Mono- and Dinuclear Copper(II) and Iron(II) Complexes of a Tetradentate Bispidine-diacetate Ligand

2009 ◽  
Vol 62 (10) ◽  
pp. 1238 ◽  
Author(s):  
Peter Comba ◽  
Lena Daumann ◽  
Julie Lefebvre ◽  
Gerald Linti ◽  
Bodo Martin ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Quadrupole Doublet ◽  
Axial Position ◽  
Water Ligand ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
X Ray Crystallography ◽  
Pyramidal Geometry ◽  
Carboxylic Groups ◽  
Concentrated Solution

The synthesis of a new tetradentate bispidine ligand (LH2 = 2,2′-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonan-3,7-diyl)diacetic acid), containing two tertiary amine and two carboxylic groups, is reported along with the preparation and characterization of the corresponding Cu(ii) and Fe(iii) complexes. The mononuclear [LCu(OH2)]·4H2O (1) complex contains a five-coordinate Cu(ii) centre, which adopt a square pyramidal geometry with the four donor atoms of the ligand (N2O2) occupying the equatorial plane and a water molecule occupying the axial position. An axial electron paramagnetic resonance (EPR) signature is observed for 1 (gx = 2.054, gy = 2.050, gz = 2.234; Ax = 18 × 10–4 cm–1, Ay = 20 × 10–4 cm–1, Az = 188 × 10–4 cm–1) in frozen methanolic solution (0.1 mM). Dimerization of 1 in concentrated solution (10 mM) was observed by EPR spectroscopy (g∥ = 2.24, g⊥ = 2.07, A∥ = 195 × 10–4 cm–1, and A⊥ = 12 × 10–4 cm–1 for each Cu centre). The structure of the dimeric species [LCu(OH2)]2 (1b) was determined by a combination of molecular mechanics with the simulation of the EPR spectrum (MM-EPR). The dimer has each Cu(ii) centre coordinated by the two amines and one carboxylate of one ligand (L), while the other carboxylate bridges to the second Cu(ii) centre; each coordination sphere is completed by an axial water ligand, with the Cu···Cu distance 5.5 Å (relative orientation from EPR simulation: α = 60°, β = 0°, γ = 25°). The aqueous reaction between the tetradentate ligand (L) and Fe(ii) leads to the formation of an oxo-bridged diiron(iii) complex, [LFe-(μ-O)-FeL] (2), with a Fe–O–Fe angle of 180° (dFe···Fe = 3.516 Å), as revealed by X-ray crystallography. The Mössbauer spectrum of 2 consists of one quadrupole doublet with an isomer shift (δ) of 0.37 mm s–1 and a quadrupole splitting (ΔEQ) of 0.73 mm s–1, which is consistent with S = 5/2 Fe(iii) centres. Variable-temperature magnetic susceptibility measurements show the presence of intramolecular antiferromagnetic interactions between the two Fe(iii) centres, with an exchange coupling constant J of –91(3) cm–1 (H = –2JS1·S2).

scholarly journals Capturing a Tetratomic Nitrogen Ring cyclo-N4 inside an Aza[ 82 ]fullerene

2021 ◽  
Author(s):  
Yuanyuan Wang ◽  
Ziqi Hu ◽  
Wangqiang Shen ◽  
Tonghui Zhou ◽  
Shinobu Aoyagi ◽  
...  
Keyword(s):  
Arc Discharge ◽  
Fullerene Cage ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
X Ray Crystallography ◽  
Covalently Bonded ◽  
Electron Paramagnetic ◽  
Nitrogen Ring ◽  
Chemical Peculiarity ◽  
Radical Character

Abstract Synthesis of polymeric nitrogen compounds is a formidable task due to the proneness of nitrogen to the formation of N ≡ N triple bond, one of the strongest chemical bonds known. Here, we report an arc-discharge approach to successfully stabilize the elusive four-membered nitrogen ring (cyclo-N4) in an unprecedented endohedral metallofullerene Dy2N4@C81N (Dy-I). Its molecular structure has been unambiguously determined by X-ray crystallography to show a covalently bonded cyclo-N4 plane bridging two dysprosium ions inside an aza[82]fullerene cage, highlighting the stabilization of cyclo-N4 as a concurrent result of fullerene encapsulation and metal coordination. Our computational results further reveal a six-center-one-electron (6c-1e) bond delocalized over the inverse-sandwich Dy-N4-Dy cluster. This chemical peculiarity stems from the diffuse radical character of the highly anionic cyclo-N43− ligand, which is confirmed by electron paramagnetic resonance (EPR) spectrum of Y2N4@C81N (Y-I).

Tris-triphenylsiloxy compounds of aluminium

1992 ◽  
Vol 70 (3) ◽  
pp. 771-778 ◽  
Author(s):  
Allen W. Apblett ◽  
Alison C. Warren ◽  
Andrew R. Barron
Keyword(s):  
Variable Temperature ◽  
Molecular Structures ◽  
Water Ligand ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Phenyl Rings ◽  
Coordinated Water ◽  
Hydrolysis Of ◽  
Solvent Complex

The reaction of AlMe3 with three equivalents of HOSiPh3 in THF results in the formation of the solvent complex Al(OSiPh3)3(THF) (1). Hydrolysis of 1 yields the stable water complex Al(OSiPh3)3(H2O)(THF)2 (2) in which the THF molecules are hydrogen bonded to the coordinated water ligand. Compounds 1 and 2 have been fully characterized by 1H, 13C, 17O, 27Al, and 29Si NMR and IR spectroscopy. In addition, variable temperature 1H NMR of 2 has been employed to investigate the steric interactions between the phenyl rings of adjacent siloxide ligands. The molecular structures of the solvates 1•(THF) and 2•(THF)1.25 have been determined by X-ray crystallography. 1•(THF): monoclinic P21/c, a = 10.03 (1), b = 23.758 (6), c = 23.294 (7) Å, β = 101.13 (6)°, Z = 4, R = 0.084, Rw = 0.094. 2•(THF)1.25: cubic [Formula: see text], a = 23.034 (3) Å, Z = 4, R = 0.093, Rw = 0.099. Keywords: aluminium, siloxide, hydrolysis, complex, NMR spectroscopy.

Spectroscopy of Naphthalene Diimides and Their Anion Radicals

2004 ◽  
Vol 57 (10) ◽  
pp. 1011 ◽  
Author(s):  
Goja Andric ◽  
John F. Boas ◽  
Alan M. Bond ◽  
Gary D. Fallon ◽  
Kenneth P. Ghiggino ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Mirror Image ◽  
High Yield ◽  
Side Chains ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
X Ray Crystallography ◽  
Naphthalene Diimide ◽  
Electron Reduction ◽  
Naphthalene Diimides

Naphthalene diimides 1–4 having different N,N-disubstitution undergo single electron reduction processes either chemically or electrochemically to yield the corresponding radical anion in high yield. This study concentrates on 1, bearing pentyl side chains connected through the diimide nitrogens, and compares the results obtained against those bearing isopropyl, propargyl, and phenylalanyl side chains. Compound 1 exhibits mirror image absorption and fluorescence in the near-UV region in CH2Cl2 and dimethylformamide that is typical of monomeric N,N-dialkyl-substituted naphthalene diimides. In toluene, excimer-like emission is observed, which suggests ground-state complexes involving 1 are formed. X-Ray crystallography has been used to characterize 1 in the solid state. Cyclic voltammetry enables the reversible potentials for [NDI]0/– and [NDI]−/2– type processes to be measured. Bulk one-electron reduction of 1–4 is characterized by dramatic changes in the absorption and emission spectra. Additionally, highly structured EPR (electron paramagnetic resonance) signals from dimethylformamide solutions of the radical anions of 1–3 have been obtained and are consistent with coupling between the unpaired electron and the naphthalene diimide nitrogens and hydrogens and the NCH hydrogens of the appropriate side chains. The overall structure of the EPR spectrum is substituent-dependent. These changes in spectroscopic output upon an electronic input may be described as a simple ‘on/off’ switching mechanism with which to apply a ‘bottom-up’ approach to molecular device manufacture.

Tris(N,N-dialkyldithiocarbamato-S,S')thiotungsten(VI) Complexes and the X-Ray Crystal Structure of [WS(S2CNEt2)3]BF4

1994 ◽  
Vol 47 (11) ◽  
pp. 2075 ◽  
Author(s):  
CG Young ◽  
TO Kocaba ◽  
M Sadek ◽  
RTC Brownlee ◽  
ERT Tiekink
Keyword(s):  
Variable Temperature ◽  
The Other ◽  
Axial Position ◽  
Monoclinic Space Group ◽  
Equatorial Position ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dithiocarbamate Ligand ◽  
R Value

The orange, diamagnetic compounds [WS(S2CNR2)3]X(R = Me, X- = BF4-, BPh4-;R = Et, X- =BF4-) were prepared by reacting WSCl4 and Me3SiS2CNR2 in dichloromethane, followed by metathesis with NaX in methanol. The compounds were characterized by elemental analysis, infrared and variable-temperature 1H n.m.r. spectroscopy and X-ray crystallography. Crystals of [WS(S2CNEt2)3] BF4 were monoclinic, space group P21/a with a 12.293(1), b 17.229(5), c 14.257(2) Ǻ,β 113.69(1)°, V 2765(2) Ǻ3 and Dc = 1.796 g cm-3 for Z = 4. The structure was solved by the Patterson method and refined by a full-matrix least-squares procedure, 3961data being used, to a conventional R value of 0.039 ( Rw = 0.040). The seven-coordinate cation possesses a pentagonal-bipyramidal geometry; the terminal thio ligand [W=S 2.127(2)Ǻ] occupies an axial position, a unique dithiocarbamate ligand spans the other axial position and an equatorial position while the two other dithiocarbamate ligands occupy the four remaining equatorial sites.

Radiation Effects on Hollandite Ceramics developed for Radioactive Cesium Immobilization

2003 ◽  
Vol 792 ◽  
Author(s):  
V. Aubin ◽  
D. Caurant ◽  
D. Gourier ◽  
N. Baffier ◽  
S. Esnouf ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Liquid Waste ◽  
Fission Products ◽  
Radioactive Cesium ◽  
Radioactive Liquid Waste ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Γ Radiation ◽  
The Stability ◽  
High Level

ABSTRACTProgress on separating the long-lived fission products from the high level radioactive liquid waste (HLW) has led to the development of specific host matrices, notably for the immobilization of cesium. Hollandite (nominally BaAl2Ti6O16), one of the main phases constituting Synroc, receives renewed interest as specific Cs-host wasteform. The radioactive cesium isotopes consist of short-lived Cs and Cs of high activities and Cs with long lifetime, all decaying according to Cs+→Ba2++e- (β) + γ. Therefore, Cs-host forms must be both heat and (β,γ)-radiation resistant. The purpose of this study is to estimate the stability of single phase hollandite under external β and γ radiation, simulating the decay of Cs. A hollandite ceramic of simple composition (Ba1.16Al2.32Ti5.68O16) was essentially irradiated by 1 and 2.5 MeV electrons with different fluences to simulate the β particles emitted by cesium. The generation of point defects was then followed by Electron Paramagnetic Resonance (EPR). All these electron irradiations generated defects of the same nature (oxygen centers and Ti3+ ions) but in different proportions varying with electron energy and fluence. The annealing of irradiated samples lead to the disappearance of the latter defects but gave rise to two other types of defects (aggregates of light elements and titanyl ions). It is necessary to heat at relatively high temperature (T=800°C) to recover an EPR spectrum similar to that of the pristine material. The stability of hollandite phase under radioactive cesium irradiation during the waste storage is discussed.

scholarly journals Crystal structure of 3-benzyl-2-[(E)-2-(furan-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one and 3-benzyl-2-[(E)-2-(thiophen-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one from synchrotron X-ray diffraction

2018 ◽  
Vol 74 (1) ◽  
pp. 10-14
Author(s):  
Flavien A. A. Toze ◽  
Vladimir P. Zaytsev ◽  
Lala V. Chervyakova ◽  
Elisaveta A. Kvyatkovskaya ◽  
Pavel V. Dorovatovskii ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Axial Position ◽  
Isatoic Anhydride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Angles ◽  
Pyramidal Geometry ◽  
Three Component Reaction ◽  
Racemic Crystals

The chiral title compounds, C21H18N2O2, (I), and C21H18N2OS, (II) – products of the three-component reaction between benzylamine, isatoic anhydride and furyl- or thienyl-acrolein – are isostructural and form isomorphous racemic crystals. The tetrahydropyrimidine ring in (I) and (II) adopts a sofa conformation. The amino N atom has a trigonal–pyramidal geometry [sum of the bond angles is 347.0° for both (I) and (II)], whereas the amido N atom is flat [sum of the bond angles is 359.3° for both (I) and (II)]. The furyl- and thienylethenyl substituents in (I) and (II) are planar and the conformation about the bridging C=C bond isE. These bulky fragments occupy the axial position at the quaternary C atom of the tetrahydropyrimidine ring, apparently, due to steric reasons. In the crystals, molecules of (I) and (II) form hydrogen-bonded helicoidal chains propagating along [010] by strong intermolecular N—H...O hydrogen bonds.

Synthesis, structural and magnetic properties of macrocyclic aza-amido binuclear copper(II) complexes

1989 ◽  
Vol 67 (4) ◽  
pp. 662-670 ◽  
Author(s):  
Sanat K. Mandal ◽  
Laurence K. Thompson ◽  
Michael J. Newlands ◽  
Amal K. Biswas ◽  
Bibhutosh Adhikary ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Complex Iii ◽  
Azomethine Nitrogen ◽  
X Ray Diffraction ◽  
Binuclear Copper ◽  
Magnetic Studies ◽  
Monoclinic System ◽  
Space Group ◽  
Pyramidal Geometry ◽  
Square Planar

Binuclear, antiferromagnetically coupled, macrocyclic copper(II) complexes, [Cu2(C28H32N4O4)]•H2O (II) and [Cu2(C36H32N4O4)]•CH3CN•H2O (III), involving asymmetric ligands with two deprotonated amide, two azomethine nitrogen, and two phenoxide donors at the binuclear centre, have been synthesized and characterized by single-crystal X-ray diffraction and variable temperature magnetic studies. Complex II crystallizes in the monoclinic system, space group P21/n, with a = 16.4854(9) Å, b = 7.6005(13) Å, c = 21.1617(11) Å, β = 104.090(5)°, Z = 4, Rf = 0.068 for 2062 significant reflections. The two copper(II) centres have square planar N2O2 donor sets with two phenoxide oxygen atoms bridging the copper centres with a copper–copper separation of 2.898(2) Å. A long copper–oxygen (amide) contact (2.808(10) Å) forms a weak dimer association. Complex III crystallizes in the triclinic system, space group [Formula: see text], with a = 8.7771(9) Å, b = 12.3983(16) Å, c = 15.7299(16) Å, α = 85.003(11)°, β = 84.574(8)°, γ = 76.838(10)°, Z = 2, Rf = 0.041 for 2966 significant reflections. The two copper(II) centres have distorted square-pyramidal geometry involving an N2O2 in plane donor set and two phenoxide oxygen bridges with a copper–copper separation of 3.018(1) Å. The fifth coordination site at each copper centre involves an amide oxygen from a neighbouring molecule (Cu(1)—O 2.371(4), Cu(2)—O 2.413(3) Å) in a staggered intermolecular array. Very strong antiferromagnetic exchange is observed in both cases (−2J = 689 ± 7 cm−1 (II), −2J = 816 ± 8 cm−1 (III)). Keywords: macrocycles, binuclear copper(II) complexes.

scholarly journals Syntheses, Structures, Magnetic Properties and Antibacterial Activities of Two Copper(II) Azido Complexes with Varied Nuclearities Containing Symmetrical 1,3-Diammine as Chelator

2021 ◽  
Vol 33 (2) ◽  
pp. 359-366
Author(s):  
Habibar Chowdhury ◽  
Chandan Adhikary
Keyword(s):  
Hydrogen Bonds ◽  
Variable Temperature ◽  
Antibacterial Activities ◽  
Metal Centers ◽  
X Ray ◽  
Pyramidal Geometry ◽  
Azide Ion ◽  
3D Network ◽  
Square Pyramidal Geometry ◽  
Dinuclear Structure

Two copper(II) azido complexes of the types mononuclear [Cu(TMEDA)2(N3)2] (1) and dinuclear [Cu(TMEDA)(μ1,1-N3)(N3)]2 (2) [TMEDA = trimethylenediamine; N3 – = azide ion] have been synthesized and characterized. X-ray structural analysis revealed that each copper(II) center in complex 1 adopts a distorted octahedron geometry with a CuN6 chromophore ligated through four N atoms of two different symmetrical TMEDA ligands as bidentate chelator and two N atoms of two terminal azides. In complex 2, each copper(II) center adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of TMEDA as bidentate chelator and two N atoms of two different azides as μ1,1-N3 bridging mode and one N atom of terminal azide ion. The two copper centers are connected through double μ1,1-N3 bridges affording a dinuclear structure with Cu···Cu separation 3.327(2) Å. In crystalline state, mononuclear units in complex 1 are associated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 2D sheet structure viewed along crystallographic b-axis, whereas dinuclear entities in complex 2 are propagated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 3D network structure viewed along crystallographic a-axis. The Variable-temperature magnetic susceptibility measurement evidenced a dominant antiferromagnetic interaction between the metal centers through μ1,1-azide bridges in complex 2 with J = − 0.40 cm-1. The antibacterial activities of the complexes have also been studied.

scholarly journals An Isolable Mononuclear Palladium(I) Amido Complex

2021 ◽  
Author(s):  
jian Liu ◽  
Melissa Bollmeyer ◽  
Yujeong Kim ◽  
Dengmengfei Xiao ◽  
Samantha N. Macmillan ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Bond Cleavage ◽  
Primary Amines ◽  
Dispersion Force ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pauli Repulsion ◽  
Catalyzed Reactions ◽  
Electron Paramagnetic

Mononuclear Pd(I) species are putative intermediates in Pd-catalyzed reactions, but our knowledge about them is limited due to difficulties in accessing them. Herein, we report the isolation of a Pd(I) amido complex, [(BINAP)Pd(NHArTrip )] (BINAP = 2,2′- bis(diphenylphosphino)-1,1′-binaphthalene, ArTrip = 2,6-bis(2’,4’,6’-triisopropylphenyl)phenyl), from the reaction of (BINAP)PdCl2 with LiNHArTrip. This Pd(I) amido species has been characterized by X-ray crystallography, electron paramagnetic resonance, and multi-edge Pd Xray absorption spectroscopy. Theoretical study revealed that, while the 3-electron-2-center π interaction between Pd and N in the Pd(I) complex imposes severe Pauli repulsion in its Pd–N bond, pronounced attractive inter-ligand dispersion force aids its stabilization. In accord with its electronic features, reactions of homolytic Pd–N bond cleavage and deprotonation of primary amines are observed on the Pd(I) amido complex.

Synthesis and characterization of new tetra-substituted porphyrins with exo-donor carboxylic groups as building blocks for supramolecular architectures: Catalytic and structural studies of their metalated derivatives

2010 ◽  
Vol 14 (09) ◽  
pp. 804-814 ◽  
Author(s):  
Lucia Carlucci ◽  
Gianfranco Ciani ◽  
Simona Maggini ◽  
Davide M. Proserpio ◽  
Fabio Ragaini ◽  
...  
Keyword(s):  
Building Blocks ◽  
Supramolecular Organization ◽  
Silver Complexes ◽  
Structural Studies ◽  
Polymeric Compound ◽  
X Ray ◽  
X Ray Crystallography ◽  
Supramolecular Architectures ◽  
Carboxylic Groups

We report herein the synthesis of the porphyrins 5,10,15,20-tetrakis(4-carboxybiphenyl)-porphyrin (H2TCBP) and 5,10,15,20-tetrakis(4-carboxy-2,6-dimethylbiphenyl)porphyrin (H2TCDMBP) bearing diphenyl units on meso-positions, and of their cobalt and silver derivatives. The silver complexes of H2TCDMBP and of H2TCPP ( H2TCPP = 5 ,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) were investigated by X-ray crystallography and their supramolecular organization elucidated. Co(TCBP) was reacted with copper formate, yielding a polymeric compound that showed a catalytic activity in the benzylic amination of hydrocarbons using arylazide as aminating agent.

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