Theoretical study of one- and two-photon absorption properties of octupolar D2d and D3 bipyridyl metal complexes

The molecular equilibrium structures, electronic structures, and one- and two-photon absorption (TPA) properties of C2v (Zn(II), Fe(II) and Cu(I)) dipolar and D2d (Zn(II) and Cu(I)) and D3 (Zn(II)) octupolar metal complexes featuring different functionalized bipyridyl ligands have been studied by the ZINDO-SOS method. The calculated results show that one- and two-photon absorption properties of metal complexes are strongly influenced by the nature of the ligands (donor end groups and pi linkers) and metal ions as well as by the symmetry of the complexes. The length of the pi-conjugated backbone, the Lewis acidity of the metal ions, and the increase of ligand-to-metal ratio result in a substantial enhancement of the TPA cross sections of metal complexes. Substitution of C=N and N=N for C=C plays an important role in altering the maximum TPA wavelengths and the maximum TPA cross sections of metal complexes. Of them, the C=N substituted metal complexes have relatively large TPA cross sections. Replacing styryl with thienylvinyl makes the one-photon absorption wavelength red shift and at the same time leads to a great decrease of the maximum TPA cross sections of metal complexes. The possible reason is discussed. In the range 500-1250 nm, octupolar metal complexes exhibit intense TPAs and therefore are promising candidates for TPA materials.     

Nonlinear optical and two-photon absorption properties of octupolar tris(bipyridyl)metal complexes

The linear (absorption and emission) and nonlinear optical (NLO) properties of a series of D(3) [(Fe(II), Ru(II), Ni(II), Cu(II), Zn(II)] octupolar metal complexes featuring the 4,4'-bis[(dibutylamino)styryl]-2,2'-bipyridine ligand are reported. Zinc(II), nickel(II), and copper(II) complexes exhibit similar absorption spectra in the visible region (lambda(ILCT) = 474-476 nm) which are assigned to intraligand charge-transfer (ILCT) bands. The quadratic and cubic NLO properties are strongly influenced by the nature of the metallic center. Harmonic light scattering studies at lambda = 1.91 microm reveal that these chromophores display large first hyperpolarizabilities beta(1.91) in the range of (211-340) x 10(-30) esu; replacing the Zn(II) metal ion by Ni(II) or Cu(II) results in a decrease of the static beta(0) coefficient by a factor of 1.5-1.6. Z-scan measurements at 765 and 965 nm reveal relatively large two-photon absorption cross-sections [650 < sigma(2) < 2200 GM], showing that both beta and sigma(2) values can be tuned by simple modification of the metal ion.     

Photochromic bipyridyl metal complexes: Photoregulation of the nonlinear optical and/or luminescent properties

The combination of transition metals and ligands featuring photochromic units is receiving much attention and opens up new perspectives for the design of metal-based photoswitchable molecules. This account summarizes some of our recent works made in the area of photochromic organometallic and coordination compounds, which have been used for the photomodulation of the quadratic non-linear optical (NLO) properties, as well as of the photoregulation of the emission properties of the resulting systems. For this purpose, we have designed new chromophores combining dithienylethene (DTE)-based bipyridine ligands with different metallic fragments (Re^I, Fe^II, Ru^II, Ir^III, Cu^I, Zn^II), giving rise to multi-photochromic metal complexes containing from two to six DTE units, and studied the photocontrol of both NLO and luminescence properties.     

Synthesis, structure, and spectroscopy of phenylacetylenylene rods incorporating meso-substituted dipyrrin ligands

The synthesis, structure, and spectroscopic characterization of a series of phenylacetylenylene rodlike molecules containing dipyrromethene (dipyrrin) ligands are described. The combination of the phenylacetylenylene groups with the porphyrinogenic dipyrrin moieties results in a rich absorption spectroscopy for these compounds, although the fluorescence of the phenylacetylenylene moiety is quenched by presence of the dipyrrin chelator. The Cu(2+) and Fe(3+) complexes of these ligands have been prepared and three of these compounds have been structurally characterized by using single-crystal X-ray diffraction. Unlike other octahedral metal-dipyrrin complexes described to date, one of the iron complexes demonstrates ideal threefold symmetry in the solid-state. The elongated structure and high symmetry of these complexes suggests the use of these meso-substituted phenylacetylenylene ligands as an interesting class of extended, branched molecules for the construction of supramolecular architectures.     

Synthesis and structural characterization of neutral higher-coordinate silicon(IV) complexes with tridentate dianionic chelate ligands

The neutral pentacoordinate silicon(IV) complexes 8 and 9 with an SiO2N3 skeleton and the neutral hexacoordinate silicon(IV) complex 10.1/2 CH3CN with an SiO4N2 skeleton were synthesized, starting from tetra(cyanato-N)silane or tetra(thiocyanato-N)silane. Compounds 8 and 9 contain one tridentate dianionic ligand derived from 4-[(2-hydroxyphenyl)amino]pent-3-en-2-one and two monodentate singly charged cyanato-N or thiocyanato-N ligands bound to the silicon(IV) coordination center, whereas the silicon(IV) center of 10 is coordinated by two of these tridentate dianionic ligands. All compounds were characterized by single-crystal X-ray diffraction and solid-state and solution NMR spectroscopy. To get more information about the stereochemistry of the compounds studied, the experimental investigations were complemented by computational studies.     

Synthesis and nonlinear optical absorption of novel porphyrin-osmium-cluster complexes

Reaction of azido(tetra-p-tolylporphyrinato)indium(III) [TTPInN(3)] and [Os(3)(mu-H)(2)(CO)(10)] in toluene at 80 degrees C overnight gave two major products, complexes 1 and 2. Complex 1 had an axial bridge of "NH", while 2 had an axial bridge of "N" between the porphyrin and osmium cluster moieties. Complex 1 could be converted to 2 when refluxed in toluene. These two novel porphyrin-osmium clusters are the first axially linked porphyrin-metal cluster complexes. UV/Vis spectroscopy revealed the significant ground state electronic perturbation in the capped complex 2, demonstrating that the remarkable electronic interaction of the moieties within the molecule was achieved by this special structural arrangement. In addition, the electrochemistry of 1 and 2 were investigated and their oxidation current voltage curves are similar to those of indium(III)-porphyrins with a metal-metal sigma bond such as [TPPInRe(CO)(5)] (TPP=tetraphenylporphyrin). The two new molecules also exhibit large nonlinear optical absorption at 532 nm with a ns pulse laser and are potential optical limiting materials for sensor protection in the visible region.     

Remarkable Tuning of the Coordination and Photophysical Properties of Lanthanide Ions in a Series of Tetrazole‐Based Complexes

A series of seven new tetrazole‐based ligands (L1, L3–L8) containing terpyridine or bipyridine chromophores suited to the formation of luminescent complexes of lanthanides have been synthesized. All ligands were prepared from the respective carbonitriles by thermal cycloaddition of sodium azide. The crystal structures of the homoleptic terpyridine–tetrazolate complexes [Ln(Li)₂]NHEt₃ (Ln=Nd, Eu, Tb for i=1, 2; Ln=Eu for i=3, 4) and of the monoaquo bypyridine–tetrazolate complex [Eu(H₂O)(L7)₂]NHEt₃ were determined. The tetradentate bipyridine–tetrazolate ligand forms nonhelical complexes that can contain a water molecule coordinated to the metal. Conversely, the pentadentate terpyridine–tetrazolate ligands wrap around the metal, thereby preventing solvent coordination and forming chiral double‐helical complexes similarly to the analogue terpyridine–carboxylate. Proton NMR spectroscopy studies show that the solid‐state structures of these complexes are retained in solution and indicate the kinetic stability of the hydrophobic complexes of terpyridine–tetrazolates. UV spectroscopy results suggest that terpyridine–tetrazolate complexes have a similar stability to their carboxylate analogues, which is sufficient for their isolation in aerobic conditions. The replacement of the carboxylate group with tetrazolate extends the absorption window of the corresponding terpyridine‐ (≈20 nm) and bipyridine‐based (25 nm) complexes towards the visible region (up to 440 nm). Moreover, the substitution of the terpyridine–tetrazolate system with different groups in the ligand series L3–L6 has a very important effect on both absorption spectra and luminescence efficiency of their lanthanide complexes. The tetrazole‐based ligands L1 and L3–L8 sensitize efficiently the luminescent emission of lanthanide ions in the visible and near‐IR regions with quantum yields ranging from 5 to 53 % for Eu^III complexes, 6 to 35 % for Tb^III complexes, and 0.1 to 0.3 % for Nd^III complexes, which is among the highest reported for a neodymium complex. The luminescence efficiency could be related to the energy of the ligand triplet states, which are strongly correlated to the ligand structures.     

Ruthenium complexes of easily accessible tridentate ligands based on the 2-aryl-4,6-bis(2-pyridyl)-s-triazine motif: absorption spectra, luminescence properties, and redox behavior

A family of tridendate ligands 1 a-e, based on the 2-aryl-4,6-di(2-pyridyl)-s-triazine motif, was prepared along with their hetero- and homoleptic Ru(II) complexes 2 a-e ([Ru(tpy)(1 a-e)](2+); tpy=2,2':6',2"-terpyridine) and 3 a-e ([(Ru(1 a-e)(2)](2+)), respectively. The ligands and their complexes were characterized by (1)H NMR spectroscopy, ES-MS, and elemental analysis. Single-crystal X-ray analysis of 2 a and 2 e demonstrated that the triazine core is nearly coplanar with the non-coordinating ring, with dihedral angles of 1.2 and 18.6 degrees, respectively. The redox behavior and electronic absorption and luminescence properties (both at room temperature in liquid acetonitrile and at 77 K in butyronitrile rigid matrix) were investigated. Each species undergoes one oxidation process centered on the metal ion, and several (three for 2 a-e and four for 3 a-e) reduction processes centered on the ligand orbitals. All compounds exhibit intense absorption bands in the UV region, assigned to spin-allowed ligand-centered (LC) transitions, and moderately intense spin-allowed metal-to-ligand charge-transfer (MLCT) absorption bands in the visible region. The compounds exhibit relatively intense emissions, originating from triplet MLCT levels, both at 77 K and at room temperature. The incorporation of triazine rings and the near planarity of the noncoordinating ring increase the luminescence lifetimes of the complexes by lowering the energy of the (3)MLCT state and creating a large energy gap to the dd state.     

Synthesis and metal complexes of chiral c(2)-symmetric diamino-bisoxazoline ligands

A synthetic route to tetradentate chiral N(4) ligands has been developed with the aim to study the potential of corresponding iron and manganese complexes as catalysts for enantioselective epoxidation. These ligands, which contain two oxazoline rings and two trialkylamino groups as coordinating units, are readily prepared in enantiomerically pure form by the reaction of chiral 2-chloromethyloxazolines with achiral N,N'-dimethylethane-1,2-diamine or chiral (R,R)-N,N'-dimethylcyclohexane-1,2-diamine. The ligands derived from N,N'-dimethylethane-1,2-diamine reacted with anhydrous metal halides MnCl(2) and FeCl(2) in a stereoselective manner to give octahedral mononuclear complexes that have the general formula Delta-[(L)MCl(2)]. In contrast, the ligands derived from N,N'-dimethylcyclohexane-1,2-diamine formed complexes with different coordination modes depending on the diastereomer employed: in one case the metal ion was found to be pentacoordinate, in the other case a hexacoordinated complex was observed. The structure of a series of Fe and Mn complexes was determined by X-ray analysis. The coordination chemistry of these ligands was further studied by X-ray and NMR analyses of the diamagnetic isostructural complexes [(L)ZnCl(2)]. Analogous ionic complexes, which were prepared by removing chloride with silver trifluoromethanesulfonate or hexafluoroantimonate, were tested as catalysts for the epoxidation of olefins.     

The first metal (Nd3+, Mn2+, and Pb2+) coordination compounds of 3,5-dinitrotyrosine and their nonlinear optical properties

The reactions of 3,5-dinitrotyrosine (H2DNTY) with Nd(NO3)3.6H2O, Mn(ClO4)2.6H2O, and Pb(OAc)2 afforded three homochiral compounds: discrete [Nd(Hdnty)2(NO3)(H2O)5].3H2O (1) and two- and three-dimensional coordination polymers, [Mn(Hdnty)2] (2) and [Pb(dnty)(0.5 H2O)] (3), respectively. The Nd atom in 1 displays a tricapped trigonal prism and supramolecular weak interactions, such as pi-pi stacking and H-bonds, between amino and nitro groups result in the formation of a three-dimensional network through these interactions. 2 has a two-dimensional square-grid topological net while 3 has the first three-dimensional homochiral ThSi2 net. To the best of our knowledge, these are the first metal coordination compounds with 3,5-dinitrotyrosine. Preliminary second harmonic generation (SHG) investigations indicated that 1 and 2 are SHG active with estimated responses 5 and 6 times larger than that of urea, respectively, while 3 is SHG non-active (obeying the Klainman symmetry requirement). Strong enhancement of their SHG efficiency, compared with H2DNTY, may be due to 1) the addition of a good donor-pi-acceptor organic chromophore into the compound resulting in superior qualities of both inorganic and organic materials and 2) the H-bonds that persist in them. Crystal data: 1: C18H32N7O25Nd, Mr = 890.75 g mol(-1), monoclinic, P2(1), a=7.0179(7), b=27.060(3), c=8.3097(8) A, alpha=gamma=90.00, beta=95.646(2) degrees , V=1570.4(3) A(3), Z=2, rho(calcd)=1.884 Mg m(-3), R(1)=0.0489, wR(2)=0.1223, mu=17.67 mm(-1), S=0.811, Flack value=0.003(13); 2: C(18)H(16)N(6)O(14)Mn, M(r)=595.31 g mol(-1), orthorhombic, P2(1)2(1)2, a=8.4381(14), b=13.639(2), c=19.697(3) A, alpha=beta=gamma=90.00 degrees , V=2266.9(6) A(3), Z=4, rho(calcd)=1.744 Mg m(-3), R(1)=0.0866, wR(2)=0.2030, mu=6.72 mm(-1), S=1.095, Flack value=0.02(6); 3: C(9)H(8)N(3)O(7.5)Pb, M(r)=485.37 g mol(-1), tetragonal, P4(1)2(1)2, a=12.8136(12), b=12.8136(12), c=14.931(2), alpha=beta=gamma=90.00 degrees , V=2451.5(5) A(3), Z=8, rho(calcd)=1.885 Mg m(-3), R(1)=0.0564, wR(2)=0.1323, mu=6.942 mm(-1), S=0.878, Flack value=0.03(2). For space group P4(3)2(1)2: R(1)=0.0672, wR(2)=0.1656, S=1.034, Flack value=1.02(3); this suggests the chosen space group P4(1)2(1)2 is correct.     

Nonlinear optical material of a low-dimensional coordination polymer: Synthesis, structure, NLO and fluorescence properties

Employing unsymmetrical 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,2′-bipyridine as mixed ligands, a new low-dimensional coordination polymer [Zn(MMTA) 2 (2,2′-bipy)] n (MMTA = 2-mercapto-5-methyl-1,3,4-thiadiazole, 2,2′-bipy = 2,2′-bipyridine), has been synthesized under solvothermal condition and characterized by single crystal X-ray diffraction. This compound crys- tallizes in the noncentrosymmetric space group Cc, with cell parameters: a = 8.291(4) , b = 15.483(9) , c = 15.620(6) , = 96.00(5)°, V = 1994.1(2) 3 , and Z = 4. The mixed ligands link the zinc center into a mononuclear unit, which is futher linked by weak C-H···N and C-H···S hydrogen bonds into a three-dimensional noncentrosymmetric framework. The compound exhibits intense photoluminescence and distinct NLO properties at room temperature. The intensity of the green light produced by the powder sample of the compound is about 3.2 times that produced by KDP powder. On the basis of the results of TG analysis, the structure is thermally stable up to ～260 °C.     

Containing‐PMBP N2O2‐donors transition metal(II) complexes: Synthesis,crystal structure,Hirshfeld surface analyses and fluorescence properties

Three newly designed containing‐PMBP N₂O₂‐donors complexes, [Co(L¹)(CH₃OH)₂] ( 1 ), [{Zn(L²)(CH₃OH)(H₂O)}₃] ( 2 ) and [Cu₄(L²)₄]?2CHCl₃ ( 3 ), have been synthesized and structurally characterized using elemental analyses, infrared and UV–visible spectroscopies and single‐crystal X‐ray diffraction. X‐ray crystal structure determinations revealed that 1 consists of one Co(II) atom, one completely deprotonated (L¹)^2? unit and two coordinated methanol molecules. Complex 2 consists of three Zn(II) atoms, three completely deprotonated (L²)^2? units, three coordinated methanol molecules and three coordinated water molecules. However, 3 includes four Cu(II) atoms, four completely deprotonated (L²)^2? units and two crystallization chloroform molecules. The Co(II) and Zn(II) atoms in the structures of 1 and 2 adopt slightly distorted octahedral geometries. While, Cu(II) atoms in 3 can be best described as adopting slightly distorted square planar geometries. Complex 2 is a novel structure, and the ratio of H₂L² to Zn(II) atom is 3:3. In addition, two‐, three‐ and three‐dimensional supramolecular structures were constructed for 1 , 2 and 3 . Most importantly, Hirshfeld surface analysis of 1 , 2 and 3 was conducted and fluorescence properties were investigated.     

Atypical and Asymmetric 1,3-P,N Ligands: Synthesis,Coordination and Catalytic Performance of Cycloiminophosphanes

Novel seven-membered cyclic imine-based 1,3-P,N ligands were obtained by capturing a Beckmann nitrilium ion intermediate generated in situ from cyclohexanone with benzotriazole, and then displacing it by a secondary phosphane under triflic acid promotion. These “cycloiminophosphanes” possess flexible non-isomerizable tetrahydroazepine rings with a high basicity; this sets them apart from previously reported iminophophanes. The donor strength of the ligands was investigated by using their P-κ¹- and P,N-κ²-tungsten(0) carbonyl complexes, by determining the IR frequency of the trans-CO ligands. Complexes with [RhCp*Cl₂]₂ demonstrated the hemilability of the ligands, giving a dynamic equilibrium of κ¹ and κ² species; treatment with AgOTf gives full conversion to the κ² complex. The potential for catalysis was shown in the Ru^II-catalyzed, solvent-free hydration of benzonitrile and the Ru^II- and Ir^I-catalyzed transfer hydrogenation of cyclohexanone in isopropanol. Finally, to enable access to asymmetric catalysts, chiral cycloiminophosphanes were prepared from l -menthone, as well as their P,N-κ²-Rh^III and a P-κ¹-Ru^II complexes.     

Synthesis, structural features, absorption spectra, redox behaviour and luminescence properties of ruthenium(ii) rack-type dinuclear complexes with ditopic, hydrazone-based ligands

The isomeric bis(tridentate) hydrazone ligand strands 1 a-c react with [Ru(terpy)Cl3] (terpy=2,2':6',2'-terpyridine) to give dinuclear rack-type compounds 2 a-c, which were characterised by several techniques, including X-ray crystallography and NMR methods. The absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in rigid matrix at 77 K) of the ligand strands 1 a-c and of the metal complexes 2 a-c have been studied. Compounds 1 a-c exhibit absorption spectra dominated by intense pi-pi* bands, which, in the case of 1 b and 1 c, extend within the visible region, while the absorption spectra of the rack-type complexes 2 a-c show intense bands both the in the UV region, due to spin-allowed ligand-centred (LC) transitions, and in the visible, due to spin-allowed metal-to-ligand charge-transfer (MLCT) transitions. The energy position of these bands strongly depends on the ligand strand: in the case of 2 a, the lowest energy MLCT band is around 470 nm, while in 2 b and 2 c, it lies beyond 600 nm. Ligands 1 a-c undergo oxidation processes that involve orbitals based mainly on the CH3--N--N== fragments. The complexes 2 a-c undergo reversible metal-centred oxidation, while reductions involve the hydrazone-based ligands: in 2 b and 2 c, the bridging ligand is reduced twice and in 2 a once before reduction of the peripheral terpy ligands takes place. Ligands 1 a-c exhibit luminescence from the lowest-lying 1pi-pi* level. Only for complex 2 a does emission occur; this may be attributed to a 3MLCT state involving the bridging ligand. Taken together, the results clearly indicate that the structural variations introduced translate into interesting differences in the spectroscopic, luminescence and redox properties of the ligand strands as well as of the rack-type metal complexes.     

Chiral AuI- and AuIII-Isothiourea Complexes: Synthesis,Characterization and Application

During an investigation into the potential union of Lewis basic isothiourea organocatalysis and gold catalysis, the formation of gold-isothiourea complexes was observed. These novel gold complexes were formed in high yield and were found to be air- and moisture stable. A series of neutral and cationic chiral gold(I) and gold(III) complexes bearing enantiopure isothiourea ligands was therefore synthesized and fully characterized. The steric and electronic properties of the isothiourea ligands was assessed through calculation of their percent buried volume and the synthesis and analysis of novel iridium(I)-isothiourea carbonyl complexes. The novel gold(I)- and gold(III)-isothiourea complexes have been applied in preliminary catalytic and biological studies, and display promising preliminary levels of catalytic activity and potency towards cancerous cell lines and clinically relevant enzymes.     

Synthesis of multi-1,10-phenanthroline ligands with 1,3-phenylene linkers and their lithium complexes

The synthesis of two multisite ligands containing four and five 1,10-phenanthroline (phen) chelates in line, respectively, is presented. The connectors are 1,3-phenylene linkers. The two ligands were prepared following multistep procedures, the two key reactions being the Suzuki coupling reaction between aromatic nuclei and the nucleophilic addition of aryllithium derivatives onto a phen fragment. The coordination chemistry of both ligands with Li+ ions was very clean and selective, whereas their reaction with copper(I) led to intractable mixtures of insoluble complexes. The tetraphen and the pentaphen compounds afforded almost quantitatively the four- and five-lithium double-stranded helical complexes, respectively. The helical systems are probably highly wound, as indicated by NMR measurements. The pronounced strain of the 5-Li+ complex is reflected by the easy loss of a lithium cation, as shown by electrospray mass spectrometry.     

Synthesis of novel rod-shaped and star-shaped fluorescent phosphane oxides--nonlinear optical properties and photophysical properties

The design of a new class of fluorophores is presented. Some push-pull chromophores (D-pi-A) containing polyphenylethynyl units and a phosphane oxide moiety were efficiently prepared from common intermediates. Straightforward syntheses gave novel one-armed, rod-shaped and three-armed, star-shaped fluorophores. The optical properties of the resulting star-shaped derivatives were evaluated, showed high fluorescence quantum yields, and their excitation induces very efficient charge redistribution. Moreover, thanks to their push-pull character, the molecules exhibited significant second-order NLO properties with good transparency, up to 67x10(-30) esu at 1907 nm, with an absorption lambdamax at 369 nm. The effect of the donor group and of the number of phenylethynyl arms have been studied in this work.     

Structural variation from 1D to 3D: effects of ligands and solvents on the construction of lead(II)-organic coordination polymers

A series of Pb(II) coordination polymers [Pb(ndc)(dpp)] (1), [Pb(ndc)(ptcp)].0.5 H2O (2), [Pb(ndc)(dppz)] (3), [Pb(ndc)(tcpn)(2)] (4), [Pb2(ndc)2(tcpp)] (5), [Pb(Hndc)2].H2O (6), [Pb(ndc)(dma)] (7), [Pb(bdc)(dma)] (8), [Pb(trans-chdc)(H2O)] (9), and [Pb2(cis-chdc)2].NH(CH3)2 (10), where ndc=1,4-naphthalenedicarboxylate, dpp=4,7-diphenyl-1,10-phenanthroline, ptcp=2-phenyl-1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene, dppz=dipyrido[3,2-a:2',3'-c]phenazine, tcpn=2-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)naphthol, tcpp=4-(1H-1,3,7,8-tetraazacyclopenta[l]phenanthren-2-yl)phenol, dma=N,N-dimethylacetamide, bdc=1,4-benzenedicarboxylate, and chdc=1,4-cyclohexanedicarboxylate, have been synthesized from a hydrothermal or solvothermal reaction system by varying the ligands or the solvents. Compounds 1-5 crystallize with an N-donor chelating ligand and an aromatic dicarboxylate linker. Compounds 1-4 are 1D polymers with different pi-pi stacking interactions, whereas compound 5 consists of 2D layers. The structures of compounds 7, 8, and 10 are 3D frameworks formed by connection of the Pb(II) centers by organic acid ligands. Compound 7 is chiral although the ndc ligand is achiral, while the framework of 8 is a typical 3D (3,4)-connected net. Compound 10 is the first example of Pb(II) wheel cluster [Pb(8)O(8)] units bridged by carboxylate groups. Compound 6 contains 1D chains which are further extended to a 3D structure by pi-pi interactions. Compound 9 consists of a 2D network constructed by Pb(II) centers and trans-chdc ligands. The structural differences between 7 and 8 and between 9 and 10 indicate the importance of solvents for framework formation of the coordination polymers. By varying the solvent the cis and trans conformations of H(2)chdc in 9 and 10 were separated completely. The photoluminescence and nonlinear optical properties of the coordination polymers have also been investigated.