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The synthesis and crystal structure of the stable and water-soluble tantalum peroxo-lactate complex with acid (ammonium tetralactatodiperoxo-[mu]-oxo-ditantalate(V)), [(N[H.sub.4]).sub.4][T[a.sub.2][([C.sub.2][H.sub.4][O.sub.3]).sub.4][([O.sub.2]).sub.2]O].3[H.sub.2]O is presented. The solution of the tantalum complex was successfully applied for the synthesis of two photocatalytic materials, NaTa[O.sub.3] and S[r.sub.2]T[a.sub.2][O.sub.7].

The cis-dioxo-molybdenum(VI) complexes with new aliphatic dithiolene ligands and mono-oxo-molybdenum(IV) complexes are prepared and investigated. The oxygen atoms of the cis-Mo(super VI)O2 cores are relatively nucleophilic and hence these complexes are unstable in protic solvents and protonation might occur to produce Mo(super VI)O(OH), as observed with the oxidized state of arsenite oxidase.

Research has been conducted on the salts. Results indicate that the charge-transfer ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide charge-transfer salts containing FeBr (sub)4 (super)- and GaBr (sub)4 (super)- counteranions have been obtained as needle crystals with almost identical structures.

Research has been conducted on the carbonic anhydrase and carboxypeptidase A. The intrinsic recognition of carboxamides by zinc(II) in these carbonic anhydrase and carboxypeptidase A has been carried out via the synthesis of the zinc(II)-carboxamide-appended cyclen complexes (cyclen= 1,4,7,10-tetraazacyclododecane) and the results are reported.

Research has been conducted on the quasi-one-dimensional halogen-bridged Cu (super)II- Pt (super)IV mixed-metal complexes of the form [Cu(chxn) (sub)2][PtX (sub)2 (chxn) (sub)2]X (sub)4, where chxn= 1R,2R-diminocyclohexane and X is Cl or Br. The synthesis of these complexes has been carried out and the crystal structures of the compounds determined by the single-crystal X-ray diffraction have been investigated.

Results show that the titanium complex of the ammonium citratoperoxotitanate exhibits extraordinary stability against hydrolysis due to tight coordination of titanium in the molecule. The aqueous solution is stable over a broad range of pH.

The article discusses the synthesis of sterically hindered tris-pyridyl methane ligands. The mechanism for their hydroxylation in the reaction with CuBr (sub)2 in MeOH under air is analyzed.

The bleomycin mimic ligands L1 and L2 are synthesized and their pH-dependent complexations with Cu(II), Fe(II) and Zn(II) are investigated via pH-metric titrations. The protonation constants for both ligands show the considerable influence exerted by the carbamide group. The complexation of L1 with Cu(II) forms (Cu(II)(H(sub -1)L1H(super 1+)))2+ at pH < 5 and (Cu(II)(H(sub -1)L1))1+ at pH > 6. Meanwhile, L1 and Zn(II) give (Zn(II)L1)2+ at pH < 6 and (Zn(II)(H(sub 1-)L1))1+ at pH > 8. Finally, the complexation of L2 with Cu(II) yields (Cu(II)(H(sub -1)L2))1+.

Research has been conducted on ethylenedithiotetrathiafuvalenothioquinone- and dimethydimethylthio-1,3-diselenolemethides. The authors describe the use of these molecules in preparation of their charge-transfer salts with the magnetic FeBr (sub)4 (super)- counteranion.

The syntheses and crystal structures of two complexes (dimethylthio- (1).CuBr2 and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides (2).CuBr2) between 1 or 2 and CuBr2 and also on their electrical conducting and magnetic properties are reported. The results indicate that 1 and 2 indeed serve as electron donors capable of binding to one molecule of CuBr2, which can act as an oxidizing agent for 1 and 2 and also as a localized d spin source.

We previously reported on a 8-quinolinot-pendant cyclen (L5) as a Zn2+ fluorophore (cyclen = 1,4,7,10-tetra-azacyclododecane) and its caged derivative, 8-(benzenesultonyloxy)-5-(N,N-dimethylaminosulfonyt)quinolin-2- ylmethyl-pendant cyclen (BS-caged-L5), which can be reactivated by hydrolsis of benzenesulfonyl group upon complexation with Zn2+ at neutral pH to give a 1:1 Zn2+-L5 complex (Zn(H-1L5)). We report herein on the synthesis of 5,7-bis(N,N-dimethylaminosulfonyl)-8-hydroxyquinolin-2-ylmethyl-pendant cyclen (L6) and its caged dedvative (BS-caged-L6) for more sensitive and more efficient cell-membrane permeability than those of L5 and BS-caged-L5. B potentiomethc pH, ¹H NMR, and UV-vis spectroscopic titrations, the deprotonation constants pKa1-pKa6 of H5L6 were determined to be <2, <2, <2,2.5 ± 0.1 (for the 8-OH group of the quinotine moiety), 9.7 ± 0.1, and 10.8 ± 0.1 at 25 °C with / =0.1 (NaNO3). The results of ¹H NMR, potentiometric pH, UV-vis, and fluorescent titrations showed that L6 rapidly forms a 1:1 complex with Zn2+ (Zn(H-1L6)), the dissociation constant of which is 50 fM at pH 7.4. The fluorescent emission of Zn(H-1L5) at 478 nm is 32 times as large as that of L6 (excitation at 370 nm), and the fluorescent quantum yield of Zn(H-1L6) (ΦF = 0.41) is much greater than that of Zn(H-1L5) (ΦF = 0.044). The BS caged-L6 was reactivated by hydrolysis of the benzenesulfonyl moiety more rapidly (completes in 30 mm at pH 7.4 at 37 °C) than BS-caged-L5, presumably enabling the practical detection of Zn2+ in sample solutions and living cells. The photochemical deprotection of BS-caged-L6 and the cell membrane permeability of L6 and BS-caged-L6 are also described. [ABSTRACT FROM AUTHOR]

The structure of the Keggin-type β-[PW 12 O 40 ] 3- (PW 12 ) polyoxometalate, with n-Bu 4 N + as the countercation, has been determined for the first time by single-crystal X-ray analysis and compared to data obtained from a new determination of the structure of the α-PW 12 isomer, having the same countercation. Analysis of cyclic voltammograms obtained in CH 3 CN (0.1 M [n-Bu 4 N][PF 6 ]) reveals that the reversible potential for the β-PW 12 isomer always remains ca. 100 mV more positive than that of the α-PW 12 isomer on addition of the acid CF 3 SO 3 H. Simulations of the cyclic voltammetry as a function of acid concentration over the range 0-5 mM mimic experimental data exceptionally well. These simulation-experiment comparisons provide access to reversible potentials and acidity constants associated with α and β fully oxidized and one- and two-electron reduced systems and also explain how the two well-resolved one-electron W(VI)/W(V) processes converge into a single two-electron process if sufficient acid is present. 183 W NMR spectra of the oxidized forms of the PW 12 isomers are acid dependent and in the case of β-PW 12 imply that the bridging oxygens between the W I and W II units are preferentially protonated in acidic media. EPR data on frozen solutions of one-electron reduced β-[PW V W VI 11 O 40 ] 4- indicate that either the W I or the W III unit in β-PW 12 is reduced in the β-[PW VI 12 O 40 ] 3- /β-[PW V W VI 11 O 40 ] 4- process. In the absence of acid, reversible potentials obtained from the α- and β-isomers of PW 12 and [SiW 12 O 40 ] 4- exhibit a linear relationship with solvent properties such as Lewis acidity, acceptor number, and polarity index.