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.     

Bis(5,7‐dimethyl‐8‐hydroxyquinolinato)platinum(II) Complex for Efficient Organic Heterojunction Solar Cells

Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8‐hydroxyquinoline (Hq) or 5,7‐dimethyl‐8‐hydroxy‐quinoline (HMe₂q) as an electron donor were fabricated by vacuum deposition. The bis(5,7‐dimethyl‐8‐hydroxyquinolinato)platinum(II) [Pt(Me₂q)₂]‐based OPVs showed the best performance with an open voltage (V_OC) of 0.42 V, a short circuit current density (J_SC) of 14.8 mA cm^?2, and a maximum power conversion efficiency (η_P) of 2.4 %. The X‐ray single‐crystal structures together with the grazing incidence X‐ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as‐fabricated field‐effect transistors (FETs) and OPV cells.     

Structure of AcMet-Gly and Its Interaction with Palladium（Ⅱ） Tetraaqua Complex Studied by Electrospray Mass Spectrometry and Density Functional Theory

The structure of dipepide AcMet‐Gly was determined by X‐ray crystallographic analysis. It possesses mono‐clinic, space group P2₁ (No. 4). with cell dimensions of α=0.8571(2) nm, b=0.5871(2) nm, c= 1.197(3) nm, β= 99.290(10)°. V=0.5944(15) nm³, Z=2, μ=2.74 cm^?1. Mononuclear chelates, described as [Pd(X)(S,N,O‐AcMet‐Gly)]^?, in which Pd(II) is coordinated by thioether, deprotonated amide nitrogen, carbonyl oxygen of me‐thionine and X (AcMetGly or other ligands present in aqueous solution or in mobile phase solution), were detected 5 min after mixing AcMet‐Gly with [Pd(H₂O)₄]^2‐ at room temperature using electrospray ionization mass spectrometry. The geometry of [Pd(H₂O)(S,N,O‐AcMet‐Gly)]^? is optimized at density functional B3LYP/LanL2DZ level. The fused five‐ and six‐membered chelate is responsible for cleavage of Met‐Gly bond. This is the first time to provide a direct evidence for Pd(II)‐mediated cleavage of dipeptides via external solvent attack.     

Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)₂RuCl₂] reacts with dinitro‐tetramethylbibenzimidazole ( A ) in DMF to form the complex [(tbbpy)₂Ru( A )](PF₆)₂ ( 1a ) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF₆^? anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the ¹H NMR spectra and X‐ray analyses of both 1a and 1b , the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl₂/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)₂Ru( C )](PF₆)₂ and [(tbbpy)₂Ru( D )](PF₆)₂ ( C : dibromo‐tetrabibenzimidazole, D : diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base Ru^II complexes 5 and 6 . ¹H NMR spectra show that the substituents (NH₂, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2 , and 3 , determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru( A )] ( 7 ) and [( A )PtCl₂] ( 8 ) display also that the nitro groups in these complexes are in a cis‐arrangement.     

Dinuclear Palladium Complexes with Two Ligand‐Centered Radicals and a Single Bridging Ligand: Subtle Tuning of Magnetic Properties

The facile and tunable preparation of unique dinuclear [(L^?)Pd?X?Pd(L^?)] complexes (X=Cl or N₃), bearing a ligand radical on each Pd, is disclosed, as well as their magnetochemistry in solution and solid state is reported. Chloride abstraction from [PdCl( NNO^ISQ )] ( NNO^ISQ =iminosemiquinonato) with TlPF₆ results in an unusual monochlorido‐bridged dinuclear open‐shell diradical species, [{Pd( NNO ^ISQ)}₂(μ‐Cl)]⁺, with an unusually small Pd‐Cl‐Pd angle (ca. 93°, determined by X‐ray). This suggests an intramolecular d⁸–d⁸ interaction, which is supported by DFT calculations. SQUID measurements indicate moderate antiferromagnetic spin exchange between the two ligand radicals and an overall singlet ground state in the solid state. VT EPR spectroscopy shows a transient signal corresponding to a triplet state between 20 and 60 K. Complex 2 reacts with PPh₃ to generate [Pd(NNO^ISQ)(PPh₃)]⁺ and one equivalent of [PdCl( NNO^ISQ )]. Reacting an 1:1 mixture of [PdCl( NNO^ISQ )] and [Pd(N₃)( NNO^{I SQ})] furnishes the 1,1‐azido‐bridged dinuclear diradical [{Pd( NNO ^ISQ)}₂(κ¹‐N;μ‐N₃]⁺, with a Pd‐N‐Pd angle close to 127° (X‐ray). Magnetic and EPR measurements indicate two independent S=1/2 spin carriers and no magnetic interaction in the solid state. The two diradical species both show no spin exchange in solution, likely because of unhindered rotation around the Pd?X?Pd core. This work demonstrates that a single bridging atom can induce subtle and tunable changes in structural and magnetic properties of novel dinuclear Pd complexes featuring two ligand‐based radicals.     

Synthesis,Interionic Structure,and Reactivity toward CO and p‐Methylstyrene of Palladacyclic Compounds Bearing α‐Diimine Ligands

Palladacyclic compounds [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] (R = Et, ⁱPr, 2,6‐ⁱPr₂C₆H₃; N? N = bpy = 2,2′‐bipyridine, or 1,4‐(o,o′‐dialkylaryl)‐1,4‐diazabuta‐1,3‐dienes; [X]^? = [BF₄]^? or [PF₆]^?) were synthesized from the dimers [{Pd(C₆H₄(C₆H₅C?O)C?N? R)(μ‐Cl)}₂] and N? N ligands. Their interionic structure in CD₂Cl₂ was determined by means of ¹⁹F,¹H‐HOESY experiments and compared with that in the solid state derived from X‐ray single‐crystal studies. [Pd(C₆H₄(C₆H₅C?O)C?N? R)(N? N)] [X] complexes were found to copolymerize CO and p‐methylstyrene affording syndiotactic or isotactic copolymers when bpy or 1,4‐(o,o′‐dimethylaryl)‐1,4‐diazabuta‐1,3‐dienes were used, respectively. The reactions with CO and p‐methylstyrene of the bpy derivatives were investigated. Two intermediates derived from a single and a double insertion of CO into the Pd? C bonds were isolated and completely characterized in solution.     

Synthesis and Self‐Assembly of NCN‐Pincer Pd‐Complex‐Bound Norvalines

The NCN‐pincer Pd‐complex‐bound norvalines Boc‐D /L ‐[PdCl(dpb)]Nva‐OMe ( 1 ) were synthesized in multigram quantities. The molecular structure and absolute configuration of 1 were unequivocally determined by single‐crystal X‐ray structure analysis. The robustness of 1 under acidic/basic conditions provides a wide range of N‐/C‐terminus convertibility based on the related synthetic transformations. Installation of a variety of functional groups into the N‐/C‐terminus of 1 was readily carried out through N‐Boc‐ or C‐methyl ester deprotection and subsequent condensations with carboxylic acids, R¹COOH, or amines, R²NH₂, to give the corresponding N‐/C‐functionalized norvalines R¹‐D /L ‐[PdCl(dpb)]Nva‐R² 2 – 9 . The dipeptide bearing two Pd units 10 was successfully synthesized through the condensation of C‐free 1 with N‐free 1 . The robustness of these Pd‐bound norvalines was adequately demonstrated by the preservation of the optical purity and Pd unit during the synthetic transformations. The lipophilic Pd‐bound norvalines L ‐ 2 , Boc‐L ‐[PdCl(dpb)]Nva‐NH‐n‐C₁₁H₂₃, and L ‐ 4 , n‐C₄H₉CO‐L ‐[PdCl(dpb)]Nva‐NH‐n‐C₁₁H₂₃, self‐assembled in aromatic solvents to afford supramolecular gels. The assembled structures in a thermodynamically stable single crystal of L ‐ 2 and kinetically stable supramolecular aggregates of L ‐ 2 were precisely elucidated by cryo‐TEM, WAX, SAXS, UV/Vis, IR analyses, and single‐crystal X‐ray crystallography. An antiparallel β‐sheet‐type aggregate consisting of an infinite one‐dimensional hydrogen‐bonding network of amide groups and π‐stacking of PdCl(dpb) moieties was observed in the supramolecular gel fiber of L ‐ 2 , even though discrete dimers are assembled through hydrogen bonding in the thermodynamically stable single crystal of L ‐ 2 . The disparate DSC profiles of the single crystal and xerogel of L ‐ 2 indicate different thermodynamics of the molecular assembly process.     

The Structure of Bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium in the Solid State and in Solution

The complex, bis[N‐6‐aminopyridyl‐N‐(1S)‐(+)‐10‐camphorsulfonylamino]palladium, Pd[(S)‐APCS]₂, 1 , was prepared by reaction of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine with PdCl₂ in THF. Complex 1 has been characterized by spectroscopic methods and its structure has been determined by X‐ray crystallography. Crystal data: space group C2, a= 16.082 (2), b = 17.104 (2), c = 13.051 (2)Å, β = 99.95 (1)°, V = 3535.9 (8) ų, Z = 2 with final residuals R1 = 0.0491 and wR2 = 0.0944. Two independent molecules, (S,S)‐Pd[(S)‐APCS]2, 1a , and (R,R)‐Pd[(S)‐APCS]2, 1b , were found in each asymmetric unit, which exchange to each other via a series of nitrogen inversion and C‐C bond rotation. The inversion energy (ΔGc₁^≠) and the energy barrier (δGc₂^≠) were 11.5 ± 0.1 Kcal mol^?1 at 246 K and 9.8 ± 0.1 Kcal mol^?1 at 199 K, respectively, calculated by dynamic NMR data.     

Sterically‐Directed Consecutive and Size‐Selective Self‐Assembly of Palladium Diphosphane Complexes with an Ar‐BIAN Ligand: Unexpected Formation of Pentameric and Hexameric Aggregates

The coordination properties of N,N′‐bis[4‐(4‐pyridyl)phenyl]acenaphthenequinonediimine (L¹) and N,N′‐bis[4‐(2‐pyridyl)phenyl]acenaphthenequinonediimine (L²) were investigated in self‐assembly with palladium diphosphane complexes [Pd(P^P)(H₂O)₂](OTf)₂ (OTf=triflate) by using various analytical techniques, including multinuclear (¹H, ¹⁵N, and ³¹P) NMR spectroscopy and mass spectrometry (P^P=dppp, dppf, dppe; dppp=bis(diphenylphosphanyl)propane, dppf= bis(diphenylphosphanyl)ferrocene, and dppe=bis(diphenylphosphanyl)ethane). Beside the expected trimeric and tetrameric species, the interaction of an equimolar mixture of [Pd(dppp)]²⁺ ions and L¹ also generates pentameric aggregates. Due to the E/Z isomerism of L¹, a dimeric product was also observed. In all of these species, which correspond to the general formula [Pd(dppp)L¹]_n(OTf)_2n (n=2–5), the L¹ ligand is coordinated to the Pd center only through the terminal pyridyl groups. Introduction of a second equivalent of the [Pd(dppp)]²⁺ tecton results in coordination to the internal, sterically more encumbered chelating site and induces enhancement of the higher nuclearity components. The presence of higher‐order aggregates (n=5, 6), which were unexpected for the interaction of cis‐protected palladium corners with linear ditopic bridging ligands, has been demonstrated both by mass‐spectrometric and DOSY NMR spectroscopic analysis. The sequential coordination of the [Pd(dppp)]²⁺ ion is attributed to the dissimilar steric properties of the two coordination sites. In the self‐assembled species formed in a 1:1:1 mixture of [Pd(dppp)]²⁺/[Pd(dppe)]²⁺/L¹, the sterically more demanding [Pd(dppp)]²⁺ tectons are attached selectively to the pyridyl groups, whereas the more hindered imino nitrogen atoms coordinate the less bulky dppe complexes, thus resulting in a sterically directed, size‐selective sorting of the metal tectons. The propensity of the new ligands to incorporate hydrogen‐bonded solvent molecules at the chelating site was confirmed by X‐ray diffraction studies.     

Structure and electrospray mass spectrometry studies on dithiacyclooctan-3-ol-containing palladium (II) complex of trans -[Pd(dtco-3-OH)_2](ClO_4)_2·2DMSO

The structure of trans-[Pd(dtco-3-OH)2] (ClO4)2·2DMSO, in which dtco-3-OH is dithiacyclooctan-3-ol and DMSO is dimethyl sulfoxide, was determined by X-ray crystallographic analysis. The crystal data: space group pi, a = 0.7077(2) nm, b = 1.0788(1) nm, c = 1.1111(1) nm, α=67.710(8)°, β = 73. 59(2)°, γ = 85. 39(2)°,R1 = 0 . 0368 and Rw = 0.0998. The palladium (II) is coordinated by four sulfur atoms with a regular square planar configuration. The Pd-S distances are 0.2314(1) and 0.2317(1) nm, respectively. Both dtco-3-OH ligands are in the boat-chair configuration and two hydroxyl groups are on the opposite sites of the PdS4 coordination plane and are towards Pd(II). The Pd-O distance is 0. 285 nm, indicating a weak interaction between them. A typical hydrogen bond between the hydroxyl group of dtco-3-OH ligand and DMSO was observed in the crystal structure. An aqueous solution prepared with the crystals of the complex was used for the investigation of electrospray mass spectrometry ( ESMS ). Besid     

Insertion Reactions of 1,2‐Disubstituted Olefins with an α‐Diimine Palladium(II) Complex

The migratory insertions of cis or trans olefins CH(X)?CH(Me) (X = Ph, Br, or Et) into the metal–acyl bond of the complex [Pd(Me)(CO)(ⁱPr₂dab)]⁺ [B{3,5‐(CF₃)₂C₆H₃}₄]^? ( 1 ) (ⁱPr₂dab = 1,4‐diisopropyl‐1,4‐diazabuta‐1,3‐diene = N,N′‐(ethane‐1,2‐diylidene)bis[1‐methylethanamine]) are described (Scheme 1). The resulting five‐membered palladacycles were characterized by NMR spectroscopy and X‐ray analysis. Experimental data reveal some important aspects concerning the regio‐ and stereochemistry of the insertion process. In particular, the presence of a Ph or Br substituent at the alkene leads to the formation of highly regiospecific products. Moreover, in all cases, the geometry of the substituents in the formed palladacycle was the same as in the starting olefin, as a consequence of a cis addition of the Pd–acyl fragment to the C?C bond. Reaction with CO and MeOH of the five‐membered complex derived from trans‐β‐methylstyrene (= [(1E)‐prop‐1‐enyl]benzene) insertion, yielded the 2,3‐substituted γ‐keto ester 9 with an (2RS,3SR)‐configuration (Scheme 3).     

Construction and photoluminescence properties of a three‐dimensional ZnII coordination network based on naphthalene‐1,4‐dicarboxylic acid and 1,6‐bis(pyridin‐3‐yl)‐1,3,5‐hexatriene

In recent years, coordination polymers constructed from multidentate carboxylate and pyridyl ligands have attracted much attention because these ligands can adopt a rich variety of coordination modes and thus lead to the formation of crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[μ₂‐1,6‐bis(pyridin‐3‐yl)‐1,3,5‐hexatriene‐κ²N:N′](μ₃‐naphthalene‐1,4‐dicarboxylato‐κ⁴O¹,O^1′:O⁴:O^4′)zinc(II)], [Zn(C₁₂H₆O₄)(C₁₆H₁₄N₂)]_n, has been prepared by the self‐assembly of Zn(NO₃)₂·6H₂O, naphthalene‐1,4‐dicarboxylic acid (1,4‐H₂ndc) and 1,6‐bis(pyridin‐3‐yl)‐1,3,5‐hexatriene (3,3′‐bphte) under hydrothermal conditions. The title compound has been structurally characterized by IR spectroscopy, elemental analysis, powder X‐ray diffraction and single‐crystal X‐ray diffraction analysis. Each Zn^II ion is six‐coordinated by four O atoms from three 1,4‐ndc²⁻ ligands and by two N atoms from two 3,3′‐bphte ligands, forming a distorted octahedral ZnO₄N₂ coordination geometry. Pairs of Zn^II ions are linked by 1,4‐ndc²⁻ ligands, leading to the formation of a two‐dimensional square lattice ( sql ) layer extending in the ab plane. In the crystal, adjacent layers are further connected by 3,3′‐bphte bridges, generating a three‐dimensional architecture. From a topological viewpoint, if each dinuclear zinc unit is considered as a 6‐connected node and the 1,4‐ndc²⁻ and 3,3′‐bphte ligands are regarded as linkers, the structure can be simplified as a unique three‐dimensional 6‐connected framework with the point symbol 4⁴6¹⁰8. The thermal stability and solid‐state photoluminescence properties have also been investigated.     

Hydrogen‐transfer reduction of α,β‐unsaturated carbonyl compounds catalyzed by naphthyridine‐functionalized N‐heterocyclic carbene complexes

Substitution of silver complex of 2‐chloro‐7‐(mesitylimidazolylidenylmethyl)naphthyridine (NpNHC) with palladium(II), rhodium(I) and iridium(I) metal precursors provided [Pd(C ,N ‐NpNHC)(η³‐allyl)](BF₄) ( 5 ), RhCl(COD)(C ‐NpNHC) ( 6a ) and IrCl(COD)(C ‐NpNHC) ( 6b ), respectively. Abstraction of chloride from 6a and 6b with AgBF₄ provided the chelation complexes [Rh(COD)(C ,N ‐NpNHC)](BF₄) ( 7a ) and Ir(COD)(C ,N ‐NpNHC)(BF₄) ( 7b ), respectively. All complexes were characterized using NMR and elemental analyses and the structural details of 5 and 6a were further confirmed using X‐ray crystallography. In catalytic activity studies, complex 5 was found to be an effective catalyst in the hydrogen‐transfer reduction of α,β‐unsaturated carbonyl compounds into the corresponding saturated carbonyl compounds.     

A fourfold interpenetrating cadmium(II) metal–organic framework based on 2,4,6‐tris(pyridin‐4‐yl)‐1,3,5‐triazine with reversible photochromic properties

2,4,6‐Tris(pyridin‐4‐yl)‐1,3,5‐triazine (tpt), as an organic molecule with an electron‐deficient nature, has attracted considerable interest because of its photoinduced electron transfer from neutral organic molecules to form stable anionic radicals. This makes it an excellent candidate as an organic linker in the construction of photochromic complexes. Such a photochromic three‐dimensional (3D) metal–organic framework (MOF) has been prepared using this ligand. Crystallization of tpt with Cd(NO₃)₂·4H₂O in an N,N‐dimethylacetamide–methanol mixed‐solvent system under solvothermal conditions afforded the 3D MOF poly[[bis(nitrato‐κ²O,O′)cadmium(II)]‐μ₃‐2,4,6‐tris(pyridin‐4‐yl)‐1,3,5‐triazine‐κ³N²:N⁴:N⁶], [Cd(NO₃)₂(C₁₈H₁₂N₆)]_n, which was characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis and single‐crystal X‐ray diffraction. The X‐ray diffraction crystal structure analysis reveals that the asymmetric unit contains one independent Cd^II cation, one tpt ligand and two coordinated NO₃^? anions. The Cd^II cations are connected by tpt ligands to generate a 3D framework. The single framework leaves voids that are filled by mutual interpenetration of three independent equivalent frameworks in a fourfold interpenetrating architecture. The compound shows a good thermal stability and exhibits a reversible photochromic behaviour, which may originate from the photoinduced electron‐transfer generation of radicals in the tpt ligand.     

A highly active multi‐usable palladium pyridylfluorene film‐based catalyst for C–C cross‐coupling reactions

The two terminal pyridyl nitrogen atoms of 2,7‐bis(4‐pyridyl)fluorene ( 1 ) were coordinated to Pd(II) ions to give self‐assembled, multilayer films using the layer‐by‐layer (LbL) method. The films were prepared by alternately dipping the substrate, pre‐coated with a polyethyleneimine layer, in aqueous solutions of PdCl₂ and ethanol solutions of 1 . The resulting films were characterized using UV–visible absorption spectroscopy, atomic force microscopy (AFM), X‐ray photoelectron spectroscopy, scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP‐AES). UV–visible spectra and SEM images show almost uniform growth of the film in a near ideal LbL manner. AFM images show that nanostructured aggregates of Pd(II) complexes form on the surface. With an increase in the number of Pd(II)/ 1 bilayers, more particulate aggregates are distributed on the surface. When released from the substrate, the Pd(II) complex nanostructure shows high catalytic activity for Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions. The catalyst loading is as low as 9.1 × 10^?3 mol% Pd, as measured using ICP‐AES, and high turnover numbers of up to 1.08 × 10⁴ are obtained. Copyright © 2015 John Wiley & Sons, Ltd.     

Structure Investigations on 4‐Halo‐1,2,3,5‐dithiadiazolyl Radicals XCNSSN• (X = F,Cl, Br): The Shortest Intradimer S···S Distance in Dithiadiazolyl Dimers

Crystals of the 4‐halo‐1,2,3,5‐dithiadiazolyl radicals (X = F, Cl, Br) were obtained by sublimation at 80 °C and 10^?2 Torr, and the structures were determined by X‐ray diffraction. The fluoro derivative crystallizes as a cisoid dimer in the space group P2₁/n, whereas the chloro and bromo derivatives crystallize isomorphous as twisted dimers in the space group C2/c. The chloro and bromo derivatives show the shortest intradimer S···S contacts of all known 1,2,3,5‐dithiadiazolyl dimers. In addition the obtained structure of ClCN₂S₂^? represents the fifth polymorph of ClCN₂S₂^? characterized by X‐ray crystallography. The structures and the packing including secondary interactions are discussed.     

Ionic thermo‐responsive copolymer with multi LCST values: easy and fast LCST‐change through anion exchange

An ionic thermo‐responsive copolymer with multiple lower critical solution temperatures (multi‐LCSTs) has been developed, and the multi‐LCSTs were easily changeable according to the various counter anion types. The multi‐LCST values were achieved by introducing an ionic segment with an imidazolium moiety within the p‐NIPAAm polymer chain to produce poly(NIPAAm‐co‐BVIm) copolymers, [p‐NIBIm]⁺[Br]^?, and changing the counter anion type to produce [p‐NIBIm]⁺[X]^? (X = Cl, AcO, HCO₃, BF₄, CF₃SO₃, PF₆, SbF₆). The as‐prepared temperature‐responsive copolymers were physicochemically characterized via proton nuclear magnetic resonance spectroscopy (¹H‐NMR), Fourier‐transform infrared, X‐ray photoelectron spectroscopy, and thermogravimetric analysis. Their various LCST values, micelle sizes, and surface charges were determined using an Ultraviolet‐visible spectrophotometer and a Zeta (ξ) sizer, which were fitted with temperature and stirring control. The copolymers showed a broad LCST spectrum between 39°C and 52°C. The Zeta (ξ) potential values at a pH = 7 decreased from about +9.7 for [p‐NIBIm]⁺[X]^? (X = Cl ≈ Br) to about +2.0 mV for [p‐NIBIm]⁺[X]^? (X = PF₆ ≈ SbF₆). The micelle size (or volume) of the copolymers with different anionic species gradually increased from 181.2 nm (or 2.49 × 10^?17 cm^?3) for [p‐NIBIm]⁺[Br]^? to 229.2 nm (or 5.04 × 10^?17 cm^?3) for [p‐NIBIm]⁺[CF₃SO₃]^?, showing a clear effect of the anion on the micelle size (or volume) at a constant temperature, such as body temperature. The fact that the most important physicochemical properties for the thermo‐responsive copolymers, such as the LCST value, micelle size (or volume), and surface charge, could be easily controlled only through the anion exchange suggests these are highly applicable as ionic thermo‐responsive copolymers in a drug (or gene, protein) delivery system. Copyright © 2015 John Wiley & Sons, Ltd.     

N‐heterocyclic carbene–palladium(II) complex supported on magnetic mesoporous silica for Heck cross‐coupling reaction

Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe₃O₄@SiO₂‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe₃O₄@SiO₂‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl₂(SMe₂)₂] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g^?1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K₂CO₃ as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability.     

Structural studies and cytotoxic activity of a new dinuclear coordination compound of palladium(II)–2,2′:6′,2″‐terpyridine with rigid dianionic 1,2,4‐triazole‐3‐sulfonate linker

A new dinuclear coordination compound of palladium(II), [Pd₂(terpy)₂(μ‐tas‐N¹,N⁴)]SO₄?11H₂O ( 1 ), was synthesized by tethering a doubly deprotonated 1,2,4‐triazole‐3‐sulfonate (tas) linker generated in situ via oxidation of 1,2,4‐triazole‐3‐thione (tat) under the synthetic conditions. X‐ray diffraction analysis reveals that tat molecules adopt the thione form in the solid state, and are combined in infinite chains by symmetrically related classical intermolecular hydrogen bonds N1─H1???S1, N3─H3???N2 to give rise to R₂²(7) pattern in one‐dimensional chains along the b‐axis propagating along the a‐axis. Further short contacts through lone pairs of N2???S1 on the rings between the adjacent chains along the a‐axis lead to a two‐dimensional network structure. Compound 1 was characterized using infrared, ¹H NMR and UV–visible spectroscopies, electrospray ionization mass spectrometry and X‐ray crystallography. The crystal structure determination of 1 reveals that the Pd(II) ions are coordinated with four nitrogen atoms: three from terpy and one from tas acting as an end‐to‐end (μ‐1,4) bridging ligand. The Pd(II) ions in 1 adopt a distorted square planar geometry. The anti‐growth effect of 1 was tested on colorectal cancer (HCT‐15), non‐small‐cell lung cancer (A549), prostate cancer (PC‐3) and cervical cancer (HeLa) cell lines using sulforhodamine B viability assay. The cytotoxic effect was further confirmed using adenosine triphosphate viability assay. Compound 1 shows a promising cytotoxic activity in the diverse cancer cell models in vitro (p <0.0001).     

Crystal Structure and Characterization of Pd(II) Bis(diiso‐propyldithiocarbamate) Complex

The crystal and molecular structure of [Pd(iPr₂dtc)₂] (dtc = dithiocarbamate) have been determined by X‐ray crystallography. The unit cell of the crystal structure consists of two discrete monomelic molecules of [Pd(iPr₂dtc)₂]. The Pd(II) ion has an square‐planar geometry. The electronic and IR spectral data are in agreement with the X‐ray structure. The TG data indicate slight degradation of a few percent.