The synthesis and characterization of a new ligand, tris((6-phenyl-2-pyridyl)methyl)amine (TPPA) and some of its copper complexes are described. The complexes [Cu(TPPA)]BPh (7) and [Cu(TPPA)(AN)](ClO& (8) (AN = acetonitrile) were prepared and their X-ray crystal structures and redox potentials were determined. The X-ray structure of 7 (triclinic space group, P1; a = 14.603(3), b = 15.137(3), c = 12.974(3) A, a = 91.76(3), p = 105.87(3), y = 117.00(3)", V = 2417.4( 12) A3, Z = 2) displays a copper(1) atom with a distorted trigonal pyramidal coordination sphere, but the X-ray structure of 8 (triclinic space group, Poi; a = 13.458(3), b = 13.586(3) c = 11.082(2) A, a = 113.00(3), p = 94.48(3), y = 90.53(3)", V = 1857.7(9) A3, Z = 2 ) indicates that the copper(I1) atom has the expected trigonal bipyramid geometry. The reduction potential of 8 in dimethylformamide, dimethylacetamide, acetonitrile, and isobutyronitrile is quite positive compared to [Cu(TPA)](ClO& (TPA = tris(2-pyridylmethy1)amine) under identical conditions. The various factors that may contribute to the difference in oxidation potential are discussed. The positive redox potential combined with steric factors accounts for the lack of reactivity of [Cu(TPPA)]PF6 with molecular 0 2 .

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A combination of host-guest chemistry and coordination chemistry in the design of electrochemical sensors for alkali metal and ammonium ions is described. The sensor molecules are coordination complexes between a copper ion and a functionalized tripodal ligand. Upon presentation of the ion to the sensor molecule, a shift in the redox potential of the copper ion occurs. In the course of the study, three new alkoxyphenyl-substituted derivatives of the ligand tris(2-pyridylmethyl)amine (TPA) were prepared and characterized. The synthesis of the new ligands involved the preparation of bromopyridyl-TPA derivatives followed by Suzuki coupling with substituted phenylboronic acids. Cyclic voltammetry studies of copper complexes of the ligands indicated that steric effects played a dominant role in the overall determination of the copper redox couple. Studies of the alkoxyphenyl ligands indicated that small but reproducible changes in the copper redox couple occurred upon presentation of a guest cation that would be expected to form a complex with the copper-ligand complex.

The structural characterization of Cu(1) and Cu(I1) complexes of tris(6-phenyl-2-pyridylmethyl)amine (tppa), a derivative of the known tris(2-pyridylmethy1)amine (tpa), was recently reported. The phenyl substituents in [Cu(tppa)AN](CIOJ, stabilize the Cu(1) state by 300-480 mV relative to [Cu(tpa)AN](CIO,),. Reported here is the synthesis of the compounds bis(2-pyridylmethyl)-6-phenyl-2-pyridylmethylamine (Phtpa) and bis(6-phenyl-2-pyridylmethyl)-2-pyridylmethylamine (Ph,tpa) and the synthesis and cyclic voltammetry studies of their Cu(I1) perchlorate complexes.The mechanism by whiCh the phenyl groups increase the redox potential was found to be solvent-dependent: in AN, the increase in potential is primarily due to reduced local dielectric: in IBN, DMF, and DMA, the steric interaction between coordinated solvent and the phenyl substituents becomes important. The redox behavior of these complexes is consistent with anticipated modes of binding of solvent molecules in the inner sphere of the Cu(I1) complexes.

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