Ligand-Driven Coordination Sphere-Induced Engineering of Hybride

Article pubs.acs.org/IC

Ligand-Driven Coordination Sphere-Induced Engineering of Hybride Materials Constructed from PbCl2 and Bis-Pyridyl Organic Linkers for Single-Component Light-Emitting Phosphors Ghodrat Mahmoudi,*,†,‡ Atash V. Gurbanov,‡,§ Sabina Rodríguez-Hermida,∥ Rosa Carballo,∥ Mojtaba Amini,† Alessia Bacchi,⊥ Mariusz P. Mitoraj,*,# Filip Sagan,# Mercedes Kukułka,# and Damir A. Safin*,∇ †

Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran Organic Chemistry Department, RUDN University, Miklukho-Maklaya str. 6, 117198 Moscow, Russian Federation § Department of Chemistry, Baku State University, Z. Xalilov Str. 23, AZ1148 Baku, Azerbaijan ∥ Departamento de Química Inorgánica, Facultade de Química, Universidade de Vigo, 36310 Vigo, Galicia, Spain ⊥ Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale, Università di Parma, Viale delle Scienze 11A, 43124 Parma, Italy # Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, R. Ingardena 3, 30-060 Cracow, Poland ∇ Institute of Condensed Matter and Nanosciences, Molecules, Solids and Reactivity (IMCN/MOST), Université catholique de Louvain, Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium ‡

S Supporting Information *

ABSTRACT: We report design and structural characterization of six new coordination polymers fabricated from PbCl2 and a series of closely related bis-pyridyl ligands LI and HLII−HLVI, namely, [Pb2(LI)Cl4]n, [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, [Pb2(LIV)Cl3]n, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOH. The topology of the obtained networks is dictated by the geometry of the organic ligand. The structure of [Pb2(LI)Cl4]n is constructed from the [PbCl2]n two-dimensional (2D) sheets, linked through organic linkers into a three-dimensional framework, which exhibits a unique binodal 4,7-connected three-periodic topology named by us as sda1. Topological analysis of the 2D metal−organic sheet in [Pb(HLII)Cl2]n·nMeOH discloses a binodal 3,4-connected layer topology, regardless of the presence of tetrel bonds. A one-dimensional (1D) coordination polymer [Pb(HLIII)Cl2]n·0.5 nMeOH is considered as a uninodal 2-connected chain. The overall structure of [Pb2(LIV)Cl3]n is constructed from dimeric tetranuclear [Pb4(μ3-LIV-κ6N:N′:N″:μ3-O)2(μ4-Cl)(μ2-Cl)2]3+ cationic blocks linked in a zigzag manner through bridging μ2-Cl− ligands, yielding a 1D polymeric chain. Topological analysis of this chain reveals a unique pentanodal 3,4,4,5,6-connected chain topology named by us as sda2. The structure of [Pb(HLV)Cl2]n exhibits a 1D zigzaglike polymeric chain. Two chains are further linked into a 1D gridlike ribbon through the dimeric [Pb2(μ2-Cl)2Cl2] blocks as bridging nodes. With the bulkiest ligand HLVI, a 2D layered coordination polymer [Pb3(LVI)2Cl4]n·nMeOH is formed, which network, considering all tetrel bonds, reveals a unique heptanodal 3,3,3,3,4,5,5-connected layer topology named by us as sda3. Compounds [Pb2(LI)Cl4]n, [Pb2(LIV)Cl3]n, and [Pb(HLV)Cl2]n were found to be emissive in the solid state at ambient temperature. While blue emission of [Pb2(LI)Cl4]n is due to the ligand-centered transitions, bluish-green and white luminescence of [Pb2(LIV)Cl3]n and [Pb(HLV)Cl2]n, respectively, was assigned to ligand-to-metal charge transfer mixed with metal-centered excited states. Molecular as well as periodic calculations were additionally applied to characterize the obtained polymers.

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replace existing mercury-containing fluorescent lights. The ability to use a single white light-emitting phosphor clearly would be advantageous. As such, different types of singlecomponent white light-emitting materials, fabricated from

INTRODUCTION

During the past few decades, rapid progress in the design of photoluminscent coordination compounds for emitting devices has been observed.1−9 The development of white light-emitting materials is an important target of solid-state lighting research, as these materials, coupled with the appropriate phosphors, offer long lifetime, significant energy savings, and are on track to © 2017 American Chemical Society

Received: May 12, 2017 Published: July 28, 2017 9698

DOI: 10.1021/acs.inorgchem.7b01189 Inorg. Chem. 2017, 56, 9698−9709

Article

Inorganic Chemistry coordination compounds, have been developed.10−16 In this connection, PbII-based coordination complexes are of interest, since PbII, being a heavy p-block metal ion, possesses a stereochemically active lone pair (6s26p0 electron configuration), which can lead both to interesting structures and luminescence properties.17−22 The stereochemically active lone pair plays a crucial role in the chemistry of PbII, which arises from the unique ability of this ion to participate in the formation of tetrel bonds.23 This supramolecular interaction is formed between a positively charged region on a group 14 atom in continuation of a covalent bond (σ-hole) and an electron donor, analogously to a more common halogen bond. PbII is particularly prone to the formation of tetrel bonds because of its size and polarizability, as well as its specific hemidirectional coordination,24 which leaves a gap in the coordination sphere of the PbII cation (Chart 1), thus

three-dimensional (3D) metal−organic framework in [Pb2(LI)Cl4]n. We also demonstrated how an alteration of the orientations of terminal pyridine groups and the bulkiness of the ligand may control the dimensionality and topology of the metal−organic network. Furthermore, the resulting topology of both [Pb(HLV)Cl2]n and [Pb3(LVI)2Cl4]n·nMeOH is highly dictated by the Pb···Cl, in the former structure, and Pb···Cl and Pb···N, in the latter structure, tetrel bonds, highlighting their crucial role for the supramolecular self-assembly of building blocks. Furthermore, it was established that hemidirected coordination of PbII in the described structures dictates singlecomponent white light-emitting properties. Density functional theory (DFT) and time-dependent (TD) DFT calculations were applied to shed light on the stability of the obtained structures as well as to describe their luminescence properties.

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RESULTS AND DISCUSSION An equimolar one-pot reaction of PbCl2 with a series of closely related organic ligands LI and HLII−VI (Chart 2) in MeOH at 60 °C in a branched tube apparatus leads to heteroleptic complexes [Pb2(LI)Cl4]n, [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, [Pb2(LIV)Cl3]n, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n· nMeOH, respectively (Scheme 1). Notably, the structures of [Pb2(LIV)Cl3]n and [Pb3(LVI)2Cl4]n·nMeOH each comprise the deprotonated form of the corresponding organic ligand, while the other compounds are constructed from the neutral form of the organic unit. All compounds were obtained in good yields and were fully characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, powder and singlecrystal X-ray diffraction, and topological analysis. Their solidstate luminescence was also studied. According to the single-crystal X-ray diffraction data, [Pb2(LI)Cl4]n, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOH crystallize in the monoclinic space group P21/c, while [Pb2(LIV)Cl3]n crystallizes in the monoclinic space group C2/c. Compounds [Pb(HLII)Cl2]n·nMeOH and [Pb(HLIII)Cl2]n· 0.5 nMeOH crystallize in the triclinic space group P1̅. The asymmetric unit of [Pb2(LI)Cl4]n consists of one PbII and two Cl− atoms as well as a half of the ligand LI. Each PbII atom is covalently linked to four μ4-Cl− and two μ2-Cl− atoms, yielding a double-layered 2D sheet (Figure 1 and Table 1). These 2D sheets are bridged by the organic linkers, coordinated through the pyridyl nitrogen atoms to the PbII ions (Table 1), generating a 3D framework (Figure 1). Thus, each PbII atom adopts a holodirected seven-coordinate square face monocapped trigonal prismatic coordination environment (Figure 1). The 3D framework of [Pb2(LI)Cl4]n was simplified, using the ToposPro software,28 resulting in a unique binodal 4,7-connected threeperiodic topology defined by the point symbol of (3·44·5)(32·44· 510·65) (Figure 1). Remarkably, this topology was observed for the first time and named by us as sda1. The difference between the HLII and LI ligands concerns the presence of an amide group in the former compound instead of one of the imine fragments in the latter one (Chart 2). This, however, leads to quite dramatic changes in the structure of the resulting PbII coordination polymer [Pb(HLII)Cl2]n·nMeOH, the asymmetric unit of which contains one PbII, two Cl− atoms, one organic ligand HLII, and one molecule of MeOH. The presence of two 3-pyridyl functions in the structure of HLII also makes this molecule, similar to LI, incapable of chelating to the PbII center, but rather makes HLII acting as a μ3-spacer and thus giving rise to the formation of a 2D structure (Figure 2). The sixcoordinate PbII atom is covalently surrounded by two pyridine

Chart 1. Simplified Diagram of the Holodirected and Hemidirected Coordination Spheres around Lead

enabling the approach of the electron donor. This makes PbIIbased networks particularly sensitive to the choice of ligands and counterions to form supramolecular interactions not only between each other but also with the metal ion itself. In this contribution we describe the synthesis, complete structural investigation, and topologies of six new Pb II coordination polymers [Pb 2 (L I )Cl 4 ] n , [Pb(HL II )Cl 2 ] n · nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, [Pb2(LIV)Cl3]n, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOH, derived from PbCl2 and 1,2-bis(pyridin-3-ylmethylene)hydrazine (LI), N′-(pyridin3-ylmethylene)nicotinohydrazide (HL II ), N′-(pyridin-2ylmethylene)nicotinohydrazide (HLIII), N′-(1-(pyridin-2-yl)ethylidene)picolinohydrazide (HLIV), N′-(1-(pyridin-2-yl)ethylidene)isonicotinohydrazide (HLV), and N′-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HLVI) (Chart 2). Similar bis-pyridyl organic linkers have been of particular importance to construct and design coordination polymers.25−27 The overall topology of the obtained PbII complexes varies from one-dimensional (1D) polymeric chains in [Pb(HLIII)Cl2]n·0.5 nMeOH and [Pb2(LIV)Cl3]n, [Pb(HLV)Cl2]n to twodimensional (2D) metal−organic networks in [Pb(HLII)Cl2]n· nMeOH, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOH, and a Chart 2. Diagrams of the Employed Ligands LI and HLII− HLVI

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Inorganic Chemistry Scheme 1. Syntheses of the PbII Complexes Described in This Worka

a

Tetrel bonds are shown as dashed lines.

nitrogen atoms and one carbonyl oxygen atom from three HLII ligands as well as three chloride ligands, forming a [Pb2(μ2Cl)2Cl2] dimer (Figure 2 and Table 1). The bridging chloride ligands are not placed equidistantly between the two lead atoms with the Pb−Cl bonds being 2.716(4) and 3.066(3) Å, while the binding of the terminal chloride ligand shows a 2.696(3) Å distance. The coordination sphere around the metal center in [Pb(HLII)Cl2]n·nMeOH is a significantly distorted octahedron (Figure 2). Such a distorted coordination environment is indicative of a stereochemically active lone pair that appears to cap one of the N−O edges. This allows the PbII atom to participate in an additional weak Pb−N tetrel bond of 3.391(11) Å involving the imine nitrogen atom of the O-donating HLII molecule (Figure 2). The amide hydrogen atom of the HLII ligand is involved in the hydrogen bonding with the oxygen atom of the lattice MeOH (Table 2). No other classic hydrogen bonds were found. The 2D layered structure of [Pb(HLII)Cl2]n· nMeOH is stabilized by efficient π···π stacking interactions (Table 3), formed between the pyridyl rings of the adjacent organic ligands. Replacing the 3-pyridyl group at the imine fragment with a 2pyridyl one makes the ligand molecule HLIII (Chart 2) capable of chelating to the PbII atom with three donor atoms, yielding a 1D coordination polymer [Pb(HLIII)Cl2]n·0.5 nMeOH (Figure 3). The asymmetric unit of [Pb(HLIII)Cl2]n·0.5 nMeOH consists of one PbII and two Cl− atoms as well as one ligand LI and a half of the MeOH molecule. The metal atom is seven-coordinated by two nitrogen and one oxygen atoms from one organic ligand, one 3-pyridyl nitrogen atom from the other organic ligand, two bridging μ2-Cl− atoms, and one terminal Cl− atom, yielding a holodirected pentagonal bipyramid (Figure 3 and Table 1). The dimeric [Pb2(μ2-Cl)2Cl2] block is also observed in the structure of [Pb(HLIII)Cl2]n·0.5 nMeOH, although its geometry is somewhat different from that observed in [Pb(HLII)Cl2]n·

nMeOH. Particularly, the bridging chloride ligands are almost equidistant from the PbII centers with the Pb−Cl bonds being 2.884(2) and 2.948(2) Å. The binding of the terminal chloride ligand shows a 2.796(2) Å distance. While the ligand HLIII chelates one PbII atom, the 3-pyridyl nitrogen atom of the same ligand binds to a neighboring PbII center (Figure 3). Hence, μ2HLIII acts as a linker between the dimeric [Pb2(μ2-Cl)2Cl2] blocks interconnecting them into 1D chains (Figure 3). The amide hydrogen atoms of the HLIII ligands in the structure of Pb(HLIII)Cl2]n·0.5 nMeOH are involved in hydrogen bonding with the terminal Cl− atoms from the adjacent chains (Table 2), yielding a ladderlike 2D sheet. The hydrogen-bonded 2D sheet is further stabilized by π···π stacking interactions (Table 3), formed between the pyridyl rings of the adjacent 1D chains. The terminal Cl− atom is further involved in the hydrogen bonding with the oxygen atom of the lattice MeOH, which in turn is also Hbonded to the carbonyl oxygen atom of the ligand HLIII (Table 2). The difference between the HLIV and HLIII ligands concerns not only the presence of two 2-pyridyl fragments but also the presence of a methyl group on the imine carbon atom (Chart 2). All this leads to dramatic changes in the structure of the resulting PbII coordination polymer [Pb2(LIV)Cl3]n. The asymmetric unit of this compound consists of one seven- and one six-coordinate PbII atoms, one ligand LIV, as well as a half of the bridging μ4-Cl− ligand, and two and a half of the bridging μ2-Cl− ligands (Table 1). The overall structure of [Pb2(LIV)Cl3]n is constructed from dimeric tetranuclear [Pb4(μ3-LIV-κ6N:N′:N″:μ3-O)2(μ4-Cl)(μ2Cl)2]3+ cationic blocks linked in a zigzag manner through bridging μ2-Cl− ligands, yielding a 1D polymeric chain (Figure 4). The [Pb4(LIV)2Cl3]3+ building block is symmetric with the twofold axis running through the μ4-Cl− ligand and orthogonal to the least-squares plane of the Pb2O2 squarelike fragment (Table 1), formed by the two seven-coordinate PbII atoms and two 9700


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rise to the formation of a 1D zigzaglike polymeric chain [Pb(HLV)Cl2]n (Figure 5). The asymmetric unit of [Pb(HLV)Cl2]n consists of one seven- and one six-coordinate PbII atoms, two ligands HLV, as well as one bridging μ2-Cl− ligand, and three terminal Cl− ligands (Table 1). The seven-coordinate PbII atoms are in the same holodirected coordination environment, N3Cl3O (Figure 5), as it was found for the metal atoms in the structure of [Pb(HLIII)Cl2]n·0.5 nMeOH (Figure 3), while the sixcoordinate PbII ions are in an N3Cl2O coordination environment (Figure 5). Two 1D zigzag chains are linked into a 1D gridlike ribbon through the dimeric [Pb2(μ2-Cl)2Cl2] blocks as bridging nodes, formed by the seven-coordinate PbII atoms (Figure 5). These dimeric blocks are quite similar to those in the structure of [Pb(HLIII)Cl2]n·0.5 nMeOH with the Pb−μ2-Cl distances being 2.814(3) and 2.983(4) Å, while binding of the terminal chloride ligand shows a 2.812(4) Å distance. Interestingly, single-crystal X-ray diffraction studies showed that the six-coordinate PbII atoms, which serve as terminal nodes of the 1D gridlike ribbon, exhibit a hemidirected coordination geometry and are involved in tetrel bonding with one of the terminal chloride atoms from the adjacent ribbons (Figure 5 and Table 1). As a result of these interactions, a double-layered 2D sheet is formed. This sheet is further stabilized by π···π stacking interactions (Table 3), formed between the pyridyl rings of the adjacent ribbons. The ligand HLVI is the bulkiest one among the exploited ligands in this work, and its structure resembles that of HLIII, although containing a phenyl fragment on the imine carbon atom (Chart 2). Despite the presence of bulky phenyl fragment, a 2D layered coordination polymer [Pb3(LVI)2Cl4]n·nMeOH is formed (Figure 6). The asymmetric unit of this compound consists of two five- and one four-coordinate PbII atoms, two organic ligands LVI, as well as two bridging μ2-Cl− ligands, and two terminal Cl− ligands (Figure 6 and Table 1). Every LVI ligand acts, considering only covalent bonds (Table 1), as a μ2-linker, chelating one PbII center with three atoms and coordinating the other PbII center through the 3-pyridyl nitrogen atom. One of the five-coordinate PbII atoms is in a N2Cl2O coordination environment formed by the chelate fragment of LVI and two μ2-Cl− ligands, while the other five-coordinate PbII atom is in an N2Cl3 coordination environment formed by two nitrogen atoms from two 3-pyridyl fragments of two LVI as well as two μ2-Cl− ligands and one terminal Cl− ligand. The four-coordinate PbII atom is in an N2ClO coordination environment thanks to the chelating fragment of LVI and one terminal Cl− ligand. Notably, each PbII atom exhibits a hemidirected coordination geometry (Figure 6) and is involved in tetrel bonding with one of the terminal chloride atoms from the adjacent ribbons (Figure 6 and Table 1). Particularly, the N2Cl2O-coordinated PbII atom forms a tetrel bond with the amide nitrogen atom from the adjacent ligand LVI, while the N2Cl3-coordinated PbII ion is involved in tetrel bonding with the adjacent terminal Cl− ligand, arising from the covalent coordination sphere of the four-coordinate metal atom (Figure 6 and Table 1). The latter metal center, in turn, forms three tetrel bonds: one bond with the amide nitrogen atom from the adjacent ligand LVI and two bonds with the bridging μ2Cl− ligands (Figure 6 and Table 1). The 2D layered structure of [Pb3(LVI)2Cl4]n·nMeOH is stabilized by π···π stacking interactions (Table 3), formed between the pyridyl rings of the adjacent organic ligands. Furtermore, one of the terminal Cl− ligands is involved in intermolecular hydrogen bonding with the OH hydrogen atom of the lattice MeOH molecule (Table 2). A simplified underlying network of [Pb3(LVI)2Cl4]n·nMeOH, considering all tetrel bonds, reveals a unique heptanodal

Figure 1. (top) Crystal structure of [Pb2(LI)Cl4]n (hydrogen atoms are omitted for clarity; color code: C = gold, N = blue, Cl = green, Pb = magenta). (middle) A simplified underlying network of [Pb2(LI)Cl4]n with the unique binodal 4,7-connected three-periodic topology sda1 defined by the point symbol of (3·44·5)(32·44·510·65) and constructed from layers with the binodal 4,6-connected layer topology 4.6L66 defined by the point symbol of (3·44·6)(32·44·56·63) (color code: Cl = green, Pb = magenta). (bottom) The holodirected coordination polyhedron, constructed from the covalent bonds, around the PbII atom in the structure of [Pb2(LI)Cl4]n.

amide oxygen atoms. The seven-coordinate PbII atom is in a hemidirected N2Cl3O2 coordination environment, formed by the two nitrogen and one oxygen atoms from the chelate fragment of one organic ligand LIV, one bridging oxygen atom from the other ligand LIV, one μ4-Cl− ligand, and two μ2-Cl− ligands (Figure 4). The six-coordinate PbII atom is in a hemidirected NCl4O coordination environment, formed by the nitrogen and oxygen atoms of the 2-PyC(O) fragment of the organic ligand, one μ4Cl− ligand, and three μ2-Cl− ligands (Figure 4). Hence, every μ3LIV-κ6N:N′:N″:μ3-O ligand acts as a linker between three PbII atoms, with the 2-PyC(CH3)N fragment being coordinated to one PbII atom, the remaining 2-pyridyl nitrogen atom being coordinated to the other PbII center, and the carbonyl oxygen atom being linked to three metal sites (Figure 4 and Table 1). Topological analysis of the 1D polymeric metal−organic chain in [Pb2(LIV)Cl3]n discloses a unique pentanodal 3,4,4,5,6-connected chain topology defined by the point symbol of (3·42)2(32· 42·52)(32·43·5)(33·43·53·6)2(33·45·55·62)2 (Figure 4). Remarkably, this topology was also observed for the first time and named by us as sda2. The ligand HLV, in comparison with HLIV, contains a 4-pyridyl group on the carbonyl side of the molecule. This makes the molecule of HLV incapable of chelating to more than one PbII atom, but rather makes HLV acting as a μ2-spacer and thus giving 9701


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Inorganic Chemistry Table 1. Covalent and Tetrel Bond Lengths (Å) in the Structures of PbII Complexes Described in this Work bond

bond donor

bond length

bond type

[Pb2(LI)Cl4]n

complex

Pb−N Pb−Cl

[Pb(HLII)Cl2]n·nMeOH

Pb−N

L Cl− Cl− Cl− Cl− Cl− Cl− L L L L Cl− Cl− Cl− L L L L Cl− Cl− Cl− L L L L

2.563(12) 2.766(4) 2.859(4) 2.903(4) 2.980(4) 3.203(4) 3.245(4) 2.545(10) 2.780(11) 3.391(11) 2.770(9) 2.696(3) 2.716(4) 3.066(3) 2.709(5) 2.712(6) 2.813(7) 2.682(5) 2.796(2) 2.884(2) 2.948(2) 2.468(3) 2.513(3) 2.534(3) 2.415(2) 2.832(3) 2.839(3) 2.7839(10) 2.8262(11) 2.8366(2) 2.9231(2) 3.0279(10) 3.0445(9) 3.2221(9) 2.587(8) 2.626(8) 2.723(9) 2.743(9) 2.784(10) 2.872(10) 2.824(7) 2.849(8) 2.642(3) 2.779(3) 2.812(4) 2.814(3) 2.983(4) 3.382(4) 2.458(15) 2.474(16) 2.557(15) 2.624(17) 2.660(16) 2.684(17) 2.989(15) 3.093(15) 2.384(13) 2.403(13) 2.593(6) 2.645(6) 2.723(6)

covalent covalent covalent covalent covalent covalent covalent covalent covalent tetrel covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent covalent tetrel covalent covalent covalent covalent covalent covalent tetrel tetrel covalent covalent covalent covalent covalent

Pb−O

[Pb(HLIII)Cl2]n·0.5 nMeOH

Pb−N

Pb−O Pb−Cl

[Pb2(LIV)Cl3]n

Pb−N

Pb−O

Cl− Cl− Cl− Cl− Cl− Cl− Cl− L L L L L L

Pb−Cl

[Pb(HLV)Cl2]n

Pb−N

Pb−O Cl− Cl− Cl− Cl− Cl− Cl− L L L L L L L L L L Cl− Cl− Cl−

Pb−Cl

[Pb3(LVI)2Cl4]n·nMeOH

Pb−N

Pb−O Pb−Cl

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Inorganic Chemistry Table 1. continued complex

bond

bond donor

bond length

Cl− Cl− Cl− Cl− Cl− Cl−

bond type

2.763(5) 3.195(5) 3.196(5) 3.440(5) 3.467(6) 3.490(6)

covalent covalent covalent tetrel tetrel tetrel

Complex [Pb2(LI)Cl4]n exhibits a broad emission band centered at 458 nm (Figure 8), which can be assigned to the intraligand π*→π and π*→n transitions of the parent ligand LI. This can be explained that PbII in the structure of [Pb2(LI)Cl4]n exclusively adopts a holodirected coordination geometry (Figure 1) and, hence, has no stereochemically active lone-pair effect.17−22 Therefore, no obvious influence of PbII is involved in the ligand photoluminescence. In contrast, the main emission peak of complexes [Pb2(LIV)Cl3]n and [Pb(HLV)Cl2]n is redshifted to 471 and 490 nm, respectively (Figure 8), which can be assigned to a ligand-to-metal charge transfer (LMCT) excited state. Interestingly, the main emission band in the spectra of [Pb2(LIV)Cl3]n and [Pb(HLV)Cl2]n is accompanied by a tail spreading well into the red region (Figure 8), suggesting metalcentered (MC) transitions involving the s and p orbitals of PbII.17−22 The colors of the emissions can be quantified with the CIE chromaticity diagram, which serves to specify how the human eye perceives light with a given spectrum. While the chromaticity coordinates for [Pb2(LI)Cl4]n and [Pb(HLV)Cl2]n are (0.16, 0.14) and (0.24, 0.36), respectively, which is located in the blue and bluish-green regions, respectively, the coordinates for the emission of [Pb2(LIV)Cl3]n are (0.23, 0.25), falling within the white gamut of the chromaticity diagram (Figure 8) due to the LMCT red shift of the main luminescence peak and the appearance of MC emission. To shed additional light on noncovalent interactions, which control the topology of the obtained polymers, the charge and energy decomposition scheme (ETS-NOCV) based29 study is performed at the DFT/BLYP-D3/TZP level including the scalar relativistic effects (ZORA) as implemented in the Amsterdam Density Functional (ADF) package.30,31 We applied the DFT/ BLYP-D3/TZP level of theory because it has been proven that it provides satisfactory results for the description of noncovalent interactions.32 We will first discuss in detail the results for [Pb(HLII)Cl2]n· nMeOH (Figure 9), based on the cluster approach, followed by a brief summary for the remaining systems. The ETS-NOCV results demonstrate that the Pb−N connections are largely ionic with ΔEelstat comprising ∼58% of the overall stabilization ΔEelstat + ΔEorb + ΔEdispersion, followed by the charge delocalization term

Figure 2. (top) Crystal structure of [Pb(HLII)Cl2]n·nMeOH (CH hydrogen atoms and methanol molecules are omitted for clarity; color code: C = gold, N = blue, Cl = green, O = red, Pb = magenta). Tetrel bonds Pb···N are shown as dashed lines. (bottom) The hemidirected coordination polyhedron, constructed from the covalent bonds, around the PbII atom in the structure of [Pb(HLII)Cl2]n·nMeOH.

3,3,3,3,4,5,5-connected layer topology defined by the point symbol of (3·4·5)(3·42·6·72·82·92)(3·43·5·62·72·8)(42·6)2(43·62· 7)(43) (Figure 6). This topology was also observed for the first time and named by us as sda3. Bulk samples of the described complexes were each studied by means of X-ray powder diffraction analysis (Figure 7). The experimental X-ray powder patterns of the complexes are in full agreement with the calculated powder patterns obtained from single-crystal X-ray diffraction, showing that the bulk materials are free from phase impurities. The photoluminescence properties of the obtained complexes were investigated in the solid state under ambient conditions. It was found that [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, and [Pb3(LVI)2Cl4]n·nMeOH are unstable under experimental conditions, which is most probably due to the volatile lattice molecules of methanol.

Table 2. Classic Hydrogen Bond Lengths (Å) and Angles (deg) for [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5nMeOH and [Pb3(LVI)2Cl4]n·nMeOH compound

D−H···A

d(D−H)

d(H···A)

d(D···A)

∠(DHA)

[Pb(HL )Cl2]n·nMeOH [Pb(HLIII)Cl2]n·0.5 nMeOHa

N(2)−H(2N)···O(2) N(3)−H(3N)···Cl(1)a No. 1 O(2)−H(2O)···Cl(1)a No. 2 O(2)−H(2O)···O(1)a No. 2 O(41)−H(41)···Cl(4)a No. 2

0.88 0.91(7) 0.90(14) 0.90(14) 0.82

2.01 2.36(6) 2.71(15) 2.50(14) 2.32

2.862(15) 3.219(7) 3.284(18) 3.166(19) 3.13(2)

163 159(6) 123(10) 131(12) 169

II

[Pb3(LVI)2Cl4]n·nMeOH a

Symmetry transformations used to generate equivalent atoms: No. 1: 1 + x, y, z; No. 2: −1 − x, 1 − y, 2 − z. 9703


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Table 3. π···π Distances (Å) and Angles (deg) for [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, [Pb(HLV)Cl2]n, and [Pb3(LVI)2Cl4]n·nMeOHa [Pb(HL )Cl2]n·nMeOH II

b

[Pb(HLIII)Cl2]n·0.5 nMeOHc

[Pb(HLV)Cl2]nd

[Pb3(LVI)2Cl4]n·nMeOHe

Cg(I)

Cg(J)b,c,d,e

d[Cg(I)−Cg(J)]

α

β

γ

slippage

Cg(2) Cg(3) Cg(3) Cg(1) Cg(2) Cg(2) Cg(3) Cg(3) Cg(4) Cg(4) Cg(5) Cg(5) Cg(6) Cg(6) Cg(5) Cg(5) Cg(5) Cg(6) Cg(6) Cg(7) Cg(7) Cg(8) Cg(10) Cg(10)

Cg(3)No. 1 Cg(2)No. 1 Cg(3)No. 2 Cg(2)No. 1 Cg(1)No. 2 Cg(2)No. 3 Cg(6)No. 1 Cg(6)No. 2 Cg(5)No. 1 Cg(5)No. 3 Cg(4)No. 4 Cg(4)No. 3 Cg(3)No. 4 Cg(3)No. 2 Cg(7)No. 1 Cg(8)No. 2 Cg(10)No. 3 Cg(7)No. 4 Cg(10)No. 5 Cg(5)No. 6 Cg(6)No. 2 Cg(5)No. 4 Cg(5)No. 3 Cg(6)No. 7

3.748(7) 3.748(7) 3.512(7) 3.790(4) 3.791(4) 3.734(4) 3.559(6) 3.772(6) 3.586(6) 3.625(6) 3.586(6) 3.625(6) 3.559(6) 3.772(6) 3.727(12) 3.748(11) 3.727(12) 3.644(11) 3.644(11) 3.728(12) 3.643(11) 3.749(11) 3.728(12) 3.643(11)

5.4(6) 5.4(6) 0.0(6) 6.8(4) 6.8(4) 0.0(3) 3.0(5) 2.3(5) 3.2(5) 4.2(5) 3.2(5) 4.2(5) 3.0(5) 2.3(5) 7 16 7 14 14 7 14 16 7 14

21.6 23.8 11.9 19.4 25.0 25.0 20.5 23.8 20.7 14.1 19.3 17.5 20.3 22.6 26.2 16.7 26.1 23.7 23.7 27.7 11.0 28.2 27.7 11.0

23.8 21.6 11.9 25.0 19.4 25.0 20.3 22.6 19.3 17.5 20.7 14.1 20.5 23.8 27.7 28.2 27.7 11.0 11.0 26.2 23.7 16.7 26.1 23.7

1.379 1.510 0.722 1.260 1.600 1.579 1.245 1.523 1.265 0.885 1.187 1.090 1.236 1.449 1.643 1.077 1.642 1.466 1.467 1.732 0.694 1.772 1.731 0.694

Cg(I)−Cg(J): distance between ring centroids; α: dihedral angle between planes Cg(I) and Cg(J); β: angle Cg(I)→Cg(J) vector and normal to plane I; γ: angle Cg(I)→Cg(J) vector and normal to plane J; slippage: distance between Cg(I) and perpendicular projection of Cg(J) on ring I. b Symmetry transformations used to generate equivalent atoms: No. 1 −x, 1 − y, − z; No. 2 −x, 2 − y, − z. Cg(2): N(1)−C(13)−C(12)−C(11)− C(10)−C(14), Cg(3): N(4)−C(23)−C(22)−C(21)−C(20)−C(24). cSymmetry transformations used to generate equivalent atoms: No. 1 x, 1 + y, z; No. 2 x, − 1 + y, z; No. 3 −1 − x, − y, 1 − z. Cg(1): N(1)−C(1)−C(2)−C(3)−C(4)−C(5), Cg(2): N(4)−C(9)−C(8)−C(12)−C(11)−C(10). d Symmetry transformations used to generate equivalent atoms: No. 1 −x, 1/2 + y, 1/2 − z; No. 2 −x, 2 − y, 1 − z; No. 3 −x, 1 − y, 1 − z; No. 4 −x, − 1/2 + y, 1/2 − z. Cg(3): N(1)−C(1)−C(2)−C(3)−C(4)−C(5), Cg(4): N(4)−C(11)−C(10)−C(9)−C(13)−C(12), Cg(5): N(5)−C(14)− C(15)−C(16)−C(17)−C(18), Cg(6): N(8)−C(24)−C(23)−C(22)−C(26)−C(25). eSymmetry transformations used to generate equivalent atoms: No. 1 x, 1/2 − y, − 1/2 + z; No. 2 x, −1 + y, z; No. 3 x, y, z; No. 4 x, 1 + y, z; No. 5 x, 3/2 − y, 1/2 + z; No. 6 x, 1/2 − y, 1/2 + z; No. 7 x, 3/ 2 − y, −1/2 − z. Cg(5): N(1)−C(1)−C(2)−C(3)−C(4)−C(5), Cg(6): N(4)−C(8)−C(9)−C(10)−C(11)−C(12), Cg(7): N(11)−C(25)− C(24)d−C(23)d−C(22)d−C(21)d, Cg(8): N(14)−C(28)−C(29)−C(30)−C(31)−C(32), Cg(10): C(21)−C(22)−C(23)−C(24)−C(25)c− N(11)c. a

the lone pair of nitrogen to the PbII atom (hybridized 4sp orbital) as well as back-donation from the metal to the binding regions of Pb−N (covalency; Figure 9, bottom). Accordingly, they are classified as typical dative-covalent connections. Furthermore, the Pb−N bonds in [Pb(HLII)Cl2]n·nMeOH are clearly not equivalent as indicated by the formation of two separated σ-type channels Δρorbσ1, Δρorbσ2 with the corresponding orbital interaction energies ΔEorbσ1 = −20.46 kcal/mol and ΔEorbσ2 = −12.59 kcal/mol, respectively (Figure 9, bottom A). Similar relation is valid when considering the other model with the additional HLII plane (Figure 9, bottom B). It is fully consistent with the Pb−N distances being 2.5 and 2.8 Å, respectively. The πcontribution of the Pb−N bond is far weaker and exhibits ΔEorbπ1+π2 = −2.64 kcal/mol (Figure S1 in the Supporting Information). Interestingly, the model B reveals a significant dispersion stabilization in the Pb−N bonding, ΔEdispersion = −26.27 kcal/mol (Figure 9). Finally, the π···π stacking interaction is quite efficient with the overall interaction energy ΔEint = −13.76 kcal/mol (Figure 9,C). It is characterized by typical constituents, namely, the leading dispersion term ΔEdispersion = −21.17 kcal/mol, followed by elestrostatic ΔEelstat = −6.31 kcal/mol and charge delocalization ΔEorb = −3.54 kcal/ mol terms (Figure 9). As far as the latter component is concerned

Figure 3. (top) Crystal structure of [Pb(HLIII)Cl2]n·0.5 nMeOH (CH hydrogen atoms and methanol molecules are omitted for clarity; color code: C = gold, N = blue, Cl = green, O = red, Pb = magenta). (bottom) The holodirected coordination polyhedron, constructed from the covalent bonds, around the PbII atom in the structure of [Pb(HLIII)Cl2]n·0.5 nMeOH.

ΔEorb (∼32%) and dispersion contribution ΔEdispersion (∼10%; Figure 9, top A,B). An inspection of the NOCV-based deformation density contributions clearly shows that formation of the Pb−N bonding is associated with charge donation from 9704


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Inorganic Chemistry

Figure 4. (top) Crystal structure of [Pb2(LIV)Cl3]n (hydrogen atoms are omitted for clarity; color code: C = gold, N = blue, Cl = green, O = red, Pb = magenta). (middle) A simplified underlying network of [Pb2(LIV)Cl3]n with the unique pentanodal 3,4,4,5,6-connected chain topology sda2 defined by the point symbol of (3·42)2(32·42·52)(32·43· 5)(33·43·53·6)2(33·45·55·62)2 (color code: LIV = blue, Cl = green, Pb = magenta). (bottom) The hemidirected coordination polyhedra, constructed from the covalent bonds, around two crystallographically independent PbII atoms in the structure of [Pb2(LIV)Cl3]n.

Figure 6. (top) Crystal structure of [Pb3(LVI)2Cl4]n·nMeOH (hydrogen atoms are omitted for clarity; color code: C = gold, N = blue, Cl = green, O = red, Pb = magenta). Tetrel bonds Pb···Cl and Pb···N are shown as dashed lines. (middle) A simplified underlying network of [Pb3(LVI)2Cl4]n·nMeOH, considering all tetrel bonds, with the unique heptanodal 3,3,3,3,4,5,5-connected layer topology sda3 defined by the point symbol of (3·4·5)(3·42·6·72·82·92)(3·43·5·62·72·8)(42·6)2(43·62· 7)(43) (color code: LVI = blue, Cl = green, Pb = magenta). (bottom) The hemidirected coordination polyhedra, constructed from the covalent bonds, around three crystallographically independent PbII atoms in the structure of [Pb3(LVI)2Cl4]n·nMeOH. Figure 5. (top) Crystal structure of [Pb(HLV)Cl2]n (CH hydrogen atoms are omitted for clarity; color code: C = gold, N = blue, Cl = green, O = red, Pb = magenta). Tetrel bonds Pb···Cl are shown as dashed lines. (bottom) The holo- (left) and hemidirected (right) coordination polyhedra, constructed from the covalent bonds, around two crystallographically independent PbII atoms in the structure of [Pb(HLV)Cl2]n.

ΔEorbπ = −16.61 kcal/mol for [Pb3(LVI)2Cl4]n·nMeOH (Figure S6 in the Supporting Information) or even ΔEorbπ = −48.04 kcal/ mol for [Pb 2 (L IV )Cl 3 ] (Figure S4 in the Supporting Information). As far as interaction of the solvent with a coordination polymer is concerned, the ETS-NOCV analysis indicates that the methanol species in the cluster model of [Pb3(LVI)2Cl4]n· nMeOH is bound quite strongly. Particularly, MeOH interacts with both the chlorine and PbII atoms with the overall interaction energy ΔEint = −11.87 kcal/mol, mostly due to the charge transfer contribution ΔEorb = −9.94 kcal/mol, which even outweighs the dispersion ΔEdispersion = −7.79 kcal/mol and electrostatic ΔEelstat = −5.34 kcal/mol terms (Figure S7 in the Supporting Information). However, note that at the present stage we can not pinpoint an exact mechanistic role of solvent species in the formation of [Pb(HLII)Cl2]n·nMeOH, [Pb(HLIII)Cl2]n·0.5 nMeOH, and [Pb3(LVI)2Cl4]n·nMeOH or their deterioration under luminescence conditions. Further indepth studies aiming toward determination and understanding both the luminescence properties as well as thermal stability of the obtained polymers are in progress.

one can notice that it covers not only the intraplane charge polarizations but also the interplane charge transfers, Δρorb1+3 (Figure 9). We performed similar calculations for the remaining systems (Figures S2−S6 in the Supporting Information). It was found that the overall strength of the Pb−N bond varies from ΔEint = −18.94 kcal/mol for [Pb(HLIII)Cl2]n·0.5 nMeOH through ΔEint = −20.48 kcal/mol for [Pb(HLV)Cl2]n to ΔEint = −24.16 kcal/mol for [Pb2(LI)Cl4]n (Figures S1−S6 in the Supporting Information). The Pb−O/Cl bonds are also dative-covalent, and they exhibit similar characteristics to the previously discussed Pb−N connections (Figures S1−S6 in the Supporting Information). Despite the fact that the σ-components are consistently more dominant over the π-contributions, the latter ones can be very strong, for example, reaching the stabilization 9705


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Inorganic Chemistry

Figure 7. Calculated (black) and experimental (red) X-ray powder diffraction patterns of the PbII complexes described in this work.

Finally, to shed some light on the electronic structure, which determines the luminescence properties of the obtained white light-emitting polymer [Pb2(LIV)Cl3], we performed both the molecular TD-DFT simulations as implemented in the ADF program as well as the periodic calculations by means of the BAND package (ZORA/TZP/BLYP and PBE).30,31 It can be concluded that the main absorption transitions are predominantly due to charge transfer from the chlorine lone pairs to the π* orbitals of LIV (Figure 10). Consistently, we determined, on the basis of the partial and overall density of states from the periodic calculations, that the valence band nearby the Fermi level is dominated by the 2p lone pairs of chlorine atoms (Figures S8 and S9 in the Supporting Information). It is important to add that the lowest-lying conduction bands are, to a significant degree, due to the Pb contributions, which supports the suggestion of an important role of the metal in the luminescence properties of [Pb2(LIV)Cl3] (Figures S8 and S9 in the Supporting Information).

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Figure 8. (top) Room-temperature emission spectra of [Pb2(LI)Cl4]n (λex = 340 nm), [Pb2(LIV)Cl3]n (λex = 370 nm), and [Pb(HLV)Cl2]n (λex = 375 nm) in the solid state. (bottom) CIE-1931 chromaticity diagram and the calculated CIE coordinates, located at (0.16, 0.14) for [Pb2(LI)Cl4]n (marked by the black circle), (0.23, 0.25) for [Pb2(LIV)Cl3]n (marked by the red circle), and (0.24, 0.36) for [Pb(HLV)Cl2]n (marked by the blue circle). 0.120, and 0.151 g, rerspectively; 0.5 mmol) were placed in the main arm of a branched tube. MeOH (15 mL) was carefully added to fill the arms. The tube was sealed and immersed in an oil bath at 60 °C, while the branched arm was kept at ambient temperature. X-ray-suitable crystals were formed during the next days in the cooler arm and were filtered off, washed with acetone and diethyl ether, and dried in air. [Pb2(LI)Cl4]n. Yellow platelike crystals. Yield: 0.155 g (81%). mp 190 °C. FTIR, ν: 1628 (C = N), 2930 (CH) cm−1. Anal. Calcd for C12H10Cl4N4Pb2 (766.45) (%): C 18.81, H 1.32 and N 7.31; found: C 18.70, H 1.23, and N 7.25. [Pb(HLII)Cl2]n·nMeOH. Yellow prismlike crystals. Yield: 0.228 g (85%). mp 201 °C. FTIR, ν: 1663 (C = O), 3032 (CH), 3202 (NH), 3490 (OH) cm−1. Anal. Calcd for C13H14Cl2N4O2Pb (536.39) (%): C 29.11, H 2.63, and N 10.45; found C 28.91, H 2.71, and N 11.00. [Pb(HLIII)Cl2]n·0.5 nMeOH. Yellow blocklike crystals. Yield: 0.174 g (67%). mp 255 °C. FTIR, ν: 1669 (C = O), 2983 (CH), 3145 (NH), 3501 (OH) cm−1. Anal. Calcd for C12.5H12Cl2N4O1.5Pb (520.37) (%): C 28.85, H 2.32, and N 10.77; found C 29.01, H 2.50, and N 11.57. [Pb2(LIV)Cl3]n. Yellow blocklike crystals. Yield: 0.124 g (65%). mp 294 °C. FTIR, ν: 1701 (C = O), 3054 (CH) cm−1. Anal. Calcd for

EXPERIMENTAL SECTION

Materials. All ligands were prepared following the reported method as described elsewhere.33 All other reagents and solvents were commercially available and used as without further purification. Physical Measurements. FTIR spectra were recorded on a Bruker Tensor 27 FTIR spectrometer. The solid-state emission spectra were obtained with a Fluorolog-3 (Jobin-Yvon-Spex Company) spectrometer. Microanalyses were performed using a Heraeus CHN-O-Rapid analyzer. Melting points were measured on an Electrothermal 9100 apparatus. Synthesis of Complexes. PbCl2 (0.139 g, 0.5 mmol) and the corresponding ligand LI or HLII−HLVI (0.105, 0.113, 0.113, 0.120, 9706


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Figure 9. (top) Cluster models of [Pb(HLII)Cl2]n·nMeOH with the fragmentation patterns A, B, and C applied in the ETS-NOCV analysis. (bottom) The most important NOCV-based deformation density channels Δρorbi with the corresponding orbital interaction energies ΔEorbi.

Figure 10. TD-DFT results describing the main absorption bands of the [Pb2(LIV)Cl3] cluster with the corresponding contours of molecular orbitals. 109.809(6), γ = 90.393(6)°, V = 817.09(9) Å3, Z = 2, ρ = 2.164 g cm−3, μ(Mo Kα) = 10.662 mm−1, reflections: 6366 collected, 3762 unique, Rint = 0.064, R1(all) = 0.0902, wR2(all) = 0.1579. Crystal Data for [Pb(HLIII)Cl2]n·0.5 nMeOH. C12H10Cl2N4OPb, 0.5(CH4O); Mr = 520.33 g mol−1, T = 293(2) K, triclinic, space group P1̅, a = 8.5656(5), b = 10.6025(12), c = 10.6335(12) Å, α = 95.295(2), β = 103.359(2), γ = 99.606(2)°, V = 788.95(15) Å3, Z = 2, ρ = 2.191 g cm−3, μ(Mo Kα) = 11.030 mm−1, reflections: 12 624 collected, 4718 unique, Rint = 0.068, R1(all) = 0.0592, wR2(all) = 0.1077. Crystal Data for [Pb2(LIV)Cl3]n. C13H11Cl3N4OPb2, Mr = 759.99 g mol−1, T = 110(2) K, monoclinic, space group C2/c, a = 24.8751(9), b = 9.7305(3), c = 15.5416(5) Å, β = 113.718(2)°, V = 3444.1(2) Å3, Z = 8, ρ = 2.931 g cm−3, μ(Mo Kα) = 20.000 mm−1, reflections: 24 128 collected, 6242 unique, Rint = 0.032, R1(all) = 0.0338, wR2(all) = 0.0520. Crystal Data for [Pb(HLV)Cl2]n. C13H12Cl2N4OPb, Mr = 518.36 g mol−1, T = 293(2) K, monoclinic, space group P21/c, a = 14.5358(5), b = 15.6284(3), c = 13.7627(5) Å, β = 105.206(3)°, V = 3017.03(17) Å3, Z = 8, ρ = 2.282 g cm−3, μ(Mo Kα) = 11.541 mm−1, reflections: 13 688 collected, 5513 unique, Rint = 0.070, R1(all) = 0.0715, wR2(all) = 0.1305. Crystal Data for [Pb3(LVI)2Cl4]n·nMeOH. C36H26Cl4N8O2Pb3, CH4O; Mr = 1398.06 g mol−1, T = 293(2) K, monoclinic, space group P21/c, a = 21.544(5), b = 9.544(2), c = 19.074(4) Å, β = 100.415(4)°, V = 3857.3(15) Å3, Z = 4, ρ = 2.408 g cm−3, μ(Mo Kα) = 13.388 mm−1, reflections: 20 013 collected, 6814 unique, Rint = 0.123, R1(all) = 0.1466, wR2(all) = 0.1664. Additional crystallographic information is available in the Supporting Information.

C13H11Cl3N4OPb2 (760.02) (%): C 20.54, H 1.46, and N 7.37; found: C 20.15, H 1.51, and N 7.57. [Pb(HLV)Cl2]n. Green parallelepiped-like crystals. Yield: 0.233 g (90%). mp 287 °C. FTIR, ν: 1661 (C = O), 3057 (CH), 3451 (NH) cm−1. Anal. Calcd for C13H12Cl2N4OPb (518.37) (%): C 30.12, H 2.33, and N 10.81; found: C 30.24, H 2.17, and N 10.97. [Pb3(LVI)2Cl4]n·nMeOH. Yellow needlelike crystals. Yield: 0.168 g (72%). mp 239 °C. FTIR, ν: 1642 (C = O), 3171 (CH), 3470 (OH) cm−1. Anal. Calcd for C37H30Cl4N8O3Pb3, (1398.11) (%): C 31.79, H 2.16, and N 8.01; found: C 31.99, H 2.02, and N 8.17. X-ray Powder Diffraction. X-ray powder diffraction for bulk samples was performed using a Rigaku Ultima IV X-ray powder diffractometer. The Parallel Beam mode was used to collect the data (λ = 1.541 84 Å). Single-Crystal X-ray Diffraction. The X-ray data were collected on a Bruker four-circle single-crystal diffractometers with a sealed graphitemonochromatised Mo Kα (λ = 0.710 73 Å) radiation tube and an APEXII CCD detector. The frames were integrated with the Bruker SAINT software package,34 and the data were corrected for absorption using the program SADABS.35 The structures were solved by direct methods using the program SHELXS97.36 Non-hydrogen atoms were refined with the full-matrix least-squares procedure on |F2| by SHELXL97.36 Hydrogen atoms were inserted at calculated positions and constrained with isotropic thermal parameters. Figures were generated using the program Mercury.37 Crystal Data for [Pb2(LI)Cl4]n. C12H10Cl4N4Pb2, Mr = 766.42 g mol−1, T = 173(2) K, monoclinic, space group P21/c, a = 17.527(4), b = 7.2591(15), c = 7.4711(15) Å, β = 93.66(3)°, V = 948.6(4) Å3, Z = 2, ρ = 2.683 g cm−3, μ(Mo Kα) = 18.287 mm−1, reflections: 4907 collected, 1705 unique, Rint = 0.070, R1(all) = 0.0710, wR2(all) = 0.1212. Crystal Data for [Pb(HLII)Cl2]n·nMeOH. C12H10Cl2N4OPb, CH4O; Mr = 536.37 g mol−1, T = 173(2) K, triclinic, space group P1̅, a = 8.5656(5), b = 9.1844(5), c = 11.0989(8) Å, α = 95.431(5), β =

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CONCLUSIONS In summary, we have designed and fully structurally characterized six new coordination polymers, namely, [Pb2(LI)Cl4]n, [Pb(HL II )Cl 2 ] n ·nMeOH, [Pb(HL III )Cl 2 ] n ·0.5 nMeOH, [Pb 2 (L IV )Cl 3 ] n , [Pb(HL V )Cl 2 ] n , and [Pb 3 (L VI ) 2 Cl 4 ] n · nMeOH, fabricated from PbCl2 and a series of closely related 9707


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Inorganic Chemistry bis-pyridyl ligands LI and HLII−HLVI. On the basis of the structural analysis, we conclude that the topology of the obtained networks is dictated by the geometry of the organic ligand. The structure of [Pb2(LI)Cl4]n is constructed from the [PbCl2]n 2D sheets, linked through organic linkers into a 3D framework, which exhibits a unique binodal 4,7-connected three-periodic topology named by us as sda1. The coordination sphere around the metal center in the 2D coordination polymer [Pb(HLII)Cl2]n·nMeOH is hemidirected, which allows the PbII atom to participate in an additional weak Pb−N tetrel bond. A 1D coordination polymer [Pb(HLIII)Cl2]n·0.5 nMeOH is considered as a uninodal 2-connected chain. The overall structure of [Pb2(LIV)Cl3]n is constructed from dimeric tetranuclear [Pb 4 (μ 3 -L IV -κ 6 N:N′:N″:μ 3 -O) 2 (μ 4 -Cl)(μ 2 -Cl) 2 ] 3+ cationic blocks linked in a zigzag manner through bridging μ2-Cl− ligands, yielding a 1D polymeric chain. Topological analysis of this chain reveals a unique pentanodal 3,4,4,5,6-connected chain topology named by us as sda2. The structure of [Pb(HLV)Cl2]n exhibits a 1D zigzaglike polymeric chain. Two chains are further linked into a 1D gridlike ribbon through the dimeric [Pb2(μ2Cl)2Cl2] blocks as bridging nodes. Single-crystal X-ray diffraction studies showed that the PbII-based terminal nodes of the 1D gridlike ribbon exhibit a hemidirected coordination geometry and are involved in tetrel bonding with one of the terminal chloride atoms from the adjacent ribbons. As a result of these interactions, a double-layered 2D sheet is formed. With the bulkiest, among the exploited in this work, ligand HLVI a 2D layered coordination polymer [Pb3(LVI)2Cl4]n·nMeOH is formed, which network, considering all tetrel bonds, reveals a unique heptanodal 3,3,3,3,4,5,5-connected layer topology named by us as sda3. Thus, tetrel bonding can play a key role for the supramolecular aggregation of building units in solid state and can legally be considered as one of the most powerful tool to design metal−organic frameworks with different dimensionalities and topologies, as evidenced from the topologies reported in this work. ETS-NOCV charge and energy decomposition calculations allowed to conclude that tetrel bonding as well as the related Pb−O/Cl interactions are largely ionic and of typical dative-covalent character. The luminescence properties of [Pb2(LI)Cl4]n, [Pb2(LIV)Cl3]n, and [Pb(HLV)Cl2]n in the solid state at ambient temperature were also studied. All three compounds were found to be emissive in the solid state. While blue emission of [Pb2(LI)Cl4]n is due to the ligand-centered transitions, bluishgreen and white luminescence of [Pb2(LIV)Cl3]n and [Pb(HLV)Cl2]n, respectively, was assigned to LMCT mixed with MC excited states. The latter compound, affording singlecomponent white-light photoluminescence, seems to be an attractive luminescent material for solid-state white-lightemitting device applications. Molecular as well as periodic calculations have shown an important role of the Pb center as well as the chlorine lone pairs and antibonding π* orbitals of LIV in the electronic transitions of [Pb2(LIV)Cl3]n.

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corresponding orbital interaction energies ΔEorbi, the overall density of states (ZORA/TZP/PBE-D3 and ZORA/TZP/BLYP-D3) of [Pb2(LIV)Cl3] with the corresponding partial density of states stemming from various atoms (PDF) Accession Codes

CCDC 1497457−1497462 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. (G.M.) *E-mail: [email protected]. (M.P.M.) *E-mail: damir.a.safi[email protected]. (D.A.S.) ORCID

Rosa Carballo: 0000-0002-9094-8238 Alessia Bacchi: 0000-0001-5675-9372 Mariusz P. Mitoraj: 0000-0001-5359-9107 Filip Sagan: 0000-0001-5375-8868 Damir A. Safin: 0000-0002-9080-7072 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful to the Univ. of Maragheh for the financial support of this research. This work was supported by the Ministry of Education and Science of the Russian Federation (Agreement number 02.a03.21.0008). DFT calculations were partially performed using the PL-Grid Infrastructure and resources provided by the ACC Cyfronet AGH (Cracow, Poland). F.S. acknowledges the financial support from Krakowskie Konsorcjum “Materia-Energia-Przyszłośc”́ within the KNOW subsidy as well as from the Polish Ministry of Science and Education “Tsubsidy” for young researchers.

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REFERENCES

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b01189. Cluster models with the fragmentation patterns applied in the ETS-NOCV analysis and the most important NOCVbased deformation density channels Δρorbi with the 9708


Article

Inorganic Chemistry

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Ligand-Driven Coordination Sphere-Induced Engineering of Hybride

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