Synthesis and characterization of a stable paramagnetic hexacoordinated oxochromium(IV) complex with dianionic tetradentate schiff base ligand salen

A paramagnetic octahedral oxochromium(IV) complex with dianionic tetradentate ligand salen (where H2salen is N,N'-bis(salicylidene)-1,2-ethylenediamine) has been synthesized. This compound [CrO(OH2)(salen)] (1) is characterized by elemental analysis, magnetic moment measurement, IR, UV-Vis and EPR spectroscopic studies. Measured room temperature (RT) magnetic moment value is 2.96 BM for 1 indicates a d2 system with a triplet ground state. The magnetic moment value rules out a large spin-orbit coupling. The RT and LNT powder EPR spectra of 1 in X-band clearly shows two lines, one around g = 1.965 and the other with larger intensity at g = 4.26 ± 0.10. The first line at g = 1.965 corresponds to the |0> ↔ |± 1> transition from the Kramers doublet |± 1>, while the broad and intense line at low field with the g-value of 4.26 ± 0.10 is due to the forbidden transition |-1> ↔ |+1>. Compound 1 displays two successive reductions at -0.76 and -1.63 V (versus Ag/AgCl), respectively, while it undergoes only one irreversible oxidation as evident from the well-defined anodic wave at +1.48 V in its cyclic voltammogram

Electronic structure of thiaporphyrins: an X-ray photoelectron spectroscopic study

The electronic structure of 5,10,15,20-tetraphenylporphyrin (H<SUB>2</SUB>tpp) modified with one and two sulfur core atoms has been investigated by X-ray photoelectron spectroscopy (XPS). The nitrogen Is binding energies (b.e.s) were excellent sensors of the electronic effects of the core-modified porphyrins. They clearly show that there is an increase in electron density on the core nitrogen atoms when the two NH groups in H<SUB>2</SUB>tpp are replaced by sulfur atoms, the nitrogen 1s b.e. decreasing by about 1.5 eV. The carbon 1s core level also decreases in b.e. on core modification with sulfur atoms. The results obtained are in good agreement with those from UV/VIS, fluorescence spectroscopy, electrochemical studies, X-ray diffraction and extended-Hückel calculations. They indicate that there is an interaction between the nitrogen and sulfur atoms and a mechanism is suggested for it. No evidence was found for interaction among sulfur atoms and the participation of their d orbitals in the electronic structure. Copper and nickel complexes of the monothiaporphyrin were also subjected to XPS analysis

Effect of nitrogen dioxide on the EPR property of lithium octa-n-butoxy 2,3-naphthalocyanine (LiNc-BuO) microcrystals

Lithium octa-n-butoxy-naphthalocyanine (LiNc-BuO) is a stable free radical that can be detected by electron paramagnetic resonance (EPR) spectroscopy. Previously we have reported that microcrystals of LiNc-BuO exhibit a single sharp EPR peak, whose width varies linearly with the partial pressure of paramagnetic molecules such as oxygen and nitric oxide. In this report, we present the effect of nitrogen dioxide (NO2), which is also a paramagnetic molecule, on the EPR properties of LiNc-BuO. The gas-sensing property of LiNc-BuO is attributed to the open molecular framework of the crystal structure which is arranged with wide channels capable of accommodating large molecules such as NO2. The EPR linewidth of LiNc-BuO was highly sensitive to the partial pressure of NO2 in the gas mixture. The line-broadening was quick and reversible in the short-term for low concentration of NO2. However, the EPR signal intensity decreased with time of exposure, apparently due to a reaction of NO2 with LiNc-BuO crystals to give diamagnetic products. The results suggested that LiNc-BuO may be a useful probe for the determination of trace amounts of NO2 using EPR spectroscopy

Synthesis and characterization of two stable paramagnetic octahedral chromium(IV) complexes with dianionic tridentate SNO donor ligands and of a chromium(III) complex with a ONO donor ligand

Two novel paramagnetic octahedral chromium(IV) complexes with dianionic tridentate SNO donor ligands containing extended p-system have been synthesized while only a paramagnetic octahedral chromium(III) complex is obtained when a related dianionic tridentate ONO donor ligand is used under similar conditions. These bischelate complexes [Cr(abtsal)2] (1) (abtsalH2 is the Schiff base of o-aminobenzenethiol and salicylaldehyde), [Cr(4-PhTSCsal)2] &#183; H2O (2) (4-PhTSCsalH2 is the Schiff base of 4-phenylthiosemicarbazide and salicylaldehyde) and K[Cr(sap)2]&#183; H2O (3) (sapH2 is the tridentate Schiff base of salicylaldehyde and o-aminophenol) are characterized by elemental analyses, magnetic moment measurements, IR, UV-Vis and EPR spectroscopic studies. Compound 3 has been structurally characterized by X-ray crystallography. Measured room temperature (RT) magnetic moment values are 2.98 BM for 1 and 2.83 BM for 2 indicating a d2 system with a triplet ground state in both the cases. On the other hand, the magnetic moment value for 3 is found to be 3.74 BM at RT and is consistent with the presence of three unpaired electrons for a d3 Cr(III) ion. The magnetic moment values rule out the large spin-orbit coupling which is substantiated by the presence of RT EPR signals. Compounds 1 and 2 exhibit very similar powder EPR spectra at RT and LNT, which show the allowed transition &#916;Ms = &#177;1 (g = 2.004 for both 1 and 2) as well as the "forbidden" half-field transition (&#916;Ms = &#177;2) at g = 4.105 for 1 and g = 4.318 for 2, respectively. The X-band LNT frozen glass EPR spectrum of 1 in DMF shows the presence of zero-field split rhombic symmetry character, and results in the parameters g 2.0, D = 740 G, and E = 260 G. It suggests that the intensity of&#916;Ms = &#177;2 forbidden transition is large due to the large D value. The X-band frozen glass EPR spectrum of compound 3 in DMF is found to be very similar to that reported for trans-[Cr(py)4F2]+ in DMF-H2O-MeOH glass. The large difference (~700 mV) in the reduction potential for the two octahedral complexes 1 (-1.40 V) and 3 (-0.70 V) is attributed to the difference in their metal ion oxidation states

Studies on gold(II) complexes with hard and soft donor ligands. part I. Complexes with o-aminobenzenethiol

The synthesis and characterisation of gold(II) complexes with o-aminobenzenethiol is reported. The e.s.r. results indicate that the highest occupied molecular orbital has appreciable contribution from the sulphur donors of the ligands. It is the first time that binuclear gold(II) complexes giving well resolved seven-line e.s.r. patterns originating from two 197Au nuclei have been reported

Correlation between ultrasound-based TIRADS and Bethesda system for reporting thyroid-cytopathology: 2-year experience at a tertiary care center in India

Background: In recent times, high-resolution ultrasound thyroid imaging has paved the way for significant transformation in clinical approach to thyroid nodule. There are several risk stratification systems in thyroid imaging, developed with an aim, not only to reduce the inter-observer variability but also to establish effective communication system. Thyroid image reporting and data system (TIRADS) classification system, which is similar to breast imaging reporting and data system for breast lesion, is the most useful of all. To our knowledge, there is just a handful published research articles available based on Indian population in this regard. In this article, we study the thyroid nodules using high-resolution ultrasound in Indian population and we try to correlate the TIRADS and Bethesda system for reporting thyroid cytopathology. Materials and Methods: This prospective study includes 184 patients studied over a period of 2 years (April 2015–April 2017). Patients having thyroid nodule in B-mode ultrasound and are scheduled to get a fine-needle aspiration cytology (FNAC) done. Bethesda classification of these nodules is tabulated in follow-up period simultaneously. By comparing these data, efficacy of TIRADS in differentiating benign from malignant nodules are assessed finally using accuracy, positive predictive value (PPV), cross-tabulation, and Chi-square tests. Results: Out of the 117 TIRADS 2 nodules, none turned out to be Bethesda IV or higher, which means none of these nodules turned out to be malignant.The risk of malignancy for TIRADS 2, TIRADS 3, TIRADS 4, and TIRADS 5 was 0, 2.2, 38.5, and 77.8%, respectively. The risk of malignancy percentage in our study is similar to those values obtained in other prominent studies. Conclusion: The probability of a particular nodule being malignant can be effectively inferred from the ultrasound-based TIRADS system with a certain level of confidence. Considering our results and other literature reviews, it be can be safely assumed that FNAC can be at least deferred in patients having TIRADS 2 nodules, which contribute to majority of newly detected cases. In our experience, there is a remarkable correlation exists between TIRADS ultrasound classification and Bethesda cytology, especially for benign nodules

The open molecular framework of paramagnetic lithium octabutoxy-naphthalocyanine: implications for the detection of oxygen and nitric oxide using EPR spectroscopy

The oxygen-induced broadening of the electron paramagnetic resonance (EPR) spectrum of lithium octa-n-butoxy-naphthalocyanine (LiNc-BuO) is interpreted in terms of its open molecular framework crystal structure. LiNc-BuO was prepared as a microcrystalline powder and its structure analyzed using X-ray powder diffraction techniques. The structure contains strongly coupled dimers of LiNc-BuO molecules, which favors a high degree of spin exchange, and results in a single sharp EPR line. The molecular packing leads to a structure with open channels large enough (10 × 6 Ų) for the penetration of small diatomic paramagnetic molecules such as oxygen (O₂) and nitric oxide (NO), as well as the larger triatomic species, nitrogen dioxide (NO₂). The EPR linewidth of LiNc-BuO is extremely sensitive to the concentration of paramagnetic gases in the pressure range of 0–760 mmHg. The effect of oxygen on LiNc-BuO is reversible without any signs of permanent adsorption or chemical oxidation. The time response of the effect of oxygen is extremely rapid (0.24 s). The paramagnetic gas-sensing properties of LiNc-BuO are attributed to the open molecular framework of the crystal structure. The oxygen-sensing property, combined with the previously established biostability and biocompatibility of this material, should enable precise and accurate measurements of oxygen concentration in biological systems using EPR spectroscopy

Changing landscapes in the neuroimaging of dementia

Neuroimaging in dementia has advanced several folds in the past decade. It has evolved from diagnosing secondary causes of dementia to the current use in identifying primary dementia and aid in clinically perplexing situations. There has been a leap in the imaging technology that can virtually dissect the brain with a high degree of radiopathological correlation. The neuroimaging in dementia is classified into structural, functional, and molecular imaging. Structural imaging includes voxel-based morphometry and diffusion tensor imaging. Functional imaging includes 18F-fluorodeoxy glucose positron emission tomography imaging, 99mTc hexamethylpropyleneamineoxime single photon emission computed tomography imaging, and functional magnetic resonance imaging studies. Molecular imaging includes amyloid imaging, tau imaging, and translocated protein imaging. These advancements have led to using neuroimaging as a biomarker in assessing the progression and also in deciphering prognosis of the disease. In this article, we discuss the current clinical relevance of these neurological advancements