PDA Ligands Research Articles

Four octamolybdate–based hybrid compounds consisting of phenanthroline derivative ligands with photocatalytic and capacitive performances

Employing polyoxometalate–based hybrid materials combined from metal–organic complex and polyoxometalate as photocatalysts for pollutant degradation and capacitive electrodes has become a research focus. In order to continue to develop the potential photocatalysts and electrode materials, four octamolybdate–based hybrids constructed from phenanthroline derivative ligands 1, 10 − phenanthroline − 5, 6 − dione (PDO) and 1, 10 − phenanthroline − 5, 6 − diamine (PDA) were isolated. The [β − Mo8O26]4− anions were involved in the structures of 1–3, which were aggregated by Cu ions into a two–dimensional layer decorated by PDO or PDA ligands in 1 and 2, but discrete and coexist with [Co(H2O)2(PDO)2]2+ metal–organic components in 3. 4 featured [α − Mo8O26]4− anions bi–supported by two [Co(H2O)(PDA)2]2+ metal–organic fragments. The introduction of metal–organic complexes of metal/PDO or PDA improved the light absorption, conductivity and electrochemical active surface area of these hybrid compounds. Consequently, compounds 1–4 as photocatalysts showed photocatalytic activity for degradation of organic dyes with good recyclability and stability at least 3 cycles. The possible photocatalytic degradation mechanism was discussed. Additionally, compounds 1–4 employed as electrode materials demonstrated good capacitive performances, especially 4 with the specific capacitance of 1385.3F g−1 at the current density of 1 A/g.

Synthesis, Structural Analysis and Bright Emission Performance of a New Family of 3D Lanthanide Coordination Polymers Based on 1,3‐phenylenediacetic Acid

AbstractA novel series of isostructural lanthanide coordination polymers with the general formula [Ln2(PDA)3(DMF)2] (where Ln3+= La, Nd, Pr, Tb, Sm and Eu, DMF= N,N’‐dimethylformamide and PDA =1,3‐phenylenediacetate) were hydrothermally synthesized and further characterized by vibrational spectroscopy, thermal analysis, scanning electron microscopy (SEM), energy dispersive X‐ray (EDX) analysis, and powder and single‐crystal X‐ray diffraction techniques. In addition, from the crystallographic data, it was possible to determine the topology of the structure, finding that the network consists of 5‐connected nodes with topological type: nov; 5/4/o8 and point symbol (44.66). To study the luminescence properties regarding potential energy transfers among the building blocks, lanthanum‐based samples doped with Tb (III) and Eu (III) (1 %, 2 %, 5 % and 10 %) were analyzed in solid state. Upon ligand sensitization, 4 f transitions could be observed confirming an “antenna effect” of the PDA ligand. These new compounds are potential materials for the construction of photoluminiscent devices.

Two Ligands of Interest in Recovering Uranium from the Oceans: The Correct Formation Constants of the Uranyl(VI) Cation with 2,2'-Bipyridyl-6,6'-dicarboxylic Acid and 1,10-Phenanthroline-2,9-dicarboxylic Acid.

The ligands BDA (2,2'-bipyridyl-6,6'-dicarboxylic acid) and PDA (1,10-phenanthroline-2,9-dicarboxylic acid) are of interest as functional group types for ion-exchange materials for extracting uranium from the oceans, reported in a previous paper for PDA Lashley, M. A. ( Inorg. Chem. 2016 55 10818 10829). Yang, Y. ( Inorg. Chem. 2019, 58, 6064 6074) have published what they claim to be a more accurate result for the formation of the UO22+/PDA complex of log K1 = 22.84 compared with our reported value of log K1 = 16.5, as well as log K1 = 21.52 for the BDA complex. The determination of log K1 for the PDA and BDA complexes with the UO22+ cation was carried out by Yang et al. using a competition reaction between DTPA (diethylenetriamine pentaacetic acid) and BDA or PDA, monitoring the absorbance due to the BDA and PDA ligands. This competition method using absorbance versus pH titrations was developed for determining the formation constants of the complexes of several polypyridyl ligands plus PDA complexes of metal ions, which were too stable for log K determination by competition with protons. A key feature of such titrations is that in the competition reaction, the displacement of the pyridyl donor ligand (e.g., PDA) by the competing ligand (e.g., DTPA), the absorbance spectrum of the displaced pyridyl donor ligand should be observed. Competing ligands used to date have been EDTA (ethylenediamine tetraacetic acid), DTPA, or the hydroxide ion. In the study of Yang et al., no such displaced PDA or BDA was apparent in the absorbance spectra in their titrations so that their reported log K1 values have no validity. Their log K1 values are so much higher than log K1 for the uranyl DTPA complex (∼13.6) that DTPA could not possibly displace BDA or PDA from the uranyl cation, and a competition reaction could not possibly occur. We report the correct value of log K1 = 15.4 (ionic strength = zero) for the uranyl BDA complex, to illustrate the correct determination of such a constant by a competition reaction between BDA and hydroxide, showing how the characteristic absorbance spectrum for a BDA complex, here the UO22+ complex, disappears, and the distinctive absorbance spectrum of the free nonprotonated BDA ligand appears as the pH is increased, and BDA is displaced by the hydroxide ion.

Heteroleptic Triple-Stranded Metallosupramolecules with Hydrophobic Inner Voids

The systematic combination of well-defined coordination spheres and multiple types of ligands (heteroleptic) can lead to the generation of hierarchical metallosupramolecules with a high level of complexity and functionality. In particular, a specific multilevel coordination-driven assembly through the initiate generation of multinuclear clusters can form unique heteroleptic multiple-stranded supramolecular complexes. Herein, we report novel triple-stranded nickel-based supramolecules constructed from two different ditopic ligands ([1,1′:3′,1′′-terphenyl]-4,4′′-dicarboxylate (TP) and 2,6-pyridinedicarboxylate (PDA)) and a nickel precursor. The solid-state structures of the as-synthesized supramolecules revealed that three PDA ligands are employed to fabricate a tetranuclear ({Ni4}) cluster, and two {Ni4} clusters are assembled to form the final triple-stranded metallosupramolecules by three TP ligands. The bridging TP ligands also provide large inner voids with highly hydrophobic environments. Structural investigation of the generated complexes provided a deeper understanding of the aspects driving the formation of heteroleptic supramolecules, which is crucial for the design of multiple-strands with desired morphologies and functionalities.

Two polyoxometalate-based hybrids constructed from trinuclear lanthanoid clusters with single‐molecule magnet behavior

In this paper we report the successful hydrothermal synthesis of the two inorganic–organic hybrid assemblies H0.87{Na(H2O)3[Dy(PDA)(H2O)2]3(BW12O40)0.87(SiW12O40)0.13}•11H2O (1) and H0.87{Na(H2O)3[Ho(PDA)(H2O)2]3 (BW12O40) 0.87(SiW12O40)0.13}•10H2O (2) (H2PDA = 1,10-phenanthroline-2,9-dicarboxylic acid). Both hybrids have been characterized using elemental analyses, Fourier transform infrared spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Structural characterizations by single-crystal X-ray diffraction reveals that these hybrids are isostructural including [BW12O40]5- Keggin-type polyoxometalates (actually containing 87% B and 13% Si based on refinement of the crystal structures) connected by three lanthanoids to yield discrete trinuclear lanthanoid clusters. These discrete molecules are further packed into 3D supramolecular assemblies by means of hydrogen-bonding and anion–π interactions. 1 and 2 are two examples of a relatively small number of inorganic–organic hybrid POMs containing the PDA ligand based on a CSD search (CSD version 5.40 updated to November 2018). The temperature dependences of χmT for 1 and 2 are considered. Magnetic studies reveal that 1 exhibits typical single‐molecule magnet (SMM) behavior.

An inorganic–organic hybrid material based on a Keggin‐type polyoxometalate@Dysprosium as an effective and green catalyst in the synthesis of 2‐amino‐4H‐chromenes via multicomponent reactions

A novel inorganic–organic hybrid, [Dy4(PDA)4(H2O)11(SiMo12O40)]·7H2O denoted as (POM@Dy‐PDA), based on a lanthanide cluster, a Keggin‐type polyoxomolybdate, and PDA (1,10‐phenanthroline‐2,9‐dicarboxylic acid) was prepared and fully characterized by elemental analysis, Fourier‐transform infrared and UV–Vis spectroscopies, thermogravimetric analysis, powder X‐ray diffraction (PXRD), and single‐crystal X‐ray diffraction. The structural analysis study showed that the [SiMo12O40]4− ions reside in the interspace between two cationic layers as discrete counterions and are not coordinated to the rare‐earth ions. Significantly, this hybrid catalyst is a rare case of an inorganic–organic hybrid polyoxometalate (POM) with a PDA ligand based on CSD search (CSD version 5.40/November2018). The hybrid catalyst was further characterized via powder X‐ray diffraction (PXRD) pattern at room temperature which indicated the good phase purity of the catalyst. BET and Langmuir surface area analysis indicate surface area of POM@Dy‐PDA 6.6 and 51.3 m2g‐1, respectively. The catalytic activity of the hybrid catalyst was successfully examined in the synthesis of 2‐amino‐4H‐chromene derivatives through a multicomponent reaction. A three‐component, one‐pot reaction involving differently substituted benzaldehydes, resorcinol/α‐naphthol/β‐naphthol/4‐hydroxycoumarin/3‐methyl‐4H‐pyrazole‐5(4H)‐one, and malononitrile or ethyl cyanoacetate in the presence of a catalytic quantity of the aforementioned hybrid catalyst in EtOH/H2O under reflux condition gave the corresponding highly functionalized 2‐amino‐4H‐chromenes in satisfactory yields. The catalyst can be reused several times without appreciable loss in its catalytic activity.

Different behavior of PDA as a preorganized ligand versus PCA ligand in constructing two inorganic-organic hybrid materials based on Keggin-type polyoxometalate

Two lanthanoid-based inorganic-organic hybrids, [Nd4(PDA)4(H2O)9(SiW12O40)]·5H2O (1), (PDA = deprotonated preorganized 1,10-phenanthroline-2,9-dicarboxylic acid) and [Gd(PCA)3(H2O)2]2 [HSiW12O40]2·10H2O (2), (PCA = pyridine-4-carboxylic acid) have been hydrothermally synthesized utilizing the [SiW12O40]4− Keggin-type polyoxometalate as a building block. These two compounds were characterized by elemental analysis, infrared spectroscopy and single crystal X-ray crystallography. Structural characterizations by single crystal X-ray diffraction reveals that hybrid 1 is one of the rarely reported inorganic-organic hybrid POMs with PDA ligand based on CSD search (CSD version 5.38/May 2017) while hybrid 2 with PCA ligand is a coordination compound. At the supramolecular level, hybrid 1 presents 3-D pillar-layered framework with the [SiW12O40]4− anions located on the voids of the 2-D Nd-PDA bilayer. Hybrid 2 consists of discrete Gd-PCA dimer and Keggin anions interacted via hydrogen bond interactions.

Detection of Pesticides in Aqueous Medium and in Fruit Extracts Using a Three-Dimensional Metal-Organic Framework: Experimental and Computational Study.

A new, three-dimensional cadmium based metal-organic framework [Cd3(PDA)1(tz)3Cl(H2O)4]·3H2O {PDA = 1,4-phenylenediacetate and tz = 1,2,4-triazolate}, 1, has been successfully synthesized using slow diffusion method at room temperature. The structure of compound 1 has been determined using single crystal X-ray diffraction. The triazolate ligands connect three different types of octahedral Cd2+ ions to form a two-dimensional structure. The chloride ion and PDA ligands connect the two-dimensional layers to form a three-dimensional structure. The phase purity of 1 was confirmed by powder X-ray diffraction, thermogravimetric analysis, and IR spectroscopy. Aqueous dispersion of compound 1 gives intense luminescence emission at 290 nm upon excitation at 225 nm. This emission was used for the luminescence based detection of pesticides, especially azinphos-methyl, chlorpyrifos, and parathion in aqueous medium. The selectivity of pesticide detection remains unaltered even in the presence of surfactant molecules. The mechanisms of luminescence quenching were successfully explained by the combination of absorption of excitation light, resonance energy transfer, and the possibility of electron transfer. Experimental findings are also well supported by the density functional theory calculations. Selectivity of pesticides detection in real samples such as apple and tomato juice has also been observed.

Cage-like crystal packing through metallocavitands within a cobalt cluster-based supramolecular assembly.

A cobalt (Co) supramolecular triple-stranded helicate, [Co8(PDA)6(Br-PTA)3(DMF)4(H2O)2] (1) (PDA = 2,6-pyridinedicarboxylate, Br-PTA = 5-bromoisophthalate, DMF = dimethylformamide), is successfully synthesized and fully characterized. The solid-state structure of 1 shows that four cobalt atoms are coordinated by three PDA ligands to form a tetranuclear cobalt cluster with three extension points and the ditopic Br-PTA ligands interlink two basic assembly units. In crystal packing, the bromo group is surrounded by the cavity-like tetranuclear cobalt cluster, which acts as a metallocavitand, to generate a unique cage-like crystal packing geometry. The isomorphous molecular cage, which exhibits a similar crystal-packing geometry as observed in 1, is also successfully isolated. This is an unusual example of a highly symmetric cage-like crystal packing architecture, resulting from the interaction among metallocavitands of in situ generated supramolecular modules.

Alkali‐Metal‐Mediated Frameworks Based on Bis(2,6‐pyridinedicarboxylate)cobalt(II) Species

Metal–organic frameworks (MOFs) with compositional multiplicity show unique topologies as well as enhanced chemical and physical properties. The construction of mixed‐metal frameworks containing more than one type of metal element can provide further structural versatility and diversity. The combination of transition‐ and alkali‐metal elements in a framework can result in interesting materials with substantial advantages. Herein, we report a synthetic strategy for the mixed transition‐ and alkali‐metal frameworks [Na2Co(PDA)2] (1, PDA = 2,6‐pyridinedicarboxylate) and [K2Co(PDA)2] (2). The solid‐state structures of these frameworks show that two PDA ligands chelate to a cobalt ion to form a Co(PDA)22– species, which in turn undergoes further assembly mediated by alkali‐metal cations (Na+ or K+) to give mixed‐metal framework structures. The {[KCo(PDA)2]–·[NH2(CH3)2]+} framework (3) is also prepared by a change in stoichiometry. The multiple coordination of alkali metal atoms to the carboxylate oxygen atoms of the PDA ligands of the Co(PDA)22– species generates unique three‐dimensional architectures. As 2 and 3 react with NaOH, the coordinated K+ exchanges readily with Na+ in aqueous solution, and finally 1 crystallizes. The strong ionic character and small size of Na+ account for the facile transformations of 2 and 3. Temperature‐dependent magnetization studies reveal that 1 exhibits distinct magnetic susceptibility relative to those of 2 and 3.

Synthesis, crystal structure, and luminescent properties of two coordination polymers based on 1,4-phenylenediacetic acid

Two coordination polymers, [Zn(pda)(bib)]n (1) and [Cd(pda)0.5(bib)Cl]n (2)]. (H2pda = 1,4-phenylenediacetic acid, bib = 1,2-bis(imidazol-1-ylmethyl)benzene), have been synthesized by using Zn(II)/Cd(II) salts with two flexible ligands pda and bib under hydrothermal conditions. Their structures have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD) analysis. Due to the coordination geometry around the metal ions and the diverse coordination modes of the flexible ligands, the obtained complex show diverse structures. In the structure of 1, a pair of bib ligands connect two Zn(II) atoms give rise a 22-membered ring, which is further extended by pda ligands in bidentate coordination mode leading a ring-containing 2D layer. In 2, bib ligands join [Cd2Cl2]2+ dimmers generate 1D polymeric ribbon, the pda ligands further extend such ribbon forming a 2D layer network containing rectangular windows, which discovers the effect of the central metal ions on the formation of metal–organic frameworks. In additional, luminescent properties of two complexes have also been studied, they could be potential fluorescence materials.

Lanthanide(III) 1,4-Phenylenediacetate Complexes: The Relation Between the Structure and Thermal Properties

The series of isostructural lanthanide coordination polymers with the empirical formula [Ln2(PDA)3(H2O)]·2H2O, where PDA = 1,4-phenylenediacetate anion = [C8H8(COO)2]2−; Ln = La-Lu(III), and Y(III) were produced in the reaction of LnCl3·nH2O with ammonium salt of 1,4-phenylenediacetic acid in water solution. The compounds were characterised structurally using powder X-ray diffraction, elemental and thermogravimetric analyses as well as FT-IR spectroscopy. Thermogravimetric analyses show that in the range 60–170 °C the dehydration process occurs. The thermal stability of dehydrated compounds, Ln2(PDA)3 increased from about 200–350 °C in the whole series of complexes. Single-crystal X-ray diffraction analysis for the Gd(III) complex revealed that the compound crystallizes in the monoclinic P21/c space group with a = 21.863(2) A, b = 10.035(1) A, c = 13.854(1) A, β = 91.53(1)° and V = 3,038.5(4) A3. The complex contains one-dimensional gadolinium-carboxylato chains, which are connected with the –CH2–C6H4–CH2– spacers of PDA ligand to the three-dimensional metal–organic framework.

Three-dimensional lanthanide coordination polymers with p-phenylenediacrylates: Syntheses, structures, and properties

Three three-dimensional lanthanide coordination polymers [Ln2(pda)2(HCOO)(OH)(H2O)]n (Ln=Dy, 1; Tb, 2; Ho, 3; H2pda=p-phenylenediacrylic acid) have been solvothermally synthesized and their structures have been determined using either X-ray powder or single-crystal diffraction data. They are isostructural and possess a 3D architecture with the pcu (α-Po) net topology based on the parallel 1D lanthanide–oxygen rod-shaped secondary building units, each of which is connected to four other rods by the pda ligands. The photoluminescent properties of 1–3 have been investigated. Complexes 1–3 all display the intense blue emission in the solid state at room temperature. Especially, compared with the free H2pda ligands, 1 shows the strong fluorescence enhancement due to the complexation.

Synthesis and Crystal Structure of Three New Zn(II), Ni(II) and Mn(II) Coordination Polymers Based on Asymmetric Dicarboxylate Ligand

Three new coordination polymers [Zn(pda)(H2O)]n (1), [Ni(pda)(bib)1.5]n (2) and [Mn2(pda)2(bimb)]n (3) [H2pda = 3,4′-biphenyl-dicarboxylic acid, bib = 4,4′-bis (2-imidazol-1-ylmethyl) biphenyl and bmib = 4,4′-bis (2-methylimidazol-1-ylmethyl)biphenyl] have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses revealed that that pda ligand acts as bridging ligand, exhibiting rich coordination modes to link metal ions: monodentate, bidentate chelating, bis-monodentate and chelating/bridging fashions. Compound 1 and 2 demonstrate a one-dimensional chain. Compound 3 is a two-dimensional (4,4) layer structure. Furthermore, the solid state luminescence spectrum of compound 1 is investigated at room temperature.

A novel water-rich mononuclear copper(II) complex with pyridine-2,4-dicarboxylate: Synthesis and crystal structure

A new monomolecular copper(II) complex, [Cu(Phen)2(Pda)] · 9H2O (I) (H2Pda = pyridine-2,4-dicarboxylate acid, Phen = 1,10-phenanthroline), has been prepared from H2Pda and Phen at room temperature and characterized by IR, elemental analysis, X-ray powder diffraction, and single-crystal X-ray diffraction. Structure analysis shows that each Cu(II) is coordinated by two Phen ligands and one Pda ligand to complete a octahedron CuN5O chromophore. In addition, a unique water networks paralleling to (001) composed by the crystallization water through hydrogen bonds play a important role in the stability of crystal structure. The crystal structure is found to be orthorombic with space group Pbcn and cell parameters a = 13.651(4), b = 22.516(7), c = 22.386(7) A, R1 = 0.0735 and wR2 = 0. 0.1935.

Synthesis and Crystal Structure of a Polymeric Silver(I) Complex with 4-Chlorobenzoate and N-Propylethane-1,2-diamine

A polymeric silver(I) complex with the formula [Ag(PDA)] n ·n(CA)·n(H2O), where PDA is N-propylethane-1,2-diamine, and CA is 4-chlorobenzoate, was prepared and characterized by single crystal X-ray diffraction. The asymmetric unit of the complex contains a [Ag(PDA)]+ cation, a CA anion, and a water molecule of crystallization. The Ag atom is coordinated by two N atoms from two PDA ligands, forming a linear geometry. The adjacent Ag atoms are linked through PDA ligands, forming chains along the unit cell a axis. The CA anions are linked to the [Ag(PDA)]+ cations through intermolecular N–H···O and O–H···O hydrogen bonds. The water molecules reside in the lattice of the structure, linked to the [Ag(PDA)]+ cations and the CA anions via intermolecular N–H···O and O–H···O hydrogen bonds. The complex shows strong cytotoxic properties to several carcinoma cells.

Synthesis and Crystal Structure of a Polynuclear Silver(I) Complex with 4,4’-Biphenyldicarboxylate and N-Propylethane-1,2-diamine

A polynuclear silver(I) complex with the formula [Ag(PDA)]2n·nBPC·nH2O, where PDA is N-propylethane-1,2-diamine, and BPC is 4,4′-biphenyldicarboxylate, was prepared and characterized by single crystal X-ray diffraction. The asymmetric unit of the complex possesses two [Ag(PDA)] complex cations, one BPC anion, and two water molecules of crystallization. The PDA ligands coordinate to the silver atoms through the N atoms, which link the silver atoms to form a 1D chain. The crystal of the complex is stabilized by intermolecular N–H···O and O–H···O hydrogen bonds. The complex shows strong cytotoxic property to the carcinoma cells.

Poly[diaquatris(μ4-1,3-phenylenediacetato)dineodymium(III)

In the title coordination polymer, [Nd2(C10H8O4)3(H2O)2]n, each of the two NdIII ions is nine-coordinated by eight O atoms from six different 2,2′-(m-phenyl­ene)diacetate (pda) bivalent anions and by one O atom from a water mol­ecule, forming a distorted tricapped trigonal–prismatic coordination geometry. Eight NdIII ions and 12 pda ligands form a large [Nd8(pda)12] ring, and four NdIII ions and six pda ligands form a small [Nd4(pda)6] ring. These rings are further connected by the coordination inter­actions of pda ligands and NdIII, generating a three-dimensional supra­molecular framework.

Poly[diaquatris(μ4-1,3-phenylenediacetato)dicerium(III)

In the title coordination polymer, [Ce2(C10H8O4)3(H2O)2]n, each CeIII atom is nine-coordinated by eight O atoms from six different 1,3-phenyl­enediacetate (pda) bivalent anions and one O atom from a coordinated water mol­ecule, forming a distorted tricapped trigonal–prismatic coordination geometry. Eight CeIII ions and twelve pda ligands form a large [Ce8(pda)12] ring, and four CeIII ions and six pda ligands form a small [Ce4(pda)6] ring. The rings are further connected by the coordination inter­actions of pda ligands and CeIII, generating a three-dimensional supra­molecular framework.

Syntheses and Crystal Structures of Two New Cadmium(II) and Nickel(II) Complexes with 1,4-Phenylenediacetate and 2,2′-Bipyridyl-Like Ligands

Two new complexes, namely [Cd(PDA)0.5(2,2′-bpy)Cl](H2PDA) (1) and [Ni(PDA)(phen)(H2O)]2 (2) (H2PDA = 1,4-phenylenediacetic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized by elemental analysis, IR spectra and X-ray crystal diffraction. Single-crystal X-ray diffraction analysis shows that complex 1 crystallizes in the triclinic space group P-1 with unit cell dimensions a = 8.760 (4) A, b = 11.190 (5) A, c = 13.917 (7) A, α = 110.383 (5)°, β = 101.736 (5)°, γ = 100.612 (5)°, V = 1202.8 (10) A3, Z = 2, R 1 = 0.0314 and wR 2 = 0.0898. Complex 2 crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 9.911 (3) A, b = 17.924 (6) A, c = 10.638 (4) A, β = 94.998 (5)°, V = 1882.7 (11) A3, Z = 2, R 1 = 0.0397 and wR 2 = 0.1150. In complex 1, Cd(II) ions are alternately bridged by PDA ligands and chloride ions into 1D chains and the PDA ligands display trans-configuration. Complex 2 is a dimer and two Ni(II) ions are linked by two PDA ligands with cis-configuration, resulting in a cyclic structure. In spite of these differences, both in complexes 1 and 2 there are π–π stacking interactions and hydrogen bonding to make them 3D supramolecular frameworks. Two new complexes [Cd(PDA)0.5(2,2′-bpy)Cl](H2PDA) and [Ni(PDA)(phen)(H2O)]2 (H2PDA = 1,4-phenylenediacetic acid, phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridine) were obtained and their structures were determined by single crystal X-ray diffraction. In complex [Cd(PDA)0.5(2,2′-bpy)Cl](H2PDA), Cd(II) ions are alternately bridged by PDA ligands and chloride ions into 1D chains and the PDA ligands display trans-configuration. The complex [Ni(PDA)(phen)(H2O)]2 is the first nickel(II) complex constructed by H2PDA. And two Ni(II) ions in one unit are linked by two PDA ligands with cis-configuration, resulting in a cyclic structure.