pyridyl-N Atoms Research Articles

Diamondoid framework solid with Sn(OCH₃)₂-tetrapyridylporphyrin linkers, CuI nodes and [CuICl₂]⁻ counter-ions.

We report on the synthesis of a new metal-organic framework (MOF) composed of Sn(OCH3)2-tetrakis(pyridin-4-yl)porphyrin linkers, Cu(+) connecting nodes and [CuCl2](-) counter-ions, namely poly[[bis(methanolato-κO)[μ5-5,10,15,20-tetrakis(pyridin-4-yl)porphyrin-κ(8)1κN(5):1'κN(10):1''κN(15):1'''κN(20):2κ(4)N(21),N(22),N(23),N(24)]copper(I)tin(II)] dichloridocuprate(I)], [CuSn(C40H24N8)(CH3O)2][CuCl2]. Its crystal structure consists of a single-framework coordination polymer of the organic ligand and the Cu(I) ions. The latter are characterized by a tetrahedral coordination geometry [with CN (coordination number) = 4], linking to the pyridyl N-atom sites of four different ligands and imparting to the positively charged polymeric assembly a diamondoid PtS-type topology. Correspondingly, every porphyrin unit is coordinated to four different Cu(I) connectors. The [CuCl2](-) anions occupy the intra-lattice voids, along with disordered molecules of the water crystallization solvent. The asymmetric unit of this structure consists of two halves of the porphyrin scaffold, located on centres of crystallographic inversion, and the Cu(+) and [CuCl2](-) ions. This report provides unique structural evidence for the formation of tetrapyridylporphyrin-based three-dimensional MOFs with a diamondoid architecture that have been observed earlier only on rare occasions.

2-Pyridyl-phosphine and -diphosphine complexes of nickel(0), their reactivity (including aqueous solution chemistry), and some related, incidental methylphosphonium iodides

The chemistry of Ni0-dicarbonyl(pyridylphosphine) complexes of the type Ni(CO)2L2, where L is either P-bonded PPh3−npyn (n=1–3, py=2-pyridyl; abbreviated PNx, x=1–3, species 1a–c), or L2 is (P–P)-chelated py2P(CH2)2Ppy2 or ▪, is further developed from earlier studies by our group [the P–P ligands are abbreviated, respectively, as d(py)pe and d(py)pcp]. The complexes are synthesized from C6H6 solutions of Ni(CO)2(PPh3)2, and the Ni(CO)2(PPh3)(PNx) intermediates (1a∗–c∗) are detected; Ni(CO)2[d(py)pcp] (2b) is shown by X-ray analysis to have a distorted tetrahedral structure; and the NiII species [Ni2(CO)4(μ-PN2)2]Cl4 is isolated from a light-induced reaction in CDCl3 solution. Complex 2b dissolves in water at ambient conditions via a net double protonation of pyridyl N-atoms, the {Ni(CO)2[2H-d(py)pcp]}2+ being isolated as the bis(triflate) salt; the dication decomposes in minutes with formation of [Ni(H2O)6]2+, CO, the phosphine dioxide, and deprotonated d(py)pcp. Some twenty-two Ni0 complexes, exemplified by Ni(P–P)2, Ni(PNx)2(P–P), Ni(PNx)4, and related PPh3- and Ph2P(CH2)2PPh2 (dppe)-containing species, are synthesized from Ni(1,5-COD)2 and their reactivity studied; for example, oxidative addition of MeI generates trans-Ni(Me)(I)(PN3)2 and trans-Ni(Me)(I)(P–P)2 but, with non-pyridyl containing reactants such as Ni(PPh3)4 and Ni(dppe)2, only (monomethyl)phosphonium iodides are formed. Such iodides, and the bis(methyl) analogues [(CH3)2(diphosphine)]I2, are then studied for clarification of some observed Ni chemistry. The NMR trends (a)–(d) are noted within the series of Ni0 complexes, and are rationalized: (a) the 2JPP values in 1a∗–c∗, and the separation between the two doublets, parallel the number of N-atoms present; (b) the 31P{1H} signals in the Ni(PNx)4 and Ni(PNx)2(P–P) complexes shift downfield in the order PN1<PN2<PN3 within linear dependences; (c) the 2JPP values for the Ni(PR3)2(P–P) complexes (R=Ph and PNx) decrease in the order R=Ph>PN1>PN2>PN3; (d) and the separation between the two 31P{1H} triplets of the Ni(PNx)2(P–P) complexes generally depends on the relative numbers of phenyl and pyridyl groups.

Binuclear Cu(I) complex of (N′1E,N′2E)-N′1,N′2-bis(phenyl(pyridin-2-yl)methylene)oxalohydrazide: Synthesis, crystal structure and catalytic activity for the synthesis of 1,2,3-triazoles

A new binuclear 5-coordinate distorted trigonal bipyramidal Cu(I) complex with (N′1E,N′2E)-N′1,N′2-bis(phenyl(pyridin-2-yl) methylene) oxalohydrazide (H2bpoh) has been synthesized, and characterized by spectroscopic and single crystal X-ray diffraction techniques. In the complex, H2bpoh acts as a dibasic hexadentate ligand bonding with two Cu(I) each through a carbonylate-O, azomethine-N, and pyridyl-N atoms. The complex possess a CuN2OP2 core with a considerable delocalization of charge on the five-membered chelate rings which forms an unusual intra-molecular π–π stacking and CH⋯π interactions. The synthesized complex exhibits excellent catalytic efficiency for a click reaction at room temperature.

High open circuit voltage in regioregular narrow band gap polymer solar cells.

The regioregular narrow band gap (E(g) ~1.5 eV) conjugated polymer PIPCP was designed and synthesized. PIPCP contains a backbone comprised of CPDT-PT-IDT-PT repeat units (CPDT = cyclopentadithiophene, PT = pyridyl[2,1,3]thiadiazole, IDT = indacenodithiophene) and strictly organized PT orientations, such that the pyridyl N-atoms point toward the CPDT fragment. Comparison of PIPCP with the regiorandom counterpart PIPC-RA illustrates that the higher level of molecular order translates to higher power conversion efficiencies (PCEs) when incorporated into bulk heterojunction (BHJ) organic solar cells. Examination of thin films via absorption spectroscopy and grazing incidence wide-angle X-ray diffraction (GIWAXS) experiments provides evidence of higher order within thin films obtained by spin coating. Most significantly, we find that PIPCP:PC61BM blends yield devices with an open circuit voltage (V(oc)) of 0.86 V, while maintaining a PCE of ~6%. Comparison against a wide range of analogous narrow band gap conjugated polymers reveals that this V(oc) value is particularly high for a BHJ system with band gaps in the 1.4-1.5 eV range thereby indicating a very low E(g) - eV(oc) loss.

Synthesis and structures of tris(2-pyridyl)aluminate sandwich compounds [{RAl(2-py')2}2M] (py' = 2-pyridyl, M = Ca, Mn, Fe).

Reactions of the lithium salts [{RAl(2-py')3Li·THF] [2-py' = 2-py (2-pyridyl), R = (n)Bu (1), R = (sec)Bu (2); py' = 5-Me-2-py (5-methyl-2-pyridyl), R = Me (3); 6-Me-2-py (6-methyl-2-pyridyl), R = Et (4b)] with the corresponding metal(ii) halides give the new heterobimetallic sandwich compounds [{RAl(2-py)3}2M] [R = (n)Bu, M = Ca (5), Mn (6), Fe (7); R = (sec)Bu, M = Ca (8), Mn (9)], [{MeAl(5-Me-2-py)3}2Ca] (10) and [{EtAl(6-Me-2-py)3}2Ca] (11) and the co-complex [{EtAl(6-Me-2-py)3}Mn(μ-Cl)Li{(6-Me-2-py)3AlEt}] (12). While neither the bridgehead group (R) nor remote ring Me-groups have any impact on metal coordination in 5-10, the introduction of Me groups into the pyridyl substituent at the 6-position (i.e., adjacent to the donor pyridyl-N atoms) has a marked effect on the ability of the ligands to form sandwich arrangements, as seen in the distorted structure of the sandwich compound 11 and in the formation of the co-complex 12, consisting of a two half-sandwich arrangement linked by a μ-Cl ion. The syntheses and solid-state structures of the new precursor 4b and the new compounds 5-12 are reported.

Syntheses, crystal structures and magnetic studies of new copper(II) complexes of (E)-N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide containing azide and SCN anions

Three new complexes of copper(II) with pseudohalide anions and (E)-N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide (HL), namely azide bridged dinuclear [Cu(L)(μ-N3)]2 (1), two-dimensional coordination polymer [Cu2(L)2(NCS)2]n (2a) and monomeric [Cu(L-H)(NCS)2] (2b), were synthesized. The complexes were characterized by elemental analyses and spectroscopic methods. The structures were unequivocally confirmed by X-ray diffraction, and further studied by means of EPR and magnetic susceptibility measurements. In all three complexes, the isonicotinohydrazide ligand coordinates to the copper center in the enolic form (–CN–N). In complex 1, the two bridging azide ligands connect the two metal centers in an end-on (EO) fashion, with the metal centers having an asymmetric square pyramidal geometry. Complex 2b is based on a square pyramid with the neutral isonicotinohydrazide ligand coordinating in a tridentate mode. By contrast, the Schiff base (L)− coordinates in a tetradentate ligand fashion in 2a as the oxygen atom of the amide unit in the enol form asymmetrically bridges two Cu centers and a third Cu center is coordinated through the pyridyl-N atom. The EPR spectrum of complex 2a, consisting of two poorly resolved resonance lines, points to the presence of a dynamical Jahn–Teller effect, typical for Cu2+ ions in octahedral environments.

Impact of Regiochemistry and Isoelectronic Bridgehead Substitution on the Molecular Shape and Bulk Organization of Narrow Bandgap Chromophores

A comparison of two classes of small molecules relevant to the field of organic electronics is carried out at the molecular and supramolecular levels. First, two molecules that differ only in the position of a pyridyl N-atom within an acceptor fragment are compared and contrasted. X-ray investigation of single crystals reveals that positioning the pyridyl N-atoms proximal to the molecules center changes the molecular shape by bending the molecule into a banana shape. Second, we demonstrate that the banana shape of the molecule can be controlled by replacing a Si atom within the dithienosilole fragment with a C or Ge atom. Here, utilization of cyclopentadithiophene or dithienogermole as the internal electron-rich unit leads to a decrease or an increase in the bending of the conjugated backbone, respectively. Such molecular shape changes alter intermolecular packing and thus affect bulk properties, leading to large differences in the optical, thermal, and crystallization properties.

N-Butyldichlorido{4-cyclohexyl-1-[1-(pyridin-2-yl-κN)ethylidene]thiosemicarbazidato-κ2N1,S}tin(IV)

Two independent mol­ecules comprise the asymmetric unit in the title compound, [Sn(C4H9)(C14H19N4S)Cl2]. In each mol­ecule, the SnIV atom exists within a distorted octa­hedral geometry defined by the N,N′,S-tridentate mono-deprotonated Schiff base ligand, two mutually trans Cl atoms, and the α-C atom of the n-butyl group; the latter is trans to the azo-N atom. The greatest distortion from the ideal geometry is found in the nominally trans angle formed by the S and pyridyl-N atoms at Sn [151.72 (7) and 152.04 (7)°, respectively]. In the crystal, mol­ecules are consolidated into a three-dimensional architecture by a combination of N—H⋯Cl, C—H⋯π and π–π inter­actions [inter-centroid distances = 3.6718 (19) and 3.675 (2) Å].

Crystal and Molecular Structures of the 2:1 Cocrystal of 4-Nitrophenylacetic acid and N,N′-bis(pyridin-3-ylmethyl)oxalamide, and with the Thioxalamide Analogue

The common feature of each of the title 2:1 cocrystals is the formation of the O–H···N(pyridyl) hydrogen bonds leading to three-molecule aggregates. The persistent formation of the O–H···N(pyridyl) hydrogen bonds where other functionalities are present, e.g. amide, indicates the robustness of this supramolecular synthon. In the structure of the 2:1 4-nitrophenylacetic acid N,N′-bis(pyridin-3-ylmethyl)oxalamide cocrystal, (1), the amide-H forms a hydrogen bond with the hydroxyl group so that rows of N,N′-bis(pyridin-3-ylmethyl)oxalamide molecules are linked into a supramolecular tape via 4-nitrophenylacetic acid molecules. In the N,N′-bis(pyridin-3-ylmethyl)thioxalamide derivative, (2), the thioamide-H atom only forms an intramolecular N–H···S contact. Nevertheless, a supramolecular tape is formed but mediated by C–H···O(nitro) interactions. Compound (1) crystallizes in the triclinic space group P¯1 with a = 8.195(2) A, b = 9.502(3) A, c = 9.999(3) A, α = 90.631(3)o, β = 102.796(5)o, γ = 108.075(5)o, and Z = 1 (three molecule aggregate). Compound (2) also crystallizes in the triclinic space group P¯1 with a = 8.0772(12) A, b = 10.2111(12) A, c = 10.2563(17) A, α = 71.319(10)o, β = 77.777(11)o, γ = 67.660(9)o, and Z = 1 (three molecule aggregate). In each cocrystal the carboxylic acid-OH interacts with the pyridyl-N atom via a hydrogen bond to result in a three-molecule aggregate. In the N,N′-bis(pyridin-3-ylmethyl)oxalamide cocrystal, these are linked into a chain via amine-H···O(carboxylic acid) interactions.

Synthesis, spectral characterization and biological activities of Organotin(IV) complexes with &amp;lt;i&amp;gt;ortho&amp;lt;/i&amp;gt;-vanillin-2-hydrazinopyridine (VHP)

Five new organotin(IV) complexes of ortho-vanillin-2-hydrazinopyridine hydrazone with formula [RnSnCl4–n(VHP)] [R = Me2, n = 2 (2); R = Ph2, n = 2 (3); R= nBu2, n = 2 (4); R = nBu, n = 2 (5) and R = 1, n = 0 (6)] have been synthesized by direct reaction of ortho-vanillin-2-hydrazinopyridine hydrazone [(VHP), (1)], base and organotin(IV) chloride(s) in absolute methanol. The hydrazone ligand [(VHP), (1)] and its organotin(IV) complexes (2-6) have been characterized by UV-Visible, FT-IR and 1H NMR spectral studies. Spectroscopic data suggested that in the complexes (2-4), the ligand (1) acted as a neutral bidentate ligand and is coordinated to the tin(IV) atom via the azomethine nitrogen and pyridyl nitrogen atoms, whereas the ligand (1) acted as a uninegative tridentate ligand and coordinated to the tin(IV) atom through phenolic-O, azomethine-N and pyridyl-N atoms in complexes (5-6). The toxicity of the ligand (1) and its organotin (IV) complexes (2-6) were determined against Artemia salina. Organotin(IV) complexes showed moderate activity against Artemia salina. The ligand (1) and its organotin(IV) complexes (2-6) were also tested against four types of bacteria namely Bacillus cereus, Staphylococcus aureus, Escherichia coli and Enterobacter aerogenes. All organotin(IV) complexes and the free ligand (1) showed better antibacterial activities against bacteria. Among the organotin(IV) complexes (2-6), diphenyltin(IV) complex (3) showed higher activity against the four types of bacteria.

Poly[[tetraaquatetrakis[μ3-5-(pyridine-4-carboxamido)isophthalato]cobalt(II)digadolinium(III)] tetrahydrate

In the centrosymmetric polymeric title compound, {[CoGd2(C14H8N2O5)4(H2O)4]·4H2O}n, the GdIII cation is coordinated by one water mol­ecule and four pyridine-4-carboxamido­isophthalate (L) anions in a distorted square-anti­prismatic arrangement, while the CoII cation, located on an inversion center, is coordinated by two pyridyl-N atoms, two carboxyl­ate-O atoms and two water mol­ecules in a distorted octa­hedral geometry. The asymmetric unit contains two anionic L ligands: one bridges two Gd cations and one Co cation through two carboxyl groups and one pyridine-N atom; the other bridges two Gd cations and one Co cation through two carboxyl groups and the uncoordinated pyridine-N atom is hydrogen-bonded to the adjacent coordinated water mol­ecule. Extensive O—H⋯O and N—H⋯O hydrogen bonds are present in the crystal structure.

Dichlorido{4-cyclohexyl-1-[1-(2-pyridyl-κN)ethylidene]thiosemicarbazidato-κ2N1,S}phenyltin(IV)

The SnIV atom in the title compound, [Sn(C6H5)(C14H19N4S)Cl2], exists within a distorted octa­hedral geometry defined by the N,N′,S-tridentate monodeprotonated Schiff base ligand, two mutually trans Cl atoms, and the ipso-C atom of the Sn-bound phenyl group; the latter is trans to the azo-N atom. The greatest distortion from the ideal geometry is found in the nominally trans angle formed by the S and pyridyl-N atoms at Sn [151.03 (4)°]. With the exception of the cyclo­hexyl group (chair form), the Schiff base ligand is almost planar (r.m.s. deviation of non-H and Sn atoms = 0.053 Å). The nearly orthogonal orientation of the Sn-bound phenyl group [N—Sn—C—C torsion angle = 70.8 (5)°] to the planar portion of the Schiff base allows for the formation of significant intra­molecular C—H⋯Cl inter­actions which preclude the Cl atoms from participating in N—H⋯Cl hydrogen bonds. Instead, C—H⋯π contacts, involving methyl­ene H and the Sn-bound phenyl group, lead to the formation of supra­molecular chains that pack in the bc plane. Connections between these layers are of the type C—H⋯Cl.

(Di-2-pyridylamine)(methanol)sulfatocopper(II)

The title complex, [Cu(SO4)(C10H9N3)(CH3OH)], is a mononuclear species with the CuII ion in a Jahn–Teller-distorted ‘4 + 1’ square-pyramidal geometry. The basal plane is defined by the pyridyl N-atom donors of the bipyridyl­amine (bpa) ligand and two O-atom donors of the sulfate ligand. The coordination geometry is completed by the axial coordination of a methanol O-atom donor. The axial bond length displays the usual elongation: Cu—O(axial) = 2.168 (2), Cu—O(basal) = 2.016 (2) (average) and Cu—N(basal) = 1.951 (3) Å (average). In the crystal structure, the complex mol­ecules are linked through N—H⋯O and O—H⋯O hydrogen bonds into chains along [100].

ChemInform Abstract: Inhibitor of HIV-1 Reverse Transcriptase: N′-(5-Bromo-2-pyridyl)-N-[2-(2,5-dimethoxyphenyl)ethyl]thiourea.

The crystal structure of the title compound, C 16 H 18 Br-N 3 O 2 S (HI-236), a potent non-nucleoside inhibitor of HIV-1 reverse transcriptase, revealed an intramolecular hydrogen bond between a thiourea N atom and the pyridyl-N atom [N-H...N= 2.671(3) A, graph-set motif S](6)] that imparts a more rigid conformation to the molecule. A second hydrogen bond between a thiourea N atom and the thiocarbonyl-S atom [N-H2...S = 3.403(2) A, graph-set motif R 2 2 (8)] was observed between inversion-related molecules of HI-236. The first-level hydrogen-bond graph-set notation for HI-236 was determined to be S](6)R 2 2 (8).

4,4′-Methylenediphenol–4,4′-bipyridine (2/3): decarboxylation of 5,5′-methylenedisalicylic acid under hydrothermal conditions

Reaction of 5,5'-methylenedisalicylic acid (5,5'-H(4)mdsa) with 4,4'-bipyridine (4,4'-bipy) and manganese(II) acetate under hydrothermal conditions led to the unexpected 2:3 binary cocrystal 4,4'-methylenediphenol-4,4'-bipyridine (2/3), C(13)H(12)O(2).1.5C(10)H(8)N(2) or (4,4'-H(2)dhdp)(4,4'-bipy)(1.5), which is formed with a concomitant decarboxylation. The asymmetric unit contains one and a half 4,4'-bipy molecules, one of which straddles a centre of inversion, and one 4,4'-H(2)dhdp molecule. O-H...N interactions between the hydroxy and pyridyl groups lead to a discrete ribbon motif with an unusual 2:3 stoichiometric ratio of strong hydrogen-bonding donors and acceptors. One of the pyridyl N-atom donors is not involved in hydrogen-bond formation. Additional weak C-H...O interactions between 4,4'-bipy and 4,4'-H(2)dhdp molecules complete a two-dimensional bilayer supramolecular structure.

Inverse bilayer structure of mononuclear CoII and NiII complexes of the type M(H2O)3(SO4)(4-CNpy)2

Two new metal compounds of the formula [M(H(2)O)(3)(SO(4))(4-CNpy)(2)] x H(2)O [M = Ni (1) and Co (2), 4-CNpy = 4-cyanopyridine] have been prepared and studied by X-ray diffraction. In both of these compounds the 4-CNpy ligands are coordinated via pyridyl-N atoms to the metal ions in a cis fashion. The neutral complexes along with the uncoordinated H(2)O molecules are glued together preferentially into inverse bilayers by non-covalent interactions, including unique interlayer pi-pi interactions between antiparallel nitrile groups. Hartree-Fock and density-functional theory (DFT) calculations indicate that the pi-pi interactions are energetically significant. The unit-cell similarity index (Pi) of 0.0046 for the compounds suggests their isostructurality, which is also supported by their X-ray powder diffraction patterns that can be almost superimposed.

Syntheses and Crystal Structures of Two Novel 1D Complexes of Zinc(II) with Terephthalato-bridge

Two novel complexes [Zn(NIT3-py)(tp)]n 1 and [Zn(im3-py)(tp)]n 2 (NIT3-py = 2-(3′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, im3-py = 2-(3′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, tp = terephthalato) have been synthesized and structurally determined by X-ray diffraction analysis. Complex 1 is, monoclinic, space group P2/c, with a = 12.6459(14), b = 6.9110(8), c = 20.0376(17) A, β = 112.030(5), V = 1623.3(3) A3 with Z = 2, for d calc = 1.428 Mg/m3. The analog 2 is, monoclinic, space group P2/n, with a = 12.2313(15), b = 6.8478(9), c = 19.908(3) A, β = 107.368(2), V = 1591.4(3) A3, with Z = 2 for d calc = 1.390 Mg/m3. X-ray analysis reveals that both Zn(II) ions are four-coordinated by two carboxylate oxygen atoms and two pyridyl-N atoms from nitroxide radicals to form a tetrahedron geometry. Each terephthalate dianion bridges two Zn(II) ions in bis-monodentate mode, resulting in a 1D chain structure. Two New Zinc(II) Nitroxide Radical Complexes bridged by terephthalate have been synthesized and structurally determined by X-ray diffraction analysis, the description of which is shown in the text.

Neighbouring metal induced oxidative addition at the iron centre amongst the iron–arylpyridylphosphine complexes

Complexes of the type (η 4-BuC 5H 5)Fe(CO) 2( P) ( P = PPh 2Py 3, PPhPy 2 4, PPy 3 5; Py = 2-pyridyl) were satisfactorily prepared. Upon treatment of 3 with M(CO) 3(EtCN) 3 (M = Mo, 6a; W, 6b), the pyridyl N-atom could be coordinated to the metal M, which then eliminates a CO ligand from the Fe-centre and induced an oxidative addition of the endo-C–H of (η 4-BuC 5H 5). This results in a bridged hydrido heterodimetallic complex [(η 5-BuC 5H 4)Fe(CO)(μ- P, N-PPh 2Py)(μ-H)M(CO) 4] (M = Mo, 7a, 81%; W, 7b, 76%). The reaction of 4 or 5 with 6a, b did not give the induced oxidative addition, although these complexes contain more than one pyridyl N-atom. The reaction of 4 with M(CO) 4(EtCN) 2 (M = Mo, 9a; W, 9b) produced heterodimetallic complexes [(η 4-BuC 5H 5)Fe(CO) 2(μ- P: N, N′-PPhPy 2)M(CO) 4] (M = Mo, 10a, 81%; W, 10b, 83%). Treatment of 5 with 6a, b gave [(η 4-BuC 5H 5)Fe(CO) 2(μ- P: N, N′, N″-PPy 3)M(CO) 3] (M = Mo, 12a, 96%; W, 12b, 78%).

Structural and functional mimic of galactose oxidase by a copper complex of a sterically demanding [N2O2] ligand

A structural and functional mimic of the galactose oxidase (GOase) enzyme active-site by a copper complex supported over a sterically demanding ligand having [N2O2] donor sites is reported. Specifically, the binding of the histidine (496 and 581) and tyrosine (272 and 495) residues to the copper center in a square-pyramidal fashion in the active-site of galactose oxidase (GOase) enzyme has been modeled in a copper complex, ([(3-tert-butyl-5-methyl-2-hydoxybenzyl)(3'-tert-butyl-5'-methyl-2'-oxobenzyl)(2-pyridylmethyl)]amine)Cu(OAc)) (1b), stabilized over a sterically demanding ligand in which the two phenolate-O atoms mimicked the tyrosine binding while an amine-N and pyridyl-N atoms emulated the histidine binding to the metal center, similar to that in the enzyme active-site. Furthermore, the copper complex 1b is found to be an effective functional model of the enzyme as it efficiently catalyzed the chemoselective oxidation of primary alcohols to aldehydes in high turnover numbers under ambient conditions. An insight into the nature of the active-species was obtained by EPR and CV studies, which in conjunction with the DFT studies, revealed that the active-species is an anti-ferromagnetically coupled diamagnetic radical cation, (1)1b+, obtained by one electron oxidation at the equatorial phenolate-O atom of the ligand in the 1b complex.

Carrier generation and carrier determination in dipyridyldiketopyrrolopyrrole-based H2 gas sensors

Operation mechanism of dipyridyldiketopyrrolopyrrole (DPPP)-based H2 sensor has been investigated with special attention to the electric-field-assisted dissociation of H2 in the presence of Pd or Pt, as well as the carrier generation and carrier determination. H2 is found to dissociate exponentially with an increase of the electric field above 102–3V∕cm as monitored by an electric current. The dissociation is greatly enhanced by the presence of DPPP which serves as a proton acceptor due to its pyridyl-N atom. The detection of H2 starts with dissociation of H2, followed by protonation of atomic hydrogen (H) at the N atom of the pyridyl ring of DPPP, ending up with a release of an electron which contributes to the electrical conduction: H+pyridyl ring→protonated pyridyl ring (N+–H)+e′. The electron conduction is confirmed by the Seebeck effect. Judging from the above process, the atomic hydrogen is pictured as an electron donor. However, the present doping is rather characterized by an instantaneous one, since the extent of doping depends on the ambient H2 concentration.