Showing papers by "Jan Reedijk published in 1991"

Reactivity of chloro- and aqua(diethylenetriamine)platinum(II) ions with glutathione, S-methylglutathione, and guanosine 5'-monophosphate in relation to the antitumor activity and toxicity of platinum complexes

Abstract: The reactivity of the two platinum(II) complexes [Pt(dien)Cl] + and [Pt(dien)(H 2 O)] 2+ with glutathione (GSH), S-methylglutathione (GS-Me), and guanosine 5'-monophosphate (5'-GMP) has been investigated and compared The reactions of GSH and GS-Me with the two platinum complexes are second order, ie with a direct nucleophilic attack by the entering ligand on the platinum

Interactions of Platinum Amine Compounds with Sulfur-Containing Biomolecules and Dna Fragments

Abstract: Publisher Summary This chapter presents a discussion on the interactions of platinum amine biomolecules and DNA fragments compounds with sulfur-containing biomolecules and DNA fragments. From the past, cis-diamminedichloroplatinum(II) has emerged as the classic compound in the context of antitumor drug therapy. Because it is generally accepted that binding of the compound to DNA is a major requirement for its biological activity, scientists have focused their attention especially on platinum-DNA interactions. The chapter discusses the latest results concerning these interactions. The chapter focuses on the reactions of this and related platinum compounds with S-containing biomolecules. Such interactions are considered to have an overall inhibitory effect on the drug action and are, therefore, of considerable importance. Besides cis-Pt other platinum compounds have been synthesized and tested for antitumor activity, obtaining higher solubility, better antitumor activity, and lower toxicity. The synthesis of most of these platinum compounds is largely governed by two empirical rules, concerning the trans-labilizing power of the coordinated ligands and the difference in platinum-ligand bond strength. Because platinum is a class B metal, it should be expected that platinum compounds show relatively high affinity for nitrogen donor sites in DNA—that is, the nucleobases rather than for the phosphate-deoxyribose moiety.

pH control of the photophysical properties of ruthenium complexes containing 3-(pyrazin-2-yl)-1,2,4-triazole ligands

Abstract: A new series of (Ru(bpy){sub 2}(L))(PF{sub 6}){sub 2} complexes, where bpy = 2,2{prime}-bipyridine and L = 3-(pyrazin-2-yl)-1,2,4-triazole (HLO), 1-methyl-3-(pyrazin-2-yl)-1,2,4-triazole (L1), 1-methyl-5-(pyrazin-2-yl)-1,2,4-triazole (L2), and 3-methyl-5-(pyrazin-2-yl)-1,2,4-triazole (HO3), have been prepared and characterized. {sup 1}H NMR spectroscopy has been used to analyze the coordination modes of the ligands, while UV-vis absorption, emission, and resonance Raman spectroscopies, together with electrochemistry, have been used to study the properties of the complexes in their ground and excited states. Electrochemical data and resonance Raman experiments show that in the compounds containing protonated or N-methyl-substituted pyrazinyltriazole ligands the lowest {pi}* levels are pyrazinyltriazole based, while for the complexes with deprotonated ligands the lowest {pi}* levels are located on the bpy ligands. Furthermore, the emission data (lifetimes and maxima) suggest that the emitting states can be changed from bpy to pyrazinyltriazole based upon lowering the pH for (Ru(bpy){sub 2}(L0)){sup +} and (Ru(bpy){sub 2}(L3)){sup +}. Another interesting feature is that the absorption and emission maxima of (Ru(bpy){sub 2}(L0)){sup +} and (Ru(bpy){sub 2}(L3)){sup +}. Another interesting feature is that the absorption and emission maxima of (Ru(bpy){sub 2}(L0)){sup +} and (Ru(bpy){sub 2}(L3)){sup +} do not change to a large extent when the pH is lowered. 39 refs., 8 figs., 4 tabs.

Mononuclear and dinuclear osmium(II) compounds containing 2,2'-bipyridine and 3,5-bis(pyridin-2-yl)-1,2,4-triazole: synthesis, electrochemistry, absorption spectra, and luminescence properties

Abstract: The synthesis, structure, electrochemical behavior, absorption spectra, luminescence spectra (from 90 to 298 K), luminescence lifetimes (from 90 to 298 K), and photoreactivity of the complexes Os(bpy){sub 2}(bpt){sup +} (1) and (Os(bpy){sub 2}){sub 2}(bpt){sup 3+} (2), where by = 2,2{prime}-bipyridine and Hbpt = 3,5-bis(pyridin-2-yl)-1,2,4-triazole, are reported. The properties exhibited by 1 and 2 are compared with those of Os(bpy){sub 3}{sup 2+} and of the analogous Ru(II) complexes. For both 1 and 2, the lowest energy absorption band and the luminescence band are attributed to Os {yields} bpy metal-to-ligand charge-transfer (MLCT) singlet and triplet excited states, respectively. Electrochemical oxidation is centered on the metal(s), and electrochemical reduction is centered on the ligands, with bpy being reduced at less negative potentials than bpt{sup {minus}}. Because of the stronger {sigma}-donor ability of bpt{sup {minus}} compared with bpy, the Os {yields} bpy CT absorption and emission bands of 1 are red-shifted compared with those of the parent Os(bpy){sub 3}{sup 2+} complex. In nitrile rigid matrix at 90 K, the emission lifetimes are 250 and 340 ns for 1 and 2, respectively. For both complexes, increasing temperature causes a decrease of the emission lifetime but the ln (1/{tau}) vs 1/T plots between 90 and 298more » K do not exhibit the highly activated decay processes characteristic of the {sup 3}MLCT {yields} {sup 3}MC crossover. In agreement with this result, no photodecomposition was observed in CH{sub 2}Cl{sub 2} solutions containing Cl{sup {minus}} ions.« less

Reaction products of [Pt(ethylenediamine)(dimethyl sulfoxide)Cl]Cl and [Pt(ethylenediamine)Cl2] with d(GpG) and 5'GMP. Unambiguous evidence for stable 1:1 intermediate N7 adducts with coordinated dimethyl sulfoxide

Abstract: The reactions of [Pt(en)(Me 2 SO)Cl]Cl, [Pt(en)(Me 2 SO)(D 2 O)](NO 3 ) 2 , [Pt(en)Cl 2 ], and [Pt(en)(D 2 O) 2 ](NO 3 ) 2 with d(GpG) and with 5'GMP have been investigated by 1 H magnetic resonance spectroscopy (en=ethylenediamine; Me 2 SO=dimethyl sulfoxide). [Pt(en)(Me 2 SO)X] (X=D 2 O, Cl − ) and 5'GMP form an intermediate product [Pt(en)(Me 2 SO)(5'GMP-N7)], which consists of two rotamers the interconversion of which is slow on the NMR time scale at 294 K

Effect of co-ordination mode on the physical properties of pyrazinyltriazole ligands bound to bis(2,2′-bipyridyl)ruthenium(II)

Abstract: The physical properties of the two co-ordination isomers of the bis(2,2′-bipyridyl)ruthenium(II) complex of 3-(pyrazin-2-yl)-1,2,4-triazole have been studied. In particular the acid–base properties have been analysed with respect to the nature of the ligand and the co-ordination mode of the triazole ring. The ground-state pKa(acid) values of 3.1 and 5.3 obtained for the N2 and N4 isomers respectively indicate that the N2 site of the triazole ring is a stronger σ donor than is the N4 atom. The excited-state pKa values obtained for deprotonation of the triazole ring are unusual and support earlier suggestions that in the compounds containing the neutral pyrazinyltriazole ligands the lowest π* level is based on the pyrazinyltriazole ligand, while for the deprotonated ligands this level is 2,2′-bipyridine based.

Structure of aquadibromobis(1,2,4‐triazolo[1,5‐a]pyrimidine‐N3)copper(II), a one‐dimensional alternating copper(II)⋯ oxygen array

Abstract: C 10 H 10 Br 2 CuN 8 O cristallise dans Pccn avec a=8,886, b=15,025, c=11,928 A, Z=4; affinement jusqu'a R=0,024. La maille contient deux molecules de 1,2,4-triazolo [1,5-a] pyrimidine, coordinees par N3 a un ion de cuivre(II), a deux ions bromure et a une molecule d'eau completant une forme bipyramidale rhomboedrique autour du cuivre. Tous les atomes N4 du coordinat non liant de chaque molecule sont impliques dans une liaison hydrogene avec le coordinat eau de la molecule suivante la plus proche

The first report of the isolation and characterisation of an intermediate formed upon photolysis of a ruthenium(II) diimine compound, in which one of the chelating ligands is bound in a monodentate fashion

Abstract: The isolation and characterisation of an intermediate produced upon photolysis of [Ru(bipy)2(L–L′)](PF6)2 in MeCN [bipy = 2,2′-bipyridyl and L–L′= 4-methyl-3-(pyridin-2-yl)-1,2,4-triazole], in which L-L′ is coordinated to the metal centre in a monodentate fashion, via the nitrogen of the triazole ring, is reported; this photochemically induced reaction can be reversed thermally.

Reaction of symmetrically and asymmetrically substituted derivatives of cisplatin with r(ApG). Influence of the nonleaving groups on structures and kinetics

Abstract: Reactions between symmetrically and asymmetrically substituted cis-platinum amine compounds with the dinucleotide r(ApG) have been studied. The symmetric cis-platinum amine compounds (general formulae cis-PtCl 2 (LL) 2 , L=NH 3 , alkylamine, also LL=ethylenediamine gave only one A-N7−G-N7 adduct as a major reaction product. On the other hand, the asymmetrically substituted compounds (general formulae cis-PtCl 2 (LL') 2 , L=NH 3 , L'=alkylamine, also LL'=N,N-dimethylethylenediamine) gave two products as detected and separated by HPLC

Synthesis and characterisation of trinuclear ru, os and ru/os mixed-metal complexes with a novel bridging pyridyltriazole ligand

Abstract: A novel bridging ligand 1,3,5-tris(5-(pyridin-2'-yl)-1,2,4-triazol-3-yl) benzene (H 3 tpb) has been synthesised and used to prepare the deprotonated trinuclear [(Ru(bpy) 2 ) 3 tpb] (PF 6 ) 3 («Ru 3 ») and [(Os(bpy) 2 ) 3 tpb] (PF 6 ) 3 («Os 3 »), as well as the deprotonated heterotrinuclear ([(Ru(bpy) 2 ) 2 (Os(bpy) 2 ) tpb] (PF 6 ) 3 ('Ru 2 Os') and [(Ru(bpy) 2 ) (Os(bpy) 2 ) 2 tpb] (PF 6 ) 3 ('RuOs 2 ') complexes (bpy=2,2'-bipyridine). The three pyridyltriazole rings of the bridging ligand can be protonated and deprotonated in these complexes, depending on the pH