Pendant Pyridyl Groups Research Articles

Nickel(II) and Palladium(II) Complexes with η5:κ1(N)-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group.

A series of C- and B-substituted nido-carborane derivatives with a pendant pyridyl group was prepared. The synthesized compounds were used as ligands in the complexation reactions with bis(triphenylphosphine)nickel(II) and palladium(II) chlorides to give six new metallacomplexes with unusual η5:κ1(N)-coordination of the metal center. The single crystal structures of 1-(NC5H4-2'-S)-1,2-C2B10H11, 1-(NC5H4-2'-CH2S)-1,2-C2B10H11, Cs [7-(NC5H4-2'-CH2S)-7,8-C2B9H11] closo- and nido-carboranes and 3-Ph3P-3-(4(7)-NC5H4-2'-S)-closo-3,1,2-NiC2B9H10 and 3-Ph3P-3-(4(7)-NC5H4-2'-CH2S)-closo-3,1,2-NiC2B9H10 metallacarboranes were determined using single crystal X-ray diffraction.

Crystal structure and Hirshfeld surface analysis of cyclo-tetra-bromido-1κ2Br,3κ2Br-tetra-kis-(μ2-2-{[(pyridin-2-yl)meth-yl]amino}-ethane-1-thiol-ato-κ3N,S:S)tetra-mercury(II).

The macrometallacyclic title compound, [Hg4Br4(C8H11N2S)4] or [((HgL 2)(HgBr2))2] (1) where HL = 2-{[(pyridin-2-yl)meth-yl]amino}-ethane-1-thiol, was prepared and structurally characterized. The Hg2+ complex crystallizes in the P21/c space group. The centrosymmetric Hg4S4 metallacycle is constructed from metal ions with alternating distorted tetra-hedral Br2S2 and distorted seesaw N2S2 primary coordination environments with pendant pyridyl groups. The backfolded extended chair metallacycle conformation suggests inter-actions between each of the bis-chelated mercury atoms and Br atoms lying above and below the central Hg2S4 plane. Supra-molecular inter-actions in 1 include a fourfold aryl embrace and potential hydrogen bonds with bromine as the acceptor. Hirshfeld surface analysis indicates that H⋯H (51.7%), Br⋯H/H⋯Br (23.0%) and C⋯H/H⋯C (9.5%) inter-actions are dominant.

Ligand-Directed Metalation of a Gold Pyrazolate Cluster.

Solid "[AuL]" (HL = 3-[pyrid-2-yl]-5-tertbutyl-1H-pyrazole) can be crystallized as cyclic [Au3(μ-L)3] and [Au4(μ-L)4] clusters from different solvents. The crystalline tetramer contains a square Au4 core with an HT:TH:TH:HT arrangement of ligand substituents, which preorganizes the cluster to chelate to additional metal ions via its pendant pyridyl groups. The addition of 0.5 equiv of AgBF4 to [AuL] yields [Ag2Au4(μ3-L)4][BF4]2, where two edges of the Au4 square are spanned by Ag+ ions via metallophilic Ag···Au contacts. Treatment of [AuL] with [Cu(NCMe)4]PF6 affords the metalloligand helicate [Cu2Au2(μ-L)4][PF6]2, via oxidation of the copper and partial fragmentation of the cluster.

Triazolyl- vs Pyridyl-Functionalized N-Heterocyclic Carbene Complexes: Impact of the Pendant N-Donor Ligand on Intramolecular C-C Bond Formation.

Organometallic Rh(Cp*) (Cp* = η5-pentamethylcyclopentadienyl) complexes with monodentate N-heterocyclic carbene (NHC) ligands bearing a pendant anthracenyl substituent have been shown to undergo intramolecular C-C coupling reactions. Herein, two bidentate NHC ligands substituted with pyridyl or triazolyl donor groups were prepared along with the corresponding MII/III (M = RuII, OsII, RhIII, IrIII) complexes. While the Rh(Cp*) complex featuring an NHC-triazole bidentate ligand underwent the equivalent reaction as the monodentate Rh(NHC) complex, i.e., it formed a polydentate ligand, the pyridyl-pendant derivative was unequivocally shown to be unreactive. This contrasting behavior was further investigated by density functional theory (DFT) calculations that highlighted significant differences between the two types of Rh(III) complexes with pendant pyridyl or triazolyl N-coordinating groups. Modeling of the reaction pathways suggests that the initial formation of a dicationic Rh(III) species is unfavorable and that the internal ligand transformation proceeds first by dissociation of the coordinated N atom of the pendant group from the Rh center. After the formation of a neutral η4-fulvene ligand via combined proton/single electron transfer, a cycloaddition occurs between the exo-ene bond of fulvene and the 9' and 10' positions on the pendant anthracenyl group. The resulting experimental UV-visible spectrum recorded in methanol of the polydentate triazolyl-based Rh species revealed the loss of the vibronic coupling typically associated with an anthracenyl functional group. Moreover, TD-DFT modeling indicates the presence of an equilibrium process whereby the N-coordination of the pendant triazolyl group to the RhIII center appears to be highly labile. Charge decomposition analysis (CDA) of the DFT-modeled species with the dissociated triazolyl group revealed a pseudo-η3-allylic interaction between the π-type MOs of the transformed anthracenyl group and the RhIII center; thus, the singly attached chelating ligand is classified as having rare nonadenticity.

Steric Effect of a Capping Ligand on the Formation of Supramolecular Coordination Networks of Ni(II): Solid-State Entrapment of Cyclic Water Dimer.

Supramolecular dimer of water is the simplest of the small water clusters [(H2O)n, n = 2–10]. During the course of our work on supramolecular coordination networks of three-component systems (divalent metal ion, tridentate capping ligand, and ditopic carboxylate linker), a cyclic water dimer is found to be entrapped in the network of [Ni2(6-Mebpta)2(adc)2]·2H2O (1) (6-Mebpta = 2-methyl-N-((6-methylpyridin-2-yl)methyl)-N-(pyridin-2-ylmethyl)propan-2-amine and adc = acetylenedicarboxylate). Based on the single-crystal structure of 1, the water dimer plays an important role in connecting the bis(adc) bridged dinickel synthons to form a one-dimensional (1D) supramolecular network. To emphasize the role of 6-Mebpta in the judicious choice of components for 1, one simple modification to it by having another methyl group in the second pendant pyridyl group to make 6,6′-Me2bpta (2-methyl-N,N-bis((6-methylpyridin-2-yl)methyl)propan-2-amine) did not allow the formation of any water cluster in [Ni(6,6′-Me2bpta)(adc)(H2O)]·H2O (2), where a different coordination environment around Ni(II) is also observed. Further quantification of the difference in supramolecular interactions observed in 1 and 2 has been assessed by Hirshfeld surface analysis. Both 1 and 2 are obtained in good yields at room temperature (methanol as solvent) and are further characterized by elemental analysis, Fourier transform infrared (FTIR) and Raman spectroscopy, powder X-ray diffraction, and thermogravimetric analysis.

Probing into the electrochemistry of four nickel(II) and cobalt(II) complexes with azadiphosphine ligands (PNP) and their catalysis on proton reduction

In this work, four complexes of Co(II) and Ni(II), [Co(L1)2(CH3CN)](ClO4)2 (1), [Ni(L1)2](ClO4)2 (2), [Co(L2)2(CH3CN)](ClO4)2 (3) and [Ni(L2)2](ClO4)2 (4) were synthesized by reacting the perchlorate hydrate of M(II) (M = Co and Ni) with the ligands, Ph2PN(cyclohexyl)PPh2 (L1) and Ph2PN(pyridin-2-ylmethyl)PPh2 (L2), respectively. The complexes were fully characterized, and their absolute structures were determined using X-ray single crystallographic analysis. The cobalt complexes (1 and 3) exhibited two reductions in acetonitrile, one reversible reduction at about −0.65 V and the other at about −2.0 V at which catalytic reduction of proton was observed. The two reductions were assigned to Co(II) → Co(I) and Co(I) → Co(0) processes, respectively. The reduction of Ni(II) → Ni(I) was negatively shifted by about 300 mV compared to the cobalt analogues and the process showed two closely located reversible reductions due to geometric isomerization between the square planar (Sp) and tetrahedral (Td) geometries, of which the Td isomer was first reduced due to the lower energy level of its frontier orbitals. The second reduction of the Ni(II) complexes (2 and 4) was invisible in the potential range examined. Upon addition of acetic acid, it shifted positively by over 300 mV and showed catalysis on proton reduction. The shift was attributed to proton-coupled electron transfer (PCET) effect which was further enhanced by the pendant pyridyl group in ligand L2. The nickel complexes showed much higher activity than cobalt analogues in the catalysis on proton reduction and the pendant base group could synergistically enhance the activity of the complex (4).

Synthesis, structural characterization and antiproliferative potential of copper 4′-phenyl-terpyridine complexes constructed from building block reaction

Reactions between 4′-phenyl-terpyridine (L0) and Cu(II) nitrate resulted in the formation of complex [Cu(NO3)2L0](H2O) (1). Further reaction of this compound as a building block with sodium citrate, sodium benzoic and a tetra-methylpyridyl functionalized Cyclam ligand led to the compounds as [Cu(L0)2](NO3)2(H2O)1.5 (2), [Cu(ONO2)L0(OCOC6H5)](1.5H2O)(0.5CH3CN) (3) and [Cu2(NO3)2(L0)2L](NO3)2(H2O)2 (4), respectively. The four compounds were characterized by Elemental analysis, IR, UV–vis, and single crystal X-ray diffraction. Moreover, the thermal stability of 1 and 4 were determined by TG-DTA. In 1, 3 and 4, Cu ion is coordinated with one terpyridine motif and two oxygen atoms or one oxygen and one nitrogen atoms from two auxiliary ligands, resulting in a distorted CuN3O2 or CuN4O tetragonal pyramid geometry, while 2 is a sandwich structure, forming a regular-octahedron CuN6 coordination structure. The functionalized cyclam ligand L shows only one conformation with two pendant pyridyl groups coordinating to two copper ions and the other two being free in a para-mode conformation. The separation between the two copper ions in one molecule is 14.9398 (9) Å. Three human cancer cell lines were used for antiproliferative potential: human lung cancer cell line (A549), human colon cancer cell line (HCT-8) and human breast cancer cell line (MCF-7). The results have shown that these copper compounds have good inhibitory effects on cancer cells, which are better than that of the commonly used clinical drug cisplatin.

Efficient fluorescent chemosensing of iodide based on a cationic meso-tetraarylporphyrin in pure water

The new tetracationic and highly luminescent triflate salt of 5,10,15,20-tetra(4-benzylpyridinium)-21H,23H-porphyrin, 1.OTf was designed and studied as a chemosensor for iodide in pure water. Under optimal conditions, the addition of inorganic anions and acetate as sodium salts to 1.OTf quench its red fluorescence with a very pronounced affinity toward iodide (K1.I− = 1.9(±0.08) x 104 M-1) accompanied by complete quenching of its emission (KSV = 1.1(±0.1) x 105) in a micromolar concentration range (0-50 μM). A rapid and direct analytical response of 1.OTf by addition of I- ions was observed in a wide range of pH (5.0–8.0) with a detection limit of 180 nmol L-1 at neutral pH and good selectivity over other biological and more basic anions such as pyrophosphate, chloride, fluoride and phosphate. The optical change by addition of iodide is attributed to a strong ion-pair binding with simultaneous formation of efficient hydrogen bonding C–H … I- interactions, these contacts are supported by 1H NMR experiments. The efficient binding and fluorescence detection is attributed to a very high positive charge of monomeric specie of 1 in combination with strong acidification of C–H donors by quaternization of pendant pyridyl groups. On the other hand, addition of bromide, common interfering anion, shows a modest spectral change but lower than those observed for iodide. On basis of multiple spectroscopic titration experiments (1H NMR, UV–vis, fluorescence), Job´s plot, crystal structure of the bromide salt of 1 and fluorescence lifetime measurements, a photoinduced electron transfer quenching mechanism with simultaneous sensor-iodide complexation both in the excited and the ground-state is proposed. From theoretical DFT studies, the binding mode of this chemosensor with iodide is markedly ionic interaction, energy calculated in 402.8 kcal/mol. The proposed method is direct, fast, accurate and of low cost for the determination of iodide ions in pure water.

A Series of Lithium Pyridyl Phenolate Complexes with a Pendant Pyridyl Group for Electron-Injection Layers in Organic Light-Emitting Devices.

We report a new series of lithium pyridyl phenolate complexes with a pendant pyridyl group, Li2BPP, Li3BPP, and Li4BPP, in which the pendant pyridines are substituted at the 2-, 3-, and 4-positions, respectively. The most important difference between these complexes is their molecular planarity; Li3BPP and Li4BPP adopt twisted bipyridine structures, whereas Li2BPP adopts a planar structure owing to the steric hindrance and chelating effect of bipyridine on the Li core. The planar structure leads to crystallization through π-π stacking interactions, and the small differences in the molecular structures of the pendant pyridine rings cause drastic differences in the physical properties of thin solid films of these complexes. We applied these complexes as electron-injection layers (EILs) in Ir(ppy)3-based organic light-emitting devices. When thin EILs were used, Li3BPP and Li4BPP afforded lower driving voltages than Li2BPP; the order of the driving voltages followed the order of their electron affinity values. Moreover, the dependence of driving voltage on the EIL thickness was investigated for each complex. Among the three LiBPP derivatives, Li2BPP-based devices showed almost negligible EIL thickness dependence, which may be attributable to the high crystallinity of Li2BPP. All LiBPP-based devices also showed higher stability than conventional 8-quinolinolato lithium-based devices.

Covalently Assembled Monolayers of Homo- and Heteroleptic FeII -Terpyridyl Complexes on SiOx and ITO-Coated Glass Substrates: An Experimental and Theoretical Study.

Well-defined FeII -terpyridyl monolayers were fabricated on SiOx and conductive ITO-coated glass substrates through covalent-bond formation between the metallo-organic complexes and a preassembled coupling layer. Three different homo- and heteroleptic complexes with terminal pyridyl, amine, and phenyl groups were tested. All the films were found to be densely packed and homogeneous, and consist of molecules standing upright. They exhibited high thermal (up to ≈220 °C) and temporal (up to 5 h at 100 °C) stability. The UV/Vis spectra of the monolayers showed pronounced metal-to-ligand charge-transfer bands with a significant redshift compared with the solution spectra of the metallo-ligands with a pendant pyridyl group quaternized with the coupling layer, whereas the shift was significantly smaller when the coupling layer was bonded to the primary amine (-NH2 ) group of the complex. Cyclic voltammograms of the monolayers showed reversible, one-electron redox behavior and suggested strong electronic coupling between the confined molecules and the underlying substrate. Analysis of the electrochemistry data allowed us to estimate the charge-transfer rate constant between the metal center and the substrate. Additionally, detailed quantum-chemical calculations were performed to support and rationalize the experimentally observed photophysical properties of the FeII -terpyridyl complexes both in the solution state and when bound to a SiOx -based substrate.

Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal-Ligand Induced Catalytic Dehydrogenation of Amines.

Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such Npyr ⋅⋅⋅H-N interactions are demonstrated by X-ray diffraction analysis, 1 H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand-metal cooperative substrate activation.

Chiral Ruthenium(II) Complexes as Supramolecular Building Blocks for Heterometallic Self-Assembly.

A series of enantiopure ruthenium(II) polypyridyl complexes are reported that feature pendant pyridyl groups suitable for building larger self-assembled structures. The complexes are characterized in detail in solution using NMR spectroscopy, cyclic voltammetry, and photophysical methods and in the solid state using single-crystal X-ray crystallography. The complexes are luminescent, displaying long excited-state lifetimes that are quenched when the pendant pyridyl groups are protonated. Reaction with cadmium(II) ions results in the formation of a mixed-metal one-dimensional coordination polymer, which was characterized by single-crystal X-ray crystallography.

Rare earth metal bis(silylamide) complexes bearing pyridyl-functionalized indenyl ligand: Synthesis, structure and performance in the living polymerization ofl-lactide and rac-lactide

Amine elimination of rare earth tris(silylamide) complexes Ln[N(SiHMe(2))(2)](3)(THF)(2) (Ln = La, Sm, Er, Lu) with 1 equiv. of the pyridyl-functionalized indenyl ligand C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α afforded a series of neutral mono-indenyl-ligated rare earth metal bis(silylamide) complexes (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)Ln[N(SiHMe(2))(2)](2) (Ln = La (1), Sm (2), Er (3), Lu (4)) in 83-87% isolated yields. Reaction of La[N(SiHMe(2))(2)](3)(THF)(2) with 2 equivalents of C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α provided the neutral bis(indenyl) lanthanum mono(silylamide) complex (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)(2)LaN(SiHMe(2))(2) (5). These complexes were characterized by elemental analysis, FT-IR and NMR (except for 3 for the strong paramagnetic property of the central metal). X-ray single crystal structural diffraction showed that 1-4 are isostructural and the central metals are four-coordinated by one indenyl ring, one nitrogen atom from the pendant pyridyl group, and two amide groups to form a distorted tetrahedral geometry; while the central metal in 5 is five-coordinated by two indenyl rings, two nitrogen atoms from the pendant pyridyl groups, and one amide group to adopt a distorted pyramidal geometry, if the indenyl ring is regarded as occupying an independent vertex. The monoanionic pyridyl-functionalized indenyl ligand is bonded to the central metal in η(5)/κ(1) constrained geometry configuration (CGC) mode. 1-4 are highly active for the ring-opening polymerization of L-lactide and rac-lactide. In the presence of 2 equivalents of benzyl alcohol, 1 shows high activity toward L-lactide and rac-lactide in a living fashion.

An Original Electrochemical Pathway for the Synthesis of Porphyrin Oligomers

An electrosynthesis process has allowed the formation of four oligomers, containing three, four, or five macrocycles. This method is based on the nucleophilic attack of porphyrins substituted by several pendant pyridyl groups to the electrogenerated radical cation of zinc β-octaethylporphyrin (ZnOEP), according to an ECEC processes. Thus, a control of the number of macrocycles and of the geometry of the oligomers can be performed. These new compounds have been characterized by HRMS as well as (1)H NMR, UV/Vis, and fluorescence spectroscopy, and electrochemistry. The results show a strong influence of the pyridinium spacers on the macrocycles.

In situ selective N-alkylation of pendant pyridyl functionality in mixed-valence copper complexes with methanol and copper(ii) bromide

The reactions of CuBr(2) with pyridyl 2,2':6',2''-terpyridine ligands in methanol yielded four copper complexes under solvothermal conditions. The self-assembly processes were accompanied by designing bitopic precursor ligands and increasing the stoichiometric metal-ligand ratio. In the four resulting complexes, the pendant pyridyl groups of pyridylterpyridine were selectively in situ N-methylated and yielded the 4'-(N-methylpyridinium)-2,2':6',2''-terpyridine cations, including the 2-position pyridyl group which is difficult to be N-alkylated due to the steric problem. Partial divalent copper atoms were reduced to cuprous ones in the solvothermal reactions, which made the mixed-valence copper atoms coexist in each compound. The mixed-valence complexes have a varied dimensionality (from 2D to 0D) and the Cu(I)Br cluster, which can be controlled by changing the metal-ligand ratio. Theoretical studies show that the nucleophilic attack of the nitrogen atom in the pendant pyridyl is more facile than others of terpyridine. A possible mechanism was also proposed.

Tuning the Excited State of Photoactive Building Blocks for Metal‐Templated Self‐Assembly

The reaction of 2,2':4,4'':4',4'''-quaterpyridyl (qtpy), with d(6) ruthenium(II) (Ru(II) ), and rhenium(I) (Re(I) ) metal centers has been investigated. The pendant pyridyl groups on the products have also been methylated to produce a second series of complexes containing coordinated Meqtpy(2+). The absorption spectra of the complexes are dominated by intraligand and charge-transfer bands. The ruthenium(II) complexes display broad unstructured luminescence consistent with emission from a Ru(d)→diimine(π*) manifold in acetonitrile solutions. In aqueous solutions, their emissions are weaker and the lifetimes are shorter. This effect is particularly acute for complexes incorporating coordinated dipyridylpyrazine, dppz, ligands. Although the emission of the ruthenium(II) complexes containing Meqtpy(2+) is generally shorter than their qtpy analogs, it is notable that solvent-dependent effects are much less intense. The rhenium(I) complexes also display broad unstructured luminescence but, compared with the ruthenium(II) systems, they have a relatively short lifetime in acetonitrile. Electrochemical studies reveal that all of the Ru(II) complexes display chemically reversible metal-based oxidations. Re(I) complexes only display irreversible metal-based oxidations. In most cases, the reduction processes were not fully chemically reversible. The electrochemical and optical studies reveal that the nature of the lowest excited state of these complexes--particularly, the systems incorporating dppz--is highly dependent on the nature of the coordinated ligands. Calculations indicate that, although the excited state of most of the complexes is centered on the qtpy or Meqtpy(2+) ligands, the excited state of the complexes containing dppz ligands is switched away from the dppz by qtpy methylation. A crystallographic study on one of the dicationic ruthenium(II) structures reveals that it forms an inclusion complex with benzene.

ROMP polymer-based antimicrobial films repeatedly chargeable with silver ions

Two norbornene derivatives bearing a pendant pyridyl group were prepared: the 3-(pyridin-2-yl)propyl ester of 5-norbornene- endo-2-carboxylic acid ( 1) and N-(pyridin-2-ylmethyl)-5-norbornene- endo-2,3-dicarboxyimide ( 2). Both of these compounds produced high yields of ROMP polymers, poly( 1) and poly( 2), with the 2nd generation Grubbs catalyst. When Ag + ions were added to these polymer solutions, the polymer–Ag + composites, poly( 1-Ag) and poly( 2-Ag), were formed quantitatively. Poly( 2) and poly( 2-Ag) produced films from their DMF solutions, and the latter film showed strong antimicrobial properties against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Alternatively, when the film of poly( 2) was immersed in a solution of Ag +, it was able to trap the ion to give a surface-modified film [Ag/poly( 2)]. The antimicrobial efficacy of [Ag/poly( 2)] was the same as that of films made of poly( 2-Ag), which indicated that the solid-state reaction of the film surfaces toward Ag + ions in solution was quantitative. When the [Ag/poly( 2)] film lost its biocidal effect after repeated use, the Ag + ions could be reloaded by immersing the film in a silver ion solution, which fully restored original activity.

Single, double and triple deprotonation of a β-diketimine bearing pendant pyridyl group and the corresponding rare-earth metal complexes

A new beta-diketimine bearing the pendant pyridyl group, CH(3)C(2,6-((i)Pr)(2)C(6)H(3)NH)CHC(CH(3))(NCH(2)-C(5)NH(4)) (L1), was synthesized. The reaction of L1 with one equivalent of Sc(CH(2)SiMe(3))(3)(THF)(2) at room temperature gave a singly deprotonated product (L1-H)Sc(CH(2)SiMe(3))(2) (1). Y(CH(2)SiMe(3))(3)(THF)(2) under the same conditions led to the unexpected dimer [(L1-H(3))Y(THF)](2) (2), in which the ligand precursor L1 was triply deprotonated. The reaction of L1 with Y(CH(2)SiMe(3))(3)(THF)(2) at -35 degrees C provided a mixture of singly deprotonated product (L1-H)Y(CH(2)SiMe(3))(2) (3) and doubly deprotonated product (L1-H(2))Y(CH(2)SiMe(3))(THF)(2) (4). The reactions of L1 with Ln[N(SiMe(3))(2)](3) gave only singly deprotonated products (L1-H)Ln[N(SiMe(3))(2)](2) (5: Ln = Y; 6: Ln = La). The complexes 1, 2 and 4-6 have been characterized by single-crystal X-ray diffraction.

Zinc(II) and mercury(II) coordination architectures with two pyridyl/benzimidazol-1-yl-based ligands: Crystal structures and photoluminescent properties

In our efforts to investigate the relationships between the structures of ligands and their complexes, two structurally related ligands, 1-(2-pyridylmethyl)-1 H-benzimidazole ( L 1 ) and 1-(4-pyridylmethyl)-1 H-benzimidazole ( L 2 ), and their four complexes, [Zn( L 1 ) 2Cl 2] ( 1), [Hg( L 1 )Br 2] ∞ ( 2), {[Zn( L 2 )Cl 2](CH 3CN)} ∞ ( 3) and [Hg( L 2 )Br 2] 2(CH 3CN) 2 ( 4) were synthesized and structurally characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction analysis. Structural analyses show that 1 has a mononuclear structure, and 2 and 3 both take 1D structure. While 4 takes a dinuclear structure. 1, 2 and 4 were further linked into higher-dimensional supramolecular networks by weak interactions, such as C–H⋯Cl and C–H⋯Br H-bonding, C–H⋯π, and π⋯π stacking interactions. The structural differences of 1– 4 may be attributed to the difference of the spatial positions of the terminal N donor atoms in the pendant pyridyl groups in L 1 and L 2 , in which the pyridine rings may act as the directing group for coordination and the benzimidazole rings act as the directing group for π⋯π stacking and C–H⋯π interactions. The luminescent properties of the corresponding complexes and ligands have been further investigated.

A Double-Helical Silver(I) Coordination Polymer Based on 1-(4-pyridylmethyl)-1H-benzotriazole: Synthesis, Crystal Structure and Luminescent Property

The reaction of AgNO3 with 1-(4-pyridylmethyl)-1H-benzotriazole (4-pbt) afforded a photoluminescent one- dimensional (1D) double-helical coordination polymer {(Ag(4-pbt))(NO3)}� (1) formed by interchain C-H � su- pramolecular interactions of the single-helical chains. Adjacent 1D double-helical motifs aforementioned were assembled into different two-dimensional (2D) sheets from the different crystallographic directions, respectively, by the co-effects of Ag O, C-H···O H-bonding,  stacking, and C H supramolecular interactions. In comparision with the previous finding, the present work reveals that the N-donor spatial position of pendant pyridyl group in such benzotriazol-1-yl- based pyridyl ligands plays an important role on the final structures of relevant coordination complexes.