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Reaction of Ni(ClO4)2 · 6H2O with 1-alkyl-2-(arylazo)imidazole (RaaiR/) and sodium azide (NaN3) or ammonium thiocyanate (NH4SCN) (1 : 2 : 2 molar ratio) in methanol gives [Ni(RaaiR/)2(X)2] (X=N3 (3, 4) and SCN (5, 6). All these complexes are characterized by elemental analyses, UV-Vis and IR spectral data, thermal and magnetic moment measurements. The X-ray structure is confirmed by single crystal measurement of [Ni(Pai-Me)2(N3)2] (3a). Cyclic voltammetry exhibits quasireversible response at >0.80 V corresponding to Ni(III)/Ni(II) couple along with ligand reductions at negative potential (<-0.5 V) to SCE reference. The electronic structure, spectral and redox properties are explained by DFT (Gaussian03) calculation. [ABSTRACT FROM AUTHOR]

The reaction of [Ru(OH2)2 (RaaiR')]2+ [RaaiR' = 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N = N-C3H2-NN(1)-R', R = H (1), Me (2), Cl (3); R' = Me (a), Et (b), CH2Ph (c)] with 8-quinolinol (HQ) in acetone solution followed by the addition of NH4PF6 afforded violet, mixed ligand complexes of composition [Ru(Q)(RaaiR')2](PF6). The structure of [Ru(Q)(MeaaiMe)2](PF6) (2a) has been confirmed by X-ray diffraction studies.Solution electronic spectra exhibit a strong MLCT band at 560-580 nm in MeCN. Cyclic voltammogrames show a Ru(III)/Ru(II)couple at 1.0-1.1 V versus SCE along with three successive ligand reductions. The electronic properties are correlated with EHMO results. [ABSTRACT FROM AUTHOR]

1-Alkyl-2-(naphthyl-(α/β)-azo)imidazoles (α/β-NaiR; R = Me, Et and CH 2 Ph) react with (NH 4 ) 2 [OsCl 6 ] and complexes OsCl 2 (NaiR) 2 are isolated in two isomeric forms: blue-violet ( 3 , 4 ) and red-violet ( 5 , 6 ). The ligand is a bidentate N (N(imidazole)), N′ (N(azo)) donor type. With reference to the pairs of Cl, Cl; N, N and N′, N′ atoms the blue-violet and red-violet isomers are assigned to cis - trans - cis ( ctc ) and cis - cis - cis ( ccc ) configurations respectively. IR spectra of the complexes show two v (Os-Cl) bands and support the cis -OsCl 2 configuration. 1 H NMR spectra also support the ctc and ccc -configuration. The structure of the blue-violet complex OsCl 2 (α-NaiEt) 2 has been determined by X-ray crystallography and the ctc configuration has been confirmed. The structure shows an unusually long N=N bond length, 1.331(4) Å, which is elongated by 0.07 Å compared to the free ligand value. [ABSTRACT FROM AUTHOR]

1-Alkyl-2-(arylazo)imidazoles ( p -R-C 6 H 4 -N=N-C 3 H 2 N 2 X, abbreviated as RaaiX, R = H( a ), CH 3 ( b ), Cl( c ); X = N(1)-CH 3 ( 1 ), N(1)-CH 2 -C 6 H 5 ( 2 )) have been reacted with (NH 4 ) 2 [OsCl 6 ] and OsCl 2 (RaaiX) 2 species isolated in two isomeric forms, blue-violet ( 3 , 5 ) and red-violet ( 4 , 6 ). IR spectra show two ν(Os-Cl) modes and support a cis -OsCl 2 configuration. X-ray diffraction methods were used to determine structures of blue-violet isomers. In terms of the three coordination pairs around Os(II), Cl, Cl, N, N (N(imidazole), N) and N′, N′ (N(azo), N′) the blue-violet isomers have a cis-trans-cis ( ctc ) configuration. 1 H NMR data for the red-violet complexes (isomers B) and results concerning analogous ruthenium(II) complexes indicate isomer B to have cis-cis-cis ( ccc ) configuration. Absorption spectra show an intense MLCT band at ca 580 nm along with two weak bands at 800 and 1000 nm. Cyclic voltammetry shows quasi -reversible Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6 V and 1.3-1.5 V versus SCE and ill-defined azo reductions. The X-Ray structures show unusually long N=N bond lengths, 1.31-1.32 Â, elongated by some 0.06 Â compared to the free ligand value. Os(II) prefers to bind N(azo) (Os-N(azo), 1.98 Â) rather than N(imidazole) (Os-N(imidazole), 2.03 Â). EHMO calculations of ctc -OsCl 2 (MeaaiMe) and comparison with the ruthenium(II) complex account for the MLCT transitions in terms of a metal-dominated HOMO to a ligand-dominated LUMO shift. [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

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]

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: 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 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-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: 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: 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: 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]

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]