Ferromagnetic mixed tribridged dinuclear copper(II) complex [Cu2(OAc)2(OH)(dpa)2]PF6 · H2O (dpa = 2,2′-dipyridylamine): 3D superstructure based on hydrogen bond and π…π interaction

A new dinuclear complex [Cu₂(OAc)₂(OH)(dpa)₂] PF₆ · H₂O (1) is prepared and structurally and magneto-structurally characterized. The monocationic core contains one acetate in familiar bidentate η¹:η¹:μ₂-bridge and another in the rare monoatomic bridge along with one hydroxo intermediary. 1 packs through N–H…O and O–H…O hydrogen bonds and π…π interaction resulting a 3D supramolecular continuum and displays high-energy intraligand ¹(π − π^*) fluorescence and intraligand ³(π − π^*) phosphorescence in glassy solution.     

Self-assembly of organometallic Pd(II) complexes via CH3π interactions: The first example of a cyclopalladated compound with herringbone stacking pattern

Two binuclear cyclometallated compounds [Pd(C²,N-dmba)(μ-N₃)]₂ (1) and [Pd₂(C²,N-dmba)₂(μ-N₃)(μ-Cl)] (2) (dmba = N,N-dimethylbenzylamine) have been synthesized and characterized by elemental analysis, IR and NMR spectroscopies and single crystal X-ray diffraction crystallography. The ability of CH₃ groups to form C(sp³)Hπ hydrogen bonds with phenyl rings is responsible for the molecular self-assembly within the crystals of 1 and 2. Compound 1 crystallizes as one-dimensional supramolecular chains whereas the crystal packing of 2 consists of a herringbone of sandwiches composed by two inversely related [Pd₂(C²,N-dmba)₂(μ-N₃)(μ-Cl)] molecules.     

An easy entry to novel early–late oligonuclear transition metal complexes containing π-conjugated systems

Heterotrinuclear Ti–Cu–Ru (5) and heterotetranuclear Ti–Cu–Pt–Fe (7) containing complexes are accessible by using {[Ti](CC^tBu)₂}CuMe (1) ([Ti]=(η⁵-C₅H₄SiMe₃)₂Ti) as key molecule; in 5 and 7, the corresponding early and late transition metal atoms are linked by π-conjugated organic moieties.     

Two novel Zn(II) coordination polymers based on trigonal ligand: 4′-(4-pyridyl)-3,2′:6′,3″-terpyridine

Two novel Zn(II) coordination polymers, [Zn₅(pytpy)₈(fum)₄(H₂O)₄(OH)₂]_n · n(CH₃OH) · 2n(H₂O) (1) and [Zn₃(pytpy)₄ (btc)₂]_n · 2n(H₂O) (2) (pytpy = 4′-(4-pyridyl)-3,2′:6′,3″-terpyridine, H₂fum = fumaric acid, H₃btc = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized and structurally characterized. Complex 1 is a 2D layer structure, which is constructed from linear pentanuclear Zn(II) subunits interconnected via bidentate-bridging pytpy ligands and tridentate-bridging fum²⁻ anions. Complex 2 is a 3D network structure, μ₂-pytpy ligands link the layers based on the heart-like hexanuclear subunits to form the 3D network. Both complexes show strong fluorescence emission upon excitation at 310 nm in solid state. Additionally, these two complexes possess great thermal stabilities, especially for 2, the framework is stable up to 350 °C.     

Controllable assembly of a 3-D metal–organic supramolecular framework with the inclusion of a well-resolved 1-D water morph

Two mixed-ligand metal–organic complexes [Cd₂(adipato)(phen)₂(NO₃)₂(H₂O)₂](H₂O)₆ (1) and {[Cd(adipato)(phen)](H₂O)₃}_n (2) have been synthesized upon the reaction of Cd(II) nitrate with 1,10-phenanthroline (phen) and adipate under similar conditions. For 1, the adipato-bridged dinuclear entities are extended into a 3-D supramolecular architecture via hydrogen bonds and π–π stacking. Interestingly, a well-resolved 1-D water morphology consisting of alternate cyclic water tetramer and hexamer is detected as the guests in each channel of this 3-D lattice. Whereas 2 represents a layered coordination polymer in which the Cd^II centers are interlinked by adipate dianions via different coordination modes.     

Ditopic, flexible hydrazone-based building blocks with pendant 2,2′:6′,2′′-terpyridine metal-binding domains

The synthesis and characterization of three new bis(2,2′:6′,2′-terpyridine) (tpy) ligands containing different hydrazone spacers between the metal-binding domains are described. Treatment of 1,4-benzenedicarbaldehyde bis(2,2′:6′,2′′-terpyridin-4′-ylhydrazone) (1) with [(tpy)RuCl₃] in the presence of N-ethylmorpholine results in the formation of [(tpy)Ru(μ-1)Ru(tpy)]⁴⁺. Single crystal X-ray diffraction data for [(tpy)Ru(μ-1)Ru(tpy)][PF₆]₄·8MeCN confirm the ability of the hydrazone-based ligand to bridge two ruthenium(II) centres, providing proof-of-principle for the application of this class of flexible ligand in the design of coordination polymers.     

Synthesis of onion-like mesoporous silica from sodium silicate in the presence of α,ω-diamine surfactant

Mesoporous silicas with vesicular and onion-like morphologies were assembled through hydrogen-bonding pathway from sodium silicate as silica source and electrically neutral α,ω-diamine, Jeffamine D2000 surfactant (H₂NCH(CH₃)CH₂[OCH₂CH(CH₃)]₃₃NH₂) as template in aqueous media at different synthesis temperatures (25, 60 and 100 °C). Assembling the material at 100 °C afforded onion-like core shell mesoporous silica, while at relatively lower temperature, e.g. 25 and 60 °C, multilamellar vesicles were obtained. Mesoporous silica with onion-like morphology was also obtained by a two-step synthesis involving an aging period of 20 h at room temperature followed by a hydrothermal stage (1–12 h) at 100 °C. The heavily cross-linked (Q⁴/Q³ ratio of 4.43) onion-like mesophase silica exhibited high hydrothermal stability. The BET surface area, pore volume and KJS (Kruk-Jaroniec-Sayari) pore diameter of the onion-like mesoporous silica were found to be 464 m² g⁻¹, 1.16 m³ g⁻¹ and 7.2 nm, respectively.     

New (κ-C,N)-palladacyclic complexes with benzimidazol-2-ylidene ligand: Synthesis, crystal structures and characterization

Reaction of unsymmetrical benzimidazolium bromides (1) with Ag₂O and subsequent transmetallation with chloro-bridged dinuclear palladacycle, [Pd(dmba)(μ-Cl)]₂ (dmba: N,N-dimethylbenzylamine) afforded benzannulated monocarbene complexes [Pd(dmba)(NHC)Cl], 2. The palladacycles (2a–c) were characterized by elemental analysis; NMR spectroscopy and the molecular structure of 2a and 2c were determined by X-ray crystallography.     

Propellanes as Rigid Scaffolds for the Stereodefined Attachment of σ-Pharmacophoric Structural Elements to Achieve σ Affinity

Following the concept of conformationally restriction of ligands to achieve high receptor affinity, we exploited the propellane system as rigid scaffold allowing the stereodefined attachment of various substituents. Three types of ligands were designed, synthesized and pharmacologically evaluated as σ₁ receptor ligands. Propellanes with (1) a 2-methoxy-5-methylphenylcarbamate group at the “left” five-membered ring and various amino groups on the “right” side; (2) benzylamino or analogous amino moieties on the “right” side and various substituents at the left five-membered ring and (3) various urea derivatives at one five-membered ring were investigated. The benzylamino substituted carbamate syn,syn-4a showed the highest σ₁ affinity within the group of four stereoisomers emphasizing the importance of the stereochemistry. The cyclohexylmethylamine 18 without further substituents at the propellane scaffold revealed unexpectedly high σ₁ affinity (K_i = 34 nM) confirming the relevance of the bioisosteric replacement of the benzylamino moiety by the cyclohexylmethylamino moiety. Reduction of the distance between the basic amino moiety and the “left” hydrophobic region by incorporation of the amino moiety into the propellane scaffold resulted in azapropellanes with particular high σ₁ affinity. As shown for the propellanamine 18, removal of the carbamate moiety increased the σ₁ affinity of 9a (K_i = 17 nM) considerably. Replacement of the basic amino moiety by H-bond forming urea did not lead to potent σ ligands. According to molecular dynamics simulations, both azapropellanes anti-5 and 9a as well as propellane 18 adopt binding poses at the σ₁ receptor, which result in energetic values correlating well with their different σ₁ affinities. The affinity of the ligands is enthalpy driven. The additional interactions of the carbamate moiety of anti-5 with the σ₁ receptor protein cannot compensate the suboptimal orientations of the rigid propellane and its N-benzyl moiety within the σ₁ receptor-binding pocket, which explains the higher σ₁ affinity of the unsubstituted azapropellane 9a.     

Supramolecular π–π assembly of a neutral [Cu(salen)] complex via the templating effect of an ionic inorganic complex Na2[Cu(mnt)2] forming a framework type material having well-defined channels

A classical ionic inorganic complex Na₂[Cu(mnt)₂] (mnt²⁻ = maleonitriledithiolate = 1,2-dicyanoethylenedithiolate), that acts as a template in assembling neutral [Cu(salen)] (salen = bis(salicylidene)ethylenediamine) complexes forming a framework type arrangement, is accommodated in the channel formed in the crystal structure of a new type of host–guest compound [Cu(salen)]₄ · Na₂[Cu(mnt)₂] (1). The non-covalent supramolecular interactions among [Cu(salen)] complexes and between [Cu(salen)] and [Cu(mnt)₂]²⁻ complexes in the crystal lattice of 1 result in weak antiferromagnetic coupling.     

Synthesis and characterization of fluorine–thiophene-based π-conjugated polymers using coupling reaction

A solution processible fluorine–thiophene-based copolymers, namely poly[2,7-bis(4-octyl-2-thienyl)-9,9-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P1), poly[2,7-bis(3-octyl-2-thienyl)-9,9-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P2), poly[2,7-bis(3,3′-dioctyl-5,5′-bithien-2yl)-9,9′-dioctylfluorene-co-alt-5,5′-(2,2′-bithiophene)] (P3) were synthesized using Suzuki and Stille coupling reaction. The polymers showed weight loss starting around 400 °C indicative of good thermal stability. UV–vis properties and photoluminescence (PL) properties were investigated in toluene. P1, P2 and P3 exhibited the absorption maximum at 450, 428 and 435 nm and their PL spectrum peaked at 587, 559 and 560 nm, respectively. And all polymers, P1, P2 and P3, showed electroluminescence (EL) spectrum peaked at 592, 595 and 607 nm in the range of orange red. The polymers were electrochemically active in oxidation regions. P3 especially showed high oxidation stabilities in 1.17 V vs. Ag/Ag⁺. And P1 and P3 showed higher crystallinity than P2, because they have a repeated unit of 3,3-dialkyl-quaterthiophene.     

Two novel d frameworks based on a new V-shaped ligand 2,4′-dipyridylamine and a flexible dicarboxylate ligand

Via hydrothermal synthesis, the self-assembly of d¹⁰ metal, 2,4′-dipyridylamine (L) and 1,3-adamantanediacetic acid (H₂ADA) generated two unprecedented coordination polymers [Zn(ADA)(L)]_n (1) and [Cd(ADA)(L)₂]_n (2). Complex 1 possesses a novel 1D looped-chain topology structure decorated with arms. Complex 2 shows an extended threaded framework involving 2D coordination layers of square (4⁴) topology with dangling ligands, which gives the novel (2D → 3D) polythreaded array. To the best of our knowledge, complex 2 is the first example with four dangling arms coordinated in the axial sites of dinuclear nodes. In addition, both of the complexes show strong photoluminescence at room temperature, and may be good candidates for potential luminescence materials.     

A novel stair-like lithium coordination polymer constructed from 4,4′-bipyridine

A novel stair-like lithium coordination polymer Li₂(4,4′-bpy)₂(NO₃)₂, 1, has been synthesized by using standard Schlenk techniques. X-ray diffraction shows the 2D stair-like framework contains an approximately perpendicular 1D “Z” type Li-4,4′-bpy chain and an unprecedented Li–NO₃ chain.     

Magnetic behavior within a new Ni(mnt)2-based molecular solid containing 1-(2′-fluorobenzyl)isoquinolinium

A novel molecular solid, [OFBzIQl][Ni(mnt)₂] (1), where [OFBzIQl]⁺ = 1-(2′-fluorobenzyl)isoquinolinium and mnt²⁻ = maleonitriledithiolate, forms 1D column of alternating between cations and anions via ππ stacking interaction between Ni(mnt)₂ plane and isoquinoline ring, and the Ni(mnt)₂ anions between the adjacent columns exist short CN interaction. The extensive hydrogen bonds between anions and cations in the crystal generate a 2D network structure. Magnetic susceptibility measurement for 1 in the temperature range 2.0–300 K shows that 1 exhibits a magnetic constant transition from ferromagnetic to antiferromagnetic around 35 K as the temperature is lowered.     

A novel lamella 2D Ag(I) coordination polymer of graphite-like structure featuring short interlayer distance

The reaction of Ag₂O with a mixture of benzene-1,3,5-tricarboxylic acid (H₃BTC) and 2-aminopyrazine (APYZ) under the ammoniacal conditions gives rise to a novel metal–organic coordination polymer Ag₆(BTC)₂(APYZ)₆·9H₂O (1). The structure of 1 possesses a high ordered lamella 2D structure with an interesting graphite-like 6³ net which is comprised of Ag₄ and Ag₆ fused hexagonal rings respectively. 1 exhibits photoluminescence maximized at 416 nm upon 330 nm excitation at room temperature, which may be mainly ascribed to ligand-to-ligand charge transfer (LLCT). Semiconducting behavior was also measured at ambient temperature with σ values of 5.56 × 10⁻⁷ S cm⁻¹ based on the π–π stacking and Ag(I)–π interactions.     

Design and construction of two new polymers featuring macrocyclic subunits based on a rigid clamp-like ligand

Reaction of a rigid conjugated clamp-like ligand N,N′-bis(pyridin-3-yl)-2,6-pyridinedicarboxamide (bppdca) with ZnSO₄·7H₂O or CoSO₄·7H₂O resulted in the formation of two new polymers, namely, {[Zn₂(bppdca)(SO₄)₂(DMF)₂]·(DMF)}_n (1) and {[Co(bppdca)(SO₄)(CH₃OH)(DMF)]·H₂O}_n (2). Both 1 and 2 feature one-dimensional double-chain structures with macrocyclic subunits, and the chains further self-assemble into a higher-dimensional framework via the hydrogen-bonding and π–π stacking interactions. Fluorescence studies show that the free ligand displays a strong fluorescence emission in solid state at room temperature, but in 1 and 2, the complexation of the ligand with metal ions and weak intermolecular interactions make the fluorescence emission partial quenching.     

Polymer-polymer interaction parameters in the ternary system polystyrene/poly(α-methyl styrene)/n-butyl chloride

The polymer-polymer interaction parameter χ′12, for the polystyrene/poly(α-methyl styrene)/n-butyl chloride ternary system, has been determined from activity coefficients of the solution measured using piezoelectric vapour sorption methods in the temperature range 30°–60°C. (These measurements where carried out in the concentration range 0.06 < ψ₀ < 0.26, where ψ is the segment fraction of the solvent). The values of χ¹⁰₁₂ extrapolated to zero solvent concentration over the range 30°–60°C, are large and negative (−0.2 to −0.9) χ¹₁₂ was found to increase with ψ₀. The negative values of χ¹₁₂ in this work are in agreement with the T_g in the polystyrene

Full-size image (1K)

M_w = 9.09 × 10⁴) blends on the point of blend compatibility. The polymer-polymer interaction parameters obtained in this work are discussed by taking into account the high susceptibility of polymers in the glassy state to solution of organic solvents.     

The structural characterization and hydroformylation activity of the tri-rhodium complex [Rh3(μ2-dppm)2(μ2-CO)3(K-CO)3]BF4

Rh₂(cod)₂(μ₂-dppm)(μ₂-Cl)]BF₄ (1) rearranges under carbon monoxide to give [Rh₃(μ₂-dppm)₂(μ₂-CO)₃(K¹-CO)₃]BF₄ (2). Complex 2 has been structurally characterized by single crystal X-ray crystallography. The hydroformylation activities of 1 and 2 were compared for substrates styrene and 1-hexene and the activity of 2 found to be unexpectedly high.     

Oxidation of catechol and l-ascorbic acid by [Ru(tpy)(pic)(OH)] (tpy = 2,2′6′,2″-terpyridine; pic = picolinate): Kinetic and mechanistic studies

Kinetics of oxidation of catechol (H₂cat) to benzoquinone (BQ) and, ascorbate (HA⁻) to dehydroascorbic acid (A) by [Ru^III(tpy)(pic)(OH)]⁺ (1) (tpy = 2,2’6’,2”-terpyridine; pic⁻ = picolinate) have been studied as function of [H₂cat] (or [HA⁻]), ionic strength (0.01 − 0.25 M), temperature (10–30 °C) at a constant pH = 3.2, using stopped-flow and rapid-scan diode array spetrophotometric techniques. The rate of reaction of 1 with HA⁻ was found to be very fast as compared to that of with H₂cat. The kinetic data and activation parameters are interpreted in terms of an associative interchange mechanism. Analysis of spectral and kinetic data revealed that the reaction of 1 with catechol proceeds by a straightforward outer-sphere electron transfer pathway, whereas, reduction of 1 with HA⁻ involves ion-pair formation.     

The dipeptide H-Aib-l-Ala-OH ligand in copper(II) chemistry: Variation of product identity as a function of pH

A systematic investigation of the influence of “pH” on the product identity from the Cu^II/H-Aib-l-Ala-OH (LH) reaction system is described, where H-Aib-l-Ala-OH is α-aminoisobutyryl-l-alanine. The pH variation has led to the synthesis of two discrete complexes, the structures of which have been determined by single-crystal X-ray crystallography. The “low pH” complex {[CuClL](H₂O)_2.5}_n (1) is a 3D coordination polymer, in which the dipeptide monoanion L⁻ behaves as a η¹:η¹:η¹:μ₂ ligand binding one Cu^II atom through its amino nitrogen and neutral peptide oxygen, and an adjacent Cu^II atom through one of its carboxylate oxygen. The “higher pH” complex {[Cu(H₋₁L)(EtOH)](EtOH)}_n (2) is a chain (1D) compound, in which the dipeptide dianion H₋₁L²⁻ uses its amino nitrogen, deprotonated peptide nitrogen and both carboxylate oxygens to bridge two metal centres.