Showing papers by "Jan Reedijk published in 1990"

Reversibility of binding of cisplatin-methionine in proteins by diethyldithiocarbamate or thiourea: a study with model adducts

Abstract: Model adducts for platinum-protein binding, at cysteine and methionine sites, have been synthesized by starting from [PtCl(dien)]Cl, cis-Pt(NH 3 ) 2 Cl 2 , trans-Pt(NH 3 ) 2 Cl 2 , and [PtCl(NH 3 ) 3 ]Cl. Glutathione (GSH) and S-methylglutathione (GS-Me) were used to mimic the sulfur atoms in the proteins. At pH 11 both trans-Pt(NH 3 ) 2 Cl 2 and [PtCl(NH 3 ) 3 ]Cl form trans-Pt-(NH 3 ) 2 (GS) 2 upon reaction with 2 equiv of GS - . Only the intermediate [Pt(NH 3 ) 3 GS]Cl was found to be relatively stable. The Pt-cysteine type bonds in [Pt(dien)GS] + and in trans-Pt(NH 3 ) 2 (GS) 2 could not be reversed by sodium diethyldithiocarbamate (Na(ddtc)) and thiourea

Synthesis, structure, and properties of a trinuclear and a mononuclear nickel(II) complex of N,N'-dimethyl-N,N'-bis(.beta.-mercaptoethyl)ethylenediamine

Abstract: The N 2 S 2 ligand N,N'-dimethyl-N,N'-bis(β-mercaptoethyl)ethylenediamine, H 2 L, reacts with NiCl 2 •6H 2 O in methanol solution to yield a trinuclear species of stoichiometry [Ni 3 L 2 ]Cl 2 •2H 2 O. This compound crystallizes in the monoclinic space group P2 1 /n with a=19.917 (7) A, b=5.453 (3) A, c=13.508 (6) A, β=100.81 (4)°, and Z=2. The trinuclear unit consists of two pseudosquare-planar terminal NiN 2 S 2 environments arranged in a chair conformation about a central NiS 4 plane, with the central nickel occupying a crystallographic inversion center. A dihedral angle of 107.84 (7)° exists between nickel planes unrelated by symmetry. Ni-N distances are 1.938 (4) and 1.951 (3) A, Ni-S distances in the NiN 2 S 2 environment are 2.144 (1) and 2.160 (1) A, and Ni-S distances of the NiS 4 center are 2.219 (1) and 2.216 (1) A. The same lignad, under aprotic conditions, reacts with bis(acetylacetonato)nickel(II) to give a neutral mononuclear [NiL] unit with an NiN 2 S 2 chromophore. The trinuclear and mononuclear species are compared with respect to their syntheses and NMR and electronic absorption spectra

Ruthenium compounds containing pyridyltriazines with low-lying .pi.* orbitals

Abstract: The structures of the complexes have been characterized by using 1 H NMR spectroscopy. The two isolated geometrical isomers of [Ru(dmpt) 3 ] 2+ have slightly different electronic properties. The emission, resonance Raman, and electrochemical data show that the LUMO (lowest unoccupied molecular orbital) of all complexes has pyridyltriazine character. A correlation between the electrochemical and absorption/emission data has been observed

Acid–base chemistry of polypyridyl ruthenium compounds of (pyridin-2′-yl)-1,2,4-triazoles. X-Ray crystal structure of bis(2,2′-bipyridine)[3-methyl-5-(pyridin-2′-yl)-1,2,4-triazolato-N1]ruthenium hexafluorophosphate tetrahydrate

Abstract: The acid–base chemistry of the two co-ordination isomers of the complex of bis(2,2′-bipyridyl)-ruthenium(II)[Ru(bipy)2]2+ with 3-(pyridin-2′-yl)-1,2,4-triazole (HL1) and of the analogous compound with 3-methyl-5-(pyridin-2′-yl)-1,2,4-triazole (HL2) has been investigated. As expected the ligands act as stronger acids after binding to the Ru(bipy)2 moiety. The two co-ordination isomers of the HL1 compound show distinctly different pKa values of 4.07 ± 0.05 and 5.95 ± 0.05. Luminescence titrations and lifetime measurements indicate that both ligands are stronger acids in the excited state than in the ground state. This suggests that they act as spectator ligands and are not directly involved in the photophysical processes. The crystal structure of [Ru(bipy)2L2]PF6·4H2O has been determined by single-crystal X-ray diffraction. Crystal data: trigonal, space group P31 with a=b= 1 3.760(6), c= 30.503(9)A, α=β= 90.00, γ= 120.00°, and Z= 6. The refinement based on 4 288 unique reflections [I > 2σ(I)] yielded a R(R′) value of 0.036(0.049). The pyridyltriazole ligand is co-ordinated to ruthenium via the N1 atom of the triazolato ring. The Ru–N distances are between 2.050(5) and 2.086(4)A. Four water molecules have been located near the pyridyltriazole ligand, giving rise to an extended hydrogen-bridged, structure.

Characterization of products from chloro(diethylenetriamine)platinum(1+) chloride and S-adenosyl-L-homocysteine. Evidence for a pH-dependent migration of the platinum moiety from the sulfur atom to the amine group and vice versa

Abstract: The reaction of [PtCl(dien)]Cl with S-adenosyl-L-homocysteine (SAH) has been followed by 1 H and 195 Pt NMR. Three products are formed: the mononuclear complex [Pt(dien)SAH-S] 2+ , with platination of SAH at the sulfur atom, the mononuclear complex [Pt(dien)SAH-N] + , which has a Pt(dien) 2+ unit coordinated to the amine group of the homocysteine unit, and the dinuclear complex [{Pt(dien)} 2 SAH-S,N] 3+ , which contains a Pt(dien) 2+ unit coordinated to the sulfur atom as well as a Pt(dien) 2+ unit coordinated to the amine group of the cysteine group

Unusual behaviour of the thioether function of the ligand 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) towards transition-metal salts. X-Ray structures of a green and a red modification of [Cu(bddo)Cl2]

Abstract: Co-ordination compounds of the new ligand 1,8-bis(3,5-dimethyl-1 -pyrazolyl)-3,6-dithiaoctane (bddo) with MCl2(M = Fe, Mn, Ni, Co, Zn, Cu, or Cd), MBr2(M = Mn, Co, Ni, or Zn), Cu(BF4)2, and CuX (X = BF4, NCS, Cl, Br, or I) are described. The general formula for the divalent metal is [M(bddo)X2] and for copper(I), [Cu2(bddo)X2]. With CuCl2 two modifications were obtained. The green modification of [Cu(bddo)Cl2] crystallises in space group P21/n with a= 9.019(2), b= 28.671(5), c= 8.431(2)A, β= 113.65(2)°, R= 0.055, and R′= 0.066 for 1 578 unique reflections [I > 2σ(I)]. The compound consists of Cu(bddo)Cl2 units. The copper atom is co-ordinated by two pyrazole nitrogens and two chloride atoms, in trans positions, in a distorted square-planar geometry. The red modification of [Cu(bddo)Cl2] crystallises in space group Pbcn with a= 9.397(4), b= 15.093(4), c= 15.142(4)A, Z= 4, R= 0.069, and R′= 0.089 for 864 unique reflections [I > σ(I)]. This compound consists of CuCl2 units linked together by ligand molecules, thus forming chains with distinct C2 symmetry perpendicular to the chain axis. The copper atom is co-ordinated in a distorted-tetrahedral geometry by two pyrazole nitrogens and two chloride atoms in cis positions. The sulphur atoms do not participate in the co-ordination, although molecular-mechanics calculations show that the ligand bddo is not sterically hindered to form tetradentate mononuclear chelates, i.e. with a MN2S2 chromophore. The structures of the other divalent metal halides were established as being very similar to that of the red modification. For [Cu(bddo)(BF4)2] semi-co-ordination of one or both tetrafluoroborates is indicated by the i.r. spectrum. Solid-state 13C n.m.r. spectra of the copper(I) compounds indicate that the S atoms show significant shifts, suggesting co-ordination. In the thiocyanate and iodide compounds both thioether sulphurs co-ordinate in an identical manner, whereas in the chloride and bromide compounds they co-ordinate in a different manner.

Structure of trans-bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-N1,N']diaquamanganese(II) dibromide

Abstract: [Mn(C12H10N6)2(H2O)2]Br2, Mr = 727.28, orthorhombic, Pbca, a = 10.734 (6), b = 17.084 (0), c = 15.182 (6) angstrom, V = 2784 angstrom 3, Z = 4, D(x) = 1.734 g cm-3, lambda-(Mo K-alpha) = 0.71073 angstrom, mu = 33.23 cm-1, F(000) = 1450, T = 295 K, final R = 0.032 for 1493 reflections [I > 2-sigma(I)]. The title compound is the first reported mononuclear compound with the ligand 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole. The manganese ions, situated on an inversion centre, are coordinated by four nitrogen atoms with an N-Mn-N angle of 74.1 (1)-degrees and Mn-N distances of 2.188 (4) and 2.266 (4) angstrom. Two axial water molecules [Mn-O = 2.200 (4) angstrom] complete the coordination sphere of the metal, which is pseudo-octahedral. The two bromide ions are not coordinated but are involved in an extended hydrogen-bridging network with the water ligands and the amino group of the triazole.

Copper co-ordination compounds of a chelating imidazole?thioether ligand. The molecular structures of [1,3-bis(5-methyl-4-imidazolyl)-2-thiapropane]-bis(nitrato)copper(II) and bis[1,3-bis(5-methyl-4-imidazolyl)-2-thiapropane]-copper(II) bis(tetrafluoroborate)?ethanol(1/2)

Abstract: The synthesis and spectroscopic properties of copper compounds with the tridentate ligand 1,3-bis(5-methyl-4-imidazolyl)-2-thiapropane (L) are described. Two series of compounds have been obtained, one green and the other purple. The green series has general formula [Cu(L)X2], in which X = Cl–, Br–, NCS–, or NO3– and [Cu(L)Cl(BF4)]. In these compounds both the ligand and the anions are co-ordinated to the copper(II) ion. The purple series has general formula [Cu(L)2]Y2·nH2O, with Y = Cl–, Br–, NO3–, or BF4– and n= 0–3, and [Cu(L)2][NCS][NO3]·H2O, with only the ligands L co-ordinated to the copper(II) ion. In all compounds L acts as a tridentate ligand with the thioether sulphur and both imidazole nitrogens co-ordinating. The compound [Cu(L)(NO3)2](A) crystallizes in the monoclinic space group P21/n with a= 18.060(5)A, b= 7.063(4)A, c= 13.229(3)A, β= 104.13(3)°, for Z= 4. The R′ value is 0.032 for 1971 significant reflections. The copper(II) ion has a distorted square-pyramidal geometry with an equatorial N2S donor set, an equatorial oxygen, and an axial oxygen from the nitrate ions. The Cu–N distances are 1.94 A, Cu–S 2.37 A, and the distance of the copper ion to the equatorial oxygen is 1.99 A and to the axial oxygen 2.41 A. The compound [Cu(L)2][BF4]2·2C2H5OH (B) crystallizes in the monoclinic space group P21/c with a= 8.262(2), b= 9.609(3), c= 22.582(5)A, β= 100.04(2)°, for Z= 2. The R′ value is 0.09 for 2 149 independent reflections (including low-intensity reflections). The copper(II) ion has a distorted-octahedral geometry with four equatorial N-donors and two long-distance axial sulphur atoms. The Cu–N distances are 2.00 A, the Cu–S distances 2.79 A. Electrochemistry of the two series (1 : 1 and 1 : 2) of copper(II) compounds points to two distinct one-electron reductions in both cases. Only the first copper(II)–copper(I) redox change, which occurs at rather high positive potentials, is chemically reversible. The stability of the copper(II)–copper(I) couple both in the five-co-ordinate [Cu(L)X2]0/– and six-co-ordinate [Cu(L)2]2+/+ assemblies gives evidence for the relative flexibility and versatility of the tridentate ligand.

Conformational changes in a single- and double-stranded nonanucleotide upon complexation of a monofunctional platinum compound as studied by proton NMR, phosphorus-31 NMR and CD methods.

Abstract: The structure of the nonanucleotide d(T-C-T-C-G-T-C-T-C), after binding of a monofunctional platinum compound (PtCl(NH{sub 3}){sub 3})Cl to the N7 of the central guanine residue, is described. The observed conformational changes are limited to the central residues; the intramolecular interactions between dC(4) and dG(5) are reduced, and the sugar conformation of the platinated guanosine, dG(5), is changed from the S-type conformer toward an N-type conformer upon platination. When the complementary strand d(G-A-G-A-C-G-A-G-A) is added to the platinated nonanucleotide, a duplex is formed. The imino proton of the platinated G {times} C base pair is clearly observed in the {sup 1}H NMR spectrum at low temperatures. The melting temperature of the double-stranded nonanucleotide is reduced by 15-20{degree}C as a result of monofunctional platinum binding to dG(5). The conformation of this Pt(NH{sub 3}){sub 3}-DNA adduct is compared with the structure of a DNA fragment to which the antitumor agent cis-PtCl{sub 2}(NH{sub 3}){sub 2} is bound bifunctionally. The kinked structure, which is proposed for cis-Pt(NH{sub 3}){sub 2}-DNA, does not occur in the monofunctional-platinated nonanucleotide, although the double-helical structure as such is destabilized. 57 refs., 8 figs.m 2 tabs.

Synthesis, characterisation, reactivity, and X-ray structure of cis-carbonylchlorobis[1-methyl-3-(pyridin-2-yl)-1,2,4-triazole-N4N′]ruthenium hexafluorophosphate

Abstract: The compound [Ru(L–L′)2(CO)Cl]PF6[L–L′= 1-methyl-3-(pyridin-2-yl)-1,2,4-triazole] has been obtained in high yield from ruthenium trichloride and the pyridyltriazole ligand in dimethylformamide, as a mixture of co-ordination isomers. One of these isomers was obtained using crystallisation techniques and crystallises in the monoclinic space group P21/n with unit-cell parameters a= 11.085(1), b= 13.120(2), c= 16.108(2)A, β= 97.17(1)°, and Z= 4. The metal cation has a cis geometry for CO and Cl, and the triazole ring is bound to the ruthenium centre via its N4 nitrogen atom. The CO and Cl groups are trans to the triazole rings of the pyridyltriazole ligand. The average ruthenium nitrogen distance is 2.09 A. From this compound the species [Ru(L–L′)(CO)L]+ have been obtained, where L = NCS– or H–. All the compounds have been characterised by spectroscopic, electrochemical, and high-performance liquid chromatographic methods. The results, and in particular the high yield in which the title compound is obtained, strongly suggest that the pyridyltriazole ligand is a weaker π acceptor than 2,2′-bipyridyl.

Unusual isomerization reaction of a platinum-dinucleotide compound

Abstract: The reaction between a bifunctional platinum complex and nucleic acid base occurs via a two-step mechanism, and the first step is normally a preferential binding to the N7 site of a guanine. The present paper mainly describes results obtained about the second step, i.e., chelation after the first platinum binding. The reaction of [Pt,(R,R-dach)(OH 2 ) 2 ] 2+ with r(GpA) (abbreviations: R,R-dach, 1R,2R-cyclohexanediamine; r(GpA), guanylyl(3'-5')adenosine) results in interbase cross-linked compounds between the guanine and the adenine bases

Structure of trans-dibromobis(5,7-dimethyl-8H-[1,2,4]triazolo[1,5-a]pyrimidine)palladium(II) methanol solvate

Abstract: [PdBr 2 (C 7 H 8 N 4 ) 2 ]•CH 3 OH cristallise dans P1 avec a=9,153, b=8,858, c=8,317 A, α=123,54, β=92,25, γ= 109,31 o , Z=1; affinement jusqu'a R=0,035. Les deux coordinats triazolopyrimidine sont coordines au palladium via N(3) a une longueur de 2,015 A; les bromes sont coordines de facon trans a une longueur de 2,4196 A, ce qui est dans la gamme attendue pour ce type de complexe

Structure of hexa-μ-chloro-μ4-oxo-tetrakis[1,2-dimethylimidazolecopper(II)]

Abstract: [Cu 4 Cl 6 (O)(C 5 H 8 N 2 ) 4 ]•O, 25 H 2 O cristallise dans P2 1 /c avec a=22,582, b=11,829, c=16,114 A, β=128,46 o , z=4; affinement jusqu'a r=0,055. Le compose contient un atome d'oxygene central, coordonne tetraedriquement a quatre atomes de cuivre; ceux-ci sont pontes en paires par les six atomes de chlore. Le coordinat imidazole (dimethyl-1,2) complete, autour de chaque atome de cuivre, une coordination bipyramide-rhomboedrique. Des molecules d'eau sont dispersees dans le reseau sans etre liees au cuivre. La cohesion du cristal est determinee par des liaisons de Van der Waals et de faibles liaisons hydrogene