The infrared and Raman spectra of the fJ-polymorph of cycIotetramethylene tetranitramine (commonly known as "HMX" in the explosives field) and its isotopic isomers, HMX_ 15 N0 2 , HMX_ 15 N(N0 2 ), HMX_I3C(50%), and HMX-d 8' have been recorded in the spectral region between 30 and 3500 em-I. Single crystal polarized Raman measurements on fJ-HMX were also made in order to separate out modes of A g symmetry from those of B g symmetry. Sizable correlation field induced splitting of some of the (N0 2 ) modes was observed. Probable assignments have been proposed for the complex internal vibrations of fJ-HMX based mainly on the observed isotopic shifts. The spectra of HMX and HMX-d s in solutions of dimethyl sulfoxide and acetonitrile have also been recorded. The results indicate that the molecular conformation in solution is centrosymmetric and probably similar to that in the fJ-HMX crystal.

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Photodynamic antimicrobial chemotherapy (PACT) uses non-traditional mechanisms (free radicals) and is a highly advocated method with promise of inactivating drug-resistance bacteria for local infections. However, there is no related drug used in clinical practice yet. Therefore, new photosensitizers for PACT are under active development. Here, we report the synthesis of a series of photosensitizers with variable positive charges (ZnPc(TAP), n = 0, 4, 8, 12) and their inactivation against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The binding kinetics of ZnPc(TAP) to bacteria were measured by flow cytometer. Reactive oxygen species (ROS) generation mechanism of the photosensitizers was studied. The toxicity of these compounds to human blood cells was also evaluated. These compounds showed negligible toxicity against human erythocytes but potent bactericidal effects. The compound with 8 positive charges, ZnPc(TAP), turned out to have the strongest antibacterial effect among this series of compounds, giving IC value of 59 nM at a light dosage of 5 J/cm toward E. coli. For a multi-resistant E. coli strain, ZnPc(TAP) decreased the bacteria load by 1000-fold at a concentration of 1 μM. Interestingly, ZnPc(TAP), instead of ZnPc(TAP), exhibited the highest amount of binding to bacteria. Flow cytometry studies showed that all PSs have fast binding onto bacteria, reaching saturated binding within 5 min. Mechanistically, ZnPc(TAP) generated ROS primarily via Type I mechanism, while ZnPc(TAP) or ZnPc(TAP) created ROS by both type I and type II mechanisms. ZnPc(TAP) are highly potent, rapid-acting and non-toxic photosensitizers capable of inactivating bacteria.

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