TMEDA in Iron‐Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic “ate” Complex Formation

The reactions of iron chlorides with mesityl Grignard reagents and tetramethylethylenediamine (TMEDA) under catalytically relevant conditions tend to yield the homoleptic “ate” complex [Fe(mes)₃]^? (mes=mesityl) rather than adducts of the diamine, and it is this ate complex that accounts for the catalytic activity. Both [Fe(mes)₃]^? and the related complex [Fe(Bn)₃]^? (Bn=benzyl) react faster with representative electrophiles than the equivalent neutral [FeR₂(TMEDA)] complexes. Fe^I species are observed under catalytically relevant conditions with both benzyl and smaller aryl Grignard reagents. The X‐ray structures of [Fe(Bn)₃]^? and [Fe(Bn)₄]^? were determined; [Fe(Bn)₄]^? is the first homoleptic σ‐hydrocarbyl Fe^III complex that has been structurally characterized.     

A “plug and play” polymer through biocomplementary hydrogen bonding

This article describes a DNA‐like polymer that exhibits the ability to self‐assemble through hydrogen bonding. We synthesized poly[1‐(4‐vinylbenzyl)thymine] (PVBT) and 9‐hexadecyladenine (A‐C16) through an atom transfer radical polymerization (ATRP) and alkylation, respectively. Biocomplementary PVBT/A‐C16 hierarchical supramolecular complexes formed in dilute DMSO solution through nucleobase recognition, that is, hydrogen bonding interactions between the thymine (T) groups of PVBT and the adenine (A) group of A‐C16; evidence for this molecular recognition was also gained from dynamic light scattering studies. ¹H NMR titration studies in CDCl₃ showed that T–A complexes formed rapidly on the NMR time scale with high association constants (up to 534 M^?1). Moreover, FTIR spectroscopic, differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering analyses provided further details into the nature of the self‐assembly of these systems. In the bulk state, these complexes self‐assemble into well‐ordered lamellar structures; the changing d‐spacing distance (ranging from 4.98 to 2.32 nm) at different A‐C16 loadings reveals that the molecular structures of the PVBT/A‐C16 complexes are readily tailored. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6416–6424, 2008     

Synthesis and clustering of supramolecular “graft” polymers

The synthesis and melt rheology of supramolecular poly(isobutylene) polymers bearing statistically distributed hydrogen‐bonding moieties is reported, aiming at understanding the formation of the underlying supramolecular networks for self‐healing polymers. Two different hydrogen bonds were incorporated into a poly(isobutylene) (PIB) copolymer, one based on a (weak) pyridinium/pyridine interaction, the other based on a (stronger) 2,6‐diaminotriazine/thymine interaction. A direct copolymerization based on living cationic polymerization of isobutene and the comonomers 1 , 2 , and 4 in amounts of 1 mol % lead to the copolymers PIB‐ 1 , PIB‐ 2 , and PIB‐ 4 with a content of ～1 mol % of comonomer and molecular weights ranging from ～2000 to 19,000 g mol^?1 (M_w/M_n ～ 1.2–1.5). Subsequent azide/alkyne “click” chemistry enabled the attachment of 2,6‐diaminotriazine‐ and thymine‐moieties to yield the copolymers PIB‐ 5 , PIB‐ 6 , and PIB‐ 7 . Proof of the statistical incorporation of ～1 mol % of hydrogen‐bonding moieties was achieved by ¹H NMR spectroscopy and matrix‐assisted laser desorption ionization measurements. The true presence of a supramolecular network in PIB‐ 1 (pyridinium/pyridine interaction) as well as with 1/1 blends of PIBs interacting via the 2,6‐diaminotriazine/thymine interaction (PIB‐ 5 /PIB‐ 6 ) was proven via the increasing plateau modulus with increasing molecular weights (5.5k, 9.9k, 12.4k, 16k, and 19k). Dynamics of the hydrogen bonds in the melt state was investigated by determining the effective cluster lifetime ( τ ) observing a clear difference in the (weaker) pyridinium/pyridine interaction ( τ ～ 1 s) to the 2,6‐ (stronger) diamintriazine/thymine interaction ( τ ～ 100 s). The so‐generated materials will be useful as a basis for self‐healing polymers, as dynamics plays a major role in such polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Stoichiometrically Controlled Revocable Self‐Assembled “Spiro” versus Quadruple‐Stranded “Double‐Decker” Type Coordination Cages

The simple combination of Pd^II with the tris‐monodentate ligand bis(pyridin‐3‐ylmethyl) pyridine‐3,5‐dicarboxylate, L , at ratios of 1:2 and 3:4 demonstrated the stoichiometrically controlled exclusive formation of the “spiro‐type” Pd₁L₂ macrocycle, 1 , and the quadruple‐stranded Pd₃L₄ cage, 2 , respectively. The architecture of 2 is elaborated with two compartments that can accommodate two units of fluoride, chloride, or bromide ions, one in each of the enclosures. However, the entry of iodide is altogether restricted. Complexes 1 and 2 are interconvertible under suitable conditions.     

Synthesis and Conformational Analysis of 1′‐ and 3′‐Substituted 2‐Deoxy‐2‐fluoro‐D‐ribofuranosyl Nucleosides

Convergent syntheses of the 9‐(3‐X‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranosyl)adenines 5 (X=N₃) and 7 (X=NH₂), as well as of their respective α‐anomers 6 and 8 , are described, using methyl 2‐azido‐5‐O‐benzoyl‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranoside ( 4 ) as glycosylating agent. Methyl 5‐O‐benzoyl‐2,3‐dideoxy‐2,3‐difluoro‐β‐D ‐ribofuranoside ( 12 ) was prepared starting from two precursors, and coupled with silylated N⁶‐benzoyladenine to afford, after deprotection, 2′,3′‐dideoxy‐2′,3′‐difluoroadenosine ( 13 ). Condensation of 1‐O‐acetyl‐3,5‐di‐O‐benzoyl‐2‐deoxy‐2‐fluoro‐β‐D ‐ribofuranose ( 14 ) with silylated N²‐palmitoylguanine gave, after chromatographic separation and deacylation, the N⁷‐β‐anomer 17 as the main product, along with 2′‐deoxy‐2′‐fluoroguanosine ( 15 ) and its N⁹‐α‐anomer 16 in a ratio of ca. 42 : 24 : 10. An in‐depth conformational analysis of a number of 2,3‐dideoxy‐2‐fluoro‐3‐X‐D ‐ribofuranosides (X=F, N₃, NH₂, H) as well as of purine and pyrimidine 2‐deoxy‐2‐fluoro‐D ‐ribofuranosyl nucleosides was performed using the PSEUROT (version 6.3) software in combination with NMR studies.     

Synthesis and Structural Characterization of Three New Inorganic ＂Host-gues＂ Polyoxomolybdates

Since two interesting inorganic “host‐guest” polyoxomolybdates 1 and 2 have been reported previously, we have now succeeded in selectively isolating three new acetated “host‐guest” polyoxomolybdates 3–5, which considerably extend the range of structures in the cyclic polyoxomolybdate catalogue. 3 crystallizes in the triclinic space group P‐1 with a = 1.22235(1) nm, b = 1.52977(2) nm, c = 1.54022(1) nm, a = 113.746(1)°, β = 96.742(1)°, γ = 101.564(1)°, V = 2.51892(4) nm³, Z =1, D_c = 2.568 g. cm^?3. 4 and 5 crystallize in the monoclinic system: P2(1)/n, a = 1.08298(2) nm, b = 1.54029(1) nm, c = 2.78893(5) nm, β =94.2730(10)°, V = 4.63929(12) nm³, Z = 2 and D_c = 2.671 g. cm^?3 for 4, and C2/c, a =2.59907(8) nm, b = 1.65992(3) nm, c = 2.28473(7) nm, β‐93.4370(10)°, V = 9.8392(5) nm³, Z = 4 and D_c = 2.556 g. cm^?3 for 5. The structures of 3, 4 and 5 consist of 18‐membered “host‐guest” polyoxoanions [ Na (X)₂| ∈ |(μ_3‐OH)₄Mo^y₈Mo^VI₁₀52(μ₂‐CH₃COO)₂]^?(R+9 (X = CH₃COO^?for 3, DMF for 4 and H₂O for 5), which are connected via Na* ions or hydrogen bonds into infinite extended frameworks.     

Ion–Molecule Reactions of “Rollover” Cyclometalated [Pt(bipy−H)]+ (bipy=2,2′‐bipyridine) with Dimethyl Ether in Comparison with Dimethyl Sulfide: An Experimental/Computational Study

The ion–molecule reactions of dimethyl ether with cyclometalated [Pt(bipy?H)]⁺ were investigated in gas‐phase experiments, complemented by DFT methods, and compared with the previously reported ion–molecule reactions with its sulfur analogue. The initial step corresponds in both cases to a platinum‐mediated transfer of a hydrogen atom from the ether to the (bipy?H) ligand, and three‐membered oxygen‐ and sulfur‐containing metallacycles serve as key intermediates. Oxidative C? C bond coupling (“dehydrosulfurization”), which dominates the gas‐phase ion chemistry of the [Pt(bipy?H)]⁺ ion with dimethyl sulfide, is practically absent for dimethyl ether. The competition in the formation of C₂H₄ and CH₂X (X=O, S) in the reactions of [Pt(bipy?H)]⁺ with (CH₃)₂X (X=O, S) as well as the extensive H/D exchange observed in the [Pt(bipy?H)]⁺/(CH₃)₂O system are explained in terms of the corresponding potential‐energy surfaces.     

Design,synthesis, and self‐assembly manipulating of polymerized ionic liquids contained imidazolium based on “Jacketing” effect

A series of novel polymerized ionic liquids (PILs) contained imidazolium, poly (2,5‐bis{[6‐(1‐butyl‐3′‐imidazolium)hexyl] oxy carbonyl}styrene salts) (denoted as P1? X^?, X^??Br^?, BF₄^?, PF₆^? and TFSI^?) were successfully synthesized via radical polymerization. The chemical structures of the monomers and their corresponding PILs were confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared spectroscopy. Thermogravimetric analysis results showed that these PILs had excellent thermal stability. The phase transitions and liquid‐crystalline (LC) behaviors of these polymers were investigated by differential scanning calorimetry, polarized light microscopy (PLM), and wide‐angle X‐ray diffraction. The combined experimental results showed that all the PILs could form hexagonal columnar (?H) LC ordered structures because of the strong interaction between the anions and cations in the side groups except for P1? TFSI^?. The conductivities of monomers and PILs were sketchily investigated, and monomers had higher conductivities than those of conprespoding PILs. For comparison, we have synthesized a polymer without counter‐anion, but similar to the chemical structure of P1? X^?, poly (2, 5‐bis{[6‐(4‐butoxy‐4′‐oxy phenyl) hexyl] oxycarbonyl} styrene) (denoted as P2). In this case, phenyl took place of imidazolium of side chain, and LC ordered structure did not form. The comparison between P1? X^? and P2 suggested that ion played an important role in the constructing of LC ordered structure. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

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 ).     

Highly Dynamic Coordination Behavior of Pn Ligand Complexes towards “Naked” Cu+ Cations

Reactions of Cu⁺ containing the weakly coordinating anion [Al{OC(CF₃)₃}₄]^? with the polyphosphorus complexes [{CpMo(CO)₂}₂(μ,η²:η²‐P₂)] ( A ), [CpM(CO)₂(η³‐P₃)] (M=Cr( B1 ), Mo ( B2 )), and [Cp*Fe(η⁵‐P₅)] ( C ) are presented. The X‐ray structures of the products revealed mononuclear ( 4 ) and dinuclear ( 1 , 2 , 3 ) Cu^I complexes, as well as the one‐dimensional coordination polymer ( 5 a ) containing an unprecedented [Cu₂( C )₃]²⁺ paddle‐wheel building block. All products are readily soluble in CH₂Cl₂ and exhibit fast dynamic coordination behavior in solution indicated by variable temperature ³¹P{¹H} NMR spectroscopy.     

11‐Vertex arachno‐Clusters with an NB10, SNB9, and SeNB9 Skeleton

One of the two bridging protons of the aza‐nido‐decaboranes RNB₉H₁₀X can be removed by certain bases to give nido‐anions [RNB₉H₉X]^– [R/X = H/H ( 1 a ), Ph/H ( 1 b ), p‐MeC₆H₄/H ( 1 c ), Bzl/H ( 1 d ), H/N₃ ( 1 ′ a )]; the stericly demanding base 1,8‐bis(dimethylamino)naphthalene (“proton sponge”, ps) is ideal. In the case of tBu anion, the deprotonation (→ C₄H₁₀) may be accompanied by a hydridation (→ C₄H₈), yielding the arachno‐anions [RNB₉H₁₁X]^– ( 2 a , b , d , 2 ′ a ); these are the main products, when stericly non‐demanding bases like H^– are applied. The Lewis acid BH₃ is added to 1 a and 1 ′ a to give the aza‐arachno‐undecaborates HNB₁₀H₁₂X [X = H ( 3 a ), N₃ (in position 2) ( 3 ′ a )]. Thia‐ and selenaaza‐arachno‐undecaborates, [S(RN)B₉H₁₀]^– ( 4 b , c ) and [Se(RN)B₉H₁₀]^– ( 4 ′ b , c ), are obtained from 1 b , c by the addition of sulfur or selenium, respectively. The methylation of the anions 4 c and 4 ′ c gives the thia‐ and selenaazaarachno‐undecaboranes (MeS)(RN)B₉H₁₀ ( 5 c ) and (MeSe)(RN)B₉H₁₀ ( 5 ′ c ), respectively. The action of HBF₄ on the arachno‐borates [HNB₁₀H₁₂X]^– ( 3 a , 3 ′ a ) leads to a mixture of nido‐HNB₉H₁₀X and nido‐HNB₁₀H₁₁X by the elimination of BH₃ or H₂, respectively; the aza‐nido‐decaborane predominates in the case of 3 ′ a and the aza‐nido‐undecaborane in the case of 3 a . The action of HBF₄ on the anion 4 c yields the hypho‐undecaborate [S(RN)B₉H₁₀F₂]^– ( 6 c ). The structures of the products are elucidated on the basis of ¹H and ¹¹B NMR spectra, supported by 2D COSY and HMQC techniques. Two types of 11‐vertex‐arachno structures and an 11‐vertex‐hypho structure are found for the products. The crystal structures of 5 c and [Hps] 6 c · CH₂Cl₂ are reported.     

Ruthenium Complex “Light Switches” that are Selective for Different G‐Quadruplex Structures

Recognition and regulation of G‐quadruplex nucleic acid structures is an important goal for the development of chemical tools and medicinal agents. The addition of a bromo‐substituent to the dipyridylphenazine (dppz) ligands in the photophysical “light switch”, [Ru(bpy)₂dppz]²⁺, and the photochemical “light switch”, [Ru(bpy)₂dmdppz]²⁺, creates compounds with increased selectivity for an intermolecular parallel G‐quadruplex and the mixed‐hybrid G‐quadruplex, respectively. When [Ru(bpy)₂dppz‐Br]²⁺ and [Ru(bpy)₂dmdppz‐Br]²⁺ are incubated with the G‐quadruplexes, they have a stabilizing effect on the DNA structures. Activation of [Ru(bpy)₂dmdppz‐Br]²⁺ with light results in covalent adduct formation with the DNA. These complexes demonstrate that subtle chemical modifications of Ru^II complexes can alter G‐quadruplex selectivity, and could be useful for the rational design of in vivo G‐quadruplex probes.     

Pseudohalide‐directed Assembly of Two Zinc(II) Coordination Polymers with a 3,4‐Bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole Tecton

The zinc(II) pseudohalide complexes {[Zn(L³³⁴)(SCN)₂(H₂O)](H₂O)₂}_n ( 1 ) and [Zn(L³³⁴)(dca)₂]_n ( 2 ) were synthesized and characterized using the ligand 3,4‐bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole (L³³⁴) and ZnCl₂ in presence of thiocyanate (SCN^–) and dicynamide [dca, N(CN)₂^–] respectively. Single‐crystal X‐ray structural analysis revealed that the central Zn^II atoms in both complexes have similar octahedral arrangement. Compound 1 has a 2D sheet structure bridged by bidentate L³³⁴ and double μ_N,S‐thiocyanate anions, whereas complex 2 , incorporating with two monodentate dicynamide anions, displays a two‐dimensional coordination framework bridged by tetradentate L³³⁴ ligand. Structural analysis demonstrated that the influence of pseudohalide anions plays an important role in determining the resultant structure. Both complexes were characterized by IR spectroscopy, microanalysis, and powder X‐ray diffraction techniques. In addition, the solid fluorescence and thermal stability properties of both complexes were investigated.     

A Nontrigonal Tricoordinate Phosphorus Ligand Exhibiting Reversible “Nonspectator” L/X‐Switching

We report here a “nonspectator” behavior for an unsupported L ‐function σ³‐P ligand (i.e. P{N[o‐NMe‐C₆H₄]₂}, 1a ) in complex with the cyclopentadienyliron dicarbonyl cation (Fp⁺). Treatment of 1a ?Fp⁺ with [(Me₂N)₃S][Me₃SiF₂] results in fluoride addition to the P‐center, giving the isolable crystalline fluorometallophosphorane 1a^F ?Fp that allows a crystallographic assessment of the variance in the Fe?P bond as a function of P‐coordination number. The nonspectator reactivity of 1a ?Fp⁺ is rationalized on the basis of electronic structure arguments and by comparison to trigonal analogue (Me₂N)₃P?Fp⁺ (i.e. 1b ?Fp⁺), which is inert to fluoride addition. These observations establish a nonspectator L/X‐switching in (σ³‐P)–M complexes by reversible access to higher‐coordinate phosphorus ligand fragments.     

Fullerene “Superhalogen” Radicals: the Substituent Effect on Electronic Properties of 1,7,11,24,27‐C60X5

Hexasubstituted fullerenes with the skew pentagonal pyramid (SPP) addition pattern are predominantly formed in many types of reactions and represent important and versatile building blocks for supramolecular chemistry, biomedical and optoelectronic applications. Regioselective synthesis and characterization of the new SPP derivative, C₆₀(CF₃)₄(CN)H, in this work led to the experimental identification of the new family of “superhalogen fullerene radicals”, species with the gas‐phase electron affinity higher than that of the most electronegative halogens, F and Cl. Low‐temperature photoelectron spectroscopy and DFT studies of different C₆₀X₅ radicals reveal a profound effect of X groups on their electron affinities (EA), which vary from 2.76 eV (X=CH₃) to 4.47 eV (X=CN). The measured gas‐phase EA of the newly synthesized C₆₀(CF₃)₄CN equals 4.28 (1) eV, which is about 1 eV higher than the EA of Cl atom. An observed remarkable stability of C₆₀(CF₃)₄CN^? in solution under ambient conditions opens new venues for design of air‐stable molecular complexes and salts for supramolecular structures of electroactive functional materials.     

Selective Detection of Multicarboxylate Anions based on “Turn on” Electron Transfer by Self‐Assembled Molecular Rectangles

Two new large molecular rectangles ( 4 and 5 ) were obtained by the reaction of two different dinuclear arene ruthenium complexes [Ru₂(arene)₂(O O)₂Cl₂] (arene=p‐cymene; O O=2,5‐dihydroxy‐1,4‐benzoquinonato ( 2 ), 6,11‐dihydroxy‐5,12‐naphthacene dionato ( 3 )) with the unsymmetrical amide (N‐[4‐(pyridin‐4‐ylethynyl)phenyl]isonicotinamide) donor ligand 1 in methanol in the presence of AgO₃SCF₃, forming tetranuclear cations of the general formula [Ru₄(arene)₄( )₂(O O)₂]⁴⁺. Both rectangles were isolated in good yields as triflate salts and were characterized by multinuclear NMR, ESI‐MS, UV/Vis, and photoluminescence spectroscopy. The crystal structure of 5 was determined by X‐ray diffraction. Luminescent rectangle 5 was used for anion sensing with an amide ligand as a hydrogen‐bond donor and an arene–ruthenium acceptor as a signaling unit. Rectangle 5 strongly bound multicarboxylate anions, such as oxalate, tartrate, and citrate, in UV/Vis titration experiments in 1:1 ratios, in contrast to monoanions, such as F^?, Cl^?, NO₃^?, PF₆^?, CH₃COO^?, and C₆H₅COO^?. The fluorescence titration experiment showed a large fluorescence enhancement of 5 upon binding to multicarboxylate anions, which could be attributed to blocking of the photoinduced electron transfer process from the arene–ruthenium moiety to the amidic donor in 5 ; this was likely to be a result of hydrogen bonding between the ligand and the anion. On the other hand, rectangle 5 was not selective towards any other anions. To the naked eye, multicarboxylate anions in a solution of 5 in methanol appear greenish upon irradiation with UV light.     

Synthesis and characterization of three dinuclear copper(I) complexes of 1,2‐bis(diphenylphosphino)‐1,2‐dicarba‐closo‐dodecaborane

Three dinuclear copper(I) complexes, [Cu₂(µ‐Cl)₂(1,2‐(PPh₂)₂‐1,2‐C₂B₁₀H₁₀)₂]·2CH₂Cl₂ ( 1 ), [Cu₂(µ‐Br)₂(1,2‐(PPh₂)₂‐1,2‐C₂B₁₀H₁₀)₂]·2THF ( 2 ) and {Cu₂(µ‐I)₂[1,2‐(PPh₂)₂‐1,2‐C₂B₁₀H₁₀]₂} ( 3 ) have been synthesized by the reactions of CuX (X = Cl, Br and I) with the closo ligand 1,2‐(PPh₂)₂‐1,2‐C₂B₁₀H₁₀. All these complexes were characterized by elemental analysis, FT‐IR, ¹H and ¹³C NMR spectroscopy and X‐ray structure determination. Single crystal X‐ray structure determinations show that every complex contained di‐µ‐X‐bridged structure involving a crossed parallelogram plane formed by two Cu atoms and two X atoms (X = Cl, Br, I). The geometry at the Cu atom was a distorted tetrahedron, in which two positions were occupied by two P atoms of the PPh₂ groups connected to the two C atoms of carborane (Cc), and the other two resulted from two X atoms which bridged the other Cu atom at the same time. To the best of our knowledge, this is the first example of copper(I) complexes with 1,2‐diphenylphosphino‐1,2‐dicarba‐closo‐dodecaborane as ligand characterized by X‐ray diffraction. The catalytic property of the complex 3 for the amination of iodobenzene with aniline was also investigated. Copyright © 2005 John Wiley & Sons, Ltd.     

Anion‐directed Silver(I) Coordination Assemblies Based on 1‐(2‐Pyridyl)‐2‐(4‐pyridyl)‐1,2,4‐triazolewith Diverse Supramolecular Networks and Dichromate Removal Capabilities

A series of silver(I) supramolecular complexes, namely, {[Ag(L²⁴)](NO₃)}_n ( 1 ), [Ag₂(L²⁴)(NO₂)₂]_n ( 2 ), and {[Ag_1.25(L²⁴)(DMF)](PF₆)_1.25}_n ( 3 ) were prepared by the reactions of 1‐(2‐pyridyl)‐2‐(4‐pyridyl)‐1,2,4‐triazole (L²⁴) and silver(I) salts with different anions (AgNO₃, AgNO₂, AgPF₆). Single‐crystal X‐ray diffraction indicates that 1 – 3 display diverse supramolecular networks. The structure of dinuclear complex 1 is composed of a six‐membered Ag₂N₄ ring with the Ag ··· Ag distance of 4.4137(3) Å. In complex 2 , the adjacent Ag^I centers are interlinked by L²⁴ ligands into a 1D chain, the adjacent of which are further extended by the bridged nitrites to construct a 2D coordination architecture. Complex 3 shows a 3D (3,4)‐connected framework, which is generated by the linkage of L²⁴ ligands. All complexes were characterized by IR spectra, elemental analysis, and powder X‐ray diffraction. Notably, a structural comparison of the complexes demonstrates that their structures are predominated by the nature of anions. Additionally, 1 and 2 show efficient dichromate (Cr₂O₇^2–) capture in water system, which can be ascribed to the anion‐exchange.     

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.     

Strontium Vanadium Oxide–Hydrides: “Square‐Planar” Two‐Electron Phases

A series of strontium vanadium oxide–hydride phases prepared by utilizing a low‐temperature synthesis strategy in which oxide ions in Sr_n+1V_nO_3n+1 (n=∞, 1, 2) phases are topochemically replaced by hydride ions to form SrVO₂H, Sr₂VO₃H, and Sr₃V₂O₅H₂, respectively. These new phases contain sheets or chains of apex‐linked V³⁺O₄ squares stacked with SrH layers/chains, such that the n=∞ member, SrVO₂H, can be considered to be analogous to “infinite‐layer” phases, such as Sr_1?xCa_xCuO₂ (the parent phase of the high‐T_c cuprate superconductors), but with a d² electron count. All three oxide–hydride phases exhibit strong antiferromagnetic coupling, with SrVO₂H exhibiting an antiferromagnetic ordering temperature, T_N>300 K. The strong antiferromagnetic couplings are surprising given they appear to arise from π‐type magnetic exchange.