Synthesis,characterization, electrochemical and solvatochromic investigations of novel monomeric and polymeric vanadyl Schiff-base complexes

This article describes the synthesis and characterization of oxovanadium(IV) complexes containing tetradentate Schiff-base ligands derived from condensation of ethylenediamine, meso-1,2-diphenyl-1,2-ethylenediamine, 1,2-orthophenylenediamine and 1,2-cyclohexanediamine with 5-bromo-3-nitro-2-hydroxybenzaldehyde. The novel VOL¹:[VO(5-Br-3-NO₂salen)], VOL²:[VO(5-Br-3-NO₂saloph)] and VOL³:[VO(5-Br-3-NO₂salchxn)] complexes were obtained in orange polymeric form with (V=O) stretching bands at 878, 884 and 884?cm^?1, respectively, but the VOL⁴ complex was obtained as a green monomer with (V=O) stretching band at 978?cm^?1. The redox process in acetonitrile was reversible for VOL⁴ and E° was determined to be approximately 950?mV but for VOL^1–3 this process was irreversible or quasi-reversible. The VOL⁴ complex is considerably soluble in a wide variety of solvents and shows solvatochromic behavior. The ² B ₂?→²?E(I) transition wavenumber shows a linear correlation to the D.N. of the solvent.     

2,3,9,10,16,17,24,25-Octakis(octyloxycarbonyl)phthalocyanines. Synthesis, spectroscopic, and electrochemical characteristics

A series of three novel 2,3,9,10,16,17,24,25-octakis(octyloxycarbonyl)phthalocyanine compounds M[Pc(COOC8H17)8] (M = 2H, Cu, Zn) (1-3) have been synthesized via the cyclic tetramerization of 4,5-di(octyloxycarbonyl)phthalonitrile, which was obtained by a newly developed procedure with o-xylene as starting material, promoted with organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in the absence and presence of metal salt like M(acac)2.H2O (M = Cu, Zn) in n-octanol at 120 degrees C. In addition to elemental analysis, these novel octakis(octyloxycarbonyl)-substituted phthalocyanine compounds have been characterized by a series of spectroscopic methods. The electrochemistry of these compounds was also studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. A significant shift to the positive direction for both the first oxidation and the first reduction of compound 1, relative to H2Pc, reveals the electron-withdrawing nature of octyloxycarbonyl groups attached to the peripheral positions of phthalocyanine. The effect of peripheral octyloxycarbonyl substitution on the electrochemistry of the series of phthalocyanines 1-3 has been reasonably explained by theoretical calculation results using the density functional theory (DFT) method.     

Synthesis, structures, and optical and electrochemical characteristics of novel crown-containing polythiophene systems

The synthesis, structures, and optical and electrochemical characteristics of novel crown-containing styryl mono-and polythiophenes were described. The double bonds were constructed by the Horner-Wadsworth-Emmons method. The Suzuki and Stille cross-coupling reactions were used to create polythiophene chains. Optical measurements revealed intense absorption and fluorescence of crown-containing polythiophenes; the band positions and shapes in their absorption and emission spectra depend on the structure of the polythiophene. The electrochemical characteristics of the compounds obtained were measured. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 932–939, May, 2007.     

Synthesis and spectroscopic and electrochemical studies of novel benzo- or 2,3-naphtho-fused tetraazachlorins, bacteriochlorins, and isobacteriochlorins

Benzene- or 2,3-naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized by using tetramethylsuccinonitrile as a source of hydrogenated sites. The derived compounds were characterized by using NMR spectroscopy, X-ray crystallography, electronic and magnetic circular dichroism (MCD) spectroscopy, and electrochemical and spectroelectrochemical methods. X-ray analysis revealed that the benzene-fused TAiBC deviates slightly from planarity at the hydrogenated sites as a result of the presence of sp(3) carbons, which prefer a nonplanar tetrahedral conformation. The spectral data were analyzed by using a band deconvolution technique. In the electronic absorption spectra of TAC and TABC species, the Q band splits into two intense components and smaller splittings were observed for the 2,3-naphthalene-fused derivatives relative to the benzo-fused species. In contrast, in the case of TAiBCs, the Q band splitting was apparently not observed in absorption spectra, as expected from the C(2v) molecular symmetry. However, MCD signals of the Q band in TAiBCs showed Faraday B terms, implying that the accidental degeneracy of the LUMO and LUMO+1 was broken even for adjacently ring-fused species. Relative molecular orbital energies were estimated by using cyclic and differential pulse voltammetry. The first reduction potentials were close for TACs and TABCs, although those of TAiBCs shifted to more negative potentials. In contrast, although TABCs and TAiBCs exhibited similar first oxidation potentials, those of TACs appeared at more positive potentials. These properties were reproduced and rationalized by molecular orbital and configuration interaction calculations within the framework of the ZINDO/S Hamiltonian. DFT-level frequency calculations have succeeded in reproducing the IR spectra for low-symmetry tetraazaporphyrin (TAP) derivatives for the first time. The relationship between structures and spectral features is discussed.     

Synthesis,spectroscopic/electrochemical characterization and DNA interaction study of novel ferrocenyl‐substituted porphyrins

We report the synthesis and characterization of two new meso‐ferrocenylporphyrins, with the ferrocenyl unit attached at the para position of a C₆F₄ group by a C? N bond with ? NH(CH₂)₂NH? ( 2a ) and ? NH(CH₂)₄NH? ( 2b ) spacers. Compounds 2a and 2b were characterized through elemental analyses, electrospray ionization high‐resolution mass spectrometry, ¹H NMR, UV–visible and fluorescence spectroscopies, electrochemistry and spectroelectrochemistry. The free base porphyrin 2 was included for comparison purposes. The binding ability of 2 and the porphyrin derivatives 2a and 2b with calf thymus DNA was determined using UV–visible and fluorescence spectroscopies. The results suggest that the interaction of these systems most probably occurs through π‐stacking by non‐classical modes involving the partial insertion of the C₆F₅ ring between adjacent base pairs on DNA and possible hydrogen interaction with the aliphatic ? NH(CH₂)_nNH? (n = 2 or 4) groups with calf thymus DNA. Moreover, we also demonstrate that porphyrins generate singlet oxygen species and show good photostability after irradiation.     

Synthesis, electrochemical, and spectroscopic properties of soluble perylene monoimide diesters

Perylene derivatives are an important class of n-type semiconductors. With the exceptions of bay-substituted and N-swallow-tail alkyl/tert-butyl substituted derivatives, most perylene diimides are insoluble. The recently reported perylene tetraesters are highly soluble, but are less electron-deficient. In this paper, a series of perylene monoimide diesters have been synthesized, which have good solubility and acceptable electron-accepting property due to the introducing of imide and ester groups in one perylene molecule. Their electrochemical properties and structural ordering were examined by cyclovoltammetry and X-ray diffraction technique, respectively. Their absorption and emission spectra are reported and discussed.     

Synthesis,crystal structure and spectroscopic properties of a copper(II) complex of the Schiff-base derived from picolinaldehyde N-oxide and 4-aminoantipyridine

The Schiff-base (PNOAAP) derived from picolinaldehyde N-oxide and 4-aminoantipyrine, and its copper(II) complex: [Cu(PNOAAP)₂(EtOH)₂]₂(ClO₄)₄ (1) has been prepared and characterized by elemental analysis, i.r., ¹H-n.m.r. spectrum, and single crystal X-ray crystallographic determination. The PNOAAP ligand isomerizes from trans to cis after chelating to copper(II).     

Synthesis, structural, spectroscopic and electrochemical studies of carborane substituted naphthyl selenides

New unsymmetrical selenides bearing an o-carborane and a naphthalene ring as the substituents were prepared by the cleavage of the corresponding diselenides. The compounds were characterized by means of spectroscopic and analytical methods. (77)Se NMR signals of the selenium atoms attached to the carbon atoms of the carborane cages are shifted downfield in comparison to those bonded only to the aromatic rings, indicating an electron withdrawing effect of the o-carboranyl substituent. Compounds 1-(2-R-1,2-dicarba-closo-carboranyl)naphthyl selenides (R = Me, 1; Ph, 2) were characterized by means of single crystal X-ray diffraction. The influence of the electronic nature of the substituents attached to the selenium atoms on the structural parameters and packing properties of naphthyl selenides are discussed. Theoretical calculations and cyclic voltammetry (CV) studies were carried out to compare the bonding nature of carboranyl and analogous aryl selenium compounds. Cyclic voltammetry studies of naphthyl carboranyl mono and diselenides have shown that the carboranyl fragment polarizes the Se lone pair making it less prone to generate a Se-Se bond.     

Synthesis, spectroscopic, and electrochemical properties of three tetrathiafulvalenes attached to perylene

Three donor–acceptor dyads 1–3 comprising of a tetrathiafulvalene (TTF) unit linked with perylene by a simple σ-bond were synthesized and characterized. Spectroscopy and cyclic voltammetry provided an indication that intramolecular charge-transfer interactions in their ground states between TTF and perylene for dyads 1–3 are negligible. Compared with the compound perylene, dyads 1–3 exhibited large fluorescence quenching, which might be ascribed to photo-induced electron transfer interaction between TTF and perylene units in the excited state. Correspondence: Yongjia Shen, Laboratory of Advanced Materials, Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, P.R. China.     

Synthesis, spectroscopic characterization and alignment of novel azobenzene-containing monomers

A series of novel bifunctionalized photochromic monomers were synthesized, focusing on those with polymerizable acrylic/methacrylic groups attached to both ends of an azobenzene core via flexible spacers. The phase behaviour of the monomers was investigated using DSC, polarizing optical microscopy and X-ray diffraction. The change in UV-vis absorbance of the monomers under illumination with non-polarized/polarized UV light was studied for both solutions and thin films; also studied was its relaxation in the dark. On illumination with LPUV light, in-plane reorientation of the molecules normal to the polarization of the exciting UV light, and aggregation of the molecules in the films, were found.     

Nitro-functionalized oligothiophenes as a novel type of electroactive molecular material: spectroscopic,electrochemical, and computational study

A novel series of terthiophenes bearing electron-donor and electron-acceptor groups at the end alpha-positions has been prepared. The analysis of the UV-vis, infrared, and Raman spectra, performed with the aid of density functional theory calculations, shows that the asymmetrically substituted nitro compounds PhT(3)NO(2) and BrT(3)NO(2) behave as push-pull systems and present an intense photoinduced charge transfer in the visible spectrum. The symmetrically substituted dinitro compound NO(2)T(3)NO(2) displays a highly delocalized structure with a low single-double bond length alternation and also displays a low-energy absorption band in the visible region. The novel nitroterthiophenes possess attractive electrochemical properties since they generate stable species both upon oxidation and reduction. Oxidation mainly involves changes in the oligothiophene backbone and leads to the formation of stable cations even for NO(2)T(3)NO(2). Reduction is mainly nitro-centered but also affects the conjugated structure. Radical anions and dianions are formed for PhT(3)NO(2) and BrT(3)NO(2). Dianions, not radical anions, and trianions are obtained for NO(2)T(3)NO(2). Nitro-functionalized terthiophenes are shown to be very promising as electroactive molecular materials since they behave as push-pull systems, present a very intense photoinduced charge transfer in the visible region, and could act as both n- and p-channel conductors in organic electronic transistors.     

Synthesis and structural,spectroscopic, and electrochemical characterization of new ruthenium dimethyl sulfoxide nitrosyls

The reactivity of ruthenium(II)- and ruthenium(III)-chloride-dimethyl sulfoxide precursors and of the antimetastatic drug [ImH][trans-RuCl(4)(dmso-S)(Im)] (NAMI-A, Im = imidazole, dmso = dimethyl sulfoxide) toward NO was investigated. Treatment of [(dmso)(2)H][trans-RuCl(4)(dmso-S)(2)] and mer-RuCl(3)(dmso)(3) with gaseous NO yielded [(dmso)(2)H][trans-RuCl(4)(dmso-O)(NO)] (1) and mer,cis-RuCl(3)(dmso-O)(2)(NO) (2), respectively. Thus, coordination of the strong pi-acceptor NO induces a S to O linkage isomerization of the dmso trans to it to avoid competition for pi-electrons. In light-protected nitromethane solutions, complex 2 equilibrates slowly with the two isomers mer-RuCl(3)(dmso-S)(dmso-O)(NO) (3), with NO trans to Cl, and mer-RuCl(3)(dmso-S)(dmso-O)(NO) (4), with NO trans to dmso-O; the equilibrium mixture consists of ca. 64% 2, 3% 3, and 33% 4. Treatment of the Ru(II) precursor trans-RuCl(2)(dmso-S)(4) with gaseous NO in CH(2)Cl(2) solution yielded the nitrosyl-nitro derivative trans,cis,cis-RuCl(2)(dmso-O)(2)(NO)(NO(2)) (5). Finally, [(Im)(2)H][trans-RuCl(4)(Im)(NO)] (6) was prepared by treatment of [ImH][trans-RuCl(4)(dmso-O)(NO)] (1Im) with an excess of imidazole in refluxing acetone. The spectroscopic features are consistent with the [Ru(NO)](6) formulation for all complexes, that is, a diamagnetic Ru(II) nucleus bound to NO(+). Compounds 1, 2, 5, and 6 were characterized also by X-ray crystallography; they all show a linear nitrosyl group, with short Ru-NO bond distances consistent with a strong d(pi) --> pi NO back-bonding. An unusual inertness of O-bonded dmso was observed in compound 1. Complexes 1, 2, 3, 5, and 6 are all redox active in DMF solutions showing irreversible reductions whose peak potentials depend on the other ligands attached to the Ru metal center. The site of reduction is the NO(+) moiety. The reduced complexes are not stable and release a Cl(-) or NO(2)(-) ligand followed by the NO(*) radical. The chemical reactions following electron transfer are all fast (rate constant >100 s(-1) at 293 K). The Ru product species are not redox active within the DMF window.     

Synthesis,characterization and spectroscopic investigation of a novel phenylhydrazone Schiff base with solvatochromism

A novel Schiff base of 4,5-diazafluorene-9-p-nitrophenylhydrazone (DAFND) has been synthesized and characterized. The crystal structures of DAFND and its analogue 4,5-diazafluorene-9-phenylhydrazone (DAFPD) were determined by single crystal X-ray diffraction method. X-ray analyses reveal that DAFPD comprise of a nonplanar molecule and all atoms of DAFND are essentially coplanar. The color of DAFND changes from brown to blue when heated, so called thermochromism and the spectroscopic properties of the two compounds are investigated by electronic absorption spectra, showing DAFND possess solvatochromism, while DAFPD does not have thermochromic and solvatochromic properties. The λ_max of DAFND within various pure solvents are different ranging from 370 nm in toluene to 614 nm in pyridine. The imaginable mechanisms of thermochromism and solvatochromism are proposed.     

Synthesis, spectroscopic and electrochemical property of an unsymmetrical porphyrin and its Zn compound

<正>In this article,a new 5-(p-maleicaminophenyl)-10,15,20-triphenylporphyrin(H_2P) and relative zinc compound(ZnP) were synthesized and characterized by means of elemental analyses,UV-vis,IR,MS and ~1H NMR spectroscopies.Furthermore,we have investigated the fluorescence spectroscopy of these compounds.The oxidation and reduction properties of the compounds were studied by the cyclic voltarnmetry,the oxidation-reduction potentials were obtained.     

Synthesis,structures, and spectroscopic properties of Hg(II) complexes of bidentate NN and tridentate NNO Schiff-base ligands

Reactions of HgX₂ (X?=?Cl, N₃, NO₃) with (E)-2-methoxy-N-(pyridin-2-ylmethylene)aniline (L¹) and (E)-4-methoxy-N-(pyridin-2-ylmethylene)aniline (L²) in ethanol gave two monomers, [HgL¹(Cl)₂] (1) and [HgL²(NO₃)₂(DMSO)] (5), and three coordination polymers, {[HgL¹(N₃)₂]₂·Hg(N₃)₂}_n (2), [HgL²(Cl)₂]_n (3), and [HgL²(NO₃)₂]_n·nCH₃CN (4). Compounds 1–5 were characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction. The common feature of monomeric 1 and 5 is the presence of intra- and intermolecular Hg–O bonds. In the absence of these, polymeric structures arise as a result of azide, chloride, and nitrate bridging in 2, 3, and 4, respectively. Fluorescent properties of 1–5 were also investigated.     

Synthesis and spectroscopic characteristics of 2,3,-biindolyl and 2,2-indolylpyrroles

A general and selective method has been achieved to synthesize 2,3'- biindolyls and 2,2'-indolylpyrroles through an acid catalysed reaction of 3-bromoindoles with indoles or pyroles. I.R., ¹H-NMR, ¹³C-NMR and MS data of the dimers are also reported.     

Characteristic and spectroscopic properties of the Schiff-base model compounds

Two series of conjugated aromatic imines (Schiff-base model compounds) with different central groups and various side-group substitutions have been synthesized and characterized by elemental analysis, differential scanning calorimetry (DSC) technique, hydrogen nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and ultra-violet and visible light (UV–vis) spectroscopy measurements. The UV–vis absorption of solutions of these compounds in dimethylacetamid (DMA), chloroform and methanol was investigated in the optical range from 240 to 450 nm, where two distinct absorption bands: at 250–280 and 315–360 nm with the different level of absorption have been observed. The influence of compound molecular structure and polarity of solvent on the absorption spectra and the possible optical transitions have been discussed. Structure of diamines in the azomethine models fundamentally affected their spectroscopic properties and conjugation of π-electrons.     

Synthesis and spectroscopic properties of novel benzo[a]phenanthridines

Condensation of arylidene-2-naphthylarnines with 5,5-dimethylcyclohexane-1,3-dione (dimedone) gives novel 2,2-dimethyl-5-R-1,2,3,4,5,6-hexahydrobenzo[a]phenanthridin-4-ones. Treatment of azomethines containing an ortho hydroxyl group in the aldehyde fragment gives the corresponding 3,3,6,6-tetramethyl-9-R-1,2,3,4,5,6,7,8-octa-hydroxanthene-1,8-diones. The IR, UV, PMR, and mass spectra of the compounds synthesized have been studied.