摘要:

The chemistry of the most recent years of binary nitrogen-halogen species is discussed in four chapters. Chapter I focusses on nitrogen-fluorine compounds, including NF3N2F4N2F2and the NF4+N2F3+N2F+and NF2+cations. In Chapter II the trihalogeno nitrides NX3(X = Cl, Br, I) and the NCl4+cation are described and the likely existence of heavier analogues NBr4+and NI4+is discussed. Whereas all halogen azides XN3(X = F, Cl, Br, I) are summarized in Chapter III, the ionic nitrogen iodine species I2N2+I(N3)2+I2N3−and I(N3)2−are comprised in Chapter IV.

ISSN:0260-3594    

DOI:10.1080/02603599408035841

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The recent development of scanning tunneling microscopy (STM) and tunneling spectroscopy (TS) has allowed the electronic and atomic structure of interfaces to be probed with unprecedented spatial resolution. Although both STM and TS are now commonly used in investigations of metal and semiconductor surfaces, these techniques can also be applied in chemical investigations of molecular species and molecular films, frequently providing details of their orientation, density, and electronic properties. In this review, the instrumentation and fundamental principles underlying STM and TS are presented and recent examples of STM/TS investigations of molecular interfaces are described. Emphasis is placed on investigations of molecularly thin films of electroactive transition metal complexes, e.g., [(Ru(terpyridine))2(tetrapyridylpyrazine)]-(PF6)4and protoporphyrin(IX)-Fe(III)Cl, deposited on metal and graphite electrodes. In addition, studies of quasi-crystalline molecular films, silver halide films, and surface defects are also presented to demonstrate the broad range of chemical systems that can be explored by these techniques.

ISSN:0260-3594    

DOI:10.1080/02603599408035842

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Although vibronic Jahn-Teller interactions almost always cause both 4- and 6-coordinate copper(II) complexes to distort significantly away from regular tetrahedral and octahedral geometries, rather different factors influence the size and nature of the distortions. In the former case, the active mode is a bending vibration and this has a very small force constant which is often influenced by factors such as lattice interactions. The size of the distortion therefore varies widely from one compound to another, sometimes causing the limiting planar geometry to be reached. The very low energy of this bending vibration causes several unusual features to occur in the electronic spectrum of the planar CuCl42-ion. In particular, the significant temperature dependence of the band maxima and the vibrational fine structure observed at low temperature both imply that in the excited electronic states the complex has an equilibrium geometry distorted towards a tetrahedron. For 6-coordinate copper(II), the overall distortion is always rather large, but the fact that the active Jahn-Teller vibration is doubly degenerate, with discrimination between the components only occurring because of higher order effects, means that the geometry can vary from an elongated tetragonal to a compressed tetragonal octahedron relatively easily, the pathway involving orthorhombic intermediates. In this case, the alteration in geometry is accompanied by a change in the electronic ground state wavefunction. When the six ligands are identical, the elongated geometry is almost always more stable, with the unpaired electron in the dx2−y2orbital.

ISSN:0260-3594    

DOI:10.1080/02603599408035843

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0260-3594    

DOI:10.1080/02603599408035840

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor