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

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ABSTRACT

1234123412,4314: 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 (), [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (DMF = N, N-Dimethylformamide) (), [Pb2Cl2(TPAA)H2O] (), and [Pb3Cl(TPAA)(HTPAA)2H2O]Cl (). 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 and represent two-dimensional (2D) layered structures whilst and form three-dimensional (3D) frameworks. The structures of , and contain one-dimensional (1D) {PbII/AsO3} substructures, while is composed of 2D {PbII/AsO3} arrays. Besides their interesting topologies, – all exhibit photoluminescence properties in the solid state at room temperature.

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(a) The coordination environment of Pb(II) ions and the coordination modes of ligands in 1. Symmetry codes: (i) −x, −y + 1, −z; (ii) x, y + 1, z; (iii) −x, −y + 2, −z; (iv) x, y−1, z; (v) −x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2. (b) Polyhedral representation of the 1D substructure comprising Pb(II) ions, the two different AsO3 functionalities, and the NO3– anion in 1. (c) Polyhedral representation of the 2D layer structure of 1.
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Figure 1: (a) The coordination environment of Pb(II) ions and the coordination modes of ligands in 1. Symmetry codes: (i) −x, −y + 1, −z; (ii) x, y + 1, z; (iii) −x, −y + 2, −z; (iv) x, y−1, z; (v) −x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2. (b) Polyhedral representation of the 1D substructure comprising Pb(II) ions, the two different AsO3 functionalities, and the NO3– anion in 1. (c) Polyhedral representation of the 2D layer structure of 1.

Mentions: [Pb2(TPAA)(HTPAA)(NO3)]·6H2O (1) Compound 1 crystallizes in the monoclinic space group C2/c. The asymmetric unit consists of two Pb(II) ions, one fully deprotonated TPAA2– ligand, one HTPAA– anion (denoted as LAs11 and LAs21), one NO3– anion, one coordinated water molecule, and five lattice water molecules (the occupancies of O6W and O7W are both 0.5) (SI, figure S1(a)). Both two Pb(II) ions are in hemidirected coordination spheres. The Pb1(II) ion is five-coordinate with four arsonate oxygen atoms and one nitrogen atom deriving from five different ligands. The Pb2(II) ion is six-coordinate, whereby three arsonate oxygen atoms originate from three different ligands, two oxygen atoms from a NO3– anion and one water molecule. The Pb–O distances (2.331(5)–2.706(4) Å) are close to those reported for other lead(II) organo arsonates [68, 69]. The long distance of the Pb1–N21v bond (2.8372 (77) Å) is comparable to some corresponding long Pb–N bonds reported in the literature [81–83]. The As–O distances of the {As11O3} group are 1.684(5), 1.686(5), and 1.687(5) and of {As21–O} are 1.666(5), 1.667(5), and 1.735(5) Å. Considering the charge balance of 1, and the fact that the As21–O23 (1.735(5) Å) bond is the longest among these As–O bonds, O23 was assigned as a hydroxyl oxygen atom. According to the research of Shimoni-Livny et al [84], the repulsion effect of the 6s2 lone pair electrons may result in long bonds and weak coordinative binding interactions involving Pb(II) ions. In light of these results, we have used a bond order calculation [85] to further characterize the coordination environment of the Pb(II) center in 1. The valence of Pb1 associated with the four Pb–O bonds is 1.675. Further calculations including the weak Pb1–N21v interaction increase the valence of Pb1 from 1.675 to 1.864; the valence of Pb2 is 1.907, which is calculated considering all the six Pb2–O bonds (the calculated valence contribution of the long Pb2–O31 interaction (2.8821(49)) Å is 0.1248). LAs11 and LAs21 adopt (κO11, O11-κO12, O12-κO13)-μ5 and (κO21-κO22-κN21)-μ3 coordination modes, respectively (figure 1(a)). The two different {AsO3} functionalities of LAs11 and LAs21 link the Pb(II) ions in 1 into 1D chains that extend in the direction of the crystallographic c-axis (figure 1(b)) and are connected to each other by a LAs21 spacer to form a 2D layer structure (figure 1(c)). Further, parallel aligned 2D layers stack in the direction of the crystallographic b-axis in an ABC fashion to form a 3D supramolecular architecture through hydrogen-bonds involving the H-bond donor/acceptor pairs O2W—H2WA···N22v and O7W—H7WB···N11vii [Symmetry codes: (v) –x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2]. Strong hydrogen-bond interactions also occur between the water molecules (SI, figure S1(b)).


Photoluminescent lead(II) coordination polymers stabilised by bifunctional organoarsonate ligands
(a) The coordination environment of Pb(II) ions and the coordination modes of ligands in 1. Symmetry codes: (i) −x, −y + 1, −z; (ii) x, y + 1, z; (iii) −x, −y + 2, −z; (iv) x, y−1, z; (v) −x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2. (b) Polyhedral representation of the 1D substructure comprising Pb(II) ions, the two different AsO3 functionalities, and the NO3– anion in 1. (c) Polyhedral representation of the 2D layer structure of 1.
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Figure 1: (a) The coordination environment of Pb(II) ions and the coordination modes of ligands in 1. Symmetry codes: (i) −x, −y + 1, −z; (ii) x, y + 1, z; (iii) −x, −y + 2, −z; (iv) x, y−1, z; (v) −x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2. (b) Polyhedral representation of the 1D substructure comprising Pb(II) ions, the two different AsO3 functionalities, and the NO3– anion in 1. (c) Polyhedral representation of the 2D layer structure of 1.
Mentions: [Pb2(TPAA)(HTPAA)(NO3)]·6H2O (1) Compound 1 crystallizes in the monoclinic space group C2/c. The asymmetric unit consists of two Pb(II) ions, one fully deprotonated TPAA2– ligand, one HTPAA– anion (denoted as LAs11 and LAs21), one NO3– anion, one coordinated water molecule, and five lattice water molecules (the occupancies of O6W and O7W are both 0.5) (SI, figure S1(a)). Both two Pb(II) ions are in hemidirected coordination spheres. The Pb1(II) ion is five-coordinate with four arsonate oxygen atoms and one nitrogen atom deriving from five different ligands. The Pb2(II) ion is six-coordinate, whereby three arsonate oxygen atoms originate from three different ligands, two oxygen atoms from a NO3– anion and one water molecule. The Pb–O distances (2.331(5)–2.706(4) Å) are close to those reported for other lead(II) organo arsonates [68, 69]. The long distance of the Pb1–N21v bond (2.8372 (77) Å) is comparable to some corresponding long Pb–N bonds reported in the literature [81–83]. The As–O distances of the {As11O3} group are 1.684(5), 1.686(5), and 1.687(5) and of {As21–O} are 1.666(5), 1.667(5), and 1.735(5) Å. Considering the charge balance of 1, and the fact that the As21–O23 (1.735(5) Å) bond is the longest among these As–O bonds, O23 was assigned as a hydroxyl oxygen atom. According to the research of Shimoni-Livny et al [84], the repulsion effect of the 6s2 lone pair electrons may result in long bonds and weak coordinative binding interactions involving Pb(II) ions. In light of these results, we have used a bond order calculation [85] to further characterize the coordination environment of the Pb(II) center in 1. The valence of Pb1 associated with the four Pb–O bonds is 1.675. Further calculations including the weak Pb1–N21v interaction increase the valence of Pb1 from 1.675 to 1.864; the valence of Pb2 is 1.907, which is calculated considering all the six Pb2–O bonds (the calculated valence contribution of the long Pb2–O31 interaction (2.8821(49)) Å is 0.1248). LAs11 and LAs21 adopt (κO11, O11-κO12, O12-κO13)-μ5 and (κO21-κO22-κN21)-μ3 coordination modes, respectively (figure 1(a)). The two different {AsO3} functionalities of LAs11 and LAs21 link the Pb(II) ions in 1 into 1D chains that extend in the direction of the crystallographic c-axis (figure 1(b)) and are connected to each other by a LAs21 spacer to form a 2D layer structure (figure 1(c)). Further, parallel aligned 2D layers stack in the direction of the crystallographic b-axis in an ABC fashion to form a 3D supramolecular architecture through hydrogen-bonds involving the H-bond donor/acceptor pairs O2W—H2WA···N22v and O7W—H7WB···N11vii [Symmetry codes: (v) –x + 1/2, y−1/2, −z + 1/2; (vii) −x + 1/2, y + 1/2, −z + 1/2]. Strong hydrogen-bond interactions also occur between the water molecules (SI, figure S1(b)).

View Article: PubMed Central - PubMed

ABSTRACT

1234123412,4314: 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 (), [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (DMF = N, N-Dimethylformamide) (), [Pb2Cl2(TPAA)H2O] (), and [Pb3Cl(TPAA)(HTPAA)2H2O]Cl (). 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 and represent two-dimensional (2D) layered structures whilst and form three-dimensional (3D) frameworks. The structures of , and contain one-dimensional (1D) {PbII/AsO3} substructures, while is composed of 2D {PbII/AsO3} arrays. Besides their interesting topologies, – all exhibit photoluminescence properties in the solid state at room temperature.

No MeSH data available.