NMR and theoretical investigations on the structures and dynamics of octahedral bis(chelate)dichloro V-III compounds isolated by an unusual reduction of non-oxo V-IV species
Φόρτωση...
Ημερομηνία
Συγγραφείς
Rikkou, M.
Manos, M.
Tolis, E.
Sigalas, M. P.
Kabanos, T. A.
Keramidas, A. D.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
American Chemical Society
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Inorg Chem
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
Reaction of the non-oxo V-IV species [(VCl2)-Cl-IV(L-OO)(2)] [L-OO = acetylacetonate (acac(-)) or benzoylacetonate (bzac(-))] with a chelate nitrogen-donor ligand L-NN in acetonitrile leads to the reduction of V-IV to V-III and the formation of the mononuclear V-III compounds of the general formula [(VCl2)-Cl-III(L-OO)(L-NN)] (L-OO and L-NN are acac(-) and bipy for 1; acac- and 5,5'-me(2)bipy for 2; acac- and 4,4'-tb(2)bipy for 3; acac(-) and phen for 4; bzac(-) and bipy for 5; bzac(-) and phen for 6). The reduction of the V-IV complexes was monitored by GC-MS and H-1 NMR spectroscopy. Both one- and two-dimensional (2D COSY and 2D EXSY) H-1 NMR techniques were used to assign the observed 1H NMR resonances of 1-6 in CD2Cl2 or CDCl3 solution. It appeared that in solution these V-III complexes form two isomers which are in equilibrium: cis-[(VCl2)-Cl-III(L-OO)(L-NN)] reversible arrow trans-[(VCl2)-Cl-III(L-OO)(L-NN)]. 2D EXSY cross-peaks were clearly observed between bipy- and acac-hydrogen atoms of the two geometrical isomers of 1-3 as well as between bipy and acac(-) protons of the cis isomer, indicating a dynamic process that corresponds to cis-trans isomerization and a cis-cis racemization. The thermodynamic and kinetic parameters of the equilibrium between these two isomers were calculated for compounds 1 and 2 by using variable temperature (VT) NMR data. Both cis-trans isomerization and cis-cis racemization processes probably proceed with an intramolecular twist mechanism involving a trigonal prismatic transition state. Density functional calculations (DFT) also indicated such a rearrangement mechanism.
Περιγραφή
Λέξεις-κλειδιά
effective core potentials, tris-chelate complexes, ray-absorption spectroscopy, nuclear magnetic-resonance, tunicate ascidia ceratodes, configurational rearrangements, molecular calculations, hydrogen-peroxide, DNA cleavage, blood-cells
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://000184264400028
http://pubs.acs.org/doi/pdfplus/10.1021/ic034221s
http://pubs.acs.org/doi/pdfplus/10.1021/ic034221s
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας