl)2]·(SO4) (1) and {[Zn2(L)2(Sip)(OH)]·H2O} n (2) (L = 2-(2,6-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, NaH2Sip = 5-sulfoisophthalic acid monosodium salt) were successfully synthesized and characterized by elemental analysis, single-crystal X-ray diffraction, and Hirshfeld surface analysis. The study reveals that complex 1 is constructed from the binuclear [Cd2L4Cl2] unit, and the [Cd2L4Cl2] units are linked via C–H⋯π and C–Cl⋯π interactions into 2D supramolecular layers. These 2D layers are further connected to generate 3D structures by N–H⋯O and N–H⋯S hydrogen bonds. Complex 2 exhibits a 1D double-chain structure consisting of a binuclear [Zn2L2(OH)] unit, which is further connected by π–π interaction to shape a 2D supramolecular structure.

Synthesis, characterization, crystal structures and catalytic activity of hydrogen bond mediated 2D and 3D-copper(II) coordination networks based on 2-aminoterepthalic acid and 5-aminoisopthalic acid

Two new copper(II) compounds [Cu2(2-NH2BDC)2(bipy)2(H2O)4] (1) and [Cu2(µ2OH)2(5-aip)(bipy)2(H2O)].5H2O (2) have been synthesized and characterized by elemental analyses, IR, thermogravimetric analysis, and electronic absorption spectroscopy. Molecular structures of compounds 1 and 2 were determined crystallographically. Single crystal X-ray studies show that the coordination network 1 is a centrosymmetrical dimeric unit with the 2-aminoterephthalate ligand bridging the two copper atoms. Each CuII atom is hexacoordinated, residing in an octahedral environment, surrounded by one oxygen and one nitrogen atoms from 2-aminoterephthalate ligand and two nitrogen atoms from one bipy ligand and two water molecules to give a CuO3N3 segmentand generate the an infinite three-dimensional (3D) supramolecular structure resulting from CH•••O interactions between adjacent dimer molecules running parallel to the a axis. In compound 2, each CuII atom is pentacoordinated, residing in a square pyramidal geometry and generate an infinite two-dimensional (2D) supramolecular structure resulting from CH•••O, NH•••O and OH•••O hydrogen bond interactions. The coordination network 1 and 2, on pyrolyzing, yielded copper oxide nanoparticles, which have been characterized by TEM and powder X-ray diffraction. The catalytic properties of the resulting copper oxide nanoparticles have also been studied for CN cross-coupling reactions with aryl halides. The CN coupling products were obtained in 70–99 % yields.

Intermolecular Assembly of Dual Hydrogen Bonding Regio-Isomers Generates High-Performance AIE Probes.

Regio-isomers are utilized to design innovative AIE luminogens (AIEgens) by regulating molecular aggregation behavior. However, relevant examples are limited, and the underlying mechanism is not fully understood. Herein, a regio-isomer strategy is used to develop AIEgens by precisely regulating the intermolecular interactions in the solid state. Among the regio-isomers it is investigated, ortho- isomer (DCM-O3-O7) exhibits enhanced AIE-activity than the para- isomer (DCM-P6), and the size of the ortho- substituents is crucial for the AIE performance. The underlying mechanism of the strategy is revealed using DFT calculations and single-crystal analysis. Dual hydrogen bonds (C─H∙∙∙π and C─H∙∙∙N) are generated between the molecules, which contributes to form dimers, tetramers, and 1D supramolecular structures in the crystal. By restricting intramolecular motion and attenuating π-π interactions, solid-state fluorescence is significantly enhanced. This strategy's effectiveness is validated using other donor-acceptor fluorophores, with DCM-O6 and its analogues serving as efficient probes for bioimaging applications. Notably, DCM-OM, which bears a morpholinyl instead of piperidinyl group, displayed strong lysosome-targeting ability and photostability; DCM-OP, incorporated by the hydrophilic quaternary ammonium group, exhibited wash-free imaging and cell membrane-targeting capabilities; and DCM-O6 nanoparticles enabled high-fidelity in vivo tumor imaging. Therefore, this strategy affords a general method for designing bright AIEgens.

Three Co-MOFs with various structures based on 4, 4’, 4’’-nitrilotrisbenzoic acid: Structure, magnetic properties and multifunctional luminescence sensing

In this work, we designed and presented three Co(II) metal-organic frameworks (MOFs), {[Co3(NTB)2(DIMB)]·H2O·DMA}n (NTB-1), {[Co3(NTB)2(DMIMB)]·DMA}n (NTB-2), and {Co(HNTB)(dpa)(H2O)2}n (NTB-3) (H3NTB = 4, 4′, 4′’-nitrilotrisbenzoic acid, DIMB = 1,4-di(1H-imidazol-1-yl) butane), DMIMB = 1,4-di(1H-2-methylimidazol-1-yl) butane), dpa = 9,10-di(4-pyridyl)anthracene) by mix-ligand strategy. X-ray diffraction analysis revealed that NTB-1 and NTB-2 exhibited three-dimensional (3D) architectures with 2, 3, 8-c net topology based on the trinuclear [Co3O12] units, while NTB-3 displayed 2D framework and further subsequently extended to 3D supramolecular structure via classical OH···O hydrogen bond. Thermogravimetric analysis (TGA) and Powder X-ray diffraction (PXRD) exhibited thermal and chemical stability of NTB-1–3. Investigation of magnetic susceptibilities indicated the antiferromagnetic coupling was existed in neighboring Co(II) ions for NTB-1–3. NTB-3 displayed single-molecule magnet characteristics with τ0 = 1.67×10−5 s and Ueff = 9.4 K. Luminescence sensing analyses demonstrated that NTB-1–3 can be regarded as promising luminescent sensors for Pb2+, Fe3+, CrO42− and Cr2O72−. Finally, the possible quenching mechanism for various ions were fully discussed.

Practicality and Compatibility of Cd(II) Coordination Polymer as Luminescent Sensor in Selective and Sensitive Detection of 3‐Nitrotyrosine Biomarker

AbstractBased on the mixed ligands of 1,4‐bis(2,4,6‐tricarboxylpyrid‐5‐yl)benzene (H6BTPB) and 1,4‐bis(imidazol‐1‐yl)benzene (bib), a new cadmium(II) coordination polymer with the molecular formula of {[Cd(bib)(μ2‐H2O)(H2O)2](H4BTPB)0.5(bib)0.5}n (CdCP) was constructed under solvothermal condition, and displayed a 3D supramolecular structure expanded by the hydrogen bonds between the 1D [Cd(bib)(μ2‐H2O)(H2O)2]n ladder chain and the guests. Profiting from its superior stability and inherent luminescence, the prepared CdCP dispalyed great potential as a highly sensitive and selective luminescent sensor in trace detection of 3‐NT biomarker in both water and real bodily fluids through the luminescence quenching effects, with the Ksv and LODs being 2.408×105 M−1 and 30.3 nM in water, 2.230×105 M−1 and 44.7 nM in diluted urine, 2.249×105 M−1 and 43.9 nM in diluted serum, respectively. Subsequent mechanism studies indicated the synergistic effect of internal filtering effect, photo‐induced electron transfer, and fluorescence resonance energy transfer determining the luminescence quenching response of CdCP towards 3‐NT biomarker.

Lattice Symmetry-Guided Charge Transport and Recombination in Supramolecular Assemblies

Synthetic soft materials mimicking biological structures are promising for many applications in fields such as photovoltaics and photocatalysis. For these applications, a deep understanding of the charge- and energy-transfer mechanisms is required to build more efficient devices. In this work, we investigate self-assembled 2D supramolecular structures using angle-resolved photoluminescence (PL) imaging techniques and decompose the optical transition dipoles in the supramolecular structures. Combining these optical studies with Monte Carlo simulations, we reveal the important role played by lattice symmetry in charge dissociation, transport, and recombination, as well as the exciton spin states. These mechanistic findings have important implications for engineering soft materials towards efficient energy conversion and photocatalytic applications.

Synthesis, structure, theoretical calculation and photocatalytic property of a novel Mn(II) supra-molecular compound containing SCN- and 2,2′-bipyridine ligands

A novel supra-molecular compound [Mn(SCN)2(byp)2] 1 (byp = 2,2′-bipyridine) was synthesized under hydrothermal conditions. Noteworthily, the SCN- in the title compound is derived from the in situ reaction of salicylaldehyde thiosemicarbazone. X-ray single-crystal diffraction analysis shows compound 1 is only a mononuclear structure, but it is expanded into a 3D supramolecular structure via H-bonds and π···π stacking. Hirshfeld Surface analysis shows C⋯H, H⋯H and S⋯H interaction are the main contribution of intermolecular interactions in the formation of compound 1. All of title compounds were characterized by IR spectroscopy, elemental analysis, XRD, XPS and TG analysis. The energy framework of compound 1 is dominated by dispersion interaction. The photocatalytic degradation ability of compound 1 for methylene blue is verified by photocatalytic degradation experiments (pH = 4: 44.6 %; pH = 7: 76.2 %; pH = 10: 78.8 %). Furthermore, the potential photocatalytic mechanism of compound 1 is inferred by UV–vis absorption spectra and Mott–Schottky curve.

Synthesis, crystal structure, spectroscopic and theoretical studies of a new fluorescent heterocyclic compound containing diketopyrrolopyrrole (DPP) moiety

A new diketopyrrolopyrrole (DPP) derived fluorescent heterocyclic compound, DPP-BA, has been synthesized and characterized by SXRD, FL spectroscopy and computational methods. SXRD studies indicate that hydrogen bonding and π-π stacking interactions are crucial for the assembly of its 3D supramolecular structure. The weak interactions within the compound were studied using IRI and NCI methods, while the planarity of DPP-BA in the DPP-BA-DMSO was quantified using MPP and SDP descriptors. The MEP map highlighted the nucleophilic and electrostatic regions in DPP-BA. In addition, Hirshfeld surface analysis and RESP atomic charges were used to visualize the interactions and to delineate the charge distribution within DPP-BA. The interaction energy and 3D energy frameworks facilitated an intuitive examination and understanding of the molecular arrangement and stability within the crystal. A comparison between the experimental and computational FL spectra was made using a range of DFT functionals, with the PBE0 functional providing the most accurate results. Analyses of the HOMO-LUMO and hole-electron distributions have shed light on the molecular electronic structure, thereby deepening our understanding of the electronic excitation processes within the molecule.

Synthesis, crystal structure study, characterization, and DFT investigation of a new nickel(II) complex, [dihomopiperazine nickel (II)] sulfate tetrahydrate

A new nickel (II) complex [NiL2](H2O)4(SO4), where L = 1,4-diazepane, has been synthesized by interaction between nickel sulfate and 1,4-diazepane. This complex crystallizes in the Pmcn orthorhombic unit cell with parameters a = 9.173(2) Å, b = 11.691(2) Å, c = 17.015(2) Å, V = 1824.9(5) Å3, and Z = 4. It possesses a mononuclear structure in which the central NiII atom is coordinated by four N atoms from two 1,4-diazepane ligands in a distorted square-planar geometry. In the crystal, the anions [SO4]2−, the cations [NiL2]2+, and the water molecules are held together by H-bonding to form a 2D supramolecular structure. Differential scanning calorimetry (DSC) results showed that this compound undergoes a reversible order–disorder phase transition at 486 K with a hysteresis of 32 K. In addition, electrical conductivity measurements showed that the complex has a conductivity value of 4.15 10−4 Ω−1cm−1 at 390 K. The Density Functional Theory (DFT) study results qualitatively supported the experimental data obtained by X-ray diffraction and thermogravimetric analysis (TGA).

Structural diversity of transition-metal coordination polymers and dinuclear metallocycles constructed by bispyridyl-substituted diphthalic diimide ligands

Four coordination polymers (CPs), namely, {[Ni(L1)2Cl2]·(CHCl3)}n(1), {[Co(L1)1.5(NO3)2]·(CHCl3)}n (2), {[Ag2(L2)2(NO3)2]·(CHCl3)}n (3), [Cd(L2)2(Cl)2]n (4), and two dinuclear metallocycles, namely, {[Zn2(L3)2(Cl)4]·2CHCl3}n (5) and [Cu2(L3)2(Cl)4] (6), (L1 = 2,2′-bis(pyridin-3-ylmethyl)-[5,5′-biisoindoline]-1,1′,3,3′-tetraone), L2 = 5,5′-oxybis(2-(pyridin-3-ylmethyl)isoindoline-1,3-dione), L3 = 5,5′-carbonylbis(2-(pyridin-3-ylmethyl)isoindoline-1,3-dione)), have been adeptly constructed using solvothermal conditions and successfully delineated by non-destructive single-crystal (X-ray) diffraction. Structural analyses provide insights into a two-dimensional (2D) 44 grid layer of complex 1 and a three-dimensional (3D) 63 network of 2. Additionally, the connection between these two complexes is established via hydrogen bonding (CH···O) to further accomplish a three-dimensional (3D) supramolecular framework system. Similarly, Complex 3 and 4 possess a one-dimensional (1D) wave-like chain and loop-like chains composed of olive-like metallacycle building units, respectively. These chains are bridged by CH···O hydrogen bond and π∙∙∙π stacking interactions to generate 3D supramolecular structure. Finally, complexes 5 and 6 occupies zero-dimensional (0D) square-like array also called as olive-like dimeric M2L2 metallacycles. The distinct structural configurations of the six complexes are in close alliance with different conformations of the N-donor pyridyl ligands and coordination arrangement of the transition metal centers.

Solvent-controlled structural variation of two Cd(II) compounds derived from thiophene dicarboxylate and 4-imidazol-1-yl-pyridine mixed ligands

Two solvent-controlled Cd(II) compounds, formulated as {[Cd2(Htdc)4(µ-imyp)(H2O)4]} (1), [Cd2(µ 2-tdc)2(µ-imyp)(DMF)2(H2O)2]n (2) (H2tdc= 2,5-thiophenedicarboxylic acid, imyp = 4-imidazol-1-yl-pyridine and DMF = N,N-dimethylformamide) have been synthesized by reactions of Cd(NO3)2·4H2O and H2tdc with imyp in different solvents, respectively. Both compounds were then characterized by single-crystal X-ray diffraction and other physicochemical methods. In 1, partially deprotonated Htdc− anion as terminal ligand and µ-imyp ligand connect Cd2+ ions to generate a discrete structure. In 2, completely deprotonated µ 2 – tdc2− anions and µ-imyp ligand link Cd2+ ions into a 1D double chain structure. Both compounds display 3D supramolecular structures through hydrogen bonding interactions. The results provided interesting insights into solvent effects on the structural formation of compounds 1 and 2. In addition, the solid-state photoluminescent properties of compounds 1 and 2 were also investigated. Two solvent-controlled Cd(II) compounds have been synthesized by reactions of Cd(NO3)2·4H2O and 2,5-thiophenedicarboxylic acid with 4-imidazol-1-yl-pyridine in the different solvents. One compound is a discrete structure, while the other compound has a 1D double chain structure. The results provided interesting insights into solvent effects on the structural formation of compounds.

Construction of coordination polymer [Ni(ppda) (tib) (H2O)]·H2O and photocatalytic degradation of indigo carmine

Semiconductor coordination polymers have garnered significant attention as photocatalysts for wastewater treatment owing to their adaptable structure, expansive specific surface area, and outstanding selectivity, stability, and sensitivity. In this study, coordination polymer [Ni(ppda) (tib) (H2O)]·H2O was synthesized utilizing flexible phenyldiacetic acid (H2ppda) and rigid 1,3,5-tris(1-imidazolyl)benzene (tib). Crystal structure analysis revealed that the three-linked tib ligands and the central Ni(II) ion create a wavy 2D surface. Additionally, cis-ppda2- ligands form a 1D wave chain alongside central Ni(II), which traverse through a 2D layer. Adjacent layers are interlaced via ppda2−, resulting in a complex 3D supramolecular structure. The fundamental framework of [Ni(ppda) (tib) (H2O)]·H2O exhibits stability up to 316 °C and remains stable over 5 cycles, with a band gap energy of 2.9 eV, rendering it a viable candidate for catalytic applications. In aqueous systems, [Ni(ppda) (tib) (H2O)]·H2O demonstrates efficient photocatalytic degradation of Indigo Carmine (IC), achieving a degradation rate of 98.5% and a reaction rate of 0.027 min−1, showcasing commendable selectivity and semiconductor properties. The primary photocatalytic degradation mechanism involves the synergistic formation of ·OH and ·O2- active species through the interaction between [Ni(ppda) (tib) (H2O)]·H2O and H2O2, facilitating the oxidative degradation of dye molecules.

Two Zn(II) complexes based on bis(benzimidazole) and different dicarboxylate anions: synthesis, structures, and fluorescent properties

Two new zinc(II) complexes, [Zn2(PBM)2(terephthalate)(formate)2] (1) and {[Zn(PBM)(fumarate)]∙H2O}n (2), were synthesized using 1,3-bis(1H-benzo[d]imidazol-2-yl)propane (PBM) and two different dicarboxylic acids under solvothermal conditions. Complexes 1 and 2 have been characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. The structural analysis showed that 1 was a binuclear structure and then formed a 3D supramolecular network structure through hydrogen bond and π-π conjugation, while 2 was a one-dimensional coordination polymer. In 1 and 2, the zinc ions were four-coordinate with an N2O2 donor set and a slightly distorted tetrahedral geometry. The solid-state fluorescence properties indicate that the fluorescence peaks belong to the π*-π transition of the ligand PBM, which has a significant red shift and enhancement with the order being 1 > 2 > PBM. The stronger fluorescence of the complexes than the ligand is due to the immobilization of the ligand through coordination, which reduces the energy loss of thermal vibration. The π∙∙∙π conjugation in 1 results in a stronger fluorescence of 1 than 2. Therefore, coordination and π∙∙∙π conjugation will affect the fluorescence of complexes.

A new type Co(II)-based photocatalyst for the nitrofurantoin antibiotic degradation

Coordination polymers (CPs) are a special class of multidimensional materials that can be employed for the photocatalytic degradation of antibiotics in wastewater. In this paper, a new Co(II)-based coordination polymer with the molecular formula {[Co(H2L)(dpa)(H2O)]·H2O}n (1), (H4L = 1,1′:2′,1″-triphenyltetracarboxylic acid, dpa = 1,2-di(pyridin-4-yl)diazene) was synthesized and characterized. Single-crystal x-ray diffraction results showed that 1 formed a 2D layered structure, which was stacked into a three-dimensional (3D) supramolecular structure through hydrogen-bonding interactions. In addition, the results of the photocatalytic experiments showed that 1 possesses good photocatalytic activity at nitrofurantoin (NFT). The photocatalytic mechanism has been discussed in detail.

Synthesis, structure, and small molecule in situ modification effects on proton conduction properties of triazine‐based triscarboxylic acid complexe

In this study, we synthesized and characterized a new Co(II)‐based coordination polymer, denoted as {[Co(HL)(dpa)]·H2O}n (1), derived from the H3L ligand and dpa co‐ligand. Single crystal X‐ray diffraction revealed that 1 forms a two‐dimensional (2D) layer and a three‐dimensional (3D) supramolecular structure via hydrogen bonding interactions. Presence of carboxylic acid groups in 1 was confirmed by X‐ray crystallography, prompting investigation into its proton transport properties. Additionally, electrostatic potential surface and nucleophilic index analyses were conducted to simulate potential proton transfer pathways. Furthermore, we prepared nine modified encapsulated materials using 1 as the base material (SDA@1, APH@1, APY@1, TA@1, BA@1, DIC@1, IDZ@1, SCA@1, and TYD@1), and tested their proton conductivity and activation energy compared to pure Nafion membrane and 1, analyzing the influence of different small molecule structures on proton conductivity. Comparative analysis revealed that only SDA@1 exhibited enhanced proton conductivity and reduced activation energy at 303 K, with an improvement rate of 220.8%. We hope that the methods presented herein can provide valuable insights for the design and development of high‐performance proton‐conducting materials, as well as for the exploration of proton conduction mechanisms.

Structural, spectroscopic and computational studies of a new hydrogen-bonded organic framework containing carbazole moiety

A new hydrogen-bonded organic framework, CZ-1, containing a carbazole moiety was synthesized and characterized by SXRD, UV–Vis, FL and computational methods. SXRD analyses show that hydrogen bonding and π-π interactions are essential for the formation of its 3D supramolecular structure. IRI and NCI methods are used to analyze these weak interactions, while MPP and SDP descriptors are used to quantify the planarity of H3L in CZ-1. MEP highlighted nucleophilic and electrostatic regions in CZ-1, Hirshfeld surface analyses and RESP atomic charges visualized the interactions and depicted the charge distribution of H3L in CZ-1, respectively. The experimental and computed UV–Vis and FL spectra were compared using various density functional theory (DFT) functionals, with the PBE0 functional demonstrating the most accurate results. HOMO-LUMO and hole-electron analyses provided insights into the molecular electronic structure, enhancing the understanding of electronic excitation behavior within the molecule. Results from the RASPA program indicated that the porous structure of CZ-1 has the potential for adsorbing and separating CO2/N2 mixture.

Two 3D fsc-type hydrogen-bonded networks as luminescent sensors for turn-on sensing of tryptophan and aspartic acid

Two new luminescent coordination polymers (CPs), [M(Aze)(bmbp)]n (M = Zn for 1; Cd for 2), based on 4,4′-bis(2-methylimidazol-1-ylmethyl)biphenyl (bmbp) and azelaic acid (H2Aze) ligands have been hydrothermally synthesized. In their crystal structures, the metal centers are connected by bmbp and Aze2- to generate 1D chains, which are further linked by CH···O hydrogen bonds to form 3D supramolecular structures. Topological analysis suggests that the 3D hydrogen-bonded networks are binodal (4,6)-connected fsc nets with the symbol of (44·610·8) (44.62). CPs 1 and 2 both dispay excellent photoluminescence with good stability. Luminescent sensing experiments show that both 1 and 2 can be used as turn-on sensors to detect tryptophan (Trp) and aspartic acid (Asp) in aqueous solution. The limits of detections (LODs) toward Trp and Asp are 0.30 and 5.33 μM for 1, 0.23 and 2.62 μM for 2, respectively. Furthermore, the sensing mechanisms were also investigated in detail via various detection means and theoretical calculations. The test films of both CPs were also prepared for visual detection of Trp and Asp.

Two-dimensional Cd(II) metal–organic framework based on tri-imidazolyl ligand: Synthesis, structure and selective luminescence sensing

A Cd(II) metal–organic framework with 4,4′-biphenyldicarboxylic acid (4,4′-H2bpda) and 1,3-bis(1-imidazolyl)-5-[4-(1-imidazolyl)-phenoxymethyl]-benzene (ptim), {[Cd2(NO3)2(bpda)(ptim)2]·2DMF·H2O}n (1), has been synthesized under hydrothermal condition. Single-crystal X-ray diffraction analyses demonstrate that complex 1 exhibits a 2D bilayered structure interconnected with 4-bpda, resulting in 1D channels. These layers are arranged via the π···π stacking interactions between ptim ligands, forming a 3D supramolecular structure. The solid state luminescent property of 1 at ambient temperature was also investigated and showed a high selectivity and sensitivity for Fe(III) owing to the quenching effect.