Synthesis and light absorption of benzotellurazole crown ether cyanine dye

Various methods for synthesis of 2-methyl-5,6-(1,4,7,10,13-pentaoxatridecamethyl-ene)benzotellurazole (8) are described. Under different conditions, alkylation of compound 8 with methyl iodide gave telluronium salt 1,2-dimethyl-5,6-(1,4,7,10,13-pentaoxatridecamethylene)benzo-tellurazolium iodide (15) or quaternary ammonium salt 2,3-dimethyl-5,6-(1,4,7,10,13-pentaoxatri-decamethylene)benzotellurazolium iodide (14) in high yields, repectively. The cyanine dye 3,3'-dimethyl-5,6,5',6'-bis(1,4,7,10,13-pentaoxatridecamethylene)telluracarbocyanine iodide (16) is obtained by condensation of 14 with ethyl orthoformate in acetic anhydride. The visible absorption of the cyanine dye is also discussed.     

Electronic structure and OK α spectra of carbonyl-containing pentafluorobenzene derivatives

The OK spectra have been obtained for several pentafluorobenzene derivatives, using acetone as a reference molecule. The MNDO calculations have been performed for all the compounds under study, and simulated spectra have been plotted. The -interaction between the carbonyl group and the pentafluorophenyl ring has been shown to occur mostly in the system of inner molecular orbitals.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 314–318, February, 1993.     

Electronic structure and aromaticity of planar singlet π-electron monocyclic π2 carbenes

Induced -electron ring currents and relative diamagnetic susceptibilities of planar singlet -electron monocyclic ² carbenes are calculated in the coupled variant of perturbation theory in the CNO method. It is shown that the parity theorem holds for charged planar ² and ² carbenes formally generated by the detachment of a proton or a hydride ion from alternant hydrocarbons. This leads, in such carbenes, to the same energies of singlet-singlet and singlet-triplet transitions, electric polarizabilities, conjugation energies, -electron ring currents, diamagnetic susceptibilities and current contributions to chemical shifts, whereas the charge contributions to the latter are of opposite signs.Donbas State Academy of Building and Architecture, 1 Derzhavina St., 339023 Makeevka, Donetsk Region, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 3, pp. 157–162, May–June, 1996. Original article submitted December 5, 1994.     

Unusual supramolecular donor—acceptor complexes of bis(crown)stilbenes and bis(crown)azobenzene with viologen analogs

The results of the comprehensive study of novel supramolecular donor-acceptor complexes of bis(crown)stilbenes and bis(crown)azobenzene with viologen analogs are generalized. The original methodology for self-assembling of the organic donor-acceptor complexes possessing a very high thermodynamic stability is described. The hydrogen bonds between the peripheral fragments of the donor and acceptor play the key role in the self-assembling. The influence of different structural factors on the thermodynamic stability of the supramolecular donor-acceptor complexes and the efficiency of charge-transfer interactions between the donor and acceptor are discussed. The driving forces of the reaction leading to exotic trimolecular charge-transfer complexes are considered. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 779–787, April, 2008.     

Spectroscopic and electrochemical sensing of lanthanides with π-extended chromophores incorporating ferrocenes and a coordinative end

In this study, we report the synthesis and characterization of three novel "push-pull" chromophores, in which multiple phenylenevinylene units are endcapped by ferrocene as donor units and malonate moieties as acceptor units. These chromophores have spectroscopic and electrochemical characteristics which consistently change according to the extension of the conjugated bridge, thus to the variation of the HOMO-LUMO band gap. The 1,3-dicarbonyl units, directly incorporated into the conjugated molecular structures, are able to coordinate Lewis acid-like cations, such as lanthanides, as confirmed by UV/Vis, (1)H NMR and cyclic voltammetry studies. The UV/Vis spectroscopic response upon complexation with Sc(3+) or Eu(3+) as the triflate salts is rather unselective and nonlinear in going from the least to the most π-extended chromophore. Binding studies in MeCN, analyzed via equilibrium-restricted factor analysis, give values between log K(a) = 1.21 and 3.07 and affirm a 1?:?1 stoichiometry of the host:guest complexes in all cases. On the other hand, cyclic voltammetry reveals a selectivity in the response to Sc(3+) coordination over Ln(3+) (Eu(3+), but also Lu(3+) and Er(3+) were tested) for the two shorter chromophores, whereas the ligand with the longest π-bridge is able to sense Er(3+) (ΔE(1/2) complexed/uncomplexed chromophore = 20 mV) selectively over the other lanthanides.     

IR absorption spectra and structure of 4-cyano-4′,-p-alkoxybiphenyls

The IR absorption spectra of 4-cyano-4,-p-alkoxybiphenyls were investigated experimentally (in the range 100–3200 cm^–1 at 100–400 K), and they were interpreted on the basis of a calculation of the frequencies, forms, and intensities of the normal vibrations of various conformers of the propyloxycyanobiphenyl molecule. Temperature and phase changes in the parameters of the IR spectrum are explained by a change in the conformational composition and intermolecular interactions in the investigated liquid crystals.Institute of Physics, Ukrainian Academy of Sciences. Saratov State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 105–111, January–February, 1993.     

The effects of substituents and solvents on the ground-state π-electronic structure and electronic absorption spectra of a series of model merocyanine dyes and their theoretical interpretation

Two series of new merocyanine dyes have been synthesised and the dependence of their electronic structure on substituents and solvents has been studied by NMR spectroscopy, by using both the NMR (13)C chemical shifts between adjacent C atoms in the polymethine chain and the (3)J(H,H) coupling constants for trans-vicinal protons. The widely used valence bond (VB) model based on two contributing structures cannot account theoretically for the observed alternating π-electron density in the polymethine chain. In addition, the prediction of zero-π-bond order alternation (or zero-bond length alternation) by this model is also incorrect. However, the results are consistent with the predictions of a qualitative VB model which considers the resonance of a positive charge throughout the whole polymethine chain. Based on this model and the Franck-Condon principle the effect of substituents and solvents on the fine structure of the electronic spectra of these dyes can be explained as vibronic transitions from the vibrational state v = 0 to v', where v is the vibrational quantum number of the totally symmetric C=C valence vibration of the polymethine chain in the electronic ground state and v' is that in the electronic excited state. In contrast, neither the effects of substituents or solvents on the electronic structure of merocyanines and their electronic spectra can be accounted for by the simple two state VB model.     

Synthesis and Supramolecular Structure of a Novel π-Extended TTF Derivative

A novel π-extended TTF derivative （C24H2ON658, Mr=649.02） has been synthesized and characterized by IR, ^1H NMR and MS. The crystal structure was prepared by crystallization from CH2Cl2-MeOH. The crystal belongs to the monoclinic system, space group P21/c with a = 5.465（5）, b = 26.835（5）, c = 10.180（5）A, β= 101.929（5）°, V = 1460.7（15） A^3, Z = 2, Dc = 1.476 g/cm^3, F（000） = 668,μ = 0.638 mm^-1, the final R = 0.0390 and wR = 0.0586 for 1694 observed reflections with I 〉 2σ（I）. The structure reveals planarity of the two dithiole rings, different from the boat-shaped structure usually found in neutral derivatives of TTF. The central ring of the benzene also adopts a planar conformation, while it is twisted from planarity of the two dithiole rings and forms a dihedral angle of 61.8°. The molecule exhibits a three-dimensional supramolecular architecture constructed through hydrogen bonds. In the molecular structure a noticeable feature can be found that there exist S…S interactions which further reinforce the 3D supramolecular framework.     

π* ← n and π* ← π absorption spectra of aminopyrazine

π* ← n and π* ← π absorption spectra of aminopyrazine have been recorded and analysed assuming C_s symmetry for the molecule.     

Electrospray ionization mass spectrometric detection of self-assembly of a crown ether complex directed by π-stacking interactions

The self-assembly of ligand-metal-ligand sandwich complexes involving a novel quinoxaline-containing crown ether, 1, was studied by electrospray ionization mass spectrometry (ESI-MS). Donor-acceptor π-stacking interactions between the electron-poor quinoxaline group of 1 and electron-rich benzene groups from benzo- or dibenzo-18-crown-6 were found to significantly enhance the formation of mixed-ligand sandwich complexes with a free energy gain of up to 17 kJ/mol relative to sandwich formation involving macrocycles without such aromatic functionalities. The relative intensities of the sandwich complexes were greatest with the alkali metals Na⁺, K⁺, and Rb⁺ as well as with the ammonium ion in equimolar concentrations with the macrocycles. The preferential formation of the mixed-ligand sandwich complexes demonstrated that donor-acceptor π-stacking interactions contribute to the assembly of molecular structures and can be monitored by ESI-MS.     

Synthesis and photochemical reactivity of caged glutamates with a π-extended coumarin chromophore as a photolabile protecting group

‘Caging’ and ‘uncaging’ bioactive substrates are key techniques in studying a wide variety of biological processes. In the present study, two-types of novel caged glutamates with a two-photon absorption (TPA) core, that is, π-extended coumarin, were synthesized and their photochemical release of glutamate was analyzed. The high yields of glutamate (>92%) were observed in the photolysis of compounds 1 and 10, respectively.     

Synthesis and spectroscopic properties of a novel zinc phthalocyanine with four 17-membered crown ether voids

A novel zinc phthalocyanine containing four 17-crown-5 ether voids(17C5ZnPc) has been synthesized and characterized. UV-visible absorption and fluorescence emission spectra and as-sociated photophysical parameters have been determined. In contrast to most of the crown ether substituted phthalocyanines, no cofacial dimer formation is observed in the presence of alkali metal salts. In addition to the fluorescence at 710 nm from S1, a strong upper excited state (Soret 52) emission around 424 nm has been detected for the first time in the phthalocyanine series. Fluorescence decay of S1 and S2 emission can be analyzed by mono- and biexponential fits respectively. X-ray structure analysis showed that the crown ether unit is conformationally deformed and oblate that may account for the unusual spectroscopic properties.     

Spectral properties and structures of supramolecular complexes of naphthylpyridine with β-cyclodextrin

The electronic absorption and fluorescence spectra of 4-(2-naphthyl)pyridine (1) and N-methyl-4-(2-naphthyl)pyridinium perchlorate (2 ⁺·ClO₄ ^–) were studied in aqueous solutions in the absence and presence of -cyclodextrin (-CD). In aqueous solutions and organic solvents in the presence of water or H⁺ ions, compound 1 exhibits intense fluorescence with a maximum at 21 270 cm^–1, and its quantum yield in an aqueous solution is 0.9±0.09. The same fluorescence spectrum was detected for an aqueous solution of 2 ⁺·ClO₄ ^–. In an aqueous solution, compound 1 and -CD form stable fluorescing supramolecular 2:2 complexes, whose structure was calculated by the quantum-chemical MNDO/PM3 method. The formation of these complexes induces a hypsochromic shift of the fluorescence maximum of 1 by 5000 cm^–1. The stability constant of the complex is 2·10³ L mol^–1. A decrease in the pH results in the formation of a protonated form of 1(1·H⁺) and destruction of the complex, thus favoring the escape of the substrate from the -CD cavity. The quantum-chemical calculations showed that the insertion of 1 into the -CD cavity is thermodynamically more favorable than hydration; on the contrary, the formation of 1·H⁺ increases dramatically the hydration energy, which promotes the escape of 1·H⁺ from the -CD cavity; cation 2 ⁺ does not form a complex with -CD; in the thermodynamically most favorable 2:2 complex, the naphthalene fragments of two molecules 1 are parallel to each other in a broad section of the -CD dimer constructed according to the head-to-head type.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2420–2425, November, 2004.     

The structure and EPR spectra of binuclear copper(II) complexes with acyldihydrazones of β-diketones

The synthesis and structure of binuclear copper(II) complexes with acyldihydrazones of some β-diketones are described. The molecular structure of the copper(II) complex [Cu₂L·4Py] with trifluoroacetylacetone succinyldihydrazone (H₄L) was determined by the single-crystal X-ray analysis. Central atoms are bridged by a chain of seven σ-bonds with a Cu...Cu distance of 8.750 Å. EPR spectra of copper(II) complexes with acyldihydrazones of trifluoroacetylacetone and lower dicarboxylic acids containing from one to four methylene groups in the aliphatic spacer show the seven-line HFS due to spin-spin coupling of unpaired electrons with the two equivalent copper nuclei (g = 2.110, a = (38.5–40.5)⊙10^?4 cm^?1). By extending polymethylene spacer, as well as by modifying starting β-diketone, an exchange interaction between paramagnetic centers is suppressed.     

Spectroscopic study of charge transfer complexes of some benzo crown ethers with π-acceptors DDQ and TCNE in dichloromethane solution

Formation of the charge transfer complexes between benzo-15-crown-5, dibenzo-18-crown-6, dibenzo-24-crown-8 and dibenzo-crown-10 and the π-acceptors DDQ and TCNE in dichloromethane solution was investigated spectrophotometrically. The molar absorptivities and formation constants of the resulting 1:1 molecular complexes were determined. The stabilities of the complexes of both π-acceptors vary in the order DB18C6 > DB3OC10 ⋍ DB24C8 > B15C5. All of the resulting complexes were isolated in crystalline form and characterized. The influences of potassium ion on the formation and stability of the TCNE molecular complexes were studied. Effects of the crown ether structure and the role of the K⁺ ion on the formation of charge transfer complexes are discussed.     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes comprising two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W- Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ⁵-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅, as well as mononuclear model complexes Cp(CO)₂Fe(CH)₂Ph (8), CpMn(CO)₃ (9), and (⁶-C⁶H⁶)Cr(CO)³ (10). The spectra were interpreted on the basis of the local symmetry of each metal carbonyl center. The positions of vCOs are determined by the mutual electronic effect of each center. CpmM(CO)_n groups are strong electron acceptors and cause an increase in vCOs of adjacent M(CO)_n groups. Cp(CO)_nM groups, being electron donors, cause a decrease in the frequencies of neighboring groups. In trinuclear complexes, the frequencies of the central Fe(CO)₂ group are not changed much due to the compensation of donor and acceptor influences of two neighboring substituents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1948–1951, November, 1994.This project was supported by the Russian Foundation for Basic Research (project code No. 93-03-18592).     

Vibrational spectra and structure of “staircase” carbonyl π-complexes of transition metals

FTIR spectra have been studied for staircase cyclopentadienyl complexes containing two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)₂Fe-CpmMn(CO)₃ (1), Cp(CO)₂Fe-CpmFe(CO)₂CH₂Ph (2), Cp(CO)₂Fe-Cpm(CO)₂Fe-CpmMn(CO)₃ (3), Cp(CO)₂Mo-Cpm(CO)₂Fe-CpmMn(CO)₃ (4), Cp(CO)₃W-Cpm(CO)₂Fe-CpmMn(CO)₃ (5), Cp(CO)₂Fe-Cpm(CO)₂Fe-BmCr(CO)₃ (6), Cr(CO)₃Bm-CpmFe(CO)₂CH₂Ph (7), where Cp = ₅-C₅H₅, Cpm = ¹⁵-C₅H₄, Bm = ¹⁶-C₆H₅. Temperature-dependent FTIR spectra were measured inn-pentane solutions over a wide temperature range and in the low-temperature solid matrices of argon and nitrogen. Rotamers, formed due to rotation about the metal-carbon -bond, were found in solutions and matrices. A molecular mechanics calculation of1 proved the possibility of such rotation.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1952–1956, November, 1994.The authors are grateful to the Russian Foundation for Basic Research (project code No 93-03-18592) and to the International Science Foundation (project code No MEQ000).     

Novel adamantane-bearing anilines and properties of their supramolecular complexes with β-cyclodextrin

Several novel anilines bearing 1-adamantyl substituents that are useful for drug modification were synthesised from the corresponding 1-adamantyl (nitrophenyl) ketones. The host–guest systems of these prepared ligands with β-cyclodextrin (β-CD) were studied using electrospray ionisation mass spectrometry, NMR spectroscopy, titration calorimetry and semi-empirical calculations. The complexes with 1:1 stoichiometry were found to predominantly exist as pseudorotaxane-like threaded structures with the adamantane cage sitting deep in the cavity of β-CD close to the wider rim. Such geometry was observed for all examined amines and is independent of their structure and/or presence of protic substituents.     

FT-IR and raman spectra of a series of metallo-β-cyclodextrin complexes

A series of metallo--CD complexes were prepared and formulated as [M₂(OH)₂ -CD·2 H₂O] ^n– . Changes in the FT-IR and Raman Spectra of-CD on coordination may be taken as evidence for complexation and support for a hydroxy bridged binuclear structure. Further support was obtained from uv/visible and magnetic moment measurements.     

Synthesis and characterization of π-extended thienoacenes with up to 13 fused aromatic rings

π-Extended thienoacenes that comprise alternatively arranged anthracene and thieno[3,2-b]thiophene moieties and have 8 or 13 aromatic rings were synthesized. The delocalization of their HOMO and LUMO orbitals is over the entire molecules, and low-lying HOMO levels endow them good stability.