Syntheses,structures, photoluminescences of silver(I) coordination polymers with 2-aminopyrazine and varied dicarboxylate ligands

Four new silver(I) coordination polymers, namely [Ag(NH₂pyz)(ox)_0.5]_n (1), [Ag(NH₂pyz)(adp)_0.5·2H₂O]_n (2), [Ag₂(NH₂pyz)₂(bdc)·H₂O]_n (3) and [Ag₂(NH₂pyz)_2.5(ndc)]_n (4) [NH₂pyz = 2-aminopyrazine, ox = oxalate anion, adp = adipate anion, bdc = 1,4-benzenedicarboxylate anion, ndc = 1,4-naphthalenedicarboxylate anion] have been synthesized by solution phase ultrasonic reactions of Ag₂O with heterocyclic NH₂pyz and various dicarboxylates under ammoniacal conditions. The complexes were characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. Complex 1 is a three-dimensional (3D) framework with an α-ThSi₂ topology. Complex 2 features a 2D 4⁴-sql net involving infinite 1D double Ag-NH₂pyz chains and flexible adp anion spacers. Complex 3 is a 3D framework in which 1D single Ag-NH₂pyz chains are pillared by bdc anions to form a 2D 6³-hcb network, adjacent 2D networks are packed into a 3D framework through bridging O atoms of dbc anions. Complex 4 is a 2D structure built from infinite 1D stair-like chains containing finite Ag₄(NH₂pyz)₅ subunits. The results show that the structural diversity of the complexes result from the nature of the dicarboxylate ligands. The photoluminescence properties of the complexes were also investigated in the solid state at room temperature.     

New rhodium(I) supramolecular structures containing pyridyl and bipyridyl ligands

The use of dimeric [RhCl(CO)₂]₂ as acceptor unit in the construction of mono-, bi- and three-dimensional metallosupramolecular structures is reported.The reaction of the dimer with the alkynylgold complex [Au(CCC₅H₄N)(CNC₆H₄O(O)CC₆H₄OC₁₀H₂₁)] resulted in the mononuclear rhodium complex 1, through an unexpected transfer of the isonitrile ligand from the gold to the rhodium centres.The reaction of the linear unit [RhCl(CO)₂]₂(μ-4,4′-bipy) (3) with the diphosphine 1,4-bis(diphenylphosphino)butane (dppb) yielded the simultaneous formation of both metallomacrocycles [RhCl(CO)(dppb)]₂ (4) and {[RhCl(CO)]₂(μ-4,4′-bipy)}₂(μ-dppb)₂ (5). The use of a diphosphine with smaller bite angle, 1,1′-bis-(diphenylphosphino)methane, (dppm) formed the three-dimensional {[RhCl(CO)]₂(μ-4,4′-bipy)}₂(μ-dppm)₄ complex (6) that incorporates four diphosphine units connecting two [RhCl(CO)₂]₂(μ-bipy) linear edges. PM3 semi-empirical method has been used to calculate the optimised geometry of compound 6.     

Syntheses and crystal structures of cadmium(II)X2-hexamethylenetetramine (X = Br/I/SCN) coordination polymers having different dimensionality

Four new coordination polymers of cadmium(II) with hexamethylenetetramine (htm) have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single crystal structure analysis. They are [CdBr(htm)(SCN)(H₂O)₂·CH₃OH]_n (1), [CdI(htm)(SCN)(H₂O)₂·0.5(CH₃OH)]_n (2), [Cd₂(htm)₃(SCN)₄(H₂O)]_n·nH₂O (3) and [Cd₃Br₆(htm)₂(H₂O)₅·(htm)(H₂O)₆]_n (4). Complexes 1, 2 and 3 exhibit 1D polymeric structure and complex 4 shows a 2D undulated layered arrangement, containing Cd₆(htm)₆ hexagonal units as building block, which extended to a 3D supramolecular architecture through hydrogen bonding. Thorough thermal investigation suggest that as far as the thermal stability of Cd(II)-htm bond is concerned it attains the maximum in complex 1 and minimum in complex 4. In case of complex 3 the thermal study inferred that CdS end product was obtained at ∼730 °C, whereas in case of other complexes the thermally stable end product remained unidentified. Solid state fluorescence study shows that all the complexes are luminescent at room temperature except complex 3.     

Two luminescent frameworks constructed from lead(II) salts with carboxylate ligands containing dinuclear lead(II) units

Two luminescent Pb(II) coordination frameworks containing dinuclear lead(II) units, [Pb(PYDC)(H₂O)]_n (1) and [Pb(HPHT)]_n (2) have been prepared by the self-assembly of lead(II) salts with pyridinecarboxylate and benzenecarboxylate. Single-crystal X-ray diffraction analyses reveal that compound 1 is a three-dimensional architecture consisting of Pb₂O₂ dimeric building units, whereas compound 2 is a two-dimensional layer structure containing one-dimensional lead-oxide chains. The luminescent properties of 1 and 2 have been investigated in the solid state at room temperature, indicating structure-dependent photoluminescent properties of the coordination frameworks.     

1D coordination polymers of silver(I) and copper(II) based on bis(N-heterocyclic carbene) ligands: Synthesis and structural studies

The alkyl chain-linked diimidazolium (or dibenzimidazolium) salts, 1,1′-diethyl-4,4′-tetramethylene-diimidazolium-diiodide (L¹H₂·I₂) and 1,1′-diethyl-3,3′-trimethylene-dibenzimidazolium-diiodide (L²H₂·I₂), and their silver(I) and copper(II) coordination polymers, [L¹AgI]_n (1) and [L²Cu₂I₄]_n (2), have been prepared and characterized. Complex 1 is a 1D helical polymer generated by bidentated carbene ligands (L¹) and Ag(I) atoms. The 1D polymer of 2 is formed by bidentated carbene ligands (L²) and coplanar quadrilateral Cu₂I₂ units. 3D supramolecular frameworks in the crystal packings of 1 and 2 are formed via intermolecular weak interactions, including C–H···π contacts, π–π interactions and C–H···I hydrogen bonds.     

New cationic palladium (II) and rhodium (I) complexes of [Ph2PCH2C(Ph)N(2,6-Me2C6H3)]

Treatment of the bulky iminophosphine ligand [Ph₂PCH₂C(Ph)N(2,6-Me₂C₆H₃)] (L) with [M(CH₃CN)₂(ligand)]⁺ⁿ, where for M = Pd(II): ligand = η³-allyl, n = 1, and for M = Rh(I), ligand: 2(C₂H₄), 2(CO) or cod, n = 0, yields the mono-cationic iminophosphine complexes [Pd(η³-C₃H₅)(L)][BF₄] (1), [Rh(cod)(L)][BF₄] (2), [Rh(CO)(CH₃CN)(L)][BF₄] (3), and cis-[Rh(L)₂][BF₄] (4). All the new complexes have been characterised by NMR spectroscopy and X-ray diffraction. Complex 1 shows moderate activity in the copolymerisation of CO and ethene but is inactive towards Heck coupling of 4-bromoacetophenone and n-butyl acrylate.     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

Exploring the reactivity of an N-pyrazole, P-phosphine hybrid ligand with Cu(I), Ag(I) and Au(I) precursors

The reactivity of (3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphine (L) hybrid ligand against Cu(I), Ag(I) and Au(I) has been assayed and compounds [Cu(L)₂](PF₆) (1), [Ag(L)]₂(PF₆)₂·2C₂H₄Cl₂·2C₄H₁₀O (2) and [AuCl(L)]₂ (3) have been isolated and fully characterised. A fully characterisation by analytical and spectroscopic methods of 1-3 are presented and X-ray crystal structures of 1 and 2 are also reported. The similar data obtained between 2 and 3 permits to do a serious purpose of the structure of 3 in solid and solution.     

Dimeric and polymeric silver(I) saccharinato complexes of two bis(pyridine) ligands: Synthesis,structural, spectroscopic,fluorescent and thermal properties

The reaction of silver(I) with 1,2-bis[1-(pyridin-2-yl)ethylidene]hydrazine (bpeh) and N,N-bis(pyridin-2-ylmethyl)amine (bpma) in the presence of Na(sac) (sac = saccharinate) yielded [Ag₂(sac)₂(bpeh)] (1) and [Ag(sac)(bpma)]_n (2) with conformational chirality. Both complexes have been characterized by elemental analysis, IR, thermal analysis and X-ray single crystal diffraction. Complex 1 displays a binuclear composition, in which each silver(I) ion is bound to one monodentate sac ligand and one of the bidentate pyridylimino groups of the bpeh ligand in a distorted trigonal coordination geometry. Complex 2 is a one-dimensional helical polymer, in which silver(I) centers are bridged by tridentate bpma ligands, and each silver(I) ion is coordinated in a distorted tetrahedral geometry by one monodentate sac ligand, a bidentate pyridylamine group of one bpma ligand, and a py group of another bpma ligand. Weak intermolecular C–H?O hydrogen bonds and C–H?π interactions lead to assembly of 1 and 2 into three-dimensional supramolecular frameworks. Spectral and thermal analysis data for 1 and 2 are in agreement with the crystal structures. In addition, both complexes in the solid state display intraligand π–π∗ fluorescence.     

Synthesis of a new N,N-ethane-1,2-bis(4-methoxyphenyl)carbothioamide ligand and its Cu(I) and Ag(I) complexes

[Cu(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O (2) and [Ag(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O (3) complexes of a new flexible thioamide ligand; N,N′-ethane-1,2-bis(4-methoxyphenyl)carbothioamide H₂L (1) have been synthesized using PPh₃ as a coligand. The synthesized compounds have been characterized with the help of elemental analyses, IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The ligand and its Cu(I) complex have been studied by single crystal X-ray crystallography. The ligand acts as a neutral S-donor and forms a nine-membered chelate ring in [Cu(H₂L)(PPh₃)₂]NO₃ · 0.5H₂O. The molecular packing is stabilized by an anionic cavity formed by intermolecular hydrogen bonding between the basal plane of the complex molecule and the nitrate ions. The square shaped columnar channel has dimensions of 5.489(25) [N(11)–H(11A)?O(13)?H(21A)N(21)] × 3.693(7) [N(11)–C(11)–C(21)–N(21)] Å.     

Syntheses,structures and luminescent properties of four copper(I) cyanide coordination polymers based on 2-(n-pyridyl)benzimidazole ligands (n = 2, 3, 4)

Four copper(I) cyanide coordination polymers containing 2-(n-pyridyl)benzimidazole ligands, namely [Cu₂(CN)(2-PyBIm)]_n (1), [Cu₂(CN)₂(3-PyHBIm)]_n (2), {[Cu₃(CN)₃(4-PyHBIm)₄] · 2H₂O}_n (3) and [Cu₅(CN)₃(4-PyBIm)₂]_n (4), have been synthesized and characterized by X-ray crystallography. Complex 1 is a one-dimension coordination polymer in which 2-(2-pyridyl)benzimidazole is deprotonated and adopts a bridging tridentate coordination mode. Complex 2 has ladder-like structure in which 2-(3-pyridyl)benzimidazole does not deprotonate and acts as a bidentate bridge. Complex 3 displays a saddle-shaped helical chain constructed through μ₂-cyanide group and the outstretched neutral 2-(4-pyridyl)benzimidazole monodentate ligand. Complex 4 shows two-dimension layer polymeric structure in which deprotonated 2-(4-pyridyl)benzimidazole acts as a tridentate bridging ligand. The cyanide groups in four complexes all act as bidentate bridging ligands. These complexes are thermal stable and display luminescence in the solid states.     

Syntheses,topological networks and properties of four complexes based on 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole ligand

Reactions of metal acetates with 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole (3-abpt) and co-ligands gave rise to four new complexes, namely [Zn₂(3-abpt)(beta)(DMF) (H₂O)₂]_n·nH₂O (1), [Zn(3-abpt)(ip)]_n·3nH₂O (2), [Zn(3-abpt)(ip)(H₂O)₂]_n·2nH₂O (3), and [Cu₂(3-abpt)₂(C₆H₅COO)₄(H₂O)₂]_n·2nH₂O (4) (ip = isophthalate, beta = 1,2,4,5-benzenetetracarboxylate). Compound 1 is a 3D coordination polymer with uncommon 3,4-connected (6².8)₂(6².8².10²) network. Compounds 2–4 are all 1D coordination polymers, which exhibit diversity structures. Compound 2 is a tubular-like chain, 3 is a ring-like network, and 4 is a zigzag chain. Their thermal stabilities and the photoluminescence of 1 have also been investigated.     

Coordination polymers and supramolecular structures in Ag(I)triflate-dppf systems (dppf=1,1-bis(diphenylphosphino)ferrocene)

The interaction of silver triflate (OTf⁻=SO₃(CF₃)⁻) and dppf [(C₅H₄PPh₂)₂Fe)] gave different complexes, depending on the stoichiometric proportions and reaction conditions. Under limiting dppf conditions, three different forms (1-3) of [Ag₂(OTf)₂(dppf)]_x were isolated. Single crystal X-ray diffraction analyses showed that the structure of 1 (x=2n) consists of a 2-D polymer comprising a tetra-silver basic unit, while that of 2 (x=2) possesses a discrete tetra-silver framework and that of 3 (x=n) is a linear polymer based on a di-silver repeating unit. The structures are supported by bridging dppf ligands and triflate groups. The crystal lattices of the compounds are stabilized by extensive intermolecular C-H?X hydrogen bonding (H=ring proton of Cp or Ph of dppf; X=O or F of OTf). [Ag(dppf)(OTf)] (4) and the structurally characterized mononuclear [Ag(dppf)₂](OTf) (5) were the sole products obtained from treatment of AgOTf with dppf in molar ratios of 1:1 and 1:2, respectively.     

Restricting the versatile metal-binding behaviour of adenine by using deaza-purine ligands in mixed-ligand copper(II) complexes

In order to deepen our understanding of the versatile behaviour of adenine (Hade) as ligand, we have synthesized four novel ternary copper(II) complexes having two deazaadenine ligands, namely 4-azabenzimidazole (H4abim) or 7-azaindole (H7azain) as N1,N6-dideazaadenine or N1,N6,N7-trideazaadenine, respectively. The related compounds were studied by thermal, spectral and single crystal X-ray diffraction methods. In [Cu(NBzIDA)(H4abim)]_n (1) the recognition between H4abim and the (N-benzyliminodiacetate)-copper(II) chelate only displays the formation of the Cu–N7(purine-like) bond, in contrast to Hade behaviour in [Cu(NBzIDA-like)(Hade)(H₂O)]·H₂O (Cu–N3(Hade) bond reinforced by N9–H···O(IDA-like) interaction). In [Cu(EIDA)(H7azain)(H₂O)] (2, EIDA = N-ethyliminodiacetate ligand), [Cu(NBzIDA)(H7azain)(H₂O)] (3) and [Cu(μ₂-SO₄)(H7azain)₂(H₂O)₂]_n (4), H7azain binds Cu(II) centre by the Cu–N3(purine-like) bond, reinforced by a N9–H···O(IDA-like or sulfate) intra-molecular interligand interaction.     

Syntheses and crystal structures of straight or zigzag one-dimensional coordination polymers based on Cu(II) square pyramidal or Cu(I) tetrahedral coordination environments

Two coordination polymers containing copper ions, [Cu(SO₄)(pyz)(H₂O)]_n (1) and [Cu₂(SO₄)(pyz)₂(H₂O)₂]_n (2) (pyz = pyrazine), have been synthesized and characterized by single-crystal X-ray analyses. Compound 1 was synthesized by the reaction of Cu(SO₄) · 5H₂O with pyz (ratio = 1:2) in H₂O at room temperature. The structure of 1 consists of linear chains of [Cu(pyz)(H₂O)]²⁺, with coordinated sulfate ions bridging the chains. Compound 2 was obtained as dark red blocks from the reaction of Cu(SO₄) · 5H₂O and pyz (ratio = 1:2) in H₂O, after heating to 180 °C in a Teflon autoclave for 48 h. The structure of 2 consists of zigzag chains of [Cu(pyz)(H₂O)]⁺ with sulfate ions. Only the difference in the synthesis temperature, room temperature or 180 °C, determines whether Cu(II) or Cu(I) coordination polymers are formed, with the reduction of Cu(II) to Cu(I) being explained by the Gillard mechanism.     

A series of silver coordination polymers constructed from flexible bis(benzimidazole) ligands and different carboxylates

In this article, eight new silver coordination polymers constructed from two structurally related ligands, 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole) (bbmb) and 1,1′-(1,4-butanediyl)bis(2-ethylbenzimedazole) (bbeb), have been synthesized: [Ag(L1)(bbmb)]·C₂H₅OH·H₂O (1), [Ag(L2)(bbmb)]·C₂H₅OH (2), [Ag(L3)(bbmb)] (3), [Ag₂(L4)(bbmb)₂]·C₂H₅OH (4), [Ag(L2)(bbeb)]·C₂H₅OH (5), [Ag(L5)(bbeb)]·CH₃OH (6), [Ag₂(L6)₂(bbeb)]·H₂O (7), and [Ag₂(L7)(bbeb)₂]·4(H₂O) (8), where L1 = benzoate anion, L2 = p-methoxybenzoate anion, L3 = 2-amino-benzoate anion, L4 = oxalate anion, L5 = cinnamate ainon, L6 = 3-amino-benzoate anion, and L7 = fumaric anion. In 1-3, 5 and 6, the bidentate N-donor ligands (bbmb and bbeb) in trans conformations bridge neighboring silver centers to form 1D single chain structures. The carboxylate anions are attached on both sides of the chains. Moreover, 1 and 3 are extended into 2D layers, while 2 and 6 are extended into 3D frameworks through π-π interactions. In 4, the bbmb ligands bridge adjacent Ag(I) centers to form -Ag-bbmb-Ag- chains, which are further connected by L4 anions to form a 2D layer. The resulting layers are extended into 3D frameworks through strong π-π interactions. In 7, the N-donor ligands (bbeb) in trans conformations bridge two silver centers to generate a [Ag₂(bbeb)]²⁺ unit. The adjacent [Ag₂(bbeb)]²⁺ units are further connected via the L6 anions to form a 1D ladder chain. Moreover, the structure of compound 7 is extended into a 3D framework through hydrogen bonding and π-π interactions. In 8, two Ag(I) cations are bridged by two bbeb ligands in cis conformations to form a [Ag₂(bbeb)₂]²⁺ ring, which are further linked by L7 anions to generate a 1D string chain. Furthermore, the hydrogen bonding and π-π interactions link L7 anions to form a 2D supramolecular sheet. Additionally, the luminescent properties of these compounds were also studied.     

Assembly of silver(I) coordination polymers incorporating pyromellitic acid and N-heterocyclic ligands

Five mixed ligands coordination polymers [Ag₄(apym)₂(pma)·(H₂O)₂]_n (1), {[Ag₄(dmapym)₄(pma)·(H₂O)₂]·(H₂O)₆}_n (2), [Ag₂(apyz)₂(H₂pma)·(H₂O)₄]_n (3), {[Ag₄(apyz)₂(pma)·(H₂O)₂]·(H₂O)₂}_n (4) and [Ag₄(NH₃)₈(pma)·(H₂O)₆]_n (5) (apym = 2-aminopyrimidine, dmapym = 4, 6-dimethyl-2-aminopyrimidine, apyz = 2-aminopyrazine, H₄pma = pyromellitic acid) were synthesized and characterized. For 1 and 2, as the substituents change from H to methyl, the dimensions of 1–2 decrease from three-dimension (3D) to one-dimension (1D) due to the steric effect of methyl groups. For 3 and 4, as the ratios of Ag₂O/apyz/pma vary from 1:1:1 to 2:1:1, the structure of 3 is a 1D ladder structure built from Ag-apyz double chains and pma anions, while the structure of 4 is a two-dimension (2D) grid. As excess ammonia is added to above four reaction systems, the structure of 5 contains unprecedented {[Ag(NH₃)₂]⁺}_n chains and pma anions. The substituent on the pyrimidyl ring, ratios of reactants, solvent systems and ligand isomers intensively influence the coordination environments of metal ion and the coordination modes of the carboxyl group, and thus determine the structures of the coordination polymers. The photoluminescent properties of 1–5 were also investigated.     

One-dimensional silver(I) 5,5-diethylbarbiturato coordination polymers with N-piperidineethanol and 1,3-bis(4-piperidyl)propane: Syntheses,crystal structures,spectroscopic and thermal properties

Two new coordination polymers, [Ag₂(barb)(pipet)]_n (1) and {Na₃[Ag₂(barb)₂](pippr)·2H₂O}_n (2) (where H₂barb, pipet and Hpippr are 5,5-diethylbarbituric acid, N-piperidineethanol and 1,3-bis(4-piperidyl)propane, respectively) have been synthesized and characterized by elemental analysis, IR, thermal analysis and X-ray single-crystal diffraction techniques. Silver(I) ions in complexes 1 and 2 are bridged by barb dianions, leading to one-dimensional coordination polymers. In 1, the barb ligand acts as a tetradentate bridging ligand, while in 2 as a bidendate bridging ligand. The pipet ligand behaves as a bidentate chelating donor, whereas the pippr anion is not involved in coordination and remains as a counter-ion. The one-dimensional chains of 1 and 2 are further extended into supramolecular networks. Spectral and thermal analysis data for 1 and 2 are in agreement with the crystal structures.     

pH- and mol-ratio dependent formation of zinc(II) coordination polymers with iminodiacetic acid: Synthesis, spectroscopic, crystal structure and thermal studies

Three novel zinc coordination polymers (NH₄)_n[Zn(Hida)Cl₂]_n (1), [Zn(ida)(H₂O)₂]_n (2), [Zn(Hida)₂]_n·4nH₂O (3) (H₂ida=iminodiacetic acid) and a monomeric complex [Zn(ida)(phen)(H₂O)]·2H₂O (4) (phen=1,10-phenanthroline) have been synthesized and characterized by X-ray diffraction methods. 1 and 2 form one-dimensional (1-D) chain structures, whereas 3 exhibits a three-dimensional (3-D) diamondoid framework with an open channel. The mononuclear complex 4 is extended into a 3-D supramolecular architecture through hydrogen bonds and π-π stacking. Interestingly, cyclic nonplanar tetrameric water clusters are observed that encapsulated in the 3-D lattice of 4. Based on ¹H and ¹³C NMR observations, there is obvious coordination of complex 2 in solution, while 1 and 3 decompose into free iminodiacetate ligand. Monomer [Zn(ida)(H₂O)₃] (5) is considered as a possible discrete species from 2. These coordination polymers can serve as good molecular precursors for zinc oxide.     

Two lead(II) 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate complexes exhibiting different topologies and fluorescent properties

The reactions of PbCl₂ with 2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid (H₃iso) gave two complexes [Pb(H₂iso)₂(H₂O)]_n (1) and [Pb(Hiso)(H₂O)]_n (2), which were characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and single crystal X-ray diffraction analysis. The two complexes display different topologies. 1 shows a three-dimensional framework with the Schläfli symbol (4.8⁵)(4.8²) no matter if the weak Pb-O bonds are included or not. However, 2 presents a 3,3-connected two-dimensional sheet with the Schläfli symbol (4.8²)(4.8²) based on the calculation of only the normal Pb-O bonds and a 5,5-connected 3D network with the Schläfli symbol (4¹⁵.6⁴)(4⁴.6⁸.8²) when the weak Pb-O bonds are also included. The fluorescent studies reveal an emission attributed to intraligand emission for 1 and an emission assigned to LMCT for 2.