Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S 4 (1) and mn13S 4 (2) and maleonitrile pentathiacrown ether mn15S 5 (3) and of their complexes with various metal salts (MX 2 , M --Pd, Pt, Ni, Co, Fe; X --Cl, CrCl 3 , Ni (BF 4 ESI has also been used to determine the binding constants for various complexes in solution. Absolute and relative binding energies of metal-containing complexes can be estimated on the basis of energy-variable collision-induced dissociation (CID) measurements. In this context, Brodbelt and co-workers studied the dissociation pattern of differently charged polyether, crown ether and polypyridyl transition metal complexes. 26,27 In general, these studies reveal that rearrangement reactions involving the loss of small neutrals from the large ligands or the loss of intact ligands from multi-ligand metal complexes are characteristic. [26][27][28][29][30] In the present paper we report on ESI-MS studies of complexes of the crown ethers mn12S 4 (1), mn13S 4 (2) and mn15S 5 (3) 24c (cf. Fig. 1) with first-row transition metals Cr(III), Fe(II), Co(II), Ni(II) and Cu(II) and second/third-row metals Pd(II), Pt(II), Cd(II) and the main group metal thallium. The CID spectra of these complexes were also examined to evaluate the stability of the different complex types. Finally, the fragmentation patterns of the present complexes were compared in order to correlate them with the diameter of the cations and their binding properties. EXPERIMENTAL SynthesesThe syntheses of crown ethers mn12S 4 (1), 24b mn13S 4 (2),

A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-a]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-a]quinoxalines.

In order to elucidate the nature of the interaction between metal complexes and DNA, use was made of short telomere single-stranded oligodeoxynucleotide (ODN) strand 5 0 -T