Scanning tunneling microscopy (STM) images of cobalt(II) phthalocyanine (CoPc), copper(II) phthalocyanine (CuPc), and mixtures of the two adsorbed on the Au(111) face are reported. Based upon the stability and ease of obtaining molecular images, CoPc appears to adsorb more strongly than CuPc on Au(111), but both species provide images showing submolecular structure. The mixed CoPc and CuPc films also provide high-quality images showing details of the internal structure of the metal phthalocyanine. A particularly exciting aspect of this work is the strong influence of the metal ion valence configuration on the observed tunneling images. Unlike CuPc, wherein the central metal appears as a hole in the molecular image, the cobalt atom in CoPc is the highest point (about 0.3 nm) in the molecular image. These data are interpreted as indicating that the Co(II) d 7 system has significant d-orbital character near the Fermi energy while the Cu(II) d 9 system does not. This interpretation is consistent with theoretical calculations that predict a large contribution of cobalt d-orbitals near the Fermi energy, and with inelastic electron tunneling spectra that show d-orbital-related bands within 1 eV of the Fermi energy. An intriguing aspect of this work is that it may be possible to chemically identify the different metal phthalocyanines simply by their appearance. This can be used to advantage in the study of surface diffusion, 2-d sublimation, and the surface thermodynamics and kinetics of adlayer formation. 7198

Scanning tunneling microscopy (STM) images of iron(II) phthalocyanine (FePc) and nickel(II) phthalocyanine (NiPc) adsorbed on the Au(111) surface are reported. Both species provide images showing submolecular structure. A particularly exciting aspect of this work is the strong influence of the metal ion valence configuration on the observed tunneling images. Unlike NiPc, wherein the central metal appears as a hole in the molecular image, the iron ion in FePc is the highest point (about 0.25 nm) in the molecular image. These data are interpreted as indicating that the Fe(II) d 6 system has significant d orbital character near the Fermi energy while the Ni(II) d 8 system does not. This interpretation is consistent with theoretical calculations that predict a large contribution of iron d orbitals near the Fermi energy. The results reported here are also fully consistent with our previous report of CoPc and CuPc d orbital dependent images. An intriguing aspect of this work is that it may be possible to chemically identify different metal complexes simply by their appearance. Metal-organic complex systems of this type may also be viewed as single molecular electronic structures with different parts of the same molecule behaving as insulator, conductor, or semiconductor.

A strong d-orbital dependence in the scanning tunneling microscopy image of metal phthalocyanines is demonstrated. Unlike copper phthalocyanine (CuPc) wherein the central metal appears as a hole in the molecular image, the cobalt atom in CoPc is the highest point (about 0.3 nm) in the molecular image. On the other hand, the benzene ring regions of CoPc and CuPc appear to have the same height. These data are consistent with theoretical calculations that predict a large contribution of cobalt d-orbitals near the Fermi energy. An intriguing aspect of this work is that it may be possible to chemically identify the different metal phthalocyanines simply by their appearance. This is demonstrated for the case of a mixed monolayer of CuPc and CoPc on Au(111).

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Context. Ices are present in comets and in the mantles of interstellar grains. Their chemical composition has been indirectly derived by observing molecules released in the gas phase, when comets approach the sun and when ice mantles are sublimated or destroyed, e.g. in the hot cores present in high-mass, star-forming regions. Comparison of these chemical compositions sheds light on the formation of comets and on the evolution of interstellar matter from the molecular cloud to a protoplanetary disk, and it shows, to first order, a good agreement between the cometary and interstellar abundances. However, a complex O-bearing organic molecule, ethylene glycol (CH 2 OH) 2 , seems to depart from this correlation because it was not easily detected in the interstellar medium (Sgr B2) although it proved to be rather abundant with respect to other O-bearing species in comet C/1995 O1 (Hale-Bopp). Ethylene glycol thus appears, together with the closely related molecules glycolaldehyde CH 2 OHCHO and ethanol CH 3 CH 2 OH, as a key species in the comparison of interstellar and cometary ices as well as in any discussion on the formation of cometary matter. Aims. It is important to measure the molecular abundances in various hot cores to see if the observed differences between the interstellar medium and the comets are general. We focus here on the analysis of ethylene glycol in the nearest and best studied hot core-like region, Orion-KL. Methods. We use ALMA interferometric data because high spatial resolution observations allow us to reduce the line confusion problem with respect to single-dish observations since different molecules are expected to exhibit different spatial distributions. Furthermore, a large spectral bandwidth is needed because many individual transitions are required to securely detect large organic molecules. Confusion and continuum subtraction are major issues and have been handled with care. Results. We have detected the aGg conformer of ethylene glycol in Orion-KL. The emission is compact and peaks towards the hot core close to the main continuum peak, about 2 to the south-west; this distribution is notably different from other O-bearing species. Assuming optically thin lines and local thermodynamic equilibrium, we derive a rotational temperature of 145 ± 30 K and a column density of 4.6 ± 0.8 × 10 15 cm −2 . The limit on the column density of the gGg conformer is five times lower.

Context. The submillimeter spectral domain has been extensively explored by the Herschel and Planck satellites and is now reachable from the ground with ALMA. A wealth of data, revealing cold dust thermal emission, is available for astronomical environments ranging from interstellar clouds, cold clumps, circumstellar envelops, and protoplanetary disks. The interpretation of these observations relies on the understanding and modeling of cold dust emission and on the knowledge of the dust optical properties. Aims. The aim of this work is to provide astronomers with a set of spectroscopic data of realistic interstellar dust analogues that can be used to interpret the observations. It pursues the experimental effort aimed at characterizing the spectroscopic properties of interstellar dust analogues at low temperature in the mid infrared (MIR) to millimeter spectral domain. Compared to previous studies, it extends the range of studied dust analogues in terms of composition and of structure of the material. Methods. Glassy silicates of mean composition (1-x)MgO -xSiO 2 with x = 0.35 (close to forsterite, Mg 2 SiO 4 ), 0.50 (close to enstatite, MgSiO 3 ) and 0.40 (close to Mg 1.5 SiO 3.5 or MgSiO 3 :Mg 2 SiO 4 = 50:50) were synthesized. The mass absorption coefficient (MAC) of the samples was measured in the spectral domain 30 -1000 µm for grain temperature in the range 300 K -10 K and at room temperature in the 5 -40 µm domain. Results. We find that the MAC of all samples varies with the grains temperature and that its spectral shape cannot be approximated by a single power law in λ −β . In the FIR/submm, and above 30K, the MAC value at a given wavelength increases with the temperature as thermally activated absorption processes appear. The studied materials exhibit different and complex behaviors at long wavelengths (λ ≥ 200 to 700 µm depending on the samples).These behaviors are attributed to the amorphous nature of dust and to the amount and nature of the defects within this amorphous structure. We do not observe MAC variations in the 10-30 K range. Above 20 µm, the measured MAC are much higher than the MAC calculated from interstellar silicate dust models indicating that the analogues measured in this study are more emissive than the silicates in cosmic dust models. Conclusions. The underestimated value of the MAC deduced from cosmic dust models in the FIR/submm has important astrophysical implications because masses are overestimated by the models. Moreover, constraints on elemental abundance of heavy elements in cosmic dust models are relaxed.

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Peptide bonds, as the molecular bridges that connect amino acids, are crucial to the formation of proteins. Searches and studies of molecules with embedded peptide-like bonds are thus important for the understanding of protein formation in space. Here we report the first tentative detection of propionamide (C 2 H 5 CONH 2 ), the largest peptidelike molecule detected in space toward Sagittarius B2(N1) at a position called N1E that is slightly offset from the continuum peak. New laboratory measurements of the propionamide spectrum were carried out in the 9-461 GHz range, which provide good opportunity to check directly for the transition frequencies of detected interstellar lines of propionamide. Our observing result indicates that propionamide emission comes from the warm, compact cores in Sagittarius B2, in which massive protostellars are forming. The column density of propionamide toward Sgr B2(N1E) was derived to be 1.5 × 10 16 cm −2 , which is three-fifths of that of acetamide, and one-nineteenth of that of formamide. This detection suggests that large peptide-like molecules can form and survive during star-forming process and may form more complex molecules in the interstellar medium (ISM). The detection of propionamide bodes well for the presence of polypeptides, as well as other complex prebiotic molecules in the ISM.