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1.
A new macropolycycle, 2,13-dimethyl-1,5,12,16-tetraazapentacyclo[14.6.2.25.12.06.11.017.22]hexacosane (L3), has been prepared by the reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.07.12]docosane (L1) with 1-bromo-2-chloroethane. The macropolycycle readily reacts with anhydrous copper(II) ion to yield [CuL3]2+ in dry methanol but does not with nickel(II) ion, showing a high copper(II) ion selectivity. Crystal structure of [CuL3](ClO4)2 shows that the complex has a distorted square-planar coordination polyhedron with a trans-IV type N-conformation. The Cu-N distances [1.989(3) and 2.015(3) Å] of [CuL3](ClO4)2 are distinctly shorter than those of [CuL1](ClO4)2 and other related macrocyclic copper(II) complexes. The d-d transition band for [CuL3](ClO4)2 is observed at 447 nm, which is ca. 40 nm shorter than that for [CuL1](ClO4)2.  相似文献   

2.
A 14-membered tetraaza macrocycle, 2,13-bis(2-carbomethoxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.1807.12]docosane (L2) bearing two N-CH2CH2COOMe groups, and its nickel(II) and copper(II) complexes have been prepared and characterized. The nickel(II) and copper(II) complexes of 2-(2-carbomethoxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.1807.12]docosane (L3) containing one N-CH2CH2COOMe group have also been prepared. The crystal structure of [NiL2](ClO4)2 shows that the complex has a slightly distorted trans-octahedral coordination geometry with two relatively short axial Ni-O (N-CH2CH2COOMe group) bonds (2.136(3) Å). In various solvents, however, a considerable proportion of [NiL2]2+ exists as a square-planar form, in which the functional pendant arms are not involved in coordination. The proportion of the square-planar isomer varies with solvents in the order of nitromethane ? acetonitrile < H2O < DMF ? DMSO. In the case of [CuL2](ClO4)2, only one N-CH2CH2COOMe group is involved in coordination. The N-CH2CH2COOMe group of [NiL3](ClO4)2 is not directly involved in coordination even in the solid state, though the functional group of [CuL3](ClO4)2 is coordinated to the metal ion.  相似文献   

3.
A di-N-functionalized 14-membered tetraaza macrocycle, [H4L3](ClO4)2 (L3 = 1,8-bis(2-carboxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane), has been synthesized by acid hydrolysis of 1,8-bis(2-cyanoethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L2). The copper(II) complexes [CuL2](ClO4)2 and [Cu(H2L3)](ClO4)2 were prepared and characterized. The complex [Cu(H2L3)]2+ readily reacts with methanol to yield [CuL4]2+ (L4 = 1,8-bis(2-carbomethoxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane). The N-CH2CH2COOH groups of [Cu(H2L3)](ClO4)2 are not coordinated to the metal ion in the solid state but are involved in coordination in various non-aqueous solvents or in aqueous solutions of pH ? 1.0. Interestingly, [CuL4](ClO4)2 exists as two stable structural isomers, 1 (the pendant ester groups are not involved in coordination) and 2 (one of the two ester groups is coordinated to the metal ion), in the solid state; the two isomers can be prepared selectively by controlling ionic strength of a methanol solution of the complex. Crystal structures and coordination behaviors of the two isomers are described. The di-N-cyanoethylated macrocyclic complex [CuL2](ClO4)2 is rapidly decomposed in 0.1 M NaOH solution even at room temperature. On the other hand, [Cu(H2L3)](ClO4)2 and [CuL4](ClO4)2 are quite inert against decomposition under similar basic conditions. In acidic or basic aqueous solutions, [CuL4]2+ is hydrolyzed to [Cu(H2L3)]2+ or [CuL3].  相似文献   

4.
New copper(II) complexes [CuL2]2+ (L2=7,7,9-trimethyl-1,3,6,10,13-pentaazabicyclo[11,2,11.13]hexadec-9-ene) and [Cu2(L3)(H2O)2]4+ have been prepared by the reaction of [CuL1]2+ (L1=5,5,7-trimethyl-1,4,8,11,14-pentaazatetradce-7-ene) and formaldehyde. The mononuclear complex [CuL2]2+ has a square-planar coordination geometry with a 5-6-5-6 chelate ring sequence and is relatively stable even in low pH at room temperature. The dinuclear complex [Cu2(L3)(H2O)2]4+ consists of two unsaturated 15-membered pentaaza macrocyclic units (7,7,9-trimethyl-1,3,6,10,13-pentaazacyclopentadec-9-ene) that are linked together by a methylene group in a tilted face-to-face arrangement [Cu?Cu distance: 7.413(2) Å ]. Each macrocyclic unit of [Cu2(L3)(H2O)2]4+ contains one four-membered chelate ring and has a severely distorted octahedral coordination polyhedron. The dinuclear complex is quite stable in aqueous solutions containing an excess of formaldehyde or in dry acetonitrile but is decomposed to [CuL1]2+ and [CuL2]2+ in pure water.  相似文献   

5.
The complexation of 3-, 4-, and 6-fluorosalicylic acids (HL) with copper(II) was investigated in aqueous solution by pH-potentiometry combined with UV-visible spectrophotometry, and in 50 v/v % water-methanol mixture by the two-dimensional ESR simulation method. Both methods showed the formation of [CuLH−1] and [CuL2H−2]2− of high stabilities, and, at low excess of ligand, the ESR-silent mixed hydroxido complex [Cu2L2H−3]. Further species were also identified by the two-dimensional ESR simulation method: [CuL]+ in the acidic region, the minor dimer [Cu2L2H−2], and the cis and the trans isomers for [CuL2H−2]2−. The position of the fluorine atom in the aromatic ring had significant effect on the coordination abilities of the ligands, in good correlation with their reported biological activities. It was 3-fluorosalicylic acid, which formed the most stable complexes [CuLH−1] and [CuL2H−2]2−, while the mononuclear complexes with 6-fluorosalicylic acid were found to be the least stable. For the other ligands (including 5-fluorosalicylic acid studied recently), complexes of medium stabilities were formed. For the interpretation of these findings, ab initio and semi-empirical quantum chemical calculations were carried out for the ligand molecules, isolated and surrounded by water molecules, respectively.  相似文献   

6.
Reaction of 5,6-dihydro-5,6-epoxy-1,10-phenanthroline (L) with Cu(ClO4)2·6H2O in methanol in 3:1 M ratio at room temperature yields light green [CuL3](ClO4)2·H2O (1). The X-ray crystal structure of the hemi acetonitrile solvate [CuL3](ClO4)2·0.5CH3CN has been determined which shows Jahn-Teller distortion in the CuN6 core present in the cation [CuL3]2+. Complex 1 gives an axial EPR spectrum in acetonitrile-toluene glass with g|| = 2.262 (A|| = 169 × 10−4 cm−1) and g = 2.069. The Cu(II/I) potential in 1 in CH2Cl2 at a glassy carbon electrode is 0.32 V versus NHE. This potential does not change with the addition of extra L in the medium implicating generation of a six-coordinate copper(I) species [CuL3]+ in solution. B3LYP/LanL2DZ calculations show that the six Cu-N bond distances in [CuL3]+ are 2.33, 2.25, 2.32, 2.25, 2.28 and 2.25 Å while the ideal Cu(I)-N bond length in a symmetric Cu(I)N6 moiety is estimated as 2.25 Å. Reaction of L with Cu(CH3CN)4ClO4 in dehydrated methanol at room temperature even in 4:1 M proportion yields [CuL2]ClO4 (2). Its 1H NMR spectrum indicates that the metal in [CuL2]+ is tetrahedral. The Cu(II/I) potential in 2 is found to be 0.68 V versus NHE in CH2Cl2 at a glassy carbon electrode. In presence of excess L, 2 yields the cyclic voltammogram of 1. From 1H NMR titration, the free energy of binding of L to [CuL2]+ to produce [CuL3]+ in CD2Cl2 at 298 K is estimated as −11.7 (±0.2) kJ mol−1.  相似文献   

7.
The acid-base properties and Cu(II), Ni(II), Ag(I) and Hg(II) binding abilities of PAMAM dendrimer, L, and of the simple model compounds, the tetraamides of EDTA and PDTA, L1, were studied in solution by pH-metric methods and by 1H NMR and UV-Vis spectroscopy. PAMAM is hexabasic and six pKa values have been determined and assigned. PAMAM forms five identifiable complexes with copper(II), [CuLH4]6+, [CuLH2]4+, [CuLH]3+, [CuL]2+ and [CuLH-1]+ in the pH range 2-11 and three with nickel(II), [NiLH]3+, [NiL]2+ and [NiLH-1]+ in the pH range 7-11. The complex [CuLH4]6+, which contains two tertiary nitrogen and three amide oxygen atoms coordinated to the metal ion, is less stable than the analogous EDTA and PDTA tetraamide complexes [CuL1]2+, which contain two tertiary nitrogen and four amide oxygen atoms, due to ring size and charge effects. With increasing pH, [CuLH4]6+ undergoes deprotonation of two coordinated amide groups to give [CuLH2]4+ with a concomitant change from O-amide to N-amidate coordination. Surprisingly and in contrast to the tetraamide complexes [CuL1]2+, these two deprotonation steps could not be separated. As expected the nickel(II) complexes are less stable than their copper(II) analogues. The tetra-N-methylamides of EDTA, L1(b), and PDTA form mononuclear and binuclear complexes with Hg(II). In the case of L1(b) these have stoichiometries HgL1(b)Cl2, [HgL1(b)H−2Cl2]2−, [Hg2L1(b)Cl2]2+, Hg2L1(b)H−2Cl2 and [Hg2L1(b)H−5Cl2]3−. Based on 1H NMR and pH-metric data the proposed structure for HgL1(b)Cl2, the main tetraamide ligand containing species in the pH range <3-6.5, contains L1(b) coordinated to the metal ion through the two tertiary nitrogens and two amide oxygens while the structure of [HgL1(b)H−2Cl2]2−, the main tetraamide ligand species at pH 7.5-9.0, contains the ligand similarly coordinated but through two amidate nitrogen atoms instead of amide oxygens. The proposed structure of [Hg2L1(b)Cl2]2+, a minor species at pH 3-6.5, also based on 1H NMR and pH-metric data, contains each Hg(II) coordinated to a tertiary amino nitrogen, two amide oxygens and a chloride ligand while that of [Hg2L1(b)H−5Cl2]3−, contains each Hg(II) coordinated to a tertiary amino nitrogen, two amidate nitrogens, a chloride and a hydroxo ligand in the case of one of the Hg(II) ions. The parent EDTA and PDTA amides only form mononuclear complexes. PAMAM also forms dinuclear as well as mononuclear complexes with mercury(II) and silver(I). In the pH range 3-11 six complexes with Hg(II) i.e. [HgLH4Cl2]4+, [HgLH3Cl2]3+, [Hg2LCl2]2+, [Hg2LH−1Cl2]+, [HgLH−1Cl2] and [HgLH−2Cl2]2− were identified and only two with Ag(I), [AgLH3]4+ and [Ag2L]2+. Based on stoichiometries, stability constant comparisons and 1H NMR data, structures are proposed for these species. Hence [HgLH4Cl2]4+ is proposed to have a similar structure to [CuLH4]6+ while [Hg2LCl2]2+has a similar structure to [Hg2L1(b)H−5Cl2]3−.  相似文献   

8.
Two bis(1-pyrazolyl)alkane ligands, bis(3,5-dimethyl-1-pyrazolyl)methane and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methane, and their copper(II) complexes, bis(3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL1(NO3)2] and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL2(NO3)2]·2H2O, were prepared. Physiochemical properties of the copper(II) complexes were studied by spectroscopic (UV–vis, IR, EPR) techniques and cyclic voltammetry. Spectroscopic analysis revealed a 1:1 stoichiometry of ligand:copper(II) ion and a bindentate coordination mode for the nitrate ions in both of the complexes. According to experimental and theoretical ab initio data, the copper(II) ion is located in an octahedral hexacoordinated environment. Both complexes were able to catalyze the dismutation of superoxide anion () (pH 7.5) and decomposition of H2O2 (pH 7.5) and peroxynitrite (pH 10.9). In addition, both complexes exhibited superoxide dismutase (SOD) like activity toward extracellular and intracellular reactive oxygen species produced by activated human neutrophils in whole blood. Thus, these complexes represent useful SOD mimetics with a broad range of antioxidant activity toward a variety of reactive oxidants.  相似文献   

9.
A potential tetradentate indolecarboxamide ligand, H4L3 is synthesized and investigated for its coordination abilities towards Ni(II) and Cu(II) ions. Two H4L3 ligands in their tetra-deprotonated form [L3]4−, were found to coordinate two metal centers resulting in the formation of [Ni2(L3)2]4− (5) and [Cu2(L3)2]4− (6) complexes. The crystal structure of 6 displays the formation of a dinuclear structure where two fully deprotonated ligands, [L3]4− hold two copper(II) ions together. Even more interesting is the fact that both deprotonated ligands, [L3]4− coordinate the copper ions in an identical and symmetrical fashion. The Na+ cations present in the complex 6 stitch together the dinuclear units resulting in the formation of a coordination chain polymer. Four sodium ions connect two dinuclear units via interacting with the Oamide groups. Further, Na+ cations were found to coordinate several DMF molecules; some of them are terminal and a few are bridging in nature. The solution state structure (determined by the NMR spectral analysis) of the diamagnetic complex 5 also supported the fact that two deprotonated ligands, coordinate two nickel ions in an identical and symmetrical fashion. Absorption spectral studies reveal that the solid-state square-planar geometry is retained in solution and both complexes do not show any tendency to coordinate potential axial ligands. The variable-temperature magnetic measurements and EPR spectra indicate spin-spin exchange between two copper centers in complex 6. The electrochemical results for both complexes show three irreversible oxidative responses that correspond to the oxidation of first and second metal ion followed by the ligand oxidation, respectively.  相似文献   

10.
Three new Mg(II) bis(pendant arm) macrocyclic Schiff-base complexes, [MgLn]2+(n=5, 6, 7), have been prepared via cyclocondensation of 2,6-diacetylpyridine with branched hexaamines and characterised spectroscopically. In addition, for [MgL5](ClO4)2 the crystal structure is reported. This is the first X-ray structural determination of an Mg(II) complex coordinated by seven nitrogen atoms. The ligands, L, are 15-, 16- and 17-membered pentaaza macrocycles having two 2-aminoethyl pendant arms [L5; 2,13-dimethyl-6,9-bis(aminoethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18), 2, 12, 14, 16-pentaene, L6; 2,14-dimethyl-6,10-bis(aminoethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19), 2, 13, 15, 17-pentaene and L7; 2,15-dimethyl-6,11-bis(aminoethyl)-3,6,11,14,20-pentaazabicyclo[14.3.1]eicosa-1(20),2,14,16,18-pentaene]. The crystal structure of [MgL5](ClO4)2, was determined by X-ray diffraction and showed that the complex cation that had formed consisted of a pentagonal bipyramidally coordinated Mg(II) ion. All complexes were characterised by IR, 1H NMR,13C NMR, COSY(H,H) and HETCOR(H,C) spectroscopy, and the data indicate that the structure is approximately pentagonal bipyramidal in each case. This structural assignment is also supported by ab initio HF-MO calculations made using the standard 3-21G* basis set.  相似文献   

11.
l-3-Phenylpropane-1,2-diamine (dapp) was prepared by a three-step synthesis based on l-phenylalanine and characterized, including determination of stability constants with M2+ ions (Ni, Cu, Zn, Cd). The reaction of L-3-phenylpropane-1,2-diamine as the [Cu(dapp)2]2+ complex ion with formaldehyde and nitroethane in basic solution yields the acyclic (5-methyl-5-nitro-1,9-diphenyl-3,7-diazanonane-1,9-diamine)copper(II) complex ion, [Cu(1)]2+, as the major product. In addition, small amounts of the macrocyclic complex ion (2,10-diphenyl-6,13-dimethyl-6,13-dinitro-1,4,8,11-tetraazacyclotetradecane)copper(II), [Cu(2)]2+, form. Reduction of the [Cu(1)]2+ ion with zinc in aqueous acid yields the acyclic polyamine 5-methyl-1,9-diphenyl-3,7-diazanonane-1,5,9-triamine (3), an analogue of the previously reported pentaamine 5-methyl-3,7-diazanonane-1,5,9-triamine. Using the bis(l-3-phenylpropane-1,2-diamine)palladium(II) as precursor and an excess of other reagents, the macrocyclization reaction to produce [Pd(2)]2+ proved more successful. Reduction and recomplexation to copper(II) allowed isolation of the 2,9-dibenzyl-6,13-diammonio-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane)copper(II) ion, [Cu(4H22+)]4+. The acyclic complex [Cu(1)]2+ promotes the hydrolytic cleavage of plasmid DNA modestly; a mechanism to support this observation is presented.  相似文献   

12.
A series of hexadentate ligands, H2Lm (m = 1−4), [1H-pyrrol-2-ylmethylene]{2-[2-(2-{[1H-pyrrol-2-ylmethylene]amino}phenoxy)ethoxy]phenyl}amine (H2L1), [1H-pyrrol-2-ylmethylene]{2-[4-(2-{[1H-pyrrol-2-ylmethylene]amino}phenoxy)butoxy]phenyl}amine (H2L2), [1H-pyrrol-2-ylmethylene][2-({2-[(2-{[1H-pyrrol-2-ylmethylene]amino}phenyl)thio]ethyl}thio)phenyl]amine (H2L3) and [1H-pyrrol-2-ylmethylene][2-({4-[(2-{[1H-pyrrol-2-lmethylene]amino}phenyl)thio]butyl}thio) phenyl]amine (H2L4) were prepared by condensation reaction of pyrrol-2-carboxaldehyde with {2-[2-(2-aminophenoxy)ethoxy]phenyl}amine, {2-[4-(2-aminophenoxy)butoxy]phenyl}amine, [2-({2-[(2-aminophenyl)thio]ethyl}thio)phenyl]amine and [2-({4-[(2-aminophenyl)thio]butyl}thio)phenyl]amine respectively. Reaction of these ligands with nickel(II) and copper(II) acetate gave complexes of the form MLm (m = 1−4), and the synthesized ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution states investigations show that the complexes are neutral. The molecular structures of NiL3 and CuL2, which have been determined by single crystal X-ray diffraction, indicate that the NiL3 complex has a distorted octahedral coordination environment around the metal while the CuL2 complex has a seesaw coordination geometry. DFT calculations were used to analyse the electronic structure and simulation of the electronic absorption spectrum of the CuL2 complex using TDDFT gives results that are consistent with the measured spectroscopic behavior of the complex. Cyclic voltammetry indicates that all copper complexes are electrochemically inactive but the nickel complexes with softer thioethers are more easily oxidized than their oxygen analogs.  相似文献   

13.
The copper(II) and nickel(II) complexes of three new 1,2-bis(1,4,7-triazacyclononane) ligands containing unsaturated four carbon bridging groups is studied by continuous variation UV-Vis spectroscopic and pH potentiometric equilibrium experiments. The cis-butene-2 (LC) linked ligand may form monomeric MN6-type complexes while the trans-butene-2 (LT) and butyne-2 (LY) ligands are prevented by their stereochemistry from forming monomeric complexes and form oligomeric complexes. It is determined that the stability of the CuLC2+ complex is not appreciably different from the oligomeric complexes of LT and LY. Single-crystal X-ray structure determinations are made on three square pyramidal Cu2L4+ complexes: [Cu2LCCl4] (1), [Cu2LYCl4] (2), and [Cu2LT(NO3)2(H2O)2](NO3)2 (3). The structure of [Ni2(LC)2](ClO4)4 · 2H2O (4) is a binuclear dimer that contains two nickel(II) ions sandwiched between two ligands, indicating that bis([9]aneN3) ligands with four linker atom chains may form either monomeric or oligomeric structures.  相似文献   

14.
The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L1 (5,7-dimethyl-3-(2′,3′,5′-tri-O-benzoyl-β-d-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L2 (5,7-dimethyl-3-β-d-ribofuranosyl-s-triazolo[4,3-a]pyrimidine) and L3 (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L1)](NO3)2, [Pd(bpy)(L1)](NO3)2, cis-Pd(L3)2Cl2, [Pd2(L3)2Cl4] · H2O, cis-Pd(L2)2Cl2 and [Pt3(L1)2Cl6] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd2(L3)2Cl4] · H2O complex was established by X-ray crystallography. The two L3 ligands are found in a head to tail orientation, with a Pd?Pd distance of 3.1254(17) Å. L1 coordinates to Pd(II) through N8 and N1 forming polymeric structures. L2 coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L2 does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond.  相似文献   

15.
The synthesis and characterisation of two dicopper(II) and two dinickel(II) macrocyclic complexes, [CuII2LPr] (10), [CuII2LBu] (11), [NiII2LPr] (12) and [NiII2LBu] (13), are reported. The two new Schiff-base macrocycles (LPr)4− and (LBu)4− are isolated as dimetallic complexes 10-13 by the [2+2] condensation of 5,5-dimethyl-1,9-diformyldipyrromethane (9) and 1,3-diaminopropane or 1,4-diaminobutane, respectively, using Cu2+ or Ni2+ template ions. Single crystal X-ray structure determinations carried out on 10-13 show that each metal atom is in a square planar N4 geometry, being bound to two deprotonated pyrrole nitrogen atoms of one dipyrromethane unit and to the two adjacent imine nitrogen atoms. NMR spectra obtained for the two dinickel(II) complexes 12 and 13 show that in CDCl3 solution they are highly symmetrical and diamagnetic.  相似文献   

16.
Two new copper(II) complexes of the ligand 1,2,4,5-tetrakis(1,4,7-triazacyclononan-1-ylmethyl)benzene (Ldur) have been synthesized and characterized by single crystal X-ray studies. The first, [Cu4Ldur2-OH)4]Cl2(PF6)2 · 8H2O (1), was isolated from a solution of Ldur and Cu2+ at pH 9. Under acidic conditions (pH 3), a polymeric complex, {[Cu4Ldur2-Cl)6](PF6)2 · 10H2O}n (2), crystallized from solution. In both complexes, each of the four triazacyclononane (tacn) rings of the Ldur ligand facially coordinate to separate metal centres. Pairs of Cu(II) centres are then doubly-bridged by hydroxo groups in 1, leading to tetranuclear complex cation units featuring pairs of isolated copper(II) dimers with Cu22-OH)2 cores folded at the O?O lines. Two forms of the tetranuclear units, featuring slightly different Cu22-OH)2 core geometries, are present in equal amounts within the crystal lattice. In complex 2, chloro bridging ligands link pairs of Cu(II) centres from neighbouring tetranuclear units, forming a 1D helical polymeric structure. Variable-temperature magnetic susceptibility measurements suggest that the hydroxo-bridged copper(II) centres within one of the tetranuclear units in 1 are weakly antiferromagnetically coupled (J = −27 cm−1), whilst those in the other interact ferromagnetically (J = +19 cm−1). Similar measurements indicate weak ferromagnetic coupling (J = +16 cm−1) for the chloro-bridged copper(II) centres in 2.  相似文献   

17.
A series of complexes with the general formula [Fe(L)2]2+, where L represents the tridentating 6-(N-3,5-dimethylpyrazolyl)2,2-bipyridine (L4); 6-(N-pyrazolyl-1-ylmethyl)-2,2-bipyridine (L5); and 6-(N-3,5-dimethylpyrazolyl-1-ylmethyl)-2,2-bipyridine (L6), were prepared and characterized. The room temperature solution magnetic susceptibility and redox properties of these compounds were investigated as a function of stepwise variation in the ligand structure. The Fe(III/II) couple was characterized by way of cyclic voltammetry using aprotic solvent conditions (acetonitrile) where each complex was observed to have reversible behavior. NMR methodology was used for measuring the magnetic susceptibilities where both [Fe(L4)2]2+ and Fe(L5)2]2+ exhibited diamagnetic low spin behavior; however, [Fe(L6)2]2+ measured a μeff of 4.1 Bohr-magnetons indicating spin equilibrium predominantly in the high spin state.  相似文献   

18.
A dicyanamide bridged 2D polynuclear complex of copper(II) having molecular formula [Cu2(L)(μ1,5-dca)2]n (1) has been synthesized using the Schiff base ligand N,N′-bis(salicylidene)-1,3-diaminopentane, (H2L) and sodium dicyanamide (dca). The complex presents a 2D hexagonal structure formed by 1,5-dca singly bridged helical chains connected through double 1,5-dca bridges. The chelating characteristics of the H2L Schiff base ligand results in the formation of copper(II) dimer with a double phenoxo bridge presenting a very strong antiferromagnetic coupling in the copper(II) derivative (1) (J = −510 cm−1). The dimeric asymmetric unit of 1 is very similar to the active site of the catechol oxidase and, as expected, also presents catalytic activity for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in presence of O2, as demonstrated by kinetic studies of this oxidation reaction monitored by absorption spectroscopy resulting in high turnover number (Kcat = 259 h−1).  相似文献   

19.
The hetero-functionalized macrocyclic complex [CuL2](ClO4)2 bearing one N-CH2C(NH)OMe and one N-CH2CN groups as well as [CuL3](ClO4)2 bearing two N-CH2C(NH)OMe groups have been prepared selectively by the reaction of [CuL1](ClO4)2 (L2 = 2,13-bis(cyanomethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.1807.12]docosane) with methanol. The N-CH2C(NH)OCH3 group in [CuL2](ClO4)2 is quite inert against acid hydrolysis. On the other hand, the functional pendant arms in [CuL3](ClO4)2 readily undergo acid hydrolysis. Both [CuL4](ClO4)2 bearing one N-CH2COOCH3 and one N-CH2C(NH)OCH3 groups and [CuL5](ClO4)2 bearing two N-CH2OOCH3 groups have been prepared by the stepwise hydrolysis of [CuL3](ClO4)2. The reactivity of the functional pendant arms in [CuL1](ClO4)2 or [CuL3](ClO4)2 is quite different from that in [NiL1](ClO4)2 or [NiL3](ClO4)2. The crystal structure of [CuL2](ClO4)2 shows that the complex has a slightly distorted square-pyramidal coordination polyhedron with an apical Cu-N (N-CH2C(NH)OCH3 group) bond. The N-CH2C(NH)OCH3 and/or N-CH2COOCH3 groups in [CuL3](ClO4)2, [CuL4](ClO4)2, and [CuL5](ClO4)2 are involved in coordination, and the complexes have distorted trans-octahedral coordination polyhedron. The axial Cu-N (N-CH2C(NH)OCH3 group) distance (2.396(7) Å) of [CuL4](ClO4)2 is considerably longer than the Cu-N (N-CH2C(NH)OCH3 group) distance (2.169(3) Å) of [CuL2](ClO4)2.  相似文献   

20.
Two copper(II) complexes [Cu4(L1)4] (1) and [Cu2(phen)2(HL2)2] (ClO4)2 (2) have been synthesized from two potentially tridentate ligands N-(2-hydroxybenzyl) propanolamine (H2L1) and N-(2-hydroxybenzyl) ethanolamine (H2L2). X-ray analyses revealed that 1 contains a Cu4O4 cubane core, with each two Cu(II) atoms bridged by a pair of alkoxides; 2 has a bis(μ2-phenoxo)-bridged dicopper(II) structure. Variable temperature magnetic measurements of 1 have revealed that the correlation between 2J and the bridge angles φ for 1 shows a very strong antiferromagnetic tendency, i.e. the ferromagnetic and antiferromagnetic interactions cross at the φ of 94.5°. The relatively weak antiferromagnetic interactions (2J=−226.8 cm−1) with respect to the bridge angles (φ=100.4°) for 2 have been ascribed to the pyramidal distortions at the phenoxide oxygen atoms in addition to the unfavorable overlaps of the magnetic orbitals for the highly distorted copper coordination polyhedra.  相似文献   

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