Synthesis,crystal structures and magnetic behaviors of two dicyanamide bridged di- and polynuclear complexes of cobalt(II) derived from 2,4,6-tris(2-pyridyl)1,3,5-triazine and imidazole

Two new dicyanamido-bridged di- and polynuclear complexes of Co(II), [Co(dca)(tptz)(H₂O)]₂·2(ClO₄) (1) and [Co(dca)₂(imz)₂]_n (2) [dca, dicyanamide; tptz, 2,4,6-tris(2-pyridyl)1,3,5-triazine; and imz, imidazole] have been synthesized and characterized structurally, as well as magnetically. The X-ray single crystal structure determination of complex 1 shows that two symmetry related octahedral Co(II) ions are separated by dca ligand and other coordination sites are satisfied by tptz and aquo ligands. Each dinuclear unit is associated with each other by intramolecular hydrogen bonding interactions, giving rise to a 1D chain structure. On the other hand complex 2 is a 1D coordination polymer having [Co(II)(imz)₂] units connected by double bridging dca ligands. These 1D chains interact through face-to-face π–π stacking interactions of the imz rings extending the dimensionality to a 2D supramolecular network. The variable temperature (300–2 K) magnetic measurements of both compounds reveal that dicyanamide exhibits a weak antiferromagnetic interaction between the metal centers.     

Photochemistry of desonide, a non-fluorinated steroidal anti-inflammatory drug

The photochemistry of anti-inflammatory drug desonide (De, 1) was studied in aerobic as well as in anaerobic condition with different irradiation wavelengths (254, 310 nm) in acetonitrile and 2-propanol. All photoproducts obtained were isolated and characterized on the basis of IR, (1)H-, (13)C-NMR spectroscopy and elemental analysis study. The products were: 11beta,21-dihydroxy-16alpha,17alpha-(1-methylethylidenedioxy)-1,5-cyclopregn-3-ene-2,20-dione 2 (254 nm), 11beta-hydroxy-16alpha,17alpha-(1-methylethylidenedioxy)androsta-1,4-diene-3-one 3 (310 nm/2-propanol), 17beta-hydroperoxy-11beta-hydroxy-16alpha,17alpha-(1-methylethylidenedioxy)androsta-1,4-diene-3-one 4 (310 nm/O(2)/2-propanol). Cyclohexadienone moiety in ring A and keto group at C(17) were found to be deeply modified by UV light therefore, loss of biological activity both during storage and in vivo can not be ruled out.     

Microwave-assisted preparations of amidrazones and amidoximes

In an operationally straightforward and efficient method, amidrazones and amidoximes are prepared in yields of 65-87% from imidoylbenzotriazoles by microwave heating for 5-20 min with the appropriate hydrazine or hydroxylamine.     

Multimodal approach for diagnosis of bacterial etiology in brain abscess

Background and purpose

Proton magnetic resonance spectroscopy (PMRS) has high sensitivity and specificity for the detection of pyogenic brain abscess and the categorization of bacteria. But the metabolite patterns failed to evaluate the etiology of disease when the culture results are sterile. The aim of the present study is to compare the multimodality techniques viz., conventional culture, MR spectroscopy and 16S rRNA PCR and sequencing for rapid diagnosis of etiology in brain abscess and evaluate the PMRS in culture sterile samples and also demonstrate the sensitivity and specificity of these techniques.

Methods

Thirty five patients underwent MRI on a 3 T MRI and in-vivo PMRS for the diagnosis and evaluation of various resonances of metabolites such as lipid (LIP), lactate (LAC), acetate (AC), amino acid (AC), succinate (SUC). Pus was collected for identification of etiologic agents by culture and molecular method.

Results

In 35 samples, metabolite patterns were as follows: LIP/LAC/AA, n = 17, LIP/LAC/AA/SUC with or without AC, n = 17 and LIP/LAC/AA/AC, n = 1. Culture showed bacterial growth in 22 samples (18 aerobic/facultative anaerobic, 9 anaerobic) whereas molecular method was detected 26 aerobic/facultative anaerobic, 13 anaerobic, 4 microaerophilic bacteria. Among the 13 sterile samples, molecular method detected 16 microorganisms along with 3 mixed infections and PMRS recognized metabolite patterns as LIP/LAC/AA, n = 5 and LIP/LAC/AA/SUC with or without AC, n = 8. The sensitivity of in-vivo PMRS in sterile samples was 100% and 75%, and specificity was 75% and 100% for aerobic and anaerobic organisms respectively.

Conclusion

Based on metabolite resonances, PMRS can detect slow growing and fastidious organisms and classify them into aerobic and anaerobic bacteria which are difficult to culture by conventional method. It can categorize microorganisms even in culture sterile samples with rational sensitivity and specificity which may allow early choice of targeted therapy.     

Nitric oxide reactivity of copper(II) complexes of bidentate amine ligands: effect of chelate ring size on the stability of a [Cu(II)-NO] intermediate

Three copper(II) complexes, 1, 2, and 3 with L(1), L(2) and L(3) [L(1) = 2-(2-aminoethyl)-pyridine; L(2) = 2-(N-ethyl-2-aminoethyl)-pyridine; L(3) = 3,3'-iminobis(N,N-dimethylpropylamine)], respectively, were synthesized and characterized. Addition of nitric oxide gas to the degassed acetonitrile solution of the complexes were found to result in the reduction of the copper(II) center to copper(I). In cases of complexes 1 and 2, the formation of the [Cu(II)-NO] intermediate prior to the reduction of Cu(II) was evidenced by UV-visible, solution FT-IR and X-band EPR spectroscopic studies. However, for complex 3, the formation of [Cu(II)-NO] has not been observed. DFT calculations on the [Cu(II)-NO] intermediate generated from complex 1 suggest a distorted square pyramidal geometry with the NO ligand coordinated to the Cu(II) center at an equatorial site in a bent geometry. In the case of complex 1, the reduction of the copper(II) center by nitric oxide afforded ligand transformation through diazotization at the primary amine site in acetonitrile solution; whereas, in an acetonitrile-water mixture, it resulted in 2-(pyridine-2-yl)ethanol. On the other hand, in cases of complexes 2 and 3, it was found to yield N-nitrosation at the secondary amine site in the ligand frameworks. The final organic products, in each case, were isolated and characterized by various spectroscopic studies.     

Copper(ii) complexes as turn on fluorescent sensors for nitric oxide

Two copper(ii) complexes, 1 and 2, of two tridentate N-donor ligands, L(1) and L(2) [L(1) = dansyl derivative of bis-[3-(dimethylamino)-propyl]amine; L(2) = dansyl derivative of dipropylenetriamine] were synthesized and characterized. The quenched fluorescence intensity of complexes 1 and 2, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide. This is attributed to the reduction of paramagnetic Cu(ii) center by nitric oxide to diamagnetic Cu(i).     

First example of a Cu(I)-(η2-O,O)nitrite complex derived from Cu(II)-nitrosyl

Copper(II) complex, 1, of the bidentate ligand, L [L = bis(2-ethyl-4-methyl-imidazol-5yl)methane] has been synthesized and structurally characterized. Addition of nitric oxide gas to a degassed acetonitrile solution of 1 yielded the corresponding copper(ii)-nitrosyl complex, 2. In acetonitrile, complex 2 on reaction with water afforded the corresponding copper(I)-nitrite complex, 3. Single crystal structure of complex 3 reveals the bidentate nitrite (η(2)-O,O) bonding. This is the first example of a structurally characterized Cu(I)-(η(2)-O,O)nitrite complex with N-donor ligand. The sequence of the formation of these complexes is just the reverse of the key steps of the postulated nitrite reduction cycle by CuNiRs.     

Photophysical characterization of 1,8 naphthalimide in micelle-diblock copolymer nano-composite: a case of morphological transformation and vesicle formation

This paper reports a morphological transition of the spherical colloidal structures of the sodium dodecyl sulfate-polyethylene-b-polyethylene glycol (SDS-PE-b-PEG) complex and anionic micelle (SDS) to "rod-shaped" colloidal structures induced by a charge transfer dye, 1,8-naphthalimide (NAPMD) (forms anions in aqueous solution by intermolecular charge transfer). The distinct steady-state results of NAPMD in the above two media point toward the formation of a new microenvironment. SDS and SDS-PE-b-PEG form unilamellar (ULV) and multilamellar vesicles (MLV), respectively, along with the rod-shaped colloidal structures as observed from transmission electron microscopy (TEM) images. This dye causes a variation in the hydrophilic/hydrophobic ratio and forms a hydrogen bond with the copolymer in the SDS-PE-b-PEG complex and subjected to electrostatic interaction with the SDS micelle in aqueous solution, which causes this morphological transformation. These vesicles show complete encapsulation of a hydrophobic dye in its interior as evident from the TEM images. ULV get ruptured at low pH, pointing toward their lower stability over MLV at low pH value. The formation of these vesicles with complete idea of its mechanism, encapsulation of bioactive molecules and its rupture at lower pH raise hope as a potential nanoscale vehicle for biologically relevant compounds and their release at low pH medium.     

On weighted directed graphs

The study of a mixed graph and its Laplacian matrix have gained quite a bit of interest among the researchers. Mixed graphs are very important for the study of graph theory as they provide a setup where one can have directed and undirected edges in the graph. In this article we present a more general structure, namely the weighted directed graphs and supply appropriate generalizations of several existing results for mixed graphs related to singularity of the corresponding Laplacian matrix. We also prove many new combinatorial results relating the Laplacian matrix and the graph structure.