Approaches to wired terpyridine: Bithienyl alkynyl derivatives of 2,2′:6′,2″-terpyridine and their ruthenium(II) complexes

Two approaches to the formation of ruthenium(II) complexes containing ligands with conjugated 2,2′:6′,2″-terpyridine (tpy), alkynyl and bithienyl units have been investigated. Bromination of 4′-(2,2′-bithien-5′-yl)-2,2′:6′,2″-terpyridine leads to 4′-(5-bromo-2,2’-bithien-5′-yl)-2,2′:6′,2″-terpyridine (1), the single crystal structure of which has been determined. The complexes [Ru(1)₂][PF₆]₂ and [Ru(tpy)(1)][PF₆]₂ have been prepared and characterized. Sonogashira coupling of the bromo-substituent with (TIPS)CCH did not prove to be an efficient method of preparing the corresponding complexes with pendant alkynyl units. The reaction of 4′-ethynyl-2,2′:6’,2″-terpyridine with 5-bromo-2,2′-bithiophene under Sonogashira conditions yielded ligand 2, and the heteroleptic ruthenium(II) complex [Ru(2)(tpy)][PF₆]₂ has been prepared and characterized.     

High-performance liquid chromatographic separation of enantiomers of 1,1′-binaphthyl-substituted α-aminoisobutyric acid

The direct and indirect stereochemical resolution of the enantiomers of free and N-protected (R,S)-2′,1′:1,2;1″,2″:3,4-dinaphthcyclohepta-1,3-diene-6-amino-6-carboxylic acid (Bin) was achieved by high-performance liquid chromatographic methods. The direct separation was carried out on a β-cyclodextrin-based chiral stationary phase, ChiraDex, and the indirect resolution by applying pre-column derivatization with 2,3,4,6-tetra-O-acetyl-β-

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-glucopyranosyl isothiocyanate.     

5′,8-Cyclopurine-2′-deoxynucleosides: Molecular structure and charge distribution – DFT study in gaseous and aqueous phase

Oxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts, it has been decided to present the structural propriety and charge distribution of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The 2-deoxyribose moiety of cyclopurines has adopted the ₀T¹ conformation in their cationic, neutral and anionic forms. The natural population analysis (NPA) of charge distribution between purine/2-deoxyribose moieties exhibited positive/positive value for cations, positive/negative for neutral molecules. NPA data for anionic forms showed negative/negative values in gas (exclude (5′S)cdG) and positive/negative in water. The dipole moments of 5′,8-cyclopurine-2′-deoxynucleosides were found as follows: 7.83(5′R)cdG, 6.86(5′S)cdG, 3.99(5′R)cdA, 1.99(5′S)cdA in the gaseous phase, 11.29(5′R)cdG, 9.99(5′S)cdG, 6.44(5′R)cdA, 4.14(5′S)cdA in the aqueous phase.     

Theoretical studies on the structural and optical properties of a series of Os(II) diimine complexes [Os(NN)(CO)2I2] (NN = 2,2′-bipyridine(bpy), 4,4′-di-tert-butyl-2,2′-bipyridine(dbubpy), 4,4′-dichlorine-2,2′-bipyridine(dclbpy))

The ground- and excited-state structures for a series of Os(II) diimine complexes [Os(NN)(CO)₂I₂] (NN = 2,2′-bipyridine (bpy) (1), 4,4′-di-tert-butyl-2,2′-bipyridine (dbubpy) (2), and 4,4′-dichlorine-2,2′-bipyridine (dclbpy) (3)) were optimized by the MP2 and CIS methods, respectively. The spectroscopic properties in dichloromethane solution were predicted at the time-dependent density functional theory (TD-DFT, B3LYP) level associated with the PCM solvent effect model. It was shown that the lowest-energy absorptions at 488, 469 and 539 nm for 1–3, respectively, were attributed to the admixture of the [d_xy (Os) → π^*(bpy)] (metal-to-ligand charge transfer, MLCT) and [p(I) → π^*(bpy)] (interligand charge transfer, LLCT) transitions; their lowest-energy phosphorescent emissions at 610, 537 and 687 nm also have the ³MLCT/³LLCT transition characters. These results agree well with the experimental reports. The present investigation revealed that the variation of the substituents from H → t-Bu → Cl on the bipyridine ligand changes the emission energies by altering the energy level of HOMO and LUMO but does not change the transition natures.     

Flip‐type disorder in 3‐substituted 2,2′:5′,2′′‐terthiophenes

In the crystal structures of four thiophene derivatives, (E)‐3′‐[2‐(anthracen‐9‐yl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₂₈H₁₈S₃, (E)‐3′‐[2‐(1‐pyrenyl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₃₀H₁₈S₃, (E)‐3′‐[2‐(3,4‐dimethoxyphenyl)ethenyl]‐2,2′:5′,2′′‐terthiophene, C₂₂H₁₈O₂S₃, and (E,E)‐1,4‐bis[2‐(2,2′:5′,2′′‐terthiophen‐3′‐yl)ethenyl]‐2,5‐dimethoxybenzene, C₃₆H₂₆O₂S₆, at least one of the terminal thiophene rings is disordered and the disorder is of the flip type. The terthiophene fragments are far from being coplanar, contrary to terthiophene itself. The central C—C=C—C fragments are almost planar but the bond lengths suggest slight delocalization within this fragment. The crystal packing is determined by van der Waals interactions and some weak, relatively short, C—H...S and C—H...π directional contacts.     

Fluorescence properties of (R)- and (S)-[1,1′-binaphthalene]-2,2′-diols solutions and their complexes with cyclodextrins in aqueous medium

Steady-state and time-resolved fluorescence techniques were used to study (R)- and (S)-[1,1′-binaphthalene]-2,2′-diol (1,1′-binaphthol or BINOL) dilute solutions of different polarity solvents, as well as their inclusion complexes with α- and βcyclodextrins (CDs) in water. BINOLs in dilute water solutions exhibited a surprisingly high fluorescence anisotropy that was explained as being due to the formation of fairly large order π–π stacking aggregates in aqueous polar media. Stoichiometries, formation constants and the changes of enthalpy and entropy upon inclusion were also obtained by measuring the variation of the fluorescence intensity with [CD] and temperature. Results agree with the formation of 1:1 stoichiometry complexes, but the association constants are rather low and very similar for both enantiomers. Molecular mechanic calculations in the presence of water were employed to study the formation of BINOL complexes with both α- and βCDs. For the most stable structures of any of the complexes only a small portion of the guests, in agreement with thermodynamics parameters and quenching experiments, penetrates inside the CD cavities. Driving forces for 1:1 inclusion processes may be dominated by non-bonded van der Waals host:guest interactions. The low guest:host binding constants and poor enantioselectivity of α- and βCDs for BINOLS may be a consequence of the BINOL aggregation in water.     

New approaches to synthesis of tris[1,2,4]triazolo[1,3,5]triazines

Thermal cyclization of 3-R-5-chloro-1,2,4-triazoles (R = Cl, Ph) afforded 2,6,10-tri-R- tris[1,2,4]triazolo[1,5-a:1′,5′c:1″,5″-e][1,3,5]triazines 5 (R = Ph) and 7 (R = Cl). These compounds are first representatives of this class of heterocycles, whose structures were unambiguously established. Treatment of these compounds with nucleophiles (H₂O/NaOH, NH₃) results in the triazine ring opening to give compounds consisting of three 1,2,4-triazole rings linked in a chain. For example, treatment of cyclic compound 5 with aqueous alkali affords 3-phenyl-1-3-phenyl-1-(3-phenyl-1H-1,2,4-triazol-5-yl)-1,2,4-triazol-5-yl-1H-1,2,4-triazol-5-one. Treatment of 3,7,11-triphenyltris[1,2,4]triazolo[4,3-a:4′,3′c:4″,3″-e][1,3,5]triazine (2) with HCl/SbCl₅ leads to the triazine ring opening giving rise to 5-(3-chloro-5-phenyl-1,2,4-triazol-4-yl)-3-phenyl-4-(5-phenyl-1H-1,2,4-triazol-3-yl)-1,2,4-triazole. Thermal cyclization of the latter produces 3,7,10-triphenyltris[1,2,4]triazolo[1,5-a:4′,3′c:4″,3″-e][1,3,5]triazine (13). Thermolysis of both cyclic compound 2 and cyclic compound 13 is accompanied by the Dimroth rearrangement to yield 3,6,10-triphenyl-tris[1,2,4]triazolo[1,5-a:1′, 5′-c:4″,3″-e][1,3,5]triazine (14). Compounds 13 and 14 are the first representatives of cyclic compounds with this skeleton. ¹³C NMR spectroscopy allows the determination of the isomer type in a series of tris[1,2,4]triazolo[1,3,5]triazines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 706–712, March, 2005.     

The preparation and coordination chemistry of 2,2′:6′,2″-terpyridine macrocycles—VI. Planar hexadentate macrocycles incorporating 2,2′: 6′,2″-terpyridine

The template condensation of 6,6″-bis(-methylhydrazino)-2,2′: 6′,2″-terpyridines L² and L³ with 2,6-pyridinedialdehyde may give a number of different products depending upon the metal ion which is used. In the presence of nickel(II) the products are either the nickel(II) complexes of the 18-membered ring macrocycles L⁴ or L⁵ or the free macrocycles. The metal ion acts as a transient template and is removed in a chloride ion specific demetallation. The use of dimethyltin(IV) as a template results in the formation of complexes of the ring contracted macrocycles L⁶ or L⁷.     

Electrochemical, spectroelectrochemical and theoretical studies on the reduction and deprotonation of the photovoltaic sensitizer [(H3-tctpy)Ru(NCS)3] (H3-tctpy=2,2′:6′,2′′-terpyridine-4,4′,4′′-tricarboxylic acid)

The electrochemical reduction of the black dye photosensitizer [(H₃-tctpy)Ru^II(NCS)₃]⁻ (H₃-tctpy=2,2′:6′,2′′-terpyridine-4,4′,4′′-tricarboxylic acid) used in photovoltaic cells has been found to be a complex process when studied in dimethylformamide. At low temperatures, fast scan rates and at a glassy carbon electrode, the chemically reversible ligand based one-electron reduction process [(H₃-tctpy)Ru(NCS)₃]⁻+e⁻[(H₃-tctpy√⁻)Ru(NCS)₃]²⁻ is detected. This process has a reversible half-wave potential (E^r_1/2) of −1585±20 mV versus Fc/Fc⁺ at 25°C. Under other conditions, a deprotonation reaction occurs upon reduction, which produces [(H_3−x-tctpy^x−)Ru(NCS)₃]^(1+x)− and hydrogen gas. Mechanistic pathways giving rise to the final products are discussed. The E^r_1/2-value for the ligand based reductions of the deprotonated complex is 0.70 V more negative than for [(H₃-tctpy)Ru(NCS)₃]⁻. Consequently, data obtained from molecular orbital calculations are consistent with the reaction [(H₃-tctpy)Ru(NCS)₃]⁻+e⁻→[(H₂-tctpy⁻)Ru(NCS)₃]²⁻+1/2H₂ yielding the monodeprotonated complex as the major product obtained after electrochemical reduction of [(H₃-tctpy)Ru(NCS)₃]⁻. The E^r_1/2-values for the metal based Ru^II/III process differ by 0.30 V when data obtained for the protonated and deprotonated forms of the black dye are compared. Electronic spectra obtained during the course of experiments in an optically transparent thin layer electrolysis configuration are consistent with the overall reaction scheme proposed on the basis of voltammetric measurements and molecular orbital calculations. Reduction studies on the free ligand, H₃-tcpy, are consistent with results obtained with [(H₃-tctpy)Ru(NCS)₃]⁻.     

1′,3′,3′-Trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-indoline]: its thermal enantiomerization and the equilibration with its merocyanine

The enantiomers of the title compound, the important photochromic material (RS)-1b, have been enriched semipreparatively by liquid chromatography. As a consequence, we were able to determine the barrier of the thermal interconversion (R)-1b(S)-1b via time-dependent polarimetry, amounting to ΔG^≠=85.9 kJ/mol at 22.0°C in d⁶-DMSO (Table 2). The thermal equilibration of the corresponding merocyanine 2b was monitored in d⁶-DMSO by time-dependent ¹H NMR, resulting in ΔG₁^≠=102.8 and ΔG₂^≠=92.0 kJ/mol at 22°C (Table 1). This means that, starting from (RS)-1b, the opened isomer 2b is attained by a slow reaction (ΔG₁^≠=102.8 kJ/mol, Fig. 4). Therefore, the merocyanine 2b cannot be identified with the intermediate required for the fast process of C(sp³)–O bond cleavage (ΔG^≠=85.9 kJ/mol) upon the above enantiomerization of (RS)-1b. Apparently, these two thermal isomerizations (Fig. 4) are independent of each other. The structure of the unknown intermediate of the interconversion (R)-1b(S)-1b must therefore differ from the known one of merocyanine 2b.

Table 1. Equilibration between spiro compounds (RS)-1 and merocyanines 2 at 22°C, measured by time-dependent UV absorptions[3] for (RS)-1a2a and by time-dependent ¹H NMR intensities for the other compounds

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Electrosynthesis of structured derivated polythiophenes: Application to electrodeposition of latex particles on these substrates

Synthesis of super-structured polymers is a great challenge because these entities could present a large choice of applications. Synthesis and electropolymerisation of thiophene derivatives are reported. Star-shaped 3D molecules are chosen because these structures ensure a high electronic conductivity. Three-dimensional structures could also assist the conductivity. 1,3,5-tris[5-(2,2′-dithienyl)]benzene 1, tris(2,2′-dithienyl)methylcarbinol 2, tris(5(2,2′:5′2″-terthienyl)methylcarbinol 3 are synthetised by different ways. UV and IR analysis are reported along with an AFM examination of the film. The first attempt of latex particle deposition on the film is also reported showing promising results in view of surface functionalisation.     

The C–HCl2Cu(II) synthon in the structural direction and assembly of supramolecular complexes with the 3,3′-bis(2-benzimidazolyl)-2,2′-dipyridine ligand and its N-substituted derivatives

Three new Cu(II) supramolecular complexes [Cu(L₁)Cl₂]·2DMF (1), [Cu(L₂)Cl₂] (2) and [Cu(L₃)Cl₂]·DMF (3) (L₁ = 3,3′-bis(2-benzimidazolyl)-2,2′-dipyridine, L₂ = 3,3′- bis(N-ethyl-2-benzimidazolyl)-2,2′-dipyridine and L₃ = 3,3′-bis(N-benzyl-2-benzimidazolyl)-2,2′-dipyridine) have been prepared and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. X-ray structural analysis of L₁, L₂·3.5H₂O and L₃·H₂O indicates that all three ligands adopt the trans conformation with the two benzimidazole fragments located on opposite sides of the dipyridyl backbone. While in complexes 1–3, all the ligands display the cis conformation and behave as bidentate chelating reagents to coordinate with Cu(II). The inorganic chloride ions always act as a reliable hydrogen bonded acceptor in these structures, and the resulting C–HCl₂Cu supramolecular synthons play a significant role in the formation and stabilization of the structures. Moreover, additional non-covalent interactions, such as C–Hπ, are also identified to extend the discrete (0-D) or low-dimensional (1-D) motifs into high-dimensional architectures.     

Preparation and Photophysical Properties of Mixed-Ligand Cyclometallated Complexes of Ir(III) with a Dendritic Bipyridine Ligand

Complexes [Ir(C^N)₂(G1-bpy)]PF₆, where C^N is a cyclometallating ligand derived from 2-(2′-thienyl)pyridine and 2-phenylpyridine, and G1-bpy is a dendritic bipyridine ligand of the first generation, 4,4′-bis[3″,5″-bis(benzyloxy)phenylethyl]-2,2′-bipyridine, were prepared and characterized by ¹H NMR, electronic absorption, and emission spectroscopy. The polyether dendritic substituents exert a “ soft” effect on the spectral and luminescence properties of the complexes, manifested as slight destabilization of the electronically excited charge-transfer state involving the bipyridine ligand, as compared to the model complexes [Ir(C^N)₂(bpy)]PF₆.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 705–711.Original Russian Text Copyright © 2005 by Kulikova, McClenaghan, Balashev.     

The effect of 2,2′-bipyridine, 2,2′:6′,2″-terpyridine and 1,10-phenantroline on radiation reduction of Rh(II) to Rh(I) complexes

Rh(II) acetate binuclear complexes have been reduced by gamma rays to Rh(I) complexes when 2,2′-bipyridine, 2,2′:6′,2″-terpyridine or 1,10-phenantroline ligands are present in aqueous methanol systems. These complexes exist in several forms possessing different absorption spectra. Their concentration depends on the ratio of the initial concentration of the ligands to Rh(II).     

Synthesis and photophysical properties of 2,5,8,11‐tetrakis(5‐hexylthiophen‐2‐yl)tetrathieno[2,3‐a:3′,2′‐c:2′′,3′′‐f:3′′′,2′′′‐h]naphthalene

The title compound, C₅₈H₆₄S₈, has been prepared by Pd‐catalysed direct C—H arylation of tetrathienonaphthalene (TTN) with 5‐hexyl‐2‐iodothiophene and recrystallized by slow evaporation from dichloromethane. The crystal structure shows a completely planar geometry of the TTN core, crystallizing in the monoclinic space group P2₁/c. The structure consists of slipped π‐stacks and the interfacial distance between the mean planes of the TTN cores is 3.456 (5) Å, which is slightly larger than that of the comparable derivative of tetrathienoanthracene (TTA) with 2‐hexylthiophene groups. The packing in the two structures is greatly influenced by both the aromatic core of the structure and the alkyl side chains.     

Rotational analysis of the v7,v11 (a′,a″) pair of bands of the infrared spectrum of the deuterium substituted propynal molecule C2H-CDO

The mid-infrared spectrum of the v₇,v₁₁ (a′,a″) pair of bands of the deuterium substituted propynal molecule C₂H-CDO was recorded at a resolution of about 0.08 cm⁻¹. An analysis of the pair of bands was completed using the method of simulation of the observed bands with synthetic spectra taking into account the effects of second order Coriolis interactions between the energy levels of the two bands. Best fit values for the changes in the rotational constants (A″ − A′), (B″ − B′) and (C″ − C′), the second order Coriolis constant ζ_7,11 and the δ_7,11 = v₁₁ − v₇ constant have been derived.     

Resonance Raman spectra of metalloporphyrins. On the methine-bridge vibrations of ferric octaethylporphyrins and its α′, β′, γ′, and δ′ deutero derivatives

Raman spectra of Fe³⁺ and Pd²⁺ octaethylporphyrin (OEP) and their α′, β′, γ′, and δ′ deutero derivatives were measured with the 5145, 4880 and 4765 Å lines of an Ar ion laser. Raman bands due to methine-bridge stretching vibrations were assigned and their vibrational amplitudes were calculated from the observed frequency shifts on deuterium substitution of methine-bridge hydrogens. These vibrations correspond to the spin-state sensitive Raman bands of heme proteins. On the basis of symmetry considerations and the observed polarizations, vibrational assignments of other Raman bands were made.     

Stereoselective total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone

The total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone is reported based on stereoselective reduction of δ-hydroxy β-keto ester to install 1,3-polyol system, cis Wittig olefination, and lactonization as the key steps. The synthesis of (−)-(6S,2′S)-epi cryptocaryalactone is also reported using syn-benzylidene acetal formation and a preferential Z-Wittig olefination reaction and lactonization as the key steps.     

Reaction and relaxation of vibrationally excited molecules: a classical trajectory study of Br + HCl(υ′) and Br + DCl(υ′) collisions

a quasiclassical trajectory study has been carried out to investigate the dynamics of collisions between Br + HCl (1 υ′ 4) and Br + DCl (υ′ = 2,3). For HCl (υ′ 2) and DCl (υ′ = 3), the endoergic reaction producing Cl + HBr occurs readily, and at approximately the same rate as vibrational deactivation in non-reactive collisions. For HCl(υ′ = 2) and DCl(υ′ = 3), where the initial vibrational energies are similar to |ΔE₀ for the reaction, the rates of both reactive and inelastic processes are quite strongly temperature dependent but the ratio of reactive to inelastic encounters is not a strong function of T. Comparison of the calculated results for Br + HCl(υ′ = 1) with experimentally determined rates strongly suggests that, at least at low temperatures, removal of HCl(υ′ = 1) by Br atoms occurs predominantly via electronically non-adiabatic vibrational relaxation.