NMR studies of mixed-ligand lanthanide complexes. Reaction of ?-diketonates of the yttrium subgroup with 18-crown-6

Babailov, Sergey P.; Kriger, Yu. G.; Martynova, T. N.; Nikulina, L. D.

doi:10.1007/bf00743578

Cited by 6 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Both dependences in coordinates LIS versus inverse temperature value (1/ T ) can be approximated by linear anamorphose. This result is similar to that of earlier investigated complexes of [Ho(H 2 O)(EDTA 4– )] − , , [Tb(H 2 O)(EDTA 4– )] − , , [Ln(18-crown-6)(ptfa) 2 ] + , ,− [Ln(diaza-18-crown-6)(NO 3 ) 3 ], [Ln(18-crown-6)(NO 3 ) 3 ], ,, and [LnH(oep)(tpp)], , where ptfa is 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, tpp is tetraphenylporphyrin, and oep is octaethylporphyrin. From the slopes of both curves, one can conclude that these dependences are substantial.…”

Section: Resultssupporting

confidence: 90%

“…The rate constants of intramolecular dynamics were evaluated by the complete band-shape method for a two-site exchange ,,− in the following procedure. LIS values in the intermediate and fast-exchange regions were extrapolated from the low-temperature range using the Curie–Weiss model. , Assuming that there are two conformers, Δ-λ E -δδδδ and Δ-δ E -δδδδ, that are in exchange, the observed average LIS value is given as normalΔ δ av = p λ normalΔ δ λ + p δ normalΔ δ δ where Δδ λ and Δδ δ are the intrinsic LISs in the absence of exchange and p λ and p δ are the molar fractions of the isomers.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Lanthanides as NMR Probes of Fast Molecular Dynamics at High Magnetic Fields and Temperature Sensors: Conformational Interconversion of Erbium Ethylenediaminetetraacetate Complexes

et al. 2013

View full text Add to dashboard Cite

(1)H NMR measurements are reported for D2O solutions of paramagnetic complex [Er(H2O)(EDTA(4-))](-) (I) for temperature interval 273-319 K. Diamagnetic complex [Lu(H2O)(EDTA(4-))](-) (II) was used as an NMR reference compound. The spectra obtained have been analyzed using a band-shape analysis technique in the framework of dynamic NMR (DNMR) taking into account the temperature dependence of lanthanide-induced shifts. Intramolecular dynamics in I was assigned to the interconversion of Δ-λE-δδδδ and Δ-δE-δδδδ conformers with estimated activation free energy ΔG(‡)(298 K) = 50 ± 4 kJ/mol. The methodology of paramagnetic 4f-element probe applications on the example of Er(3+) for the study of free-energy changes in chemical exchange processes, as well as the advantages of this method in comparison with DNMR studies of diamagnetic substances, is discussed. In accordance with the literature reviewed, the fulfilled experimental study is the first example of intramolecular dynamics determination for erbium complexes. An additional advantage of the investigation is in the approach proposed which extends the range of measurement of the NMR rate constants for paramagnetic 4f-element complexes compared to diamagnetic ones. Coordination compounds investigated represent a new type of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solutions.

show abstract

Section: Resultssupporting

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Lanthanides as NMR Probes of Fast Molecular Dynamics at High Magnetic Fields and Temperature Sensors: Conformational Interconversion of Erbium Ethylenediaminetetraacetate Complexes

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Analysis of the temperature dependence of paramagnetic LISs of I in Fig. shows that it is substantial and well approximated by a linear anamorphose of the inverse temperature value (1/ T ) (like for [Ln(18‐crown‐6)(ptfa) 2 ] + , [Ln(diaza‐18‐crown‐6)(NO 3 ) 3 ], [Ln(18‐crown‐6)(NO 3 ) 3 ], and [LnH(oep)(tpp)], where Ln = La‐Eu, ptfa is 1,1,1‐trifluoro‐5,5‐dimethyl‐2,4‐hexanedione, tpp is tetraphenylporphyrin, and oep is octaethylporphyrin).…”

Section: Resultsmentioning

confidence: 97%

Intermolecular dynamics and paramagnetic properties of ethylenediaminetetraacetate complexes with the yttrium subgroup rare earth elements using nuclear magnetic resonance

Babailov

2012

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

(1)H nuclear magnetic resonance (NMR) measurements are reported for the D(2)O solutions of [Ln(3+)(EDTA(4-))](-) complexes, where EDTA(4-) is ethylenediaminetetraacetate anion, Ln(3+) = Tb(3+) (I), Ho(3+) (II), Tm(3+) (III), Yb(3+) (IV) and Lu(3+) (V). Temperature dependencies of the (1)H NMR spectra of paramagnetic I-IV have been analyzed using the dynamic NMR methods. It is found that the activation free energies (ΔG(‡)(298)) of the intermolecular EDTA ions exchange at [Ln(3+) (EDTA(4-))](-) complexes are 60±3 (I), 66±3 (II), 69±3 (III) and 74±3 (IV) kJ/mol (at pD = 7). A monotonic increase of the free energy of chemical exchange processes along the series of lanthanide [Ln(3+) (EDTA(4-))](-) complexes is probably related to the lanthanide contraction. The obtained results indicate that coordination compounds I-IV may be considered as thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution.

show abstract

“…During the last decades, an increase in the number of publications devoted to the molecular structure and to the dynamics of the rare-earth coordination compounds has been observed. − The information about the molecular structure and the dynamics of the rare-earth coordination compounds in solutions underlies the existing technologies for photoresist production in microelectronics, sensitizers for photodynamic therapy, contrast reagents for magnetic resonance imaging (MRI), synthetic models of natural ionofores, and sensors for biology and medicine. Studies of the paramagnetic chemical shifts in NMR spectra allow us to gain qualitative and quantitative information about the molecular structure as well as the kinetic and thermodynamic stability of paramagnetic complexes in solutions. − …”

Section: Introductionmentioning

confidence: 99%

Lanthanide Paramagnetic Probes for NMR Spectroscopic Studies of Fast Molecular Conformational Dynamics and Temperature Control. Effective Six-Site Proton Exchange in 18-Crown-6 by Exchange Spectroscopy

Babailov

2012

Inorg. Chem.

View full text Add to dashboard Cite

(1)H and (13)C NMR measurements are reported for the CDCl(3) and CD(2)Cl(2) solutions of [La(18-crown-6)(NO(3))(3)] (I), [Pr(18-crown-6) (NO(3))(3)] (II), [Ce(18-crown-6)(NO(3))(3)] (III), and [Nd(18-crown-6)(NO(3))(3)] (IV) complexes. Temperature dependencies of the (1)H NMR spectra of paramagnetic II-IV have been analyzed using the dynamic NMR (DNMR) methods for six-site exchange. Two types of conformational dynamic processes were identified (the first one is conditioned by interconversion of complex enantiomeric forms and pseudorotation of a macrocycle molecule upon the C(2) symmetry axis; the second one is conditioned by macrocycle molecule inversion). Application of exchange spectroscopy (2D-EXSY) of DNMR for investigation of this dynamic system (II-IV) simplifies the assignment of the NMR signals and represents the first experimental study of multisite exchange. In the present work, the methodology of paramagnetic 4f (Ce, Pr, and Nd) probe applications for the study of free-energy, enthalpy, and entropy changes in chemical exchange processes, as well as the advantages of this method in a comparison with DNMR studies of diamagnetic substances, is discussed. In particular, as a result of paramagnetic chemical shifts in 4f complexes, the range of measurable rate constants expands considerably compared to the analogous range in diamagnetic compounds. Coordination compounds investigated in the paper represent new types of thermometric NMR sensors and lanthanide paramagnetic probes for in situ temperature control in solution.

show abstract

NMR studies of mixed-ligand lanthanide complexes. Reaction of ?-diketonates of the yttrium subgroup with 18-crown-6

Cited by 6 publications

References 4 publications

Lanthanides as NMR Probes of Fast Molecular Dynamics at High Magnetic Fields and Temperature Sensors: Conformational Interconversion of Erbium Ethylenediaminetetraacetate Complexes

Lanthanides as NMR Probes of Fast Molecular Dynamics at High Magnetic Fields and Temperature Sensors: Conformational Interconversion of Erbium Ethylenediaminetetraacetate Complexes

Intermolecular dynamics and paramagnetic properties of ethylenediaminetetraacetate complexes with the yttrium subgroup rare earth elements using nuclear magnetic resonance

Lanthanide Paramagnetic Probes for NMR Spectroscopic Studies of Fast Molecular Conformational Dynamics and Temperature Control. Effective Six-Site Proton Exchange in 18-Crown-6 by Exchange Spectroscopy

Contact Info

Product

Resources

About