The first compounds with mixtures of deprotonateable amide and oxime donor groups that may act as tetradentate metal chelators were synthesized using the reagent N,N,N-triethyl-N-(propan-2-onyl oxime)ammonium chloride to add the oxime-containing arms to various amines with attached amides. This reagent avoids the complications due to competition between deprotonation of the oxime moiety and acid/base chemistry of the alkylation reaction. These compounds are based on either the simple "tripodal amine" framework, or on chiral, natural amino acid derivatives. The steric properties may be easily tuned by variation of the "R-groups" on the arms containing the functional groups.

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/aryl < amide < carboxylate < alcohol < pyridyl < oxime.

The crown-ether-functionalized Mn(III) salicylaldimine complexes and their alkali metal ion derivatives have been synthesized and structurally characterized, and their ability to transport zwitterionic molecules such as tryptophan and specific neurotransmitters such as serotonin and dopamine has been investigated. The complexes are effective in the efficient transport of host molecules between water compartments, across a bridging CHCl3 solution that serves as an artificial membrane.

The potentially pentadentate, chiral ligand N,N-bis(1-propan-2-onyl oxime)-L-methionine N'-methylamide (L-MABO) shows remarkable versatility in its coordination chemistry with Ni(II) and Zn(II). In the crystal structure of the ZnCl2 complex of L-MABO, the ligand coordinates to the metal only through its three nitrogen donor groups (one amine and two oximes), with two chloride anions completing the distorted trigonal bipyramidal coordination sphere. In the NiCl2 complex, the three nitrogen donors and the thioether sulfur coordinate, along with two chlorides. The crystal structure of the Ni(NO3)2 complex contains two independent molecules, one of which coordinates the three nitrogens, the thioether sulfur, and the amide oxygen of L-MABO in addition to one nitrate anion. The second molecule coordinates the three nitrogen donors, the amide oxygen, one nitrate anion, and a methanol molecule. Thus, in only three crystal structures, L-MABO demonstrates its ability to provide N3, N3S, N3O, and N3OS donor sets. The thioether-bound complexes are unusual in that they have a predominantly nitrogen environment with a nickel-thioether bond that is not constrained by surrounding donor groups in a macrocyclic or linear polydentate motif. Comparison of the thioether-coordinated and methanol-coordinated molecules in the Ni(NO3) salt of L-MABO demonstrate the effect of the thioether bond on the relative "hardness" of the nickel. The electronic absorption and circular dichroism spectra of the aqueous solutions of the nickel complexes are interpreted in terms of a "descent in symmetry" model based on successive C3v and Cs distortions from octahedral geometry. These ligand field spectra indicate that in aqueous solution all ligand groups except for the three nitrogens of L-MABO are displaced by water. In acetonitrile, the non-nitrogen donors in the nitrate salt may also be displaced, while the chlorides remain coordinated.

A new synthetic route to molecules that contain cofacially oriented, [Mo(2)O(5)](2+)-bridged bis(catecholate) dianions is described. This synthesis has been useful in the preparation of supermolecular molecules containing catechol-functionalized, metalated macrocyclic [M(II)(TAD(OH)(2))] (M = Co, Ni) and SALPHEN [M(II)(R(2)R'(2)SALPHEN(OH)(2))] (M = H(2), Mn, Fe, Co, Ni, Cu) ligands. Of the former, the (Bu(4)N)(2)[Mo(2)O(5)[Ni(TAD(O)(2))](2)] (7) complex has been structurally characterized. The complex crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 12.324(3) Å, b = 17.740(4) Å, c = 20.920(4) Å, alpha = 108.79(3) degrees, beta = 98.20(3) degrees, and gamma = 103.12(3) degrees. The nearly-planar macrocyclic ligands are essentially parallel, with a dihedral angle of 6.5(2) degrees. The Ni(1)--Ni(2) separation in the anion is 3.938 Å. The structure of (Bu(4)N)(2)[Mo(2)O(5)[Cu(EtO(2)H(2)SALPHEN(O)(2))](2)] (19) has also been determined. This complex crystallizes in the monoclinic space group P2(1)/c, with unit cell dimensions a = 20.821(4) Å, b = 23.133(5) Å, c = 20.056(4) Å, and beta = 117.71(3) degrees. The Cu(1)--Cu(2) separation is 4.110 Å, and the dihedral angle between SALPHEN "planes" is approximately 9.7(1) degrees. Analytical and spectroscopic properties are provided. Reactions of these molecules with oxidants and strongly coordinating ligands are presented. The ability of the Fe(II) and Co(II) analogues of 19 to bind ligands such as O(2)(-) or S(2)(-) and O(2), respectively, in the "pocket" of the complex is described, and the products have been characterized. The synthesis and characterization of the unique "mixed catecholate" complexes (Bu(4)N)(2)[Mo(2)O(5)(D(t)()BC)(M(II)((t)()Bu(4)SALPHEN(O)(2)))] (M = H(2), Fe, Co, Ni, Cu) is described, and comparisons between these latter systems and the bis(M(II)SALPHEN-catecholate) complexes are provided.