Showing papers by "Jan Reedijk published in 2012"

Coordination polymers, metal-organic frameworks and the need for terminology guidelines

Abstract: Coordination polymers (CPs) and metal–organic frameworks (MOFs) are among the most prolific research areas of inorganic chemistry and crystal engineering in the last 15 years, and yet it still seems that consensus is lacking about what they really are, or are not.

Citation-based metrics are appropriate tools in journal assessment provided that they are accurate and used in an informed way

Abstract: In a reply to Jerome K. Vanclay's manuscript "Impact Factor: outdated artefact or stepping-stone to journal certification?" we discuss the value of journal metrics for the assessment of scientific-scholarly journals from a general bibliometric perspective, and from the point of view of creators of new journal metrics, journal editors and publishers. We conclude that citation-based indicators of journal performance are appropriate tools in journal assessment provided that they are accurate, and used with care and competence.

Fast and slow versus strong and weak metal-DNA binding: consequences for anti-cancer activity.

Abstract: The binding of transition metal compounds to nucleic acids is discussed in the perspectives of kinetics and their anticancer activity. Kinetics of ligand exchange is primarily determined by the intrinsic properties of the metal ions, and to a lesser degree by the ligands coordinated already to the metal ion. Metal compounds having ligand-exchange rates of the same order of magnitude as cell-division processes, e.g. many Pt(II), Ru(II) and Ru(III) compounds, are in use as chemotherapeutic drugs. Detailed knowledge of ligand exchange in such compounds is important for design of derivative and entirely new compounds. Metal coordination compounds of metal ions with much faster ligand-exchange reactions interact with DNA in a quite different way, namely primarily by compensation of negative charge of the polyanionic chain and are usually not active as anticancer agents. Examples of our recent work are presented in relation with experiments performed by others on new generations of platinum anti-cancer drugs.

Editorial: Citations and Ethics

Abstract: Once upon a time, citations were used to inform the reader of a scientific paper which earlier research papers had been used for the described research and for the writing of the actual paper. All references were stored in a database that could be searched manually by browsing the Science Citation Index from the Institute of Scientific Information (ISI). These references have been used by scientists to efficiently study earlier scientific literature on a given topic and to see their follow-ups (the snowball effect). Nowadays, literature citations in a paper may also have a strong strategic content, like mentioning certain papers, for example, of potential referees, or ignoring others. Indeed, citation habits have changed, as deduced from complaints that some scientists, for example, disproportionally cite more, or less, papers from the same or the other side of the Atlantic or Pacific Ocean. Mentioning just one reference followed by the sentence “and references cited therein” is not uncommon. Referee reports requesting to add one or more “specific” references are also regularly seen.

Mononuclear and dinuclear manganese compounds stabilized by supramolecular interactions

Abstract: New manganese compounds [Mn(HphpzMe)2(H2phpzMe)(HCO2)] (1), [Mn2(phpzMe)2(HphpzMe)2(OCH3)]·2CH3OH (2), Na{[Mn(HphpzPh)(phpzPh)(MeOH)2]2}(HCO2) (3), [Mn(HphpzPh)2(EtOH)2]ClO4·2EtOH (4) and [Mn(HphpzPh)2N3] (5) were synthesized and characterized with various techniques. 1, 4 and 5 are mononuclear manganese(III) compounds, 2 is a mixed-valence dinuclear manganese(III/IV) compound, and 3 is a trinuclear compound containing two manganese(III) ions and a sodium(I) ion. A remarkable feature is the spontaneous formation of the formate ion as a result of the methanol or methoxide oxidation in compounds 1 and 3. Using ethanol precludes the formation of the formate and compound 4 is obtained. The molecular structure of all compounds is stabilized by supramolecular interactions, including strong hydrogen bonding and π–π interactions.

2-Chloro-pyrimidin-4-amine.

Abstract: In the title pyrimidine derivative, C4H4ClN3, the 2-chloro and 4-amino substituents almost lie in the mean plane of the pyrimidine ring, with deviations of 0.003 (1) A for the Cl atom, and 0.020 (1) A for the N atom. In the crystal, molecules are linked via pairs of N—H⋯N hydrogen bonds, forming inversion dimers. These dimers are further linked via N—H⋯N hydrogen bonds, forming an undulating two-dimensional network lying parallel to (100).

Tetra-hedral zinc in tetra-kis-(1-methyl-1H-imidazole-κN)zinc bis-(tetra-fluorido-borate).

Abstract: In the title compound, [Zn(C4H6N2)4](BF4)2, the ZnII ion is in a slightly distorted tetra­hedral coordination geometry, with Zn—N distances in the range 1.980 (2)–1.991 (2) A. The tetra­hedral angles are in the range 104.93 (9)–118.81 (9)°.

Putting Anion—π Interactions into Perspective

Abstract: Supramolecular chemistry is a field of scientific exploration that probes the relationship between molecular structure and function. It is the chemistry of the noncovalent bond, which forms the basis of highly specific recognition, transport, and regulation events that actuate biological processes. The classic design principles of supramolecular chemistry include strong, directional interactions like hydrogen bonding, halogen bonding, and cation-π complexation, as well as less directional forces like ion pairing, π-π, solvophobic, and van der Waals potentials. In recent years, the anion-π interaction (an attractive force between an electron-deficient aromatic π system and an anion) has been recognized as a hitherto unexplored noncovalent bond, the nature of which has been interpreted through both experimental and theoretical investigations. The design of selective anion receptors and channels based on this interaction represent important advances in the field of supramolecular chemistry. The objectives of this Review are 1) to discuss current thinking on the nature of this interaction, 2) to survey key experimental work in which anion-π bonding is demonstrated, and 3) to provide insights into the directional nature of anion-π contact in X-ray crystal structures.

Copper perchlorate and tetrafluoridoborate compounds with the ligand 1,4,5-triazanaphthalene. Gradual transformation of mononuclear Cu(II) compounds via polynuclear mixed-valence Cu(II)/Cu(I) species to dinuclear Cu(I); syntheses, characterizations and X-ray structures

Abstract: When the ligand 1,4,5-triazanaphthalene (abbreviated as tan) is reacted with Cu(II) BF4− and ClO4− salts, a variety of mononuclear compounds has been found, all with the [Cu(tan)4] unit and varying amounts of weakly coordinating axial ligands and lattice solvents. Reproducible compounds formed include two purple compounds, analyzing as [Cu(tan)4](ClO4)2(CH3OH)2(H2O) (1) and [Cu(tan)4](BF4)2(CH3OH)1.5(H2O) (3), and two blue compounds, analyzing as [Cu(tan)4](ClO4)2(H2O)2 (2) and [Cu(tan)4]2(BF4)2(H2O)2 (4). Upon standing at room temperature, red-coloured, mixed-valence dinuclear-based 3D coordination polymers are formed by conversion of the purple/blue products, of which [Cu2(tan)4]n(BF4)3n (5) and the isomorphic methanol–water adduct [Cu(tan)4]n(BF4)3n(CH3OH)n(H2O)5n (5A) are presented in this paper. In addition a fully reduced dinuclear Cu(I) compound of formula [Cu2(tan)3(ClO4)2] (7) has been observed, and structurally characterized, as a rare three-blade propeller structure, with a Cu–Cu distance of 2.504 A.

Bis{μ-2-[(4,6-bis{(2-hydroxy-5-methylphenyl)[(pyridin-2-yl)methyl]amino}-1,3,5-triazin-2-yl)[(pyridin-2-yl-κN)methyl]amino-κN]-4-methyl­phenolato-1:2κ2O:O}bis­[(nitrato-κ2O,O′)zinc]–acetonitrile–water (2/4/1)

Abstract: The title compound, [Zn2(C42H38N9O3)2(NO3)2]·2CH3CN·0.5H2O, is a bis-phenolate-bridged dinuclear ZnII complex. The asymmetric unit comprises half the zinc complex (the full complex is completed by the application of a centre of inversion), one acetonitrile solvent mol­ecule and a quarter of a water mol­ecule (located on a twofold axis with half-occupancy; H atoms were not located for this mol­ecule). Each triazine-based multidentate ligand uses a phenolate group to bridge ZnII ions, generating a Zn2O2 core. The ZnII ions are five-coordinate, with an additional long Zn—O contact [2.6465 (16) A], and include a semi-bidentate nitrate ion and a N,N′,O-tridentate mode of the ligand in the coordination sphere. Non-coordinating pyridine groups form intra­molecular O—H⋯N hydrogen bonds with phenol groups. As suggested by the short O⋯O donor–acceptor distances between the disordered water molecules and phenol O atoms, these groups also participate in hydrogen bonding.