1,721,057 research outputs found
1,10-phenanthroline: a versatile building block for the construction of ligands for various purposes
No full textThis review will cover the developments in the chemistry of phenanthroline-based ligands in the last
10–15 years. 1,10-Phenanthroline (phen) is a classic ligand in coordination chemistry, which couples versatility
in metal ion binding with peculiar properties of its complexes. For instance, metal complexes with
phenanthroline can be featured by an intense luminescence or can interact with DNA in an intercalative
fashion inducing, in some cases, DNA cleavage. For this reason a number of phenanthroline-containing
ligands has been recently synthesized by inserting phenanthroline within open-chain or macrocyclic
backbone, in order to develop new molecular chemosensors for metal cations and anions, ionophores as
well as new intercalating agents for polynucleotides. Furthermore, phenanthroline is rigid and its insertion
within cyclic or acyclic structures can impart to the resulting ligand a high degree of pre-organization,
affording selective complexing agents. This review will discuss on the coordination, luminescence and
intercalating and/or DNA cleaving properties as well as on analytical applications of metal complexes
with phenanthroline-based ligands. Particular attention will be devoted to macrocyclic receptors or openchain
ligands that, beside the phenanthroline nitrogen atoms, contain other donor atoms able to interact
with the metal cations or anions
RECENT ADVANCES IN COMPUTATIONAL CHEMISTRY - VOL. 1 (RECENT ADVANCES IN DENSITY FUNCTIONAL METHODS) PART III
No full textSensing and activation of anionic species by polyamine-based metal complexes
No full textThe role of metal complexes with polyamine ligands in selective binding of anions and their possible use
as optical chemosensors or biologically relevant hydrolytic agents for anionic substrates will be discussed
on the basis of some study cases from the work of the authors, with particular emphasis on the cooperative
action of metal cation and polyamine receptor in both the processes of interaction and sensing/
activation
Probing biologically and environmentally important metal ions with fluorescent chemosensors: thermodynamic versus optical response selectivity in some study cases
No full textThe reciprocal influence of the thermodynamic (binding) selectivity and the sensing (optical response)
selectivity of fluorescent chemosensors in determining their efficiency in probing biologically and environmentally
important metal ions in real matrices will be discussed on the basis of some study cases
from the work of the authors
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Anisotropic exchange in dinuclear complexes with polyatomic bridges. Crystal and molecular structure and EPR spectra of (m-oxalato)-bis-(1,10 phenantroline) dicopper (II) dinitrate
No full textThe X-ray crystal structure of (oxalato)bis(l,lO-phenanthroline)dicopper(II) dinitrate was determined at room temperature.The crystals are triclinic, space group Pi, with a = 9.977 (6) A, b = 9.658 (6) A, c = 7.036 (3) A, (Y = 108.03 (4)O, 0 = 95.40(4)'. y = 90.22 (4)O, and Z = 2. The least-squares refinement of the structure led to a conventional R factor of 0.036.Single-crystal EPR spectra were recorded at X-band (9-GHz) frequency at 77 K. The measured zero-field splitting tensor wasfound to be largely misaligned from the g tensor, showing that exchange contributions to the anisotropic spinspin interactionare operative. The relative influences of the dipolar magnetic and the anisotropic exchange interactions in determining the zero-field splitting in oxalato-bridged copper(I1) dimers are discussed
Aquifer-type behaviour of Marnoso-Arenacea formation in Northern Apennines: evidences from hydrogeological monitoring and hydrochemical data
No full textZinc(II)-based fluorescent dyes: Luminescence modulation by phosphate anion binding
No full textThis review deals on the interaction of inorganic phosphate anions with zinc(II)-based luminescent dyes,
with particular attention to the effects on their emission spectra observed upon binding of these anions
to zinc(II). Interaction with phosphates induces different effects, including electron and charge transfer
processes as well as structural rearrangements of the complex structures, which can remarkably change
the photophysical properties of zinc(II)-based dyes. These effects have been exploited to develop luminescent
systems for the selective recognition of inorganic phosphates, which are discussed on the basis
of their structural architecture and mechanism involved in the sensing process triggered by the anion
binding at the metal centre(s)
Synthesis, Structure, and Physicochemical Properties of ((Ethylsulfanyl)porphyrazinato)cobalt(II). Metal-Ligand Bonds in Co(OESPz) and in Related Cobalt(II) Tetrapyrroles: Insigths from a Density Functional Study
No full textThe Co(OESPz) complex crystallizes in space group P21/n, with a = 10.260(5) Å, b = 22.650(5) Å, c = 16.720(5) Å, β = 91.680(5)°, and Z = 4 and forms, similarly to the isomorphous Mn(OESPz), solid-state extended one-dimensional aggregates where “ruffled” molecular units are held together by extra planar Co···S interactions. The complex, which contains a low-spin Co2+ (S = 1/2) ion, exhibits intermolecular ferromagnetic interactions (θ = 2.6 K, g = 2.44) propagated through a superexchange pathway by extra planar Co···S interactions, with a possible contribution of the π system. Co(OESPz) shows a Co−Np distance shorter than CoOEP and CoPc and a sensible electrochemical stabilization of the Co2+ vs Co3+ state. The bonding interactions between Co2+ and the macrocyclic ligands OMSPz2-, Pc2-, Pz2-, and P2- are analyzed in detail, within the density functional (DF) theory, to elucidate the effects of the ligand framework. It is concluded that the σ interactions, which are by far dominant in all members of the CoII tetrapyrrole series, in the aza-bridged complexes, particularly in CoPz and Co(OMSPz), are stronger than in CoP, due to the reduced “hole” size of the macrocycle. The π interactions, consisting of π back-donation from Co-3dπ into empty ring π orbitals and donation from the occupied ring π orbitals into the Co-4pz are rather weak, but there is a sizable contribution from polarization of the macrocyclic ligand. The aza bridges have little effect on the metal to ligand π back-donation which in Co(OMSPz) is completely absent; the peripheral substituents, which are responsible for large polarization effects, play a more relevant role in the metal−macrocycle π interactions. In all porphyrazines the total orbital interaction contribution (covalent component) prevails over the ionic component of the bond, the latter being identified as the sum of the Pauli repulsion and the attractive electrostatic interaction between Co2+ and the tetrapyrrole(2−)
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