In this study, NMR spectroscopy was used to investigate the temperature dependences of paramagnetic chemical shifts in a 22% solution of poloxamer 407 with and without the addition of the [Dy(DTPA)]2− complex. The half-width of the polymer signals in the system with the paramagnetic additive depends significantly on the solution viscosity and temperature due to the Curie-spin contribution to the paramagnetic spin-spin relaxation rate enhancement. The [Dy(DTPA)]2−complex can be considered as a promising compound for the design of temperature-sensitive NMR probes aimed at determining local temperature and viscosity in aqueous media and dispersed systems.

The applicability, peculiarities, and progress of the high resolution 1H, 13C, and 15N NMR spectroscopy for elucidating the spin crossover phenomenon were shown. The results obtained by the NMR method are compared with the results found by other physicochemical methods. Though, the coordination environment in a solution can change significantly compared with a solid state. As a result, the magnetic properties of the complex as a whole can also vary significantly. NMR is quite possible to study such systems, extracting a lot of useful information about the properties of complexes in solution. The use of NMR spectroscopy makes it possible to estimate the structural and dynamic peculiarities of complexes possessing a spin crossover. In addition, the presence of a “magnetic response” to changing external conditions provides opportunities for targeted design of NMR sensor systems.

Detecting harmful pathogens in food is not only a crucial aspect of food quality management but also an effective way to ensure public health. In this paper, a complete nuclear magnetic resonance biosensor based on a novel gadolinium (Gd)-targeting molecular probe was developed for the detection of Salmonella in milk. First, streptavidin was conjugated to the activated macromolecular polyaspartic acid (PASP) via an amide reaction to generate SA-PASP. Subsequently, the strong chelating and adsorption properties of PASP toward the lanthanide metal gadolinium ions were exploited to generate the magnetic complex (SA-PASP-Gd). Finally, the magnetic complex was linked to biotinylated antibodies to obtain the bioprobe and achieve the capture of Salmonella. Under optimal experimental conditions, the sensor we have constructed can achieve a rapid detection of Salmonella within 1.5 h, with a detection limit of 7.1 x 10(3) cfu mL(-1).

The relaxation properties of the [Dy(H2O)n(CyDTA)]− complex were studied by 1H NMR using methods based on the analysis of spin–spin relaxation rates.

H-1 NMR measurements are reported for the C6D6 solution of the complex bis(tris(tert-butyl)cyclopentadienyl)neodymium(iii) iodide [Cp ''' 2NdI] {where Cp ''' = 1,3,4-tris(tert-butyl)cyclopentadienide}. Temperature dependences of the 1H NMR spectra of the complex have been analyzed using the bandshape analysis, taking into account the temperature variation of the paramagnetic chemical shifts, within the frame of the dynamic NMR method. The conformational dynamics of the complex are conditioned by the process of racemization (with the value of the Gibbs activation energy Delta G(298)double dagger= 58 +/- 3 kJ mol(-1)). Due to the substantial temperature dependence of the paramagnetic shifts, the complex is essentially an NMR thermosensor reagent for local temperature monitoring. Good agreement between the calculated and experimental lanthanide-induced paramagnetic shifts in the H-1 NMR spectra indicates the similarity of the structure of the complex in a solution of C6D6 and the structure in the crystalline phase, found from the data of the X-ray structural study of the similar complex.

NMR spectroscopy was applied to study the temperature dependences of paramagnetic chemical shifts of the [Co(EDTA)]2− complex (1) in D2O solution and in 10

The synthesis, crystal structure and NMR-study of new paramagnetic Er (III) complex based on imine derivatives of thiacalix[4]arene was carried out. Temperature dependences of the 1H NMR spectra of complex Er(III) and calix[4]arene with N-contained substituents (I) have been analyzed using the line shape analysis, taking into account the temperature variation of paramagnetic chemical shifts, within the frame of the dynamic NMR method. Two kinds of molecular dynamics in I are reported for the CDCl3 solution. The first one conformational dynamics is conditioned by the pinched cone A <-> pinched cone B interconversion with activation free energy Delta G not equal(298 K) = 40 +/- 3 kJ/mol (observed at low temperature). The second one dynamics is connected with rearrangements in coordination environment (with Delta G not equal(298 K) = 58 +/- 3 kJ/mol). Due to substantial temper-ature dependence of paramagnetic shifts, the complex I can be considered as NMR thermosensor reagent for local temperature monitoring. Owing to the large magnetic moments typical for many Ln-ions and especially high value of magnetic anisotropy for Er cation (III) adopting capped trigonal prismatic geometry of coordination sphere one may expect that 1-Er can potentially exhibit SMM behavior.

Kinetic and energy characteristics of reversible intermolecular processes for [Pr(DPM) 3 ], [Pr(DPM) 3 (18-crown-6)], and [(Pr(DPM) 3 ) 2 (18-crown-6)] complexes in the CDCl 3 solution (DPM=dipivaloylmethane anion) are characterized by dynamic 1 H NMR.

The conformational dynamics of the paramagnetic complex [Dy(H2O)n(DOTA)](-) has been studied by dynamic H-1 NMR within the framework of the signal bandshape analysis technique taking into account the temperature variation of the lanthanide-induced shifts (LIS). The corresponding values of the free energy of activation Delta G(dagger)298 were 68 kJ/mol for the SAP -> TSAP transformation process, and 60 kJ/mol for the reverse transition (TSAP -> SAP). In the series of [Ln(H2O)n(DOTA)]- complexes from praseodymium to lutetium, there is first a monotonic increase in the free energy of activation Delta G(not equal)298 of the conformational transition up to Dy, then there is a gradual decrease in the activation barrier (as a manifestation of the gadolinium break effect).

Paramagnetic chemical shifts in the iron(II) tris(pyrazole-1-yl)methane [Fe(HC(Pz)3)2](C10H7SO3)2 complex exhibiting spin crossover were studied by 1H NMR at different temperatures. The studied complex demonstrates a relatively sharp temperature change of NMR chemical shifts due to spin crossover. Complex [Fe(HC(Pz)3)2](C10H7SO3)2 can be considered a promising compound for the design of thermally sensitive shift and relaxation NMR probes utilized for local temperature measurements in aqueous media and for advanced MRI diagnostics.

The temperature dependences of paramagnetic chemical shifts in the lanthanide complexes with diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid [Ln(H2O)(DTPA)]2− (Ln = Pr, Dy, Ho, Yb) were studied by NMR spectroscopy. The dysprosium complex demonstrated the highest temperature sensitivity of chemical shifts d(δexp)/dT equal to 1.46 ppm K−1 at T = 306 K. The [Dy(H2O)(DTPA)]2− complex can be considered as the most promising thermosensor reagent for determining the local temperature in aqueous media and for advanced MRI diagnosis of diseases.

The structure and paramagnetic properties of the [Dy(H2O)n(CyDTA)]– complex are studied by 1H NMR using the analysis of paramagnetic shifts and spin-spin relaxation rates for an ab initio structural model. It is shown that significant temperature-dependent spectral line broadening is due to the Curie-spin contribution to the paramagnetic spin-spin relaxation rate enhancement. The complex demonstrates conformational, kinetic, and thermodynamic stability in the temperature range from 278 K to 368 K. The maximum temperature sensitivity of chemical shifts d(δexp)/dT is equal to 0.44 ppm/K. Due to its thermodynamic and conformational stability, this compound may be prospective for the design of thermally sensitive NMR probes in aqueous media.

The temperature dependence of the lanthanide-induced chemical shifts (LISs) was studied for the systems containing 1-palmitoyl-2-oleoylphosphatidylcholine (POPC)-Ho, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-Ho and 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC)-Ho in unilamellar liposomes. In the POPC-Ho system, anti-Curie dependence of LISs is observed, same as previously observed in POPC-Pr system. In the DPPC- and DMPC-Ho systems, temperature features are observed which are probably connected with phase transition.

The relaxation properties of the [Dy(H 2 O) n (CyDTA)] - complex were studied by 1 H NMR using methods based on the analysis of spin-sin relaxation rates. It is found that a significant temperature-dependent broadening of the NMR signals is due to the presence of the Curie-spin contribution to the increase in the spin-spin relaxation rate (both on nuclei of ligands and residual protons of D 2 O). This compound can be used for the design of thermosensitive NMR probes aimed at determining the local temperature in aqueous media and advanced diagnostics of diseases using MRI technologies.

Temperature dependences of paramagnetic chemical shifts in NMR spectra of lanthanide tris-phthalocyaninates Ln2[(15C5)4Pc]3(where [(15C5)4Pc][Formula: see text] is 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninate dianion, Ln = Ho(III), Tm(III)) have been studied in the physiological temperature range (from 303 to 323 K). The observed maximum temperature sensitivity [Formula: see text]/dT turns out to be 0.25 ppm/K for the signals of the thulium complex and 0.16 ppm/K for the holmium complex. By the example of Tm2[(15C5)4Pc]3, it has been shown that the use of temperature sensitivities normalized to signal half-widths (∣CT∣/[Formula: see text] is expedient to judge the applicability of the observed temperature dependences of LISs of analogous lanthanide complexes (Ln = Tb, Dy, Ho, Tm) for determining temperatures. The investigated kinetically and thermodynamically stable Ln2[(15C5)4Pc]3complexes can be considered promising for the design of thermosensitive NMR probes for determination of the local temperature in nonpolar solutions.

The sensitivity of Ho–phospholipid complexes to changes in the membrane viscosity of liposomes was checked. An increase in viscosity was observed for DPPC and DMPC near the phase-transition temperature. Ho–phospholipid complexes could be used as sensors of local membrane viscosity in NMR and MRI technologies.

The detailed knowledge about the structure of multinuclear paramagnetic lanthanide complexes for the targeted design of these compounds with special magnetic, sensory, optical and electronic properties is a very important task. At the same time, establishing the structure of such multinuclear paramagnetic lanthanide complexes in solution, using NMR is a difficult task, since several paramagnetic centers act simultaneously on the resulting chemical shift of a particular nucleus. In this paper, we have demonstrated the possibility of molecular structure determination in solution on the example of binuclear triple-decker lanthanide(III) complexes with tetra-15-crown-5-phthalocyanine Ln2[(15C5)4Pc]3 {where Ln = Tb (1) and Dy (2)} by quantitative analysis of the pseudo-contact lanthanide-induced shifts (LIS). The symmetry of complexes was used for the simplification of the calculation of pseudo-contact shifts on the base of the expression for the magnetic susceptibility tensor in the arbitrary oriented magnetic axis system. Good agreement between the calculated and experimental shifts in the 1H NMR spectra indicates the similarity of the structure for the complexes 1 and 2 in solution of CDCl3 and the structure in the crystalline phase, found from the data of the X-ray structural study of the similar complex Lu2[(15C5)4Pc]3. The described approach can be useful for LIS analysis of other polynuclear symmetric lanthanide complexes.

1H NMR measurements are reported for the CD2Cl2/CDCl3 solutions of the Co(II) calix[4]arenetetraphosphineoxide complex (I). Temperature dependences of the 1H NMR spectra of I have been analyzed using the line shape analysis, taking into account the temperature variation of paramagnetic chemical shifts, within the frame of the dynamic NMR method. Conformational dynamics of the 2:1 Co(II) calix[4]arene complexes was conditioned by the pinched cone ↔pinched cone interconversion of I (with activation Gibbs energy ΔG≠(298K) = 40 ± 3 kJ/mol. Due to substantial temperature dependence of paramagnetic shifts, complex I can be used as model compound for designing an NMR thermosensor reagent for local temperature monitoring.

The search for efficient methods of comparative structural investigations of coordination compounds in solid state and solutions is a very relevant task. In this study, structural assignments in a series of Ln2[(15C5)4Pc]3 complexes (where [(15C5)4Pc]2- is 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato-dianion, Ln = Nd3+, Tb3+, Dy3+, Ho3+, Er3+ and Tm3+) was performed using NMR relaxation and paramagnetic lanthanide-induced shifts (LIS) data. Analysis of the paramagnetic chemical shifts and relaxation rates evidenced of isostructurality of the complete series of the investigated triple-decker complexes in the solutions. The performed systematic DFT calculations for a series of model complexes with methoxy-substituted ligands Ln2[(MeO)8Pc]3 demonstrate that the calculated geometrical factors are in agreement with characteristics extracted from experimental NMR data.

The paramagnetic, thermosensory, and molecular dynamic properties of the [Ln(H2O)n(EDTA)]– (Ln = Pr, Eu, Tb, Ho, Er, Tm) complexes were studied by 1H NMR. The maximum temperature sensitivity of paramagnetic chemical shifts d(δexp)/dT turned out to be 0.48 ppm/K for the Tb complex. It was found that the intramolecular dynamics is due to the inversion of the ethylene cycle and the concerted reorientation of the acetate groups. The value of the activation barrier found for the europium complex turned out to be Δ G_298^ = 49 ± 3 kJ/mol. The [Ln(H2O)n(EDTA)]– complexes can be considered as promising compounds for the design of thermosensitive NMR probes aimed at determining the local temperature in aqueous media.