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| Dr. Raphael G. Rapti - Associate Professor |
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Ph.D., Texas A&M University, 1988.
Postdoctoral Fellow, Texas A&M University, 1989
Australian National University, 1990-91.
Email: raphael@adam.uprr.pr
Phone: 787-764-0000 ext. 2598
Fax: 787-756-8242
Field of Interest:
Inorganic Chemistry; Synthesis, Electrochemistry,
Spectro-Electrochemistry, X-Ray Crystallography,
Polynuclear Complexes, Metal-Metal Bonding, Metalloprotein
Models, Small Molecule Activation. |
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The
structure of Fe8(µ4-O)4(µ-pz)12Cl4.
We are involved in the study of Transition Metal pyrazolato complexes, employing pyrazole and substituted pyrazole ligands, which are either prepared in our laboratory or commercially available. Current projects include the synthesis, X-ray structural characterization and study of physicochemical properties of octanuclear Fe III -clusters (for an example, see Figure and 3D model in my hand in the photo), a trinuclear water-activating Cu-system, the supramolecular Chemistry of large 6- to 14-membered Cu-pyrazolato rings, and oligomeric Pd-, Ag-, and Au-complexes.
We have recently shown for the first time that
Fe/O-cubanes not only are redox-active, but their
electrochemistry rivals that of their better
known Fe/S-analogues. 4 We are currently
pursuing the structural, spectroscopic and magnetic
characterization of mixed-valent and substituted-pyrazole
derivatives of ferric/oxo-cubanes contained in
octanuclear Fe-pyrazolato clusters, anticipating
the discovery of Fe 4 O 4 active
centers in electron-transfer proteins. At the
same time we are pursuing two additional related
objectives: the development of octanuclear iron
clusters as MRI contrast enhansing agents, and
the use of such robust molecules as building
blocks for the synthesis of redox-active cluster-of-clusters
assemblies. Some related Mn 8 O 4 -clusters
are also being studied.
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A
trinuclear Cu II -pyrazolato complex
forms a rigid 9-membered (Cu-N-N) 3 frame
on which water molecules are twice deprotonated
to an oxide. 3 The pH-dependent reversible
conversion of Cu 3 (µ 3 -O),
Cu 3 (µ 3 -OH), and
Cu 3 (µ 3 -X) 2 ,
is accompanied by an orderly change from antiferro-
to ferromagnetic exchange among the three Cu-atoms.
The magnetic susceptibility and ESR studies in
various solvents are pointing to similarities
between those complexes and the trinuclear active-centers
of the particulate methane monooxygenase (pMMO).
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Small-ring
opening reactions have led to the characterization
of a series of spectacular [Cu(µ-OH)(µ-pz)] n -rings,
n = 6, 8, 9, 12, and 14 so far, which exhibit
size-recognition properties. Aggregates composed
of three or four of those neutral metallacycles
encapsulate anions, such as Cl - ,
CO 3 2- , SO 4 2- .
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Palladium pyrazolato monomers
PdX 2 (pz*H) 2 are convenient
building blocks for the synthesis of larger
homonuclear and heteronuclear complexes. Among
our recent products there is a homoleptic Pd 3 ( µ -3-Ph-pz) 6 complex
of D 3 -symmetry. 2
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In search of oligomeric complexes
showing argentophilic and aurophilic interactions,
we have prepared some new oligonuclear Ag-
and Au-pyrazolates. Recent synthetic efforts
have yielded a novel tetrameric [Au(µ-3,5- t Bu 2 -pz)] 4 complex
and a silver dimer-of-trimers complex with a
characteristic Raman band at 85 cm -1 assigned
to a short unsupported Ag-Ag interaction of 3.000 Å.
Selected Publications:
Gellert Mezei; Marlyn Rivera-Carillo; Raphael
G. Raptis, Dalton Trans. 2007, 37-40, "Trigonal
prismatic CuII6-pyrazolato cages: Structural
and electrochemical study, evidence of charge-delocalisation". Guang Yang; Raphael G. Raptis, Inorg. Chim.
Acta 2007, 360, 2503-2506, "Synthesis and
crystal structure of tetrameric silver(I) 3,5-di-tert-butyl-pyrazole".
Gellert Mezei; Raphael G. Raptis; Joshua Telser, Inorg.
Chem. 2006, 45, 8841-8843, "Trinuclear, Antiferromagnetically
Coupled CuII Complexes with an EPR Spectrum of
Mononuclear CuII: Effect of Alcoholic Solvents".
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