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A new tridentate and rigid ligand containing S,N-hetero donor, the 1H-1,8-naphthyridine-2-thione (Hnpt), is designed and developed to build up the first homonuclear nickel string supported by the m...

This paper proposes a novel μ-hydroxo-bridged dinuclear macrocyclic zinc complex, {[Zn(C10H20N8)]2(OH)}(BF4)3. The structure was determined by X-ray crystallography: Monoclinic, C2/c, a = 25.4632(6), b = 10.9818(3), c = 15.7522(4) A, Z = 8, R1 = 0.0233, wR2 = 0.0557, based on reflections I > 2σ(I). The complex was successfully reacted with graphene oxide to form a μ-hydroxo-bridged dinuclear macrocyclic Zn complex/reduced graphene oxide composite. To evenly disperse the Zn- and N-rich complex onto the surface of the reduced graphene oxide, and to enhance the electrocatalytic property of the graphene composites, a soluble molecular grafting method was used here. The graphene-based composites were applied as the counter electrodes (CEs) of dye-sensitized solar cells. Current density–voltage measurements revealed that the conversion efficiency of the GO/Zn (1 : 10) sample was 7.78%, which was better than that of Pt CE (7.49%). GO/Zn (1 : 10) CE exhibited the lowest impedance (RCE = 9.90 Ω), which was better than that of Pt CE (RCE = 66.1 Ω), showing that GO/Zn CEs can reduce the impedance at the CE/electrolyte interface. The proposed method is simple, and the composite materials can potentially replace conventional Pt, optimizing efficiency and reducing production cost.

Synthesis of the multidentate coordinated chelate N3C–H2, composed of a linked functional pyridyl pyrazole fragment plus a peripheral phenyl and pyridyl unit, was obtained using a multistep protoco...

The [3 + 2] cycloaddition reactions of a series of ynoate esters with a ruthenium azido complex [Ru]−N 3 ( 1 , [Ru] = ( η 5 -C 5 H 5 )(dppe)Ru, dppe = Ph 2 PCH 2 CH 2 PPh 2 ) were investigated. The reaction products, metal-bound heterocyclic complexes such as the triazolato complexes [Ru]N 3 C 2 (CO 2 Et) 2 ( 2 ), [Ru]N 3 C 2 (CO 2 Et)(CF 3 ) ( 3 ), [Ru]N 3 C 2 (CO 2 Me)(Ph) ( 4 ) and [Ru]N 3 C 2 (CO 2 Et)(CH 3 ) ( 5 ) were produced from diethyl acetylene dicarboxylate, ethyl 4,4,4-trifluoro-2-butynoate, methyl phenylpropiolate and ethyl 2-butynoate, respectively. The complexes were all structurally characterized as being N(2)-bound. The alkylation of 2 with organic halides resulted in the cleavage of the Ru−N bond and the formation of a series of 1-alkylated-4,5-bis(ethoxycarbonyl)-1,2,3-triazoles N 3 (CH 2 R)C 2 (CO 2 Et) 2 ( 6a , R = H; 6b , R = C 6 F 5 ; 6c , R = Ph; 6d , R = 4-CH 2 Br-C 6 H 4 ; 6e , R = 4-CN-C 6 H 4 ). The high regioselective alkylation of 4 with organic halides gave a 1-alkylated-4-phenyl-5-methoxycarbonyl-1,2,3-triazoles N 3 (CH 2 C 6 F 5 )C 2 (Ph)(CO 2 Me) ( N 3 - 7a ). The structures of complexes 2 , 3 , 4 , 5 and N 3 - 7a were confirmed by single-crystal X-ray diffraction analysis.

The [3 + 2] cycloaddition of two acetylacetylenes with ruthenium azido complex [Ru]−N3 (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) is reported. The metal-bound heterocyclic complexes produced are triazolato complexes [Ru]N3C2H(COCH3) (2) and [Ru]N3C2(Ph)(COCH3) (3) from 3-butyn-2-one and 4-phenyl-3-butyn-2-one, respectively. Both of the structures of 2 and 3 are clearly established as N(2)-bound. Alkylation of 2 with organic halides affords a series of N(1)-bound N(3)-alkyl-4-acetyl triazolato complexes {[Ru]N3(CH2R)C2H(COCH3)}[X] (4a, R = H, X = I; 4b, R = C6F5, X = Br; 4c, R = Ph, X = Br; 4d, R = 2,6-F2-C6H3, X = Br; 4e, R = 4-CN-C6H4, X = Br). Treatment of 4a with CH3I in refluxing CHCl3 afforded [Ru]-I (5). The structures of complexes 2, 3, 4a and 5 have been determined by single-crystal X-ray diffraction analysis.

Anionic nitrogen heterocyclic carbene complexes of C,N-bound mercuramacrocycles {Hg4Cl4(R-Bim)4} (BimH = benzimidazole; R = Ph, Py) were prepared either from the simple reaction of N-substituted benzimidazoles with HgCl2 or from the reaction of N-substituted benzimidazoles with Hg(OAc)2 and NaCl. The former reaction is unique as no additional base is required, although in low reaction yield. Under similar reaction conditions, only N-bound benzimidazole complexes were obtained when HgBr2 or HgI2 instead of HgCl2 was employed. The different reactivity could be due to the hard-soft acid-base property of mercury(II) and halides, that facilitates the cleavage of Hg-Cl bond and promotes the C-metallation of HgCl2 and benzimidazole. Upon protonation of {Hg4Cl4(R-Bim)4} with HBF4⋅OEt2, NH,NR-NHC complexes of [HgCl(R-Bim-H)][BF4] (R = Ph, Py) were obtained. Preliminary study on the transmetallation reaction of {Hg4Cl4(Ph-Bim)4} with PdCl2(CH3CN)2 and LiCl did provide a C,N-bound NHC palladium complex.

The alkylation of the N(2)-bound ruthenium triazolate [Ru]N3C2HCO2Et (2, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with benzylbromides is reported. The regiospecific alkylation of 2, which results from the [3 + 2] cycloaddition of ethyl propiolate with [Ru]-N3 (1), gives a series of cationic N(1)-bound N(3)-alkylated-4-ethoxycarbonyl triazolato complexes {[Ru]N3(CH2R)C2HCO2Et}[Br] (3a, R = 4-CH2Br-C6H4; 3b, R = 3,5-(CH2Br)2-C6H3; 3c, R = 2,6-F2-C6H3; 3d, R = 4-CN-C6H4) and the subsequent cleavage of the Ru-N bond of 3a-3d gives N(1)-alkylated-5-ethoxycarbonyl triazoles N3(CH2R)C2HCO2Et (4a-4d) and [Ru]-Br, which, on reacting with sodium azide, would afford [Ru]-N3 (1) thus forming a reaction cycle. The treatment of {[Ru]N3(CH2C6F5)C2HCO2Et}[Br] (3e) with sodium azide in refluxing ethanol gives the free triazole N3(CH2C6F5)C2HCO2Et (4e) and 1. The treatment of 2 with an equivalent of 3a affords a dinuclear bis(triazolato) complex {α,α'-bis([Ru]N3C2HCO2Et)-p-xylene}[Br]2 (5) and an organic bis(triazole) complex α,α'-bis(N3C2HCO2Et)-p-xylene (6). The treatment of 2 with CF3COOH in CHCl3 at room temperature affords a mixture of N(2)-bound 1H- and 3H-4-ethoxycarbonyl triazolato complexes {[Ru]N3HC2HCO2Et}[CF3COO] (1H-7) and (3H-7) in a ratio of 5 : 2. The structures of 4e, 5 and 1H-7 were confirmed by single-crystal X-ray diffraction analysis.

A novel trinuclear complex [Ni3(μ3-dbay)4Cl2]I3 (1) with a mixed-valence state was prepared by reacting the tridentate ligand 1,13,14-triaza-dibenz[a,j]anthracene (dibenzanthyridine = dbay) with anhydrous NiCl2 and sodium tetraphenylborate. The title compound provides the first example of a trinuclear nickel-anthyridine-based string complex in which the metal framework of complex 1 consists of NiII-NiI-NiII. X-ray crystallography, magnetic susceptibility and detailed EPR measurements were performed to characterize the structure and magnetic properties of this unique complex.

By using tripyridyldiamine ligand, N , N’ -di(pyrazin-2-yl)pyridine-2,6-diamine (H 2 dpzpda), linear pentanuclear nickel(II) [Ni 5 (µ 5 -dpzpda) 4 Cl 2 ] (1) and tetranuclear copper(II) [Cu 4 (Hdpzpda) 2 (CH 3 COO) 6 ] (2) complexes were first synthesized and structurally characterized. This pentanickel linear metal chain is helically wrapped by four syn-syn-syn-syn type dpzpda 2- ligands. There are two types of Ni Ni distances existing in the complex. The terminal Ni Ni distances bonded to the axial ligand are longer (2.3877(8) A) affected by the axial ligands. The inner Ni Ni distances are very short and remain constant (2.3071(6) A). Two terminal Ni(II) ions bonded to the axial ligands are in a square-pyramidal (NiN 4 Cl) environment and exhibit long Ni N bonds (2.097(4) A), which are consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions display short Ni N (1.8915(8)–1.903(4) A) bond distances, which are consistent with a square planar (NiN 4 ), the diamagnetic arrangement of a low-spin Ni(II) configuration. Temperature-dependent magnetic research revealed an antiferromagnetic interaction between the two terminal atoms through a superexchange pathway along metal cores with a parameter of about −51.0 cm –1 . Observation of the first oxidation peak in the cyclic voltammograms of 1 at +1.206 V revealed that this complex is the most resistant to oxidation among all known pentanuclear nickel strings with unmodulated and modulated oligo-α-pyridylamido ligands. The structure of 2 consists of four copper atoms linearly placed with a copper(II) acetate dimer in the centre. In complex 2 ligand H 2 dpzpda coordinates to the Cu(II) atoms as a tetradentate ligand in an all anti conformation. Copper complex 2 is built to a 1-D supramolecular chain structure through intermolecular hydrogen bond and strong π-π interaction (3.19 A) between the pyridine and pyrazine rings. From the magnetic susceptibility data, 2 shows strong antiferromagnetic coupling, which was satisfactorily fitted using Hamiltonian H = J 1 ( S 1 S 2 + S 3 S 4 ) + J 2 S 2 S 3 . The best fitting result were obtained with the parameters J 1 = 10.64 cm −1 , J 2 = −175.36 cm −1 , g = 2.11.

A new class of bis-tridentate Ir(III) complexes (Dap-1-4) was synthesized using carbene pincer pro-chelates PC1·H3(PF6)2 or PC2·H3(PF6)2 with either imidazolylidene or imidazo[4,5-b]pyridin-2-ylidene appendages, together with a second cyclometalating 2,6-diaryoxypyridine chelate, L1H2 and L2H2, differed by a NMe2 donor at the central pyridinyl fragment. The respective emission tuning between the ultraviolet and blue region was rationalized using time-dependent density functional theory (TD-DFT) approaches. Next, a highly efficient blue emitter (Dap-5) was synthesized by concomitant addition of two methyl groups and a single CF3 substituent at the central phenyl and peripheral imidazo[4,5-b]pyridin-2-ylidene entities of the carbene pincer chelate, respectively. The organic light-emitting diode (OLED) device with 15 wt % Dap-5 in DPEPO shows electroluminescence at 468 nm and with CIE (0.14, 0.15) and a max external quantum efficiency (max EQE) of 16.8% with low efficiency roll-off (EQE of 14.4% at 1000 cd m-2); the latter is attributed to the relatively shortened triplet excited-state radiative lifetime. These results highlight the adequateness of bis-tridentate Ir(III) phosphors in fabrication of practical blue-emitting OLEDs.

The reaction of Re(CO)5Cl with 4-mercaptopyridine (4-PySH) led to the formation of [Re(CO)3(4-HPyS)3]Cl (1), showing three hydrogen-bonding donors of 4-PySH ligands as well as a characteristic liga...

In a refluxing chloroform solution, the &eta, 1-pyrimidinyl {pyrimidinyl = C4H3N2} palladium complex [Pd(PPh3)2(&eta, 1-C4H3N2)(Br)], 1 exhibited intermolecular displacement of two triphenylphosphine ligands to form the doubly bridged &eta, 2-pyrimidinyl Dipalladium complex [Pd(PPh3)(Br)]2(&mu, &eta, 2-C4H3N2)2, 3. The treatment of 1 with Hdppa {Hdppa = N,N-bisdiphenyl phosphinoamine} in refluxing dichloromethane yielded the doubly bridged Hdppa dipalladium complex [Pd(Br)]2(&mu, 2-Hdppa)2, 4. Complex 1 reacted with the bidentate ligand, NH4S2CNC4H8 and, NaS2COEt, and the tridentate ligand, KTp {Tp = tris(pyrazoyl-1-yl)borate}, to form the &eta, 2-dithio &eta, 1-pyrimidinyl complex [Pd(PPh3)(&eta, 1-C4H3N2)(&eta, 2-SS)], (5: SS = S2CNC4H8, 6: SS = S2COEt) and &eta, 2-Tp &eta, 2-Tp)], 7, respectively. Treatment of 1 with AgBF4 in acetonitrile at room temperature resulted in the formation of the doubly bridged &eta, 2-pyrimidinyl dipalladium complex [{Pd(PPh3)(CH3CN)}2(&mu, 2-C4H3N2)2][BF4]2, 8. All of the complexes were identified using spectroscopic methods, and complexes 3, 4, and 8 were determined using single-crystal X-ray diffraction analyses.

Three homoleptic Pt(II) metal complexes [Pt(imPz)2] (1), [Pt(imiz)2] (2), and [Pt(imMz)2] (3) were synthesized from the treatment of Pt(DMSO)2Cl2 and functional imidazolyl pyrazole in refluxing tetrahydrofuran (THF). Alternatively, the heteroleptic Pt(II) complexes [Pt(imPz)(fppz)] (4), [Pt(imiz)(fppz)] (5), and [Pt(imMz)(fppz)] (6) were obtained from the treatment of a common intermediate [Pt(fppzH)Cl2] with a corresponding imidazolyl chelate. Pt(II) complexes 1, 2, and 5 were studied by single-crystal X-ray diffraction to reveal the corresponding packing arrangement in their crystal lattices, among which both homoleptic complexes 1 and 2 formed monomeric species, while heteroleptic 5 aligned as a dimer with a nonbonding Pt···Pt contact of 3.574 A. Subsequent photophysical examinations showed that the homoleptic 1-3 and heteroleptic 4-6 exhibited the structured sky-blue ππ* emission and structureless light-green-emitting metal-metal-to-ligand charge transfer (MMLCT) emission in the solid state, respectively. A shortened Pt···Pt interaction of approximately 0.34-0.35 nm was confirmed in thin films of all heteroleptic Pt(II) complexes 4-6 by grazing-incidence X-ray diffraction (GIXD) analyses. Finally, Pt(II) complex 6 was employed as a dopant in the fabrication of organic light-emitting diode (OLED) devices with varied doping ratios, among which OLEDs with only 1 wt % 6 in the SimCP host exhibited a maximum external quantum efficiency (EQE) of 5.8% and CIEx,y values of 0.20, 0.31. In contrast, OLEDs using a nondoped architecture (i.e., 100% of 6 in the emitting layer (EML)) achieved a maximum EQE of 26.8%, current efficiency (CE) of 91.7 cd A-1, and power efficiency (PE) of 80.1 lm·W-1 and CIEx,y values of 0.41, 0.55, manifesting their versatility in various degrees of stacking assemblies and hence facile color-tuning capability on OLEDs.

Multiple-stimuli-responsive photoluminescence films based on a ZnII -organic framework, {[Zn2 (Htpim)(3,4-pydc)2 ]⋅4 DMF⋅4 H2 O}n (1, Htpim=2,4,5-tri(4-pyridyl)imidazole, 3,4-H2 pydc=3,4-pyridinedicarboxylic acid), were fabricated. This compound consisted of a 2D corrugated layer, {Zn(3,4-pydc)}n , which was further pillared using a Y-shaped pillar N-donor ligand (Htpim) to form a 3D-pillared-layer framework with 1D open channels. The rectangular channels in the as-synthesized compound are fully occupied by guest DMF and H2 O molecules. The framework exhibits instant and reversible thermochromic properties corresponding to the removal of different H2 O and DMF guest molecules as temperature increases. The pale-yellow crystal undergoes significant redshifting to a greenish emission centered at 530 nm. Compound 1 also showed remarkable solvatochromic effects in the presence of various organic solvents without affecting its structural integrity. In addition, polycrystalline MOF films were grown on an α-Al2 O3 support for switchable and fast-response thermochromic and solvatochromic sensors.

Three new families of borondifluoride complexes 1a–c derived from salicylideneamines 2a and β-enaminoketonates 2b–c were reported, and their mesomorphic and optical properties were also investigated. One single crystal and molecular structure of nonmesogenic BF2 complex 1c (n = 10) was resolved and the geometry of the central boron atom was tetrahedron. A larger dihedral angle of 81.3° between the two phenyl rings observed in crystal lattice was attributed to the lack of liquid crystallinity. Boron complexes 1a formed monotropic SmA phases, while boron complexes 1b exhibited enantiotropic SmC mesophases. The optical property of the boron complexes was dependent on their molecular structures, and they emitted a blue–to–green emission at λmax = 476–541 nm in the solution and 488–550 nm in the solid state. This is the first group of mesogenic BF2 complexes with the Schiff bases derived from respective salicylideneamines and β-enaminoketones.

The [3+2] cycloaddition reaction of ethyl propiolate with ruthenium azido complex [Ru]−N3 (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) has been investigated. The metal-bound heterocyclic complex produced is N(2)-bound triazolate [Ru]N3CHCO2Et (2). A regiospecific alkylation happens by treatment of 2 with organic halides and gives a series of cationic N(1)-bound N(3)-alkylated-4-ethoxycarbonyl triazolato complexes {[Ru]N3(R)C2HCO2Et}[X] (3a, R = CH3, X = I; 3b, R = CH2Ph, X = Br; 3c, R = CH2C6F5, X = Br; 3d, R = CH2CN, X = I; 3e, CH2CO2CH3, X = Br) and the following cleavage of the Ru-N bond of 3a and 3b gives ruthenium halides and N(1)-alkylated five-membered-ring organic triazoles N3(R)C2HCO2Et (4a, R = CH3; 4b, R = CH2Ph). The structures of 2 and 3c have been determined by single-crystal X-ray diffraction analysis.

By using tetranaphthyridyl-triamine ligand, N2-(2-(1,8-naphthyridin-7-ylamino)-1,8-naphthyridin-7-yl)-N7-(1,8-naphthyridin-2-yl)-1,8-naphthyridine-2,7-diamine (H3tentra), double-stranded dinuclear helical compounds [M2(H3tentra)2(ClO4)4] [M = NiII (1), CoII (2), FeII (3), ZnII (4)] were synthesized and structurally characterized. The single X-ray crystal structure of iron(II) complex showed that both of H3tentra ligands wrap around the metal–metal axis giving rise to a double-stranded dinuclear helical compound with Fe–Fe separation of ca. 5.326 A. Each ligand uses two nitrogen atoms from two different napthyridine rings, to coordinate one metal centre (Fe or Fe(A)) and therefore, the geometry about the metal ions was described as distorted tetrahedral, with both ligands acting as bisbidentate N4 donors. This distortion is shown by the angles between nitrogen and iron atoms, which range from 80.45(15) to 143.32(14)°. Distorted tetrahedral environment was also proposed for the other complexes on the basis of the magnetic measurements and X-ray results. Strong π–π interactions were observed for all synthesized double stranded helicates of H3tentra ligand. The measured χMT values at 300 K for complexes 2 and 3 found larger than the expected values for two high-spin Co(II) with S = 3/2 and for Fe(II) ions with S = 2 and g = 2, which attributed to the unquenched orbital coupling.

An evanescent wave infrared chemical sensor was developed for the selective detection of odorous amino compounds in the atmosphere. To achieve this goal, cavity-containing rhenium metallacycles with multi-recognition sites were prepared and used as host molecules to modify the surface of an evanescent wave infrared (EWIR) sensing element. The unique cavity structure with hydrophobic properties of the Re metallacycle permits the selective trapping of suitably sized compounds with proper functionalities. To explore the scope of the process, two different Re metallacycles were synthesized and used to trap a series of volatile organic compounds (VOCs) with different functionalities. Based on the results, Re metallacycles are selective to detect amino compounds as evidenced by the peak shifts for C O absorption after the amino compounds had been adsorbed. The hydrophobic pocket and hydroxyl groups in the Re metallacycles were also verified to provide extra forces to stabilize the attraction of amino compounds. The efficiency of the Re metallacycles in detecting amino compounds follows the order of amine with phenyl ring > aliphatic primary amine ∼ cyclo-amine > aliphatic secondary amine > aliphatic tertiary amine. This sensor was applied to detect benzyl amine and a linear range up to 1 mg/L could be obtained with a detection limit close to 4 μg/L.

As a new synthetic approach, a versatile building block of [(Re(CO)4)3(N3S3)] (1a) can be used to react with linear dipyridyl ligands (i.e., pyrazine (pz), 4,4'-bipyridine (bpy), 1,2-di(4-pyridyl)ethylene (dpe), bis(4-pyridyl)acetylene (bpa), and 1,4-bis(pyridyl-4-ylethynyl)benzene (bpb)) and a tripyridyl one (1,3,5-tris(4-pyridylethynyl)benzene (tpb)) to afford a series of molecular cages, [(Re(CO)3)6(L)3(N3S3)2] (L = pz 2; bpy 3; bpe 4; bpa 5; bpb 6) and [(Re(CO)3)9(tpb)3(N3S3)3] (7) by solvothermal methods. Interestingly, various structural dimensions and motifs can be systematically tuned and obtained depending on different dipyridyl and tripyridyl ligands used in the reaction condition. In this regard, molecular cages of hexanuclear complexes of 2-6 containing dipyridyl ligands feature interesting trigonal-prism structures with different dimensionalities. Furthermore, the nonanuclear complex of 7 shows a novel trianglular-star structure, and three benzene rings of tpb ligands form a triple-decker arrangement with significant pi...pi interactions of 3.490(1) and 3.528(1) A. In addition, molecular cages of 1-3 and 5-7 exhibit luminescence in the solid state, and their luminescent properties are also studied.

In an attempt to prepare the heavier analogue of NHC-stabilized borenium cation, we have prepared a silylene-coordinated borenium equivalent (1a), which can be viewed as a contact ion pair of borenium and triflate. The triflate anion coordinates to the oxophilic silicon center, leaving the boron center existing in a trigonal-planar geometry in the solid state and in solution. Nucleophilic substitution reactions of 1a all result in the release of free silylene ligand, demonstrating the borenium-ion-like reactivity of 1a. Chemical reduction of 1a leads to a neutral radical possessing a partial Si–B double bond.

Tetradentate chelates bearing tripodal arranged terpyridine and a functional pyrazole unit (i.e., L1-H and L2-H) were employed in preparation of Ir(III) complexes [Ir(L1)Cl2] (1) and [Ir(L2)Cl2] (2); subsequent chloride-to-bipyrazolate substitution gave [Ir(L1)(bipz)] (3) and [Ir(L2)(bipz)] (4). Single-crystal X-ray structural studies on 1 and 3 showed the possession of a tetradentate chelate, whereas the remaining cis-sites are occupied by either dual chlorides or the bipz chelate, respectively. Sky blue organic light-emitting diode with peak efficiencies (10.1%, 19.8 cd·A–1, and 20.4 lm·W–1) was successfully fabricated using 3 (or 4) as dopant emitter, highlighting the potential application of this class of Ir(III) phosphor.

Small-molecule compounds targeting trinucleotide repeats in DNA have considerable potential as therapeutic or diagnostic agents against many neurological diseases. NiII (Chro)2 (Chro=chromomycin A3) binds specifically to the minor groove of (CCG)n repeats in duplex DNA, with unique fluorescence features that may serve as a probe for disease detection. Crystallographic studies revealed that the specificity originates from the large-scale spatial rearrangement of the DNA structure, including extrusion of consecutive bases and backbone distortions, with a sharp bending of the duplex accompanied by conformational changes in the NiII chelate itself. The DNA deformation of CCG repeats upon binding forms a GGCC tetranucleotide tract, which is recognized by NiII (Chro)2 . The extruded cytosine and last guanine nucleotides form water-mediated hydrogen bonds, which aid in ligand recognition. The recognition can be accounted for by the classic induced-fit paradigm.

Through a pyrazine and naphthyridine-containing diamino ligand, N2,N7-di(pyrazin-2-yl)-1,8-naphthyridine-2,7-diamine (H2dpznda), defective extended metal atom chain complexes with one chromium(II) metal absent in centre, [Cr5(μ5-dpznda)4Cl2] (1) and [Cr5(μ5-dpznda)4(NCS)2] (2) were obtained. An electrochemistry research showed that the pentachromium(II) complexes were quite resistant to reduction although accessible to oxidation, with two reversible redox couples at E1/2 = +0.59 and +0.30 V.

Two novel linear hexanuclear nickel complexes [Ni 6 ( μ 6 -dpznda) 4 Cl 2 ](PF 6 ) 2 (1) and [Ni 6 ( μ 6 -dpznda) 4 (NCS) 2 ](PF 6 ) 2 (2) (H 2 dpznda = N 2 , N 7 -di(pyrazin-2-yl)-1,8-naphthyridine-2,7-diamine) were synthesized and structurally characterized. Both the two complexes consist of a linear metal chain and four supporting ligands which are helically wrapped around the metal core. The single crystal X-ray structural analysis showed that the complex 1 belonged to rhombohedral system, space group R -3 with a = b = 34.2051(8), c = 20.7751(5) A, V = 21050.2(9) A 3 and Z = 9. Direct-current magnetic susceptibility measurements showed weak antiferromagnetic interactions with coupling parameters of g = 2.04 and J = −8.27 cm −1 for 1 and g = 2.02 and J = −12.62 cm −1 for 2 , respectively ( Ĥ = –JŜ 1 Ŝ 2 , S 1 = S 2 = 1). The decrease of magnetic moments at low temperature was partly attributed to ZFS. The electrochemical study on complex 1 shows rich features and facility to reduction in its cyclic voltammogram by displaying four reversible redox couples at E 1/2 = +0.01, −0.29, −0.64 and −0.73 V ( vs. Ag/AgCl).

A new pyrimidine-modulated ligand, N2-(pyridin-2-yl)-N6-(pyrimidin-2-yl)pyridine-2,6-diamine (H2pppmda) (1), its mononuclear copper(II) complex [Cu(H2pppmda)(CH3OH)](ClO4)2 (2) and pentanickel metal string complex [Ni5(μ5-pppmda)4Cl2] (3) have been synthesized and structurally characterized. X-ray analysis showed that the free ligand exhibits the syn–anti–syn–syn conformation and intermolecular hydrogen bonds link the ligand molecules to a 1-D network along the c axis. H2pppmda coordinates to the metal atom with all-anti mode in the copper mononuclear complex 2 and the coordination geometry of the Cu(II) ion is an elongated octahedron. The [Ni5(μ5-pppmda)4Cl2] complex involves a Ni5 linear chain unit where all the Ni–Ni–Ni angles are nearly 179° and which is terminated by the two axial ligands. The pentanuclear linear metal chain is helically wrapped by four syn–syn–syn–syn type pppmda2− ligands. There are two types of Ni–Ni distance in this complex. Terminal Ni–Ni distances bonded with the axial ligand are longer (2.3669(8) A); the inner Ni–Ni distances are short at 2.2987(6) A. The terminal Ni(II) ions bonded with the axial ligands are square-pyramidal (NiN4Cl) with long Ni–Nav bonds (2.096 A), consistent with a high-spin Ni(II) configuration. The inner three Ni(II) ions have short Ni–Nav bond distances (1.902(4)–1.888(4) A), consistent with a square planar (NiN4), diamagnetic arrangement of a low-spin Ni(II) configuration. This compound exhibits magnetic behavior similar to [Ni5(μ5-tpda)4Cl2], indicating an antiferromagnetic interaction of the two terminal high-spin Ni(II) ions. Electrochemical studies showed that the pentanickel(II) complex can undergo one reversible oxidation at +0.76 V. The introduction of an electron-withdrawing pyrimidine ring to the spacer ligand retarded the oxidation of the pentanickel metal string and stabilized the complex.

One new series of boron difluoride complexes 1 derived from heterocyclic benzoxazoles 2 was reported, and their mesomorphic and optical properties were also investigated. One single crystal of the mesogenic BF2 complex 1a (m = 12, n = 8) was obtained, and its single crystal and molecular structure were resolved. The geometry coordination at the central boron atom is tetrahedral. It crystallizes in a triclinic space group P with Z = 4. The overall molecular shape was described as slightly bent Z-shapes, and the molecular length was ca. 34.06 A. Weak intramolecular and intermolecular H-bonds observed in the crystal lattice were attributed to the formation of mesophases. The results indicated that benzoxazoles 2a (n = 6, 8, 12) formed monotropic SmA phases, while boron difluoride complexes 1a (n = 6, 8, 12, 16) exhibited monotropic SmC mesophases. In contrast, all compounds of 2b and 1b (m = 1, n = 12 for all) were not mesogenic. Boron complexes 1 emitted a pronounced violet emission at λmax = 399 nm in solution at room temperature.

Striding to extend the length of metal-atom strings, oligo-α-pyridylamino ligands are modulated with naphthyridyl moieties leading to the undeca-nickel mixed-valence complexes [Ni11(bnatpya)4Cl2]4+ (1) and [Ni11(bnatpya)4Cl2]2+ (2). The first single-molecule conductance measurements of a linear undeca-nickel chain were performed.

The azido-bridged molybdenum complex [N(CH3)4][(μ1,1-N3)3{Mo(η3-C3H5)(CO)2}2], 1, was synthesized and its reactions with unsaturated nitriles and alkynes were investigated. The isolated [3 + 2] cycloaddition products were the N(2), N(3) bound tetrazolate complexes [N(CH3)4][(μ1,1-N3)2(μ-N4C{R}-κ2N2:N3){Mo(η3-C3H5)(CO)2}2] (R = C(CN)C(CN)2 (2), C6H4NO2, (3)) and [N(CH3)4][(μ-N4C{R}-κ2N2:N3)2(μ1,1-N3){Mo(η3-C3H5)(CO)2}2] (R = C(CN)C(CN)2 (4), C6H4NO2 (5)), and the N(1), N(2) bound triazolate complexes [N(CH3)4][(μ-N3C2{R}2-κ2N1:N2)(μ1,1-N3)2{Mo(η3-C3H5)(CO)2}2] (R = CO2CH3 (6) and R = CO2CH2CH3 (7). The reactivity of these cycloaddition reactions could be determined by the electronic properties of both metal azide and dipolarophile. In the reaction of 1 with nitriles, at most two bridging azido groups can participate in the cycloaddition reactions and elevated temperature is required for the preparations of 3 and 5. In the case of alkynes, only one azido group is active for the reaction. These complexes are fluxional in solution, and isomers were found in 3 and 5. The molecular structures of the above complexes were determined by single-crystal X-ray diffraction analysis, which reveals a distorted octahedral geometry around each molybdenum atom, and the two metal atoms are connected through three bridging ligands. The formation of these heterocycles demonstrated the [3 + 2] cycloaddition reaction could also be applied to the less electron-rich azido-bridged molybdenum complex.

Treatment of [Ru]–CCPh (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with trimethylsilyl azide afforded the cationic nitrile complex {[Ru]NCCH2Ph}[N3] (2) and the further cycloaddition of 2 with trimethylsilyl azide at 60 °C afforded the N(2)-bound tetrazolato complex [Ru]N4CCH2Ph (3). The regiospecific alkylation of 3 gave a series of cationic N(2)-bound N(4)-alkylated-5-benzyl tetrazolato complexes {[Ru]N4(CH2R)CCH2Ph}[Br] (4a, R = C6F5; 4b, R = Ph; 4c, R = 4-CN-C6H4; 4d, R = 2,6-F2-C6H3; 4e, R = 6-CH2Br-C5NH3) and the subsequent cleavage of the Ru–N bond of 4a–4e gave N(1)-alkylated-5-benzyl tetrazoles N4(CH2R)CCH2Ph (5a–5e) in good to excellent yields and [Ru]–Br, which, on reacting with phenylacetylene, resulted in the formation of 1 thus forming a reaction cycle. The structures of 2, 3, 4a, 4c and 5a were confirmed by single-crystal X-ray diffraction analysis.

Two ligands, 2,4-di-2-pyridyl-2,4-pentanediol (rD and mD), were employed to synthesize two Mn2 complexes, [Mn2(rD)2Br2] (1) and [Mn2(mD)2(H2O)2]Br2 (2). Compound 1 crystallized in a tetragonal space group, P41212, with a novel hamburger shaped structure. A detailed study indicated that compound 1 did not contain a metal&ndash, metal bond, but antiferromagnetic coupling was observed between the Mn(III) ions. Compound 2 crystallized in a monoclinic space group, C2/c, with one Mn(II) and the other with Mn(IV). The two manganese ions were bridged by two alkoxide ligands, resulting in ferromagnetic coupling. Magnetic property studies confirm the above assignments.

Briareum stechei is proven to be a rich source of 3,8-cyclized cembranoids (briarane) with a bicyclo[8.4.0] carbon core. In the present study, four previously unreported briaranes, briarenols W–Z (1–4), along with solenolide A (5), briarenolide M (6), briaexcavatolide F (7), and brianolide (8), were isolated and characterized through spectroscopic analysis, and the absolute configuration of 8 was corroborated by a single-crystal x-ray diffraction analysis. Briaranes 2 and 5 were found to induce significant inflammatory activity in lipopolysaccharide (LPS)-induced RAW 264.7 mouse macrophage cells by enhancing the expression of the inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins.

Chemical examination of Briareum excavatum, collected in the waters of Taiwan, led to the isolation of four briarane diterpenoids, including three known compounds, briarenol G (1), briaviolides Y (2), and Z (3), as well as a new metabolite, briarenol L (4). The absolute configuration of 1 was determined by a single-crystal X-ray diffraction analysis for the first time in this study and the structure of 4 was established on the basis of spectroscopic analysis. Briaranes 2 and 3 exerted inhibition effects on COX-2 and iNOS, respectively, release from RAW 264.7 macrophages.

A series of bis-bidentate nickel(II) complexes [Ni(R-bimy-CH2CONH)2] (bimyH = benzimidazole; R = Me (3), Et (4), Ph (5)) bearing amido-functionalized N-heterocyclic carbene ligands, and pincer-type nickel(II) complexes [Ni(Py-bimy-CH2CONH)X] (X = Cl (6), Br (7)) bearing an amido- and pyridyl-functionalized N-heterocyclic carbene ligand were prepared. These complexes were characterized by NMR (1D and 2D) and single-crystal X-ray diffraction. Complexes 3-5 possess cis configuration, and the carbene ligands bound to the nickel atom through C2 carbon and NH nitrogen in a bis-bidentate coordination mode. In complexes 6 and 7, the pyridyl substituent was also N-bound to the nickel metal center resulting in a pincer-type coordination mode. As observed from the proton NMR spectra, the six-membered chelate rings in complexes 3-5 rendered the protons of the methylene moieties diastereotopic, and the cis configuration made the free rotation of the ethyl substituent in 4 and the phenyl substituent in 5 hampered by the adjacent substituent. The catalytic activity of these nickel complexes in Kumada cross-coupling of phenylmagnesium bromide with aryl chlorides was also investigated. The results indicated that pincer-type complexes 6 and 7 displayed excellent to moderate catalytic activity depending on the aryl chloride used.

The syntheses, crystal structures, and magnetic properties of three trinuclear, symmetric, heterometal string complexes stabilized by four dipyridylamide (dpa) ligands were explored. MnNiMn(dpa)4Cl2 (1), MnPdMn(dpa)4Cl2 (2), and MnPtMn(dpa)4Cl2 (3) were found to exhibit an approximate D4 symmetry and a linear metal framework helically wrapped by four syn–syn-type ligands. The center metal ions bond with the amide part of dpa– in a square-planar environment, and the outer Mn ions bond with Cl– and the pyridyl part of dpa– in a square-pyramidal environment. The magnetic susceptibilities of these three compounds showed antiferromagnetic interactions (2J = –13.7 cm–1 for 1, –29.7 cm–1 for 2, and –66.2 cm–1 for 3 in the Heisenberg exchange framework) between the MnII magnetic centers. The value of 2J increased with increasing atomic number of the central metal ion. The antiferromagnetic properties were further confirmed by electron paramagnetic resonance spectroscopy studies in variable-temperature measurements.

Vanadium chemistry is of interest due its biological relevance and medical applications. In particular, the interactions of high-valent vanadium ions with sulfur-containing biologically important molecules, such as cysteine and glutathione, might be related to the redox conversion of vanadium in ascidians, the function of amavadin (a vanadium-containing anion) and the antidiabetic behaviour of vanadium compounds. A mechanistic understanding of these aspects is important. In an effort to investigate high-valent vanadium–sulfur chemistry, we have synthesized and characterized the non-oxo divanadium(IV) complex salt tetraphenylphosphonium tri-μ-methanolato-κ6O:O-bis({tris[2-sulfanidyl-3-(trimethylsilyl)phenyl]phosphane-κ4P,S,S′,S′′}vanadium(IV)) methanol disolvate, (C24H20P)[VIV2(μ-OCH3)3(C27H36PS3)2]·2CH3OH. Two VIVmetal centres are bridged by three methanolate ligands, giving aC2-symmetric V2(μ-OMe)3core structure. Each VIVcentre adopts a monocapped trigonal antiprismatic geometry, with the P atom situated in the capping position and the three S atoms and three O atoms forming two triangular faces of the trigonal antiprism. The magnetic data indicate a paramagnetic nature of the salt, with anS = 1 spin state.

Both the reduced and the protonated states of diiron dithiolate complexes, which are key intermediate species for the electrocatalytic production of hydrogen, have been spectroscopically and theoretically investigated in this study. Five important states in the process of H2 evolution have been characterized. In the presence of a superacid, protonation occurs onto the Fe–Fe vector of [(μ-xdt)Fe2(CO)6] (xdt: pdt, 1,3-propanedithiolate; edt, 1,2-ethanedithiolate; bdt, 1,2-benzenedithiolate) to yield the cationic μ-H species (the C state). A single reduction at 193 K leads to the neutral species (the CE state), with similar structures for the pdt and edt bridgeheads. The CE species of the bdt analogue is unstable under the same conditions. An open structure resulting from the rupture of one Fe–S bond is suggested by DFT calculations. Subsequently, a second reduction induces a dramatic structural rearrangement in which the CEE state possesses an open structure exhibiting a μ-H and a μ-CO group. Protonation on...

A new class of neutral bis-tridentate Ir(III) metal complexes that show nearly unitary red, green, and blue emissions in solution is prepared and employed for the fabrication of both monochrome and white-emitting organic light-emitting diodes, among which a green device gives external quantum efficiency exceeding 31%.

Boron mono- and di-cations featuring a nucleophilic N-heterocyclic olefin and the pentamethylcyclopentadienyl substituent have been prepared and structurally characterized. Experimental and theoretical investigations show that [η5-Cp*B-NHO]2+is considerably more Lewis acidic than [η5-Cp*B-IMes]2+due to the steric congestion imposed by the bent geometry of NHO around the central boron atom.

Two new series of mesogenic palladium complexes 1a–b derived from salicylaldimines containing phenyl or naphenyl moiety were prepared, characterized and their mesomorphic properties investigated. Two single crystallographic structures of mesogenic 1a (n=4) and nonmesogenic 1b (n=3) were determined by X-ray analysis; both crystals crystallize in a triclinic space group P1. The geometry at both palladium atoms was nearly square planar. All Schiff bases 2a–b and palladium complexes 1a–b exhibited mesomorphic properties. However, the formation of mesophases was sensitive to terminal naphthalyl and phenyl group. Compounds 2a formed N or/and SmC phases and compounds 2b exhibited N or/and SmC phases. In contrast, palladium complexes 1a formed N or N/SmC phases and complexes 1b exhibited N, N or/and SmC phases. Compounds 1b have a higher clearing temperature than those of 1a by a ΔTcl=35.4−14.8 °C. An improved mesomorphic behavior observed in compounds 1b was attributed to the H-bonds and π–π interaction.

Functional 2-pyrazolyl-6-phenylpyridine chelates-namely, (pzpyphBu)H2 and (pzpyphCF3)H2 and phosphines-are successfully employed in the preparation of emissive Ir(III) metal complexes, for which the reaction with phosphine such as PPh3, PPh2Me, and PPh2(CH2Ph) afford corresponding Ir(III) complexes [Ir(pzpyphBu)(PPh3)2H] (1a), [Ir(pzpyphCF3)(PPh2R)2H] (2a-2c), R = Ph, Me, CH2Ph, which also show an equatorial coordinated hydride. In contrast, treatment with 1,2-bis(diphenylphosphino)benzene (dppb) and 1,2-bis(diphenylphosphino)ethane (dppe) yields the isomeric products [Ir(pzpyphBu)(dppb)H] (3a) and [Ir(pzpyphBu)(dppe)H] (3b), for which the distinctive, axial hydride undergoes rapid chlorination, forming chlorinated complexes [Ir(pzpyphBu)(dppb)Cl] (4a) and [Ir(pzpyphBu)(dppe)Cl] (4b), respectively. On the other hand, upon extensive heating of 2c, one of its coordinated PPh2(CH2Ph) exhibits benzyl cyclometalation and hydride elimination to afford [Ir(pzpyphCF3)(PPh2R)(PPh2R')] (5c and 6c) R = CH2Ph and R' = CH2( o-C6H4) as the kinetic and thermodynamic products, respectively. Their structural, photophysical, and electrochemical properties are examined and further affirmed by the computational approaches.

A class of neutral tris-bidentate Ir(III) metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppb)(tht)Cl3] (1) with fppzH afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (2) and cis-(Cl,Cl)[Ir(dppb)(fppz)Cl2] (3). The reaction of 3 with the dianionic chelate precursor bipzH2 or mepzH2, in DMF gave the complex [Ir(dppb)(fppz)(bipz)] (4) or [Ir(dppb)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppb)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: DGME. All complexes 2 - 6 are luminescent in powder forms and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (Q.Y.s) up to 90% whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with Q.Y.s up to 70%. Hybrid TD-DFT calculations showed considerable MLCT contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3ππ* transition character in the blue-emitting 4 - 6. The dppb does not participate to these radiative transitions in 4 - 6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an OLED with dopant 5 gave a deep blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir(III) complexes containing phosphine chelates.

The ligand, 2, 7-bis(α-5-phenylpyrazinamino)-1, 8-naphthyridine (H2bphpzany), was synthesized by the reaction of 2, 7-dichloro-1, 8-naphthyridine with 2-amino-5-phenylpyrazine in the presence of potassium tert-butoxide under palladium(0)-catalyzed conditions. Linear defective penta-cobalt metal-string complex [Co5(bphpzany)4(NCS)2] (1) and hexa-cobalt Co611+ complex [Co6(bphpzany)4(NCS)2](PF6) (2) each containing four bphpzany2– ligands were synthesized, and their structure was determined using single-crystal X-ray diffraction. The structure of complex 1 consists of two lantern-type dinuclear Co2 fragments at the terminal positions and one rare octacoordinated cobalt at the center forming a linear [Co2···Co···Co2] chain. The magnetic susceptibility measurement of 1 shows a quartet ground state with a significant spin-orbital contribution of the central CoII ion. Complex 2 consists of a linear Co611+ configuration wrapped by four bphpzany2– ligands and its magnetic susceptibility measurement reveals a two-stages magnetic behavior with spin-states of S = 1/2 at 2 K, and S = 3/2 at 300 K. The cyclic voltammograms display three redox waves at E1/2 = +0.97, E1/2 = +0.71 and E1/2 = –1.02 V for 1, and four waves at E1/2 = +1.32, E1/2 = +0.99, E1/2 = +0.64, and E1/2 = –0.14 V for 2, respectively. The values of single-molecular resistance for 1 and 2 are 15.5 (±4.84) and 16.1 (±10.4) MΩ, respectively.

Two defective nickel-extended metal-atom chain (EMAC) complexes were synthesized from a pyrazine- and naphthyridine-containing ligand and structurally characterized. The chains consist of dinickel and trinickel units with one absent metal center, in spite of which the complexes are very stable. The magnetic interaction between the two terminal, high-spin nickel atoms is very weak with a spin exchange of J = –0.62(3) cm–1. An electrochemical study on one of the defective nickel EMAC complexes showed high resistance to both oxidation and reduction, with one reduction at E1/2 = –0.76 V and no observable oxidation events in the range from –0.9 V to +1.20 V.