The triplet-sensitized (by the solvent acetone) as well as the direct (λex = 300 - 320 nm) photochemical decarboxylation of N-phthaloylated γ-aminobutyric acid (GABA) derivatives are versatile and high-yielding routes to benzopyrrolizidines via intramolecular electron transfer initiated decarboxylation followed by radical coupling. The ß-mono- and ß,ß´-disubstituted N-phthaloyl GABA derivatives 7a-7g, respectively, were applied as substrates. Decarboxylative photocyclization yielded hydroxy benzopyrrolizidines 8a-8g in high chemical yields and with moderate diastereoselectivities from the ß-monosubstituted substrates. The analogous α-substituted GABA derivatives 11a-11c were also applied as potential substrates for memory of chirality effects. The reaction quantum yields of the photodecarboxylation reactions for the parent GABA derivative 13 and for the new substrates 7h and 11a were determined by the quantum yield determination system (QYDS) and showed a remarkable concentration dependency indicating aggregation at higher substrate concentrations. Inhibition studies on the atherogenic human serine hydrolase cholesterol esterase showed derivatives 8a and 8d to exhibit a hyperbolic mode of inhibition with moderate IC50 values of about 60-80 µM.

Quantum chemistry methods have been enacted to characterize the second-order nonlinear optical (NLO) properties of a multi-state molecular switch combining dihydroazulene and spiropyran units. They have demonstrated that the first hyperpolarizabilities constitute a novel output signal from the viewpoint of molecular logic, owing to the contrasts of NLO responses between the different forms of the dyad. On the one hand, the DFT calculations demonstrate that switching either unit has only a negligible impact on the geometrical parameters of the other one, as well as on the thermodynamics of their transformations. Similarly, as determined by time-dependent DFT calculations, the UV/vis absorption spectra are in good approximation a superposition of those from the parent units. On the other hand, this additivity trend is not consistently observed for the NLO responses. However, an interpretation of these NLO responses has been proposed by using the unit sphere representation of the first hyperpolarizability tensors to address their orientational aspects as well as by resorting to the few-state approximation and the missing state analysis to highlight the localized or charge-transfer nature of the dominant excited states.

The construction of full-color fluorescence systems has received widespread attention because of their applications in lighting materials, optoelectronic materials, and fluorescent probes. However, for the full-color luminescence system based on trichromatic materials, there are no connections between materials of different luminescent colors. Herein, A new donor-acceptor dye with red fluorescence was synthesized. The dye displays excellent optical properties of short half-peak width and strong fluorescence emission. An effective energy transfer process from the dansyl donor to the acceptor was observed with a transfer efficiency of 81%. Further, dyes with green and blue fluorescence were introduced to construct a full-spectrum fluorescent system. Through exchange reactions of Diels-Alder dynamic covalent bonds, red, green, and blue luminescence can be converted. This work provides a new idea for the design of full-color fluorescent materials.