Iodinated Metallacrowns: Toward Combined Bimodal Near-Infrared and X-Ray Contrast Imaging Agents

Multimodal probes capable of combining imaging modalities within a single molecule are in high demand today as they can provide information at both molecular and anatomical levels. Herein, a study was conducted on a series of gallium(III)/lanthanide(III) bis(12-MC-4) metallacrowns (MCs) with the general composition {Ln[12-MC_Ga^III_N(shi)-4]}₂(iph)₄ ( Ln-I _x , x=0, 4, 8, 12), where shi and iph are salicylhydroximate and isophthalate ligands, respectively, or their iodinated derivatives. For Yb-I _x , the attenuation in X-ray computed tomography (XCT) imaging and near-infrared (NIR) luminescence properties can be finely tuned by controlled structural modifications based on iodo groups. Solutions of Yb-I _x appear to be 22–40 times more efficient as XCT agents in comparison to the commercially available iobitridol, while providing an intense emission signal in the NIR range with total quantum yields up to 8.6 %, which are among the highest values reported so far. Therefore, these molecules are promising potential bimodal agents for combined NIR luminescence and XCT imaging.     

[Ga3+8Sm3+2, Ga3+8Tb3+2] Metallacrowns are Highly Promising Ratiometric Luminescent Molecular Nanothermometers Operating at Physiologically Relevant Temperatures

Nanothermometry is the study of temperature at the submicron scale with a broad range of potential applications, such as cellular studies or electronics. Molecular luminescent-based nanothermometers offer a non-contact means to record these temperatures with high spatial resolution and thermal sensitivity. A luminescent-based molecular thermometer comprised of visible-emitting Ga³⁺/Tb³⁺ and Ga³⁺/Sm³⁺ metallacrowns (MCs) achieved remarkable relative thermal sensitivity associated with very low temperature uncertainty of S_r=1.9 % K⁻¹ and δT<0.045 K, respectively, at 328 K, as an aqueous suspension of polystyrene nanobeads loaded with the corresponding MCs. To date, they are the ratiometric molecular nanothermometers offering the highest level of sensitivity in the physiologically relevant temperature range.     

Semi-interpenetrated polymer networks based on modified cellulose and starch as gel polymer electrolytes for high performance lithium ion batteries

Cellulose - Poly(ethylene oxide) (PEO) is one of the most famous polymer electrolytes; however, its low conductivity and capacity have prevented its commercial applications. This study utilizes...     

Structure and electrochemical properties of composite films based on poly-3,4-ethylenedioxythiophene with metallic palladium inclusions

The electrochemical behavior of PEDOT/Pd composite films obtained by the chemical deposition of ultradisperse Pd particles in the poly-3,4-ethylenedioxythiophene (PEDOT) polymer matrix was studied. The structure of the films was determined by electron microscopy and energy-dispersion X-ray fluorescence analysis. The electrochemical properties of PEDOT/Pd composite films in solutions containing hydrogen peroxide was also studied. Special attention was paid to the effect of the time of the chemical deposition of palladium in the polymer structure on the electroreduction of hydrogen peroxide in phosphate buffer solutions.     

A self-assembled complex with a titanium(IV) catecholate core as a potential bimodal contrast agent

A ditopic chelating ligand (H(6)4) that bears catechol and diethylenetriamine-N,N,N',N',N'-pentaacetate (DTPA) has been designed and shown to specifically bind lanthanide(III) ions at the DTPA core ([Ln(H(2)4)(H(2)O)](-)) and further self-assemble with titanium(IV), thereby giving rise to the formation of a supramolecular metallostar complex with a lanthanide(III)-to-titanium(IV) ratio of 3:1, [(Ln4)(3)Ti(H(2)O)(3)](5-) (Ln=La, Eu, Gd). The efficacy of the metallostar complex as a potential bimodal optical/magnetic resonance imaging (MRI) agent has been evaluated. Nuclear magnetic relaxation dispersion (NMRD) measurements for the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex have demonstrated an enhanced r(1) relaxivity that corresponds to 36.9 s(-1) mM(-1) per metallostar molecule at 20 MHz and 310 K, which is a result of a decreased tumbling rate. The ability of the complex to bind to human serum albumin (HSA) was also examined by relaxometric measurements. In addition, upon UV irradiation the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex exhibits broad-band green emission in the range 400-750 nm with a maximum at 490 nm. Taking into account the high relaxivity and luminescence properties, the [(Gd4)(3)Ti(H(2)O)(3)](5-) complex is a good lead compound for the development of efficient bimodal contrast agents.     

Using Native Chemical Ligation for Site-Specific Synthesis of Hetero-bis-lanthanide Peptide Conjugates: Application to Ratiometric Visible or Near-Infrared Detection of Zn2+

The interest in ratiometric luminescent probes that detect and quantify a specific analyte is growing. Owing to their special luminescence properties, lanthanide(III) cations offer attractive opportunities for the design of dual-color ratiometric probes. Here, the design principle of hetero-bis-lanthanide peptide conjugates by using native chemical ligation is described for perfect control of the localization of each lanthanide cation within the molecule. Two zinc-responsive probes, r-LZF1^Tb|Cs124|Eu and r-LZF1^Eu|Cs124|Tb are described on the basis of a zinc finger peptide and two DOTA (DOTA=1,4,7,10-tetraaza-cyclododecane-1,4,7,10-tetraacetic acid) complexes of terbium and europium. Both display dual-color ratiometric emission in response to the presence of Zn²⁺. By using a screening approach, anthracene was identified for the sensitization of the luminescence of two near-infrared-emitting lanthanides, Yb³⁺ and Nd³⁺. Thus, two novel zinc-responsive hetero-bis-lanthanide probes, r-LZF3^Yb|Anthra|Nd and r-LZF3^Nd|Anthra|Yb were assembled, the former offering a neat ratiometric response to Zn²⁺ with emission in the near-infrared around 1000 nm, which is unprecedented.     

Chromatography-mass spectrometry studies of transarylation and disproportionation reactions of diaryl telluroxides

Electrospray ionization chromatography-mass spectrometry was used to study transarylation and disproportionation reactions of di(4-methoxyphenyl) and di(4-dimethylaminophenyl) telluroxides in refluxing toluene. The reaction mixture compositions were established based on the mass spectrometry data and relative retention times. General schemes for fragmentation of the reaction mixture components were suggested.     

Theoretical study of the structure and properties of complexes formed by lithium and a boron α sheet

The ability of lithium to form complexes with a boron α sheet and the occurrence of ionic conduction in the compounds formed were evaluated using quantum-chemical methods. The obtained materials were established to be stable, and the weight fraction of lithium can reach 0.32. It was concluded that a low potential barrier for migration of lithium ions over the surface indicates the presence of ionic conduction.     

Reactions of pentachloropyridine with organomagnesium compounds

4-Alkyltetrachloropyridines were obtained by the interaction of pentachloropyridine with halogenated magnesium alkyl compounds in an ether-tetrahydrofuran solution.