(E)‐(4‐Hydroxyphenyl)(4‐nitrophenyl)diazene, (E)‐(4‐methoxyphenyl)(4‐nitrophenyl)diazene and (E)‐[4‐(6‐bromohexyloxy)phenyl](4‐cyanophenyl)diazene

Syntheses and X‐ray structural investigations have been carried out for (E)‐(4‐hydroxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₂H₉N₃O₃, (Ia), (E)‐(4‐methoxy­phenyl)(4‐nitro­phenyl)­diazene, C₁₃H₁₁N₃O₃, (IIIa), and (E)‐[4‐(6‐bromo­hexyl­oxy)­phenyl](4‐cyano­phenyl)­diazene, C₁₉H₂₀BrN₃O, (IIIc). In all of these compounds, the mol­ecules are almost planar and the azo­benzene core has a trans geometry. Compound (Ia) contains four and compound (IIIc) contains two independent mol­ecules in the asymmetric unit, both in space group P (No. 2). In compound (Ia), the independent mol­ecules are almost identical, whereas in crystal (IIIc), the two independent mol­ecules differ significantly due to different conformations of the alkyl tails. In the crystals of (Ia) and (IIIa), the mol­ecules are arranged in almost planar sheets. In the crystal of (IIIc), the mol­ecules are packed with a marked separation of the azo­benzene cores and alkyl tails, which is common for the solid crystalline precursors of mesogens.     

Excess molar heat capacities and excess molar volumes of some mixtures of propylene carbonate with aromatic hydrocarbons

Excess molar volumes V ^E and excess molar heat capacities C _P ^E at constant pressure have been measured, at 25°C, as a function of composition for the four binary liquid mixtures propylene carbonate (4-methyl-1,3-dioxolan-2-one, C₄H₆O₃; PC) + benzene (C₆H₆;B), + toluene (C₆H₅CH₃;T), + ethylbenzene (C₆H₅C₂H₅;EB), and + p-xylene (p-C₆H₄(CH₃)₂;p-X) using a vibrating-tube densimeter and a Picker flow microcalorimeter, respectively. All the excess volumes are negative and noticeably skewed towards the hydrocarbon side: V ^E (cm³-mol^–1) at the minimum ranges from about –0.31 at x₁=0.43 for {x₁C₄H₆O₃+x₂p-C₆H₄(CH₃)₂}, to –0.45 at x₁=0.40 for {x₁C₄H₆O₃+x₂C₆H₅CH₃}. For the systems (PC+T), (PC+EB) and (PC+p-X) the C _P ^E s are all positive and even more skewed. For instance, for (PC+T) the maximum is at x _1,max =0.31 with C _P,max ^E =1.91 J-K^–1-mol^–1. Most interestingly, C _P ^E of {x₁C₄H₆O₃+x₂C₆H₆} exhibits two maxima near the ends of the composition range and a minimum at x _1,min =0.71 with C _P,min ^E =–0.23 J-K^–1-mol^–1. For this type of mixture, it is the first reported case of an M-shaped composition dependence of the excess molar heat capacity at constant pressure.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60^th birthday, Clermont-Ferrand, France, 17–18 May 1990.     

Thermal and volumetric properties of chloroform+benzene mixtures and the ideal associated solution model of complex formation

In the ideal associated solution model, activity coefficients of all species (labelled A, B, and AB here) at equilibrium are taken to be unity at all compositions and temperatures. We have applied this model to an analysis of thermodynamic properties (vapor pressures, excess enthalpies, partial molar enthalpies of solution, excess heat capacities, and excess volumes) of the chloroform+benzene system in terms of K, H, C _p , and V for the equilibrium represented by A+B=AB. It is demonstrated that there is reasonably good consistency between this simple model and all of the thermodynamic data, which shows that the model is realistic enough to be useful in assessing the properties of the not-very-stable AB complex in the chloroform+benzene system. New thermal (partial molar enthalpies of solution and excess heat capacities) and volumetric properties of the chloroform+benzene system have been measured, with results presented here.     

Thermodynamic Properties of CTAB in Aqueous Solutions of Neutral Polymers at 25°C

Interactions of polyethylene glycols (PEGs) and polypropylene glycols (PPOs) in aqueous solutions of hexadecyltrimethylammonium bromide (CTAB) were investigated through thermodynamic properties at 25°C. The densities and heat capacities of the solutions were measured with a vibrating tube densimeter and a Picker flow microcalorimeter, respectively. The variations in the apparent molar volumes and heat capacities of both solutes, calculated from the densities and heat capacities of the solutions, are unusually large in the vicinity of the CMC, reflecting the existence of very strong interactions between CTAB and PPOs. With the more hydrophilic polymers, PEGs, the apparent properties of CTAB are less affected by the presence of the polymer, indicating that PEGs interact only weakly with CTAB. This revised version was published online in August 2006 with corrections to the Cover Date.     

499 bis—The surface compartment model—voltage clamp

Solutions of the SCM equations under voltage clamp show that a transient inward sodium flux can occur at certain settings of the parameters. If there is a nonspecific increase in cation permeability upon depolarization, the positive sodium flux arises because the ion concentration changes in the electrical double layer compensate for the decrease in the electrical driving force, while parallell changes in the potassium ion concentrations lead to a decreased (but still outward) potassium flux. The sodium flux is quite sensitive to the magnitudes of the ionic permeabilities and mobilities, as well as the ion binding equilibrium and release rate constants. The values of the parameters determined here suggest magnitudes for the properties of the membrane components associated with the permeability change.     

Incorporation of a designed ruthenium nitrosyl in PolyHEMA hydrogel and light-activated delivery of NO to myoglobin

A ruthenium nitrosyl with 4-vinylpyridine (4-vpy) as one ligand, namely, [Ru(Me2bpb)(NO)(4-vpy)](BF4) (1), has been synthesized and structurally characterized. This diamagnetic {Ru-NO}6 nitrosyl is photoactive and readily releases NO upon exposure to low-intensity (5-10 mW) UV light (quantum yield at 300 nm = 0.18). Radical-induced copolymerization of 2-hydroxyethyl methacrylate (HEMA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of 1 has afforded a 1-pHEMA, a transparent hydrogel in which 1 is covalently attached to the polymer backbone. Exposure of 1-pHEMA to UV light (5-10 mW) results in rapid release of NO (detected by NO electrode) that can be delivered to biological targets such as myoglobin. The photoactivity of 1-pHEMA is strictly dependent on exposure to UV light.