An electron spin resonance study of coordination modes in the copper(II)–histamine and copper(II)–l-histidine systems in fluid aqueous solution

Szabó-Plánka, Terézia; Rockenbauer, Antal; Korecz, L.; Nagy, Dorottya

doi:10.1016/s0277-5387(00)00364-8

Cited by 49 publications

(52 citation statements)

References 25 publications

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“…In both species an octahedral distorted coordination ge- 2ϩ complex in equimolar Cu(II)-Hm solution at basic pH. 9,13 Upon Cu(II) addition at pH 6, the Raman spectrum showed some peaks (i.e., at 1590 cm Ϫ1 ), due to the neutral imidazole moiety, in addition to a weak shoulder at 1618 cm Ϫ1 , which is related to the charged imidazole ring (Fig. 2, spectrum C, and Table I).…”

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“…ESR studies on Cu(II)-Hm equilibrium aqueous systems also showed the presence of these two monomeric species under slightly acidic conditions. 9,11 By preparing the Cu(II)-Hm complex [Cu-(ClO 4 ) 2 /Hm ϭ 0.5] in alcoholic solution, it was possible to carry out the Raman measurements on the precipitate after filtration and on the supernatant solution after lyophilization. In both Raman spectra the bands attributable to tautomer I (e.g., 1585 and 1276 cm…”

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Raman and IR study on copper binding of histamine

et al. 2003

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A comparative Raman and FTIR study of histamine (Hm), a small hormone present in a wide selection of living organisms, and its complexes with copper(II) at different pH values was carried out. Both the Raman and IR spectra present some marker bands useful for the identification of the structure of the species predominating in the Cu(II) aqueous and alcoholic systems. In particular, Raman spectroscopy appears to be a useful tool for analyzing the tautomeric equilibrium of the imidazole ring of Hm, because some bands (i.e., nuC(4)dbond;C(5)) appear at different wavenumbers, depending on whether the imidazole moiety is in the N(tau)-H (tautomer I) or N(pi)-H (tautomer II) protonated form. In aqueous solutions the manner in which Hm binds to Cu(II) depends on the pH. At basic pH the most relevant species formed are a dimer, [Cu(2)L(2)H(-2)](2+), and a monomeric complex, [CuL](2-) or [CuL(2)](+). On the contrary, by decreasing the pH, Hm acts as a mono- or bidentate ligand, giving rise to two types of monomeric complexes, [CuLH](2-) and [CuL](2-) or [CuL(2)](+). With respect to the Cu(II)-Hm alcoholic system, both the aminic group and the imidazole ring (tautomer I) take part in the Cu(II) coordination, leading to the formation of the [CuL](2-) or [CuL(2)](+) monomeric complex.

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Raman and IR study on copper binding of histamine

et al. 2003

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“…[30,31] The resolved superhyperfine lines in the spectra also depend on the rotational correlation time, τ θ . [24,32] A negligible influence of the anisotropic components (a Nʈ and a NЌ ) of the superhyperfine coupling tensor can be determined from spectrum c. [33,34] Well resolved superhyperfine lines suggest that the copper and nitrogen atoms are positioned in the equatorial plane of the copper() coordination sphere. The spectra of the complex dissolved in CD 3 OD which are characterised by different EPR parameters (Table 1), albeit with the similar τ θ values [24,32] as in CDCl 3 , show five much broader superhyperfine lines in the whole temperature range studied.…”

Section: A) Epr Analysismentioning

confidence: 99%

Conformational Analysis of Bis(L‐N,N‐dimethylvalinato)copper(II) and Bis(L‐N,N‐dimethylleucinato)copper(II) in Different Solvents by EPR Spectroscopy and a Molecular Mechanics Study

2004

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An EPR study on the Brownian motion of bis(L‐N,N‐dimethylvalinato)copper(II), Cu(L‐Me2Val)2 and bis(L‐N,N‐dimethylleucinato)copper(II), Cu(L‐Me2Leu)2, dissolved in different solvents (CD3OD, CH3CH2OH, CDCl3) as a function of temperature is presented. The theoretical fits of the EPR spectra revealed different EPR behaviour for the two copper(II) complexes in hydrogen bond making solvents. In order to examine whether the different behaviour could be explained on conformational (steric) grounds, a conformational analysis of the copper(II) complexes with L‐N,N‐dimethylated amino acids was performed with a molecular mechanics force field. The ability of the most stable conformations to bind a water molecule in the copper(II) first coordination sphere was also examined using the force field. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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“…Later, mass spectrometric experiments were performed to investigate different 1:1 complexes of copper and other metals with histidine [28]. Copper histidine complexes of 1:1, 1:2 and 2:2 stoichiometries were identified also by electron spin resonance spectroscopy [29].…”

Section: Introductionmentioning

confidence: 99%

“…This holds in particular for separation based methods, because an excess of free ligand is usually separated from metal species during separation (changing the metal to ligand ratio), and also the effective pH may change considerably when organic modifiers (such as methanol in RP or acetonitrile in HILIC) are used. Moreover, and unlike the situation of stable phytosiderophore or nicotianamine chelates which exist always in 1:1 stoichiometry, for iron citrate and copper histidine several stoichiometries and charge states must be considered [21,29] In the last years hydrophilic interaction chromatography (HILIC) has been employed successfully for the separation of metal species by several research groups [9][10][11]23]. It enables new separation possibilities due to the fact that the HILIC partitioning mechanism (as already proposed by Alpert [30]) displays only weak, but very effective, interactions with potentially labile metal species.…”

Section: Introductionmentioning

confidence: 99%