Photochemistry and Photophysical Properties of Novel, Unsymmetrically Substituted Metallophthalocyanines

Abstract— A series of novel, unsymmetrically substituted metallophthalocyanines was synthesized, along with their symmetrically substituted analogs, and the effects of structure and metal substitution on their photophysical and photoredox properties were investigated. The macrocy-cles were synthesized using a mixed-condensation method followed by chromatographic separation of the resulting soluble products. They possess a catechol "active site" and three tert-butyl groups for enhanced solubility. The ground- and excited-state photophysical properties of the free-base, Zn(II) and Pd(II) macrocycles were measured and compared with their symmetrically substituted (tetra[ tert -butyl]) analogs. The efficiency with which these macrocycles sensitize the formation of singlet oxygen was determined and discussed in the context of the excited-state photophysical properties. Several examples of photoinduced electron transfer reactions with one- and two-electron acceptors are demonstrated and discussed. These soluble molecules can be tuned to optimize their photochemical and redox properties by varying the central metal, axial ligands and other substituents, thereby providing a series of molecules for the investigation of photodynamic therapy and photoinduced electron transfer mechanisms.     

Design and development of a fiber-optic immunosensor utilizing near-infrared fluorophores

The design and application of a fluorescent fiber-optic immunosensor (FFOI) are reported. The FFOI is utilized for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region. The technique is developed through the combined use of fiber-optic, semiconductor laser-excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize an antibody sandwich technique. The assay involves the immobilization of the capture antibody on the sensing tip of the FFOI followed by the exposure of the immobilized sensing tip to the antigen. The antigen-coated FFOI is then introduced to a second antibody previously labeled with the NIR dye. Typical measurements are performed in about 15 min. A semiconductor laser provides the excitation (780 nm) of the immune complex. The resulting emission is detected by a silicon photodiode detector (820 nm). The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. The sensitivity of the analysis reaches 10 ng/ml and the response time is 10–15 min.     

Automerizations in benzenoid hydrocarbons. New mechanistic insights from the thermal rearrangement of benz[a]anthracene-5-13C.

Scrambling of the carbon atoms in benz[a]anthracene between positions 5 and 6 has been shown to occur at high temperatures; a mechanism involving thermal generation of a carbene is proposed.     

Rates and mechanisms of indole and 3-Methylindole polymerization in cation exchange resin beads

Batch extraction and polymerization of indole and 3-methylindole (skatole) with acidic cation exchange resins functioned as pseudo first-order reactions. Activation energies of 3.4 and 5.7 keal/mole indicated greater steric hindrance to skatole polymerization, as would be expected from 2,2′ bonding of skatole compared to 3,2′ bonding for indole. Linear polymerization occurred, although a heterocyclic ring opened at the trimer stage of poly(indole). 2-Methylindole did not polymerize. General acid-base catalysis caused unreproducible partial depolytnerization when the polymers were extracted from resin beads. Thus, compounds chromatographically separated probably were of lower degree of polymerization than were the polymers formed in the resin matrix.     

Laser-induced multiphoton dissociation ofn-butyl ether

The pulsed CO₂-laser-induced multiphoton dissociation of n-butyl vinyl ether is studied. Comprehensive measurements have been performed for 9.6.μm and 10.6 μm irradiation. The corresponding dissociation product distributions show distinct differences for the two irradiation wavelengths, the most important finding being that acetylene is only produced at 9.6 μm.     

Liquid solubilization dynamics: Oleic acid in bile salt

The solubilization dynamics of oleic acid by aqueous sodium taurodeoxycholate solutions at 37°C does not conform to previous resistance in series models involving diffusion and interfacial steps. This is especially true as the ionic strength of the aqueous solution is increased by adding NaCl or by increasing the taurodeoxycholate concentration above 2%. Experiments conducted with a liquid/liquid stirred cell show that as the ionic strength is increased, the flux of oleic acid into the aqueous solution exceeds a reasonable value for the diffusion limit, assuming that oleic acid diffuses only in mixed micelles, and that the flux becomes independent of flow at these high ionic strengths. Two alternative models for the solubilization process are proposed. One involves a rapid exchange of oleic acid between mixed micelles and oleic acid free micelles in parallel with mixed micelle diffusion; and the second involves formation of a small emulsion droplet at the interface, which contains significantly more oleic acid than a mixed micelle, and which rapidly dissolves into micellar solution as the droplet leaves the interface.     

ESR identification of a new N2− defect in X-ray irradiated NaN3

A relatively weak ESR spectrum is observed in single crystals of NaN₃ after X-ray irradiation at 77 K. This spectrum, which has an anisotropic g value and exhibits a resolved 5-line hyperfine structure with components in the ratio 1:2:3:2:1, corresponds to a single unpaired electron interacting symmetrically with two spin-one nuclei, in three inequivalent sites. The spin-Hamiltonian parameters are: g_x = 2.0054 ± 0.0005, g_y = 2.0045 ± 0.0005, g_z = 1.9688 ± 0.0005, |A_x| = 4.0 ± 0.2 G, |A_y| = 20.0 ± 0.2 G, and |A_z| = 4.9 ± 0.2 G, c-axis, and y is perpendicular to the c-axis. This spectrum, which is clearly different from that of substitutional N₂^?reported by Gelerinter and Silsbee, is attributed to interstitial N₂^?.     

Constraint relations in two-tensor gravity

A 3 + 1-dimensional decomposition is made of a two-tensor theory of gravity proposed by Salam et al. It is found that the gauge invariance roles of the two tensors are very symmetric, so that the massiveness or masslessness of the fields is ambiguous. Constraint equations are derived by elimination of gauge variables. The form of the constraints casts doubt on the sign of the total energy of the theory.     

Locally compact abelian groups with trivial multiplier group

LCA groups with trivial multiplier group are characterized. It is found that every LCA group with nontrivial multiplier group has an “irreducible” quotient with the same property, and the irreducible groups are described.