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DOI: 10.1002/zaac.201000426

Sonochemical Synthesis of a Novel Nanoscale Lead(II) CoordinationPolymer: Synthesis, Crystal Structure, Thermal Properties, and

DFT Calculations of [Pb(dmp)(μ-N3)(μ-NO3)]n with the Novel Pb2(μ-N3)2(μ-NO3)2 Unit

Behrouz Shaabani,*[a] Babak Mirtamizdoust,[a] Davide Viterbo,[b] Gianluca Croce,[b]Hassan Hammud,[c] Pejman Hojati-Lalemi,[d] and Aliakbar Khandar[e]

Keywords: Lead; Azides; Coordination polymers; Nanostructure; Density functional calculations

Abstract. A new nanostructured coordination polymer of divalent leadwith the ligand 2,9-dimethyl-1,10-phenanthroline (dmp), [Pb(dmp)(μ-N3)(μ-NO3)]n (1), was synthesized by sonochemical methods. The poly-mer was characterized by scanning electron microscopy, X-ray pow-der diffraction, IR, 1H NMR, and 13C NMR spectroscopy, and elemen-tal analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The single-crystal analysis shows that the

Introduction

The synthesis and characterization of infinite networks hasbeen an area of rapid growth in recent years.[1] The motivationbehind much of this activity has been provided by the prospectof generating a wide range of purpose-built materials with pre-determined structures and useful properties (e.g. electronic,magnetic, optical, and catalytic) by deliberate design.[2] Infinitemetal-ligand assemblies, where the metal-organic connectivityis interrupted by “inorganic” bridges, such as –(R,H)O–, –Cl–,–CN–, –N3–, –(R,O)PO3– and –(R,O)SO3– or where an ex-tended inorganic metal-ligand network is only linked by termi-nal organic ligands are called organic-inorganic hybrid-materials.[3]

* Dr. B. ShaabaniFax: +98-411-3340191E-Mail: shaabani_b@yahoo.com

[a] Synthesis of Inorganic Compounds Research LaboratoryFaculty of ChemistryUniversity of TabrizTabriz, Iran

[b] Dipartimento di Scienze e Tecnologie AvanzateUniversitá del Piemonte OrientaleAlessandria, Italy

[c] Department of Chemistry, Faculty of ScienceBeirut Arab UniversityBeirut, Lebanon

[d] Department of Materials EngineeringMonash UniversityClayton, Victoria 3800, Australia

[e] Coordination Chemistry Research Laboratory, Faculty ofChemistryUniversity of TabrizTabriz, Iran

Z. Anorg. Allg. Chem. 2011, 637, 0000–0000 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1

coordination number of PbII ions is seven, (PbN4O3) has a “stereo-chemically active” electron lone pair, and the coordination sphere ishemidirected. The chains interact with each other through π–π stackinginteractions to create a 3D framework. The structure of the title com-plex was optimized by density functional calculations. The calculatedstructural parameters and the IR spectrum of the title complex are inagreement with the crystal structure.

Azido-bridged complexes have attracted intense interest dueto the coordination versatility of the azido bridge and the mag-netic diversity of the complexes.[4] The azido ligand is able tolink two or more metal ions in various modes; μ-1,1 (end-on,EO), μ-1,3 (end-to-end, EE), μ-1,1,3 and others, and to mediatemagnetic exchange of different nature and magnitude. Thesemodes may simultaneously exist in the same compound in avariety of alternating sequences.[5] The above features in con-junction with the presence of co-ligands led to several 1D and2D architectures with interesting polymeric topologies and/ormagnetic properties.[6] An interesting strategy toward high di-mensional topologies is to incorporate a second bridging ligandinto the metal–azido systems. An increasing number of 2D and3D systems were obtained by this strategy. Second bridgingligands used thus far have been pyridyl-based ditopic ligandssuch as pyrazine, 4,4'-bipy and their analogues.[7]

Compared to the relatively large number of azido-bridgedpolymers with MnII, NiII, and CuII reported in the literature,[8]

PbII polymers are still very rare.PbII stereochemistry is conditioned by the structural effect ofthe 6s2 electron pair (PbII configuration: [Xe] 4f145d10 6s2).Whether or not this electron pair is “stereochemically active”has a very significant influence on the arrangement of PbII

coordination compounds (vide infra).[9] This influence can beunderstood in terms of simple hybridization or valence shellelectron-pair repulsion arguments (an alternative approach tothis topic has recently been published[10]). On using the formerapproach, it seems that the 6s orbital, in spite of its stabiliza-tion, is able to hybridize with the 6p orbitals to give a “stereo-chemically active” 6s electron pair that occupies one positionin the coordination sphere of the metal. Because the electron

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pair is not directly detectable, its presence is ususally identifiedby a void in the distribution of the coordination bonds (hemidi-rected coordination). If hybridization does not occur and thepair has only s character, then it is “stereochemically inactive”and the complex does not show a gap or void in the bonddistribution (holodirected coordination).[11]Solid energetic substances have long played an importanttechnological role as explosives. Metal azides serve as a proto-type for more complex energetic solids. Attempts at character-izing the probable solid-state electronic structure of metal az-ides are described in a review article by Young [12].Lead azide is a primary explosive and is widely used as aprimer. The sodium and lithium azide systems are much morebenign in behavior. Therefore, to gain an understanding of thebehavior patterns observed, one should know the importanceof the fundamental electronic structure properties of this classof solids.[13] Nanometer-sized particles of metal coordinationpolymers are fascinating to explore, since their unique proper-ties are controlled by the large number of surface molecules,which experience an entirely different environment than thosein a bulk crystal. Controlling the growth of materials at thesubmicrometer scale is of central importance in the emergingfield of nanotechnology.[14] The first lead(II) coordination pol-ymer with a versatile azido-bridging agent was synthesized inour research group and recently we have reported the first the-oretical study of lead(II)–azido complexes.[15] As a continua-tion of the previous study, in this paper we extend these studiesto investigate the interactions of the universal bridging azideanion with lead(II) ions in the presence of aromatic aminesand describe the simple sonochemical preparation of nano-structures of this coordination polymer.

Results and DiscussionSpectroscopic Studies

The reaction of the “dmp” ligand with a mixture of lead(II)nitrate and sodium azide using two different routes providedcrystalline materials of the general formula [Pb(dmp)(μ-N3)(μ-NO3)]n (1). Scheme 1 gives an overview of the methods usedfor the synthesis of compound 1 using two different routes.

Scheme 1. Synthetic methods and materials produced.

The elemental analysis and IR spectra of the nanostructuresand the single crystalline material are indistinguishable. TheIR spectra of the nanostructures and the single crystalline ma-terials show the characteristic absorption bands of the “dmp”ligand. The selected spectroscopic data and the correspondingdata obtained from DFT calculations are given in Table 1. Therelatively weak band around 3025 cm–1 is attributed to the ab-

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sorption of the aromatic CH hydrogen atoms and the bandaround 2990 cm–1 is attributed the absorption of the aliphaticCH hydrogen atoms. The band at 1350 cm–1 is due to the(NO3)– stretching vibration. The strong doublet at 2053–2075 cm–1 corresponds to νasym(N3–) and indicates the end-on(μ-1,1) bonding mode of N3–.[16] The 1H NMR spectrum of theDMSO solution of 1 displays a distinct peak at 2.78 ppm,which is assigned to the aliphatic protons of the “dmp” ligand.The peaks of 7.67, 7.87, and 8.35 ppm are assigned to thearomatic protons of the “dmp” ligand. The 13C NMR spectrumof the DMSO solution of compound 1 displays six distinctpeaks, which are assigned to the aromatic carbon atoms of the“py” groups of the “dmp” ligand and another peak at 24 ppm,which is assigned to the methyl group carbon atoms of the“dmp” ligand.

Table 1. Experimental FT-IR frequencies /cm–1 for [Pb(dmp)(μ-N3)(μ-NO3)]n (1), compared with the theoretical frequencies obtained fromDFT calculations.

Assignment Experimental Calculated

ν(C–H)aliphatic 2990 m 3027ν(C–H)aromatic 3025 w 3210ν(C–H) 708 m 717ν(CC) 1470 s, 1575 s 1490, 1591ν(NO3)– 1350 vs 1366ν(N3)– 2053 vs, 2075 s 2070, 2100ν(Pb–N) 340

Figure 1 shows the XRPD pattern calculated from singlecrystal data (see below) of compound 1 in comparison with theXRPD pattern of the typical nanolayer sample of 1 prepared bya sonochemical process (Figure 1a and b, respectively).

Figure 1. The XRPD patterns of compound 1. (a) Computed fromsingle-crystal X-ray data; (b) nanostructure of compound 1.

The acceptable match observed between the simulated andexperimental powder X-ray diffraction patterns, with veryslight differences in peak positions, (Figure 1) indicates thatthe nanolayer sample is a single crystalline phase, which isidentical to the one obtained by single crystal diffraction. Thesignificant broadening of the peaks of the nanostructure (Fig-

A Novel Nanoscale Lead(II) Coordination Polymer

ure 1b) indicates that the particles are of nanometer dimen-sions. The average size of the particles was estimated by theScherrer formula, D = 0.891λ / βcosθ, where D is the averagegrain size, λ the X-ray wavelength (0.71069 Å), θ the diffrac-tion angle, and β the full-width at half maximum of an ob-served peak. The obtained value for D amounts to 65 nm. Fig-ure 2 shows the nanolayers observed by scanning electronmicroscopy. The morphology of compound 1 prepared by son-ochemical methods (Figure 2) is very interesting. It is com-posed of cross-sheets with a thickness of about 65 nm thatform a flower like network (Figure 2). The formation mecha-nism of this network structure needs to be further investigated,however it may be a result of the crystal structure of the com-pound, which is a two-dimensional layered network (see be-low), packing of the structure on a molecular level might haveinfluenced the morphology of the nanostructure of the com-pound.

Figure 2. SEM photographs of [Pb(dmp)(μ-N3)(μ-NO3)]n (1) nanolayers.

The structure determination of [Pb(dmp)(μ-N3)(μ-NO3)]n bysingle-crystal X-ray analysis[17] showed that the complex crys-tallizes in the triclinic system with space group P1̄, taking theform of a one dimensional polymer in the solid state (Fig-ure 3). Each lead atom is chelated by two nitrogen atoms of“dmp” with Pb–N distances of 2.647(3) and 2.636(4) Å, twoazide anions with Pb–N distances of 2.413(4) and 2.554(4) Å,and three nitrate oxygen atoms with Pb–O distances of2.975(5), 2.761(4), and 2.761(4) Å (Figure 4).

Figure 3. Fragment of the coordination polymer showing the 1D polymer.

Lead–oxygen separations in the range of 2.38 to 3.07 Å wereconsidered, on the basis of bond valence calculations, to indi-

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Figure 4. Molecular structure of the asymmetric unit of [Pb(dmp)(μ-N3)(μ-NO3)]n.

cate significant bonding interactions. Besides, there are numer-ous examples[18] of “long” Pb···X contacts, which are muchshorter than the next longest distances and thus have been con-sidered to be indicative of weak attractions. The coordinationnumber of lead in this complex is seven (two links with “dmp”ligands, three with nitrate ions, and two with azide anions).The lead(II) ions are bridged by two azide ions in a μ2-1,1end-to-on fashion with a Pb···Pb distance of 4.115 Å in thepolymeric units. The nitrate anions coordinate to lead as singlebidentate ligands and also bridge two adjacent Pb2+ ions, witha Pb···Pb separation of 5.392 Å in the polymeric units. A sche-matic representation of the PbII environment is shown in Fig-ure 5. The arrangement of the “dmp” ligands and nitrate andazide anions suggests a gap or hole in the coordination ar-rangement around the metal ion [N3–Pb1–O1 angle163.69(12)°], which is possibly occupied by a stereo-activeelectron lone pair on lead(II).[11] The observed shortening ofthe Pb–N bonds on the side of the Pb2+ ion opposite to theputative lone pair [2.413(4) Å compared with 2.554(4) Å adja-cent to the lone pair] supports this hypothesis.[19]

Figure 5. Schematic representation of PbII environment.

There are two different types of noncovalent π–π stackinginteractions[20] between the parallel aromatic rings belongingto adjacent chains, as shown in Figure 6 and Figure 7. The

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interplanar distances of the “dmp” ligands (Figure 6) are 3.48and 3.50 Å (our measurements are 3.37 and 3.65 Å), which isappreciably shorter than the normal π–π stacking.[21] Conse-quently, the π–π stacking interactions also allow the 1D struc-ture to form a three dimensional network (Figure 7).

Figure 6. Projection of the nearest neighbor pair π–π stacks of hete-roaromatic bases in [Pb(dmp)(μ-N3)(μ-NO3)]n.

Figure 7. Packing of 1D Chains to form 3D supramolecular layers viaπ–π stacking interactions.

Thus, two factors, lone pair activity and π–π stacking, maycontrol the coordination sphere of the lead(II) ions in this com-plex. The obvious question is whether the lone pair activityhas stretched coordinate bonds to result in ligand stacking orwhether the stacking interaction imposed a positioning of thedonor atoms to form a gap in the coordination sphere. How-ever, one could say that the cooperative effect of the π–π inter-actions and the presence of a lone pair give a closer packingof the solved structure.

Thermal Properties

Thermal analysis plays an important role in studying struc-ture and properties of metal complexes. In order to investigatethe thermal stability of [Pb2(dmp)2(μ-N3)2(μ-NO3)2]n (1), ther-

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mogravimetric analyses (TGA) and differential scanning calor-imetry (DSC) analyses were performed on a crystalline sampleof 1 from 25 °C to 800 °C under nitrogen.[22] The TG curvesof 1 showed continuous weight loss and thus structural change(from 50 °C to up to about 245 °C), demonstrated that theframework decomposes over this range with a weight loss of21 % corresponding to the loss of one dmp ligand (in contrastto the TG curve of [Pb(dmp)I2]n, which shows structural stabil-ity for the complex upon heating from 25 °C up to 250 °C).[23]

Complex 1 shows a second sharp thermal decomposition at256 °C, with an exothermic peak (ΔH = –624.6 J·g–1) and aweight loss of 4.1 %, which corresponds to the loss of one N3–

ligand. The complex further shows a gradual weight loss from280 to 750 °C, which corresponds to complete decompositionof the complex with loss of the remaining dmp, N3–, and NO3–

ligands.

DFT Calculations

The calculated structural parameters are listed in Table 2. Itshould be noted that the experimental data belong to the solidphase, whereas the calculated data correspond to the isolatedmolecule in gas phase. However, the experimental and compu-tational data in Table 2 differ only slightly from each other.For example, the largest difference between the experimentaland calculated O2–Pb1 length is about 0.220 Å, whereas thelargest deviation of ca. 3.78° occurs for the N4–Pb1–O1 angle.The calculated geometrical parameters represent a good ap-proximation.

Table 2. Selected bond lengths /Å and angles /° for [Pb(dmp)(μ-N3)(μ-NO3)]n (1). Symmetry transformations used to generate equivalent at-oms: i = –x, –y, –z. (Experimental data belong to the solid phase,whereas the calculated data correspond to the isolated molecule in gas-phase).

Experimental Calculated

Pb1···Pb1i–1 4.115 4.204N2–Pb1 2.647(3) 2.594N3–Pb1 2.636(4) 2.694N4–Pb1 2.413(4) 2.405N4i–Pb1 2.554(4) 2.530O1–Pb1 3.048(5) 3.079O2–Pb1 2.975(5) 2.655O3–Pb1i–2 2.761(4) 2.709Pb1···Pb1i–2 5.392 5.476O1i–Pb1 2.761(4) 2.668N2–Pb1–N3 63.65(11) 63.55N4–Pb1–N2 87.09(13) 89.95N4–Pb1–N3 76.58(12) 76.16N4i–Pb1–N2 96.89(13) 94.04N4i–Pb1–N3 140.63(12) 138.25N4–Pb1–O1 153.94(14) 150.16N4–Pb1–O2 119.56(14) 118.20N3–Pb1–O1 163.69(12) 167.57N4i–Pb1–O1 78.36(14) 78.22N4i–Pb1–O2 84.57(14) 84.92O3i–Pb1–N4 88.00(13) 89.14O3i–Pb1–N4i 100.36(12) 103.50

The computed and the experimentally determined IR spec-troscopic frequencies are listed in Table 1. The assignment of

A Novel Nanoscale Lead(II) Coordination Polymer

the ν(Pb–N) vibration is based on the theoretically calculatedfrequency of 340 cm–1 for a lead complex [Pb(dmp)(μ-N3)(μ-NO3)]n.The Mulliken charges of lead(II) and of the coordinated at-oms were also calculated. The positive charge of the lead(II)ions was 1.068. The charges of the nitrogen atoms of the“dmp” ligands were –0.271 and –0.184, respectively, whereasthe nitrogen atoms of both azide anions (N4i and N4) havesimilar charges: N4i = –0.450 and N4 = –0.457. The calcula-tions indicate that complex 1 has 83 occupied molecular orbit-als (MOs) per [Pb(dmp)(μ-N3)(μ-NO3)] unit. The value of theenergy separation between the highest occupied molecular or-bital (HOMO) and the lowest unoccupied molecular orbital(LUMO) was calculated. Figure 8 shows the HOMO andLUMO for the lead(II) complex. As is obvious from Figure 8,the HOMO of the title complex is principally localized on twonitrogen atoms of the azide anion and three nitrogen atomsof the nitrate anion including lead(II), whereas the LUMO isapproximately delocalized on all atoms of the “dmp” ligand.The calculated HOMO–LUMO gap is 0.116 a.u. (3.148 eV).Compared with lead azide [Pb(N3)2] gap (4.7 eV)[13] and[Pb(dmp)(N3)2]n gap (1.662 eV),[15b] it was found that the gapwidth of complex 1 is between the [Pb(N3)2] bandgap and[Pb(dmp)(N3)2]n bandgap. Therefore, complex 1 can be ex-pected to be a primary explosive and to be medium sensitiveto shock.

Figure 8. Frontier molecular orbitals for a unit of [Pb(dmp)(μ-N3)(μ-NO3)]n.

ConclusionsA novel 1D PbII coordination polymer containing a universal

bridging ligand (azide anion) and a nitrate bridging ligand withlead(II) ions involving the Pb2(μ-N3)2(μ-NO3)2 unit in the pres-

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ence of aromatic amine (2,9-dimethyl-1,10-phenanthroline)is described together with sonochemical preparation of nano-structures of this coordination polymer. The crystal structureof the complex was also determined. In the solid state, it takesthe form of a one dimensional polymer. The arrangement ofthe ligands suggests a gap in the arrangement around the metalions possibly occupied by a “stereo-active” lone pair of elec-trons on lead(II). Two factors, lone pair activity and π–π stack-ing, may control the coordination sphere of lead ions in thiscomplex. A novel theoretical study of the title nitrato–lead(II)–azido complex allowed to examine its electronic structure andto compute bond length and angles and vibrational frequenciesin good agreement with the experimental data. The Pb···Pb in-teractions were estimated in accordance with the experimentalcrystal structure. The calculations indicate that the LUMO isdelocalized approximately on all atoms of the “dmp” ligand.The significant broadening of the XRPD peaks of the nano-structure indicates that the particles are of nanometer dimen-sions. Estimated by the Scherrer formula the average size ofthe particles is 65 nm. The morphology of compound 1 pre-pared by the sonochemical method is composed of cross-sheetswith thickness of about 65 nm, which form a flower-like net-work, observed by scanning electron microscopy.

Experimental SectionMaterials and Physical Measurements: All chemicals were obtainedfrom commercial sources and used as received. A multiwave ultrasonicgenerator (Sonicator 3000; Misonix Inc., Farmingdale, NY, USA),equipped with a converter/transducer and titanium oscillator (horn),12.5 mm in diameter, operating at 20 kHz with a maximum poweroutput of 600W at room temperature for 1 h, was used for the ultra-sonic irradiation. Infrared spectra were recorded in KBr pellets with aPerkin–Elmer 883-IR spectrophotometer and with a Nicolet 520 FTIRspectrophotometer. Elemental analyses (C, H, N) were performed witha Perkin–Elmer 2400 II elemental analyzer. X-ray powder diffraction(XRD) measurements were performed with a X'pert diffractometermanufactured by Panalytical, with monochromatized Cu-Kα radiationand simulated XRD powder patterns based on single crystal data wereprepared using the Mercury program.[24] The crystallite sizes of se-lected samples were estimated using the Scherrer formula. The sampleswere characterized with a scanning electron microscope with goldcoating. Melting points were measured with an Electrothermal 9100apparatus and are uncorrected. 1H NMR and 13C NMR spectra weremeasured with a BRUKER DRX-500 AVANCE spectrometer at500 MHz, respectively. Thermogravimetric-differential scanning calor-imetry (TG-DSC) curves were recorded with a SETARAM LABSYSthermal analyzer in the flow of nitrogen within the 25–800 °C temper-ature range, with a heating rate of 3 °C·min–1.

Preparation of [Pb(dmp)(μ-N3)(μ-NO3)]n (1): To prepare the nano-structure of [Pb(dmp)(μ-N3)(μ-NO3)]n (1), a 0.1 m solution (15 ml) oflead(II) nitrate in H2O was positioned in a high-density ultrasonicprobe, operating at 20 kHz with a maximum power output of 600 W.A 0.1 m solution (15 ml) of the ligands 2,9-dimethyl-1,10-phenanthro-line and sodium azide (0.1 m) was added dropwise. The obtained pre-cipitates were filtered off, washed with water and dried in air. M.p.244 °C. C28H24N12O6Pb2: calcd. C 32.37, H 2.33, N 16.18 %; found:C 32.25, H 2.22, N 16.13 %. IR (KBr): ν̃ 708 m,1350 vs, 1470 s, 1575s, 2053 vs, 2075 s, 2990 m, 3025 w cm–1.

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To isolate single crystals of [Pb(dmp)(μ-N3)(μ-NO3)]n (1), 2,9-dim-ethyl-1,10-phenanthroline (0.20 g, 1 mmol) was placed in one arm ofa branched tube[25] and a mixture of lead(II) nitrate (0.33 g, 1 mmol)and sodium azide (0.13 g, 2 mmol) in the other. Afterwards, methanolwas carefully added to fill both arms, the tube was sealed and theligand-containing arm was immersed in a bath at 60 °C, while theother was left at ambient temperature. After 2 weeks, crystals suitablefor an X-ray structure determination had deposited in the arm at ambi-ent temperature. They were filtered off, washed with acetone and ether,and air dried. Yield 65 %. M.p. 248 °C. C28H24N12O6Pb2: calcd. C32.37, H 2.33, N 16.18 %; found: C 32.20, H 2.20, N 16.10 %. IR(KBr): ν̃ 705 m,1350 vs, 1470 s, 1575 s, 2053 vs, 2075 s, 2990 m,3025 w cm–1. 1H NMR (DMSO): δ = 2.78 (s, 6 H, methyl-H), 7.67(s, 2 H, py-H), 7.87 (d, 2 H, py-H), 8.35 (d, 2 H, py-H) ppm. 13CNMR (DMSO): δ = 24 (methyl), 120 (py), 125 (py), 128 (py), 137(py), 140 (py), 158 (py) ppm.

Crystallography: Crystallographic data were collected at 100 K withthe Oxford Xcalibur CCD area detector diffractometer, using graphitemonochromatic Mo-Kα (λ = 0.71069Å) radiation. Data reduction andabsorption correction were performed using CrysAlis RED 1.171.26(Oxford Diffraction). The structure was solved by direct methods usingSIR2004[26] and refined by full-matrix least-squares using SHELX-97.[26] Hydrogen atoms were generated in calculated position usingSHELX-97.[26] Materials for publication were prepared usingSHELXTL[26] and ORTEPIII.[26]

Crystallographic data for the structure reported in this paper has beendeposited with the Cambridge Crystallographic Data Centre as supple-mentary publication CCDC-798926 for [Pb(dmp)(μ-N3)(μ-NO3)]n (1).Copies of the data can be obtained on application to CCDC, 12 UnionRoad, Cambridge CB2 1EZ, UK [Fax: +44-1223-336033; E-Mail: de-posit@ccdc.cam.ac.uk].

Computational Details: The geometry of the [Pb(dmp)(μ-N3)(μ-NO3)]n complex has been optimized using the B3LYP density func-tional model.[27] In these calculations we used the 3-21G* basis set forcarbon and hydrogen atoms, whereas the 6-31G* basis set was usedfor nitrogen and oxygen atoms. For the lead atoms, the LanL2DZ va-lence and effective core potential functions were used.[28] All DFTcalculations were performed by using the Gaussian 98 R-A.9package.[28b] X-ray structures were used as input geometries whenavailable.

AcknowledgementThe authors acknowledge financial support by University of TabrizResearch Council (project number sad/27/1391-3) and Università delPiemonte Orientale and Beirut Arab University is gratefully acknowl-edged. Thermal analyzer at BAU is provided by FP 6 European Com-mission Grants “MEDINDUS” Contract # 509159.

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Z. Anorg. Allg. Chem. 2011, 0000–0000 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.zaac.wiley-vch.de 7

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Received: December 9, 2010Published Online: ■