Shin-Geol Kang

TEMPLATE SYNTHESIS, CRYSTAL STRUCTURE, AND SOLUTION BEHAVIOR OF A HEXAAZA MACROCYCLIC NICKEL(II) COMPLEX CONTAINING TWO N-AMINOETHYL PENDANT ARMS

Abstract A new nickel(II) complex of the 14-membered hexaaza macrocyclic ligand 1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane (L 1 ), in which two 2-aminoethyl pendant arms are attached to the bridgehead nitrogen atoms, has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the metal ion. The complex [NiL 1 ] 2+ has a square-planar coordination geometry in the solid state and in nitromethane; the pendant amino groups are not coordinated to the metal ion. The crystal structure of [Ni(H 2 L 1 )](ClO 4 ) 4 (H 2 L 1 =a protonated form of L 1 ) shows that the four secondary nitrogen atoms are coordinated to the nickel(II) ion with a 5-6-5-6 chelate ring sequence. The nickel(II) ion is located at the inversion center of the N 4 square. The complex [NiL 1 ] 2+ exists in aqueous solutions as a mixture of the square-planar and octahedral [NiL l (H 2 O) 2 ] 2+ species. The addition of HCl (0.1–3.0 M) to aqueous solutions of the complex increases the concentration of the square-planar species, in contrast to the case for [NiL 2 ] 2+ (L 2 =1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) and other related hexaaza and pentaaza macrocyclic complexes. On the other hand, the addition of NaOH to the solution of [NiL 1 ] 2+ or [NiL 2 ] 2+ increases the proportion of the octahedral species. Synthesis, characterization, and solution behavior of the nickel(II) complexes of L 1 are reported.

Synthesis and characterization of copper(II) and nickel(II) complexes of tetraaza macrocyclic ligands containing one C-nitromethyl or -aminomethyl pendant arm

Abstract The square-planar copper(II) complex [Cu(L2)]2+ L2 = 3,14-dimethyl-3-nitromethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosa-13-ene) containing one C-nitromethyl pendant arm was synthesized by the nucleophilic addition of deprotonated nitromethane to the diimine complex [Cu(L1)]2+ (L1 = 3,14-dimethyl-2,6,13,17-tetraazatricyclo-[16.4.0.07.12]docosa-2,13-diene). The copper(II) complex of L2 is relatively stable against the dissociation of the nitromethyl group even in basic acetonitrile solutions, in contrast to the corresponding nickel(II) complex. Reduction of the nitro group [M(L2]2+ (M = NiII (L3 = 3,14-dimethyl-3-amino-methyl-2,6,13,17-tetraazatricyclo[16.4.0.017.2]docosa-13-ene) or CuII) produced the square-pyramidal complex [Cu(L3)]2+ or the octahedral complex [Ni(L3) (H2O]2+ containing one C-aminomethyl group, which is coordinated to the metal ion. Synthesis and characterization of the complexes of L2 and L3, together with the effects of the pendant arms on their properties, are reported.

Synthesis and properties of a tetraaza macrocyclic ligand containing 2-pyridylmethyl pendant arms and its copper(II) and nickel(II) complexes: crystal structure of the copper(II) complex

Abstract A new functionalized macrocyclic ligand 2,13-bis(2′-pyridylmethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.118O712]docosane (L2) containing two 2-pyridylmethyl pendant arms has been prepared by the one-step reaction of 3,4-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.118O712]docosane (L1) with 2-(chloromethyl) pyridine. The octahedral complexes [NiL2](ClO4)2 and [CuL2](ClO4)2, in which two pyridyl groups are coordinated to the metal ion, have been prepared and characterized. The crystal structure of [CuL2](ClO4)2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral geometry. In concentrated HClO4 solutions, the coordinated pyridyl groups of [CuL2]2 are protonated and are removed from the coordination sphere. However, those of [NiL2]2 are not protonated but are coordinated to the metal ion even in 3.0 M HClO4. The macrocycle L2 reacts more slowly with copper(II) ion than does L1.

SYNTHESIS AND PROPERTIES OF A NEW TETRAAZA MACROCYCLIC LIGAND CONTAINING ONE N-ACETIC ACID PENDANT ARM AND ITS COPPER(II) AND NICKEL(II) COMPLEXES

Abstract A new monofunctionalized tetraaza macrocycle C-meso-5,16-dimethyl-2,6,13,17-tetraazatricylco-[16.4.0.07.12]docosane-2-acetic acid (HL2), in which one acetic acid group is appended, was prepared by the one-step reaction of the tetraaza macrocycle C-meso-3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07,12]docosane (L)1) with an excess of bromoacetic acid. The copper(II) and nickel(II) complexes of HL2 were synthesized and characterized. Two types of copper(II) complexes Cu(HL2)](ClO4)2·0.5H2O and [CuL2]ClO4·5H2O (L2 is a deprotonated form of HL2) can be isolated under acidic and basic conditions respectively. However, only one form of nickel(II) complex [NiL2(H2O)]ClO4 was isolated even under acidic conditions. The crystal structure of [Cu(Hl2)](ClO4)2·0.5H2O shows that the pendant acetic acid group is coordinated to the metal ion through the oxygen atom of the carbonyl unit; the complex has a somewhat distorted square-pyramidal coordination geometry. The acetic acid group in [Cu(Hl2)]2 is also coordinated to the metal ion in nitromethane, acetonitrile, and ≥ 0.5 M HClO4 aqueous solutions, but is deprotonated to produce [CuL2] even in pure water. The macrocycle HL2 reacts with copper(II) ions more slowly than L1. Crystal data of [Cu(HL2)](ClO4)2·0.5H2O: monoclinic, space group P21/n with a = 8.179(1), b = 21.485(4), c = 16.339(7) A , β = 91.78(1)° and Z = 4.

Synthesis, characterization and properties of new fully n-alkylated 14-membered tetraaza macrocycles and their copper(II) complexes

Abstract New fully N-alkylated 14-membered tetraaza macrocyles 3,14-dimethyl- 3,14-dimethyl-2,6,13,17-tetraethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.180.7.12]docosane (3) and 3,14-dimethyl-2,6,13,17-tetrakis(n-propyl)-2,6,13,17-tetraazatricyclo[16.4.01.180.7.12]docosane (4) have been prepared from direct reactions of 3,14-dimethyl-2,6,13,17-tetraazatricyclo [16.4.01.180.7.12]docosane (1) with appropriate alkyl bromides. The protonation constants of 3 and 4 were determined by a potentiometric method, and it was found that these ligands have a higher proton affinity than 1 and its tetra-N-methyl derivative (2). The new macrocyles react with the dehydrated copper(II) ion to form the stable complexes [Cu(L)]2+ ( L = 3 or 4 ) in an ethanol solution, but do not react with hydrated copper(II) or nickel(II) ions in the same solution. The effects of the N-alkyl groups on the protonation and complexation behaviours of the macrocycles and on the spectroscopic and redox properties of their copper(II) complexes are presented.

Synthesis and characterization of nickel(II) complexes of di-N-alkylated 14-membered tetraaza macrocycles containing cyclohexane rings via regioselective alkylation reaction

Square-planar nickel(II) complexes of new di- N -alkylated 14-membered tetraaza macrocycles 6,17-dimethyl (L 5 ),6,17-diethyl (L 6 ), and 6,17-bis(n-propyl) (L 7 ) derivatives of 3,14-dimethy1-2,6,13,17-tetraazatricyclo-[16,4,0 1.18 O, 7.12 ]docosane (L 1 ) have been prepared by one-step, regioselective reaction of [NiL 1 ] 2+ with RI (R  Me, Et, or n-Pc) in basic Me 2 SO solution. The nickel(II) complexes were characterized by 1 H and 13 C NMR spectroscopy and/or by single crystal X-ray crystallography. Crystal structures of [NiL 1 ] (ClO 4 ) 2 and the di- N -propyl derivative [NiL 7 ] (ClO 4 ) 2 show that the two complexes have normal square-planar coordination geometries with the nickel atoms lying on the N 4 planes; however, the NiN bond distances of the latter are about 0.03 A longer than those of the former. The electronic spectra, redox potentials and/or structures of the nickel(II) complexes are strongly affected by the presence of N- and C-substituents, but little affected by the nature of the N -alkyl groups.

Template synthesis of N-aminoethylated hexaaza macrobicyclic nickel(II) complexes containing one four-membered chelate ring

Abstract New nickel(II) complexes of the hexadentate macrobicycles 6-(2-aminoethyl)-1,3,6,9,11,14-hexaazabicyclo[12.3.1]octadecane (1), 6-(2-aminoethyl)-1,3,6,9,11,14-hexaazabicyclo[12.2.1]heptadecane (2), and 6-(2-aminoethyl)-1,3,6,9,11,15-hexaazabicyclo[13.3.1]nonadecane (3) have been prepared selectively by the metal template condensation of formaldehyde with tris(2-aminoethyl)amine and a triamine (1,4,8-triazaoctane, 1,4,7-triazaheptane, or 1,5,9-triazanonane). The complexes [Ni(L)]2+ (L=1, 2, or 3), in which one 2-aminoethyl pendant arm is coordinated to the metal ion, have distorted octahedral coordination geometry with a rarely observed four-membered chelate ring. They are extremely stable in neutral or basic aqueous solutions but are readily decomposed in acidic conditions. The decomposition rate of the complexes in HClO4 solutions is not affected significantly by the ring size of the macrobicyclic ligands. Synthesis and characterization of the nickel(II) complexes are reported, together with the crystal structure of [Ni(1)][ZnCl4].

Template synthesis of a new dinuclear nickel(II) complex of a bis(macrobicyclic) ligand

Abstract A one-pot condensation reaction of 1,4,8-triazaoctane, ethylenediamine and formaldehyde in the presence of nickel(II) produced a new dinuclear nickel(II) complex of a bis(macrobicyclic) ligand, [Ni2(D)](ClO4)4, in which two fully saturated hexaazamacrobicycles are linked together by an ethylene chain. Each macrobicyclic subunit of the complex contains one 1,3-diazacyclohexane ring and has a square-planar geometry with a 5—6—5—6 chelate ring sequence. The electronic spectra and electrochemical properties show that metal—metal interactions of the dinuclear complex are negligible.

Synthesis and properties of a mono-N-hydroxyethylated tetraaza macrocycle and its nickel(II) and copper(II) complexes

Abstract A new 14-membered tetraaza macrocycle 2-(2-hydroxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosane (L3), in which only one 2-hydroxyethyl pendant arm is appended, has been prepared by direct reaction of 3,4-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosane (L1) with 2-bromoethanol. Two nickel(II) complexes [NiL3](ClO4)2 and [Ni(L3–H)(H2O)]ClO4 (L3–H=a deprotonated form of L3) can be prepared under acidic and basic conditions, respectively. On the other hand, only one form of copper(II) complex [CuL3](ClO4)2 was isolated as a solid under acidic and basic conditions. In the complex [CuL3](ClO4)2, the hydroxyl group is involved in coordination. However, the hydroxyl group of [NiL3]2+ is not involved in coordination in the solid state and in nitromethane. The nickel(II) complex is deprotonated to form the octahedral complex [Ni(L3–H)(H2O)]+, in which the hydroxoalkyl group and the water molecule are coordinated to the metal ion, in basic aqueous solutions. In water and acetonitrile, the nickel(II) complex exists as a mixture of the square-planar [NiL3]2+ and octahedral [NiL3(S)]2+ or [NiL3(S)2]2+ (S=solvent molecule) species. Synthesis and properties of the mono-N-functionalized macrocycle L3 and its nickel(II) and copper(II) complexes are reported.

Selective protonation of a tetraaza macrocyclic copper(II) complex containing two N-acetate pendant arms: short hydrogen-bonded chain structure of the mono-protonated derivative

Abstract Two copper(II) complexes [Cu(H2L3)](ClO4)2 (1) and [Cu(HL3)]n(ClO4)n.nCH3CN (2), in which the pendant N-acetate groups of L3 (2,12-bis(2-carboxymethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14.4.01.18.07.12]docosane) are fully or partially protonated, have been prepared selectively. The complexes have an octahedral coordination polyhedron. The [Cu(HL3)]+ cations of 2 are linked together by strong intermolecular hydrogen bonding interactions (COH⋯OC) between the N-acetic acid and N-acetate pendant arms, forming an one-dimensional polymer; the acetic acid and acetate groups are also coordinated to the metal ion through the oxygen atoms of the carbonyl units. The complexes 1 and 2 are quite stable in the solid states or in non-aqueous solvents, such as nitromethane and N,N-dimethylformamide, but are readily deprotonated to produce [CuL3] in aqueous solutions.