Acoustical Studies of Some Schiff Bases in 1,4-Dioxane and Dimethylformamide at 318.15 K

From experimental data of density,viscosity and ultrasonic velocity,the various acoustical properties,such asspecific impedance(Z),isentropic compressibility(к_s),Rao's molar sound function(R_m),the van der Waals con-stant(b),molar compressibility(W),intermolecular free length(L_f),relaxation strength(r),internal pressure(π),free volume(V_f),solvation number(S_n)etc.,were calculated for three Schiff bases in 1,4-dioxane and dimethylfor-mamide(DMF)at 318.15 K.The results are interpreted in terms of molecular interactions occurring in the solu-tions.     

Acoustical Studies of Schiff Bases in 1,4-dioxane and Dimethylformamide at 308.15K

Variousworkershavereportedthepreparation,chemicalandphysicalpropertiesofvariousSchiffbases犤1-5犦.Schiffbasesareknowntobeimportantduetotheirapplicationsintheprepa-rationofdyes,liquidcrystalsandpowerfulcorrosionin-hibitors.Furthermore,theyareusedinthemecha…     

Kinetics of the oxidation of sulphite by tetrachloroaurate(III)

Summary The reaction between sulphite and gold(III) in hydrochloric acid medium has been studied; an initial complex is formed prior to electron transfer. The reaction rate is inversely proportional to the hydrogen ion concentration and the reaction appears to proceed through the intermediate formation of a free radical which reacts with gold(III) to give the products. Evidence for the formation of dithionate together with sulphate is presented.     

Photophysics and photocatalytic behavior of composite CdS-purine nanoparticles in the presence of certain indoles

The photophysics of purine-capped Q-CdS has been examined in the presence of certain indoles. The addition of indole does not modify electronic spectrum of purine-capped Q-CdS but it forms a fluorescing charge-transfer intermediate with illuminated CdS, which has an emissive peak at 495 nm. The intensity and the lifetime of this intermediate are enhanced initially with an increase in concentration of indole. In the presence of other indoles, the fluorescence is simply quenched in a dynamic process without forming any fluorescing intermediate. In contrast, emissive CT intermediate is not formed in the presence of indole or any of its derivatives with adenine-capped Q-CdS. In all the cases the quenching of fluorescence, monitored by steady state and time-resolved methods, follows the Stern-Volmer relationship and takes place with a bimolecular rate constant of approximately 10(10) dm(3)mol(-1)s(-1). Purine-capped Q-CdS sensitizes the reactions of the investigated indole(s)-O2 couple much more efficiently than adenine-capped Q-CdS. The differences in quenching of fluorescence and reactivity of holes between purine-capped Q-CdS and adenine-capped Q-CdS are explained by the difference in the binding of indole to the particle. In the case of purine-capped Q-CdS, specific channels for the binding of the solutes are created through the H-bond with the surface-capped purine.     

Specific heat studies in a-Se and a-Se<Subscript>90</Subscript>M<Subscript>10</Subscript> (M = In,Sb, Te) alloys

Specific heat measurements have been made in a-Se and a-Se₉₀M₁₀ (M = In, Sb, Te) alloys using differential scanning calorimetry (DSC) technique to see the effect of additives In, Sb and Te on the specific heat in a-Se. An extremely large increase in the specific heat values has been observed at the glass transition temperature. It has also been found that the values of C _p below glass transition temperature (C _pg ) and after glass transition (C _pe ) are highly composition dependent. This indicates that the additives used in the present study influences the structure of the a-Se. Specific heat and atomic mass values of the additive elements are found to be significant for the explanation of present results.     

Room-temperature ferromagnetism in nanoparticles of superconducting materials

Nanoparticles of superconducting (YBCO) () exhibit ferromagnetism at room temperature while the bulk YBCO, obtained by heating the nanoparticles at high temperature (940 ^°C), shows a linear magnetization curve. Across the superconducting transition temperature, the magnetization curve changes from that of a soft ferromagnet to a superconductor. Furthermore, our experiments reveal that not only nanoparticles of metal oxides but also metal nitrides such as NbN () and δ-MoN () exhibit room-temperature ferromagnetism.     

Signals in solid-state photochemically induced dynamic nuclear polarization recover faster than signals obtained with the longitudinal relaxation time

During the photocycle of quinone-blocked photosynthetic reaction centers (RCs), photochemically induced dynamic nuclear polarization (photo-CIDNP) is produced by polarization transfer from the initially totally electron polarized electron pair and can be observed by 13C magic-angle spinning (MAS) NMR as a strong modification of signal intensities. The same processes creating net nuclear polarization open up light-dependent channels for polarization loss. This leads to coherent and incoherent enhanced signal recovery, in addition to the recovery due to light-independent longitudinal relaxation. Coherent mixing between electron and nuclear spin states due to pseudosecular hyperfine coupling within the radical pair state provides such a coherent loss channel for nuclear polarization. Another polarization transfer mechanism called differential relaxation, which is based on the long lifetime of the triplet state of the donor, provides an efficient incoherent relaxation path. In RCs of the purple bacterium Rhodobacter sphaeroides R26, the photochemical active channels allow for accelerated signal scanning by a factor of 5. Hence, photo-CIDNP MAS NMR provides the possibility to drive the NMR technique beyond the T1 limit.     

Cucurbituril adamantanediazirine complexes and consequential carbene chemistry

Adamantanediazirines, precursors of adamantanylidenes, form 1:1 complexes (guest to host) with cucurbit[7]uril and cucurbit[8]uril and a 3:1 complex with a Pd nanocage in water. (1)H NMR spectra suggested that these complexes are stable in water on the NMR time scale. While photolysis of adamantanediazirines in water gave mainly adamantanone and adamantanol via adamantanylidene as intermediate, the 1:1 complexes of adamantanediazirine with cucurbiturils gave intramolecular C-H insertion products of adamantanylidene in >90% yield. The study establishes that significant control of carbene reactivity can be achieved when the precursor is encapsulated within a tight inert cavity. While the general characteristics of molecular containers can be understood on the basis of concepts such as "confinement" and "weak interactions", each one is unique and deserves careful scrutiny.     

Structural properties of schiff bases of 4-aminophenol in DMSO solutions on the data density, viscosity and ultrasound speed at 308.15 K

Density, ultrasonic velocity and viscosity of some Schiff bases of 4-aminophenol have been measured in dimethyl sulfoxide solutions over a wide range of concentration at 308.15 K. From these experimental data, some acoustical parameters have been evaluated, which helps in understanding the molecular interactions occurring in these solutions.