Synthesis and spectroscopic characterization of new heteroleptic ruthenium(II) complexes incorporating 2-(2′-pyridyl)quinoxaline and 4-carboxy-2-(2′-pyridyl)quinoline

Starting from cis-[Ru(dcbpyH₂)₂Cl₂] (1), two new heteroleptic ruthenium(II) complexes, [Ru(dcbpyH₂)₂(L¹)](NO₃)₂ (L^1?=?2-(2′-pyridyl)quinoxaline (2), and [Ru(dcbpyH₂)₂(L²)](NO₃)₂ (L^2?=?4-carboxy-2-(2′-pyridyl)quinoline (4); dcbpyH_2?=?2,2′-bipyridine-4,4′-dicarboxylic acid), were synthesized and spectroscopically characterized. During the preparation of 2 and 4, the homoleptic [Ru(dcbpyH₂)₃]Cl₂ complex (3) was isolated as a side product. Characterization includes IR and Raman spectroscopy, UV-Vis, multinuclear NMR spectroscopy, elemental, and ESI-mass spectrometric analyses.     

Crystal Structure of Bis(3-hydroxy-2-pyridyl)disulfide

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Ruthenium(II) complexes of 2-(2′-pyridyl)naphthoimidazole: synthesis,characterization and DNA-binding studies

The perchlorate salts of two new ruthenium(II) complexes incorporating 2-(2′-pyridyl)naphthoimidazole are synthesized in good yield. Complexes [Ru(phen)₂(PYNI)]²⁺ (phen = 1,10-phenanthroline) 1 and [Ru(dmp)₂(PYNI)]²⁺ (dmp = 2,9-dimethyl-1,10-phenanthroline, PYNI = 2-(2′-pyridyl)naphthoimidazole) 2 are fully characterized by elemental analysis, FAB-MS, ES-MS, ¹H NMR and cyclic voltammetric methods. The DNA-binding behavior of the complexes have been studied by spectroscopic titration, viscosity measurements and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf-thymus DNA (CT-DNA), with their binding constants spanning the range (2.73–5.35) × 10⁴ M^?1. The experimental results show that 1 interacts with calf thymus DNA (CT-DNA) by intercalative mode, while 2 binds to CT-DNA by partial intercalation.     

Complexes of palladium,platinum and rhodium with 2,2′-biquinoline and 2-(2′-pyridyl)quinoline

Summary The reactions of 2,2-biquinoline(biq) with M(PhCN)₂X₂ (M=Pd; X=Cl or Br; M=Pt, X=Cl, Br or I), K₂PtCl₄ and RhCl₃·3H₂O and of 2-(2-pyridyl)quinoline (pq) with K₂PtCl₄ and RhCl₃·3H₂O have been investigated. The isolated complexescis-[Pd(biq)X₂] (X=Cl or Br),cis-[Pt(biq)Cl₂],cis-[Pt(biq)Cl₂]·H₂O,trans-[Pt(biq)₂Br₂]·5H₂O, [Pt₃(biq)₂I₆],mer-[Rh(biq)Cl₃-(H₂O)] andmer-[Rh(pq)Cl₃(H₂O)] have been characterized by elemental analyses, conductivity measurements, i.r., electronic, and¹H n.m.r. spectra. The reaction of pq with K₂PtCl₄ in 1M H₂SO₄ gave the salt 2-(2-pyridyl) quinolinium tetrachloroplatinate(II) pentahydrate, (pqH)₂[PtCl₄]·5H₂O; when the reaction was carried out in aqueous acetone,cis-[Pt(pq)Cl₂] was obtained. A new method for the synthesis ofcis-[Rh(biq)₂X₂]X (X=Cl or Br) is described; both compounds have been further characterized by¹H n.m.r.     

Conformations,vibrational spectra and force field of 1-methyl-2-(2′-pyridyl)benzimidazole: experimental data and density functional theory investigation in comparison with 2-(2′-pyridyl)benzimidazole

The molecular structure, conformational equilibria, vibrational spectra and molecular force field of 1-methyl-2-(2′-pyridyl)benzimidazole have been determined at the HF, MP2 and DFT/(B3LYP, BVP86) levels with 6-31+G(d,p) and TZVP basis sets. The torsional potentials for the rotation around the C1–C2 pivotal bond have been calculated at the B3LYP/6-31+G(d,p) and BVP86/TZVP levels of theory for gaseous and aqueous 1-methyl-2-(2′-pyridyl)benzimidazole. FT-Raman (3500–10 cm^?1) and FT-IR (3900–400 cm^?1) spectra of solid 1-methyl-2-(2′-pyridyl)benzimidazole have been recorded and interpreted on a base of calculated potential energy distribution. The results of the experimental and theoretical study of vibrational spectra and molecular structure of 1-methyl 2-(2′-pyridyl)benzimidazole are considered in comparison with similar data for 2-(2′-pyridyl)benzimidazole.

     

Synthesis and Crystal Structure of a New Hexadentate Ligand N,N''''-Bis(di(2-pyridyl)methyl)ethylenediamine

1 INTRODUCTION The interest in the development of new poly- pyridine ligands derives from several respects. The formation of a stable complex that can be used as a model for the active sites presents in some metallo- proteins. The uncoordinated donor at…     

Preparation,Characterization and Properties of Two New Lanthanide(Ⅲ)-5-(2-pyridyl)tetrazolate Complexes

Two new mononuclear lanthanide(Ⅲ) complexes Ln(pytz)3(H2O)3·(H2O)3.5[Ln=Tb(1);Eu(2);Hpytz=5-(2-pyridyl)tetrazole] were synthesized by reacting Hpytz with the corresponding lanthanide(Ⅲ) ions and characterized.The single crystal X-ray diffraction analysis reveals that complexes 1 and 2 are isostructural and the lanthanide(Ⅲ) ions in both complexes 1 and 2 are nine-coordinated,with three oxygen atoms of three coordination water molecules and six nitrogen atoms of three pytz ligands,forming a monocapped square antiprism.Extensive hydrogen bonds exist,resulting in a three-dimensional supramolecular network structure by hydrogen-bonds in both complexes 1 and 2,respectively.Complex 1 exhibits typical green fluorescence of Tb(Ⅲ) ion and complex 2 red fluorescence of Eu(Ⅲ) ion,in solid state at room temperature.     

The chemical behaviour of di(2-pyridyl)sulphide,dps. Crystal and molecular structure of μ-di(2-pyridyl)sulphidebis(trans-dichlorotriethylphosphine platinum(II)), [{Pt(PEt3)Cl2}2μ-dps] and its reactivity towards stannylated species

The coordinating ability of the ligand di(2-pyridyl)sulphide, dps, was studied in several situations. Dps behaved as a bidentate chelating agent with SnX4 (X=Cl or Br) and also with Pd and Pt (PdCl2 and K2PtCl4), whereas with [Pt2(PR3)2Cl4], (R = Et or Ph), it formed bridging complexes: [{Pt(PR3)Cl2}2-dps]. The crystal and molecular structure of [{Pt(PEt3)Cl2}2-dps] was determined. This complex, as well as [M(dps)Cl2], (M = Pd or Pt), underwent reactions with SnCl2, which inserts into the M–Cl bonds producing heterobimetallic products, which are important in catalysis.     

Quantum-chemical modeling of the effect of microhydration and media on the vibrational spectra of 2-(2′-pyridyl)-benzimidazole and its 1-methylsubstituted analogue

Quantum-chemical calculations of the optimized structures, harmonic force fields, and frequencies of 1 : 1 and 1 : 2 complexes of 2-(2′-pyridyl)-benzimidazole and 1-methyl-2-pyridine-2-yl-1H-benzimidazole are performed by means of DFT (B3LYP/6-31+G**). The shifts in the frequencies of the vibrational spectra of the investigated complexes are considered with allowance for the conformational structure and effect of the medium. Analytical bands (spectral marks) are proposed that can be used to identify complexes of 2-(2′-pyridyl)-benzimidazole and 1-methyl-2-pyridine-2-yl-1H-benzimidazole with water. It is concluded that considering the environment within a model of a polarized continuum allows the forecasting of possible shifts in the frequencies in the vibrational spectra of the studied compounds in aqueous media and DMF.     

Synthesis,Crystal Structure and Photoluminescent Property of a New Zn(Ⅱ) Complex Based on 3,4-Bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole

The coordination polymer[Zn_(1.5)(2,2?,4??-tpt)(tpa)_2]_n(2,2?,4??-tpt=3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole,H_2tpa=terephthalic acid)has been obtained by solution evaporation method and characterized by elemental analysis,IR,TG and single-crystal X-ray diffraction.The title compound crystallizes in the triclinic system,space group P1,with a=10.331(3),b=10.596(1),c=14.966(3)?,β=99.029(0)o,V=1448.86(6)?~3,Z=2,D_c=1.668g/cm~3,μ=1.320 mm~(-1),F(000)=740,R=0.0359 and w R=0.0841 with I2σ(I)).In this polymer,the asymmetric unit contains two crystallographically independent Zn(II)ions in different coordination environments.Zn(1)ion is five-coordinated,forming a distorted tetragonal pyramidal geometry,while the Zn(2)ion is six-coordinated to get a distorted octahedral geometry.Each Zn(II)ion is linked by 2,2?,4??-tpt and H_2tpa ligands,forming an infinite 2D structure.The existence of O(8)–H(8)···O(2)hydrogen bonding interactions leads the 2D chains to generate a 3D structure.In addition,1 shows strong photoluminescent emissions in the solid state at room temperature,so it can be used as potential optical materials.     

Dimeric and polymeric copper(I) complexes. Synthesis and characterization of copper(I) complexes of di-2-pyridyl ketone oxime (DPKox) and crystal structures of [Cu(DPKox)Cl]2·2H2O and [Cu(DPKox)(NCS)]n

Copper(I) complexes with di-2-pyridylketone oxime (DPKox) of the type CuLX·nH₂O, n=1 for X=Cl and Br, and n=0 for X=I and SCN, have been synthesized and characterized. The overall physical results suggest tridentate and bidentate DPKox ligand in the Cl, Br and I, SCN complexes, respectively, and terminal X in the former but bridging X in the later. These complexes display MLCT bands in the visible region, but they do not fluoresce at room temperature. The structure determination has shown the chloride complex (1) to have a centro-symmetrically related dimeric unit, in which each copper atom is coordinated by Cl(1), N(1), N(2) and N(3) (of the second ligand molecule) in a distorted tetrahedral environment. Hydrogen bonds are formed by the O(1) of the oxime group and a lattice water molecule, and between different lattice water molecules and Cl(1). The structure of the thiocyanate complex (2) features tetrahedral geometry around copper atoms, a chelating bidentate DPKox ligand coordinating via one of the two pyridyl nitrogens, N(1), and N(oxime) only and μ-1,3-thiocyanate group forming zigzag chains along the c-axis of the unit cell.     

Ruthenium,osmium and rhodium-2,3-bis(2′-pyridyl)quinoxaline complexes

Ru₃(CO)₁₂ reacts with 2,3-bis (2-pyridyl)quinoxaline (dpq) in benzene in the presence of either 2,2(dipyridine (dpy) or pyridine (py) to give the mononuclear complexes Ru(CO)₃(dpq) (1) and Ru(CO)₂(dpq)(py) (2), respectively. On the other hand, reactions of Os₃(CO)₁₂ with dpq alone, or in the presence of dipyridine, yield only Os(CO)₃(dpq) (3). Spectroscopic studies of the three complexes were consistent with the proposed structures. Reactions of RuCl₃ with dpq, under reduced pressure in PhH/EtOH gave bis-[Ru(dpq)₂Cl₂]Cl (4). Magnetic measurements showed Ru^III, d⁵, to be in a low-spin electronic configuration. Three complexes, Rh₂(dpq)₂Cl₆ (5), [Rh(dpq)₂Cl₂]Cl (6) and Rh(dpq)(py)Cl₃ (7), were isolated from reactions of RhCl₃ with dpq. The type of product was dependent on the reactants and conditions. The complexes exhibit either irreversible or quasi-reversible ligand-based reductions. In addition, the zerovalent complexes (1)–(3) displayed one metal(based oxidation in their cyclic voltammograms, due to the formation of M⁺ species.     

Syntheses,structures, and properties of transition metal complexes with 2-( n -pyridyl)benzimidazole ( n = 2, 3, and 4)

Three pyridylbenzimidazoles (2-PBIM, 3-PBIM, and 4-PBIM) have been prepared (2-PBIM: 2-(2-pyridyl)-benzimidazole, 3-PBIM: 2-(3-pyridyl)-benzimidazole, 4-PBIM: 2-(4-pyridyl)-benzimidazole). Reactions of several transition metals (Cd²⁺, Cu²⁺, Fe²⁺) with the three ligands gave four new coordination complexes, [(Cd)₂(2-PBIM)₂(CH₃COO)₄] (1), [Cu(3-PBIM)₂(CH₃COO)₂]?·?2H₂O (2), [Cu(4-PBIM)₂(CH₃COO)₂(H₂O)]?·?H₂O (3), and [Fe(4-PBIM)₂(Cl)₂(H₂O)₂] (4), respectively. These four complexes have been characterized by X-ray crystallography, IR spectroscopy, and UV absorption spectroscopy. Thermogravimetric properties of 2 and 4 were also measured. X-ray crystallographic studies reveal that these four complexes are very different, although the ligands are similar in structure. The role of hydrogen-bonding and π–π interactions in extending dimensionality of simple complexes has been discussed.     

2-Oxooxazolopyridines. 2. Synthesis of N′-alkyl-N-(2-oxo-3-pyridyl)ureas

In reactions with amines 2-oxo-7-trifluoromethyl-5-phenyl-(1H)-oxazolo[5,4-b]pyridines and alkyl N-(2-oxo-3-pyridyl)carbamates are converted into N-alkyl- and N,N-dialkyl-N-(2-oxo-3-pyridyl)ureas respectively.For Communication 1, see [1].Riga Technical University, Riga LV-1048, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 385–391, March, 1998.     

Synthesis,spectral and RAHB studies on some arylhydrazones of β-diketones: crystal and molecular structures of 2-(2-(3-pyridyl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione and 2-(2-(2-methoxyphenyl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione

The present study describes the synthesis and spectral analysis of a series of arylhydrazones of β-diketones (1–6) along with the single crystal X-ray structural studies of 2-(2-(3-pyridyl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (3) and 2-(2-(2-methoxyphenyl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (6). Spectral and structural studies clearly exemplify the effective intramolecular hydrogen bonding and as a result the NH proton signals and carbonyl carbon signals are shifted to higher frequency region in NMR spectra. Structural implications imposed by the formation of pseudo six-membered ring after hydrogen bonding is well observed in XRD analysis. XRD analysis also evidences the envelop conformation of the dimedone ring in both the cases and resonance assisted hydrogen bonding (RAHB) studies were also performed.     

The reaction of β-lactam carbenes with 3,6-dipyridyltetrazines: switch of reaction pathways by 2-pyridyl and 4-pyridyl substituents of tetrazines

The reactions of β-lactam carbenes with both 3,6-di(2-pyridyl)tetrazine and 3,6-di(4-pyridyl)tetrazine were studied. It was found that β-lactam carbenes reacted with 3,6-di(2-pyridyl)tetrazine to produce 5-triazolo[1,5-a]pyridylpyrrol-2-ones in good yields, while with 3,6-di(4-pyridyl)tetrazine, they afforded pyrido[c]cyclopenta[b]pyrrol-2-ones in moderate yields. Both reactions were proposed to follow cascade mechanisms containing a 3,6a-dipyridylpyrrolo[3,2-c]pyrazol-5-one intermediate. The different pathways of the transformation of pyrrolo[3,2-c]pyrazol-5-ones were switched by the 2- and 4-pyridyl substituents. This work not only provided a simple and efficient strategy for the construction of novel triazolo[1,5-a]pyridine and pyrido[c]cyclopenta[b]pyrrole derivatives, respectively, but also revealed two different thermal transformation patterns of 3H-pyrazole compounds.     

Structures and bonding situation of Pb2X2 (X?=?H, F, Cl, Br and I)

Quantum chemical calculations using DFT (BP86) and ab initio methods (MP2, MP4 and CCSD(T)) have been carried out for the title compounds. The nature of the Pb?CPb interactions has been investigated with an energy decomposition analysis. The energy minimum structures of the halogen substituted Pb₂X₂ molecules possess a doubly bridged butterfly geometry A like the parent system Pb₂H₂. The unusual geometry can be explained with the interactions between PbX fragments in the X ²?? ground state which leads to one Pb?CPb electron-sharing ?? bond and two donor?Cacceptor bonds between the Pb?CX bonds as donor and vacant p(??) AOs of Pb. The energy difference between the equilibrium form A and the linear structure XPb??PbX (E) which is a second-order saddle point is much higher when X is a halogen atom than for X?=?H. This is because the a ⁴??^?????X ²?? excitation energies of PbX (X?=?F?CI) are higher than for PbH. The structural isomers B, D1, D2, E, F1, F2 and G of Pb₂X₂ are no minima on the potential energy surface.     

Coordination compounds of europium(III) and samarium(III) dibenzoylmethanates with 5-phenyl-2-(2′-pyridyl)-7,8-benzo-6,5-dihydro-1,3,6-triazaindolizine

Novel heteroligand europium(III) and samarium(III) complexes with dibenzoylmethane (HDBM) and 5-phenyl-2-(2??-pyridyl)-7,8-benzo-6,5-dihydro-1,3,6-triazaindolizine (L), Ln(DBM)₃L (Ln = Eu, Sm), were synthesized. The structure of the europium complex was determined by X-ray diffraction. It was shown that the use of L as an auxiliary ligand increases the luminescence intensity of lanthanides severalfold as compared with analogous complexes containing phenanthroline as the second ligand.     

Preparation and reaction of platinum(II) complexes of N,N-bis(dicyclohexylphosphinomethyl)aminomethane. Crystal structures of (Cy2PCH2)2NMe (Cy = cyclohexyl) and [PtX2{(Cy2PCH2)2NMe}], (X = Cl and I)

Treatment of [Cy₂P(CH₂OH)₂]Cl with MeNH₂ in the presence of Et₃N affords a high yield of the phosphine (Cy₂PCH₂)₂NMe (1) (dcpam) which has been characterised by a single crystal X-ray structure. Treatment of [PtX₂(COD)], (COD=cyclo-octa-1,5-diene, X= Cl or I) with (1) affords the platinum complexes [PtX₂{(Cy₂PCH₂)₂NMe}] (2). The chloride complex, (2a), reacts with t-BuNC to afford [PtCl(t-BuNC)-{(Cy₂PCH₂)₂NMe}]Cl (3) and treatment of (2a) with 2-mercapto-1-methylimidazole affords [Pt{SCN(Me)CHCH=N(Me)}{Cy₂PCH₂)₂NMe}]Cl (5). The reaction of (2a) with 2-acetamidoacrylic acid in the presence of silver(I) oxide affords the carbon bonded isomer (8a) only whereas a similar reaction using [PtCl₂{Ph₂P-(CH₂)₃PPh₂}] affords a mixture of the azaallyl complex (7) and the carbon bonded isomer (8b) which can be separated by fractional crystallisation. The crystal structures of PtX₂{(Cy₂PCH₂)₂NMe}] are also reported.