Synthesis, Crystal Structures, and Photophysical Properties of Two Novel Lead(II)–SIP Coordination Polymers (NaH2SIP = 5-Sulfoisophthalic Acid Monosodium Salt) Containing Tetranuclear Lead(II) Units

Multifunctional Luminescent Sensor Based on the Pb2+ Complex Containing a Tetrazolato Ligand

A series of luminescent Pb²⁺ complexes, [Pb(L¹)₂]_n (1), [Pb(L²)₂]_n (2), [Pb(L³)(NO₃)(H₂O)₂]_n (3), [Pb(L³)(Br)(H₂O)]_n (4), [Pb(L³)(Cl)(H₂O)]_n (5), and [Pb(L⁴)(H₂O)₂] (6) have been synthesized by treatment of polydentate tetrazolato ligands with various hydrated Pb²⁺ salts (HL¹ = 2-(1H-tetrazol-5-yl)pyridine, HL² = 3-(1H-tetrazol-5-yl)isoquinoline, HL³ = 6-(1H-tetrazol-5-yl)-2,2'-bipyridine, and H₂L⁴ = 6,6'-bis(1H-tetrazol-5-yl)-2,2'-bipyridine). These complexes have been characterized by IR, TGA, and elemental analysis. Their crystal structures have been determined by X-ray crystallography, and the phase purity of bulk samples were further confirmed by PXRD. Their luminescence properties have been investigated in detail, and their emission origin may involve ligand-centered π-π* transition, metal-centered s-p transition and charge-transfer character. It is interesting to note that 5 exhibits obviously enhanced red-shifted emission, whose photoluminescence quantum yield (PLQY = 16.5%) is much higher than the other compounds (≤2%). Most importantly, the emission property of 5 was strongly affected by temperature. When the temperature rises from 295 to 493 K, the emission maximum gradually shifts to high energy due to the loss of the aqua ligand. In contrast, when the temperature is lowered from 295 to 13 K, two emission bands were observed. The low-energy emission band exhibits a slight blue shift, while a new high-energy emission band appears at around 520 nm, which is assigned to ligand-centered phosphorescence. After removal of the coordinated aqua ligand, the emission of 5-H₂O is very sensitive to the vapors of volatile primary amines and acids, although they have different response mechanisms. This result indicates that 5-H₂O may be a potential multifunctional sensor for temperature, volatile amines, and acids. To decipher the emission origin, DFT calculations have also been carried out based on the structure units of these compounds.

Exploring thiophene-2-acetate and thiophene-3-acetate binding modes towards the molecular and supramolecular structures and photoluminescence properties of Pb(ii) polymers

The isomeric ligands thiophene-2(3)-acetate as linkers were used to construct Pb(ii) coordination polymers with an intriguing structure, noncovalent interactions, topology and interesting photoluminescence properties.

Lead(ii) soaps: crystal structures, polymorphism, and solid and liquid mesophases

The long-chain members of the lead(ii) alkanoate series or soaps, from octanoate to octadecanoate, have been thoroughly characterized by means of XRD, PDF analysis, DSC, FTIR, ssNMR and other techniques, in all their phases and mesophases. The crystal structures at room temperature of all of the members of the series are now solved, showing the existence of two polymorphic forms in the room temperature crystal phase, different to short and long-chain members. Only nonanoate and decanoate present both forms, and this polymorphism is proven to be monotropic. At higher temperature, these compounds present a solid mesophase, defined as rotator, a liquid crystal phase and a liquid phase, all of which have a similar local arrangement. Since some lead(ii) soaps appear as degradation compounds in oil paintings, the solved crystal structures of lead(ii) soaps can now be used as fingerprints for their detection using X-ray diffraction. Pair distribution function analysis on these compounds is very similar in the same phases and mesophases for the different members, showing the same short range order. This observation suggests that this technique could also be used in the detection of these compounds in disordered phases or in the initial stages of formation in paintings.

Hemi- and holo-directed lead(II) complexes in a soft ligand environment

To investigate the geometry and stereochemical activity of the lone pair at the lead atom, lead(ii) complexes () with one tripodal (L(1)), one dipodal (L(2)) boron-centred soft ligand and eight other small soft heterocyclic ligands, 2-mercaptobenzimidazole (L(3)), 2-mercapto-5-methylbenzimidazole (L(4)), 3-mercapto-1,2,4-triazole (L(5)H), 3-mercapto-4-methyl-1,2,4-triazole (L(6)), 2-mercapto-1,3,4-thiadiazole (L(7)H), 2-mercapto-5-methyl-1,3,4-thiadiazole (L(8)H), 5-mercapto-1-methyltetrazole (L(9)H) and 2-mercapto-4-phenylthiazole (L(10)H) were prepared. The structures of these complexes were elucidated on the basis of X-ray crystallography, elemental analyses as well as (1)H NMR, (1)H DOSY, (13)C NMR and (207)Pb NMR spectroscopy. The coordination numbers of these complexes vary from 4 to 8. The majority of the complexes are polymeric and possess a hemi-directed environment around the lead atoms. Solution studies revealed that most of the complexes are dissociated in highly polar solvents. Most of the complexes are emissive both under ambient conditions and at 77 K in the solid state. However, no obvious relationship between their solid state structures and luminescence behaviour with respect to the nature of the excited state could be identified.

Photoluminescent lead(II) coordination polymers stabilised by bifunctional organoarsonate ligands

Four lead(II) coordination polymers were isolated under hydro(solvo)thermal conditions. The applied synthetic methodology takes advantage of the coordination behaviour of a new bifunctional organoarsonate ligand, 4-(1, 2, 4-triazol-4-yl)phenylarsonic acid (H2TPAA) and involves the variation of lead(II) reactants, metal/ligand mole ratios, and solvents. The constitutional composition of the four lead(II) coordination polymers can be formulated as [Pb2(TPAA)(HTPAA)(NO3)]·6H2O (1), [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (DMF = N, N-Dimethylformamide) (2), [Pb2Cl2(TPAA)H2O] (3), and [Pb3Cl(TPAA)(HTPAA)2H2O]Cl (4). The compounds were characterized by single-crystal and powder x-ray diffraction techniques, thermogravimetric analyses, infra-red spectroscopy, and elemental analyses. Single-crystal x-ray diffraction reveals that 1 and 2 represent two-dimensional (2D) layered structures whilst 3 and 4 form three-dimensional (3D) frameworks. The structures of 1, 2, and 4 contain one-dimensional (1D) {PbII/AsO3} substructures, while 3 is composed of 2D {PbII/AsO3} arrays. Besides their interesting topologies, 1-4 all exhibit photoluminescence properties in the solid state at room temperature.

catena-[[(nitrato-κO)silver(I)]-μ-1,10-phenanthroline-5,6-dione-κO,O':N,N']

In the title one-dimensional coordination polymer, [Ag(NO₃)(C₁₂H₆N₂O₂)]_n, the Ag^I atom is penta­coordinated by two N atoms from a 1,10-phenanthroline-5,6-dione (phen-dione) ligand, one O atom from the nitrate anion and two O atoms from another phen-dione ligand. The coordination environment around silver is slightly distorted square-pyramidal. Inter­estingly, the Ag—O distances to the phen-dione ligand are different [Ag—O = 2.612 (6) and 2.470 (5) Å]. The one-dimensional chains run parallel to [101] and are further inter­connected by weak hydrogen bonds (C—H⋯O) and π–π stacking inter­actions [centroid–centroid distances 3.950 (4) and 3.792 (4) Å], forming a three-dimensional supra­molecular network.

Poly[(μ(2)-4,4'-bipyridine)(μ(2)-3,5-dicarboxybenzenesulfonato)silver(I)]

In the title compound, [Ag(C(8)H(5)O(7)S)(C(10)H(8)N(2))](n), the Ag atom is tetra-coordinated by two 4,4'-bipydidine (4,4'-bipy) N atoms and two monodentate sulfonate O atoms of the 5-sulfoisophthalic acid (H(3)sip) ligands. Adjacent Ag atoms are bonded through four sulfonate O atoms, forming a dinuclear unit with an Ag⋯Ag separation of 3.384 (5) Å; they are further linked together by the 4,4'-bipy lignds into a chain. Classical inter-molecular O-H⋯O and non-classical intra-molecular C-H⋯O hydrogen bonds are also observed in the two-dimensional supra-molecuar structure.

Structure and Characterization of a Novel 3D Lead Phosphonate Metal - Organic Framework with Cationic Layer Based on Weak Pb - O(N) Contact

A novel lead-phosphonate, [Pb2(HL)]·(NO3)·2(H2O) 1 (H4L = H2O3PCH2N(C4H8)NCH2PO3H2 N,N′-piperazinebis(methylenephosphonic acid), so HL = O3PCH2NH(C4H8)NCH2PO3), has been hydrothermally synthesized and characterized by elemental analysis, IR, TG-DTA, and X-ray single-crystal diffraction. Compound 1 possesses a 2D cationic layer structure built from inorganic chains with three types of eight-membered rings arranged in an ABAC manner. In 1, both crystallographic distinct Pb(II) ions adopt three-coordination geometry, and a counter anion NO3 – and two lattice water molecules occupy the voids between 2D layers. After the removal of solvent, the size of tunnel formed by 2D layers is 137.9 Å3 per unit cell, comprising 17.0% of the crystal volume based on the crystal structure. When the bond length of Pb–O(N) extended to 3.10 Å, a 3D metal–organic framework was constructed via long Pb–O(N) contacts, simultaneously accompanied by the hemi- to holo-directed transition in coordination geometry of Pb(II). Except for the long Pb–O contacts, a 3D supramolecular network is also formed by hydrogen bonds (N–H···O, O–H···O, and C–H···O), van der Waals forces as well as electrostatic interactions. The result of fluorescence measurements indicates that 1 shows a fluorescent emission band at 465 nm (λexcitation = 215 nm).

A series of silver(I) pyridone-sulfonates with 1-D "butterfly" chain, 2-D lamellar network and 3-D pillared layered frameworks: syntheses, structures and characterizations

A series of silver(I) pyridone-sulfonates, namely [Ag5(HL1)3(NO3)2(H2O)]n (1) [Ag2(HL1)2]n.2nH2O (2), [Ag2(HL1)(NO3)]n (3), and [Ag3(HL2)2(NO3)(H2O)]n (4) (HL1 = 4(1H)-pyridone-3-sulfonate monoanion, HL2 = 2(1H)-pyridone-5-sulfonate monoanion), have been synthesized and characterized by elemental analyses, IR, TG, PL and X-ray analyses. Complex 1, which exhibits a novel continuous silver polyhedral framework containing four kinds of coordination spheres, has been recently reported. Complex 2 presents the first one-dimensional (1-D) "butterfly" array composed of SO3-bridged columns of Ag(I) ions and symmetric pendant organic groups in silver(I) sulfonates, while complex 3 possesses a two-dimensional (2-D) layer structure in which the inorganic network substructure consists of helical chains of edge-sharing Ag1 distorted octahedra linked through dimers of edge-sharing Ag2 distorted anti-trigonal prisms by sharing two corners and two edges. Replacing H2L1 by H2L2 leads to the formation of complex 4, a three-dimensional (3-D) pillared layered framework, which is also extended by the rare mu4 nitrate anion. In complexes 1-4, all the inorganic parts can be considered as being built up from versatile polyhedra of silver(I) centers by sharing corners, edges or faces. The sulfonic group shows some novel coordination modes, which is first reported here. Solid-state fluorescence quenching and thermal stability are discussed for all of these complexes.