Facile synthesis of novel bis-derivatives of 2,5-diamino-thiadiazole/<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-thiocarbohydrazide and their biological perspective

A series of new bis derivatives of 2,5-thiadiazole and N,N′-thiocarbohydrazide along with their transition metal complexes were synthesized by green methods (sonochemical and microwave), i.e., energy and time efficient and operationally more simple than existing conventional methods. All the synthesized compounds were fully characterized by routine analytical techniques and subjected to a preliminary biological screening. These novel characterized compounds were screened for antimicrobial activities and showed promising results. A few potent compounds were also tested for antitumor activities against MDA-MB231 (human breast carcinoma cell line) and compound 5 has emerged as a potential antitumor compound followed by compound 2, 10 and 9, with IC₅₀ values of 29.48, 32.25, 32.34 and 34.34 μg/ml, respectively. To understand the binding interactions of these compounds, in silico studies were performed using the AUTODOCK 4.2 suite and found to be supportive of the experimental results.     

Third-Order Optical Nonlinearity Studies of p-Heptaphenyl Derivatives-Doped Sol-Gel Processed Composite Glass and THF Solution by Degenerate Four-Wave Mixing and Optical Kerr Gate Measurements

We have investigated the nonlinear optical performance of new UV photostable dyes, didecyl and didecyloxy substitutedpara-polyphenyl heptamers (DDPPH and DDOPPH hereafter, respectively) using the techniques of degenerate four-wave mixing (DFWM) and optical Kerr gate (OKG). The studies were performed on the dyes dissolved in THF solution and doped in sol-gel processed composite-glass. The magnitudes and the signs of the real and the imaginary components of the complex third-order optical susceptibilities were determined by the heterodyned OKG method and compared to the values obtained from concentration dependent homodyne Kerr gate and DFWM measurements. The observed effective second hyperpolarizability γ values are dependent on the optical intensity and the pulse width of the pumping source beam. Doping of the dyes in composite-glass allows to increase the interaction length providing the prospect of using them as building blocks for photonic devices.     

Thermoanalytical investigations of niobium(V) chloride aryloxides

Niobium(V) chloride aryloxides [NbCl₃(OAr)₂] and [NbCl₂(OAr)₃] (Oar = —OC₆H₄Bu ^t -4 and —OC₆H₄OMe-4) have been prepared by reacting NbCl₅ with two and three equivalents of the respective phenol in CCl₄. The complexes have been characterized by elemental analysis, molecular weight determination, i.r., ¹H-n.m.r., u.v.–vis. and MS techniques. Thermal behaviour (t.g.–d.t.) of the complexes has also been studied and decomposition schemes proposed. The kinetic and thermodynamic parameters namely, the activation energy 'E ^*', the frequency factor 'A', entropy of activation 'S' and specific rate constant 'kr' etc. have been calculated employing the Coats–Redfern equation. The non-isothermal t.g. data has also been utilized to determine the most probable mechanism and corresponding activation energy for the decomposition of niobium(V) complexes by testing seven different theoretically possible decomposition mechanisms.     

Kinetic investigations on interaction of carbon monoxide with RuIICl2(PPh3)3 in mixed aqueous medium

Kinetics, equilibrium and thermodynamics of interaction of CO with RuCl₂(PPh₃)₃ (1) have been investigated in 1:1(v/v) water — 1,4-dioxan mixture in which 1 dissociates to RuCl₂(PPh₃)₂ (1a), by losing a coordinated PPh₃. The kinetics of complexation of (1a) with CO to form RuCl₂(CO)(PPh₃)₂ (2) indicated first order dependence in [1a] and [CO]. The thermodynamic parameters for the formation of 2 were determined.This revised version was published online in December 2005 with corrections to the Cover Date.     

Variable‐Temperature Powder X‐ray Diffraction of Aromatic Carboxylic Acid and Carboxamide Cocrystals

The effect of temperature on the cocrystallization of benzoic acid (BA), pentafluorobenzoic acid (FBA), benzamide (BAm), and pentafluorobenzamide (FBAm) is examined in the solid state. BA and FBA formed a 1:1 complex 1 at ambient temperature by grinding with a mortar and pestle. Grinding FBA and BAm together resulted in partial conversion into the 1:1 adduct 2 at 28 °C and complete transformation into the product cocrystal at 78 °C. Further heating (80–100 °C) and then cooling to room temperature gave a different powder pattern from that of 2 . BAm and FBAm hardly reacted at ambient temperature, but they afforded the 1:1 cocrystal 3 by melt cocrystallization at 110–115 °C. Both BA+FBAm ( 4 ) and BA+BAm ( 5 ) reacted to give new crystalline phases upon heating, but the structures of these products could not be determined owing to a lack of diffraction‐quality single crystals. The stronger COOH and CONH₂ hydrogen‐bonding groups of FBA and FBAm yielded the equimolar cocrystal 6 at room temperature, and heating of these solids to 90–100 °C gave a new crystalline phase. The X‐ray crystal structures of 1 , 2 , 3 , and 6 are sustained by the acid–acid/amide–amide homosynthons or acid–amide heterosynthon, with additional stabilization from phenyl–perfluorophenyl stacking in 1 and 3 . The temperature required for complete transformation into the cocrystal was monitored by in situ variable‐temperature powder X‐ray diffraction (VT‐PXRD), and formation of the cocrystal was confirmed by matching the experimental peak profile with the simulated diffraction pattern. The reactivity of H‐bonding groups and the temperature for cocrystallization are in good agreement with the donor and acceptor strengths of the COOH and CONH₂ groups. It was necessary to determine the exact temperature range for quantitative cocrystallization in each case because excessive heating caused undesirable phase transitions.