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The oxorhenium(V) complexes [Re (V)O(L A)Cl 2] bearing the (N-2-pyridylmethyl) of l-valine (HL A (1)), l-leucine (HL A (2)), and l-phenylalanine (HL A (3)) and [Re (V)O(L B)Cl] containing the {(N-2pyridylmethyl)-(N-(5-nitro-2-hydroxybenzyl)} of l-valine (H 2L B (1)), l-leucine (H 2L B (2)), and l-phenylalanine (H 2L B (3)) are presented in this article. The complexes are isolated in enantiomeric pure form examined from X-ray structure determination. The complexes are characterized by spectroscopic and electrochemical methods. The molecular structures observed in the solid state are grossly preserved in solution ( (1)H, (13)C, and circular dichroism spectra). Gas-phase geometry optimization and the electronic structures of [Re (V)O(L A (1))Cl 2], [Re (V)O(L A (2))Cl 2], and [Re (V)O(L B (2))Cl] have been investigated with the framework of density functional theory. The absorption and circular dichroism spectra of the complexes were also calculated applying time-dependent density functional theory (TDDFT) using the conductor-like polarizable continuum solvent model to understand the origin of the electronic excitations. The chemical shift ( (1)H and (13)C) as well as (1)H- (1)H spin-spin coupling constant were also computed by the gauge-independent atomic orbital method, and the computed values are consistent with the experimental data.

The Re(I) complexes [Re(HPAN)(CO)(3)Cl], 1, and [Re(2)(PAN)(2)(CO)(6)]·C(6)H(12), 2·C(6)H(12), have been prepared by reacting [Re(CO)(5)Cl] with HPAN. Here (PAN)(-) is the deprotonated form of 1-(2-pyridylazo)-2-naphthol. A subsequent reaction of [Re(HPAN)(CO)(3)(CF(3)SO(3))] with a chelating diphosphine ligand generates [Re(PAN)(CO)(P-P)]·CH(2)Cl(2), 3·CH(2)Cl(2). The structures of the complexes are determined by X-ray crystallography. The molecular structures observed in the solid state are retained in the solution ((1)H, (13)C and (31)P NMR and mass spectra). The photophysical and electrochemical properties are also investigated. The gas-phase geometry optimization and the electronic structures of [Re(HPAN)(CO)(3)Cl], [Re(2)(PAN)(2)(CO)(6)] and [Re(PAN)(CO)(P-P)] have been investigated with the framework of density functional theory. The absorption spectra of the complexes are calculated by time dependent density functional theory (TDDFT) using a conductor-like polarizable continuum model (CPCM). DFT calculation shows good agreement with the experimental ground state IR and NMR values. Excited state TDDFT calculations provide a better insight into the experimental luminescence spectra of all the complexes in solution.

Binuclear mixed valence oxovanadium(IV/v) complexes of general formula [V2O3L] containing a [OVIV(μ‐Ooxo)(μ‐Ophen)VVO]2+ core have been synthesised using conformationally labile N4O3‐coordinating heptadentate ligands (H3L). The X‐ray structure of one complex has been examined. Solution EPR spectra revealed that the unpaired electron of the complexes is delocalised between the two vanadium centres. The simulated EPR spectrum of one complex confirms this experimental observation. DFT studies have been performed using crystallographic coordinates in order to obtain further insight into the electronic structure of this type of molecule. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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