Preparation and coordination complex of the first imine-bridged tetrathiafulvalene-pyridine donor ligand

The first imine-bridged pyridyltetrathiafulvalene building block (TTF-CH=N-Py, 1) has been synthesized via the Schiff base condensation of formyltetrathiafulvalene and 2-aminopyridine. The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [CuII(hfac)2(TTF-CH=N-Py)] (2) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center, thus making this ligand an attractive precursor for the assembly of pi-d systems.     

Effects of masking noise on vowel and sibilant contrasts in normal-hearing speakers and postlingually deafened cochlear implant users

The role of auditory feedback in speech production was investigated by examining speakers' phonemic contrasts produced under increases in the noise to signal ratio (N/S). Seven cochlear implant users and seven normal-hearing controls pronounced utterances containing the vowels /i/, /u/, /e/ and /ae/ and the sibilants /s/ and /I/ while hearing their speech mixed with noise at seven equally spaced levels between their thresholds of detection and discomfort. Speakers' average vowel duration and SPL generally rose with increasing N/S. Average vowel contrast was initially flat or rising; at higher N/S levels, it fell. A contrast increase is interpreted as reflecting speakers' attempts to maintain clarity under degraded acoustic transmission conditions. As N/S increased, speakers could detect the extent of their phonemic contrasts less effectively, and the competing influence of economy of effort led to contrast decrements. The sibilant contrast was more vulnerable to noise; it decreased over the entire range of increasing N/S for controls and was variable for implant users. The results are interpreted as reflecting the combined influences of a clarity constraint, economy of effort and the effect of masking on achieving auditory phonemic goals-with implant users less able to increase contrasts in noise than controls.     

Triphenylphosphinoxid (L) als Solvens und Ligand für Metallphthalocyaninate; Synthese und Struktur von [{Li(L)}2(μ‐pc)], [Li(L)4][Lipc] · Solvat, [Mg(L)pc] · Solvat und [Zn(L)pc] · Solvat

Triphenylphosphine Oxide (L) as Solvent and Ligand for Metallophthalocyaninates; Synthesis and Structure of [{Li(L)}₂(μ‐pc)], [Li(L)₄][Lipc] · Solvate, [Mg(L)pc] · Solvate, and [Zn(L)pc] · Solvate Triphenylphosphine oxide (L) coordinates to metallophthalocyaninates of Li, Mg and Zn at 300 °C. After purification and recrystallization in different solvents the very soluble and stable title compounds have been isolated and structurally characterized. In [{Li(L)}₂(μ‐pc)], the Li atom lies in a distorted tetragonal pyramid of four isoindole N atoms (N_i) at a distance varying between 2.163(5) and 2.301(5) Å, and an O atom at 1.863(5) Å. In [Li(L)₄] · [Lipc] · S, the Li atom of the cation coordinates four O atoms in a distorted tetrahedral arrangement at a distance varying from 1.887(9) to 1.953(9) Å, while the Li atom of the anion is in a quasi quadratic planar geometry of four N_i atoms (1.951(9)–1.977(9) Å) with the Li atom being displaced by 0.15 Å out of the (N_i)₄ plane. The structural data of the distorted tetragonal pyramidale Mg(N_i)₄O moiety in [Mg(L)pc] and the solvates [Mg(L)pc] · S (S = CH₂Cl₂, thf, 2py) generally do not vary significantly: Mg–N_i/2.035(3) –2.061(3) Å, Mg–O/1.955(2)–2.000(3) Å. The Mg atom is displaced by ca. 0.52 Å out of the (N_i)₄ plane towards the O atom and the Mg–O–P moiety is bent (ca. 153°). [Zn(L)pc] · S crystallizes as a mixed crystal of equal parts of the conformer with a bent (155.1(3)°) and that of a quasi linear Zn–O–P moiety (174.2(3)°). Structural data of the Zn(N_i)₄O moiety: (Zn–N_i)_av: 2.024/2.013 Å; Zn–O: 2.050(4)/2.081(4) Å; Zn–(N_i)₄: 0.40/0.33 Å. In the crystal, the Mg and Zn derivates aggregate in double layers forming pairs. The pc ligands in the triclinic complexes with good overlap of the neighbouring pc ligands are in a waving conformation, while those in the monoclinic complexes with weak overlap are in a concave conformation.     

trans-Bis(triphenylphosphin)phthalocyaninato(2–)rhenium(II): Synthese,Eigenschaften und Kristallstruktur

trans -Bis(triphenylphosphine)phthalocyaninato(2–)rhenium(II): Synthesis, Properties, and Crystal Structure Dirheniumheptoxide reacts with phthalodinitrile in boiling 1-chloronaphthalene and subsequent reprecipitation of the green raw product from conc. sulfuric acid to yield an oxo-phthalocyaninate of rhenium, which is reduced by molten triphenylphosphine forming dark green trans-bis(triphenylphosphine)phthalocyaninato(2–)rhenium(II), ^trans[Re(PPh₃)₂pc^2–]. The latter crystallizes triclinic in the space group P 1 with the cell parameters as follows: a = 11.512(2) Å, b = 12.795(2) Å, c = 12.858(2) Å, α = 64.42(2)°, β = 79.45(2)°, γ = 72.74(1)°; V = 1628.1(5); Z = 1. Re is in the centre of the (N_p)₄ plane (N_p: N1, N3) and coordinates two triphenylphosphine ligands axially in trans position. The average Re–N_p and Re–P distances are 2.007(1) and 2.516(3) Å, respectively. Despite the many extra bands the typical B, Q and N regions of the pc^2– ligand are observed at ca. 16500, 28900/32900 and 35300 cm^–1. A weak band group at ca. 8900 cm^–1 is attributed to a trip-multiplet transition, another one at ca. 14500 cm^–1 to a P → Re charge transfer. The vibrational spectra are dominated by internal vibrations of the pc^2– ligand. The very weak intensity of the IR bands at 905 and 1327 cm^–1 are diagnostic of the presence of Re^II.     

Structural ordering of ω-ferrocenylalkanethiol monolayers on Au(1 1 1) studied by scanning tunneling microscopy

The self-assembly of ω-ferrocenylalkanethiols (FcCnSH) with different alkyl-spacer lengths on Au(1 1 1) substrates has been studied by scanning tunneling microscopy (STM). Upon deposition at room temperature FcCnSH molecules tend to form multilayers, while by thermal treatment monolayer formation, a rearrangement of the molecules and the formation of ordered domains is achieved. The surface structure of the resulting full coverage self-assembled monolayers is resolved with molecular resolution by STM. The ordered monolayer structure of ω-ferrocenylpropanethiol is discussed in comparison with its bulk crystal structure, derived from single crystal X-ray analysis. Based on these results a monolayer structure of ω-ferrocenylalkanethiols with longer alkyl chains closely related to the bulk crystal structure of the shorter alkyl-spacer derivates is suggested. Our results provide detailed insight into the self-assembly of FcCnSH on gold substrates.