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Journal ArticleDOI

ORTEP-3 for Windows - a version of ORTEP-III with a Graphical User Interface (GUI)

01 Oct 1997-Journal of Applied Crystallography (International Union of Crystallography)-Vol. 30, Iss: 5, pp 565-565
TL;DR: L Lists of software presented and~or reviewed in the Journal of Applied Crystallography are available on the World Wide Web at the above address, together with information about the availability of the software where this is known.
Abstract: Computer Program Abstracts The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and significant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr Commission on Crystallographic Computing. It should not exceed 500 words in length and should follow the standard format given on page 189 of the June 1985 issue of the Journal [J. Appl. CrysL (1985). 18, 189190] and on the World Wide Web at http://www.iucr. ac. uk/journals/jac/software/. Lists of software presented and~or reviewed in the Journal of Applied Crystallography are available on the World Wide Web at the above address, together with information about the availability of the software where this is known. J. App/. CrysL (1997). 30, 565 ORTEP-3 for Windows a version of ORTEP-III with a Graphical User Interface (GUI)
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Journal ArticleDOI
TL;DR: Fluorescence, mass spectrometry and (1)H NMR experiments reveal that the mechanism of anion-induced fluorescence revival involves either displacement of pendant coordination or complete removal of the Hg(II) from the macrocycle, depending on the anion.
Abstract: A cyclam-based fluorescent sensor featuring a novel triazole pendant arm has been synthesised using click chemistry. The sensor is highly responsive to both Cu(II) and Hg(II) in neutral aqueous solution and displays excellent selectivity in the presence of various competing metal ions in 50-fold excess. The addition of specific anions such as I(-) and S(2)O(3)(2-) causes a complete revival of fluorescence only in the case of Hg(II), providing a simple and effective method for distinguishing solutions containing Cu(II), Hg(II) or a mixture of both ions, even in doped seawater samples. X-ray crystal structures of both the Hg(II) sensor complex and a model Cu(II) complex show that pendant triazole coordination occurs through the central nitrogen atom (N2), providing to the best of our knowledge the first reported examples of this unusual coordination mode in macrocycles. Fluorescence, mass spectrometry and (1)H NMR experiments reveal that the mechanism of anion-induced fluorescence revival involves either displacement of pendant coordination or complete removal of the Hg(II) from the macrocycle, depending on the anion.

66 citations

Journal ArticleDOI
TL;DR: In this article, an octahedral iron(II) complex with the formula FeL(CNpy)2·0.25CNpy (1) was investigated using temperature-dependent susceptibility measurements (SQUID) and Mossbauer spectroscopy.
Abstract: The reaction of the Schiff-base like ligand H2L [L2– = (E,E)-({diethyl 2,2′-[1,2-phenylenebis(iminomethylidyne)]bis(3-oxobutanato)})] with iron(II) acetate in methanol in the presence of 4-cyanopyridine leads to the formation of an octahedral iron(II) complex with the formula FeL(CNpy)2·0.25CNpy (1). The magnetic properties of this complex were investigated using temperature-dependent susceptibility measurements (SQUID) and Mossbauer spectroscopy. Both measurements indicate that the complex performs a stepwise spin transition with a large plateau in the region from 225 K to 125 K and γHS ≈ 0.25. The molecule structure of the compound was determined at room temperature, 240 K (γHS ≈ 0.5 according to susceptibility measurements) and 100 K. Two complex molecules were found in the asymmetric unit with strong π–π interactions between the phenylene rings of H2L. In agreement with outcomes from the magnetic measurements, both iron centres are in the high-spin state at room temperature and in the low-spin state at 100 K. At 240 K one of the two iron centres is high-spin and the other one low-spin. The reason for the wide step with one fourth of the iron centres in the high-spin state is the additional distorted 4-cyanopyridine in the crystal that influences the transition temperature of the surrounding iron centres. The spin transition was followed in solution by using 1H NMR spectroscopy. A gradual spin transition with T1/2 = 238 K is obtained. Temperature-dependent diffuse reflectivity spectra show the occurrence of photoconversion at the surface of the sample but only about 6 % of the complex could be switched in bulk condition using a SQUID magnetometer and the stability of the photoinduced HS state with TLIESST = 40 K is very weak. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

66 citations

Journal ArticleDOI
TL;DR: Both mtpO-HmtpO metal complexes show very low resistance factors against an A2780 cell line, which has acquired resistance to cisplatin and for the first time, prototropic exchange is observed between the two heterocyclic ligands.
Abstract: Palladium and platinum complexes with HmtpO (where HmtpO = 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine, an analogue of the natural ocurring nucleobase hypoxanthine) of the types [M(dmba)(PPh3)(HmtpO)]ClO4 [dmba = N,C-chelating 2-(dimethylaminomethyl)phenyl; M = Pd or Pt], [Pd(N−N)(C6F5)(HmtpO)]ClO4 [N-N = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy), or N,N,N′,N′-tetramethylethylenediamine (tmeda)] and cis-[M(C6F5)2(HmtpO)2] (M = Pd or Pt) (head-to-head atropisomer in the solid state) have been obtained. Pd(II) and Pt(II) complexes with the anion of HmtpO of the types [Pd(tmeda)(C6F5)(mtpO)], [Pd(dmba)(µ-mtpO)]2, and [NBu4]2[M(C6F5)2(µ-mtpO)]2 (M = Pd or Pt) have been prepared starting from the corresponding hydroxometal complexes. Complexes containing simultaneously both the neutral HmtpO ligand and the anionic mtpO of the type [NBu4][M(C6F5)2(HmtpO)(mtpO)] (M = Pd or Pt) have been also obtained. In these mtpO−HmtpO metal complexes, for the first time, prototropic exchange...

66 citations

Journal ArticleDOI
TL;DR: In this article, proton transfer equilibria in chloroform solution of twelve 2-phenacylquinolines were studied by 1H, 13C and 15N NMR spectroscopies.
Abstract: Proton-transfer equilibria in chloroform solution of twelve 2-phenacylquinolines were studied by 1H, 13C and 15N NMR spectroscopies. The (Z)-enaminone form stabilized by an intramolecular hydrogen bond was found to prevail in all cases. Electron-donating substituents in the phenacyl part of the molecule lead to an increase of the ketimine form (to 33% for p-NMe2). Variable temperature 1H NMR measurements show that higher temperatures have the same effect. The negative logarithm values of the equilibrium constant, pKT, were found to be linearly dependent on Hammett σ substituent constants. The pKTvs. temperature correlation also has a linear character. In general, strong electron-withdrawing substituents cause transformation of the ketimine to the enaminone form to become more exothermic but values of the heat of reaction for 2-phenacylquinolines studied are not linearly dependent on σ. X-Ray data show that the strength of the internal hydrogen bond in the enaminone form increases for strong electron-withdrawing substituents. Rough estimation shows this bond to be stronger in chloroform solution than in the crystalline state. π-Electron delocalization in the six-membered quasi-ring involving the H⋯O bond is very strong. This effect is responsible for the predominance of the tautomeric enaminone form in 2-phenacylquinolines. On the other hand, semiempirical AM1 and PM3 calculations show that in the gas phase the ketimine tautomer is energetically favored in most cases.

66 citations

Journal ArticleDOI
TL;DR: A new, easily synthesized diphosphine based on a heterocyclic 1,3,2-diazaphospholidine framework has been prepared and calculations show that the homolytic cleavage of the P-P bond to form two phosphinyl radicals is favored over the diph phosphine by ~11 kJ/mol.
Abstract: A new, easily synthesized diphosphine based on a heterocyclic 1,3,2-diazaphospholidine framework has been prepared. Due to the large, sterically encumbering Dipp groups (Dipp = 2,6-diisopropylphenyl) on the heterocyclic ring, the diphosphine undergoes homolytic cleavage of the P–P bond in solution to form two phosphinyl radicals. The diphosphine has been reacted with O2, S8, Se, Te, and P4, giving products that involve insertion of elements between the P–P bond to yield the related phosphinic acid anhydride, sulfide/disulfide, selenide, telluride, and a butterfly-type perphospha-bicyclobutadiene structure with a trans,trans-geometry. All molecules have been characterized by multinuclear NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Variable-temperature EPR spectroscopy was utilized to study the nature of the phosphinyl radical in solution. Electronic structure calculations were performed on a number of systems from the parent diphosphine [H2P]2 to amino-substituted [(H2N)...

66 citations