Mn -Acetate Complexes Studied as Single Molecules.

The phenomenon of single molecule magnet (SMM) behavior of mixed valent Mn coordination clusters of general formula [Mn Mn O (RCOO) (H O) ] had been exemplified by bulk samples of the archetypal [Mn Mn O (CH COO) (H O) ] (4) molecule, and the molecular origin of the observed magnetic behavior has found support from extensive studies on the Mn system within crystalline material or on molecules attached to a variety of surfaces. Here we report the magnetic signature of the isolated cationic species [Mn O (CH COO) (CH CN)] (1) by gas phase X-ray Magnetic Circular Dichroism (XMCD) spectroscopy, and we find it closely resembling that of the corresponding bulk samples. Furthermore, we report broken symmetry DFT calculations of spin densities and single ion tensors of the isolated, optimized complexes [Mn O (CH COO) (CH CN)] (1), [Mn O (CH COO) ] (2), [Mn O (CH COO) (H O) ] (3), and the complex in bulk geometry [Mn Mn O (CH COO) (H O) ] (5).

Large orbital magnetic moments of small, free cobalt cluster ions Co[Formula: see text] with n [Formula: see text].

The size dependent electronic structure and separate spin and orbital magnetic moments of free Co[Formula: see text] ([Formula: see text]) cluster ions have been investigated by x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. A very large orbital magnetic moment of [Formula: see text] per atom was determined for Co[Formula: see text], which is one order of magnitude larger than in the bulk metal. Large orbital magnetic moments per atom of  ≈1 [Formula: see text] were also found for Co[Formula: see text], Co[Formula: see text], and Co[Formula: see text].

Soft X-ray Spectroscopy as a Probe for Gas-Phase Protein Structure: Electron Impact Ionization from Within.

Preservation of protein conformation upon transfer into the gas phase is key for structure determination of free single molecules, for example using X-ray free-electron lasers. In the gas phase, the helicity of melittin decreases strongly as the protein's protonation state increases. We demonstrate the sensitivity of soft X-ray spectroscopy to the gas-phase structure of melittin cations ([melittin+qH] , q=2-4) in a cryogenic linear radiofrequency ion trap.

Electronic ground states of Fe2(+) and Co2(+) as determined by x-ray absorption and x-ray magnetic circular dichroism spectroscopy.

The (6)Π electronic ground state of the Co2 (+) diatomic molecular cation has been assigned experimentally by x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap. Three candidates, (6)Φ, (8)Φ, and (8)Γ, for the electronic ground state of Fe2 (+) have been identified. These states carry sizable orbital angular momenta that disagree with theoretical predictions from multireference configuration interaction and density functional theory.