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Title: XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands

Abstract

Binuclear copper complexes are known to be models for metalloenzymes containing copper active sites, and some of them are of considerable interest due to their magnetic and charge transfer properties. The reactions of the complex formation of bibasic tridentate heterocyclic imines with copper acetate leads to two types of chelates with mono deprotonated ligands and with totally deprotonated ligands. Cu K-edge EXAFS has been applied to determine the local structure around the metal center in copper(II) azomethine complexes with five tridentate ligands: 1-(salycilideneimino)- or 1-(2-tosylaminobenzilideneimino)-2-amino(oxo, thio)benzimidazoles. It has been found that some of the chelates studied are bridged binuclear copper complexes, and others are mononuclear complexes. The copper-copper interatomic distances in the bridged binuclear copper complexes were found to be 2.85-3.01 A. Variable temperature magnetic susceptibility data indicate the presence of both ferromagnetic and antiferromagnetic interactions within the dimer, the former is dominating at low temperatures and the latter at high temperatures.

Authors:
 [1];  [2]; ; ; ; ;  [3];  [1]
  1. Institute of Physics, Rostov State University, Stachki Ave., 194, 344090, Rostov-on-Don (Russian Federation)
  2. (Russian Federation)
  3. Institute of Physical and Organic Chemistry, Rostov State University, Stachki Ave., 194/2, 344090, Rostov-on-Don (Russian Federation)
Publication Date:
OSTI Identifier:
21054627
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644524; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; ACETATES; ANTIFERROMAGNETISM; BENZIMIDAZOLES; CHELATES; COPPER; COPPER COMPLEXES; COPPER IONS; CRYSTAL STRUCTURE; DIMERS; FERROMAGNETISM; FINE STRUCTURE; IMINES; INTERATOMIC DISTANCES; LIGANDS; MAGNETIC SUSCEPTIBILITY; TEMPERATURE DEPENDENCE; X-RAY SPECTROSCOPY

Citation Formats

Vlasenko, Valery G., Institute of Physical and Organic Chemistry, Rostov State University, Stachki Ave., 194/2, 344090, Rostov-on-Don, Vasilchenko, Igor S., Shestakova, Tatiana E., Uraev, Ali I., Burlov, Anatolii S., Garnovskii, Alexander D., and Pirog, Irina V. XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands. United States: N. p., 2007. Web. doi:10.1063/1.2644524.
Vlasenko, Valery G., Institute of Physical and Organic Chemistry, Rostov State University, Stachki Ave., 194/2, 344090, Rostov-on-Don, Vasilchenko, Igor S., Shestakova, Tatiana E., Uraev, Ali I., Burlov, Anatolii S., Garnovskii, Alexander D., & Pirog, Irina V. XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands. United States. doi:10.1063/1.2644524.
Vlasenko, Valery G., Institute of Physical and Organic Chemistry, Rostov State University, Stachki Ave., 194/2, 344090, Rostov-on-Don, Vasilchenko, Igor S., Shestakova, Tatiana E., Uraev, Ali I., Burlov, Anatolii S., Garnovskii, Alexander D., and Pirog, Irina V. Fri . "XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands". United States. doi:10.1063/1.2644524.
@article{osti_21054627,
title = {XAFS Study of the Ferro- and Antiferromagnetic Binuclear Copper(II) Complexes of Azomethine Based Tridentate Ligands},
author = {Vlasenko, Valery G. and Institute of Physical and Organic Chemistry, Rostov State University, Stachki Ave., 194/2, 344090, Rostov-on-Don and Vasilchenko, Igor S. and Shestakova, Tatiana E. and Uraev, Ali I. and Burlov, Anatolii S. and Garnovskii, Alexander D. and Pirog, Irina V.},
abstractNote = {Binuclear copper complexes are known to be models for metalloenzymes containing copper active sites, and some of them are of considerable interest due to their magnetic and charge transfer properties. The reactions of the complex formation of bibasic tridentate heterocyclic imines with copper acetate leads to two types of chelates with mono deprotonated ligands and with totally deprotonated ligands. Cu K-edge EXAFS has been applied to determine the local structure around the metal center in copper(II) azomethine complexes with five tridentate ligands: 1-(salycilideneimino)- or 1-(2-tosylaminobenzilideneimino)-2-amino(oxo, thio)benzimidazoles. It has been found that some of the chelates studied are bridged binuclear copper complexes, and others are mononuclear complexes. The copper-copper interatomic distances in the bridged binuclear copper complexes were found to be 2.85-3.01 A. Variable temperature magnetic susceptibility data indicate the presence of both ferromagnetic and antiferromagnetic interactions within the dimer, the former is dominating at low temperatures and the latter at high temperatures.},
doi = {10.1063/1.2644524},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • A series of bimetallic complexes of ruthenium(II) bridged by heterocyclic ligands formed by the condensation of 4,5-diazafluoren-9-one with various diamines, hydrazine, 1,4-phenylenediamine, benzidine, and 4,4{prime}-methylene-dianiline, results in metal centers separated by various distances. The complexes give rise to metal-to-ligand charge-transfer absorptions in the 450 nm region of the visible spectrum and intraligand {pi} {yields} {pi}* transitions in the 300 nm region of the ultraviolet spectrum. The ruthenium(II) centers are oxidized in two closely spaced one-electron processes at potentials more positive than that for Ru(bpy){sub 3}{sup 2+}. The bridging ligands are reduced by two closely spaced one-electron processes at more positivemore » potentials than that for reduction of the coordinated bipyridine ligands ({approximately} {minus}1.30 V), although the diazafluorene {double_bond} N {minus} N {double_bond} diazafluorene bridging ligand is reduced reversibly in two single-electron steps at E{sub 1/2} values of {minus} 0.29 and {minus}0.52 V. After purification by eluting the pure complexes over a silica gel column with various concentrations of 0.10 M NH{sub 4}PF{sub 6} in methanol, emission occurs only in a glassy matrix at 77 K and at low temperatures in solution. The emission lifetimes at 77 K in a 4:1 ethanol: methanol glass are 5 {+-} 1 {micro}s. A variable-temperature emission lifetime study reveals the presence of a low-lying state with {Delta}E = {approximately} 1,500 cm{sup {minus}1}, and extrapolation to room temperature indicates the emission lifetimes are in the subnanosecond range.« less
  • A series of polypyridyl ruthenium(II) complexes containing monodentate pyridyl- and cyano-substituted acetylenes have been prepared. Complexes of the type Ru(tpy)(bpy)L{sup 2+} (where tpy = 2,2{prime}:6{prime}:2{double_prime}-terpyridine (C{sub 15}H{sub 11}N{sub 3}), bpy = 2,2{prime}-bipyridine (C{sub 10}H{sub 8}N{sub 2}), and L = pyridine (py) (C{sub 5}H{sub 5}N), pyridylacetylene (PA) (C{sub 7}H{sub 5}N), phenylpyridylacetylene (PPA) (C{sub 10}H{sub 9}N), dipyridylacetylene (DPA) (C{sub 12}H{sub 8}N{sub 2}), CH{sub 3}CN, cyanoacetylene (CA) (C{sub 3}HN), and cyanophenylacetylene (CPA) (C{sub 9}H{sub 5}N)) have been prepared, and their synthesis and characterization are reported herein. The complexes [Ru(tpy)(bpy)(PPA)](PF{sub 6}){sub 2}{center_dot}(CH{sub 3}){sub 2}CO, [Ru(tpy)(bpy)(PA)](PF{sub 6}){sub 2}{center_dot}(CH{sub 3}){sub 2}CO, and [Ru(tpy)(bpy)(CH{sub 3}CN)](PF{sub 6}){sub 2}more » have been crystallized and the crystal structures determined. [Ru(tpy)(bpy)(CH{sub 3}CN)](PF{sub 6}){sub 2} crystallizes in the monoclinic P2{sub 1}/c space group. [Ru(tpy)(bpy)(PA)](PF{sub 6}){sub 2}{center_dot}(CH{sub 3}){sub 2}CO crystallizes in the triclinic P{bar 1} space group. [Ru(tpy)(bpy)(PPA)](PF{sub 6}){sub 2}{center_dot}(CH{sub 3}){sub 2}CO crystallizes in the triclinic P{bar 1} space group. The inclusion of the functionalized acetylene groups makes these complexes possible precursors to metal-coordinated polyacetylenes.« less
  • Electrochemical techniques were employed to study electron transfer properties of a binuclear copper--macrocyclic ligand complex and to prepare several reduced derivatives. The complex, Cu/sup II/Cu/sup II/L(ClO/sub 4/)/sub 2/.2H/sub 2/O, was prepared by condensing 1,3-diaminopropane with 5-methyl-2-hydroxyisophthalaldehyde and Cu(ClO/sub 4/)/sub 2/.6H/sub 2/O. The Cu/sup II/Cu/sup II/ complex was reduced in successive, quasi-reversible, one-electron steps at - 0.52 and - 0.91 V vs. NHE. Constant-potential electrolysis was employed to prepare the reduced species, Cu/sup II/Cu/sup I/L(ClO/sub 4/) and Cu/sup I/Cu/sup I/L, both of which were isolated and fully characterized. The mixed-valence species, Cu/sup II/Cu/sup I/L/sup +/, is stable in oxygen-free solutions (conproportionationmore » constant: 3.97 x 10/sup 6/) and reacts with carbon monoxide to form an adduct, Cu/sup II/Cu/sup I/L(CO)ClO/sub 4/. The diamagnetic Cu/sup I/Cu/sup I/L species was obtained as essentially insoluble black needles which, however, formed a soluble dicarbonyl adduct, Cu/sup I/Cu/sup I/L(CO)/sub 2/, on exposure to CO. The latter complex was not isolated. At the ambient temperature Cu/sup II/Cu/sup I/L/sup +/ exhibits an isotropic seven-line solution EPR spectrum while an anisotropic pattern was observed in frozen solutions (77/sup 0/K), with four lines for g parallel to and unresolved g perpendicular to. Variable-temperature experiments indicated coalescence at about 200/sup 0/K suggesting an intramolecular electron transfer rate of about 1.7 x 10/sup 10/ s/sup -1/ at 298/sup 0/K. Electronic absorption spectral measurements revealed at least two absorptions for Cu/sup II/Cu/sup I/L(ClO/sub 4/)/sub 2/ at 1700 and 1200 nm (CH/sub 2/Cl/sub 2/), which are not present in Cu/sup II/Cu/sup II/L(ClO/sub 4/)/sub 2/.2H/sub 2/O, Cu/sup I/Cu/sup I/L, or the carbonyl derivatives. The new spectral bands may be attributable to intramolecular electron transfer processes. 11 figures, 5 tables.« less
  • Four chloride-bridged, binuclear bis(cyclopentadienyl) rare-earth-metal complexes have been subjected to detailed mass spectrometric studies adopting exhaustively the B/E-linked scan technique: (Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl)){sub 2} (1), ((Me{sub 3}SiC{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl)){sub 2} (2), (Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Y({mu}-Cl)){sub 2} (3), and Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2}Yb({mu}-Cl){sub 2}Y(C{sub 5}H{sub 4}){sub 2}SiMe{sub 2} (5). The strict dominance of binuclear fragments in the spectrum of pure 1 indicates, in excellent accordance with a previous crystallographic X-ray study, the presence of metal-bridging Me{sub 2}Si(C{sub 5}H{sub 4}){sub 2} ligands in the vapor state. The existence of the new complex 5, which could not bemore » separated chemically from admixtures of 1 and 3 (i.e., from sample 4), has been confirmed unambiguously by deducing its individual fragmentation pattern from a systematic B/E-linked scan analysis.« less
  • Compounds of the type (ArylNHCH{sub 2}CH{sub 2}){sub 2}O (Aryl = 2,6-Me{sub 2}C{sub 6}H{sub 3} (H{sub 2}[1a])), 2,6-Et{sub 2}C{sub 6}H{sub 3} (H{sub 2}[1b]), 2,6-i-Pr{sub 2}C{sub 6}H{sub 3} (h{sub 2}[1c]) can be prepared by treating (TsOCH{sub 2}CH{sub 2}){sub 2}O (TsO = tosylate) with the lithium anilides in THF. [1a,b]TiCl{sub 2}, [1a,b]TiMe{sub 2}, [1a]Ti(CH{sub 2}Ph){sub 2}, [1a-c]M(NMe{sub 2}){sub 2} (M = Zr or Hf), [1a-c]MCl{sub 2}, and [1a-c]MR{sub 2} (R = Me, Et, i-Bu) were prepared. An X-ray study of [1a] Ti(CH{sub 2}Ph){sub 2} revealed the structure to be a distorted trigonal bipyramid (type B) in which the two amido nitrogens and onemore » benzyl ligand occupy equatorial positions. An X-ray study of [1a]ZrMe{sub 2} showed it to be a distorted trigonal bipyramid that contains axial amido groups (type A), while an X-ray study of [1c]HfEt{sub 2} revealed it to have a structure halfway between type A and type B, i.e,, a distorted square pyramid with one alkyl in the apical position. Zr and Hf dimethyl complexes that contain an oxygen donor or a sulfur donor ligand can be activated with [Ph{sub 3}C][B(C{sub 6}F{sub 5}){sub 4}] to yield efficient catalysts for polymerization of 1-hexene, although the molecular weight of the poly(1-hexene) chains is limited to {approximately}20,000-{approximately}25,000 under the conditions employed. Neither {l_brace}[1c]ZrMe(ether){r_brace}[B(C{sub 6}F{sub 5}){sub 4}] nor {l_brace}[1c]HfMe(ether){r_brace}[B(C{sub 6}F{sub 5}){sub 4}] will polymerize 1-hexene in C{sub 6}D{sub 5}Br at room temperature, and neither will polymerize ethylene readily at 1 atm and 25 C. It is proposed that a solvated five-coordinate cation must lose the solvent in order to react with an olefin and that {beta}-hydride elimination in the four-coordinate cation limits chain length.« less