摘要:

The chemistry of metal phosphonates has been of increasing interest during the past two decades, owing to their practical applications as ion exchangers, catalysts and sensors. Great efforts have been devoted to the metal diphosphonates, by modifying the organic tether (R) of R(PO3H2)2, to explore new materials with large pores and interesting functions. The template effect on directing the formation of different metal diphosphonate structures, however, has not been well documented. We present here the syntheses and structures of eleven M-hedp compounds, where M = Cu, Fe, Ni; hedp = 1-hydroxyethylidenediphosphonate. The influences of templates on the final products are discussed.

ISSN:0260-3594    

DOI:10.1080/02603590008050866

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The papers which report on the crystal structures of the metal complexes containing anti-inflammatory drugs used to cure humans and other animals are critically reviewed and analyzed to search for the major structural-characteristics both for the coordination spheres and the ligand moieties. Even though this is not an exhaustive review, it appears that metal complexes of non-steroidal anti-inflammatory drugs (NSAID) only, have been reported thus far. The total number of compounds structurally characterized via diffraction techniques is small (ca. 20). Five of the complexes contain piroxicam (H2pir, see list of abbreviations) and almost fifteen of them are based on drugs from the carboxylic acid family: indomethacin (Hindo), tolmetin (Htol), naproxen (Hnap), diclofenac (Hdic) and aspirin (Hasp). The metals studied are also few in number, Cu(II) being the more frequently encountered; other metals are Cd(II), Pt(II) and Sn(IV). Some of the articles reviewed include the syntheses and the physico-chemical characterizations of other complexes whose molecular structures are inferred from spectroscopic techniques. Some complexes of H2pir with Fe(II), Co(II), Ni(II), and Zn(II) and a complex of ibuprofen (Hibu) with Cu(II) have been partially characterized in this way. The preponderance of Cu(II) complexes stems from the long-known anti-inflammatory superoxide dismutase (SOD) like activity shown by several Cu(II) inorganic and coordination compounds. [MII(Hpir)2(dmf)2] (M: Cu, Cd) are pseudo-octahedral neutral complexes of the monoanionic piroxicam (Hpir−) drug in the ZZZ conformation. The Cu(II) derivatives have a high oxygen radical scavenger activity as measured through the luminescence technique by using stimulated human neutrophils from healthy subjects. The peripheral parts of the complex molecules are mostly hydrophobic in character. The [PtIICl2(H2pir)L] (L: dmso, C2H4) complexes contain the neutral ligand molecule H2pir in the EZE conformation, coordinated through the pyridyl nitrogen atom only. The Pt-N linkage is greatly weakened by the high trans influence of the π-DMSO and π2-C2H4ligands. The molecular structure of the polymeric [SnIV(pir)(bu)2]ncompound has two n-bu groups and a doubly deprotonated tridentate pir2-ligand (ZZE) per Sn center. The donor atoms from pir2-are the enolate oxygen and the amidate nitrogen. The pyridyl nitrogen is also weakly bound to the SnIVatom. The amidic oxygen atom forms a weak link to the SnIVatom from a different coordination unit. The Pt and Sn compound are of potential anti-inflammatory and anti-tumor interest because of the presence of the piroxicam and of the PtCl2and Sn(bu)2reactive moieties. The complexes from the carboxylic acid family usually have the formula [CuII2L4L'2] (L: indo'; L': dmf, H2O, nmp, dma, dmso. L: tol−, nap−; L': dmso. L: dic−; L': ac, dmf) and [Cu2(asp)4], and are neutral binuclear molecules which show a high peripheral hydrophobicity. The indo−, tol−, nap−, dic−and asp−derivatives have a chemical inertness, at least as regards the [Cu2L4] coordination core, in some solution conditions (e.g. biological buffers, HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) and TES (N-tris(hydroxymethyl-2-aminoethanesulfonic acid)). The compounds can exert a SOD-like activity once the apical positions on Cu(II) are made free by dissociation of L'. Both the piroxicam and the carboxylic acid family molecule conformations have been analyzed (the metal-bound and the free forms). Molecular orbital investigations at semi-empirical levels have been initiated for some of the ligands in this article, with the aim of searching for fast and easily accessible ways to compute reliable conformations, charges and energetics; I hope that all laboratories will find these methods to be useful in subsequent analyses of drug-metal and drug-enzyme interactions.

ISSN:0260-3594    

DOI:10.1080/02603590008050867

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Current research efforts focus on using metal ions to bring organic molecules together and in so doing form structures that resemble large common materials, such as boxes, cages, grids, and channels. These metal-organic supramolecular structures are at the interface between molecular and macromolecular chemistry. As a contribution to this field of chemistry, we have focused on binding metal ions to cupped-shaped template molecules, which can be appended with functional groups. These resorcinarene-based molecules have four phenyl groups linked together into a ring and various functional groups attached to their upper rim. Some of the functional groups, bispyridylmethylamine (bpa) and iminodiacetic acid, are able to coordinate to metal ions. In the case of the bispyridylmethylamine resorcinarene, 2, a tetranuclear metal complex is formed when it is allowed to coordinate to copper(II). The copper centers surround the resorcinarene cavity and are not electronically coupled. In contrast to the Cu428+complex, when cobalt(II) or iron(II) are allowed to coordinate to an iminodiacetic acid resorcinarene, 3, two resorcinarenes are bought together. The M4328−(M = Co or Fe) complexes are tetranuclear metal(II) cage compounds that assemble in aqueous solutions above pH 4 and have a cavity. These molecules are capable of encapsulating a variety of organic guest molecules, for example, nonpolar hydrocarbons, substituted phenyls, alcohols, halogen containing hydrocarbons, and polar organic molecules. The cages act as NMR shift reagents and cause substantial up-field isotropic hydrogen shifts (−30 to −40 ppm for Co2+and −5 to −15 ppm for Fe2+) in the guest molecule and separation of the guest hydrogen chemical shifts. The solid state structures of Ba4[M432guest] (guest = 6 H2O, bromobenzene, or ethylbenzene) show bond angles independent of whether the metal ion is cobalt or iron, and bond lengths typical of metal oxygen and nitrogen bonds. The encapsulated guest does not noticeably effect the cavity dimensions, bond lengths, and bond angles.

ISSN:0260-3594    

DOI:10.1080/02603590008050868

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

One hallmark of supramolecular chemistry is the spatial organization of the individual components with respect to one another over nanoscopic distances. Frequently, coordination complexes play an important role in such systems, however, few are robust or inert enough to withstand a significant amount of physical or chemical manipulation. One exception is supramolecular structures constructed from enantiomerically pure [Ru(phenanthroline)3]2+complexes. When bridged by rigid, planar aromatic tpphz ligands (tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2″,3″j]phenazine), these complexes form robust, structurally rigid and well-defined, nanoscopic complexes. A series of enantiomerically and diastereomerically pure ruthenium(II) dimers, tetramers, hexamers, decamers and linear polymers have been prepared using a stereospecific synthetic strategy involving the coupling reaction between peripheral ortho-diamine and orthoquinone groups. These structures show spatial organization over nanoscopic distances with diameters ranging from 1.6 nm to over 5.0 nm. Due to the overall rigidity, the global structure of these molecules is easily modeled and shown to differ dramatically for different diastereomers. Most importantly, this system presents a synthetic approach to tailorable, robust and even chiral nanoscopic structures which exhibit unique physical properties and may serve as platforms for even larger mesoscopic architectures. Because of the unique kind stereoisomerism present in these topologically different diastereomers, the term atopomers is introduced to describe their stereochemistry. These structures also show a global chirality or chiral tertiary structure which is classified by the stereochemical descriptors P, M and T, as defined herein.

ISSN:0260-3594    

DOI:10.1080/02603590008050869

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Langmuir-Blodgett (LB) technique is a method of obtaining highly ordered thin films. The homogeneous nature of the surface and the large surface area per unit volume of this type of films are of key importance in the preparation of electronic gas sensors.

ISSN:0260-3594    

DOI:10.1080/02603590008050870

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Zeolites are widely used as adsorbents, catalysts, ion exchangers and molecular sieves. However, less is known about the potential use of zeolites and related microporous solids for tailored synthesis of advanced materials. Zeolite-based host-guest nanocomposites are a type of advanced material in which zeolites act as hosts for encapsulating and organizing molecules, crystalline nano-phases and supramolecular entities inside the zeolite pores. Space confinement and host-guest (electrostatic) interaction results in composite materials possessing novel optical, electronic and magnetic properties. Potential technological applications can be expected in a number of fields, such as chemical and biological sensing, semiconductor devices and photonics, to name only a few examples. A related aspect is the fine tuning of the intracrystalline space in zeolites for controlling intrazeolite chemical processes, including the conversion of zeolite cavities into chiral chambers which act as very selective catalysts for the asymmetric synthesis of fine chemicals. Developments in all of these fields critically depend upon improved methods for zeolite characterization and for studying intrazeolite chemistry. For both of these purposes many instrumental techniques are currently being used. Among them, IR spectroscopy deserves special attention. Recent advances in IR spectroscopy of zeolites include the use of variable temperature procedures, synchrotron IR radiation and ultrafast time-resolved IR spectrometry. Examples are given of how IR spectroscopy is strongly contributing to an improved understanding of zeolites and intrazeolite chemistry, which is needed in order to extend potential applications of zeolite-based materials.

ISSN:0260-3594    

DOI:10.1080/02603590008050871

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor