Substituted fluorene structures have demonstrated unusual photochemical properties. Previous reports on the substituted fluorene Schiff base FR0-SB demonstrated super photobase behavior with a ΔpK b of ∼14 upon photoexcitation. In an effort to understand the basis for this unusual behavior, we have examined the electronic structure and relaxation dynamics of the structural precursor of FR0-SB, the aldehyde FR0, in protic and aprotic solvents using time-resolved fluorescence spectroscopy and quantum chemical calculations. The calculations show three excited singlet states in relatively close energetic proximity. The spectroscopic data are consistent with relaxation dynamics from these electronic states that depend on the presence and concentration of solvent hydroxyl functionality. These results underscore the central role of solvent hydrogen bonding to the FR0 aldehyde oxygen in mediating the relaxation dynamics within this molecule.

The influence of the copper­(II) ion on the formation, morphology, and organization of an arachidic acid monolayer was investigated using Langmuir–Blodgett (LB) monolayers, Π–A isotherms, and Brewster angle microscopy (BAM). Our findings indicate that a Cu2+-complexed LB film exhibits an order that depends on the subphase pH, analogous to other metal ions. Ionic Interactions of Fatty Acid Monolayers at the Air–Water InterfaceYazdanianM. Yazdanian, M. Langmuir1990610931098 Morphology of Microphase Separation in Arachidic Acid–Cadmium Arachidate Langmuir–Blodgett MultilayersKurnazM. L. Kurnaz, M. L. J. Phys. Chem.19961001111311119The metal ion facilitates the formation of solid-phase films at surface pressures as low as 5 mN/m. The films exhibit a rigid, ordered phase, evidenced by the absence of a collapse point and an increase in surface pressure rather than the typical sharp decrease in surface pressure, indicative of film failure. Amphiphile ionic charge vs pH (i.e., the extent of arachidic acid protonation) plays a role in the observed absence of collapse and the ability of the films to maintain order and cohesion at high surface pressures (ca. 65 mN/m). Additionally, film thickness data suggest that the incorporation of Cu2+ ions induces a change in orientation of the aliphatic chains of the amphiphiles and that amphiphile solubility in the subphase may play a role in the observed film behavior at low surface areas and high pH.

We report on the structure and dynamics of a Cu2+-complexed arachidic acid (AA) monolayer formed by Langmuir–Blodgett (LB) deposition. Infrared reflection–absorption spectroscopy (IRRAS) was used to characterize aliphatic chain −CH2 symmetric and asymmetric stretching modes and determine the chain tilt angle and order as a function of subphase pH. Monolayer structure is controlled by metal ion–amphiphile interactions. At low subphase pH (<5), film buckling at high surface pressure is observed, while for high subphase pH (≥5), monolayer buckling is not observed. This finding is correlated to monolayer structural mediation by metal ion–amphiphile interactions. Dynamics and mobility of a fluorophore incorporated into the monolayer were also affected by Cu2+–AA interactions, determined by fluorescence recovery after photobleaching (FRAP) measurements. These data are consistent with the formation of a rigid film due to Cu2+ coordination to AA headgroups, with the extent of headgroup protonation being determined by the pH of the subphase during monolayer deposition.

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Techniques developed for the screening of forensic samples can be useful for increasing sample throughput and decreasing backlog in forensic laboratories. One such technique, rapid gas chromatography mass spectrometry (GC-MS), allows for fast sample screening (≈1 min) and has gained interest in recent years for forensic applications. This work focuses on the development of methods for ignitable liquid analysis using rapid GC-MS. A sampling protocol and temperature program were developed for the analysis of these volatile samples. Using the optimized method for analysis, the limits of detection for compounds commonly found in ignitable liquids ranged from 0.012 mg/mL to 0.018 mg/mL. Once the analysis method was developed, neat ignitable liquids (i.e., gasoline and diesel fuel) were analyzed, and major components in each liquid were identified. The identification of gasoline and diesel fuel in the presence of substrate interferences was then assessed through the analysis of simulated fire debris samples. Three different substrates were spiked with each ignitable liquid, burned, and analyzed. Major compounds in both liquids were identified using the total ion chromatograms, relevant extracted ion profiles, and deconvolution methods.