Syntheses and Characterization of Zinc,Cadmium, and Mercury(II) Complexes with N‐(2‐pyridyl)carbonylaniline (L), X‐ray Crystal Structure of [Hg(L)(SCN)2]

The reaction of N‐(2‐pyridyl)carbonylaniline (L) with Zn(NO₃)₂, CdCl₂, and Hg(SCN)₂ gives the following complexes: [Zn(L)₂](NO₃)₂, [Cd(L)₂Cl₂], and [Hg(L)(SCN)₂]. The new complexes were characterized by elemental analyses and IR‐, ¹H‐, ¹³C‐NMR spectroscopy. The crystal structure of the [Hg(L)(SCN)₂] was determined by single crystal X‐ray analysis. The monomeric complex is built up of a Hg(SCN)₂ unit with one N‐(2‐pyridyl)carbonylaniline (L) ligand coordinated to the Hg atom via the ring pyridinic nitrogen atom and the carbonyl oxygen atom forming a five‐membered chelate ring. The Hg atom has a distorted tetrahedral environment. There is π‐π stacking interaction between the parallel aromatic rings belonging to adjacent chain as planar species in which the mean molecular planes are close to parallel and separated by a distance of ～ 3.5Å, close to that of the planes in graphite. The coordinated N‐(2‐pyridyl)carbonylaniline (L) molecule is involved in hydrogen bonding acting as hydrogen‐bond donors with S and N atoms from SCN^— ligand as potential hydrogen‐bond acceptors. There is a shortest intermolecular contacts between the S and N atoms. The hydrogen bonding and shortest intermolecular contacts between the S and N atoms yields infinite chains parallel to the crystallographic vector c. Each molecule is bonded to two neighbors.     

Copper(II) Complexes with N‐(9‐anthracenyl)‐N′‐(3‐pyridyl)urea (L) and a Derivative of L: Synthesis,Structure, and Fluorescent Properties

Three copper(II) complexes, [Cu₂(OAc)₄L₂] · 2CH₃OH ( 1 ), [CuBr₂L′₂(CH₃OH)] · CH₃OH ( 2a ), and [CuBr₂L′₂(DMSO)] · 0.5CH₃OH ( 2b ) {L = N‐(9‐anthracenyl)‐N′‐(3‐pyridyl)urea and L′ = N‐[10‐(10‐methoxy‐anthronyl)]‐N′‐(3‐pyridyl)urea} have been synthesized by the reaction of L with the corresponding copper(II) salts. Complex 1 shows a dinuclear structure with a conventional “paddlewheel” motif, in which four acetate units bridge the two Cu^II ions. In complexes 2a and 2b , the anthracenyl ligand L has been converted to an anthronyl derivative L′, and the central metal ion exhibits a distorted square pyramidal arrangement, with two pyridyl nitrogen atoms and two bromide ions defining the basal plane and the apical position is occupied by a solvent molecule (CH₃OH in 2a and DMSO in 2b ).     

Zinc (II), palladium (II) and cadmium (II) complexes containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline derivatives: Synthesis,characterization and methyl methacrylate polymerization

A series of Zn (II), Pd (II) and Cd (II) complexes, [(L) _n MX ₂ ] _m (L = L‐a–L‐c; M = Zn, Pd; X = Cl; M = Cd; X = Br; n, m = 1 or 2), containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline ( L‐a ), 4‐methoxy‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐b ) and 4‐methoxy‐N‐methyl‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐c ) have been synthesized and characterized. The X‐ray crystal structures of Pd (II) complexes [L ₁ PdCl ₂ ] (L = L‐b and L‐c) revealed distorted square planar geometries obtained via coordinative interaction of the nitrogen atoms of pyridine and amine moieties and two chloro ligands. The geometry around Zn (II) center in [(L‐a)ZnCl ₂ ] and [(L‐c)ZnCl ₂ ] can be best described as distorted tetrahedral, whereas [(L‐b) ₂ ZnCl ₂ ] and [(L‐b) ₂ CdBr ₂ ] achieved 6‐coordinated octahedral geometries around Zn and Cd centers through 2‐equivalent ligands, respectively. In addition, a dimeric [(L‐c)Cd(μ ‐ Br)Br] ₂ complex exhibited typical 5‐coordinated trigonal bipyramidal geometry around Cd center. The polymerization of methyl methacrylate in the presence of modified methylaluminoxane was evaluated by all the synthesized complexes at 60°C. Among these complexes, [(L‐b)PdCl ₂ ] showed the highest catalytic activity [3.80 × 10⁴ g poly (methyl methacrylate) (PMMA)/mol Pd hr^?1], yielding high molecular weight (9.12 × 10⁵ g mol^?1) PMMA. Syndio‐enriched PMMA (characterized using ¹H‐NMR spectroscopy) of about 0.68 was obtained with T_g in the range 120–128°C. Unlike imine and amine moieties, the introduction of N‐methyl moiety has an adverse effect on the catalytic activity, but the syndiotacticity remained unaffected.     

Synthesis,Structure and Noncovalent Interactions Palladium（Ⅱ）Complexes with N—Benzoyl—β—phenylalaniate Dianion and Aromatic Diimine

Two palladium(II) complexes, [Pd(bipy)(BzPhe‐N,O)] and [Pd(phen)(BzPhe‐N,O)]·4H₂O were synthesized by reactions between Pd(bipy)Cl₂ and BzPheH₂ (N‐benzoyl‐β‐phenylalanine), Pd(phen) Cl₂ and BzPheH₂ in water at pH‐9, with their structures determined by X‐ray diffraction analysis. The Pd atom is coordinated by two nitrogen atoms of bipy (or phen), the deprotonated amido type nitrogen atom and one of the carboxylic oxygens of BzPhe (BzPhe = N‐benzoyl‐β‐phenylalaninate dianion). In the complex [Pd(phen) (BzFne‐N,O)] · 4H₂O, the side chain of phenylalanine is located above and approximately parallels to the coordination plane. Both the aromatic‐aromatic stacking interaction between the phenyl ring of phenylalanine and phen, and the metal ion‐aromatic interaction between the phenyl ring of phenylalanine and Pd(II) were observed. [Pd(bipy)(BzPhe‐N,O)] has the phenylalanyl side chain oriented outwards from the coordination plane, which is mainly due to the interaction between the carbonyl oxygen atom of the amido group and the phenyl ring of phenylalanine. The reason for the different orientation of phenylalanyl side chain in the complexes was suggested.     

Synthesis and Characterization of Palladium(II) Complexes with 2‐(2′‐Pyridyl)quinoline. Catalytic Air Oxidation of Olefins by Palladium(II) Complexes

Palladium(II) complexes of 2‐(2′‐pyridyl)quinoline (PQ), namely [PdX₂(PQ)] (X = Br^?, I^?, N₃^?, NO₂^?, SCN^?, acac) and [PdCl(NO₃)(PQ)] have been synthesized via substitution reactions of [PdCl₂(PQ)] with an excess of sodium salts and acetylacetone. The complexes have been characterized by elemental analysis, conductivity measurements, IR, ¹H and ¹³C NMR spectroscopy. Selected complexes have been further characterized using electrospray ionization (ESI) and ion trap mass spectroscopy (ITMS). Some complexes are found to catalyze the rapid air oxidation of α‐olefins under Wacker oxidation. The chlorohydrin products are produced in good to excellent yields while oxidation products are obtained in low yields. The [PdCl₂(PQ)] complex is found to have the highest catalytic activity.     

Highly Selective Salicylate Membrane Electrode Based on N,N＇- （Aminoethyl）ethylenediamide Bis（2-salicylideneimine） Binuclear Copper（Ⅱ） Complex as Neutral Carrier

A new ion selective electrode for salicylate based on N,N＇-（aminoethyl）ethylenediamide bis（2-salicylideneimine） binuclear copper（Ⅱ） complex [Cu（Ⅱ）2-AEBS] as an ionophore was developed. The electrode has a linear range from 1.0 × 10^-1 to 5.0 ×10^-7 mol·L^- 1 with a near-Nemstian slope of （ - 55 ±1 ） mV/decade and a detection limit of 2.0 × 10-7 mol·L^-1 in phosphorate buffer solution of pH 5.0 at 25 ℃. It shows good selectivity for Sal^- and displays anti-Hofmeister selectivity sequence： Sal^-〉SCN^-〉 ClO4^- 〉I^-〉 NO2^- 〉Br^-〉 NO3^- 〉Cl^-〉 SO3^2- 〉 SO4^2- The proposed sensor based on binuclear copper（Ⅱ）complex has a fast response time of 5-10 s and can be used for at least 2 months without any major deviation. The response mechanism is discussed in view of the alternating current （AC） impedance technique and the UV-vis spectroscopy technique. The effect of the electrode membrane compositions and the experimental conditions were studied. The electrode has been successfully used for the determination of salicylate ion in drug pharmaceutical preparations.     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.     

Synthesis and Structure Characterization of 2‐(Dimethylaminomethyl)pyrrolate and 2,5‐Bis(dimethylaminomethyl)pyrrolate Zirconium Complexes

Tetrakis(diethylamido)zirconium reacts with 2‐(dimethylamino)methyl pyrrole (DMAMP) and 2,5‐[bis(dimethylamino)methyl]pyrrole (BDMAMP) to give Zr(NEt)₂(DMAMP)₂ 1 and Zr(NEt)₃(BDMAMP) 2 , respectively. Both 1 and 2 have been characterized by ¹H and ¹³C NMR spectroscopies and 1 has also been characterized by X‐ray crystallography. Complex 1 shows an agostic interaction between Zr and H(21A) in solid state that is not sustained in solution. Reacting 1 with 2 equivalents of trimethylsilyl chloride in toluene yields ZrCl₂(DMAMP)₂ 3 in 75% yield which was characterized by ¹H and ¹³C NMR spectroscopies.     

Preparation,Structural Characterization,and Antifungal Activities of Complexes of Group 12 Metals with 2‐Acetylpyridine‐ and 2‐Acetylpyridine‐N‐oxide‐4N‐phenylthiosemicarbazones

Reaction of group 12 metal dihalides in ethanolic media with 2‐acetylpyridine ⁴N‐phenylthiosemicarbazone ( H4PL ) and 2‐acetylpyridine‐N‐oxide ⁴N‐phenylthiosemicarbazone ( H4PLO ) afforded the compounds [M(H4PL)X₂] (X = Cl, Br, M = Zn, Cd, Hg; X = I, M = Zn, Cd) ( 1–8 ), [Hg(4PL)I]₂ ( 9 ) and [M(H4PLO)X₂] (X = Cl, Br, I, M = Zn, Cd, Hg) ( 10–18 ). H4PL , H4PLO and their complexes were characterized by elemental analysis and by IR and ¹H and ¹³C NMR spectroscopy (and the cadmium complexes by ¹¹³Cd NMR spectroscopy), and H4PL , H4PLO , ( 5 · DMSO) and ( 9 ) were additionally studied by X‐ray diffraction. H4PL is N,N,S‐tridentate in all its complexes, including 9 , in which it is deprotonated, and H4PLO is in all cases O,N,S‐tridentate. In all the complexes, the metal atoms are pentacoordinate and the coordination polyhedra are redistorted tetragonal pyramids. In assays of antifungal activity against Aspergillus niger and Paecilomyces variotii, the only compound to show any activity was [Hg(H4PLO)I₂] ( 18 ).     

Electrosynthesis and Characterization of Poly(N‐(9‐fluorenylmethoxycarbony)‐glycine)

High‐quality poly(N‐(9‐fluorenylmethoxycarbony)‐glycine) (PFG), a new kind of soluble polyfluorene derivative, was successfully synthesized electrochemically by direct anodic oxidation of N‐(9‐fluorenylmethoxycarbony)‐glycine (FG) in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of FG in BFEE was only 0.6 V vs. Pt, which was much lower than that in acetonitrile +0.1 mol/L tetrabutylammonium tetra?uoroborate (TBATFB). PFG film obtained from BFEE showed good electrochemical activity and thermal stability. It indicates that BFEE is a better medium for the electrosynthesis of PFG film. PFG is highly soluble in common organic solvents, facilitating potential applications as a blue‐light‐emitting material. Fluorescent spectra revealed that PFG was a good blue‐light emitter. Results of FT‐IR and ¹H NMR spectra indicated the polymerization location of N‐(9‐fluorenylmethoxycarbony)‐glycine occurred mainly at C(2) and C(7) positions of the fluorine ring.     

Synthesis of a new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxycarbonyl)aminobenzenesulfonamide and its copolymerization with N‐phenyl maleimide

The new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxy‐ carbonyl)aminobenzenesulfonamide (MPBAS) (M₁) is synthesized using sulfadiazine as parent compound. It could be homopolymerized and copolymerized with N‐phenyl maleimide (NPMI) (M₂) by radical mechanism using AIBN as initiator at 60 °C in dimethylformamide. The new monomer MPBAS and polymers were identified by IR, element analysis and ¹H NMR in detail. The monomer reactivity ratios in copolymerization were determined by YBR method, and r₁ (MPBAS) = 2.39 ± 0.05, r₂ (NPMI) = 0.33 ± 0.02. In the presence of ammonium formate, benzyloxycarbonyl groups could be broken fluently from MPBAS segments of copolymer by catalytic transfer hydrogenation, and the copolymer with sulfadiazine side groups are recovered. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2548–2554, 2000     

Synthesis,Structure and Photoluminescent Properties of Zn(II)/Cd(II)‐Complexes Containing 2,4,6‐Tris‐(benzimidazolyl‐2‐yl)pyridine Ligand

Hydrothermal reactions of tridentate rigid 2,4,6‐tris‐(benzimidazolyl‐2‐yl)pyridine (pytbzim) ligand and Zn(II)/Cd(II) salts generate binuclear complexes {[Cd₂Cl₂(pytbzim)₂(H₂O)₂]·2NO₃}_n ( 1 ) and two isomorphs {[M₂Cl₂(pytbzim)₂(H₂O)₂]Cl₂·2H₂O}_n [M=Cd ( 2 ), Zn ( 3 )]. All complexes include [M₂Cl₂(pytbzim)₂(H₂O)₂] dimers, which are further connected into a three‐dimensional supramolecular networks through ?‐? stacking interaction and hydrogen bonds. The solid state photoluminescent studies reveal good fluorescent properties of the pytbzim ligand and complexes 1 – 2 at room temperature.     

Synthesis and Crystal Structure of Mercury(II) Metal Crown Ether with N‐Heterocyclic Carbene Linkage

The mercury(II) metal crown ether ( 2a ) was obtained in high yield by reaction of the carbene precursor 1,2‐bis[N‐(1‐naphthylmethylene)imidazoliumethoxy]benzene dihexafluorophosphate ( 1 ) and Hg(OAc)₂. Addition of NaI to the acetone solution of 2a resulted in precipitation of pale yellow solid 2b . The structures of 2a and 2b were determined by single‐crystal X‐ray diffractometry. Both molecules display a helical conformation with a torsional cycle. The mercury atom in complex 2a is tricoordinated by two intramolecular carbene carbon atoms and an acetate oxygen atom. The mercury atom in complex 2b is tetracoordinated by two intramolecular carbene carbon atoms and two cis‐iodine atoms.     

Novel Ytterbium(III) Selective Membrane Sensor Based on N‐(2‐Pyridyl)‐N′‐(2‐Methoxyphenyl)‐Thiourea as an Excellent Carrier and Its Application to Determination of Fluoride in Mouth Wash Preparation Samples

The construction, performance, and applications of a novel ytterbium(III) sensor based on N‐(2‐pyridyl)‐N′‐(2‐methoxyphenyl)‐thiourea (PMT), as an excellent carrier, in plasticized poly(vinyl chloride) PVC matrix, is described. The influences of membrane composition and pH on the potentiometric response of the sensor were investigated. The sensor exhibits a nice Nernstian response for Yb(III) ion over a wide concentration range of 4 decades of concentration (1.0×10^?6–1.0×10^?2 M), and a detection limit of 5.0×10^?7 M. The response time of the electrodes is between 8 and 10 s, depending on the concentration of ytterbium(III) ions. The proposed sensor can be used for about 8 weeks without any considerable divergence in potential. The sensor revealed very good selectivity for Yb(III) in the presence of several metal ions. The best performance was observed for the membrane containing; 30% PVC, 59% o‐nitrophenyloctyl ether (NPOE) as solvent mediator, 7% PMT, and 4% sodium tetraphenyl borate (NaTPB). It was successfully applied as indicator electrodes in the potentiometric titration of Yb(III) with EDTA and for the determination of fluoride ion in two mouth wash formulations. The proposed La(III) sensor was found to work well under laboratory conditions. It was also used as an indicator electrode in titration of a 1.0×10^?4 M of Yb(III) with a standard EDTA solution (1.0×10^?2 M). It was also used for determination of Yb(III) ion in Xenotime .     

Synthesis and Cytotoxicity of 2‐(2′‐Pyridyl)benzimidazole Complexes of Palladium(II) and Platinum(II)

Compounds of type [MX₂(Hpben)] [M = Pd (X = Cl), Pt (X = Cl, I); Hpben = 2‐(2′‐pyridyl)benzimidazole] were prepared and characterized, and the structures of the Pt derivatives were determined by X‐ray crystallography. The crystals of [PtI₂(Hpben)] consist of discrete units in which the Pt atom is coordinated to two iodine atoms and to pyridine and imidazole N atoms in a distorted square planar arrangement. The structure of the chloro derivative is similar, except that the [PtCl₂(Hpben)] monomers are hydrogen‐bonded in zig‐zag chains. In assays of the interactions of the Pd and Pt chloro compounds with DNA, and of their in vitro cytotoxic activity against human cervical carcinoma cells (HeLa‐229), human ovarian carcinoma cells (A2780) and a cisplatin‐resistant mutant A2780 line (A2780cis), the only activity observed was modest cytotoxicity of the Pd derivative for A2780.     

Five‐coordinate dinuclar cobalt (II), copper (II), zinc (II) and cadmium (II) complexes with 4‐bromo‐N‐(2‐pyridinylmethylene)benzenamine: Synthesis,characterisation and methyl methacrylate polymerization

A series of late transition metal complexes, [(bpma)Co(μ – Cl)Cl] ₂ , [(bpma)Cu(μ – Cl)Cl] ₂ , [(bpma)Zn(μ – Cl)Cl] ₂ and [(bpma)Cd(μ – Br)Br] ₂ (where bpma is 4‐bromo‐N‐((pyridin‐2‐yl)methylene)benzenamine) have been synthesized and structurally characterized. The X‐ray structures of dimeric complexes [(bpma)M(μ – X)X] ₂ (M = Co, Cu and Zn, X = Cl; M = Cd, X = Br) showed a distorted 5‐coordinate trigonal bipyramidal geometry involving two nitrogen atoms of N,N‐bidentate ligand, two bridged and one terminal halogen atoms. The complex [(bpma)Cu(μ – Cl)Cl] ₂ revealed the highest catalytic activity for the polymerisation of methyl methacrylate in the presence of modified methylaluminoxane with an activity of 9.14 × 10⁴ g PMMA/mol·Cu·h at 60 °C and afforded syndiotactic poly (methylmethacrylate) (rr = 0.69).     

Copper(II)‐Catalyzed Synthesis of N‐Substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones by the Reaction of N‐Substituted‐2‐iodobenzamides with Malononitrile

A novel Cu(OAc)₂·H₂O catalyzed coupling reaction of N‐substituted‐2‐iodobenzamides with malononitrile to afford N‐substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones is described. The reaction proceeded in DMSO at 90°C for 5 h in nitrogen without external ligands.     

N-(4-甲基苯甲酰氨基) N’-[5-(2-三氟甲基苯基)-2-呋喃甲酰硫脲的合成、晶体结构测定与生物活性测定

本文首次合成标题化合物N-(4-甲基苯甲酰氨基)-N’-[5-(2-三氟甲基苯基)-2-呋喃甲酰硫脲。化合物(C21H16F3N3O3S, Mr = 447.43)单晶经测定为单斜晶体,空间群为P -1。在晶体中,存在一些分子内和分子间的相互作用,分子间还有C—H···π 的相互作用,这可能导致晶体更稳定的原因。目标产物的结构经IR, H NMR和元素分析测定确证。初步生物活性测试表明,部分化合物对棉花枯萎病、黄瓜灰霉病、苹果轮纹病和棉花炭疽病有较好的选择性杀菌活性;部分目标化合物有较好的除草活性。     

Copper(II) bromide,nitrate and perchlorate complexes with sterically demanding N‐(6‐methylpyridin‐2‐yl)acetamide ligands

Functionalized acid amides are widely used in biology, medicine, environmental chemistry and many other areas. Among them, pyridine‐substituted amides, in particular N‐(pyridin‐2‐yl)acetamide and its derivatives, play an important role due to their excellent chelating properties. The donor properties of these ligands can be effectively modified by introducing electron‐donating substituents (e.g. alkyl groups) into the heterocycle. On the other hand, substituents in the α‐position of the pyridine ring can create steric hindrance, which significantly influences the coordination number and geometry. To achieve a better understanding of these effects, copper(II) complexes with sterically demanding N‐(6‐methylpyridin‐2‐yl)acetamide ligands (L ) and monoanions of different size, shape and coordination ability have been chosen as model compounds. The crystal structures of three new compounds, bromidobis[N‐(6‐methylpyridin‐2‐yl‐κN )acetamide‐κO ]copper(II) bromide, [CuBr(C₈H₁₀N₂O)]Br, (I), aquabis[N‐(6‐methylpyridin‐2‐yl‐κN )acetamide‐κO ]copper(II) dinitrate, [Cu(C₈H₁₀N₂O)(H₂O)](NO₃)₂, (II), and aquabis[N‐(6‐methylpyridin‐2‐yl‐κN )acetamide‐κO ]copper(II) bis(perchlorate), [Cu(C₈H₁₀N₂O)(H₂O)](ClO₄)₂, (III), have been determined by single‐crystal X‐ray diffraction analysis. It has been shown that the presence of the 6‐methyl group results in either a distorted square‐pyramidal or a distorted trigonal–bipyramidal coordination geometry around the Cu^II centres instead of the typical octahedral geometry observed when the methyl substituent is absent or occupies any other position on the pyridine ring. Moreover, due to the steric hindrance provided by the L ligands, only the bromide ligand, the smallest of the series, enters into the first coordination sphere of the Cu^II ion in (I). In (II) and (III), the vacant coordination site of the Cu^II ion is occupied by a water molecule, while the nitrate and perchlorate anions are not involved in coordination to the metal centre. The structures of (I)–(III) are characterized by the presence of one‐dimensional infinite chains formed by hydrogen bonds of the types N—H…Br [in (I)], N—H…O and O—H…O [in (II) and (III)] between the amide groups of the L ligands, the coordinated water molecules and the uncoordinated anions. The hydrogen‐bonded chains are further interconnected through π–π stacking interactions between the pyridine rings of the L ligands, with approximate interplanar separations of 3.5–3.6 Å.     

Dinuclear Macrocyclic Quinoline Bridged Mercury and Silver Bis(N‐heterocyclic Carbene) Complexes: Synthesis,Structure, and Spectroscopic Studies

Quinoline bridged imidazolium precursors 5,8‐bis(N‐R‐imidazolylidenylmethylene)quinoline PF₆^– salts [H₂L](PF₆)₂ [R = Me ( 1a ), R = naphthylmethyl ( 1b )] were prepared by quaternization of N‐methylimidazole and N‐naphthylmethylimidazole with 5,8‐bis(bromomethyl)quinoline, respectively. Reaction of the imidazolium ligands 1a and 1b with Hg(OAc)₂ and Ag₂O in acetonitrile gave the macrocyclic transition metal carbene complexes [Hg₂L₂](PF₆)₄ ( 2a and 2b ) and [Ag₂L₂](PF₆)₂ ( 3a and 3b ), respectively. All the N‐heterocyclic carbene complexes were characterized in detail by NMR, ESI‐MS, and elemental analysis. Structures of complexes 2a and 3a were determined by X‐ray diffraction studies. Structural studies revealed that the coordination arrangement of the central mercury atom in complex 2a displays a tricoordinate mode and the molecular conformation results in a“closed” form with the bridging quinoline functionality in the macrocycle, whereas the silver complex 3a does not show an coordiantion between the bridging quinoline and the Ag^I ion, which results in an “open” conformation of the macrocycle. The Hg^II and Ag^I NHC complexes showed similar UV absorption and luminescence in acetonitrile solutions.