ESR study of the structure and bonding parameters in binary copper(II) complexes of some α-amino acids and dipeptides

1990 ◽  
Vol 55 (2) ◽  
pp. 546-554 ◽  
Author(s):  
Milan Strašák ◽  
Zlatica Durcová
Keyword(s):  
Room Temperature ◽  
Local Symmetry ◽  
Heterocyclic Ring ◽  
Tridentate Ligand ◽  
Imino Group ◽  
Electron Absorption Spectroscopy ◽  
Physiological Conditions ◽  
Bonding Parameters ◽  
Binary Complexes ◽  
Metal Ligand

Binary 1 : 1 copper(II)-amino acid and copper(II)-dipeptide complexes, [CuL] and [CuL]+ (H2L = +H3N-CHR-CO-NH-CHR'-COO-, HL' = +H3N-CHR-COO-), have been investigated in aqueous solution by means of ESR and electron absorption spectroscopy. Molecular orbital coefficients characteristic of the metal-ligand bonds have been derived for an effective D4h local symmetry. It is suggested that at the pH near to the physiological conditions both histidine and tryptophan coordinate as a tridentate ligand via O(carboxyl), N(heterocyclic ring) and N(amino) atoms. ESR investigation at room temperature and in frozen aqueous solutions, and visible spectral evidence suggest histamine-like coordination of histidine and tryptamine-like coordination of tryptophan in the quatorial plane of the binary complexes. Since proline contains the imino group, there is no ionizable amide-NH-proton when it is inserted in a peptide chain, hence the proline-nitrogen is unable to bind metal ions in peptides.

scholarly journals Metal–ligand covalency enables room temperature molecular qubit candidates

2019 ◽  
Vol 10 (27) ◽  
pp. 6707-6714 ◽  
Author(s):  
Majed S. Fataftah ◽  
Matthew D. Krzyaniak ◽  
Bess Vlaisavljevich ◽  
Michael R. Wasielewski ◽  
Joseph M. Zadrozny ◽  
...  
Keyword(s):  
Room Temperature ◽  
Spin Dynamics ◽  
Metal Ligand ◽  
Coherent Spin

Metal–ligand covalency enables observation of coherent spin dynamics to room temperature in a series of vanadium(iv) and copper(ii) catechol complexes.

Metal ligand interactions under physiological conditions

1993 ◽  
Vol 51 (1-2) ◽  
pp. 188
Author(s):  
J.J. Powell ◽  
P Taylor ◽  
R.P.H. Thompson
Keyword(s):  
Physiological Conditions ◽  
Ligand Interactions ◽  
Metal Ligand

ChemInform Abstract: Electronic Spectrum and Metal-Ligand Bonding Parameters of the V(H2O)3+ 6 Ion.

ChemInform ◽  
1988 ◽  
Vol 19 (30) ◽  
Author(s):  
M. A. HITCHMAN ◽  
R. G. MCDONALD ◽  
P. W. SMITH ◽  
R. STRANGER
Keyword(s):  
Electronic Spectrum ◽  
Bonding Parameters ◽  
Metal Ligand

scholarly journals SYNTHESIS AND SPECTRAL CHARACTERISTICS OF HETEROMETALLIC COMPLEXES OF Pr(III) WITH Zn(II), CO(II) BASED ON ETHYLENEDIAMINETETRAACETIC AND ETHYLENEDIAMINEDISUCCINIC ACIDS

2021 ◽  
Vol 87 (3) ◽  
pp. 3-17
Author(s):  
Elena Trunova ◽  
Artem Mishchenko ◽  
Tamara Makotryk
Keyword(s):  
Spectral Characteristics ◽  
Local Symmetry ◽  
Heterometallic Complexes ◽  
Molar Ratio ◽  
Ligand Field ◽  
Electron Absorption Spectroscopy ◽  
Lanthanide Ion ◽  
3D Metals ◽  
Equimolar Composition ◽  
Heteronuclear Complexes

New heterometallic f-d-complexes of Pr (III), Co(II), Zn(II) with aminopolycarboxylic acids (ethylenediaminetetraacetic, ethylenediaminedisuccinic acids) have been synthesized and spectroscopically characterized. It was found that complexes with a molar ratio of Pr:M3d: EDTA=1:2:2 are formed for ethylenediaminetetraacetic compounds, and that in the case of complexes based on EDDS, heteronuclear compounds of the equimolar composition Pr: M3d: EDDS = 1: 1: 1 are formed. It is shown that it is expedient to carry out the synthesis of heterometallic complexes on the basis of mono­nuclear polycarboxylates of 3d metals, which act as a «building block» for the preparation of a heterobinuclear compound by the exo coordination of additional metal ions. The complexes are characterized by the method of electron absorption spectroscopy. It is shown that independent of 3d-metal, for both heterometallic systems based on EDDS, a hypsochromic shift of the absorption maxima relative to νmax is observed for the homonuclear praseodymium complex. For ethylenediaminetetraacetate systems, the absorption maxima undergo both low- and high-frequency shift, which indicates the different nature of the ligand field effect, which is caused primarily by differences in the structure of the corresponding heteronuclearaminopolycarboxylates due to the presence of a chiral carbon atom in the EDDS molecule. For the supersensitive transitions Pr(III)) 3H4 →3P2 and 3H4 → 1D2 , the covalence parameters of the Ln-O bond have been calculated: osci­llator power (P), nepheloxetic parameter (β), covalence parameter (b1/2), Sinha parameter (δ). Analysis of the spectroscopic parameters indicates a decrease in the covalence of the lanthanide-ligand bond in the transition from mono- to heteronuclear complex, and a decrease in the local symmetry of the lanthanide ion occurs in the order Ln (III) aqua ion <hete­rometallic complex <monometallic complex. Heteronuclear complexes are several orders of magnitude more stable than mononuclear ones due to the formation of additional bonds or metallacycles with donor ligand atoms. It is noted that the stability of complexes with EDDS is lower than that of the corresponding complexes with EDTA due to the different size and number of chelated metallacycles. The obtained heteronuclear complexes belong to folded complexes, in which the ligand-complexone realizes the maximum denticity to the lanthanide ion, and the coordination sphere of the 3d-cation is formed by carboxyl groups EDTA / EDDS and inner-sphere water molecules. In this case, the ions of 3d-metals are in a distorted octahedral environment, and the coordination number of Pr(III) is 8.

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXVII Synthesis, Spectroscopy and Structural Systematics of Some 1 : 3 Adducts of Silver(I) Compounds with Triphenylarsine, [(Ph3As)3AgX], X = Cl, Br, I, SCN

1997 ◽  
Vol 50 (6) ◽  
pp. 577 ◽  
Author(s):  
Graham A. Bowmaker ◽  
Effendy ◽  
John D. Kildea ◽  
Allan H. White
Keyword(s):  
Room Temperature ◽  
Far Infrared ◽  
Phosphine Ligands ◽  
Lewis Base ◽  
X Ray ◽  
Bonding Parameters ◽  
Pseudo Halides ◽  
The Relationship ◽  
Far Infrared Spectra

The syntheses and room-temperature single-crystal X-ray structure determination of 1 : 3 adducts formed between silver(I) (pseudo-)halides, AgX, and triphenylarsine, AsPh3, are described (X = Cl, Br, I, SCN), [(Ph3As)3AgX], (1)–(4). The chloride (1) has been previously described as its acetone hemisolvate; other solvates (1a–d) (0·75 MeCN, MeOH, 1·5 pyridine, 0·75 2,6-dimethylpyridine) are isomorphous, being triclinic, P-1, a ≈ 13·5, b ≈ 14·0, c ≈ 14·25 Å, α ≈ 83, β ≈ 87, γ ≈ 76°, V ≈ 2600 Å3, Z = 2 f.u. The bromide (2), iodide (3) and thiocyanate (4) are isomorphous with [(Ph3P)3AgI], monoclinic, P21/n, a ≈ 19·1, b ≈ 14·0, c ≈ 17·7 Å, β ≈ 97°, Z = 4 f.u. In the chlorides, Ag–Cl are 2·494(5)–2·525(6) Å, with appreciably different Cl–Ag–As ranges (99·7(1)–114·3(1)° in the acetonitrile solvate; 104·8(2)–110·2(1)° in the 2,6-dimethylpyridine solvate) and more compact As–Ag–As distributions (overall range: 109·93(8)–113·26(3)°). For the bromide and iodide, Ag–X are 2·627(1) and 2·779(1) Å respectively, while for the thiocyanate Ag–S is 2·550(5) Å with Ag–S–C 104·2(3)°; the latter complexes also display wide ranges for many of the associated bonding parameters about the silver atom. The far-infrared spectra of [(Ph3As)3AgX] (X = Cl, Br, I) show v(AgX) bands at 217, 145 and 124 cm-1 respectively. The relationship between the v(AgX) wavenumbers and the Ag–X bond length r (AgX) is found to be the same as that for a range of AgX complexes with phosphine ligands, and is similar to that observed previously for analogous CuX complexes.

Metal Complexes of 1,3-Bis(Pyridin-2-yl)pyrazole: Spectral, Magnetic and Structural Studies

1995 ◽  
Vol 48 (6) ◽  
pp. 1071 ◽  
Author(s):  
AT Baker ◽  
DC Craig ◽  
G Dong ◽  
AD Rae
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Complex Cation ◽  
Tridentate Ligand ◽  
Structural Studies ◽  
Crystal Data ◽  
Octahedral Structure ◽  
Heterocyclic Ligands ◽  
X Ray ◽  
Donor Nitrogen

Bis(ligand)iron(II) and nickel(II) complexes of the asymmetric tridentate ligand 1,3-bis(pyridin-2-yl) pyrazole , L, have been prepared. The iron(II) complex, [FeL2] [PF6]2, is high-spin in the solid state over the temperature range 304-102 K, with a magnetic moment of 5.27 BM at room temperature. The crystal structure of bis (1,3-bis(pyridin-2-yl) pyrazole )iron(II) bis (hexafluorophosphate ) has been determined by single-crystal X-ray diffractometry. The compound crystallized as yellow prisms, with the structure being disordered in the tetragonal space group P421c with Z = 2. Crystal data a = b = 8.785(1) Ǻ, c = 19.804(6) Ǻ. The iron(II) centre is in an N6 environment, where the six donor nitrogen atoms are provided by the two tridentate heterocyclic ligands. The complex cation has an approximately octahedral structure exhibiting tetragonal compression. The observed Fe-N(pyridine) and Fe-N( pyrazole ) distances are 2.308(4) and 2.019(7) Ǻ respectively, with the Fe-N(pyridine) distance being the longest observed to date.

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