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2,7-Di-tert-butyl-10b,10c-dimethyl-pyrazino[2,3-e]dihydropyrene was prepared and its photochromic properties were studied. The open form of the molecule was separated into its constituent enantiomers by chiral HPLC. The absolute structures of the enantiomers were determined by using spectra predicted with time-dependent density functional theory. Photoswitchable circular dichroism properties of 2,7-di-tert-butyl-10b,10c-dimethyl-pyrazino[2,3-e]dihydropyrene were observed, suggesting its potential for application in molecular devices.

Dihydropyrenes (DHPs) are a particularly interesting class of photochromic polyaromatic molecules due to their negative photochromism in UV-Vis spectra. Asymmetric heterocyclic-[e]-annelated DHPs were prepared by new synthetic routes and their photochromism was studied. The optical resolution of heterocyclic-[e]-annelated DHPs was performed by chiral HPLC systems and their enantiomers indicate the photochromism for UV-Vis, and CD spectra. The absolute structures of the enantiomers were determined by using spectra predicted with time-dependent density functional theory. Photoswitchable circular dichroism properties of asymmetric heterocyclic-[e]-annelated DHPs have potential as the molecular device to control the circular polarized light.

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Crystallized salt can be extracted by boiling brine in pottery over fire. This technique was implemented in many ancient civilizations throughout the world and is used even today. We identified the raw materials and technological aspects of potteries used in salt workshops from the Early Classic period (AD 250-550) of Nueva Esperanza (Pacific coast of El Salvador) by subjecting 19 samples to a petrographic analysis and wavelength-dispersive X-ray fluorescence. Previous research suggests salt pots were local, but decorated pots were transported from inland communities through markets. However, all 19 samples were made from similar main raw materials, indicating that a variety of techniques and processes were used to manufacture different types of potteries in the associated salt workshops. In sum, this study's approach should enhance understanding of ancient salt workshops, particularly regarding related pottery production systems and the nature of trade.