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Abstract: The scattering of a bound Frohlich large polaron in the presence of a coulomb impurity center as well as a linearly polarized laser field is studied. The differential (DCS) as well as the momentum transfer cross sections (MTCS) and the conductivity depend remarkably on the electron–phonon coupling ( ) and the strength of the coulomb impurity ( ). The strongly bound polaron is found to be reluctant to contribute to the conductivity which is justified physically. The curves for MTCS and conductivity verses and appear to be complementary, indicating the possibility of controlling the mobility and thereby conductivity by varying one of the parameters. This behavior indicates the possibility of optimizing the composition of optoelectronic materials where laser is the dominant source of excitation. [Copyright &y& Elsevier]

Abstract: A new series of group 6 carbonyl complexes of N-[(2-pyridyl)methyliden]-α (or β)-aminonaphthalene (α/β-NaiPy) are described in this work. The complexes are formulated as cis-[M(CO)4(α/β-NaiPy)] by elemental, mass and other spectroscopic data. The complexes show emission spectra at room temperature and their quantum yield lies between 0.4 and 0.5. All the complexes exhibit negative solvatochromism. Cyclic voltammetry shows metal centred oxidation and ligand reductions. [Copyright &y& Elsevier]

Abstract: Background: Opiate use in pregnancy is on the increase. There are a number of complications associated with this problem but current data from UK centres are sparse. Design: A retrospective study. Setting: A North of England Hospital. Methods: Maternal and neonatal case records were studied and a standard data set completed. Main outcome measures: Maternal and neonatal outcomes were classified by the woman''s drug usage at the end of pregnancy. Results: One hundred and ten babies born to 108 women were studied and 41% had evidence of previous exposure to the hepatitis C virus. Women who took heroin in later pregnancy were significantly more likely than women who were stabilised on methadone to have a baby who needed morphine (40% versus 19%), had higher mean maximum neonatal abstinence scores (NAS) (5.8 versus 4.7) and stayed in the neonatal unit significantly longer (mean 17.2 days versus 11.8days). There were two neonatal deaths and the overall rate of prematurity was 29%. Conclusions: The outcome for pregnancy in women who use opiates is complicated by high rates of prematurity and neonatal death. Women who used heroin in later pregnancy had babies who developed more severe NAS and needed a longer hospital stay than women who used only methadone. [Copyright &y& Elsevier]

Abstract: The tunneling escape rate is calculated on the basis of ballistic miniband transport of electron in the presence of external electric field. The variation of the miniband escape rate is reported as functions of barrier and well widths as well as the externally applied bias. Interesting features with regard to the electric field modulation are observed in the semiconductor heterostructures with small barrier and well widths. For the system with constant periodic length, the maximum confinement of carriers is found for the well width almost equal to half of the barrier width. [Copyright &y& Elsevier]

We investigate theoretically the transmission of electrons through a pair of δ-function magnetic barriers in graphene in presence of external monochromatic, linearly polarized and CW laser field. The transmission coefficients are calculated in the framework of non-perturbative Floquet theory using the transfer matrix method. It is noted that the usual Fabry–Perot oscillations in transmission through the graphene magnetic barriers with larger inter barrier separation takes the shape of beating oscillations in presence of the external laser field. The laser assisted transmission spectra are also found to exhibit the characteristic Fano resonances (FR) for smaller values of the inter barrier separation. The appearance of the perfect node in the beating oscillation and the asymmetric Fano line shape can be controlled by varying the intensity of the laser field. The above features could provide some useful and potential information about the light - matter interactions and may be utilized in the graphene based optoelectronic device applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Importance of 1H-2(Phenylazo) imidazole (PaiH) molecule is discussed. [•] Interaction of PaiH with silver nano particles is possibly through theN3 atom. [•] Concentration dependent dark isomerisation (trans-to-cis) is suggested. [•] DFT calculations are in good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of HgX2 (X=Cl, Br, I) with 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole (SRaaiNR′) in MeOH-ethyleneglycol mixture has synthesised [Hg(SRaaiNR′)X2]. The structure of the products has been established by microanalytical and spectral (IR, UV–Vis, 1H NMR) data, and a distorted Td-geometry has been confirmed by a single crystal X-ray diffraction study of [Hg(SMeaaiNEt)I2] (SMeaaiNEt=1-ethyl-2-{(o-thiomethyl)phenylazo}imidazole). The UV light irradiation in CH3CN solution of the complexes shows E-to-Z (E and Z refer to trans and cis-configurations) isomerisation of the coordinated SRaaiNR′ ligand about the –N bond. The rate of isomerisation follows: [Hg(SRaaiNR′)Cl2]<[Hg(SRaaiNR′)Br2]<[Hg(SRaaiNR′)I2]. The quantum yields (ϕE → Z ) of the isomerisation of the complexes are lower than those of the free ligands. These may be due to increased mass and rotor volume of the complexes. The electronegativity sequence of X (I

Abstract: A theoretical model is proposed to study the ballistic electron transport for a quasi-periodic multibarrier structure where two different barrier shapes are arranged according to the Thue–Morse sequence. Important tunneling features are revealed form such arrangements. It is noted that the tunneling band spectrum could be fragmented by tailoring the shape of the barriers in the structure. Results for the transmission coefficients and the current densities are compared with the corresponding periodic and single shape barrier arrangements. The quasi-periodic structure consisting of the rectangular and triangular barrier shapes is suggested to be more suitable for the electronic and opto-electronic devices due to its high negative differential conducting effect. [Copyright &y& Elsevier]

Abstract: Dynamics of the Dirac fermions, in particular the transmission coefficient and the resonant tunneling lifetime are studied across a bilayer graphene electrostatic double barrier structure modulated by an in plane homogeneous electric field. Asymmetric Fano type resonances are noted for the first time in the transmission spectrum of the bilayer graphene nanostructures and are found to be highly sensitive to the direction of incidence of the charge carriers and the applied homogeneous electric field. The effect of the external field on the extended and the evanescent modes is also analysed. Resonant tunneling lifetime is found to be highly anisotropic in nature. The chiral carriers are either accelerated or decelerated by the electric field depending on the energy of the quasi-bound states, the angle of incidence and the magnitude of the applied field. Effects of the external field on the localization of the chiral carriers are also discussed. [Copyright &y& Elsevier]

Abstract: The effects of the external homogeneous electric field on the transmission coefficient and the ballistic conductance are studied theoretically for an electron across a graphene double barrier structure. The Klein transmission is noted for the normal to near normal incidence only. The electrons are found to be confined by the external static electric field for the glancing incidence and not for the normal incidence. Although the conductance profile for the lower barrier widths is almost sinusoidal in nature, some interesting features occur for the higher barrier width of the structure. The oscillations in the below barrier conductance are greatly suppressed by the external field. Some negative differential conducting regions are also noted, being quite sensitive to the Fermi energy of the system. [Copyright &y& Elsevier]

Abstract: A new series of Cr(0)- and Mo(0)-carbonyl complexes of 1-alkyl-2-(naphthyl-α/β-azo)imidazoles (α/β-NaiR′) are described in this work. The complexes are formulated cis-[M(CO)4(α/β-NaiR′)] by elemental, mass and other spectroscopic data. The complexes are stable and exhibit emission spectra at room temperature. Cyclic voltammetry shows two metal centred oxidations, M+/M0 and M2+/M+, and two ligand centred reductions, azo/azo− and azo−/azo=. [Copyright &y& Elsevier]

Reaction of ctc-OsBr2(RaaiR′)2 [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N&z.dbnd6;N-C3H2-NN-1-R′, where R=H (a), Me (b), Cl (c) and R′=Me (2), Et (3) and CH2Ph (4)] with 2,2′-bipyridine (bpy) in presence of AgNO3 in EtOH followed by the addition of NH4PF6 afforded a mixed ligand complex [Os(bpy)(RaaiR′)2](PF6)2. The structure of the complex, in one case [Os(bpy)(MeaaiMe)2](PF6)2 · 4H2O, has been confirmed by X-ray crystallography. The complexes are diamagnetic (low spin d6, s=0) and they show intense MLCT transition in the visible region (480–525 nm) and a weak transition at longer wavelength (>850 nm) in CH3CN solution. Cyclic voltammetry of the complexes show two metal oxidation, Os(II)/Os(III) at 0.72–0.76 V and Os(III)/Os(IV) at 1.34–1.42 V and three successive ligand reductions. [Copyright &y& Elsevier]

1-Alkyl-2-(naphthyl-(α/β)-azo)imidazole [α-NaiR (2)/β-NaiR (3); R=Me (a), Et (b), CH2Ph (c)] are N,N′-bidentate chelating ligands. The structure of 1-ethyl-2-(naphthyl-α-azo)imidazolium hexaflurophosphate has been confirmed by single crystal X-ray structure study and shows supramolecular geometry through non-covalent interactions (C–H⋯F, C–H⋯π, π⋯π). Mercury(II) complexes of the formula Hg(NaiR)Cl2 (4/5) have been synthesised and characterised by spectral (IR, UV–Vis and 1H and 13C NMR) studies. α-NaiR has been used to synthesise organomercury derivatives, Hg(α-NaiR–H)Cl (6) and the site of mercuration has been supported by charge density calculation using a semi-empirical PM3 technique. [Copyright &y& Elsevier]

Graphical abstract Phosphino bridged Ag(I) complex of 1-alkyl-2-(arylazo)imidazole is structurally characterized and UV light irradiation initiates trans -to- cis isomerisation. Reverse is also carried out by heat treatment. Rate of photoisomerisation of free ligand is faster than coordinated ligand which may be due to higher molar mass of the associated photochrome. Highlights • Diphenylphosphino bridging Ag(I)-dimer complex of arylazoimidazoles. • Single crystal X-ray structure of one of the complexes was established. • Coordinated arylazoimidazole undergoes UV-light irradiated photoisomerisation. • Free ligand shows higher rate of trans -to- cis photoisomerisation that that of complex phase. • Reverse process, cis -to- trans isomerisation is thermally controlled. Abstract The coordinated 1-alkyl-2-(arylazo)imidazole (RaaiR/) in [Ag(μ-dppm)(RaaiR/)] 2 (PF 6) 2 (dppm, bis-(diphenylphosphino)methane) undergoes light induced trans -to- cis isomerization about N N bond. The quantum yields (ϕ t→c) of trans -to- cis isomerization of coordinated RaaiR/ in the complex is lower than the free ligand data. The reverse transformation, cis -to- trans , is carried out at different temperatures (298–313 K) and activation energy (E a) has been calculated. It is found that E a (free ligands) > E a (coordinated ligand in the complexes). The structures of the complexes have been established by spectral (UV–Vis, IR, and 1H NMR) data. One of the complexes, [Ag(μ-dppm)(HaaiEt)] 2 (PF 6) 2 has been structurally confirmed by single crystal X-ray diffraction study. [ABSTRACT FROM AUTHOR]

Transmission profiles in bilayer graphene are studied theoretically through a rectangular vector potential (magnetic) barrier with and without the presence of an oscillatory potential. Unlike the electrostatic barrier, the Fano resonances (FR) are noted in the transmission spectra both for normal and glancing incidences due to non-conservation of chirality for a static vector barrier. The results for normal incidence indicate that the cloaking effect is a manifestation of the chirality conservation in charge transport through bilayer graphene scalar barriers. It is also noted that the aforesaid FR for a static vector barrier might disappear (photon induced electronic cloaking effect) due to the predominant photon exchange processes in presence of an external oscillating potential. The study of Fano resonances in transmission spectrum is in high demand in respect of localization of charge carriers in graphene nano structures for its potential applications in digital device fabrications. [ABSTRACT FROM AUTHOR]

Electronic transport through graphene magnetic barriers is studied theoretically in presence of an external time harmonic scalar potential in the framework of non-perturbative Landau–Floquet Formalism. The oscillating field mostly suppresses the transmission for rectangular magnetic barrier structure and exhibits the Fano resonance for multiphoton processes due to the presence of bound state inside the barrier. While, for a pair of delta function barriers of larger separation, the oscillating potential suppresses the usual Fabry–Perot oscillations in the transmission and a new type of asymmetric Fano resonance is noted for smaller separation, occurring due to extended states between the barriers. [ABSTRACT FROM AUTHOR]

Abstract: 1-Alkyl-2-{(o-thioalkyl)phenylazo}imidazole acts as imidazolyl-N donor ligand to Cd(II) although they have potential three donor centres namely N(imidazole), N(azo) and –SR. Two series of complexes [Cd(SRaaiNR/)2X2] (X=Cl, Br, I) and [Cd(SRaaiNR/)4](ClO4)2 are synthesized with these ligands. These complexes are spectroscopically (IR, UV–Vis, 1H NMR) characterised and, the single crystal X-ray structures of [Cd(SEtaaiNEt)2I2] and [Cd(SEtaaiNEt)4](ClO4)2 (where SEtaaiNEt=1-ethyl-2-{(o-thioalkyl)phenylazo}imidazole) have confirmed the distorted tetrahedral structures. The UV light irradiation in MeCN solution of the complexes shows E-to-Z (E and Z refer to trans and cis-configuration about –N, respectively) isomerisation of the coordinated azoimidazole. The rate of isomerisation follows the sequence : [Cd(SRaaiNR/)4](ClO4)2 <[Cd(SRaaiNR/)2Cl2]<[Cd(SRaaiNR/)2Br2]<[Cd(SRaaiNR/)2I2]. Quantum yields (ϕE → Z ) and the activation energy (E a) of the isomerisation of the complexes are lower than that of free ligand data. The observation has been explained considering the molecular association that increases the mass and rotor volume of the complexes. [Copyright &y& Elsevier]

Abstract: Halide bridging lead(II) coordination polymer of 1-alkyl-2-(arylazo)imidazole (RaaiR′), [Pb(RaaiR′)(μ-X)2] n is spectroscopically characterized and, the single crystal X-ray structure of [Pb(MeaaiMe)(μ-Cl)2] (where MeaaiMe=1-methyl-2-(p-tolylazo)imidazole) has confirmed the structure. The UV light irradiation in DMF solution of the complexes shows E-to-Z (E and Z refer to trans and cis-configuration about –N, respectively) isomerization of the coordinated azoimidazole. The rate of isomerization follows: [Pb(RaaiR′)(μ-Cl)2] n <[Pb(RaaiR′)(μ-Br)2] n <[Pb(RaaiR′)(μ-I)2] n . Quantum yields (ϕ E→Z) and the activation energy (E a) of the isomerization of the complexes are lower than that of free ligand data. These may be due to increased mass and rotor volume of the complexes. The results are supported by DFT computation of optimized structures. [Copyright &y& Elsevier]

Abstract: Reaction of Cu(ClO4)2·6H2O, SRaaiNR′ (1-alkyl-2-[(o-thioalkyl)phenylazo]imidazole) and NH4SCN (1:1:2mol ratio) affords distorted square pyramidal, [CuII(SRaaiNR′)(SCN)2] (3) compound while identical reaction with [Cu(MeCN)4](ClO4) yields –SCN– bridged coordination polymer, [CuI(SRaaiNR′)(SCN)] n (4). These two redox states [CuII and CuI] are interconvertible; reduction of [CuII(SRaaiNR′)(SCN)2] by ascorbic acid yields [CuI(SRaaiNR′)(SCN)] n while the oxidation of [CuI(SRaaiNR′)(SCN)] n by H2O2 in presence of excess NH4SCN affords [CuII(SRaaiNR′)(SCN)2]. They are structurally confirmed by single crystal X-ray diffraction study. Cyclic voltammogram of the complexes show Cu(II)/Cu(I) redox couple at ∼0.4V and azo reductions at negative to SCE. UV light irradiation in MeCN solution of [CuI(SRaaiNR′)(SCN)] n (4) show trans-to-cis isomerisation of coordinated azoimidazole. The reverse transformation, cis-to-trans, is very slow with visible light irradiation while the process is thermally accessible. Quantum yields (ϕ t→c) of trans-to-cis isomerisation are calculated and free ligands show higher ϕ than their Cu(I) complexes. The activation energy (E a) of cis-to-trans isomerisation is calculated by controlled temperature experiment. Copper(II) complexes, 3, do not show photochromism. DFT and TDDFT calculation of representative complexes have been used to determine the composition and energy of molecular levels and results have been used to explain the solution spectra, photochromism and redox properties of the complexes. [ABSTRACT FROM AUTHOR]

Abstract: Protonation or dialkylation of 2-(arylazo)imidazoles (RaaiH) has generated azoimidazolium motif (RaaiH2 +, RaaiR′H+, RaaiR′ 2 + where R=H, CH3 and R′ =Me, Et, –CH2Ph). Electrostatic attraction between imdazolium cation and counter ions like Cl−, , has generated hydrogen bonded azoimidazolium-chloride/chlorometallated networks. The single crystal X-ray structure of 1-benzyl-2-(phenylazo)imidazolium chloride shows tape like 1-D network of [Cl(H2O)4]−. Aquated Cl− forms 10 membered supracycle through hydrogen bonding with imidazolium ion. The X-ray structures of [HaaiMe2 (1,3)]+[Me2NH2]+ [ZnCl4]2− and [MeaaiH2 +·H2O]2[PtCl6]2− show hydrogen bonded chlorometallate chain penetrated into the channel developed by organic motif. Azoimidazolium units are associated through π···π and C–H···π interactions to strengthen the supramolecular geometry. [Copyright &y& Elsevier]

Abstract: The reaction of CuX (X=Cl, Br, I) with a mixture of PPh3 and 1-alkyl-2-(naphthyl-α/β-azo)imidazole has synthesized mixed ligand complexes of the composition, [Cu(α/β-NaiR)(PPh3)X]. The spectroscopic characterization (IR, UV–Vis, 1H NMR) supports this formulation. The single crystal X-ray diffraction study of [Cu((α-NaiMe)(PPh3)I] (7a) (α-NaiMe=1-methyl-2-(naphthyl-α-azo)imidazole) shows a distorted tetrahedral geometry about Cu(I). Cyclic voltammograms of the complexes show a high potential Cu(II)/Cu(I) couple and azo reductions. The [Cu(α/β-NaiR)(PPh3)I] complexes show an additional oxidative response at 0.4V that is assigned to I/I− A sharp anodic peak at ∼−0.2V is assigned to the oxidation of metallic Cu, deposited on electrode surface upon scanning to the negative side of the SCE. DFT and TD-DFT computations of [Cu((α-NaiMe)(PPh3)I] (7a), [Cu((α-NaiMe)(PPh3)I]+ (7a+ ) and [Cu((α-NaiMe)(PPh3)I]− (7a− ) were carried out to examine the electronic configuration and to explain the spectral and redox properties of the complexes. [Copyright &y& Elsevier]

Abstract: The reaction of Pd(β-NaiR)Cl2 (2) [β-NaiR (1)=1-alkyl-2-(naphthyl-β-azo)imidazoles] with ArNH2 in MeCN has yielded a C–N coupled product chloro[1-alkyl-2-{(7-imidoaryl)naphthyl-β-azo}imidazole-N,N′,N′′]palladium(II), Pd(β-NaiR–N–Ar)Cl (3–5) and coupling takes place at ortho-C–H position of pendant naphthyl group. The structural confirmation has been achieved by single crystal X-ray structure determination of the representative complexes, Pd(β-NaiEt)Cl2 (2b) and Pd(β-NaiEt–N–C6H4–Cl-p)Cl (5b). The electronic spectra of the products, 3–5, exhibit characteristic transition within 600–900nm those are absent in Pd(β-NaiR)Cl2 (2). Cyclic voltammogram shows one oxidative response and two ligand reductions. The products are emissive. The excited state decays via radiative and non-radiative biexponential routes. The electronic structure, spectra and redox properties are explained by DFT computation. [Copyright &y& Elsevier]

Abstract: The complexes, cis-(CO)-trans-(Cl)-[Ru(SRaaiNR)(CO)2Cl2] (2) and trans-(Cl)-[Ru(SRaaiNR)(CO)Cl2] (3) (SRaaiNR=1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles; R=Me (1a) and Et (1b)) have been synthesized and characterized. The structural confirmation is achieved by single crystal X-ray structure determinations. The complexes show Ru(III)/Ru(II) couple and ligand reductions. Electronic structure and spectral properties of the complexes have been explained with the DFT and TDDFT calculation. [Copyright &y& Elsevier]

Abstract: 1,3-Di-alkyl-2-(arylazo)imidazolium iodide () has been used to prepare iodocuprate(I) and iodoargentate(I) complexes. The structural confirmation has been carried out by single crystal X-ray diffraction study in representative cases. Iodo bridged anion, [Cu2(μ-I)2I2]2−, serves as charge support to dialkylazoimidazolium ion (). Silver(I) compound is a trimeric iodo-bridged [Ag3I5]2− that forms 1D chain while imidazolium ion, , is penetrating into the network. Electrostatic interaction between organic cation and inorganic anion and supramolecular interactions viz. hydrogen bonding, D–H–π, π–π interactions contribute to the crystal packing. [Copyright &y& Elsevier]

Abstract: 1-Alkyl-2-{(o-thioalkyl)phenylazo}imidazole (SRaaiNR/, 1) reacts with Co(ClO4)2·6H2O to form [Co(SRaaiNR/)2](ClO4)2 (2). The single crystal X-ray structure of one of the complexes of 2 shows a tridentate chelation N(imidazole), N(azo), S(thioether) system. In the structure one of ClO4 − anions shows disorder and forms an (imidazole)C–H···O(ClO3) interaction leading to a 1-D chain. Co(OAc)2.4H2O and SRaaiNR/ react in the presence of NH4SCN (1:1:2 mole ratio) in methanol and the complex [Co(SRaaiNR/)2(SCN)2] (3) has been separated. The single crystal X-ray structure determination has established the structure of the complexes in which the ligand SRaaiNR/ acts in a bidentate N(imidazole), N(azo) chelation mode. A cyclic voltammogram shows a Co(III)/Co(II) oxidative response at 0.6–0.8V and azo reductions. DFT computation using optimized geometry support the electronic spectral and redox properties of the complexes. [Copyright &y& Elsevier]

Abstract: The reaction of 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles (SRaaiNR) (2a/2b) with Ru(II) has synthesized [Ru(SRaaiNR)2](ClO4)2 (3a/3b) in 2-methoxyethanol. The reaction in methanol, however, has synthesized [Ru(SRaaiNR)( S RaaiNR)Cl](ClO4) (4a/4b). The solid phase reaction of SRaaiNR and RuCl3 on silica gel surface upon microwave irradiation has synthesized [Ru(SRaaiNR)(SaaiNR)](PF6) (5a/5b) [SRaaiNR represents tridentate N,N′,S-chelator; S RaaiNR is N,N′-bidentate chelator where S does not coordinate and SaaiNR refers N,N′,S-chelator where S refers to thiolato binding]. The structural characterization of [Ru(SEtaaiNEt)( S EtaaiNEt)Cl](ClO4) (4b) and [Ru(SEtaaiNEt)(SaaiNEt)](PF6) (5b) has been confirmed by single crystal X-ray diffraction study. The IR, UV–Vis, and 1H NMR spectral data also support the stereochemistry of the complexes. The complexes show metal oxidation, Ru(III)/Ru(II), and ligand reductions (azo/azo−, azo−/azo ). The molecular orbital diagram has been drawn by density functional theory (DFT) calculation. Normal mode of analysis has been performed to correlate calculated and experimental frequencies of representative complexes. The electronic movement and assignment of electronic spectra have been carried out by TDDFT calculation both in gas and acetonitrile phase. [Copyright &y& Elsevier]

Abstract: [Ni(NaiR)2(X)2] (X=N3 (3, 4) and NCS (5, 6) complexes are synthesized from the reaction of Ni(ClO4)2 ·6H2O with 1-alkyl-2-(naphthyl-α/β-azo)imidazole (α/β-NaiR) and sodium azide (NaN3) or ammonium thiocyanate (NH4NCS) (1:2:2 molar ratio) in methanol solution. The complexes are characterized by elemental, spectroscopic and magnetic study. The distorted octahedral structure has been confirmed by single crystal X-ray diffraction study of [Ni(β-NaiEt)2(NCS)2] (6b). Cyclic voltammogram exhibits quasireversible oxidation response at 0.3–0.4V which is corresponding to Ni(III)/Ni(II) couple along with ligand reductions at negative potential to SCE reference electrode. [Copyright &y& Elsevier]

Abstract: trans-(Cl)-[Ru(CO)2Cl2(PaiR/TaiR)] compounds have been synthesized by reacting 1-alkyl-2-(phenylazo)imidazole (PaiR) or 1-alkyl-2-(p-tolylazo)imidazoles (TaiR) with [Ru(CO)2Cl2] n in methanol under refluxing conditions. The X-ray crystallographic study of trans-(Cl)-[Ru(CO)2Cl2(PaiEt)] (PaiEt=1-ethyl-2-(phenylazo)imidazole) shows a distorted octahedral geometry with a trans-Cl,Cl configuration. An intermolecular hydrogen bonded dimer serves as a motif in the supramolecular network with C–H⋯π and π⋯π interactions. The complexes show metal oxidation, Ru(III)/Ru(II); and reduction of the coordinated azo (–N) function. The molecular orbital diagram has been drawn by density functional theory (DFT) using an optimized geometry from the single crystal X-ray parameters. The electronic movement and assignment of electronic spectra have been carried out by TD-DFT calculations both in the gas and acetonitrile phase. [Copyright &y& Elsevier]

Abstract: Manganese(II)-naphthylazoimidazole complexes using and NCS− as counter ions are characterized as Mn(β-NaiR)2(X)2(β-NaiEt=1-alkyl-2-(naphthyl-β-azo)imidazole; , NCS−). The ligands are unsymmetric N(imidazole), N(azo) chelating agents. The microanalytical, spectral (FT-IR, UV–vis), magnetic (bulk moment and EPR) and electrochemical data establish the structure and composition of the complexes. The single crystal X-ray diffraction studies of Mn(β-NaiEt)2(N3)2 and Mn(β-NaiEt)2(NCS)2(β-NaiEt=1-ethyl-2-(naphthyl-β-azo)imidazole) have confirmed the three dimensional structure of the complexes. Cyclic voltammetry exhibits high potential Mn(III)/Mn(II) couple along with azo reductions. The EPR spectra show usual pattern. [Copyright &y& Elsevier]

Abstract: Palladium(II) complexes of N-[(2-pyridyl)methyliden]-α(or β)-aminonaphthalene (α or β-NaiPy) are reported in this work. They are spectroscopically characterized along with some mixed ligand complexes, using diimine and azoimine functions. The single crystal X-ray structure of [Pd(N-(2-pyridyl)methyliden-β-aminonaphthalene)Cl2] has been determined. Luminescence properties of the complexes exhibit a ligand centered π–π∗ emission. Quantum yields (ϕ) have been calculated and it has been observed that the complexes of α-NaiPy show higher ϕ values than the complexes of β-NaiPy. Lifetime measurements suggest bi-exponential decay and the average fluorescence lifetime varies from 1.4 to 6.8ns. The spectroscopic properties are correlated with DFT and TD-DFT calculations in two complexes, Pd(β-NaiPy)X2 (X=Cl, I) and they are compared with the free ligand results. [Copyright &y& Elsevier]

Abstract: The reaction of 8-aminoquinoline (8-aq) with M(NO3)2 and M(ClO4)2 (where M=Zn, Cd and Hg) has synthesized complexes of the composition [M(8-aq)2(H2O)2](X)2 (X=NO3, ClO4) whereas MCl2 has isolated M(8-aq)Cl2 type non-ionic compounds. The reaction of M(OAc)2, 8-aq and NaN3/NH4CNS in a 1:1:2mole ratio has separated polynuclear complexes of the composition [M(8-aq)(Y)2]n (Y=N3, NCS). The complexes have been characterized by spectroscopic data and have been structurally confirmed by single crystal X-ray diffraction study in some representative cases. The X-ray structure of [Zn(8-aq)2(H2O)2](NO3)2 shows C–H–π, and π–π interactions and forms a H-bonded sheet (with interactions between the oxygen of NO3 and C(9)–H of 8-aq/coordinated H2O). A novel one-dimensional cadmium(II) azido complex, [Cd(8-aq)(N3)2]n (9), in which the azido takes on an end-on (EO) bridging mode, has been synthesized and characterized. The presence of π–π interactions result in a supramolecular two-dimensional behaviour for the structure. The complexes are photoluminescent at room temperature. [Copyright &y& Elsevier]

Abstract: The reaction of 2-(3′-pyridylazo)imidazole (PyaiH) or 1-alkyl-2-(3′-pyridylazo)imidazole (PyaiR) with in THF or MeCN has synthesized stable red coloured (2a) or (2b–2d). While the reaction of PyaiR and in dry n-heptane has separated shining green compound and has been identified azo-anion radical, [Os(Cl)(CO)(PPh3)2(PyaiR− )] (4b–4d). The reaction performance in n-hexane or toluene is very poor. Upon addition of Cl2 in MeCN to CH2Cl2 solution of 2 or 4 the colour has changed sharply to red-violet and has isolated (3). The reaction of 2 in ethanol with NaBH4 suspension under dinitrogen has reduced coordinated imidazole group to imidazolidine (5). One of the structures of azo-imidazolidinate-hydrido-osmium–carbonyl, [Os(H)(CO)(PPh3)2(PyaiH2)] (5a), is characterized by X-ray diffraction study. Other spectroscopic studies (IR, UV–Vis, NMR) are used to identify the structure of all the complexes. Electrochemistry shows two consecutive anodic peaks (E pa) and suggest irreversible oxidations Os(III)/Os(II), Os(IV)/Os(III) along with azo reductions. [Copyright &y& Elsevier]

Abstract: 1-Alkyl-2-(naphthyl-α/β-azo)imidazole (α-NaiR 1; β-NaiR, 2) react with [Os(H)(Cl)(CO)(PPh3)3] in THF and synthesise [Os(H)(CO)(PPh3)2(α/β-NaiR)](PF6) (3, 4). The X-ray structure of [Os(H)(CO)(PPh3)2(α-NaiEt)](PF6) (3c) shows a distorted octahedral geometry. Other spectroscopic studies (IR, UV–Vis, NMR) support the stereochemistry of the complexes. Addition of Cl2 in MeCN to 3 or 4 gives [Os(Cl)(CO)(α/β-NaiR)(PPh3)2](PF6) (5, 6), which were characterized by spectroscopic studies. The redox properties of the complexes show Os(III)/Os(II), Os(IV)/Os(III) and azo reductions. [Copyright &y& Elsevier]

Abstract: Cadmium(II) complexes of N-[(2-pyridyl)methyliden]-α (or β)-aminonaphthalene (α or β-NaiPy) and 1-alkyl-2-(naphthyl-α (or β)-azo)imidazoles (α- or β-NaiR) using Cl−, and as anions are spectroscopically characterized. Molar conductance data in nitromethane show that the chloro and nitrite compounds are non-conducting, while the perchlorate complexes are 1:2 electrolytes. The single crystal X-ray structure of [Cd(N-{(2-pyridyl)methyliden}-β-aminonaphthalene)2(ONO2)2] has been determined. The luminescence properties of Cd(II) complexes of α/β-NaiPy are studied and they exhibit ligand centered π–π∗ emissions. Naphthylazoimidazoles and their cadmium complexes are non-fluorescent. [Copyright &y& Elsevier]

Abstract: The reaction of 1-alkyl-2-(naphthyl-(α/β)-azo)imidazoles [α-NaiR, (1) and β-NaiR (2) where R=Me (a), Et (b), CH2Ph (c)] with Co(OAc)2 ·4H2O and NaN3 in methanol solution has synthesised [Co(α/β-NaiR)2(N3)2] (3, 4). The complexes have been characterized by spectroscopic data and structurally confirmed by single crystal X-ray diffraction data in the case of [Co(β-NaiEt)2(N3)2] (4b). The structure is a severely distorted tetrahedron of CoN4 coordination in which β-NaiEt serves as a monodentate imidazole-N donor ligand. The distortion arises from two weak interactions from Co⋯N(azo) (N(azo) from β-NaiEt). Two weak transitions observed at >600nm are due to the structural distortion. Cyclic voltammetry shows a high potential Co(III)/Co(II) couple along with ligand reductions in the complexes. The tris-chelates, [Co(NaiR)3]2+, are also characterized. [Copyright &y& Elsevier]

Abstract: The reaction of 1-ethyl-2-(phenylazo)imidazole (PaiEt), NaN3 and Mn(OAc)2 ·4H2O at 1:2:1 molar ratio has isolated azido bridge 1-D coordination polymer. In monomeric unit of the complex, MnN6 distorted octahedral coordination is achieved by two EO–N3, two EE–N3 and N,N′-chelation of PaiEt. Bridge angle Mn–(EO)N3–Mn is 98.55(10)°. Variable temperature (300–2K) magnetic measurements determine J values −13.63±0.10 and 2.31±0.15cm−1 and support antiferromagnetic (EE–N3) and ferromagnetic (EO–N3) interaction, respectively. Maximum susceptibility (χ M =0.0251cm3 mol−1) is observed at 43K. [Copyright &y& Elsevier]

Abstract: PbI2 forms iodo-bridged neutral polymer upon reaction with 1-alkyl-2-(arylazo)imidazoles (RaaiR′). The reaction of PbI2 and dialkyl imidazolium iodides [RaaiR′R″]+I− has synthesized {1,3-dialkyl-2-(arylazo)imidazolium} m -{tri-iodoplumbate(II)} m . The complexes are characterized by different spectroscopic studies. Iodobridged chelated polymer, [Pb(RaaiR′)I2] n , has been established by single crystal X-ray diffraction measurements in one case. Tri-iodoplumbates form iodo bridged anion polymer, which connects [RaaiR′R″]+ by hydrogen bonding and are placed in between the pillars of [Pb(μ-I)6] n motif. [Copyright &y& Elsevier]

Abstract: The reaction of 2-(3′-pyridylazo)imidazole (3′-PyaiH) or its 1-alkyl derivative, 3′-PyaiR, with Ru(CO)3(PPh3)2 has synthesized air stable, moisture insensitive, diamagnetic Ru(0) complexes, [Ru(CO)(3′-PyaiR)(PPh3)2]. The ligands serve as an unsymmetric N,N′-chelating agent (N(imidazole) and N(azo) are abbreviated as N and N′, respectively). The X-ray structure determination of [Ru(CO)(3′-PyaiH)(PPh3)2] shows a square pyramidal geometry. The square plane is made up of Ru, 2P, C(O), N(1), and with N(3) at the apex. Other spectroscopic studies (IR, UV–Vis, NMR) support the stereochemistry. Electrochemistry shows three consecutive anodic peaks (E pa) and suggest irreversible redox responses of Ru(I)/Ru(0), Ru(II)/Ru(I), Ru(III)/Ru(II) and azo reductions. Oxidation by Cl2 of [Ru(CO)(3′-PyaiR)(PPh3)2] has isolated the Ru(II)-complex as the perchlorate salt, [Ru(CO)(Cl)(3′-PyaiR)(PPh3)2](ClO4). A solution of RuCl3 and 3′-PyaiR in ethanol has isolated two isomers of the composition Ru(3′-PyaiR)2Cl2. They have been characterized by spectral and electrochemical data. [Copyright &y& Elsevier]

Abstract: Two new series of Zn(II) complexes of α/β-naphthyl-(2-pyridylmethylene)amine and 1-alkyl-2-(naphthyl-α/β-azo)imidazoles with as a counter ion are described in this article. The single crystal X-ray structure of [Zn(β-naphthyl-(2-pyridylmethylene)amine)(N3)2]2 has revealed an end-on azido bridged dimer while [Zn(1-ethyl-2-(naphthyl-β-azo)imidazole)2(N3)2] is a monomer. The complexes are spectroscopically characterized. Examination of luminescence properties of the complexes suggests that the Schiff bases are emissive and the naphthylazo compounds are non-emissive. [Copyright &y& Elsevier]

Abstract: 2-(Arylazo)pyrimidine (p-R-C6H4–NC4H3N2, aapm, R=H (papm, 3a), Me (tapm, 3b), Cl (Clpapm, 3c)) are N,N′-chelating ligands. Platinum(II) complexes, Pt(aapm)Cl2 (4) have been synthesized by the reaction of K2PtCl4 and aapm in MeCN–water under refluxing condition. The reaction of Pt(aapm)Cl2 with ArNH2 in MeCN has synthesized C–N coupled product, Pt(aapm-N–Ar)Cl (5–10). The single crystal X-ray structure determination of one of the compounds has suggested the coupling of ArNH2 at ortho-C–H of the pendant aryl part of aapm in the chelated complex. The stereochemistry and the bonding are described by 1H NMR data. The solution electronic spectra of Pt(aapm-N–Ar)Cl exhibit multiple transition at Vis–NIR region (500–1250nm) which are absent in Pt(aapm)Cl2. Cyclic voltammograms show two quasireversible azo reductions of Pt(aapm)Cl2; Pt(aapm-N–Ar)Cl exhibit four successive redox couples, one of them (positive to SCE) is oxidative in nature and other (negative to SCE) are ligand reductions. [Copyright &y& Elsevier]

Abstract: Heteroleptic tris-chelates, [Ru(bpy)2(α/β-NaiR)](ClO4)2 (bpy=2,2′-bipyridine; α/β-NaiR=1-alkyl-2-(naphthyl-α-azo)imidazole, α-NaiR and 1-alkyl-2-(naphthyl-β-azo)imidazole, β-NaiR) have been synthesized either by reacting Ru(bpy)2Cl2 and α/β-NaiR in presence of 2 equivalent of AgNO3 or from Ru(bpy)2Cl2 +[Ag(α/β-NaiR)2](ClO4) reaction under refluxing condition in MeCN. The single crystal X-ray diffraction study in one case, and by other spectroscopic studies has supported the structure of the complexes. All the complexes show metal-to-ligand charge transfer (MLCT) transitions in the visible region. Cyclic voltammetric studies exhibit high potential Ru(III)/Ru(II) (1.2–1.3V vs. SCE) and three successive ligand reductions at negative to SCE in acetonitrile solution. [Copyright &y& Elsevier]

Abstract: Pyridine and imidazole are connected by an azo group (h name="dbnd" />Nhesize 2-[(3′-pyridyl)azo]imidazole (3′-PyaiH) and this has been confirmed by X-ray structure determination. The N(1)-alkylation gives 1-alkyl-2-[(3′-pyridyl)azo]imidazole (3′-PyaiR′) (R′=Me (2a), Et (2b), Bz (2c)). The reaction between Mn(ClO4)2 ·6H2O and 3′-PyaiR′ in methanol has synthesized [Mn(3′-PyaiR′)4](ClO4)2 (3). The structure has been confirmed by single crystal X-ray diffraction study in one case, in addition to other spectral characterization. The structure reveals a tetrahedral orientation of four ligands coordinating through imidazole-N only. Cyclic voltammetry exhibits a Mn(III)/Mn(II) couple at >1.1V along with azo reductions. However, the reaction of MnCl2 ·4H2O+3′-PyaiR′ in the presence of NaN3 or NH4CNS (1:2:2 mole proportion) has synthesized Mn(3′-PyaiR′)2(X)2 (X=N3 (4), NCS (5)). [Copyright &y& Elsevier]

Abstract: Mercury(II) acetate reacts with the 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R=H (a), Me (b); R′=Me (1/3/5), Et (2/4/6)] and sodium azide in methanol solution to afford azido bridged polymeric complexes [Hg(RaaiR′)(N3)2]n (3/4). On setting up similar reaction condition, the reaction of Hg(OAc)2 with RaaiR′ and NH4SCN has yielded, instead of polymer, an ion-pair [Hg(RaaiR′)4][Hg(SCN)4] (5/6). The complexes are characterised by elemental analysis, IR, UV–Vis, 1H NMR spectral data and single-crystal X-ray structures of [Hg(HaaiEt)(μ-1,1-N3)2]n (4a) and [Hg(HaaiEt)4][Hg(SCN)4] (6a). The complex 4a is a coordination polymer with end-on (μ-1,1) azido bridge and 6a has tetrahedral structure. [Copyright &y& Elsevier]

Imidazolyl and 3′-pyridyl are linked by azo bond (–N&z.dbnd6;N–) to synthesize hitherto unknown mixed heterocyclic azo molecules, 2-[(3′-pyridyl)azo]imidazole (3′-PyaiH). Alkylation in presence of NaH has synthesized 1-alkyl-2-[(3′-pyridyl)azo]imidazole (3′-PyaiR′). 3′-PyaiR′ include three types of N-donor centers: N(imidazole), N(azo) and a peripheral N(pyridine). They bind to Ag+ to form 2:2 metallo-macrocycle, [Ag(3′-PyaiR′)]22+, while the reaction with Cd2+ forms Cd(3′-PyaiR′)42+. The complexes are structurally characterized by X-ray diffraction studies. [Copyright &y& Elsevier]

Tris-chelated [Ru(o/p-RaaiR′)3]Cl2 (where RaaiR′=1-alkyl-(2-arylazo)imidazole, R= H (5), p-Me (6) p-OMe (7) o-OMe (8), R′=Me (a), Et (b), CH2Ph (c)) were prepared by the microwave technique. Complexes have been characterized by IR, UV–Vis and 1H NMR spectral data. The structural confirmation has been done in one case, [Ru(o-OMeaaiCH2Ph)3]Cl2. The UV–Vis spectra of the complexes show an intense peak in the visible region (510–570 nm) and it has been assigned to a MLCT transition. Cyclic voltammetry of the complexes shows one metal oxidation Ru(II)/Ru(III) at 1.2–1.5 V and three successive ligand reduction couples negative to SCE as the reference electrode. [Copyright &y& Elsevier]

Cadmium(II) complexes of 1-alkyl-2-(arylazo)imidazoles [RaaiR′ (where R=H (a), Me (b); R′=Me (1/3/5/7), Et (2/4/6/8)] are described in this work. Three representative complexes of the series, [Cd(HaaiMe)2Cl2] (3a), [Cd(HaaiEt)4](ClO4)2 (6a) and [Cd(HaaiMe)4](NO3)2 · 2H2O (7a), have been characterized by single crystal X-ray diffraction measurements. In these complexes, cadmium is seated at the center of a tetrahedron. In [Cd(HaaiMe)2Cl2] (3a), the neutral metallo-organic compound consists of a central cadmium atom surrounded by two HaaiMe ligands and two chlorides. In [Cd(HaaiEt)4] (ClO4)2 (6a), the cation consists of a central cadmium atom surrounded by four HaaiEt ligands. [Cd(HaaiMe)4] (NO3)2 · 2H2O (7a) is a tetragonal channel structure. Nitrate and interstitial water molecules assemble into a square-grid supramolecule (ca. 7 × 7 A˚) and each grid is interlocked by chains parallel to the Z-axis passing through the middle of the square arms to form a layer in the ac- (or bc-) plane with a brick-wall topology (dimension 11.2 × 7 A˚). [Copyright &y& Elsevier]

Dichloro zinc(II) complexes of 1-alkyl-2-(arylazo)imidazole, Zn(RaaiR′)Cl2·H2O (RaaiR′=p-R&z.sbnd;C6H4&z.sbnd;N=N&z.sbnd;C3H2N&z.sbnd;N(1)&z.sbnd;R′: R=H, Me, Cl and R′=Me, CH2CH3, CH2Ph) are characterized by elemental analysis, IR, UV–Vis and 1H NMR spectral data. The reaction of ZnCl2 and RaaiR′ (excess) in the presence of NH4CNS has synthesized Zn(RaaiR′)2(NCS)2. The single-crystal X-ray structure of dichloro-{1-methyl-2-(p-tolylazo)imidazole}zinc(II)-monohydrate (Zn(MeaaiMe)Cl2·H2O) suggests that the complex is distorted trigonal bipyramidal (TBP) around Zn(II) with a trigonal plane constituted from Cl(1), Cl(2), N(imidazole) (N(1)). Molecular packing shows a 1D chain via a hydrogen bonded eight membered ring. The X-ray structure of di-thiocyanato-bis-{1-methyl-2-(phenylazo)-imidazole}zinc(II) also shows a distorted TBP around Zn(II). The coordination sphere is ZnN3 type: where one of the ligands acts as a bidentate chelating agent and the second one coordinates via only the imidazole-N along with two N-centers from the NCS group. [Copyright &y& Elsevier]

The hetero-tris-chelates of the formulae [Ru(phen)(RaaiR′)2](ClO4)2 [phen=1,10-phenanthroline, RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R&z.sbnd;C6H4&z.sbnd;N&z.dbnd6;N&z.sbnd;C3H2&z.sbnd;NN-1-R′, where R=H (a), Me (b), Cl (c) and R′=Me (2), Et (3), CH2Ph (4)] have been isolated from the reaction of ctc-[RuCl2(RaaiR′)2] with AgNO3+phen or [Ag(phen)2](ClO4) in acetone at 40 °C in the dark followed by the addition of NaClO4(aq). The structure of [Ru(phen)(HaaiMe)2](ClO4)2 has been confirmed by X-ray diffraction study and suggested stereoretentive nucleophilic substitution. The structure and stereochemistry of the complexes have been supported by 1H NMR data. Electronic spectra exhibit a strong metal-to-ligand charge transfer (MLCT) band at 515–530 nm along with a weak transition at 700–710 nm. Cyclic voltammograms show a Ru(III)/Ru(II) couple at 1.3–1.4 V versus saturated calomel electrode (SCE) along with three successive ligand reductions. The plot of the difference in potential of the first oxidation and reduction versus energy of the main MLCT band (ν¯CT) is linear. [Copyright &y& Elsevier]