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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 the Pb(II) ions and the coordination modes of the ligands in 2. Symmetry codes: (i) x, y−1, z; (ii) x + 1, y, z; (iii) −x, −y, −z + 1; (iv) −x + 1, −y + 1, −z + 1; (v) x−1, y, z; (vi) x, y + 1, z; (vii) –x, 1-y, 1-z. (b) Polyhedral representation of the one-dimensional sub-structure in 2 comprising of Pb(II) ions and the three different {AsO3} functionalities (view in the direction of the crystallographic b-axis). (c) Polyhedral representation of the two-dimensional structure in 2 (view in the direction of the crystallographic b-axis).
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Figure 2: (a) The coordination environment of the Pb(II) ions and the coordination modes of the ligands in 2. Symmetry codes: (i) x, y−1, z; (ii) x + 1, y, z; (iii) −x, −y, −z + 1; (iv) −x + 1, −y + 1, −z + 1; (v) x−1, y, z; (vi) x, y + 1, z; (vii) –x, 1-y, 1-z. (b) Polyhedral representation of the one-dimensional sub-structure in 2 comprising of Pb(II) ions and the three different {AsO3} functionalities (view in the direction of the crystallographic b-axis). (c) Polyhedral representation of the two-dimensional structure in 2 (view in the direction of the crystallographic b-axis).

Mentions: [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (2) Single-crystal x-ray diffraction measurements reveal that compound 2 crystallizes in the triclinic space group P-1. The asymmetric unit of 2 consists of two Pb(II) ions, one fully deprotonated TPAA2– ligand, two HTPAA– anions (denoted as LAs11, LAs21, and LAs31), one lattice DMF molecule, and half a lattice water molecule (figure S2(a)). If the long Pb1–O31iv (2.9358 (29) Å) is taken into consideration, the Pb1(II) ion is in a holodirected coordination sphere which is six-coordinate with six arsonate oxygen atoms deriving from six different ligands. The Pb2(II) ion is in a hemidirected coordination sphere that is completed by four arsonate oxygen atoms and one nitrogen atom that are provided by five different ligands. The Pb–O distances (2.236(2)–2.671(2) Å) are in the expected range. The Pb2–N31 distance (2.676(3) Å) is much shorter than the previously discussed bond in 1. When only the relatively strong Pb–O bonds (Pb–O < 2.88 Å) are taken into account, the valence of Pb1 is 1.828. Further calculation demonstrates that the long Pb1–O31iv bond has a considerable contribution, increasing the valence to 1.936. The valence of Pb2 calculated from the existing Pb–O bonds and the Pb2–N31 bond is 2.02, which is very close to the assumed oxidation state of the Pb(II) ion. The longest As–O bonds in the respective {AsO3} groups are As11–O13 1.742(3), As21–O23 1.699(2), and As31–O33 1.709(3) Å, so, considering the charge balance of 2, O13 and O33 were assigned as hydroxyl atoms. LAs11, LAs21, and LAs31 adopt κO11-μ1, (κO21-κO22, O22-κO23, O23)-μ5, and (κO31, O31-κO32, O32-κN31)-μ5 coordination modes, respectively (figure 2(a)). The three different {AsO3} functionalities from LAs11, LAs21, and LAs31 link the Pb(II) ions into 1D chains that extend in the direction of the crystallographic b-axis (figure 2(b)) and which are connected to each other by an LAs31 spacer to form a 2D layer structure (figure 2(c)). There are two distinct, strong intramolecular hydrogen-bond interactions in 2 that occur within the 2D layer between OH functionalities (O13 and O33) of the AsO3 groups and deprotonated oxygen atoms (O23 and O12) of neighbouring AsO3 groups. These H-bonds are characterized by O13–H13···O23 and O33–H33···O12vi distances of 2.649(4) and 2.493(4) Å, respectively [symmetry codes: (vi) x, y + 1, z] (figure S2(b)).


Photoluminescent lead(II) coordination polymers stabilised by bifunctional organoarsonate ligands
(a) The coordination environment of the Pb(II) ions and the coordination modes of the ligands in 2. Symmetry codes: (i) x, y−1, z; (ii) x + 1, y, z; (iii) −x, −y, −z + 1; (iv) −x + 1, −y + 1, −z + 1; (v) x−1, y, z; (vi) x, y + 1, z; (vii) –x, 1-y, 1-z. (b) Polyhedral representation of the one-dimensional sub-structure in 2 comprising of Pb(II) ions and the three different {AsO3} functionalities (view in the direction of the crystallographic b-axis). (c) Polyhedral representation of the two-dimensional structure in 2 (view in the direction of the crystallographic b-axis).
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Figure 2: (a) The coordination environment of the Pb(II) ions and the coordination modes of the ligands in 2. Symmetry codes: (i) x, y−1, z; (ii) x + 1, y, z; (iii) −x, −y, −z + 1; (iv) −x + 1, −y + 1, −z + 1; (v) x−1, y, z; (vi) x, y + 1, z; (vii) –x, 1-y, 1-z. (b) Polyhedral representation of the one-dimensional sub-structure in 2 comprising of Pb(II) ions and the three different {AsO3} functionalities (view in the direction of the crystallographic b-axis). (c) Polyhedral representation of the two-dimensional structure in 2 (view in the direction of the crystallographic b-axis).
Mentions: [Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (2) Single-crystal x-ray diffraction measurements reveal that compound 2 crystallizes in the triclinic space group P-1. The asymmetric unit of 2 consists of two Pb(II) ions, one fully deprotonated TPAA2– ligand, two HTPAA– anions (denoted as LAs11, LAs21, and LAs31), one lattice DMF molecule, and half a lattice water molecule (figure S2(a)). If the long Pb1–O31iv (2.9358 (29) Å) is taken into consideration, the Pb1(II) ion is in a holodirected coordination sphere which is six-coordinate with six arsonate oxygen atoms deriving from six different ligands. The Pb2(II) ion is in a hemidirected coordination sphere that is completed by four arsonate oxygen atoms and one nitrogen atom that are provided by five different ligands. The Pb–O distances (2.236(2)–2.671(2) Å) are in the expected range. The Pb2–N31 distance (2.676(3) Å) is much shorter than the previously discussed bond in 1. When only the relatively strong Pb–O bonds (Pb–O < 2.88 Å) are taken into account, the valence of Pb1 is 1.828. Further calculation demonstrates that the long Pb1–O31iv bond has a considerable contribution, increasing the valence to 1.936. The valence of Pb2 calculated from the existing Pb–O bonds and the Pb2–N31 bond is 2.02, which is very close to the assumed oxidation state of the Pb(II) ion. The longest As–O bonds in the respective {AsO3} groups are As11–O13 1.742(3), As21–O23 1.699(2), and As31–O33 1.709(3) Å, so, considering the charge balance of 2, O13 and O33 were assigned as hydroxyl atoms. LAs11, LAs21, and LAs31 adopt κO11-μ1, (κO21-κO22, O22-κO23, O23)-μ5, and (κO31, O31-κO32, O32-κN31)-μ5 coordination modes, respectively (figure 2(a)). The three different {AsO3} functionalities from LAs11, LAs21, and LAs31 link the Pb(II) ions into 1D chains that extend in the direction of the crystallographic b-axis (figure 2(b)) and which are connected to each other by an LAs31 spacer to form a 2D layer structure (figure 2(c)). There are two distinct, strong intramolecular hydrogen-bond interactions in 2 that occur within the 2D layer between OH functionalities (O13 and O33) of the AsO3 groups and deprotonated oxygen atoms (O23 and O12) of neighbouring AsO3 groups. These H-bonds are characterized by O13–H13···O23 and O33–H33···O12vi distances of 2.649(4) and 2.493(4) Å, respectively [symmetry codes: (vi) x, y + 1, z] (figure S2(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)]&middot;6H2O (), [Pb2(TPAA)(HTPAA)2]&middot;DMF&middot;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, &ndash; all exhibit photoluminescence properties in the solid state at room temperature.

No MeSH data available.