Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Excited state & Catalysis. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Three Novel End-to-End Single Azido-Bridged Ferromagnetic Copper(II) Chains: Synthesis, Crystal Structure, and Magnetic Behavior

Abstract: Three new single end-to-end azido-bridged copper(II) chains [Cu(L1)(N3)]n(ClO4)n (1), [Cu(L2)(N3)]n(ClO4)n (2), and [Cu(L3)(N3)]n(ClO4)n (3) using three different tridentate Schiff bases L1, L2, and L3, obtained from condensation of pyridine-2-carbaldehyde with N,N-dimethylethane-1,2-diamine, N,N-diethylethane-1,2-diamine, and 4-(2-aminoethyl)morpholine, respectively, have been synthesized, and their crystal structures have been determined by X-ray diffraction methods. Complex 1, C10H15CuN6ClO4, crystallizes in an orthorhombic system, space group P212121, with a = 7.434(3), b = 12.047(4), c = 17.404(6) A, and Z = 4; complex 2, C12H19CuN6ClO4, crystallizes in an orthorhombic system, space group Pna21, with a = 14.723(5), b = 13.829(5), c = 8.002(5) A, and Z = 4 and complex 3, C12H17CuN6ClO5, crystallizes in an orthorhombic system, space group Pna21, with a = 13.837(15), b = 14.804(2), c = 8.050(4) A, and Z = 4. Each structure consists of a single end-to-end azido-bridged copper(II) 1D chain where each copper(II) center possesses a square pyramidal geometry. Magnetic susceptibility data, measured from 4 to 300 K, show weak ferromagnetic interaction through the end-to-end bridging azido pathway in all the complexes. The magnetic data were fitted to a high temperature series-expansion for a one-dimensional system with S = 1/2 local spin based on the Hamiltonian H = −JΣSi·Si+1 for all the complexes, giving the parameters J = +2.15 cm−1, g = 2.23 for 1, J = +3.61 cm−1, g = 2.16 for 2, and J = +2.06 cm−1, g = 2.17 for 3. This unusual magnetic behavior through the end-to-end bridging azido pathway has been correlated to the structural parameters. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

An FCS study of unfolding and refolding of CPM-labeled human serum albumin: Role of ionic liquid

Abstract: The effect of a room temperature ionic liquid (RTIL) on the conformational dynamics of a protein, human serum albumin (HSA), is studied by fluorescence correlation spectroscopy (FCS). For this, the protein was covalently labeled by a fluorophore, 7-dimethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM). On addition of a RTIL ([pmim][Br]) to the native protein, the diffusion coefficient (Dt) decreases and the hydrodynamic radius (Rh) increases. This suggests that the RTIL ([pmim][Br]) acts as a denaturant when the protein is in the native state. However, addition of [pmim][Br] to a protein denatured by GdnHCl causes an increases in Dt and decrease in Rh. This suggests that in the presence of GdnHCl addition of RTIL helps the protein to refold. In the native state, the conformational dynamics of protein is described by three distinct time constants: ∼3.6 ± 0.7, ∼29 ± 4.5, and 133 ± 23 μs. The faster components (∼3.6 ± 0.7 and ∼29 ± 4.5 μs) are ascribed to chain dynamics of the protein, while the slowest...

Diffusion of organic dyes in ionic liquid and giant micron sized ionic liquid mixed micelle: fluorescence correlation spectroscopy.

Abstract: Diffusion of organic dyes in neat room temperature ionic liquid (RTIL) and RTIL-mixed micelle has been studied by fluorescence correlation spectroscopy (FCS). We have selected two RTILs, 3-pentyl-1-methyl imidazolium bromide ([C5C1Im][Br]) and the corresponding tetra-fluoroborate ([C5C1Im][BF4]). Diffusion coefficients (Dt) of three organic dyes—DCM (neutral), C480 (neutral), and C343 (anionic)—in these RTILs are ∼100 times slower compared to water. This indicates very high viscosity of the RTILs. In contrast to water, the Dt in RTIL exhibits a wide distribution which suggests the presence of heterogeneity (nanoscale organization). The presence of ions in the RTILs markedly affects diffusion in the RTILs. Dt's of C480 (neutral) and C343 (anionic) are very similar in water but in RTILs the ionic dye C343 diffuses 1.7 times slower than neutral C480. This is attributed to the electrostatic force exerted by the ions in the RTILs. In the giant (∼2–4 μm) [C5C1Im][Br]-triblock copolymer (P123) mixed micelle Dt o...