Facile Derivatizations of Heptamethine Cyanine Dyes

Treatment of dye 3 with sodium methoxide, morpholine, or diphenylphosphine gives the respective substituted derivatives 4, 5 and 6 in high yields. The reaction of 3 with sodium acetate followed by workup affords ketone 7 which is also obtained by demethylation of a methoxy derivative 4 under non-hydrolytic conditions.     

Synthesis, structure, magnetic and spectroscopic properties of chromium(III) complex with quinoline-2-carboxylate ion

The new complex of chromium (III) with quinoline-2-carboxylate ion, [Cr(quin-2-c)₂ClMeOH]·MeOH (1), has been synthesized and its structure has been established by single crystal X-ray diffraction studies. The spectroscopic (IR, UV-Vis) and magnetic study have been undertaken. The chromium ion is coordinated by ClN₂O₃ donor set of pseudoctahedral geometry. The structure of 1 consists of hydrogen-bonded dimers which are further connected by weaker C-H?O bonds and C-H?Cl interactions into the layers. The layers are held together by the aromatic π?π contacts. The electronic experimental energies of d-d transitions are comparable with values calculated for crystal field parameters Dq = 1669, Ds = 705, and B = 684 cm⁻¹. The splitting of the d-d bands was observed by applying the filtration process. Magnetization measurements revealed the occurrence of weak antiferromagnetic interactions together with zero field splitting effects. The appearance of magnetic exchange between distant Cr(III) ions (Cr?Cr separation >6 Å) was ascribed to hydrogen bond extension of carboxylate ligands.     

Analytical assessment of some characteristic ratios for <Emphasis Type="Italic">s</Emphasis>-wave superconductors

We evaluate some thermodynamic quantities and characteristic ratios that describe low- and high-temperature s-wave superconducting systems. Based on a set of fundamental equations derived within the conformal transformation method, a simple model is proposed and studied analytically. After including a one-parameter class of fluctuations in the density of states, the mathematical structure of the s-wave superconducting gap, the free energy difference, and the specific heat difference is found and discussed in an analytic manner. Both the zero-temperature limit T = 0 and the subcritical temperature range T ? T_c are discussed using the method of successive approximations. The equation for the ratio R₁, relating the zero-temperature energy gap and the critical temperature, is formulated and solved numerically for various values of the model parameter. Other thermodynamic quantities are analyzed, including a characteristic ratio R₂, quantifying the dynamics of the specific heat jump at the critical temperature. It is shown that the obtained model results coincide with experimental data for low-T_c superconductors. The prospect of application of the presented model in studies of high-T_c superconductors and other superconducting systems of the new generation is also discussed.